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000
FXUS63 KILX 041544
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1044 AM CDT WED MAY 4 2016

.UPDATE...
Issued at 1035 AM CDT Wed May 4 2016

CU development today in mvfr category as 850mb shows strong cold
air advection over the region through today. Should then riase
cigs to low vfr in the afternoon. Will see sct shower development
in the east with the unstable airmass, with even a storm possible
as steep lapse rates. Showers and clouds should disspiate
overnight with drop off of afternoon heating. Gusy winds today in
srong gradient and the cold air advection behind the front that
moved through last night. Some drop off in winds overnight.

&&

.SHORT TERM...(Today)
ISSUED AT 320 AM CDT Wed May 4 2016

A band of showers and a few thunderstorms is diving across central
and southeast Illinois early this morning. This convection lies just
ahead of a strong cold front, that is driven by a vigorous upper
wave diving into the Midwest. The rapid movement of this
front/precipitation will have the rainfall completely out of the
forecast area by mid-morning. It will be noticeable cooler across
the region today behind the front, with many areas only seeing high
temperatures in the 50s. Northerly post-frontal winds gusting to 30
mph at times will also make it feel cooler. Peak afternoon heating
and very chilly air aloft will combine to produce steep lapse rates
later today. This should allow a few showers or a thunderstorm to
pop this afternoon. However, coverage should not be significant and
have limited Slight Chance afternoon PoPs to roughly the eastern
half of the forecast area.

.LONG TERM...(Tonight through Tuesday)
ISSUED AT 320 AM CDT Wed May 4 2016

Upper ridging currently along the Rockies will be edging eastward
the next couple days, but pattern overall will be rather blocky,
with closed lows on either side of it. No real breakdown expected
until this weekend, when an upper wave will drop southeast from
Hudson Bay and finally boot the eastern low out of the way. However,
the western one will remain in the picture until Monday, with a
surface boundary extending eastward into the Midwest.

Longer range models are in decent agreement with pushing the front
through the area by Saturday evening, with scattered showers and
thunderstorms during the day and evening hours, before diminishing.
After that, the boundary becomes parallel to the upper flow between
what`s left of the ridge and shortwaves rotating through the Great
Lakes region. The GFS hangs onto this until late Monday night before
the front and associated rain chances lift back north. Meanwhile,
the ECMWF is much more aggressive in pushing it back beginning
Sunday evening as the lingering ridge axis slides overhead. Leaned
more toward the latter solution, although not quite as wet, and have
chance PoP`s over most of the forecast area Sunday night and Monday.
With the remnants of the western low only into the central Plains by
Tuesday, rain chances will be steadily increasing with time early
next week.

A warming trend will commence on Thursday, with highs mostly in the
mid 60s. As the thermal ridge builds east late in the week, a couple
days are expected with temperatures reaching near 80 degrees, before
the front pushes through. However, with the main troughing remaining
near the Great Lakes, temperatures behind the front should not be
especially cooler.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 635 AM CDT Wed May 4 2016

Predominantly VFR conditions expected across the central Illinois
terminals today, although a few patches of stratus/fog will be in
the area for the next hour or two. Low end VFR CIGS will develop
around midday and possibly result in a few showers, especially
toward the Indiana border. Gusty northerly winds are expected to
develop shortly, and linger until this evening.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Goetsch
SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...BAK




000
FXUS63 KILX 041544
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1044 AM CDT WED MAY 4 2016

.UPDATE...
Issued at 1035 AM CDT Wed May 4 2016

CU development today in mvfr category as 850mb shows strong cold
air advection over the region through today. Should then riase
cigs to low vfr in the afternoon. Will see sct shower development
in the east with the unstable airmass, with even a storm possible
as steep lapse rates. Showers and clouds should disspiate
overnight with drop off of afternoon heating. Gusy winds today in
srong gradient and the cold air advection behind the front that
moved through last night. Some drop off in winds overnight.

&&

.SHORT TERM...(Today)
ISSUED AT 320 AM CDT Wed May 4 2016

A band of showers and a few thunderstorms is diving across central
and southeast Illinois early this morning. This convection lies just
ahead of a strong cold front, that is driven by a vigorous upper
wave diving into the Midwest. The rapid movement of this
front/precipitation will have the rainfall completely out of the
forecast area by mid-morning. It will be noticeable cooler across
the region today behind the front, with many areas only seeing high
temperatures in the 50s. Northerly post-frontal winds gusting to 30
mph at times will also make it feel cooler. Peak afternoon heating
and very chilly air aloft will combine to produce steep lapse rates
later today. This should allow a few showers or a thunderstorm to
pop this afternoon. However, coverage should not be significant and
have limited Slight Chance afternoon PoPs to roughly the eastern
half of the forecast area.

.LONG TERM...(Tonight through Tuesday)
ISSUED AT 320 AM CDT Wed May 4 2016

Upper ridging currently along the Rockies will be edging eastward
the next couple days, but pattern overall will be rather blocky,
with closed lows on either side of it. No real breakdown expected
until this weekend, when an upper wave will drop southeast from
Hudson Bay and finally boot the eastern low out of the way. However,
the western one will remain in the picture until Monday, with a
surface boundary extending eastward into the Midwest.

