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000
FXUS63 KLOT 301955
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
255 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
134 PM CDT

STRONGER WESTERLY WINDS OVER THE LAKE HAVE SINCE DIMINISHED THIS
AFTERNOON WITH A WEAK RIDGE OF HIGH PRESSURE OVERHEAD. ALONG WITH
THE DIMINISHING TREND THIS AFTERNOON...WINDS HAVE BECOME HIGHLY
VARIABLE ACROSS THE ENTIRE THE LAKE. EXPECT EITHER AN ONSHORE
COMPONENT OR A PERIOD OF VARIABLE WINDS OVER THE NEARSHORE THIS
AFTERNOON INTO THE EVENING...WITH A SOUTH TO EAST WIND OVER THE
OPEN WATERS. THIS WILL OCCUR UNTIL LATE IN THE EVENING...WHEN A
LOW PRESSURE SYSTEM QUICKLY MOVES SOUTHEAST TO THE SOUTHERN END OF
THE LAKE. INCREASING SPEEDS OVER THE ENTIRE LAKE BUT STILL
VARIABLE OVER THE SOUTH HALF...WILL THEN TRANSITION TO A NORTHERLY
WIND OVER ALL OF THE LAKE BY EARLY TUESDAY MORNING. SPEEDS MAY
STILL BE IN THE 15 TO 25 KT RANGE INITIALLY WITH THIS
TRANSITION...BUT WILL LIKELY OBSERVE A QUICK DIMINISHING TREND
THROUGH MIDDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301955
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
255 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
134 PM CDT

STRONGER WESTERLY WINDS OVER THE LAKE HAVE SINCE DIMINISHED THIS
AFTERNOON WITH A WEAK RIDGE OF HIGH PRESSURE OVERHEAD. ALONG WITH
THE DIMINISHING TREND THIS AFTERNOON...WINDS HAVE BECOME HIGHLY
VARIABLE ACROSS THE ENTIRE THE LAKE. EXPECT EITHER AN ONSHORE
COMPONENT OR A PERIOD OF VARIABLE WINDS OVER THE NEARSHORE THIS
AFTERNOON INTO THE EVENING...WITH A SOUTH TO EAST WIND OVER THE
OPEN WATERS. THIS WILL OCCUR UNTIL LATE IN THE EVENING...WHEN A
LOW PRESSURE SYSTEM QUICKLY MOVES SOUTHEAST TO THE SOUTHERN END OF
THE LAKE. INCREASING SPEEDS OVER THE ENTIRE LAKE BUT STILL
VARIABLE OVER THE SOUTH HALF...WILL THEN TRANSITION TO A NORTHERLY
WIND OVER ALL OF THE LAKE BY EARLY TUESDAY MORNING. SPEEDS MAY
STILL BE IN THE 15 TO 25 KT RANGE INITIALLY WITH THIS
TRANSITION...BUT WILL LIKELY OBSERVE A QUICK DIMINISHING TREND
THROUGH MIDDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO


  [top]

000
FXUS63 KILX 301946
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
246 PM CDT Mon Mar 30 2015

.SHORT TERM...(Tonight)
ISSUED AT 246 PM CDT MON MAR 30 2015

Surface high center in AR with southwest winds ahead of low pressure
center in northern plains. Only scattered high clouds over region as
the low center and assocated short wave tracks north of central IL,
dragging weak cold front into state overstate.


&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 246 PM CDT MON MAR 30 2015

Above normal temperatures can be expected to continue into mid-week
as shortwave ridging approaches Illinois. Steady 500mb height rises
reaching almost 5700m by the time the axis pushes across the state
Wednesday. Model suite at 12z consistent in developing 850 mb temps
above 10C by Wednesday Night. An increase in cloud cover once the
ridge axis passes may temper highs somewhat on Wednesday, but even
with clouds temps should be in the upper 60s to lower 70s.

Models have been trending slower with shortwave on backside of ridge
bringing precip in late Wednesday Night.  Big challenge involves the
timing of the associated cold front.  Slower solutions suggest a
frontal passage Thursday afternoon allowing good boundary layer
moisture return and enabling 500+ J/kg CAPE to develop along and
just ahead of the boundary.  Latest GEFS suggests there is still
significant spread in amount of instability with higher values
southwest of the forecast area. If slowing trend in models continue
though the strong southwest winds ahead of the front may be able to
advect higher boundary layer moisture into area. Will have to
monitor evolution closely.

As second wave is progged to move across the Mississippi Valley on
Friday. The forecast area should be mostly into the cold air by
then. ECMWF is strongest with the strength of this wave enabling
some overrunning rainfall across the entire forecast area Friday.
GFS confines significant precip near and southeast of
I-72/Danville.  will go with a blend for now which suggest at least
some chance PoPs all the way back into KGBG and KPIA. Either way, a
dreary day may keep temps below normal as strong cold advection
evident.

This second wave should push the front out of the Ohio Valley and
into the southeast U.S. bringing a dry but cool Saturday. GFS is
stronger than ECMWF with moisture return Sunday sugegsting some low
PoPs may be needed by Sunday afternoon.  This seems a bit fast and
will generally follow drier ECMWF which holds off on introducing
PoPs until Monday.


&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1228 PM CDT MON MAR 30 2015

No real change with the southwest light winds through tonight.
With passage of the next front, did time the frontal passage in
the 10-12z period across central IL in the TAFS. Winds will then
shift more to north northwest on Tuesday morning. Only sct cirrus
possible.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Goetsch
LONG TERM...Barker
AVIATION...Goetsch







000
FXUS63 KILX 301946
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
246 PM CDT Mon Mar 30 2015

.SHORT TERM...(Tonight)
ISSUED AT 246 PM CDT MON MAR 30 2015

Surface high center in AR with southwest winds ahead of low pressure
center in northern plains. Only scattered high clouds over region as
the low center and assocated short wave tracks north of central IL,
dragging weak cold front into state overstate.


&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 246 PM CDT MON MAR 30 2015

Above normal temperatures can be expected to continue into mid-week
as shortwave ridging approaches Illinois. Steady 500mb height rises
reaching almost 5700m by the time the axis pushes across the state
Wednesday. Model suite at 12z consistent in developing 850 mb temps
above 10C by Wednesday Night. An increase in cloud cover once the
ridge axis passes may temper highs somewhat on Wednesday, but even
with clouds temps should be in the upper 60s to lower 70s.

Models have been trending slower with shortwave on backside of ridge
bringing precip in late Wednesday Night.  Big challenge involves the
timing of the associated cold front.  Slower solutions suggest a
frontal passage Thursday afternoon allowing good boundary layer
moisture return and enabling 500+ J/kg CAPE to develop along and
just ahead of the boundary.  Latest GEFS suggests there is still
significant spread in amount of instability with higher values
southwest of the forecast area. If slowing trend in models continue
though the strong southwest winds ahead of the front may be able to
advect higher boundary layer moisture into area. Will have to
monitor evolution closely.

As second wave is progged to move across the Mississippi Valley on
Friday. The forecast area should be mostly into the cold air by
then. ECMWF is strongest with the strength of this wave enabling
some overrunning rainfall across the entire forecast area Friday.
GFS confines significant precip near and southeast of
I-72/Danville.  will go with a blend for now which suggest at least
some chance PoPs all the way back into KGBG and KPIA. Either way, a
dreary day may keep temps below normal as strong cold advection
evident.

This second wave should push the front out of the Ohio Valley and
into the southeast U.S. bringing a dry but cool Saturday. GFS is
stronger than ECMWF with moisture return Sunday sugegsting some low
PoPs may be needed by Sunday afternoon.  This seems a bit fast and
will generally follow drier ECMWF which holds off on introducing
PoPs until Monday.


&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1228 PM CDT MON MAR 30 2015

No real change with the southwest light winds through tonight.
With passage of the next front, did time the frontal passage in
the 10-12z period across central IL in the TAFS. Winds will then
shift more to north northwest on Tuesday morning. Only sct cirrus
possible.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Goetsch
LONG TERM...Barker
AVIATION...Goetsch






000
FXUS63 KLOT 301834
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
134 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
134 PM CDT

STRONGER WESTERLY WINDS OVER THE LAKE HAVE SINCE DIMINISHED THIS
AFTERNOON WITH A WEAK RIDGE OF HIGH PRESSURE OVERHEAD. ALONG WITH
THE DIMINISHING TREND THIS AFTERNOON...WINDS HAVE BECOME HIGHLY
VARIABLE ACROSS THE ENTIRE THE LAKE. EXPECT EITHER AN ONSHORE
COMPONENT OR A PERIOD OF VARIABLE WINDS OVER THE NEARSHORE THIS
AFTERNOON INTO THE EVENING...WITH A SOUTH TO EAST WIND OVER THE
OPEN WATERS. THIS WILL OCCUR UNTIL LATE IN THE EVENING...WHEN A
LOW PRESSURE SYSTEM QUICKLY MOVES SOUTHEAST TO THE SOUTHERN END OF
THE LAKE. INCREASING SPEEDS OVER THE ENTIRE LAKE BUT STILL
VARIABLE OVER THE SOUTH HALF...WILL THEN TRANSITION TO A NORTHERLY
WIND OVER ALL OF THE LAKE BY EARLY TUESDAY MORNING. SPEEDS MAY
STILL BE IN THE 15 TO 25 KT RANGE INITIALLY WITH THIS
TRANSITION...BUT WILL LIKELY OBSERVE A QUICK DIMINISHING TREND
THROUGH MIDDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301834
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
134 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
134 PM CDT

STRONGER WESTERLY WINDS OVER THE LAKE HAVE SINCE DIMINISHED THIS
AFTERNOON WITH A WEAK RIDGE OF HIGH PRESSURE OVERHEAD. ALONG WITH
THE DIMINISHING TREND THIS AFTERNOON...WINDS HAVE BECOME HIGHLY
VARIABLE ACROSS THE ENTIRE THE LAKE. EXPECT EITHER AN ONSHORE
COMPONENT OR A PERIOD OF VARIABLE WINDS OVER THE NEARSHORE THIS
AFTERNOON INTO THE EVENING...WITH A SOUTH TO EAST WIND OVER THE
OPEN WATERS. THIS WILL OCCUR UNTIL LATE IN THE EVENING...WHEN A
LOW PRESSURE SYSTEM QUICKLY MOVES SOUTHEAST TO THE SOUTHERN END OF
THE LAKE. INCREASING SPEEDS OVER THE ENTIRE LAKE BUT STILL
VARIABLE OVER THE SOUTH HALF...WILL THEN TRANSITION TO A NORTHERLY
WIND OVER ALL OF THE LAKE BY EARLY TUESDAY MORNING. SPEEDS MAY
STILL BE IN THE 15 TO 25 KT RANGE INITIALLY WITH THIS
TRANSITION...BUT WILL LIKELY OBSERVE A QUICK DIMINISHING TREND
THROUGH MIDDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT MON MAR 30 2015

.UPDATE...

FOR MIDDAY UPDATE...
1246 9M CDT

HAVE RAISED TEMPS A COUPLE OF DEGREES THIS AFTERNOON BASED ON OBS
TRENDS...MODEL LOW LEVEL THERMAL PROGS...AND SLOWER ARRIVAL OF CLOUD
COVER THAN PREVIOUS FORECAST. SHOULD HAVE NO TROUBLE MAKING LOW (OR
EVEN MID) 60S ACROSS THE WESTERN CWA...AND AROUND 60 EAST. SOME
CONCERN THAT WEAKENING OF PRESSURE GRADIENT LATE THIS AFTERNOON AND
DEVELOPING WARM FRONTAL TROUGH SOUTHEAST OF EASTERN DAKOTAS LOW MAY
ALLOW LAKE BREEZE WINDS ALONG THE NORTH SHORE LATE...ALONG THE LINES
OF THE LAST SEVERAL RAP RUNS. ALSO TRIMMED BACK THICKER CLOUD COVER
UNTIL LATER THIS AFTERNOON.

OTHERWISE...NO CHANGES ATTM.

RATZER

&&

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT ARND 00Z...AND THEN VEER TO NORTH NORTHWEST AND GUST TO 18
  KT IN THE EARLY MORNING HOURS.

* GUSTY NORTHWEST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 18Z...

A WEAK LOW PRESSURE SYSTEM IS OVER THE EASTERN DAKOTAS AND IT WILL
TRACK OVER FAR NORTHEAST IL TONIGHT. WEST WINDS ARE GUSTING TO 25
KT AND THEY WILL DIMINISH AND BECOME EAST THIS EVENING AS THE LOW
APPROACHES. SOME GUIDANCE MEMBERS SUGGEST THE WINDS COULD BE
NORTHEAST AND ARND 10 KT...BUT DECIDED TO KEEP WINDS EAST AT 8 KT
FOR NOW AT MDW AND ORD. THE OTHER TERMINALS WILL SEE SOUTHWEST
WINDS THIS EVENING. ANY SHOWERS ACCOMPANYING THE LOW SHOULD FALL
WELL NORTH AND EAST OF THE TERMINALS OVER WI AND LAKE MI. WINDS
THEN VEER TO SW AT ALL OF THE TERMINALS AROUND MIDNIGHT AS THE
LOW MOVES OVER THE SOUTHERN END OF THE LAKE. WIND SPEEDS PICK UP
ALOFT AS WELL LEADING TO LLWS.

SOME GUIDANCE MEMBERS THEN FEATURE WINDS BECOMING NORTH AND
POSSIBLY NORTHEAST EARLY TUESDAY MORNING BEFORE BACKING TO NW.
DECIDED TO HOLD ON TO NORTH NORTHWEST WINDS GUSTING UP TO 20 KT.
GUIDANCE ALSO CONTINUES TO FEATURE MVFR OR LOWER CIGS MOVING
THROUGH BEHIND THE LOW AND ITS COLD FRONT TUESDAY MORNING.
MOISTURE DOES NOT LOOK OVERLY SIGNIFICANT SO KEPT SCATTERED MVFR
CIGS GOING. WINDS THEN BACK TO NW AND CONTINUE TO GUST UP TO 20 KT
IN THE LATE MORNING. IF CLOUD COVER IS THICKER THAN
FORECAST...THINKING GUSTS WILL NOT BE AS STRONG.

JEE

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN WIND DIRECTION THIS EVENING. MEDIUM
  CONFIDENCE IN WIND SPEED THIS EVENING...WINDS MAY BE STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 301728
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1228 PM CDT Mon Mar 30 2015

.UPDATE...
ISSUED AT 1052 AM CDT MON MAR 30 2015

High pressure centered over AR will continue to drift to the
southeast, with light southwest winds over central IL. Some high
clouds drifting southeast over northern IL from weak short wave in
the upper plains. Only forecast concern is the approaching weak
front by Tuesday morning and the timing of frontal passage. Winds
will shift to the northwest with frontal passage. Conditions
though will remain VFR.

&&

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1228 PM CDT MON MAR 30 2015

No real change with the southwest light winds through tonight.
With passage of the next front, did time the frontal passage in
the 10-12z period across central IL in the TAFS. Winds will then
shift more to north northwest on Tuesday morning. Only sct cirrus
possible.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Goetsch
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Goetsch






000
FXUS63 KLOT 301608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1108 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* GUSTY WEST WINDS THIS AFTN DIMINISH AND BECOME EAST LESS THAN 10
  KT AFT 00Z...AND THEN BACK TO NORTHWEST AND GUST TO 18 KT IN
  THE EARLY MORNING HOURS.

* GUSTY NORTHEAST WINDS BY LATE MORNING TUESDAY.

* LLWS PSBL OVERNIGHT.

* MVFR CIGS PSBL IN THE MORNING.

JEE

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAY SHIFT ASSESS OBSERVATIONAL TRENDS
BEFORE MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST
FOR NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL
BECOME SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY
ENOUGH TO ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT
NOT AS FAR WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* MEDIUM CONFIDENCE IN WIND DIRECTION AND SPEED THIS
  EVENING...WINDS MAY BE MORE NE AND STRONGER.

* HIGH CONFIDENCE IN THE SHOWERS REMAINING EAST OF ORD AND MDW.

* MEDIUM CONFIDENCE IN LLWS TONIGHT.

* MEDIUM CONFIDENCE IN MVFR CIGS...LOW CONFIDENCE IN COVERAGE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 301556
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1056 AM CDT Mon Mar 30 2015

.UPDATE...
ISSUED AT 1052 AM CDT MON MAR 30 2015

High pressure centered over AR will continue to drift to the
southeast, with light southwest winds over central IL. Some high
clouds drifting southeast over northern IL from weak short wave in
the upper plains. Only forecast concern is the approaching weak
front by Tuesday morning and the timing of frontal passage. Winds
will shift to the northwest with frontal passage. Conditions
though will remain VFR.

&&

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 648 AM CDT MON MAR 30 2015

VFR conditions are expected for the next 24 hours at all central
Illinois terminals. WNW winds 5-10 kts will gradually shift to SW
and increase to 10-15 kts through the afternoon as a low pressure
center tracks closer to the Great Lakes Region. Expect some higher
gusts during the afternoon. Winds will begin to shift to NW
following a weak dry cold frontal passage late tonight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Goetsch
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton






000
FXUS63 KLOT 301420
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
920 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL IS INCREASING FOR A SHIFT TO NORTHEAST OR EAST WINDS
  THIS EVENING ARND 00Z.

* LLWS PSBL TONIGHT.

* MVFR CIGS PSBL TUESDAY MORNING...ALONG WITH GUSTY NNW WINDS.

JEE

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* LOW CONFIDENCE IN WIND DIRECTION THIS EVENING...GUIDANCE IS
  STARTING TO HINT AT A SHIFT TO NE OR E WINDS ARND 00Z.

* MEDIUM CONFIDENCE IN LLWS TONIGHT.

* LOW CONFIDENCE IN MVFR CIGS AND COVERAGE TUESDAY MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301420
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
920 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL IS INCREASING FOR A SHIFT TO NORTHEAST OR EAST WINDS
  THIS EVENING ARND 00Z.

* LLWS PSBL TONIGHT.

* MVFR CIGS PSBL TUESDAY MORNING...ALONG WITH GUSTY NNW WINDS.

JEE

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* LOW CONFIDENCE IN WIND DIRECTION THIS EVENING...GUIDANCE IS
  STARTING TO HINT AT A SHIFT TO NE OR E WINDS ARND 00Z.

* MEDIUM CONFIDENCE IN LLWS TONIGHT.

* LOW CONFIDENCE IN MVFR CIGS AND COVERAGE TUESDAY MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301420
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
920 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL IS INCREASING FOR A SHIFT TO NORTHEAST OR EAST WINDS
  THIS EVENING ARND 00Z.

* LLWS PSBL TONIGHT.

* MVFR CIGS PSBL TUESDAY MORNING...ALONG WITH GUSTY NNW WINDS.

JEE

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* LOW CONFIDENCE IN WIND DIRECTION THIS EVENING...GUIDANCE IS
  STARTING TO HINT AT A SHIFT TO NE OR E WINDS ARND 00Z.

* MEDIUM CONFIDENCE IN LLWS TONIGHT.

* LOW CONFIDENCE IN MVFR CIGS AND COVERAGE TUESDAY MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301420
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
920 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL IS INCREASING FOR A SHIFT TO NORTHEAST OR EAST WINDS
  THIS EVENING ARND 00Z.

* LLWS PSBL TONIGHT.

* MVFR CIGS PSBL TUESDAY MORNING...ALONG WITH GUSTY NNW WINDS.

JEE

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* LOW CONFIDENCE IN WIND DIRECTION THIS EVENING...GUIDANCE IS
  STARTING TO HINT AT A SHIFT TO NE OR E WINDS ARND 00Z.

* MEDIUM CONFIDENCE IN LLWS TONIGHT.

* LOW CONFIDENCE IN MVFR CIGS AND COVERAGE TUESDAY MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301420
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
920 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL IS INCREASING FOR A SHIFT TO NORTHEAST OR EAST WINDS
  THIS EVENING ARND 00Z.

* LLWS PSBL TONIGHT.

* MVFR CIGS PSBL TUESDAY MORNING...ALONG WITH GUSTY NNW WINDS.

JEE

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* LOW CONFIDENCE IN WIND DIRECTION THIS EVENING...GUIDANCE IS
  STARTING TO HINT AT A SHIFT TO NE OR E WINDS ARND 00Z.

* MEDIUM CONFIDENCE IN LLWS TONIGHT.

* LOW CONFIDENCE IN MVFR CIGS AND COVERAGE TUESDAY MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301420
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
920 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* POTENTIAL IS INCREASING FOR A SHIFT TO NORTHEAST OR EAST WINDS
  THIS EVENING ARND 00Z.

* LLWS PSBL TONIGHT.

* MVFR CIGS PSBL TUESDAY MORNING...ALONG WITH GUSTY NNW WINDS.

JEE

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* LOW CONFIDENCE IN WIND DIRECTION THIS EVENING...GUIDANCE IS
  STARTING TO HINT AT A SHIFT TO NE OR E WINDS ARND 00Z.

* MEDIUM CONFIDENCE IN LLWS TONIGHT.

* LOW CONFIDENCE IN MVFR CIGS AND COVERAGE TUESDAY MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 301159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
659 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* LOW POTENTIAL FOR WIND SHIFT TO NORTHEAST THIS EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT.

* POTENTIAL FOR LOWER MVFR CIGS TUESDAY MORNING.

* GUSTY NORTH-NORTHWEST WINDS TUESDAY MORNING.

RC

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND FORECAST THROUGH MID AFTERNOON...LOW-MEDIUM THIS
  EVENING/TONIGHT...MEDIUM-HIGH TUESDAY MORNING.

* MEDIUM IN LLWS TONIGHT.

* LOW IN LOWER MVFR CIG POTENTIAL TUESDAY MORNING.

RC

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
659 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* LOW POTENTIAL FOR WIND SHIFT TO NORTHEAST THIS EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT.

* POTENTIAL FOR LOWER MVFR CIGS TUESDAY MORNING.

* GUSTY NORTH-NORTHWEST WINDS TUESDAY MORNING.

RC

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND FORECAST THROUGH MID AFTERNOON...LOW-MEDIUM THIS
  EVENING/TONIGHT...MEDIUM-HIGH TUESDAY MORNING.

* MEDIUM IN LLWS TONIGHT.

* LOW IN LOWER MVFR CIG POTENTIAL TUESDAY MORNING.

RC

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 301159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
659 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* LOW POTENTIAL FOR WIND SHIFT TO NORTHEAST THIS EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT.

* POTENTIAL FOR LOWER MVFR CIGS TUESDAY MORNING.

* GUSTY NORTH-NORTHWEST WINDS TUESDAY MORNING.

RC

//DISCUSSION...UPDATED 12Z...

AVIATION CONDITIONS WILL BE QUIET MOST OF THE DAY WITH WEST WINDS
BECOMING MODERATELY GUSTY AND INCREASING VFR CLOUDS BY MID DAY.
FOCUS WILL BE ON TRACK OF CLIPPER LOW PRESSURE SYSTEM CURRENTLY
OVER THE NORTHERN HIGH PLAINS THIS MORNING. IT IS EXPECTED TO
TRACK NORTH OF THE TERMINALS THIS EVENING...BUT SOME OF THE LATEST
HIGHER RESOLUTION GUIDANCE IS INDICATING A FARTHER SOUTH TRACK. IF
THIS OCCURS...A WIND SHIFT TO NORTHEAST WOULD BE POSSIBLE THIS
EVENING AT THE EASTERN TERMINALS...AS WELL AS A BETTER CHANCE FOR
RAIN SHOWERS. WILL LET DAYSHIFT ASSESS OBSERVATIONAL TRENDS BEFORE
MAKING ANY BIG CHANGES...AND HAVE STUCK WITH A DRY FORECAST FOR
NOW. IF TRACK OF LOW IS AS CURRENTLY EXPECTED...WINDS WILL BECOME
SOUTH-SOUTHWEST BY EARLY EVENING AND DIMINISH...LIKELY ENOUGH TO
ENABLE A WEAK LAKE BREEZE TO PUSH ONTO THE IL SHORE BUT NOT AS FAR
WEST AS ORD/MDW.

IN ADDITION...BASED ON CURRENT FORECAST TRACK OF THE LOW
PRESSURE JUST TO THE NORTHEAST OF THE TERMINALS...SOUTHWEST WINDS
WILL STRENGTHEN TONIGHT...WITH A BRIEF BUT SUBSTANTIAL INCREASE
IN WINDS ALOFT. THUS HAVE MAINTAINED A PERIOD OF LLWS IN THE TAFS.
BEHIND THE LOW...WINDS WILL SHIFT TO NORTH-NORTHWEST BY TUESDAY
MORNING AND EVENTUALLY NORTHEAST TUESDAY AFTERNOON FOR THE EASTERN
TERMINALS. WILL NEED TO WATCH FOR A PERIOD OF LOWER MVFR
CIGS TUESDAY MORNING...WHICH HAS BEEN HINTED AT IN THE ORD 30
HOUR TAF.

RC


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND FORECAST THROUGH MID AFTERNOON...LOW-MEDIUM THIS
  EVENING/TONIGHT...MEDIUM-HIGH TUESDAY MORNING.

* MEDIUM IN LLWS TONIGHT.

* LOW IN LOWER MVFR CIG POTENTIAL TUESDAY MORNING.

RC

//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...

TUESDAY NIGHT...VFR WITH NORTHEAST WINDS.

WEDNESDAY...VFR. MODERATELY GUSTY SOUTH WINDS DEVELOPING.

THURSDAY...SHRA LIKELY...CHANCE TSRA. PERIODIC IFR POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY AND SUNDAY...LIKELY VFR.

RC

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 301148
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
648 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 648 AM CDT MON MAR 30 2015

VFR conditions are expected for the next 24 hours at all central
Illinois terminals. WNW winds 5-10 kts will gradually shift to SW
and increase to 10-15 kts through the afternoon as a low pressure
center tracks closer to the Great Lakes Region. Expect some higher
gusts during the afternoon. Winds will begin to shift to NW
following a weak dry cold frontal passage late tonight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton






000
FXUS63 KILX 301148
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
648 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 648 AM CDT MON MAR 30 2015

VFR conditions are expected for the next 24 hours at all central
Illinois terminals. WNW winds 5-10 kts will gradually shift to SW
and increase to 10-15 kts through the afternoon as a low pressure
center tracks closer to the Great Lakes Region. Expect some higher
gusts during the afternoon. Winds will begin to shift to NW
following a weak dry cold frontal passage late tonight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton







000
FXUS63 KILX 301148
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
648 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 648 AM CDT MON MAR 30 2015

VFR conditions are expected for the next 24 hours at all central
Illinois terminals. WNW winds 5-10 kts will gradually shift to SW
and increase to 10-15 kts through the afternoon as a low pressure
center tracks closer to the Great Lakes Region. Expect some higher
gusts during the afternoon. Winds will begin to shift to NW
following a weak dry cold frontal passage late tonight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton







000
FXUS63 KILX 301148
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
648 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 648 AM CDT MON MAR 30 2015

VFR conditions are expected for the next 24 hours at all central
Illinois terminals. WNW winds 5-10 kts will gradually shift to SW
and increase to 10-15 kts through the afternoon as a low pressure
center tracks closer to the Great Lakes Region. Expect some higher
gusts during the afternoon. Winds will begin to shift to NW
following a weak dry cold frontal passage late tonight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton






000
FXUS63 KLOT 300929
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
429 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 300929
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
429 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNESDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION
AHEAD OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH
FORECAST LOWS PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE
LEANED TOWARD THE CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO
THE SYSTEM COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A
MAJORITY OF THE SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER
AND THUNDERSTORM CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND
QUITE POSSIBLY EVEN MORE SO INTO THURSDAY. WITH THE PARENT LOW
RACING EAST...THE COLD FRONT IS FORECAST TO SLOW WITH A PARALLEL
UPPER JET INCREASING OVERHEAD...BRINGING ANOTHER WAVE ALONG THE
BOUNDARY DURING FRIDAY OR SO. OVER THE PAST TWO DAYS...GUIDANCE
HAS NOT SURPRISINGLY VARIED WITH HOW THIS ALL WILL MESH TOGETHER
IN OUR REGION...AND LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS
AND THUNDERSTORMS ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR
LATE WEDNESDAY NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF
UNCERTAINTY ON FRIDAY. THERE ALSO IS HIGHER THAN NORMAL
UNCERTAINTY FOR TEMPERATURES THURSDAY AND FRIDAY...WITH THE LATTER
LIKELY BEING COOLER...IF NOT CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
429 AM CDT

MAIN MARINE CONCERN IN THE NEAR TERM IS WITH A POSSIBLE PERIOD OF
STRONGER SOUTHWEST WINDS IN THE NEARSHORE TONIGHT. A CLIPPER
SYSTEM WILL DIVE SOUTHEAST AND CROSS SOUTHERN LAKE MICHIGAN
LATE THIS EVENING INTO THE OVERNIGHT. THE PATH THE LOW TAKES WILL
DICTATE WIND SPEEDS...WITH CURRENT FORECAST FAVORING A SLIGHTLY
FARTHER NORTH PATH SUPPORTIVE OF SOUTHWEST TO WEST WINDS OF 20 TO
25 KT. HOWEVER...A FARTHER SOUTH PATH WOULD RESULT IN LIGHTER
WESTERLY WINDS. DUE TO THIS LINGERING UNCERTAINTY...HAVE HELD OFF
ON ISSUING A SMALL CRAFT ADVISORY. NORTH OF THE LOW...NORTHEAST
WINDS WILL INCREASE TO UP TO 25 KT AND SOME POTENTIAL FOR A BRIEF
PERIOD OF GUSTS UP TO 30 KT LATE TONIGHT. NORTHERLY WINDS WILL
PUSH DOWN THE LAKE IN THE WAKE OF THE CLIPPER LOW ON TUESDAY.
HOWEVER...SPEEDS WILL DIMINISH FAIRLY QUICKLY FROM EARLY 15 TO 20
KT/POSSIBLY 25 KT SPEEDS TO START THE DAY...SO WAVES WILL NOT HAVE
MUCH TIME TO BUILD ON SOUTHERN TIP OF THE LAKE.

LIGHT WINDS TUESDAY NIGHT DUE TO HIGH PRESSURE WILL SHIFT
SOUTHERLY AS THE HIGH SLIDES EAST ON WEDNESDAY. STRONGER WINDS
WILL RETURN TO THE LAKE WEDNESDAY NIGHT AS A LARGE LOW PRESSURE
SYSTEM ORGANIZES IN THE UPPER PLAINS NEAR THE INTERNATIONAL
BORDER. THIS WILL DRIVE STRONG SOUTHERLY WINDS WITH A STOUT
INVERSION FORECAST. SO THE CHALLENGE RETURNS AS TO HOW MUCH
MOMENTUM WILL BE TRANSFERED DOWN TO THE SURFACE. FOR RIGHT NOW IN
THE NORTH HAVE MENTIONED OCCASIONAL GALES WHILE IN THE SOUTH TO 30
KT. THE LOW WILL STEER A COLD FRONT ACROSS THE LAKE ON
THURSDAY...RIGHT NOW FAVORED EARLY IN THE DAY...WHICH WILL TURN
WINDS WESTERLY AND DIMINISH THEM IN SPEED.

RC/MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 300840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT MON MAR 30 2015

.SHORT TERM...
340 AM CDT

TODAY THROUGH TUESDAY...

MAIN WEATHER FEATURE OF NOTE TODAY IS AN ALBERTA CLIPPER
CURRENTLY OVER THE NORTHERN CANADIAN PRAIRIES THAT WILL DIVE
SOUTHEAST TOWARD SOUTHERN LAKE MICHIGAN THIS EVENING IN NORTHWEST
FLOW ALOFT. MILD DOWNSLOPE FLOW FROM THE HIGH PLAINS WILL RESULT
IN TEMPERATURES WARMING TO THE UPPER 50S TO LOWER 60S TODAY...WITH
ASSOCIATED WARM ADVECTION RESULTING IN MIDLEVEL CLOUDS INCREASING
BY MID DAY. MODERATE WESTERLY WINDS WILL SHIFT SOUTHWEST AND
DIMINISH...ESPECIALLY CLOSER TO THE LAKE BY LATE DAY AS THE
CLIPPER APPROACHES. WEAKENING WIND FIELD IS EXPECTED TO ENABLE A
LAKE BREEZE TO SLIP JUST INLAND ALONG THE IL SHORE AND BRING LATE
DAY COOLING. HAVE CONCERN WITH THE TRACK OF THE CLIPPER...WITH THE
ECMWF DECIDEDLY FARTHER SOUTH...THOUGH NORTH OF PREVIOUS RUN.
OVERALL...EVEN FARTHER SOUTH TRACK WILL BRING ONLY A GLANCING BLOW
OF RAIN SHOWERS TO NORTHEAST THIRD OR QUARTER OF CWA....SO HAVENT
MADE BIG CHANGES TO SLIGHT/LOW CHC POPS DURING EVENING.

TEMPERATURES WILL REMAIN MILD IN LOWER-MID 40S TONIGHT THANKS TO
GUSTY WEST-SOUTHWEST WINDS AS CLIPPER PASSES TO NORTHEAST...BUT
THEN THERE WILL BE A FAIRLY STRONG COLD FRONT PASSAGE IN THE WAKE
OF IT. 850 MB TEMPS WILL COOL TO ABOUT -2 CELSIUS NEAR THE LAKE BY
MID DAY TUESDAY...ALONG WITH FAIRLY STRONG NORTHERLY FLOW.
THEREFORE...HAVE SHAVED SEVERAL DEGREES OFF OF PREVIOUS FORECAST
HIGHS...WITH ONLY MID TO UPPER 40S NEAR THE LAKE AND MID 50S TO
LOWER 60S WELL INLAND. WINDS WILL SHIFT NORTHEAST DUE TO LAKE
BREEZE INFLUENCE TUESDAY AFTERNOON AND LAKE COOLING WILL PUSH
INLAND DURING THE MID TO LATE AFTERNOON. EXPECTING A CHILLY MID TO
UPPER 30S ALONG THE SHORE BY SUNSET....SO A BIG CHANGE FROM THE
MILD TEMPERATURES TODAY.