Longer range models are in decent agreement with pushing the front
through the area by Saturday evening, with scattered showers and
thunderstorms during the day and evening hours, before diminishing.
After that, the boundary becomes parallel to the upper flow between
what`s left of the ridge and shortwaves rotating through the Great
Lakes region. The GFS hangs onto this until late Monday night before
the front and associated rain chances lift back north. Meanwhile,
the ECMWF is much more aggressive in pushing it back beginning
Sunday evening as the lingering ridge axis slides overhead. Leaned
more toward the latter solution, although not quite as wet, and have
chance PoP`s over most of the forecast area Sunday night and Monday.
With the remnants of the western low only into the central Plains by
Tuesday, rain chances will be steadily increasing with time early
next week.

A warming trend will commence on Thursday, with highs mostly in the
mid 60s. As the thermal ridge builds east late in the week, a couple
days are expected with temperatures reaching near 80 degrees, before
the front pushes through. However, with the main troughing remaining
near the Great Lakes, temperatures behind the front should not be
especially cooler.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 635 AM CDT Wed May 4 2016

Predominantly VFR conditions expected across the central Illinois
terminals today, although a few patches of stratus/fog will be in
the area for the next hour or two. Low end VFR CIGS will develop
around midday and possibly result in a few showers, especially
toward the Indiana border. Gusty northerly winds are expected to
develop shortly, and linger until this evening.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Goetsch
SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...BAK




000
FXUS63 KILX 041142
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
642 AM CDT WED MAY 4 2016

.SHORT TERM...(Today)
ISSUED AT 320 AM CDT Wed May 4 2016

A band of showers and a few thunderstorms is diving across central
and southeast Illinois early this morning. This convection lies just
ahead of a strong cold front, that is driven by a vigorous upper
wave diving into the Midwest. The rapid movement of this
front/precipitation will have the rainfall completely out of the
forecast area by mid-morning. It will be noticeable cooler across
the region today behind the front, with many areas only seeing high
temperatures in the 50s. Northerly post-frontal winds gusting to 30
mph at times will also make it feel cooler. Peak afternoon heating
and very chilly air aloft will combine to produce steep lapse rates
later today. This should allow a few showers or a thunderstorm to
pop this afternoon. However, coverage should not be significant and
have limited Slight Chance afternoon PoPs to roughly the eastern
half of the forecast area.

.LONG TERM...(Tonight through Tuesday)
ISSUED AT 320 AM CDT Wed May 4 2016

Upper ridging currently along the Rockies will be edging eastward
the next couple days, but pattern overall will be rather blocky,
with closed lows on either side of it. No real breakdown expected
until this weekend, when an upper wave will drop southeast from
Hudson Bay and finally boot the eastern low out of the way. However,
the western one will remain in the picture until Monday, with a
surface boundary extending eastward into the Midwest.

Longer range models are in decent agreement with pushing the front
through the area by Saturday evening, with scattered showers and
thunderstorms during the day and evening hours, before diminishing.
After that, the boundary becomes parallel to the upper flow between
what`s left of the ridge and shortwaves rotating through the Great
Lakes region. The GFS hangs onto this until late Monday night before
the front and associated rain chances lift back north. Meanwhile,
the ECMWF is much more aggressive in pushing it back beginning
Sunday evening as the lingering ridge axis slides overhead. Leaned
more toward the latter solution, although not quite as wet, and have
chance PoP`s over most of the forecast area Sunday night and Monday.
With the remnants of the western low only into the central Plains by
Tuesday, rain chances will be steadily increasing with time early
next week.

A warming trend will commence on Thursday, with highs mostly in the
mid 60s. As the thermal ridge builds east late in the week, a couple
days are expected with temperatures reaching near 80 degrees, before
the front pushes through. However, with the main troughing remaining
near the Great Lakes, temperatures behind the front should not be
especially cooler.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 635 AM CDT Wed May 4 2016

Predominantly VFR conditions expected across the central Illinois
terminals today, although a few patches of stratus/fog will be in
the area for the next hour or two. Low end VFR CIGS will develop
around midday and possibly result in a few showers, especially
toward the Indiana border. Gusty northerly winds are expected to
develop shortly, and linger until this evening.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...BAK




000
FXUS63 KILX 041142
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
642 AM CDT WED MAY 4 2016

.SHORT TERM...(Today)
ISSUED AT 320 AM CDT Wed May 4 2016

A band of showers and a few thunderstorms is diving across central
and southeast Illinois early this morning. This convection lies just
ahead of a strong cold front, that is driven by a vigorous upper
wave diving into the Midwest. The rapid movement of this
front/precipitation will have the rainfall completely out of the
forecast area by mid-morning. It will be noticeable cooler across
the region today behind the front, with many areas only seeing high
temperatures in the 50s. Northerly post-frontal winds gusting to 30
mph at times will also make it feel cooler. Peak afternoon heating
and very chilly air aloft will combine to produce steep lapse rates
later today. This should allow a few showers or a thunderstorm to
pop this afternoon. However, coverage should not be significant and
have limited Slight Chance afternoon PoPs to roughly the eastern
half of the forecast area.

.LONG TERM...(Tonight through Tuesday)
ISSUED AT 320 AM CDT Wed May 4 2016

Upper ridging currently along the Rockies will be edging eastward
the next couple days, but pattern overall will be rather blocky,
with closed lows on either side of it. No real breakdown expected
until this weekend, when an upper wave will drop southeast from
Hudson Bay and finally boot the eastern low out of the way. However,
the western one will remain in the picture until Monday, with a
surface boundary extending eastward into the Midwest.