RC

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300837
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
337 AM CDT MON MAR 30 2015

.SHORT TERM...
334 AM CDT

THROUGH TUESDAY...

TO BE ISSUED SHORTLY.

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 300837
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
337 AM CDT MON MAR 30 2015

.SHORT TERM...
334 AM CDT

THROUGH TUESDAY...

TO BE ISSUED SHORTLY.

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 300837
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
337 AM CDT MON MAR 30 2015

.SHORT TERM...
334 AM CDT

THROUGH TUESDAY...

TO BE ISSUED SHORTLY.

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 300837
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
337 AM CDT MON MAR 30 2015

.SHORT TERM...
334 AM CDT

THROUGH TUESDAY...

TO BE ISSUED SHORTLY.

&&

.LONG TERM...
332 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

THE UPPER PATTERN WILL REMAIN PROGRESSIVE DURING THE MID TO LATTER
HALF OF THE WEEK INTO NEXT WEEKEND. HEIGHT RISES AND A LOWER TROP
THERMAL RIDGE WILL MOVE IN TOGETHER ON WEDNESDAY. THE STARTING POINT
OF THE DAY WILL BE NEAR TO JUST SLIGHTLY BELOW NORMAL...SO FEEL
COMFORTABLE GOING WITH WEDNESDAY HIGHS NEAR WHERE THEY
CLIMATOLOGICALLY SHOULD BE FOR 850MB TEMPERATURES OF 7-10C THIS
TIME OF YEAR. THIS SUPPORTS 60S IN MOST PLACES WITH THE IMMEDIATE
ILLINOIS LAKE SHORE POTENTIALLY HAVING SLIGHT COOLING GIVEN A
FORECAST WIND DIRECTION OF 170 DEGREES OR SO.

AN UPPER TROUGH MOVING ACROSS SOUTHERN CANADA WEDNSEDAY NIGHT
THROUGH THURSDAY IS FORECAST TO TAKE ADVANTAGE OF JET COUPLING TO
STRENGTHEN AS IT MOVES EAST...WITH A SURFACE REFLECTION FORECAST
AROUND 992 MB USING A MEAN GLOBAL SOLUTION. THE WARM ADVECTION AHEAD
OF THIS WILL LEAD TO A MILD NIGHT WEDNESDAY NIGHT WITH FORECAST LOWS
PRESENTLY IN THE LOWER TO MID 50S /YES LOWS/. HAVE LEANED TOWARD THE
CONSISTENTLY SLOWER EC SOLUTION WITH REGARD TO THE SYSTEM
COLD FRONT...WHICH IS SUPPORTED BY THE NAM AND A MAJORITY OF THE
SREF MEMBERS. THIS WOULD KEEP MOST OF THE SHOWER AND THUNDERSTORM
CHANCES CONFINED TO LATE WEDNESDAY NIGHT AND QUITE POSSIBLY EVEN
MORE SO INTO THURSDAY. WITH THE PARENT LOW RACING EAST...THE COLD
FRONT IS FORECAST TO SLOW WITH A PARALLEL UPPER JET INCREASING
OVERHEAD...BRINGING ANOTHER WAVE ALONG THE BOUNDARY DURING FRIDAY
OR SO. OVER THE PAST TWO DAYS...GUIDANCE HAS NOT SURPRISINGLY
VARIED WITH HOW THIS ALL WILL MESH TOGETHER IN OUR REGION...AND
LIKELY CHANGES WILL OCCUR. CHANCES FOR SHOWERS AND THUNDERSTORMS
ARE PRESENTLY MOST WARRANTED IN THE FORECAST FOR LATE WEDNESDAY
NIGHT AND THURSDAY...WITH A HIGH AMOUNT OF UNCERTAINTY ON FRIDAY.
THERE ALSO IS HIGHER THAN NORMAL UNCERTAINTY FOR TEMPERATURES
THURSDAY AND FRIDAY...WITH THE LATTER LIKELY BEING COOLER...IF NOT
CONSIDERABLY COOLER THAN THURSDAY.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 300802
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
302 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.


&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1143 PM CDT SUN MAR 29 2015

VFR aviation weather conditions expected across the central
Illinois terminals through the 06Z TAF valid time. A cold front
has cleared the area within the past few hours, with high pressure
expected to be dominant for the duration of the forecast. Cloud
cover is expected to be minimal overall, with winds becoming gusty
out of the the southwest for much of the daytime hours Monday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Bak






000
FXUS63 KILX 300802
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
302 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.


&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1143 PM CDT SUN MAR 29 2015

VFR aviation weather conditions expected across the central
Illinois terminals through the 06Z TAF valid time. A cold front
has cleared the area within the past few hours, with high pressure
expected to be dominant for the duration of the forecast. Cloud
cover is expected to be minimal overall, with winds becoming gusty
out of the the southwest for much of the daytime hours Monday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Bak







000
FXUS63 KILX 300802
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
302 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.


&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1143 PM CDT SUN MAR 29 2015

VFR aviation weather conditions expected across the central
Illinois terminals through the 06Z TAF valid time. A cold front
has cleared the area within the past few hours, with high pressure
expected to be dominant for the duration of the forecast. Cloud
cover is expected to be minimal overall, with winds becoming gusty
out of the the southwest for much of the daytime hours Monday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Bak






000
FXUS63 KILX 300802
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
302 AM CDT Mon Mar 30 2015

.SHORT TERM...(Today)
ISSUED AT 301 AM CDT MON MAR 30 2015

Mild temperatures and dry weather are expected today as central
Illinois remains in weak subsidence aloft behind yesterday`s storm
system. With a surface high pressure center passing by to the south
and a surface low approaching northeast IL from the northern Plains,
a strengthening pressure gradient will bring a 10-15 mph SW breeze
helping to advect warmer air into the region from the central
Plains. Highs will therefore reach the low to mid 60s, with the
warmer temperatures toward the west side of the state. Periods of
high clouds can be expected, but they should be thin enough for a
mostly sunny day.


&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 301 AM CDT MON MAR 30 2015

In the near term...temperatures going through a warming trend
through midweek.  A quick wave/clipper like system diving into the
Midwest should keep the bulk of its impacts just north of ILX
tonight...as dry weather and weak high pressure ridging dominates
through Wednesday.  System in development for second half of the
week starting to show in the med range models and so far, the NAM is
aligning with slower ECMWF...with the GEM not too far behind.  With
the slower solution, the precip should remain to the west until
Thursday morning, but so far, the SuperBlend is holding onto pops
for Wed night because of the quicker GFS. Have altered them somewhat
in the east to start a slower trend. Once this front moves through
with the rain on Thursday and Thursday evening, the front does not
get very far and ends up hanging up in mostly weak parallel flow
just north of the Ohio River Valley.  Another wave moves out of the
Plains along the boundary, enhancing precip along the boundary for
Friday as well as acting as a kicker to get the system out of the
region altogether by the weekend.  High pressure builds back in for
next weekend with the highs in the mid to upper 50s/lower 60s.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1143 PM CDT SUN MAR 29 2015

VFR aviation weather conditions expected across the central
Illinois terminals through the 06Z TAF valid time. A cold front
has cleared the area within the past few hours, with high pressure
expected to be dominant for the duration of the forecast. Cloud
cover is expected to be minimal overall, with winds becoming gusty
out of the the southwest for much of the daytime hours Monday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Bak







000
FXUS63 KLOT 300547
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1247 AM CDT MON MAR 30 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300547
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1247 AM CDT MON MAR 30 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 300547
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1247 AM CDT MON MAR 30 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LOW LEVEL WIND SHEAR AROUND MIDNIGHT TONIGHT.

RC

//DISCUSSION...UPDATED 06Z...

CONDITIONS SHOULD GENERALLY REMAIN VFR THROUGH THE PERIOD. SCT TO
BKN VFR CLOUDS ARE STREAMING SOUTHEAST FROM SOUTHERN WI INTO
NORTHERN IL AND NW IN BUT SHOULD SHIFT EAST THIS
MORNING...FOLLOWED BY INCREASING VFR CLOUDS BY MID DAY. CURRENTLY
LIGHT WEST WINDS WILL INCREASE BY MID DAY AND GUST INTO THE MID-
HIGH TEENS INTO THE MID AFTERNOON. MAIN WEATHER FEATURE OF NOTE
IS A CLIPPER TYPE SYSTEM THAT WILL DIVE SOUTHEAST TODAY AND ACROSS
SOUTHERN LAKE MICHIGAN THIS EVENING. WINDS WILL SHIFT SOUTHWEST
LATE IN THE DAY IN ADVANCE OF THE CLIPPER AND MAY DIMINISH ENOUGH
TO ENABLE A LAKE BREEZE TO SLIP INLAND ALONG THE IMMEDIATE IL
SHORE...LIKELY WELL EAST OF ORD AND MDW. MOST GUIDANCE KEEPS
PRECIP WITH THE CLIPPER NORTH OF THE TERMINALS...SO HAVE STAYED
WITH A DRY FORECAST. SOUTHWEST WINDS WILL INCREASE TONIGHT AS THE
SYSTEM TRACKS JUST TO THE NORTHEAST...WITH A BRIEF BUT SUBSTANTIAL
INCREASE IN WINDS ALOFT. THUS HAVE INCLUDED A PERIOD OF LLWS IN
THE TAFS.

RC


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM-HIGH IN LLWS TONIGHT.

* HIGH IN REMAINING ELEMENTS.

RC

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 300446
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1146 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1143 PM CDT SUN MAR 29 2015

VFR aviation weather conditions expected across the central
Illinois terminals through the 06Z TAF valid time. A cold front
has cleared the area within the past few hours, with high pressure
expected to be dominant for the duration of the forecast. Cloud
cover is expected to be minimal overall, with winds becoming gusty
out of the the southwest for much of the daytime hours Monday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KILX 300446
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1146 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1143 PM CDT SUN MAR 29 2015

VFR aviation weather conditions expected across the central
Illinois terminals through the 06Z TAF valid time. A cold front
has cleared the area within the past few hours, with high pressure
expected to be dominant for the duration of the forecast. Cloud
cover is expected to be minimal overall, with winds becoming gusty
out of the the southwest for much of the daytime hours Monday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak






000
FXUS63 KLOT 300312
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1012 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NONE

IZZI

//DISCUSSION...UPDATED 00Z...

COLD FRONT WILL CONTINUE TO MOVE ACROSS THE TERMINALS EARLY THIS
EVENING WITH A BRIEF PERIOD OF LIGHT RAIN/SPRINKLES ALONG THE
FRONT. SMALL AREA OF MVFR CIGS WILL PROBABLY AFFECT THE TERMINALS
ALONG AND IMMEDIATELY IN THE WAKE OF THE FRONT BEFORE SKIES GO SKC
LATER THIS EVENING. IN ADDITION...THE PUSH IMMEDIATELY BEHIND
FRONT COULD HAVE AN HOUR OR TWO OR STRONG NORTHWEST WINDS
POTENTIALLY GUSTING UP TO AROUND 30KT BEFORE WINDS BACK A BIT MORE
WESTERLY AND EASE MID-LATE EVENING. A VFR CEILING COULD MOVE BACK
IN WITH MID LEVEL CLOUDINESS AND POTENTAILLY SOME VIRGA OR EVEN
A SPRINKLE MONDAY AFTERNOON WITH CONTINUED LIGHT WESTERLY WINDS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 300312
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1012 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NONE

IZZI

//DISCUSSION...UPDATED 00Z...

COLD FRONT WILL CONTINUE TO MOVE ACROSS THE TERMINALS EARLY THIS
EVENING WITH A BRIEF PERIOD OF LIGHT RAIN/SPRINKLES ALONG THE
FRONT. SMALL AREA OF MVFR CIGS WILL PROBABLY AFFECT THE TERMINALS
ALONG AND IMMEDIATELY IN THE WAKE OF THE FRONT BEFORE SKIES GO SKC
LATER THIS EVENING. IN ADDITION...THE PUSH IMMEDIATELY BEHIND
FRONT COULD HAVE AN HOUR OR TWO OR STRONG NORTHWEST WINDS
POTENTIALLY GUSTING UP TO AROUND 30KT BEFORE WINDS BACK A BIT MORE
WESTERLY AND EASE MID-LATE EVENING. A VFR CEILING COULD MOVE BACK
IN WITH MID LEVEL CLOUDINESS AND POTENTAILLY SOME VIRGA OR EVEN
A SPRINKLE MONDAY AFTERNOON WITH CONTINUED LIGHT WESTERLY WINDS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 300312
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1012 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NONE

IZZI

//DISCUSSION...UPDATED 00Z...

COLD FRONT WILL CONTINUE TO MOVE ACROSS THE TERMINALS EARLY THIS
EVENING WITH A BRIEF PERIOD OF LIGHT RAIN/SPRINKLES ALONG THE
FRONT. SMALL AREA OF MVFR CIGS WILL PROBABLY AFFECT THE TERMINALS
ALONG AND IMMEDIATELY IN THE WAKE OF THE FRONT BEFORE SKIES GO SKC
LATER THIS EVENING. IN ADDITION...THE PUSH IMMEDIATELY BEHIND
FRONT COULD HAVE AN HOUR OR TWO OR STRONG NORTHWEST WINDS
POTENTIALLY GUSTING UP TO AROUND 30KT BEFORE WINDS BACK A BIT MORE
WESTERLY AND EASE MID-LATE EVENING. A VFR CEILING COULD MOVE BACK
IN WITH MID LEVEL CLOUDINESS AND POTENTAILLY SOME VIRGA OR EVEN
A SPRINKLE MONDAY AFTERNOON WITH CONTINUED LIGHT WESTERLY WINDS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM MONDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 300149
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
849 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak








000
FXUS63 KILX 300149
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
849 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KILX 300149
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
849 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KILX 300149
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
849 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KILX 300149
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
849 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KILX 300149
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
849 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 849 PM CDT SUN MAR 29 2015

Periods of showers that impacted central and southeast Illinois
earlier today were well ahead of the surface cold front that is
currently crossing the area. The cold front is roughly along the
I-55 corridor at this time. The front itself is coming through
dry, but is associated with a band of clouds. Expect the front to
quickly exit to the east over the next few hours, with skies
rapidly clearing in its wake (where it has not already done so).
Then, building high pressure will help keep quiet conditions in
place for the balance of the night.

Going forecast had this quiet weather regime well handled. Only
need to update for the latest hourly trends and to remove
precipitation wording in the east from the text products.

&&

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KILX 292355
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
655 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak






000
FXUS63 KILX 292355
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
655 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KILX 292355
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
655 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak






000
FXUS63 KILX 292355
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
655 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forecast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 655 PM CDT SUN MAR 29 2015

A cold front is beginning to track across central Illinois from
the northwest, and should be south/east of the terminal area
within the next few hours. The front is accompanied by a band of
lower end VFR cigs, with skies expected to rapidly clear behind
the front. VFR conditions are expected to prevail through the
entire 00Z TAF valid time, as high pressure builds across the area
behind the cold front. Pre-frontal winds, potentially gusty from
the southwest, will trend northwest behind the front and diminish.
Winds will back southwest again early Monday, gusting to around 20
kts by midday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak







000
FXUS63 KLOT 292351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
651 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* BRIEF PERIOD OF -RA/MVFR CIGS/30KT NW WINDS WITH FRONTAL PASSAGE
  THIS EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

COLD FRONT WILL CONTINUE TO MOVE ACROSS THE TERMINALS EARLY THIS
EVENING WITH A BRIEF PERIOD OF LIGHT RAIN/SPRINKLES ALONG THE
FRONT. SMALL AREA OF MVFR CIGS WILL PROBABLY AFFECT THE TERMINALS
ALONG AND IMMEDIATELY IN THE WAKE OF THE FRONT BEFORE SKIES GO SKC
LATER THIS EVENING. IN ADDITION...THE PUSH IMMEDIATELY BEHIND
FRONT COULD HAVE AN HOUR OR TWO OR STRONG NORTHWEST WINDS
POTENTIALLY GUSTING UP TO AROUND 30KT BEFORE WINDS BACK A BIT MORE
WESTERLY AND EASE MID-LATE EVENING. A VFR CEILING COULD MOVE BACK
IN WITH MID LEVEL CLOUDINESS AND POTENTAILLY SOME VIRGA OR EVEN
A SPRINKLE MONDAY AFTERNOON WITH CONTINUED LIGHT WESTERLY WINDS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN CIGS/PRECIP/WINDS THROUGH MID EVENING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
651 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* BRIEF PERIOD OF -RA/MVFR CIGS/30KT NW WINDS WITH FRONTAL PASSAGE
  THIS EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

COLD FRONT WILL CONTINUE TO MOVE ACROSS THE TERMINALS EARLY THIS
EVENING WITH A BRIEF PERIOD OF LIGHT RAIN/SPRINKLES ALONG THE
FRONT. SMALL AREA OF MVFR CIGS WILL PROBABLY AFFECT THE TERMINALS
ALONG AND IMMEDIATELY IN THE WAKE OF THE FRONT BEFORE SKIES GO SKC
LATER THIS EVENING. IN ADDITION...THE PUSH IMMEDIATELY BEHIND
FRONT COULD HAVE AN HOUR OR TWO OR STRONG NORTHWEST WINDS
POTENTIALLY GUSTING UP TO AROUND 30KT BEFORE WINDS BACK A BIT MORE
WESTERLY AND EASE MID-LATE EVENING. A VFR CEILING COULD MOVE BACK
IN WITH MID LEVEL CLOUDINESS AND POTENTAILLY SOME VIRGA OR EVEN
A SPRINKLE MONDAY AFTERNOON WITH CONTINUED LIGHT WESTERLY WINDS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN CIGS/PRECIP/WINDS THROUGH MID EVENING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 292351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
651 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* BRIEF PERIOD OF -RA/MVFR CIGS/30KT NW WINDS WITH FRONTAL PASSAGE
  THIS EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

COLD FRONT WILL CONTINUE TO MOVE ACROSS THE TERMINALS EARLY THIS
EVENING WITH A BRIEF PERIOD OF LIGHT RAIN/SPRINKLES ALONG THE
FRONT. SMALL AREA OF MVFR CIGS WILL PROBABLY AFFECT THE TERMINALS
ALONG AND IMMEDIATELY IN THE WAKE OF THE FRONT BEFORE SKIES GO SKC
LATER THIS EVENING. IN ADDITION...THE PUSH IMMEDIATELY BEHIND
FRONT COULD HAVE AN HOUR OR TWO OR STRONG NORTHWEST WINDS
POTENTIALLY GUSTING UP TO AROUND 30KT BEFORE WINDS BACK A BIT MORE
WESTERLY AND EASE MID-LATE EVENING. A VFR CEILING COULD MOVE BACK
IN WITH MID LEVEL CLOUDINESS AND POTENTAILLY SOME VIRGA OR EVEN
A SPRINKLE MONDAY AFTERNOON WITH CONTINUED LIGHT WESTERLY WINDS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN CIGS/PRECIP/WINDS THROUGH MID EVENING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
651 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* BRIEF PERIOD OF -RA/MVFR CIGS/30KT NW WINDS WITH FRONTAL PASSAGE
  THIS EVENING

IZZI

//DISCUSSION...UPDATED 00Z...