Longer range models are in decent agreement with pushing the front
through the area by Saturday evening, with scattered showers and
thunderstorms during the day and evening hours, before diminishing.
After that, the boundary becomes parallel to the upper flow between
what`s left of the ridge and shortwaves rotating through the Great
Lakes region. The GFS hangs onto this until late Monday night before
the front and associated rain chances lift back north. Meanwhile,
the ECMWF is much more aggressive in pushing it back beginning
Sunday evening as the lingering ridge axis slides overhead. Leaned
more toward the latter solution, although not quite as wet, and have
chance PoP`s over most of the forecast area Sunday night and Monday.
With the remnants of the western low only into the central Plains by
Tuesday, rain chances will be steadily increasing with time early
next week.

A warming trend will commence on Thursday, with highs mostly in the
mid 60s. As the thermal ridge builds east late in the week, a couple
days are expected with temperatures reaching near 80 degrees, before
the front pushes through. However, with the main troughing remaining
near the Great Lakes, temperatures behind the front should not be
especially cooler.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 635 AM CDT Wed May 4 2016

Predominantly VFR conditions expected across the central Illinois
terminals today, although a few patches of stratus/fog will be in
the area for the next hour or two. Low end VFR CIGS will develop
around midday and possibly result in a few showers, especially
toward the Indiana border. Gusty northerly winds are expected to
develop shortly, and linger until this evening.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...BAK



  [top]

000
FXUS63 KLOT 041130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
630 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

MVFR CONDITIONS THIS MORNING AND GUSTY NORTHERLY WINDS THROUGH THE
DAY MAKE UP THE MAKE FORECAST CONCERNS FOR TODAY. EARLY THIS
MORNING...A COLD FRONT HAS DROPPED SOUTH OF THE TERMINALS WITH
SOME LINGERING LIGHT SHOWERS WHICH SHOULD CLEAR THE TERMINALS BY
AROUND 12Z. WINDS HAVE QUICKLY RAMPED UP THIS MORNING...IN PART
DUE TO CONVECTIVE OUTFLOW FROM THE SHOWERS. WITH THAT IN MIND DO
STILL ANTICIPATE WINDS TO SETTLE SOME AS THE SHOWERS DEPART WITH
PREVAILING WIND DIRECTION BETWEEN 350-010 THROUGH MUCH OF THE
DAY...AND GUSTS INTO THE LOW TO MID 20 KT RANGE. MVFR CIGS THIS
MORNING ARE EXPECTED TO RISE WITH DAYTIME HEATING...AND EXPECT VFR
CONDITIONS TO RETURN BY AROUND MIDDAY...EXCEPT AT GYY WHERE LOWER
CONDITIONS AND STRONGER WINDS WILL LIKELY PERSIST DOWN FETCH OF
LAKE MICHIGAN. SCATTERED LIGHT SHOWERS AND SPRINKLES ARE POSSIBLE
THIS AFTERNOON...THOUGH COVERAGE SHOULD BE TOO LOW TO INCLUDE IN
THE TAFS AT THIS DISTANCE.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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 041130
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
630 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

MVFR CONDITIONS THIS MORNING AND GUSTY NORTHERLY WINDS THROUGH THE
DAY MAKE UP THE MAKE FORECAST CONCERNS FOR TODAY. EARLY THIS
MORNING...A COLD FRONT HAS DROPPED SOUTH OF THE TERMINALS WITH
SOME LINGERING LIGHT SHOWERS WHICH SHOULD CLEAR THE TERMINALS BY
AROUND 12Z. WINDS HAVE QUICKLY RAMPED UP THIS MORNING...IN PART
DUE TO CONVECTIVE OUTFLOW FROM THE SHOWERS. WITH THAT IN MIND DO
STILL ANTICIPATE WINDS TO SETTLE SOME AS THE SHOWERS DEPART WITH
PREVAILING WIND DIRECTION BETWEEN 350-010 THROUGH MUCH OF THE
DAY...AND GUSTS INTO THE LOW TO MID 20 KT RANGE. MVFR CIGS THIS
MORNING ARE EXPECTED TO RISE WITH DAYTIME HEATING...AND EXPECT VFR
CONDITIONS TO RETURN BY AROUND MIDDAY...EXCEPT AT GYY WHERE LOWER
CONDITIONS AND STRONGER WINDS WILL LIKELY PERSIST DOWN FETCH OF
LAKE MICHIGAN. SCATTERED LIGHT SHOWERS AND SPRINKLES ARE POSSIBLE
THIS AFTERNOON...THOUGH COVERAGE SHOULD BE TOO LOW TO INCLUDE IN
THE TAFS AT THIS DISTANCE.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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 040911
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
411 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
UPDATE FOR 09Z TAFS...
STABLE CONDITIONS BEHIND THE DEPARTING LINE OF SHOWERS HAS SLOWED
THE ARRIVAL OF GUSTIER NORTHERLY WINDS TO THE TERMINALS THIS
MORNING...HOWEVER ANTICIPATE WINDS TO VEER BACK TO THE NORTH AND
INCREASE OVER THE NEXT HOUR OR TWO. MEANWHILE...MVFR/IFR CIGS ARE
NOW NOTED IN OBS OVER SOUTHEAST WI AND INTO FAR NE IL AND ALSO
EXPECT THOSE TO OVERSPREAD THE CHICAGO AREA TERMINALS OVER THE
NEXT COUPLE HOURS...THEN GRADUALLY LIFT DIURNALLY AFTER DAYBREAK.
CONFIDENCE IN HOW FAR WEST THESE WILL SPREAD IS LOW HOWEVER...SO
HAVE BACKED OFF ON LOWEST CIGS AT RFD...AND MAY HAVE TO FOLLOW
SUIT AT DPA.