COLD FRONT WILL CONTINUE TO MOVE ACROSS THE TERMINALS EARLY THIS
EVENING WITH A BRIEF PERIOD OF LIGHT RAIN/SPRINKLES ALONG THE
FRONT. SMALL AREA OF MVFR CIGS WILL PROBABLY AFFECT THE TERMINALS
ALONG AND IMMEDIATELY IN THE WAKE OF THE FRONT BEFORE SKIES GO SKC
LATER THIS EVENING. IN ADDITION...THE PUSH IMMEDIATELY BEHIND
FRONT COULD HAVE AN HOUR OR TWO OR STRONG NORTHWEST WINDS
POTENTIALLY GUSTING UP TO AROUND 30KT BEFORE WINDS BACK A BIT MORE
WESTERLY AND EASE MID-LATE EVENING. A VFR CEILING COULD MOVE BACK
IN WITH MID LEVEL CLOUDINESS AND POTENTAILLY SOME VIRGA OR EVEN
A SPRINKLE MONDAY AFTERNOON WITH CONTINUED LIGHT WESTERLY WINDS.

IZZI

//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN CIGS/PRECIP/WINDS THROUGH MID EVENING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 12Z TUESDAY-12Z SUNDAY...UPDATED 00Z...

TUESDAY...VFR. WIND SHIFT TO NE WINDS PROBABLY 10KT OR GREATER.

WEDNESDAY...VFR. MODERATELY STRONG SOUTH WINDS DURING AFTERNOON.

WEDNESDAY NIGHT AND THURSDAY...PERIOD OF SHRA/TSRA. PERIODIC IFR
POSSIBLE.

FRIDAY...CHANCE OF MVFR CIGS. NE WINDS 10KT OR GREATER POSSIBLE.

SATURDAY...PROBABLY VFR.

IZZI

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 292144
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
444 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* STRONG SOUTHWEST WINDS THROUGH 23-00Z POSSIBLY GUSTING OVER 30KT
  AT TIMES
* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE AROUND
  00Z.
* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

IZZI

//DISCUSSION...UPDATED 22Z...

SENT AN EARLY 22Z AMENDMENT TO BACK OFF ON GUSTS THROUGH 23Z.
ACARS SOUNDINGS SHOW WINDS IN THE MIXED LAYER SLOWING EASING A
BIT. STRONGEST PRESSURE FALLS CONTINUE TO PUSH AWAY AND ANY
CLEARING LOOKS TO BE VERY SHORT LIVED AND CHANCES OF TOP OF THE
CHANNEL MIXING DOWN OF 35KT+ GUSTS ARE QUICKLY FADING. A BRIEF
GUST OR TWO UP TO 35KT CANNOT COMPLETELY BE RULED OUT BUT
PREVAILING GUSTS SHOULD REMAIN MOSTLY BELOW 30KT REST OF THE
AFTERNOON. BAND OF -RA/-SHRA IS DEVELOPING OVER SOUTHERN WI WITH
THE FRONT SO HAVE ADDED A SHORT PERIOD OF PREVAILING -RA/MVFR CIGS
AHEAD OF THE FRONT.

IZZI

UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM CONFIDENCE IN CIG TRENDS THIS EVENING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 292144
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
444 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* STRONG SOUTHWEST WINDS THROUGH 23-00Z POSSIBLY GUSTING OVER 30KT
  AT TIMES
* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE AROUND
  00Z.
* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

IZZI

//DISCUSSION...UPDATED 22Z...

SENT AN EARLY 22Z AMENDMENT TO BACK OFF ON GUSTS THROUGH 23Z.
ACARS SOUNDINGS SHOW WINDS IN THE MIXED LAYER SLOWING EASING A
BIT. STRONGEST PRESSURE FALLS CONTINUE TO PUSH AWAY AND ANY
CLEARING LOOKS TO BE VERY SHORT LIVED AND CHANCES OF TOP OF THE
CHANNEL MIXING DOWN OF 35KT+ GUSTS ARE QUICKLY FADING. A BRIEF
GUST OR TWO UP TO 35KT CANNOT COMPLETELY BE RULED OUT BUT
PREVAILING GUSTS SHOULD REMAIN MOSTLY BELOW 30KT REST OF THE
AFTERNOON. BAND OF -RA/-SHRA IS DEVELOPING OVER SOUTHERN WI WITH
THE FRONT SO HAVE ADDED A SHORT PERIOD OF PREVAILING -RA/MVFR CIGS
AHEAD OF THE FRONT.

IZZI

UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM CONFIDENCE IN CIG TRENDS THIS EVENING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292144
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
444 PM CDT SUN MAR 29 2015

.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* STRONG SOUTHWEST WINDS THROUGH 23-00Z POSSIBLY GUSTING OVER 30KT
  AT TIMES
* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE AROUND
  00Z.
* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

IZZI

//DISCUSSION...UPDATED 22Z...

SENT AN EARLY 22Z AMENDMENT TO BACK OFF ON GUSTS THROUGH 23Z.
ACARS SOUNDINGS SHOW WINDS IN THE MIXED LAYER SLOWING EASING A
BIT. STRONGEST PRESSURE FALLS CONTINUE TO PUSH AWAY AND ANY
CLEARING LOOKS TO BE VERY SHORT LIVED AND CHANCES OF TOP OF THE
CHANNEL MIXING DOWN OF 35KT+ GUSTS ARE QUICKLY FADING. A BRIEF
GUST OR TWO UP TO 35KT CANNOT COMPLETELY BE RULED OUT BUT
PREVAILING GUSTS SHOULD REMAIN MOSTLY BELOW 30KT REST OF THE
AFTERNOON. BAND OF -RA/-SHRA IS DEVELOPING OVER SOUTHERN WI WITH
THE FRONT SO HAVE ADDED A SHORT PERIOD OF PREVAILING -RA/MVFR CIGS
AHEAD OF THE FRONT.

IZZI

UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM CONFIDENCE IN CIG TRENDS THIS EVENING
* HIGH CONFIDENCE IN REMAINING FORECAST ELEMENTS

IZZI

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292036
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 PM CDT SUN MAR 29 2015


.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292036
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 PM CDT SUN MAR 29 2015


.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292036
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 PM CDT SUN MAR 29 2015


.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292036
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 PM CDT SUN MAR 29 2015


.SHORT TERM...
334 PM CDT

THIS EVENING THROUGH THURSDAY...

LOW PRESSURE WAS MOVING NORTH OF THE GREAT LAKES OVER ONTARIO
THIS AFTERNOON...TRAILING AN OCCLUDED FRONT INTO THE UPPER
MISSISSIPPI VALLEY TO A TRIPLE POINT SOMEWHERE NEAR NORTHEAST
IOWA. FROM THERE A WARM FRONT EXTENDED SOUTH ALONG THE MISSISSIPPI
RIVER ITSELF...WHILE A COLD FRONT WAS A LITTLE FURTHER TO THE WEST
ACROSS CENTRAL AND EAST CENTRAL IOWA. THIS COMPLEX SYNOPSIS OF
SURFACE FEATURES WILL BRING SEVERAL HOURS OF CHANGABLE WEATHER
ACROSS THE FORECAST AREA... WITH SHOWERS EXITING TO THE
EAST/SOUTHEAST COUNTIES THIS AFTERNOON WHILE SOME CLEARING OF
CLOUD COVER WORKS IN FROM THE SOUTHWEST. TEMPERATURES BEHIND BOTH
THE WARM AND COLD FRONTS ARE WARMER THAN OUR CURRENT MID-UPPER
30S...THUS LATE DAY RISES IN TO THE 40S OR EVEN A FEW LOWER 50S
ARE EXPECTED THROUGH SUNSET. IN ADDITION... NEAR-TERM HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL FOR SHOWERS TO
DEVELOP ALONG/AHEAD OF THE FRONT AS WE HEAD INTO EARLY
EVENING...THUS HAVE MAINTAINED A PERIOD OF CHANCE POPS WITH THE
FRONT FROM WEST TO EAST THROUGH MID-EVENING. GUSTY WINDS OF 30 TO
40 MPH...INITIALLY FROM THE SOUTH-SOUTHWEST AND THEN SHIFTING TO
THE WEST-NORTHWEST THIS EVENING...WILL CONTINUE AS WELL BEFORE
DIMINISHING TONIGHT. AIR MASS BEHIND THIS FRONT IS OF A PACIFIC
NATURE HOWEVER...AND MONDAY WILL BE MILDER THAN TODAY WITH MORE
SUNSHINE. A SHEARED MID-LEVEL WAVE APPROACHES IN NORTHWEST FLOW
ALOFT LATER MONDAY HOWEVER...WITH A SURFACE LOW PRESSURE
PROPAGATING SOUTHEAST FROM WI ACROSS SOUTHERN LAKE MICHIGAN AND
INTO INDIANA/OHIO BY TUESDAY MORNING. THIS WILL LIKELY BRING SOME
INCREASE IN CLOUD COVER TO EASTERN PARTS OF THE CWA LATER MONDAY
AFTERNOON AND NIGHT...WITH SOME GUIDANCE INDICATING LIGHT RAIN
DEVELOPING DURING THE EVENING.

THE LOW PULLS OFF TO THE SOUTHEAST ON TUESDAY...WITH TRAILING
COLD FRONT SAGGING ACROSS THE AREA AS SURFACE HIGH SPREADS ACROSS
THE NORTHERN LAKES. WHILE TEMPS SHOULD REACH THE UPPER 50S/NEAR 60
AWAY FROM THE LAKE...IT LOOKS LIKE THE FRONT/LAKE BREEZE COMBO
WILL LIKELY PRODUCE FALLING TEMPS ACROSS NORTHEAST IL/NORTHWEST
IND DURING THE AFTERNOON AS WINDS SHIFT NORTHEAST AND DROP TEMPS
NEAR THE LAKE. MORE AMPLIFIED UPPER TROUGH/LOW THEN COMES OUT OF
THE PACIFIC NORTHWEST AND ALONG THE INTERNATIONAL BORDER WEDNESDAY
HOWEVER...DEVELOPING DEEP SURFACE LOW WHICH MOVES INTO MANITOBA
AND WESTERN ONTARIO WEDNESDAY NIGHT. THIS RESULTS IN SOUTH WINDS
RETURNING AND BECOMING BREEZY...BUT PULLING TEMPS BACK UP ACROSS
THE CWA. LOW LEVEL THERMAL PROGS SUGGEST 70 MAY NOT BE OUT OF
REACH ESPECIALLY IN THE FAR WEST...WHILE 60S ARE LIKELY TO THE
EAST. COULD BE A LITTLE LAKE COOLING ALONG THE NORTH SHORE WITH
SLIGHT SOUTHEAST COMPONENT TO THE WIND ALONG THE LAKE.

RAIN AND THUNDERSTORM CHANCES THEN INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS COLD FRONT TRAILING FROM CANADIAN LOW APPROACHES AND
PASSES. THURSDAY COULD POTENTIALLY BE ANOTHER WARM DAY DEPENDING
ON TIMING OF THE COLD FRONT...AND CLOUD/PRECIP COVERAGE. MID 60S
APPEAR REASONABLE AT THIS DISTANCE.

RATZER

&&

.LONG TERM...
334 PM CDT

FRIDAY THROUGH SUNDAY...

THOUGH PATTERN REMAINS SOMEWHAT PROGRESSIVE THROUGH THE PERIOD...
GUIDANCE IN GOOD AGREEMENT IN DEVELOPING LARGE SCALE TROUGH OVER
THE EASTERN PORTION OF NORTH AMERICA FRIDAY INTO NEXT WEEKEND.
THIS SETS UP COOL HIGH PRESSURE ACROSS THE UPPER MIDWEST AND GREAT
LAKES... WITH RELATIVELY LOW PRECIP CHANCES. SOME MODERATION
EXPECTED AS THE HIGH MOVES EAST TOWARD THE END OF THE PERIOD.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 292000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 03Z/10PM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 292000 CCA
AFDLOT

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 292000 CCA
AFDLOT

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 292000 CCA
AFDLOT

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 292000 CCA
AFDLOT

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
300 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
259 PM CDT

OBS ARE NOT SUPPORTING STORM FORCE GUSTS OVER THE NORTHERN HALF OF
THE LAKE SO WILL DROP THE STORM FORCE WARNING WITH THE AFTN UPDATE.
GUIDANCE ALSO HOLDS ON TO GALES OVER THE OPEN WATERS INTO THIS
EVENING SO EXTENDED THE OPEN WATER GALE WARNING INTO THIS EVENING.
WILL HOLD ON TO THE CURRENT NSH GALE WARNING UNTIL 7PM CDT/00Z. A
SMALL CRAFT ADVISORY WILL THEN BE NEEDED THROUGH 09Z/4AM CDT.

WITH HIGH PRESSURE TO OUR SE AND LOW PRESSURE TO OUR NORTH...WE ARE
UNDER A TIGHTENED PRESSURE GRADIENT RESULTING IN STRONG WINDS.  THE
GRADIENT WEAKENS AS BOTH FEATURES CONTINUE EAST AND THE LOWS COLD
FRONT SWINGS OVERHEAD THIS EVENING. WINDS WILL DIMINISH AND TURN
WEST BEHIND THE COLD FRONT.  LIGHT WINDS BECOME SOUTHEAST OR SOUTH
BY MONDAY EVENING AS A WEAK RIDGE SCOOTS BY.  A WEAK LOW PASSES OVER
THE SOUTHERN END OF THE LAKE LATE MONDAY NIGHT INTO TUESDAY MORNING
WITH EAST WINDS OVER THE NORTHERN HALF OF THE LAKE AND SOUTHWEST TO
WEST WINDS OVER THE SOUTHERN HALF BOTH 10-20 KT.  HIGH PRESSURE THEN
SLIDES OVER THE LAKE TUESDAY EVENING WITH WINDS BECOMING EAST
OVERNIGHT.  SOUTH WINDS INCREASE TO 30 KT WEDNESDAY AFTERNOON AHEAD
OF THE NEXT LOW THAT PASSES OVER ONTARIO THURSDAY.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 9 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* SOUTHWEST TO SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT AND
  EXPECTED TO INCREASE TO AROUND 35 KT FOR A FEW HOURS TOWARDS
  21Z. CANNOT RULE OUT GUSTS NEAR 40 KT FOR A SHORT TIME.

* WINDS TREND MORE SOUTHWEST THEN WEST TOWARD 00Z WITH SPEEDS
  EASING.

* CHANCE FOR SCATTERED SHOWERS WITH A COLD FRONTAL PASSAGE TOWARD
  00Z.

* SHORT PERIOD OF MVFR CIGS POSSIBLE EARLY THIS EVENING.

MDB

//DISCUSSION...UPDATED 20Z...

SATELLITE SHOWS A WEDGE OF SCATTERING SKIES NOSING INTO NORTHERN
ILLINOIS WHICH WILL SPREAD ACROSS ORD/MDW/DPA/GYY IN THE NEXT FEW
HOURS. THIS WILL LIKELY ALLOW MORE FREQUENT GUSTS AS WELL AS AN
INCREASE IN GUST MAGNITUDE. AREAS THAT HAVE SCATTERED TO THE WEST
ARE REACHING THEIR EXPECTED GUST POTENTIAL THOUGH WIND SPEEDS
ABOVE THE SURFACE ARE LOWER THERE THAN THEY ARE LOCALLY. THIS
RAISES THE CONCERN THAT GUSTS WILL EXCEED 35 KT FOR A SHORT TIME
AS MIXING DEEPENS WITH DECREASING CLOUD COVER AND COULD REACH 40
KT. WIND SPEEDS THEN EASE UP AS A COLD FRONT APPROACHES TOWARD
00Z. RETAINED TEMPO SHOWER MENTION FOR NOW AS THERE MAY BE SOME
DEVELOPMENT AHEAD OF THE FRONT BUT COVERAGE MAY BE MINIMAL.