PREVIOUS DISCUSSION FOR THE 06Z TAFS...
LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS BY
AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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 040911
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
411 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONIC FLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
UPDATE FOR 09Z TAFS...
STABLE CONDITIONS BEHIND THE DEPARTING LINE OF SHOWERS HAS SLOWED
THE ARRIVAL OF GUSTIER NORTHERLY WINDS TO THE TERMINALS THIS
MORNING...HOWEVER ANTICIPATE WINDS TO VEER BACK TO THE NORTH AND
INCREASE OVER THE NEXT HOUR OR TWO. MEANWHILE...MVFR/IFR CIGS ARE
NOW NOTED IN OBS OVER SOUTHEAST WI AND INTO FAR NE IL AND ALSO
EXPECT THOSE TO OVERSPREAD THE CHICAGO AREA TERMINALS OVER THE
NEXT COUPLE HOURS...THEN GRADUALLY LIFT DIURNALLY AFTER DAYBREAK.
CONFIDENCE IN HOW FAR WEST THESE WILL SPREAD IS LOW HOWEVER...SO
HAVE BACKED OFF ON LOWEST CIGS AT RFD...AND MAY HAVE TO FOLLOW
SUIT AT DPA.

PREVIOUS DISCUSSION FOR THE 06Z TAFS...
LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS BY
AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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 040828
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
328 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONICFLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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000
FXUS63 KLOT 040828
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
328 AM CDT WED MAY 4 2016

.SHORT TERM...
326 AM CDT

TODAY THROUGH THURSDAY NIGHT...

NEAR TERM FOCUS IS ON BLUSTERY...COOLER AND SHOWERY WEATHER
CONDITIONS TODAY.

A STRONG MID-LEVEL SHORT WAVE WAS DIGGING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING...AND WILL CONTINUE TO CARVE OUT A CLOSED
UPPER LOW OVER THE MIDWEST AND OHIO VALLEY THROUGH THIS EVENING AS
ADDITIONAL SHORT WAVE ENERGY WRAPS IN TO THE DEEPENING TROUGH FROM
THE NORTH. COINCIDENT WITH THE INITIAL VORT IS THE PASSAGE OF A
STRONG COLD FRONT...WHICH WILL BRING SHARPLY COOLER TEMPERATURES
AS WELL AS BLUSTERY NORTH WINDS TO THE REGION TODAY. CYCLONICFLOW
AND COOL AIR ALOFT WILL SUPPORT WEAK INSTABILITY AND RESULT IN
EXTENSIVE STRATOCU AND SCATTERED SHOWERS FROM LATER THIS MORNING
THROUGH THIS AFTERNOON. STEEPEST LAPSE RATES WILL LIKELY BE OVER
THE ILLINOIS PORTION OF THE FORECAST AREA...WHILE NORTH FLOW OFF
COOL LAKE MICHIGAN WATERS WILL KEEP THE BOUNDARY LAYER MORE STABLE
ACROSS NORTHWEST INDIANA. BASED ON MODEL LOW LEVEL THERMAL
FIELDS...TEMPS MAY STRUGGLE TO BREAK THE 50 DEGREE MARK NEAR THE
LAKE IN NORTHWEST INDIANA...WHILE APPROACHING THE 60 DEGREE MARK
ACROSS THE WESTERN PARTS OF THE CWA. NORTH WIND GUSTS OF 25 TO 30
MPH WILL MAKE IT FEEL EVEN CHILLIER. A FEW SHOWERS WILL LIKELY
LINGER INTO THIS EVENING ESPECIALLY ACROSS THE SOUTHEASTERN CWA
WITH SECONDARY VORT PASSING OVERHEAD...BEFORE COMBINATION OF DRIER
AIR...SUBSIDENCE AND LOSS OF WEAK DIURNAL COMPONENT SHUTS OFF
PRECIP POTENTIAL. UNSEASONABLY CHILLY CONDITIONS CONTINUE TONIGHT
WITH READINGS EXPECTED TO FALL INTO THE MID-UPPER 30S ACROSS MANY
NORTHERN IL LOCATIONS. NORTH WINDS WILL LIKELY STAY STRONG ENOUGH
OVERNIGHT TO PREVENT ANY APPRECIABLE FROST THREAT.

STRONG HEIGHT RISES DEVELOP LATE TONIGHT AND THURSDAY AS THE DEEP
EASTERN TROUGH DRIFTS AWAY FROM THE REGION...AND UPPER RIDGING
OVER THE CENTRAL CONUS BEGINS TO SPREAD IN FROM THE WEST. SURFACE
HIGH PRESSURE RIDGE SLOWLY EDGES INTO THE FORECAST AREA LATER IN
THE DAY. DECREASING NORTH WINDS WILL LIKELY RESULT IN A
NORTHEASTERLY LAKE BREEZE DEVELOPING BY THURSDAY
AFTERNOON...THOUGH MOSTLY SUNNY SKIES AND MODERATING TEMPS WILL
MAKE FOR A BETTER DAY. TEMPS LOOK TO RECOVER INTO THE MID-UPPER
50S AWAY FROM THE IMMEDIATE LAKE SHORE IN THE EAST AND INTO THE
MID 60S FARTHER WEST ACROSS NORTH CENTRAL IL. TEMPS WILL COOL
QUICKLY THURSDAY EVENING WITH LIGHT WINDS AND MAINLY CLEAR
SKIES...THOUGH DEVELOPMENT OF WARM ADVECTION ALOFT WILL HELP KEEP
OVERNIGHT LOWS IN CHECK IN THE 40S.

RATZER

&&

.LONG TERM...
326 AM CDT

FRIDAY THROUGH TUESDAY...

FRIDAY WILL BRING A BIG WARM-UP TO THE REGION AS THE UPPER RIDGE
BUILDS IN FROM THE WEST. WEST-SOUTHWEST SURFACE WINDS DEVELOP AND
STRENGTHEN JUST ENOUGH TO PREVENT MUCH INLAND PUSH TO THE LAKE
BREEZE BOUNDARY OVER NORTHEAST ILLINOIS FRIDAY AFTERNOON...WITH
MOSTLY SUNNY SKIES HELPING TO WARM TEMPS NEARLY 20 DEGREES OVER
THURSDAYS NUMBERS. LOW LEVEL THERMAL PROGS SUPPORT HIGHS FROM THE
MID-UPPER 70S EAST TO THE LOW-MID 80S FARTHER WEST.

UNFORTUNATELY...GUIDANCE REMAINS IN GOOD AGREEMENT IN BRINGING A
FAIRLY STRONG SHORT WAVE ACROSS THE TOP OF THE RIDGE OVER THE
NORTHERN LAKES FRIDAY NIGHT THROUGH SATURDAY...WITH A SURFACE COLD
FRONT SAGGING INTO THE AREA EARLY SATURDAY. WINDS SHIFT NORTH-
NORTHEAST BEHIND THE FRONT WHICH WILL BRING AN END TO THE BRIEF
WARM-UP FOR AREAS NEAR LAKE MICHIGAN. TEMPS MAY REACH THE 60S
BEFORE THE COOL ADVECTION PUSH BEHIND THE BACK DOOR FRONT
CAUSES TEMPS TO FALL DURING THE AFTERNOON NEAR THE LAKE. EVEN WELL
INLAND TEMPS WILL LIKELY FALL FROM THE 70S INTO THE 60S BY LATE
AFTERNOON AS NORTH-NORTHEAST WINDS PICK UP. AS MODELS HAVE
CONTINUED TO TREND EARLIER WITH THE COLD FRONT SATURDAY...THE
GREATEST CHANCE OF THUNDERSTORMS WILL LARGELY BE ACROSS THE
SOUTHERN HALF OF THE CWA. THE FRONT THEN SAGS ALL THE WAY TO THE
OHIO VALLEY SATURDAY NIGHT... FOCUSING PRECIP POTENTIAL MAINLY
SOUTH OF THE CWA UNTIL THE FRONT RETURNS AS A WARM FRONT MONDAY-
TUESDAY. WHILE IT WILL BE COOLER WITH THE FRONT TO OUR SOUTH
THROUGH THE END OF THE EXTENDED PERIOD...IT WILL BE MILDER THAN
THE VERY NEAR TERM. TEMPS LOOK TO RANGE FROM THE 50S/60S RIGHT
ALONG THE LAKE TO THE 70S OVER SOUTHERN AND WESTERN PARTS OF THE
FORECAST AREA.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KILX 040820
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
320 AM CDT WED MAY 4 2016

.SHORT TERM...(Today)
ISSUED AT 320 AM CDT Wed May 4 2016

A band of showers and a few thunderstorms is diving across central
and southeast Illinois early this morning. This convection lies just
ahead of a strong cold front, that is driven by a vigorous upper
wave diving into the Midwest. The rapid movement of this
front/precipitation will have the rainfall completely out of the
forecast area by mid-morning. It will be noticeable cooler across
the region today behind the front, with many areas only seeing high
temperatures in the 50s. Northerly post-frontal winds gusting to 30
mph at times will also make it feel cooler. Peak afternoon heating
and very chilly air aloft will combine to produce steep lapse rates
later today. This should allow a few showers or a thunderstorm to
pop this afternoon. However, coverage should not be significant and
have limited Slight Chance afternoon PoPs to roughly the eastern
half of the forecast area.

&&

.LONG TERM...(Tonight through Tuesday)
ISSUED AT 320 AM CDT Wed May 4 2016

Upper ridging currently along the Rockies will be edging eastward
the next couple days, but pattern overall will be rather blocky,
with closed lows on either side of it. No real breakdown expected
until this weekend, when an upper wave will drop southeast from
Hudson Bay and finally boot the eastern low out of the way. However,
the western one will remain in the picture until Monday, with a
surface boundary extending eastward into the Midwest.

Longer range models are in decent agreement with pushing the front
through the area by Saturday evening, with scattered showers and
thunderstorms during the day and evening hours, before diminishing.
After that, the boundary becomes parallel to the upper flow between
what`s left of the ridge and shortwaves rotating through the Great
Lakes region. The GFS hangs onto this until late Monday night before
the front and associated rain chances lift back north. Meanwhile,
the ECMWF is much more aggressive in pushing it back beginning
Sunday evening as the lingering ridge axis slides overhead. Leaned
more toward the latter solution, although not quite as wet, and have
chance PoP`s over most of the forecast area Sunday night and Monday.
With the remnants of the western low only into the central Plains by
Tuesday, rain chances will be steadily increasing with time early
next week.