FROM 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH CONFIDENCE IN WIND DIRECTION TRENDS/TIMING. HIGH CONFIDENCE
  IN 30 KT GUSTS WITH MEDIUM CONFIDENCE IN 35 KT GUSTS AND LOW
  CONFIDENCE THAT THEY WILL PUSH 40 KT. MEDIUM-HIGH CONFIDENCE IN
  HIGHEST GUSTS OCCURRING FOR A FEW HOURS STARTING AROUND 21Z.

* MEDIUM CONFIDENCE IN SOME SHOWER ACTIVITY WITH FRONTAL PASSAGE.

* MEDIUM CONFIDENCE THAT CHANCE FOR MVFR STRATUS IS LOW THIS
  EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 291944
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
244 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.


&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forcast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.


&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Geelhart




000
FXUS63 KILX 291944
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
244 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.


&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forcast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.


&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Geelhart




000
FXUS63 KILX 291944
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
244 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.


&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forcast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.


&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Geelhart




000
FXUS63 KILX 291944
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
244 PM CDT Sun Mar 29 2015

.SHORT TERM...(Tonight)
ISSUED AT 241 PM CDT SUN MAR 29 2015

Initial band of light rain had largely moved into Indiana by about
12:30 pm. Secondary batch of showers was trying to form at mid
afternoon, but low level air mass remains rather dry, and cloud
heights are mostly above 7,000 feet as well, so this has been
struggling to produce much more than sprinkles. Wind gusts 35-45 mph
formed over the western CWA this morning and have shifted to more
across the east this afternoon, but still some gusts near 25 mph
over the western CWA as well.

Frontal boundary was shown on 2 pm surface map from western
Wisconsin, across eastern Iowa, to west central Missouri. This is
progged by the short-term models to be near Galesburg by 6 pm and
along the I-70 corridor toward 10 pm. HRRR has been persistent in
developing a narrow band of showers along it, the initial hints of
which are seen on regional radar mosaics over southwest Wisconsin.
However, while some additional moisture will spread into the
forecast area the remainder of the afternoon (perhaps getting dew
points up to around 40), not terribly confident that this will have
any better luck reaching the ground this far to the south. Have
maintained some slight chance PoP`s early evening across about the
east half of the forecast area, but went dry everywhere by 10 pm.
Clearing line is not too far away in northwest Iowa, and most of the
CWA should be mostly clear by midnight.


&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 241 PM CDT SUN MAR 29 2015

A rather quiet weather pattern to start the week off with as our
area will be influenced by northwest flow aloft. Surface high
pressure will drift south of our area during the day Monday bringing
warmer conditions to the forecast area while a shortwave trof shifts
southeast into the upper Midwest late in the day. This feature has
been expected to keep its more widespread cloud cover and rain to
our north and that trend is still holding with this mornings 12z
model runs. The boundary should push across the area Tuesday
afternoon and be close to the Ohio River Valley Tuesday evening as
surface high pressure shifts south from the upper Great Lakes into
our area at night. Upper level ridging is then forecast to build over
the region on Wednesday in response to a rather potent upper level
shortwave forecast to move across the northern Rockies Wednesday. The
southerly flow ahead of the upper wave is forecast to bring in some
mild air to the region Wednesday with afternoon highs in the upper 60s
east to the lower or middle 70s far southwest.

Have chosen the slower solutions (12z ECMWF and Canadian models)
with respect to the timing of the cold front and showers and storms
into our area late Wednesday night and especially during the day on
Thursday. Fairly decent instability and shear parameters ahead of
the upper wave to our west late Wednesday but based on the projected
timing of the front into our area, the storms should be less intense
as they track into our area early Thursday morning with the better
chances for showers and storms across the forecast area during the
day on Thursday. The front will get pushed southeast into the Ohio
River Valley Thursday night with models suggesting another shortwave
to induce a weak wave on the boundary with a renewed threat for
showers spreading back over the forcast area again Thursday night
into parts of Friday with the higher POPs shifting into southeast
Illinois during the day Friday before the system pushes away from
the area next weekend bringing in cooler weather for at least the
start of the Easter weekend.

After a nice recovery in temperatures starting tomorrow, which should
last through at least Thursday, the mercury will drop off to below normal
levels once again thru Saturday before we see temperatures start to moderate
again on Easter Sunday. Precip-wise, after our slight chance POPs in
the southeast Friday evening, will keep the remainder of the forecast
dry for now with longer range solutions suggesting some shower chances may
return late Sunday night or next Monday.


&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Geelhart




000
FXUS63 KLOT 291752
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1252 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LINGERING DRIZZLE/LIGHT RAIN EXITING WITHIN THE NEXT HOUR.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT WITH SOMEWHAT
  ERRATIC FREQUENCY. THINNING CLOUD COVER MAY ALLOW FOR INCREASED
  GUSTS AROUND 35 KT MID AFTERNOON.

* WINDS SHIFT WEST-NORTHWEST AROUND 00Z WITH SPEEDS EASING.

* MVFR CIGS POSSIBLE THIS EVENING.

MDB

//DISCUSSION...UPDATED 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN PRECIP FORECAST.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC 30 KT GUSTS EARLY AFTERNOON.
  MEDIUM CONFIDENCE IN 35 KT GUSTS OCCURRING MID/LATE AFTERNOON.
  MEDIUM-HIGH CONFIDENCE IN TIMING OF WIND SHIFT.

* LOW CONFIDENCE IN MVFR POTENTIAL THIS EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291752
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1252 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LINGERING DRIZZLE/LIGHT RAIN EXITING WITHIN THE NEXT HOUR.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT WITH SOMEWHAT
  ERRATIC FREQUENCY. THINNING CLOUD COVER MAY ALLOW FOR INCREASED
  GUSTS AROUND 35 KT MID AFTERNOON.

* WINDS SHIFT WEST-NORTHWEST AROUND 00Z WITH SPEEDS EASING.

* MVFR CIGS POSSIBLE THIS EVENING.

MDB

//DISCUSSION...UPDATED 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN PRECIP FORECAST.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC 30 KT GUSTS EARLY AFTERNOON.
  MEDIUM CONFIDENCE IN 35 KT GUSTS OCCURRING MID/LATE AFTERNOON.
  MEDIUM-HIGH CONFIDENCE IN TIMING OF WIND SHIFT.

* LOW CONFIDENCE IN MVFR POTENTIAL THIS EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291752
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1252 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LINGERING DRIZZLE/LIGHT RAIN EXITING WITHIN THE NEXT HOUR.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT WITH SOMEWHAT
  ERRATIC FREQUENCY. THINNING CLOUD COVER MAY ALLOW FOR INCREASED
  GUSTS AROUND 35 KT MID AFTERNOON.

* WINDS SHIFT WEST-NORTHWEST AROUND 00Z WITH SPEEDS EASING.

* MVFR CIGS POSSIBLE THIS EVENING.

MDB

//DISCUSSION...UPDATED 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN PRECIP FORECAST.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC 30 KT GUSTS EARLY AFTERNOON.
  MEDIUM CONFIDENCE IN 35 KT GUSTS OCCURRING MID/LATE AFTERNOON.
  MEDIUM-HIGH CONFIDENCE IN TIMING OF WIND SHIFT.

* LOW CONFIDENCE IN MVFR POTENTIAL THIS EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291752
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1252 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LINGERING DRIZZLE/LIGHT RAIN EXITING WITHIN THE NEXT HOUR.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT WITH SOMEWHAT
  ERRATIC FREQUENCY. THINNING CLOUD COVER MAY ALLOW FOR INCREASED
  GUSTS AROUND 35 KT MID AFTERNOON.

* WINDS SHIFT WEST-NORTHWEST AROUND 00Z WITH SPEEDS EASING.

* MVFR CIGS POSSIBLE THIS EVENING.

MDB

//DISCUSSION...UPDATED 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN PRECIP FORECAST.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC 30 KT GUSTS EARLY AFTERNOON.
  MEDIUM CONFIDENCE IN 35 KT GUSTS OCCURRING MID/LATE AFTERNOON.
  MEDIUM-HIGH CONFIDENCE IN TIMING OF WIND SHIFT.

* LOW CONFIDENCE IN MVFR POTENTIAL THIS EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291752
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1252 PM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LINGERING DRIZZLE/LIGHT RAIN EXITING WITHIN THE NEXT HOUR.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH-SOUTHWEST WINDS GUSTING TO AROUND 30 KT WITH SOMEWHAT
  ERRATIC FREQUENCY. THINNING CLOUD COVER MAY ALLOW FOR INCREASED
  GUSTS AROUND 35 KT MID AFTERNOON.

* WINDS SHIFT WEST-NORTHWEST AROUND 00Z WITH SPEEDS EASING.

* MVFR CIGS POSSIBLE THIS EVENING.

MDB

//DISCUSSION...UPDATED 18Z...

THE MAIN AREA OF PRECIP IS EXITING TO THE EAST WITH A SMALL AREA
OF DRIZZLE ON THE BACK EDGE...WHICH IS LEADING TO A LOWERING OF
CIGS TOWARDS 030...THOUGH THIS DOES NOT LOOK TO LAST BEYOND 19Z.
UPSTREAM OBS/SATELLITE TRENDS SUPPORT A THINNING OF CLOUDS INTO
MID AFTERNOON THOUGH SOME STRATO CU MAY FORM. COULD BE TOO
PESSIMISTIC WITH BROKEN LOWER LEVEL CLOUD COVER BY MID AFTERNOON.
WIND GUSTS HAVE BEEN ERRATIC BUT SHOWING SIGNS OF INCREASING TO
THE WEST WHERE CLOUDS ARE THINNING. WINDS QUICKLY INCREASE OFF THE
DECK SO IT WILL NOT TAKE MUCH TO REALIZE 30-35 KT GUSTS AT THE
SURFACE. FREQUENCY OF 30+ KT GUSTS LOOKS TO BE LOW BEFORE
20Z...BUT DECREASING LOWER CLOUD COVER WOULD BE SUPPORTIVE OF
INCREASED GUSTS BY MID AFTERNOON. SHOULD THERE BE A PERIOD OF
DECENT SUNSHINE THEN GUSTS MAY TOP 35 KT FOR A SHORT TIME.

A COLD FRONT WILL BE CROSSING THE AREA LATE THIS AFTERNOON AND
EARLY THIS EVENING TURNING WINDS WEST TO WEST-NORTHWEST. HAVE SPED
UP THE PASSAGE OF THE FRONT BY ABOUT AN HOUR AND BUMPED UP GUSTS A
BIT BEHIND IT. MVFR STRATUS MAY ALSO BECOME BROKEN FOR A FEW HOURS
BUT MUCH OF WHAT IS BEHIND THE FRONT NOW LOOKS TO BE DIURNALLY
DRIVEN SO OPTED TO KEEP SCATTERED MVFR LEVEL CLOUDS. WINDS WILL
EASE UP THROUGH THE EVENING WITH CLOUD COVER DIMINISHING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN PRECIP FORECAST.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC 30 KT GUSTS EARLY AFTERNOON.
  MEDIUM CONFIDENCE IN 35 KT GUSTS OCCURRING MID/LATE AFTERNOON.
  MEDIUM-HIGH CONFIDENCE IN TIMING OF WIND SHIFT.

* LOW CONFIDENCE IN MVFR POTENTIAL THIS EVENING.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 291723
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1223 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Geelhart







000
FXUS63 KILX 291723
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1223 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Geelhart






000
FXUS63 KILX 291723
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1223 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Geelhart







000
FXUS63 KILX 291723
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1223 PM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1222 PM CDT SUN MAR 29 2015

Initial band of rain is now exiting KCMI, although another band is
expected to develop around mid-afternoon. KCMI/KDEC are most
likely to be affected by this next band in the 21-23Z time frame.
Like the earlier rain, mainly VFR conditions expected, with
perhaps visibility briefly dipping to around 4-5SM if one of the
heavier showers happens to pass over the airport. The strongest
wind gusts will be early in the afternoon, but gusts to around 25
knots still likely mid-late afternoon. A frontal boundary will be
moving through the TAF sites in the 23Z-02Z time frame, switching
winds around to the northwest. These winds will diminish and turn
more southwest overnight, as an area of high pressure settles
across Missouri.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Geelhart






000
FXUS63 KLOT 291659
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1159 AM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

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000
FXUS63 KLOT 291659
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1159 AM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291659
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1159 AM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291659
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1159 AM CDT SUN MAR 29 2015

.UPDATE...

FOR LATE MORNING UPDATE...
1159 AM CDT

BAND OF RAIN...INITIALLY MIXED WITH SLEET AND SOME WET SNOW...WAS
MOVING ACROSS THE CENTRAL AND EASTERN PARTS OF THE FORECAST AREA AT
MIDDAY IN ASSOCIATION WITH WARM/MOIST ADVECTION COINCIDENT WITH
ELEVATED WARM FRONTAL FEATURE IN ADVANCE OF MID-LEVEL SHORT WAVE
TRACKING ACROSS THE UPPER MIDWEST. WHILE MANY METARS AND PING
PROJECT OBS HAVE REPORTED RAIN MIXED WITH SLEET/SNOW...SURFACE
TEMPERATURES HAVE WARMED INTO THE MID-UPPER 30S FOR THE MOST PART
AND WARMING LOW-LEVEL THERMAL PROFILES AND LOSS OF MOISTURE IN ICE
PRODUCTION LAYER SHOULD SUPPORT JUST RAIN FOR ANY LINGERING
PRECIPITATION BEHIND THE INITIAL BAND INTO THIS AFTERNOON. AS FOR
TIMING...INITIAL HEAVIER BAND SHOULD CONTINUE TO MOVE EAST OF THE
CWA EARLY THIS AFTERNOON...THOUGH ADDITIONAL SHOWERS ARE EXPECTED TO
DEVELOP LATER AS COLD FRONT CURRENTLY ACROSS CENTRAL IOWA APPROACHES
ALONG WITH SUPPORT FROM SECOND VORT DIGGING INTO THE REGION FROM THE
NORTHWEST. THESE SHOWERS SHOULD EXIT THE AREA EARLY THIS EVENING AS
COLD FRONT SWEEPS THROUGH.

OTHERWISE...VERY GUSTY SOUTH WINDS WILL CONTINUE TO SLOWLY WARM
TEMPERATURES ACROSS THE AREA THROUGH LATE AFTERNOON...WITH UPSTREAM
TEMPS FROM THE MID 40S TO AROUND 50 EXPECTED TO SPREAD INTO THE CWA
LATE. SOUTH WINDS WILL CONTINUE TO GUST NEAR 40 MPH BEFORE
EVENTUALLY SHIFTING WEST AND DIMINISHING A BIT EARLY THIS EVENING
BEHIND THE COLD FRONT.

RATZER

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291624
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1124 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291624
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1124 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291624
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1124 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 291624
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1124 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 16Z...

* RAIN EXITING TOWARD 1730Z. BRIEF MVFR VSBY POSSIBLE UNTIL THEN.
  ADDITIONAL SHOWERS POSSIBLE LATE AFTERNOON.

* SOUTH TO SOUTH-SOUTHWEST WINDS GUSTING 30-35 KT THROUGH THE
  AFTERNOON BECOMING WEST THEN NORTHWEST WITH COLD FRONTAL
  PASSAGE 00 OR 01Z.

* CIGS MAY LOWER TO NEAR 030 THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 16Z...

PRECIP IS MOVING ACROSS THE CHICAGO/NW IN TERMINALS AND EXITING
THE RFD AREA. UPSTREAM OBS BEHIND THE RAINFALL SHOW LOWER GUSTS
BUT WOULD EXPECT THIS TO BE SHORT LIVED WITH MIXING RECOVERING.
WILL NEED TO KEEP AN EYE ON THIS THOUGH. CLOUD COVER MAY MAY
ULTIMATELY TEMPER THE FREQUENCY OF GUSTS...ESPECIALLY PRIOR TO
18Z. OBS SHOW A SMALL AREA OF MVFR CIGS ACROSS NORTHEAST IOWA AND
MAY SKIRT RFD INTO MIDDAY BUT WILL KEEP THIS NORTH OF THE OTHER
TERMINALS FOR NOW. SOME SPOTTY SHOWERS OR SPRINKLES MAY LINGER
THROUGH THE AFTERNOON BUT WILL DRY THE TAFS OUT UNTIL LATE
AFTERNOON WHEN THE COLD FRONT MAY BRING SOME SHOWERS AHEAD OF IT.
MAY ALSO NEED TO SPEED UP THE COLD FRONTAL PASSAGE TIMING BY ABOUT
AN HOUR OR SO WITH UPCOMING TAFS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 16Z...

* HIGH CONFIDENCE IN PRECIP TIMING. AND THAT MVFR VSBY IN RAIN
  WOULD BE BRIEF.

* HIGH CONFIDENCE IN 30-35 KT GUSTS AND DIRECTION THROUGH THE
  AFTERNOON. THERE COULD BE A BRIEF LULL IN GUSTS IMMEDIATELY
  FOLLOWING PRECIP.

* MEDIUM CONFIDENCE IN CIG TRENDS.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 291442
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
942 AM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 646 AM CDT SUN MAR 29 2015

Rain showers will spread from west to east across central IL
starting around 12Z. Observations in the approaching system
showing VFR conditions, however there will likely be isolated MVFR
cigs/vsbys in heavier showers and perhaps an isolated thunderstorm
as it crosses the central IL terminals. Showers expected to begin
around 14Z at KPIA to around 16Z at KDEC/KCMI based on current
timing, consistent with HRRR model. Strong and gusty southerly
winds 20-25 kts with gusts 30-35 kts are expected as well. By late
afternoon a slight wind shift and decrease to SW 15-20g25 kts is
expected as showers taper off. Winds to continue shifting to NW
and decreasing overnight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton






000
FXUS63 KILX 291442
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
942 AM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 646 AM CDT SUN MAR 29 2015

Rain showers will spread from west to east across central IL
starting around 12Z. Observations in the approaching system
showing VFR conditions, however there will likely be isolated MVFR
cigs/vsbys in heavier showers and perhaps an isolated thunderstorm
as it crosses the central IL terminals. Showers expected to begin
around 14Z at KPIA to around 16Z at KDEC/KCMI based on current
timing, consistent with HRRR model. Strong and gusty southerly
winds 20-25 kts with gusts 30-35 kts are expected as well. By late
afternoon a slight wind shift and decrease to SW 15-20g25 kts is
expected as showers taper off. Winds to continue shifting to NW
and decreasing overnight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton







000
FXUS63 KILX 291442
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
942 AM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 646 AM CDT SUN MAR 29 2015

Rain showers will spread from west to east across central IL
starting around 12Z. Observations in the approaching system
showing VFR conditions, however there will likely be isolated MVFR
cigs/vsbys in heavier showers and perhaps an isolated thunderstorm
as it crosses the central IL terminals. Showers expected to begin
around 14Z at KPIA to around 16Z at KDEC/KCMI based on current
timing, consistent with HRRR model. Strong and gusty southerly
winds 20-25 kts with gusts 30-35 kts are expected as well. By late
afternoon a slight wind shift and decrease to SW 15-20g25 kts is
expected as showers taper off. Winds to continue shifting to NW
and decreasing overnight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton






000
FXUS63 KILX 291442
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
942 AM CDT Sun Mar 29 2015

.UPDATE...
ISSUED AT 940 AM CDT SUN MAR 29 2015

The rain has made some steady progress eastward, and was generally
along a Lacon to Jacksonville line at 930 am. Dual-pol radar data
suggests some mixed precipitation across the far northern CWA,
which has also been reported at the Galesburg airport, although
web cams are not showing much of an issue with it. HRRR guidance
has been handling this fairly well, and it was used to fine-tune
the precipitation trends today. Bumped up PoP`s to the categorical
range for a few hours across the north as this band moves through.
Secondary band is expected to develop between the Illinois River
and I-55 early this afternoon, and the HRRR suggests perhaps one
final band toward sunset with the front itself. Winds have been
picking up in many areas and gusts over 30 mph already being
reported across the central and western CWA. Area of 35-40 mph
gusts will be working its way eastward with time and should linger
into early afternoon before starting to diminish a bit.

&&

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial FROPA. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 646 AM CDT SUN MAR 29 2015

Rain showers will spread from west to east across central IL
starting around 12Z. Observations in the approaching system
showing VFR conditions, however there will likely be isolated MVFR
cigs/vsbys in heavier showers and perhaps an isolated thunderstorm
as it crosses the central IL terminals. Showers expected to begin
around 14Z at KPIA to around 16Z at KDEC/KCMI based on current
timing, consistent with HRRR model. Strong and gusty southerly
winds 20-25 kts with gusts 30-35 kts are expected as well. By late
afternoon a slight wind shift and decrease to SW 15-20g25 kts is
expected as showers taper off. Winds to continue shifting to NW
and decreasing overnight.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Geelhart
SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton







000
FXUS63 KLOT 291412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* RAIN ARRIVES 1530-16Z OR SO WITH BRIEF PERIOD OF SLEET OR SNOW
  POSSIBLE AT ONSET. ADDITIONAL SHOWERS POSSIBLE THROUGH EARLY
  AFTERNOON.
* MVFR CIGS POSSIBLE...MAINLY THIS AFTERNOON.
* CHANCE OF ANOTHER ROUND OF BRIEF RAIN SHOWERS
  TOWARD SUNSET.

MDB

//DISCUSSION...UPDATED 14Z...

BAND OF PRECIP IS NOW APPROACHING RFD AND WILL BE REACHING THE
CHICAGO AREA 1530-16Z OR SO. THE BAND HAS NARROWED QUITE A BIT
OVER THE LAST HOUR OR TWO SO DURATION OF THE MORE SOLID PRECIP
LOOKS TO BE 60-90 MIN...WITH SOME ADDITIONAL SCATTERED SHOWER
ACTIVITY TRAILING IT. BASED ON LATEST SURFACE TEMPS FZRA WILL
OCCUR FOR A TIME AT RFD ALONG WITH A MIX OF RAIN AND SLEET OR
SNOW...BUT TEMPS WILL WARM SO FZRA MAY BE SHORT LIVED.
ELSEWHERE...MAINLY RAIN LOOKS TO OCCUR BUT CANNOT RULE OUT SOME
SLEET OR POSSIBLY SOME SNOW AT ONSET.

WIND GUSTS ARE COMING UP SPORADICALLY AND GUSTS MAY BE TEMPERED
DURING PRECIP BUT 30-35 KT GUSTS STILL LOOK ON TRACK AND SHOULD
DEVELOP AHEAD OF THE PRECIP AS WELL. NOT MUCH IN THE WAY OF MVFR
CIGS UPSTREAM BUT EXPECT DEVELOPMENT THIS AFTERNOON AROUND 030.
AM A LITTLE CONCERNED THAT GUSTS COULD BE A LITTLE UNDERDONE THIS
AFTERNOON IF CLOUD COVER IS NOT AS WIDESPREAD OR WE MIX A LITTLE
DEEPER. WILL NEED TO MONITOR AS WARMING OCCURS OVER THE NEXT FEW
HOURS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING.
* MEDIUM-HIGH IN BEST CHANCE FOR MVFR BEING THIS AFTERNOON BUT LOW
  THAT IT WILL OCCUR.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* RAIN ARRIVES 1530-16Z OR SO WITH BRIEF PERIOD OF SLEET OR SNOW
  POSSIBLE AT ONSET. ADDITIONAL SHOWERS POSSIBLE THROUGH EARLY
  AFTERNOON.
* MVFR CIGS POSSIBLE...MAINLY THIS AFTERNOON.
* CHANCE OF ANOTHER ROUND OF BRIEF RAIN SHOWERS
  TOWARD SUNSET.

MDB

//DISCUSSION...UPDATED 14Z...

BAND OF PRECIP IS NOW APPROACHING RFD AND WILL BE REACHING THE
CHICAGO AREA 1530-16Z OR SO. THE BAND HAS NARROWED QUITE A BIT
OVER THE LAST HOUR OR TWO SO DURATION OF THE MORE SOLID PRECIP
LOOKS TO BE 60-90 MIN...WITH SOME ADDITIONAL SCATTERED SHOWER
ACTIVITY TRAILING IT. BASED ON LATEST SURFACE TEMPS FZRA WILL
OCCUR FOR A TIME AT RFD ALONG WITH A MIX OF RAIN AND SLEET OR
SNOW...BUT TEMPS WILL WARM SO FZRA MAY BE SHORT LIVED.
ELSEWHERE...MAINLY RAIN LOOKS TO OCCUR BUT CANNOT RULE OUT SOME
SLEET OR POSSIBLY SOME SNOW AT ONSET.

WIND GUSTS ARE COMING UP SPORADICALLY AND GUSTS MAY BE TEMPERED
DURING PRECIP BUT 30-35 KT GUSTS STILL LOOK ON TRACK AND SHOULD
DEVELOP AHEAD OF THE PRECIP AS WELL. NOT MUCH IN THE WAY OF MVFR
CIGS UPSTREAM BUT EXPECT DEVELOPMENT THIS AFTERNOON AROUND 030.
AM A LITTLE CONCERNED THAT GUSTS COULD BE A LITTLE UNDERDONE THIS
AFTERNOON IF CLOUD COVER IS NOT AS WIDESPREAD OR WE MIX A LITTLE
DEEPER. WILL NEED TO MONITOR AS WARMING OCCURS OVER THE NEXT FEW
HOURS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING.
* MEDIUM-HIGH IN BEST CHANCE FOR MVFR BEING THIS AFTERNOON BUT LOW
  THAT IT WILL OCCUR.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* RAIN ARRIVES 1530-16Z OR SO WITH BRIEF PERIOD OF SLEET OR SNOW
  POSSIBLE AT ONSET. ADDITIONAL SHOWERS POSSIBLE THROUGH EARLY
  AFTERNOON.
* MVFR CIGS POSSIBLE...MAINLY THIS AFTERNOON.
* CHANCE OF ANOTHER ROUND OF BRIEF RAIN SHOWERS
  TOWARD SUNSET.

MDB

//DISCUSSION...UPDATED 14Z...

BAND OF PRECIP IS NOW APPROACHING RFD AND WILL BE REACHING THE
CHICAGO AREA 1530-16Z OR SO. THE BAND HAS NARROWED QUITE A BIT
OVER THE LAST HOUR OR TWO SO DURATION OF THE MORE SOLID PRECIP
LOOKS TO BE 60-90 MIN...WITH SOME ADDITIONAL SCATTERED SHOWER
ACTIVITY TRAILING IT. BASED ON LATEST SURFACE TEMPS FZRA WILL
OCCUR FOR A TIME AT RFD ALONG WITH A MIX OF RAIN AND SLEET OR
SNOW...BUT TEMPS WILL WARM SO FZRA MAY BE SHORT LIVED.
ELSEWHERE...MAINLY RAIN LOOKS TO OCCUR BUT CANNOT RULE OUT SOME
SLEET OR POSSIBLY SOME SNOW AT ONSET.

WIND GUSTS ARE COMING UP SPORADICALLY AND GUSTS MAY BE TEMPERED
DURING PRECIP BUT 30-35 KT GUSTS STILL LOOK ON TRACK AND SHOULD
DEVELOP AHEAD OF THE PRECIP AS WELL. NOT MUCH IN THE WAY OF MVFR
CIGS UPSTREAM BUT EXPECT DEVELOPMENT THIS AFTERNOON AROUND 030.
AM A LITTLE CONCERNED THAT GUSTS COULD BE A LITTLE UNDERDONE THIS
AFTERNOON IF CLOUD COVER IS NOT AS WIDESPREAD OR WE MIX A LITTLE
DEEPER. WILL NEED TO MONITOR AS WARMING OCCURS OVER THE NEXT FEW
HOURS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING.
* MEDIUM-HIGH IN BEST CHANCE FOR MVFR BEING THIS AFTERNOON BUT LOW
  THAT IT WILL OCCUR.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* RAIN ARRIVES 1530-16Z OR SO WITH BRIEF PERIOD OF SLEET OR SNOW
  POSSIBLE AT ONSET. ADDITIONAL SHOWERS POSSIBLE THROUGH EARLY
  AFTERNOON.
* MVFR CIGS POSSIBLE...MAINLY THIS AFTERNOON.
* CHANCE OF ANOTHER ROUND OF BRIEF RAIN SHOWERS
  TOWARD SUNSET.

MDB

//DISCUSSION...UPDATED 14Z...

BAND OF PRECIP IS NOW APPROACHING RFD AND WILL BE REACHING THE
CHICAGO AREA 1530-16Z OR SO. THE BAND HAS NARROWED QUITE A BIT
OVER THE LAST HOUR OR TWO SO DURATION OF THE MORE SOLID PRECIP
LOOKS TO BE 60-90 MIN...WITH SOME ADDITIONAL SCATTERED SHOWER
ACTIVITY TRAILING IT. BASED ON LATEST SURFACE TEMPS FZRA WILL
OCCUR FOR A TIME AT RFD ALONG WITH A MIX OF RAIN AND SLEET OR
SNOW...BUT TEMPS WILL WARM SO FZRA MAY BE SHORT LIVED.
ELSEWHERE...MAINLY RAIN LOOKS TO OCCUR BUT CANNOT RULE OUT SOME
SLEET OR POSSIBLY SOME SNOW AT ONSET.

WIND GUSTS ARE COMING UP SPORADICALLY AND GUSTS MAY BE TEMPERED
DURING PRECIP BUT 30-35 KT GUSTS STILL LOOK ON TRACK AND SHOULD
DEVELOP AHEAD OF THE PRECIP AS WELL. NOT MUCH IN THE WAY OF MVFR
CIGS UPSTREAM BUT EXPECT DEVELOPMENT THIS AFTERNOON AROUND 030.
AM A LITTLE CONCERNED THAT GUSTS COULD BE A LITTLE UNDERDONE THIS
AFTERNOON IF CLOUD COVER IS NOT AS WIDESPREAD OR WE MIX A LITTLE
DEEPER. WILL NEED TO MONITOR AS WARMING OCCURS OVER THE NEXT FEW
HOURS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING.
* MEDIUM-HIGH IN BEST CHANCE FOR MVFR BEING THIS AFTERNOON BUT LOW
  THAT IT WILL OCCUR.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* RAIN ARRIVES 1530-16Z OR SO WITH BRIEF PERIOD OF SLEET OR SNOW
  POSSIBLE AT ONSET. ADDITIONAL SHOWERS POSSIBLE THROUGH EARLY
  AFTERNOON.
* MVFR CIGS POSSIBLE...MAINLY THIS AFTERNOON.
* CHANCE OF ANOTHER ROUND OF BRIEF RAIN SHOWERS
  TOWARD SUNSET.

MDB

//DISCUSSION...UPDATED 14Z...

BAND OF PRECIP IS NOW APPROACHING RFD AND WILL BE REACHING THE
CHICAGO AREA 1530-16Z OR SO. THE BAND HAS NARROWED QUITE A BIT
OVER THE LAST HOUR OR TWO SO DURATION OF THE MORE SOLID PRECIP
LOOKS TO BE 60-90 MIN...WITH SOME ADDITIONAL SCATTERED SHOWER
ACTIVITY TRAILING IT. BASED ON LATEST SURFACE TEMPS FZRA WILL
OCCUR FOR A TIME AT RFD ALONG WITH A MIX OF RAIN AND SLEET OR
SNOW...BUT TEMPS WILL WARM SO FZRA MAY BE SHORT LIVED.
ELSEWHERE...MAINLY RAIN LOOKS TO OCCUR BUT CANNOT RULE OUT SOME
SLEET OR POSSIBLY SOME SNOW AT ONSET.

WIND GUSTS ARE COMING UP SPORADICALLY AND GUSTS MAY BE TEMPERED
DURING PRECIP BUT 30-35 KT GUSTS STILL LOOK ON TRACK AND SHOULD
DEVELOP AHEAD OF THE PRECIP AS WELL. NOT MUCH IN THE WAY OF MVFR
CIGS UPSTREAM BUT EXPECT DEVELOPMENT THIS AFTERNOON AROUND 030.
AM A LITTLE CONCERNED THAT GUSTS COULD BE A LITTLE UNDERDONE THIS
AFTERNOON IF CLOUD COVER IS NOT AS WIDESPREAD OR WE MIX A LITTLE
DEEPER. WILL NEED TO MONITOR AS WARMING OCCURS OVER THE NEXT FEW
HOURS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING.
* MEDIUM-HIGH IN BEST CHANCE FOR MVFR BEING THIS AFTERNOON BUT LOW
  THAT IT WILL OCCUR.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291412
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
912 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* RAIN ARRIVES 1530-16Z OR SO WITH BRIEF PERIOD OF SLEET OR SNOW
  POSSIBLE AT ONSET. ADDITIONAL SHOWERS POSSIBLE THROUGH EARLY
  AFTERNOON.
* MVFR CIGS POSSIBLE...MAINLY THIS AFTERNOON.
* CHANCE OF ANOTHER ROUND OF BRIEF RAIN SHOWERS
  TOWARD SUNSET.

MDB

//DISCUSSION...UPDATED 14Z...

BAND OF PRECIP IS NOW APPROACHING RFD AND WILL BE REACHING THE
CHICAGO AREA 1530-16Z OR SO. THE BAND HAS NARROWED QUITE A BIT
OVER THE LAST HOUR OR TWO SO DURATION OF THE MORE SOLID PRECIP
LOOKS TO BE 60-90 MIN...WITH SOME ADDITIONAL SCATTERED SHOWER
ACTIVITY TRAILING IT. BASED ON LATEST SURFACE TEMPS FZRA WILL
OCCUR FOR A TIME AT RFD ALONG WITH A MIX OF RAIN AND SLEET OR
SNOW...BUT TEMPS WILL WARM SO FZRA MAY BE SHORT LIVED.
ELSEWHERE...MAINLY RAIN LOOKS TO OCCUR BUT CANNOT RULE OUT SOME
SLEET OR POSSIBLY SOME SNOW AT ONSET.