A warming trend will commence on Thursday, with highs mostly in the
mid 60s. As the thermal ridge builds east late in the week, a couple
days are expected with temperatures reaching near 80 degrees, before
the front pushes through. However, with the main troughing remaining
near the Great Lakes, temperatures behind the front should not be
especially cooler.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1203 PM CDT Wed May 4 2016

VFR conditions will prevail at all TAF sites next 24hrs. Sfc front
will drop quickly through the CWA early this morning and radar
indicates thunderstorms along with showers. So have changed to
VCTS with TEMPO group at all sites for thunderstorms. Once the
pcpn moves south skies will scatter out some. However, with the
500mb trough, additional clouds and VCSH will be seen at
DEC/CMI/BMI in the afternoon. Skies will scatter out and clear
after sunset at all sites. Winds will become northwesterly just
behind the front and then northerly during the day and into the
afternoon. Wind speeds will increase and gust to 23-26kts at all
sites. Winds speeds will decrease in the evening.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...Auten




000
FXUS63 KLOT 040747
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
247 AM CDT WED MAY 4 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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 040747
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
247 AM CDT WED MAY 4 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
244 AM CDT

A COLD FRONT IS SWEEPING SOUTH ACROSS LAKE MICHIGAN EARLY THIS
MORNING WITH NORTHERLY WINDS INCREASING IN ITS WAKE. THE GRADIENT
WILL BE STRONGEST TODAY AND TONIGHT ACROSS THE SOUTH HALF OF
LAKE MICHIGAN SUPPORTING GALE FORCE WIND GUSTS THROUGH THAT TIME
FRAME. A GALE WARNING IS IN EFFECT FOR THE OPEN WATERS OF LAKE
MICHIGAN SOUTH OF MANISTEE...AND FOR THE INDIANA/ILLINOIS
NEARSHORE WATERS. HIGH PRESSURE WILL BEGIN BUILD ACROSS NORTHERN
LAKE MICHIGAN THURSDAY ALLOWING WINDS TO DIMINISH. THE HIGH WILL
MOVE SOUTH OF THE LAKE LATE THURSDAY INTO FRIDAY AS LOW PRESSURE
MOVES ACROSS MANITOBA INTO ONTARIO WITH A FRESH SOUTHWESTERLY
BREEZE DEVELOPING...THEN A TRAILING COLD FRONT WILL MOVE SOUTH
ACROSS LAKE MICHIGAN ON SATURDAY WITH NORTHERLY WINDS TO 30 KT
EXPECTED BEHIND THE FRONT.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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 040513
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1213 AM CDT WED MAY 4 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 06Z TAFS...

LINE OF SHOWERS AND THUNDERSTORMS IS DROPPING INTO NORTHERN
ILLINOIS LATE THIS EVENING AND SHOULD BE CLEAR OF THE TERMINALS
BY AROUND 7-8Z. MOST LIGHTNING ACTIVITY THUS FAR HAS BEEN FOCUSED
OVER NORTH CENTRAL ILLINOIS WITH ONLY ISOLATED ACTIVITY FARTHER
EAST...SO WILL ONLY BRING THUNDERSTORMS ON STATION AT RFD...AND
WILL JUST KEEP A VCTS MENTION FOR THE CHICAGO AREA TERMINALS. A
GUST FRONT HAS SURGED OUT AHEAD OF THE MAIN LINE OF SHOWERS AND
WILL BRING STRONG GUSTY NORTHERLY WINDS...THEN BEHIND THE INITIAL
LINE OF SHOWERS AND THUNDERSTORMS THERE MAY BE SOME VARIABILITY OR
LIGHTER WINDS BEFORE THE SYNOPTIC FRONT PUSHES THROUGH A FEW HOURS
LATER WITH GUSTY WINDS PICKING UP AGAIN OUT OF THE NORTH.
CONFIDENCE IS HIGH IN THE GUSTY NORTH WINDS WITH THE GUST
FRONT...HOWEVER CONFIDENCE IN WIND DIRECTION IS LOW FOR THE FEW
HOURS FOLLOWING THE LINE OF PRECIP. HAVE BACKED OFF ON THE IFR
CIGS BEHIND THE FRONT THIS EVENING AS THEY ARE NOT SHOWING UP YET
IN UPSTREAM OBS AND MODELS SEEM TO HAVE BETTER CONSENSUS ON MVFR
OR BETTER CONDITIONS. STRONG GUSTY NORTHERLY WINDS ARE EXPECTED TO
CONTINUE THROUGH THE DAY WEDNESDAY WITH SOME SCATTERED DIURNAL
LIGHT SHOWERS POSSIBLE MAINLY DURING THE AFTERNOON.

BMD

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...ILLINOIS NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779 UNTIL 4 AM
     THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KILX 040503
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1203 AM CDT WED MAY 4 2016

.UPDATE...
Issued at 903 PM CDT Tue May 3 2016

Will be taking a look at the pop/wx grids to clean them up a bit.
Otherwise, current forecast looks on track and has a good handle
on current situation for the remainder of the night.

&&

.SHORT TERM...(Tonight)
ISSUED AT 225 PM CDT Tue May 3 2016

A Strong shortwave associated with 100kt jet will plunge into the
eastern U.S. trough that has been over the region the past few days.
Relatively strong dynamics with this fast system will have little in
way of deep moisture to work with. An associated cold front will
move across the region after midnight bringing a chance of showers.
The lower layers of the atmosphere are relatively dry and
precipitation amounts should be less than a quarter of an inch.

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 225 PM CDT Tue May 3 2016

Upper low forecast to dive south-southeast into the lower Great
Lakes on Wednesday with the associated cold front and shower
activity expected to be southeast of our forecast area during
the morning. However, 500 mb temperatures forecast to drop to
between -24C to -27C by afternoon over roughly the eastern half
of the forecast area. Will continue to hold onto scattered
showers for the afternoon with some thunder possible as well due
to the steep mid level lapse rates. Seeing some occasional
lightning this afternoon with the deep trof just north of Lake
Superior so will continue to hold with the thunder mention,
especially across the east where the temperatures aloft are the
coldest. The upper low should drift off to our east tomorrow night
with high pressure settling into the region for a couple of quiet
days for Thursday and Friday. After a rather cool couple of
days/nights for Wednesday and Thursday, we should see a nice
warmup for Friday and the weekend when the mercury will rise back
into the 70s, with a few 80s possible ahead of a cool front
Saturday afternoon.

The short lived omega block will begin to break down towards the
end of the week as a vigorous northern stream upper wave shifts
southeast into the upper Great Lakes by Saturday This will drive
another cold front into our area by Saturday afternoon with most
models now suggesting the trof amplifying to our east late
Saturday into Sunday will be strong enough to push the front
further south than earlier expected on Sunday. This would normally
shift the better rain chances further south as well but because a
couple of models have a further north solution to the boundary and
higher POPs, the consensus has mentionable POPs for Sunday into
early Sunday evening, although lower than what we had before,
before the boundary starts to edge back north Sunday night and
Monday resulting in 30-40 Pops CWA-wide again. If this further
south solution continues with the next several runs, we may be
able to lower POPs over most of the area on Sunday. Unfortunately,
with the evolving pattern late in the weekend and especially for
the first half of next week, it appears there will be a daily
threat for showers and thunderstorms through at least next
Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1203 PM CDT Wed May 4 2016

VFR conditions will prevail at all TAF sites next 24hrs. Sfc front
will drop quickly through the CWA early this morning and radar
indicates thunderstorms along with showers. So have changed to
VCTS with TEMPO group at all sites for thunderstorms. Once the
pcpn moves south skies will scatter out some. However, with the
500mb trough, additional clouds and VCSH will be seen at
DEC/CMI/BMI in the afternoon. Skies will scatter out and clear
after sunset at all sites. Winds will become northwesterly just
behind the front and then northerly during the day and into the
afternoon. Wind speeds will increase and gust to 23-26kts at all
sites. Winds speeds will decrease in the evening.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Auten
SHORT TERM...Barker
LONG TERM...Smith
AVIATION...Auten




000
FXUS63 KILX 040204
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
904 PM CDT TUE MAY 3 2016

.UPDATE...
Issued at 903 PM CDT Tue May 3 2016

Will be taking a look at the pop/wx grids to clean them up a bit.
Otherwise, current forecast looks on track and has a good handle
on current situation for the remainder of the night.

&&

.SHORT TERM...(Tonight)
ISSUED AT 225 PM CDT Tue May 3 2016

A Strong shortwave associated with 100kt jet will plunge into the
eastern U.S. trough that has been over the region the past few days.
Relatively strong dynamics with this fast system will have little in
way of deep moisture to work with. An associated cold front will
move across the region after midnight bringing a chance of showers.
The lower layers of the atmosphere are relatively dry and
precipitation amounts should be less than a quarter of an inch.

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 225 PM CDT Tue May 3 2016

Upper low forecast to dive south-southeast into the lower Great
Lakes on Wednesday with the associated cold front and shower
activity expected to be southeast of our forecast area during
the morning. However, 500 mb temperatures forecast to drop to
between -24C to -27C by afternoon over roughly the eastern half
of the forecast area. Will continue to hold onto scattered
showers for the afternoon with some thunder possible as well due
to the steep mid level lapse rates. Seeing some occasional
lightning this afternoon with the deep trof just north of Lake
Superior so will continue to hold with the thunder mention,
especially across the east where the temperatures aloft are the
coldest. The upper low should drift off to our east tomorrow night
with high pressure settling into the region for a couple of quiet
days for Thursday and Friday. After a rather cool couple of
days/nights for Wednesday and Thursday, we should see a nice
warmup for Friday and the weekend when the mercury will rise back
into the 70s, with a few 80s possible ahead of a cool front
Saturday afternoon.

The short lived omega block will begin to break down towards the
end of the week as a vigorous northern stream upper wave shifts
southeast into the upper Great Lakes by Saturday This will drive
another cold front into our area by Saturday afternoon with most
models now suggesting the trof amplifying to our east late
Saturday into Sunday will be strong enough to push the front
further south than earlier expected on Sunday. This would normally
shift the better rain chances further south as well but because a
couple of models have a further north solution to the boundary and
higher POPs, the consensus has mentionable POPs for Sunday into
early Sunday evening, although lower than what we had before,
before the boundary starts to edge back north Sunday night and
Monday resulting in 30-40 Pops CWA-wide again. If this further
south solution continues with the next several runs, we may be
able to lower POPs over most of the area on Sunday. Unfortunately,
with the evolving pattern late in the weekend and especially for
the first half of next week, it appears there will be a daily
threat for showers and thunderstorms through at least next
Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 710 PM CDT Tue May 3 2016

Skies will become scattered this evening, ahead of the next short
wave bringing pcpn to the area later tonight. Could be some
clouds, but think they will be cirrus, so no need to mention.
Believe HRRR model has a good handle on movement of the pcpn into
and through the area tonight, so followed its timing with pcpn
getting to PIA first around 05z, then SPI and BMI around 06z, then
CMI and DEC around 07z. Will have VCSH at all sites and then a
TEMPO group at for 3-4hrs where vis is lower due to showers and
slightly lower cigs. Besides the showers, VFR conditions will
prevail at all sites next 24hrs. After the pcpn, clouds will
become scattered or clear remainder of the night and early
morning. With cyclonic flow continuing tomorrow, clouds will
return and thicken, but only at DEC/CMI and BMI. In addition,
short term models indicate that more showers could be possible at
these three sites, so have included more VCSH. Winds will be
southwest ahead of the trough, but then become northwest and then
northerly tomorrow. Winds will become gusty as well.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Auten
SHORT TERM...Barker
LONG TERM...Smith
AVIATION...Auten