WIND GUSTS ARE COMING UP SPORADICALLY AND GUSTS MAY BE TEMPERED
DURING PRECIP BUT 30-35 KT GUSTS STILL LOOK ON TRACK AND SHOULD
DEVELOP AHEAD OF THE PRECIP AS WELL. NOT MUCH IN THE WAY OF MVFR
CIGS UPSTREAM BUT EXPECT DEVELOPMENT THIS AFTERNOON AROUND 030.
AM A LITTLE CONCERNED THAT GUSTS COULD BE A LITTLE UNDERDONE THIS
AFTERNOON IF CLOUD COVER IS NOT AS WIDESPREAD OR WE MIX A LITTLE
DEEPER. WILL NEED TO MONITOR AS WARMING OCCURS OVER THE NEXT FEW
HOURS.

MDB

FROM 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING.
* MEDIUM-HIGH IN BEST CHANCE FOR MVFR BEING THIS AFTERNOON BUT LOW
  THAT IT WILL OCCUR.

MDB

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WEATHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...NEARSHORE WATERS UNTIL 7
     PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291155 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
655 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* ONE HOUR PERIOD OR SO OF SLEET OR SNOW POSSIBLE AT ONSET OF
  PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON WITH AT LEAST
  TEMPORARY MVFR CONDITIONS. CHANCE OF ANOTHER ROUND OF BRIEF
  RAIN SHOWERS TOWARD SUNSET.


//DISCUSSION...UPDATED 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.


//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 291155 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
655 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* ONE HOUR PERIOD OR SO OF SLEET OR SNOW POSSIBLE AT ONSET OF
  PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON WITH AT LEAST
  TEMPORARY MVFR CONDITIONS. CHANCE OF ANOTHER ROUND OF BRIEF
  RAIN SHOWERS TOWARD SUNSET.


//DISCUSSION...UPDATED 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.


//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291155 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
655 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* ONE HOUR PERIOD OR SO OF SLEET OR SNOW POSSIBLE AT ONSET OF
  PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON WITH AT LEAST
  TEMPORARY MVFR CONDITIONS. CHANCE OF ANOTHER ROUND OF BRIEF
  RAIN SHOWERS TOWARD SUNSET.


//DISCUSSION...UPDATED 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.


//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291155 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
655 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* ONE HOUR PERIOD OR SO OF SLEET OR SNOW POSSIBLE AT ONSET OF
  PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON WITH AT LEAST
  TEMPORARY MVFR CONDITIONS. CHANCE OF ANOTHER ROUND OF BRIEF
  RAIN SHOWERS TOWARD SUNSET.


//DISCUSSION...UPDATED 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.


//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 291155 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
655 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* ONE HOUR PERIOD OR SO OF SLEET OR SNOW POSSIBLE AT ONSET OF
  PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON WITH AT LEAST
  TEMPORARY MVFR CONDITIONS. CHANCE OF ANOTHER ROUND OF BRIEF
  RAIN SHOWERS TOWARD SUNSET.


//DISCUSSION...UPDATED 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.


//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 291155 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
655 AM CDT SUN MAR 29 2015

.UPDATE...
652 AM CDT

KEEPING A CLOSE EYE ON SURFACE TEMPERATURES AS AN AREA OF
PRECIPITATION ADVANCES EASTWARD ACROSS IA TOWARDS NORTHWEST
ILLINOIS. THERE HAVE BEEN MULTIPLE REPORTS OF FREEZING RAIN AND
ICING IN IOWA INTO SOUTHWEST WISCONSIN EARLY THIS MORNING. THESE
AREAS WERE MORE VULNERABLE FOR THIS PRECIP TYPE GIVEN IT BEGAN
BEFORE DAYBREAK ALLOWING TEMPERATURES NOT TO MODERATE. FOR OUR
FORECAST AREA...SURFACE TEMPERATURES ARE LIKELY TO WARM TO ABOVE
FREEZING BEFORE PRECIPITATION BEGINS NEAR ROCKFORD AND THE I-39
CORRIDOR FROM 9-10 AM...HOWEVER WET BULB COOLING WILL LIKELY
BRING THE TEMPERATURE DOWN A FEW DEGREES AT ONSET IF THE PRECIP IS
MODERATE ENOUGH. THIS COULD RESULT IN BRIEF FREEZING RAIN ACROSS
NORTH CENTRAL ILLINOIS...WHICH ALREADY DID HAVE A BRIEF CHANCE IN
THE FORECAST FOR...BUT DAY SHIFT MAY NEED TO ADDRESS WITH SEPARATE
STATEMENT.

MTF

&&

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILITY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* SOUTHERLY WINDS QUICKLY INCREASING WITH OCCASIONAL GUSTS AROUND
  35 KT FROM MID-MORNING THROUGH MID-AFTERNOON.
* ONE HOUR PERIOD OR SO OF SLEET OR SNOW POSSIBLE AT ONSET OF
  PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON WITH AT LEAST
  TEMPORARY MVFR CONDITIONS. CHANCE OF ANOTHER ROUND OF BRIEF
  RAIN SHOWERS TOWARD SUNSET.


//DISCUSSION...UPDATED 12Z...

SOUTHERLY WINDS ARE ALREADY INCREASING EARLY THIS MORNING WITH
GUSTS OVER 20 KT BEING NOTED ACROSS NORTHERN ILLINOIS...AND MUCH
STRONGER WINDS WITHIN A COUPLE THOUSAND FEET AGL ABLE TO BE MIXED
DOWN BY MID-MORNING. EXPECTING THE WIND DIRECTION TO VEER EVER SO
SLIGHTLY THIS MORNING...BUT STILL BE 190-210 WHEN GUSTS REACH
AROUND 35 KT AT TAF SITES BY MID-LATE MORNING.

A 3-4 HOUR PERIOD OF RAIN SHOWERS WILL MOVE FROM WEST-TO-EAST
ACROSS THE AREA FROM MID MORNING THROUGH EARLY AFTERNOON. A
TEMPORARY PERIOD OF MIXED PRECIPITATION IS LIKELY AT
ONSET...ESPECIALLY AT RFD...BUT EVEN BRIEFLY AT THE CHICAGOLAND
TAF SITES. THIS IS MOST FAVORED TO BE SLEET OR SNOW IF IT
OCCURS...THOUGH FOR RFD IT COULD ALSO BE FREEZING RAIN BASED ON
UPSTREAM OBSERVATIONS. WILL MONITOR TRENDS CLOSELY TO SEE IF THAT
NEEDS TO BE ADDED INTO THE RFD TAF. A WARMING ATMOSPHERE WILL
LIKELY ALLOW SHOWER ACTIVITY TO BE RAIN BY EARLY AFTERNOON.

AS A COLD FRONT APPROACHES...WINDS WILL TURN SOUTHWEST THIS
AFTERNOON AND THEN WESTERLY BEHIND THE FRONTAL PASSAGE WHICH WILL
BE NEAR OR SLIGHTLY AFTER SUNDOWN. WIND SPEEDS WILL ALSO DECREASE
SOME THOUGH STILL WITH SOME GUSTS DURING THE EVENING. IN
ADDITION...IT APPEARS THERE WILL BE SOME LIGHT RAIN SHOWERS ALONG
THIS FRONT AS WELL.


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN GUSTS REACHING 35
  KT AND TIMING.
* MEDIUM IN BRIEF SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.


//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...

MONDAY NIGHT...SLIGHT CHANCE OF RAIN AND MVFR. SOUTHWEST WINDS.
TUESDAY...VFR. NORTHEAST WINDS.
WEDNESDAY...CHANCE OF TSRA DURING THE NIGHT. SOUTH WINDS.
THURSDAY...CHANCE OF RAIN. WEST WINDS.
FRIDAY...CHANCE OF RAIN. NORTHEAST WINDS.
SATURDAY...VFR. WEST WINDS.

MTF

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KILX 291146
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
646 AM CDT Sun Mar 29 2015

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial fropa. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 646 AM CDT SUN MAR 29 2015

Rain showers will spread from west to east across central IL
starting around 12Z. Observations in the approaching system
showing VFR conditions, however there will likely be isolated MVFR
cigs/vsbys in heavier showers and perhaps an isolated thunderstorm
as it crosses the central IL terminals. Showers expected to begin
around 14Z at KPIA to around 16Z at KDEC/KCMI based on current
timing, consistent with HRRR model. Strong and gusty southerly
winds 20-25 kts with gusts 30-35 kts are expected as well. By late
afternoon a slight wind shift and decrease to SW 15-20g25 kts is
expected as showers taper off. Winds to continue shifting to NW
and decreasing overnight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton






000
FXUS63 KILX 291146
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
646 AM CDT Sun Mar 29 2015

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial fropa. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 646 AM CDT SUN MAR 29 2015

Rain showers will spread from west to east across central IL
starting around 12Z. Observations in the approaching system
showing VFR conditions, however there will likely be isolated MVFR
cigs/vsbys in heavier showers and perhaps an isolated thunderstorm
as it crosses the central IL terminals. Showers expected to begin
around 14Z at KPIA to around 16Z at KDEC/KCMI based on current
timing, consistent with HRRR model. Strong and gusty southerly
winds 20-25 kts with gusts 30-35 kts are expected as well. By late
afternoon a slight wind shift and decrease to SW 15-20g25 kts is
expected as showers taper off. Winds to continue shifting to NW
and decreasing overnight.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Onton






000
FXUS63 KLOT 290915
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
415 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS PRIOR TO 13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF SLEET OR SNOW POSSIBLE AT
  ONSET OF PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON SUNDAY WITH AT
  LEAST TEMPORARY MVFR CONDITIONS. CHANCE OF MORE BRIEF RAIN
  SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* MEDIUM IN SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR TO HOUR AND A HALF.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

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000
FXUS63 KLOT 290915
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
415 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS PRIOR TO 13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF SLEET OR SNOW POSSIBLE AT
  ONSET OF PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON SUNDAY WITH AT
  LEAST TEMPORARY MVFR CONDITIONS. CHANCE OF MORE BRIEF RAIN
  SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* MEDIUM IN SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR TO HOUR AND A HALF.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290915
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
415 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS PRIOR TO 13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF SLEET OR SNOW POSSIBLE AT
  ONSET OF PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON SUNDAY WITH AT
  LEAST TEMPORARY MVFR CONDITIONS. CHANCE OF MORE BRIEF RAIN
  SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* MEDIUM IN SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR TO HOUR AND A HALF.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290915
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
415 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS PRIOR TO 13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF SLEET OR SNOW POSSIBLE AT
  ONSET OF PRECIP LATE THIS MORNING...WHICH COULD BRING BRIEF IFR
  CONDITIONS.
* PERIOD OF RAIN SHOWERS THROUGH EARLY AFTERNOON SUNDAY WITH AT
  LEAST TEMPORARY MVFR CONDITIONS. CHANCE OF MORE BRIEF RAIN
  SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* MEDIUM IN SNOW/SLEET POTENTIAL AT BEGINNING OF
  PRECIPITATION...WHILE HIGH THAT IT WOULD LAST NO MORE THAN AN
  HOUR TO HOUR AND A HALF.
* HIGH IN PRECIP TIMING AND LOW-MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
358 AM CDT

AN ACTIVE MARINE WETAHER PERIOD WILL BE SEEN OVER LAKE MICHIGAN
THE NEXT 24 HOURS AS A QUICK-MOVING AND DEEPENING LOW PRESSURE
SYSTEM CRUISES EASTWARD ACROSS ONTARIO. THE RAPID MOVEMENT OF THIS
SYSTEM WILL DRIVE STRONG SOUTHERLY GALES TODAY...WITH EVEN STORM
FORCE WINDS EXPECTED ACROSS THE NORTH LATE THIS MORNING THROUGH
MID AFTERNOON. THE SOUTH HALF IS MOST FAVORED TO HAVE 40
KT...POSSIBLY AT TIMES 45 KT GALES. IN THE ILLINOIS AND INDIANA
NEARSHORE THE SOUTH GALES ARE EXPECTED BY MID MORNING AND WILL
LAST THROUGH THE DAY.

THE SYSTEM COLD FRONT WILL MOVE ACROSS THE LAKE FROM WEST TO EAST
VERY LATE TODAY INTO EARLY THIS EVENING. THIS WILL BRING A
DIMINISHING AND TURNING TO THE WEST-NORTHWEST OF THE WINDS.

A CLIPPER SYSTEM WILL DROP OVER THE LAKE ON MONDAY NIGHT. THERE
REMAINS UNCERTAINTY ON SPECIFIC TIMING OF THIS...BUT DO THINK A
PERIOD OF SMALL CRAFT ADVISORY CRITERIA WINDS ARE POSSIBLE ON BOTH
THE ILLINOIS AND INDIANA NEARSHORES.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290850
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
350 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290850
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
350 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290850
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
350 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290850
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
350 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

MONDAY THROUGH SATURDAY...

IN GENERAL A MILDER WEATHER PATTERN WILL BE IN PLACE ON MONDAY
THROUGH THURSDAY...THOUGH WITH SOME EXCEPTIONS IN THE DAY TO DAY
DETAILS. WHILE AREA WILL BE UNDER NORTHWEST FLOW AT THE MID AND
UPPER LEVELS BEHIND SUNDAY`S DEPARTING WAVE ON MONDAY...IT WILL BE
A DOWNSLOPING/WARM ADVECTIVE REGIME. THIS WILL ESPECIALLY BE THE
CASE DURING THE AFTERNOON AS WAA RAMPS UP IN ADVANCE OF A CLIPPER
SYSTEM DROPPING SOUTHEAST ACROSS THE UPPER MIDWEST. 850 MB TEMPS
WILL WARM TO THE MID SINGLE DIGITS CELSIUS AND 925 MB TEMPS TO
AROUND 10 CELSIUS BY EARLY EVENING...WHICH WILL YIELD HIGHS A BIT
ABOVE NORMAL IN THE MID 50S TO LOWER 60S. WILL NEED TO WATCH FOR A
LAKE BREEZE DURING THE LATE AFTERNOON AS GRADIENT WILL WEAKEN WITH
APPROACH OF CLIPPER.

SIMILAR TO PREVIOUS SHIFT...THERE IS DECENT AGREEMENT BETWEEN THE
GFS AND ECMWF ON TRACK OF THE SYSTEM TO THE NORTH OF THE CWA
MONDAY EVENING AND NIGHT. THIS KEEP THE BRUNT OF THE PRECIP TO OUR
NORTH...WITH JUST A GLANCING BLOW OF LOW POPS IN THE NORTHEAST
THIRD OF THE CWA. IN THE WAKE OF THIS SYSTEM...THE AIR MASS WILL
NOT UNDERGO MUCH COOLING...BUT GUIDANCE HAS COME INTO GOOD
AGREEMENT ON A FAVORABLE SETUP FOR A STRONG LAKE BREEZE TO PUSH
INLAND ON TUESDAY. HIGHS WILL REACH THE UPPER 50S TO MID 60S
INLAND AND LOWER TO MID 50S ALONG THE SHORE...FOLLOWED BY RAPID
COOLING INTO THE UPPER 30S TO LOWER 40S CLOSER TO THE LAKE DURING
THE MID TO LATE AFTERNOON.

IN THE MID TO LATE WEEK PERIOD...OPERATIONAL AND ENSEMBLE
GUIDANCE IS IN FAIR AGREEMENT IN THE SYNOPTIC PATTERN...HOWEVER
THERE ARE SIGNIFICANT TIMING DIFFERENCES. MIDLEVEL RIDGING WILL
FOCUS INTO THE MIDWEST ON WEDNESDAY...WITH GOOD SOUTHERLY LOW
LEVEL WARM AND MOIST ADVECTION (850 MB AND 925 MB TEMPS WARMING TO
10-15 CELSIUS BY LATE WEDS) RESULTING IN HIGHS AT LEAST IN THE
60S...AND THEN DEWPOINTS SURGING INTO THE 50S WEDNESDAY NIGHT. A
FAIRLY STRONG SURFACE LOW LOOKS TO RIDE ALONG THE CANADIAN
BORDER...WITH SHOWERS AND POSSIBLY THUNDERSTORMS DEVELOPING
ALONG/AHEAD OF TRAILING COLD FRONT GIVEN PRESENCE OF FAIRLY MOIST
AIRMASS. TIMING DISCREPANCY BETWEEN THE GFS/GEFS AND ECMWF IN THIS
FRONTAL SYSTEM IS FAIRLY SUBSTANTIAL...WITH GFS FAVORING MUCH
QUICKER WEDNESDAY NIGHT INTO THURSDAY TIMING AND ECMWF FAVORING
THURSDAY AFTERNOON INTO THURSDAY NIGHT. THIS WILL ULTIMATELY
PLACEMENT OF POPS AND HOW FAST COOLING TO NEAR OR BELOW NORMAL
LEVELS WILL ARRIVE LATER IN THE WEEK. OF NOTE...00Z ECMWF DID
ABANDON IDEA FROM PAST FEW RUNS OF SIGNIFICANT SYNOPTIC SYSTEM
OVER THE REGION ON FRIDAY...BUT PERIOD WILL NEED TO BE WATCHED AS
IT DID HAVE GOOD ENSEMBLE SUPPORT PRIOR TO 00 UTC CYCLE.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

TO BE ISSUED SHORTLY.

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

TO BE ISSUED SHORTLY.

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KLOT 290840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

TO BE ISSUED SHORTLY.

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO



000
FXUS63 KLOT 290840
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
340 AM CDT SUN MAR 29 2015

.SHORT TERM...
338 AM CDT

THROUGH TONIGHT...

A WELL-DEFINED UPPER CIRCULATION IS SEEN ON EARLY MORNING WATER
VAPOR IMAGERY MOVING SOUTHEASTWARD INTO SOUTHERN MN EARLY THIS
MORNING. THIS IS A QUICK-MOVING PACIFIC SYSTEM AND DESPITE MUCH OF
THE GULF BEING CUT OFF...DOES HAVE AN AXIS OF MOISTURE/SATURATION
WITHIN ITS WARM ADVECTION WING WITH SHOWERS FROM SOUTHERN MN ACROSS
IA. AS THIS ELEVATED WARM AND MOIST ADVECTION TRANSLATES OVER OUR
AREA THIS MORNING...IT WILL BE THE PRIMARY FOCUS FOR
PRECIPITATION...BRINGING A 3-4 HOUR PERIOD FROM WEST-TO-EAST.

RECENT LIGHTNING STRIKES AROUND 330 AM NEAR THE TWIN CITIES INDICATE
THE PRESENCE OF ELEVATED INSTABILITY AND RAP SOUNDINGS DO TRANSLATE
STEEP LAPSE RATES ABOVE 750MB INTO THE AREA WITHIN THIS ZONE OF
PRECIPITATION. WITH THIS INSTABILITY AND THE COMPACT AREA OF STRONG
QG FORCING OF THE UPPER WAVE...THERE MAY BE ENOUGH
INTENSITY/DYNAMICS OF PRECIPITATION AT FIRST FOR A BRIEF BUT
MODERATE INTENSITY MIX WITH SLEET OR SNOW. THIS CHANCE...WHICH HAS
INCREASED...LOOKS TO BE NORTH OF I-80 AND PRIOR TO NOON. HIGH-
RESOLUTION CONVECTIVE ALLOWING MODELS DO SHOW HIGHER SIMULATED
REFLECTIVITY AND HYDROMETEORS/PRECIP TYPE FAVORING THIS BRIEF
MIX...THOUGH THE SPECIFICS VARY FROM MODEL TO MODEL. AM NOT
EXPECTING THIS TO BE A BIG DEAL IN THE AREAS IT BRIEFLY OCCURS DUE
TO WARMING LOW-LEVEL TEMPS...THOUGH VISIBILTY COULD SHARPLY COME
DOWN FOR A NARROW WINDOW OF TIME.

RAIN SHOWERS SHOULD END FROM WEST TO EAST FOR MOST AREA BY EARLY-MID
AFTERNOON. THE COVERAGE OF SHOWERS BEHIND THE LEADING EDGE MAY NOT
BE AS WIDESPREAD AS THOUGHT EARLIER...BUT STILL FEEL A FEW HOUR
WINDOW OF CATEGORICAL POPS COVERS THIS SITUATION WELL. THE UPPER LOW
IN TANDEM WITH THE LOW-LEVEL COLD FRONT MAY HELP PROVIDE SOME
REGENERATING SHOWERS ACROSS FAR NORTHERN AND NORTHEAST ILLINOIS LATE
THIS AFTERNOON. MOST AREAS SHOULD FINISH UNDER 0.15 OF AN INCH.

THE OTHER CONCERN FOR TODAY IS THE STRONG WINDS. WHILE THE SURFACE
LOW WITH THIS SYSTEM IS WELL NORTH IN ONTARIO TODAY...THE RAPID
PROGRESSION OF THE SYSTEM WILL BRING PRESSURE FALLS OF 4-6MB PER
3HR MOVING DIRECTLY OVER THE AREA THIS MORNING. THIS ISALLOBARIC
COMPONENT AS WELL AS SOME SHALLOW BUT LIKELY REALIZED MIXING OF
STOUT GUSTS WILL BRING REGULAR 20-27 MPH WINDS WITH 35-40 MPH
GUSTS FROM MID-MORNING THROUGH EARLY AFTERNOON...BASICALLY IN
TANDEM WITH THE PRECIPITATION WINDOW. THIS IS A LITTLE BELOW WIND
ADVISORY CRITERIA BUT SOMETHING STILL TO NOTE SO WILL CONTINUE
SPS.

TEMPERATURES SHOULD CLIMB FROM SUNRISE THROUGH PRECIP START
TIME...AND THEN HOLD STEADY OR SLIGHTLY DIP IN THE FIRST 1-2 HOURS
DUE TO WET BULB COOLING. TEMPERATURES WILL WARM THIS AFTERNOON AS
DOWNSLOPE WARM ADVECTION IS DRAGGED THIS FAR EAST WITHIN THE PACIFIC
SYSTEM WARM SECTOR. HIGHS IN THE LOWER-MID 40S NORTH TO AROUND 50
TOWARD PONTIAC SHOULD BE REACHED LATE IN THE AFTERNOON/EARLY EVENING
JUST AHEAD OF THE COLD FRONT

MTF

&&

.LONG TERM...
338 AM CDT

TO BE ISSUED SHORTLY.

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* STRONG SOUTHERLY WINDS DEVELOPING SOON AFTER SUNRISE.
* CHANCE OF LLWS BETWEEN 09Z-13Z.
* ONE TO POSSIBLY TWO HOUR PERIOD OF GRAUPEL/SLEET OR SNOW
  POSSIBLE AT ONSET OF PRECIP LATE THIS MORNING.
* PERIOD OF RAIN THROUGH EARLY AFTERNOON SUNDAY WITH MVFR
  CONDITIONS. CHANCE OF MORE BRIEF RAIN SHOWERS TOWARD SUNSET.

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE WILL CONTINUE TO SCOOT AWAY FROM THE REGION WITH
SOUTHERLY WINDS INCREASING THROUGH DAYBREAK. AS ROBUST PRESSURE
FALLS ENVELOP THE REGION BY MID-MORNING...WIND SPEEDS AND GUSTS
WILL ESCALATE WITH GUSTS TO AROUND 35 KT FAVORED GIVEN STRONG
WINDS JUST OFF THE DECK. THE DIRECTION IS VERY LIKELY TO BE
SLIGHTLY WEST OF DUE SOUTH...BUT NOT BY MUCH.

PRECIPITATION IS EXPECTED TO FILL IN ACROSS IOWA DURING THE PRE-
SUNRISE HOURS AND MOVE INTO AND ACROSS NORTHERN ILLINOIS DURING
THE MID-LATE MORNING. THIS PRECIPITATION LOOKS TO LAST ABOUT 3-4
HOURS IN ANY ONE PLACE AND BE SOMEWHAT SHOWERY...SO FLUCTUATIONS
IN VISIBILITY AND EVEN CIGS ARE LIKELY. AT ONSET...OBSERVATIONAL
TRENDS AND MODEL GUIDANCE DO SUPPORT A MIX OF RAIN WITH ICE
PELLETS OR POSSIBLY EVEN SNOW. THIS COULD COME DOWN AT A FAIRLY
HIGH RATE...ALTHOUGH IS FAVORED TO LAST AS A MIX/FROZEN PRECIP
FOR ONLY A SHORT PERIOD OF TIME IF IT WERE TO COME TO FRUITION.
RAIN SHOWERS SHOULD CONTINUE INTO EARLY-MID AFTERNOON BEFORE AN
END...WITH POSSIBLY SOME BRIEF LIGHT SHOWERS AS THE COLD FRONT
MOVES INTO THE AREA NEAR/JUST PRIOR TO SUNSET. THIS FRONT WILL
SHIFT WINDS WEST WHICH WILL REMAIN GUSTY THROUGH THIS EVENING.

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH IN WIND DIRECTION TODAY. MEDIUM-HIGH IN SPEEDS.
* LOW-MEDIUM IN SNOW/SLEET/GRAUPEL POTENTIAL AT BEGINNING WITH
  HIGH THAT IT WOULD LAST NO MORE THAN TWO HOURS AT THE MOST.
* HIGH IN PRECIP TIMING AND MEDIUM IN VISIBILITY DURING.
* LOW IN TRUE LLWS EARLY THIS MORNING BUT HIGH IN 40-45 KT WINDS
  ABOVE 1000 FT.

//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...

MONDAY...PRIMARILY VFR.

TUESDAY...PRIMARILY VFR. LAKE BREEZE/NE WINDS DEVELOPING.

WEDNESDAY...PRIMARILY VFR. MODERATE-STRONG SOUTH WINDS POSSIBLE.

THURSDAY...CHANCE SHRA/TSRA IN MORNING...OTHERWISE VFR.

FRIDAY...LOW CONFIDENCE. RAIN/SUB-VFR CONDITIONS POSSIBLE.

MTF/IZZI

&&

.MARINE...
149 PM CDT

HIGH PRESSURE OVER THE LAKE HAS BEEN HELPING FOR QUIET CONDITIONS
WITH LIGHT WINDS...BUT EXPECT THIS TO CHANGE TONIGHT AND
ESPECIALLY SUNDAY MORNING AS THIS HIGH SHIFTS TO THE EAST AND A
TROUGH OF LOW PRESSURE APPROACHES FROM THE WEST. LIGHTER SOUTHERLY
WINDS THIS EVENING WILL INCREASE RAPIDLY OVER THE ENTIRE LAKE
OVERNIGHT WITH SOUTH/SOUTHWEST GALES TO 45 KT STILL EXPECTED.
HOWEVER SOUTHERLY FLOW IS APPEARING TO LIKELY APPROACH STORM FORCE
WINDS FOR A PERIOD SUNDAY MORNING THROUGH EARLY SUNDAY AFTERNOON.
WITH A HIGH LIKELIHOOD OF THIS OCCURRENCE...HAVE MAINTAINED THE
CURRENT GALE WARNING IN EFFECT FOR THE ENTIRE LAKE BUT TRANSITION
THE NORTHERN HALF TO A STORM WARNING BY 14Z AND CONTINUE IT
THROUGH 20Z. GALES MAY LINGER A COUPLE OF HOURS BEYOND THIS END
TIME BUT SHOULD BE DIMINISHING AS WELL. GALE WARNING FOR THE SOUTH
HALF REMAINS THE SOME...BUT WITH SOME POSSIBILITY THAT THE GALES
COULD CONTINUE A COUPLE OF HOURS BEYOND THE END TIME TOMORROW
EVENING.

MADE SOME MINOR CHANGES TO THE CURRENT HEADLINES FOR THE
NEARSHORE...PRIMARILY EXTENDING THE GALE WARNING TO 00Z AS WELL.
ALSO...WINDS SHOULD PICK UP PRIOR TO THE GALE WARNING FOR THE
INDIANA NEARSHORE AND SO DID ISSUE AN SCA TONIGHT INTO EARLY
SUNDAY.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM SUNDAY.

     GALE WARNING...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...10 AM
     SUNDAY TO 7 PM SUNDAY.

     GALE WARNING...LMZ777-LMZ779 UNTIL 7 PM SUNDAY.

&&

$$

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WWW.YOUTUBE.COM/NWSCHICAGO




000
FXUS63 KILX 290835
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
335 AM CDT Sun Mar 29 2015

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.


&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial fropa. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.


&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 1138 PM CDT SAT MAR 28 2015

VFR conditions will prevail through the entire 06z TAF period
despite passage of a frontal boundary Sunday evening. Clear skies
initially will give way to increasing high clouds toward dawn. As
the front approaches, a band of mid-level clouds and scattered
light showers will develop across the area Sunday morning.
NAM/Rapid Refresh timing still indicates showers arriving at KPIA
by 14z, then further east to KCMI by around 16z. Front will have
very little moisture to work with and strongest upper dynamics are
expected to stay well to the north across the Upper Midwest, so am
not expecting widespread rainfall. Will therefore maintain just
VCSH at the terminals into the afternoon. Light S/SE winds tonight
will increase markedly, with forecast soundings suggesting gusts
reaching the 25 to 30kt range by Sunday morning. Winds will
gradually veer to S/SW, then will decrease and become NW between
02z and 05z as the front passes.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Barnes







000
FXUS63 KILX 290835
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
335 AM CDT Sun Mar 29 2015

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.


&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial fropa. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.


&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 1138 PM CDT SAT MAR 28 2015

VFR conditions will prevail through the entire 06z TAF period
despite passage of a frontal boundary Sunday evening. Clear skies
initially will give way to increasing high clouds toward dawn. As
the front approaches, a band of mid-level clouds and scattered
light showers will develop across the area Sunday morning.
NAM/Rapid Refresh timing still indicates showers arriving at KPIA
by 14z, then further east to KCMI by around 16z. Front will have
very little moisture to work with and strongest upper dynamics are
expected to stay well to the north across the Upper Midwest, so am
not expecting widespread rainfall. Will therefore maintain just
VCSH at the terminals into the afternoon. Light S/SE winds tonight
will increase markedly, with forecast soundings suggesting gusts
reaching the 25 to 30kt range by Sunday morning. Winds will
gradually veer to S/SW, then will decrease and become NW between
02z and 05z as the front passes.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Barnes






000
FXUS63 KILX 290835
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
335 AM CDT Sun Mar 29 2015

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.


&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, particularly with the trend of the ECMWF to
the GFS...but the SuperBlend is a little slower to respond.
Onset of precipitation being delayed to later on Wednesday night is
cutting down the potential thunder activity, but still keeping the
mention in for the initial fropa. Still concerned that the temps for
Thursday may be too warm considering the proximity of the cloud
cover/rain potential.  Unless the clearing behind the boundary is
clean and quick early Thursday, the sun will have little chance to
rebound the sfc temps in the wake of the precip.


&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 1138 PM CDT SAT MAR 28 2015

VFR conditions will prevail through the entire 06z TAF period
despite passage of a frontal boundary Sunday evening. Clear skies
initially will give way to increasing high clouds toward dawn. As
the front approaches, a band of mid-level clouds and scattered
light showers will develop across the area Sunday morning.
NAM/Rapid Refresh timing still indicates showers arriving at KPIA
by 14z, then further east to KCMI by around 16z. Front will have
very little moisture to work with and strongest upper dynamics are
expected to stay well to the north across the Upper Midwest, so am
not expecting widespread rainfall. Will therefore maintain just
VCSH at the terminals into the afternoon. Light S/SE winds tonight
will increase markedly, with forecast soundings suggesting gusts
reaching the 25 to 30kt range by Sunday morning. Winds will
gradually veer to S/SW, then will decrease and become NW between
02z and 05z as the front passes.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Onton
LONG TERM...HJS
AVIATION...Barnes







000
FXUS63 KILX 290835
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
335 AM CDT Sun Mar 29 2015

.SHORT TERM...(Today)
ISSUED AT 334 AM CDT SUN MAR 29 2015

A shortwave moving into northwest Iowa early this morning will
continue moving rapidly ESE-ward through the morning arriving in
central IL later this morning. Precipitation with this feature
should intensify as it approaches as southerly return flow ahead of
it feeds more moisture into the region. Warm frontal boundary will
be followed closely by a cold frontal boundary, causing temperatures
to increase about 10 degrees from yesterday`s readings by late
afternoon, however cold air behind the system will not be very
pronounced. Precipitation amounts still look to be relatively light,
generally under one tenth of an inch. Southerly winds will be fairly
strong and gusty today, as model soundings showing winds into the
30-40 kt range in the near-surface mixed layer. Expect S-SW winds
15-25 mph with gusts 30-40 mph. Strongest gusts looking to be I-74
northward around noon. An outside chance for brief freezing rain
early in the morning in Knox and Stark counties, but looks like rain
will hold off until a few hours after sunrise, and temperatures
likely to rise above freezing just in time for start of
precipitation. Precipitation will be tapering off from west to east
late in the afternoon as the wave continues moving eastward.


&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 334 AM CDT SUN MAR 29 2015

Wave moving through the forecast area rather quickly today and the
precipitation should be coming to an end this evening.  Keeping the
slight chances in the east.  Brief dry pd expected for the first
couple days of the work week with daytime highs more seasonable into
the 60s with 850mb temps warming from 4-5C tomorrow...to 10-11C by
Wednesday.  Westerly/southwesterly winds helping to bring some of
the heat in from the western ridging.  However, the next system
will be moving on the Pac coast Mon night/Tuesday and making its way
towards the Midwest.  Agreement on this system is not happening yet
between the GFS and the ECMWF.  The GFS is quicker and cleaner with
the development of the sfc low and progression across the region.
00Z ECMWF is starting to look more like the GFS...bringing precip
Wed night through Thursday. GFS stalling the boundary just to the SE
along the Ohio River Valley and putting the southeastern CWA on the
edge of some weak waves moving along the boundary for Thurs night
and Fri. The ECMWF is still a messier solution with the QPF,
stalling the boundary further to the north and keeping the CWA wet
from Wed night through Friday. Trending the forecast to the GFS is
preferred at this point, par