000
FXUS63 KLOT 040139 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
839 PM CDT TUE MAY 3 2016

.UPDATE...
838 PM CDT

THERE WERE ONLY A FEW CHANGES MADE TO THE FORECAST TONIGHT AND ALL
FAIRLY MINOR SINCE THE MAIN THEME OF THE FORECAST
CONTINUES...SHOWERS AND SOME STORMS TONIGHT WITH WINDY AND
COOLER CONDITIONS MOVING IN. THE CHANGES INCLUDED 1.) HAVING
INCREASED THE THUNDER LIKELIHOOD OVERNIGHT...2.) BUMPED UP WIND
GUSTS LATE TONIGHT AND WEDNESDAY MORNING ESPECIALLY NEAR THE LAKE
SHORE WHERE SOME GUSTS OF 40 TO 45 MPH ARE POSSIBLE...AND 3.) FOR
WEDNESDAY AFTERNOON WENT WITH MORE COVERAGE WORDING OF SHOWERS AS
CONFIDENCE IN DEVELOPMENT IS FAIRLY HIGH...ESPECIALLY FOR AREAS
EAST OF INTERSTATE 39.

WATER VAPOR IMAGERY THIS EVENING PORTRAYS A REALLY WELL-DEFINED
SHORT WAVE UPPER CIRCULATION AT THE LEADING EDGE OF A SHARPLY
DIGGING BROADER TROUGH. THE 00Z INL SOUNDING SAMPLED A 115 KT DUE
NORTHERLY JET...HIGHLY ANOMALOUS ORIENTATION AND SPEED FOR MAY.
THE SHORT WAVE HAS BEEN ON A STEADY TRACK TOWARD THE AREA WITH ITS
LEADING EDGE PRESENTLY IN CENTRAL WISCONSIN. CONVECTION AND
ASSOCIATED LIGHTNING HAS BEEN STEADY ALONG THIS FRONT EDGE AND
OFTEN WITH THESE COLD CORE WAVES KEEP THEIR LIGHTNING OVERNIGHT.
SO HAVE INCREASED THUNDER CHANCES AS STEEP MID-LEVEL LAPSE RATES
/SAMPLED ON 00Z MPX SOUNDING/ MOVE INTO THE REGION. THE OVERALL
COVERAGE OF SHOWERS AND ANTICIPATED FORCING...AS WELL AS OUTPUT
FROM CONVECTIVE ALLOWING MODELS...IS HIGH ENOUGH TO WARRANT NEAR
100 POPS BETWEEN MAINLY 11 PM AND 4 AM FROM NORTH TO SOUTH.

UPSTREAM OBSERVATIONS AT THE SURFACE ARE INDICATE A STRENGTHENING
ISALLOBARIC COUPLET AS THE LOW OF 1002 MB NEAR LA CROSSE
WISCONSIN CONTINUES TO DEEPEN. SOME UPSTREAM WINDS ARE ALREADY
OUTPERFORMING GUIDANCE AND WOULD EXPECT THAT TO CONTINUE TO BE THE
TREND IN THIS PATTERN. HAVE INCREASED GUSTS WITH TEMPORARY 30 TO
40 MPH GUSTS EXPECTED OVER MUCH OF THE AREA IMMEDIATELY BEHIND THE
FRONT AND THEN 30 TO 35 MPH GUSTS MUCH OF THE DAY WEDNESDAY.
CLOSER TO THE LAKE SHORE GIVEN THE FRICTIONLESS NORTHERLY
DIRECTION THE GUSTS SHOULD PEAK MORE 35 TO 45 MPH DURING WEDNESDAY
MORNING.

WAVES ARE LIKELY TO BUILD TO OR A LITTLE OVER 10 FT ON THE
CHICAGO SHORE BY LATER WEDNESDAY MORNING AND 12 TO 15 FT ALONG
THE INDIANA SHORE BY EARLY AFTERNOON. THIS FORECAST IS BELOW
THRESHOLDS FOR A LAKE FLOOD ADVISORY.

AS FOR FORECAST TEMPERATURES WEDNESDAY...THESE CONTINUE TO LOOK
TO BE ON TRACK WITH MID TO UPPER 40S HIGHS IN THE DOWNSTREAM PART
OF THE LAKE AND LOWER TO MID 50S ELSEWHERE.

MTF

&&

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVENING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS
WITH A FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED
AS CAPE VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 00Z TAFS...

MAIN FORECAST CONCERNS ARE WITH SHOWER AND THUNDER CHANCES LATER
TONIGHT...LOW END MVFR AND IFR CEILINGS...AND STRONG NORTHERLY
WINDS WEDNESDAY MORNING.

WESTERLY WINDS AND VFR CEILINGS OCCURRING EARLY THIS EVENING WILL
CONTINUE FOR MOST OF THE EVENING UNTIL AN AREA OF LOW PRESSURE AND
FRONTAL BOUNDARY QUICKLY PUSH SOUTH ACROSS THE REGION. DO EXPECT
AROUND A THREE HOUR WINDOW OF PREVAILING SHOWERS WITH SOME
EMBEDDED THUNDER TO OCCUR JUST AFTER THE MIDNIGHT TIME FRAME
TONIGHT. THE MAIN AREA OF PRECIP WILL SWING THROUGH BUT THERE DOES
APPEAR TO BE SOME IMMEDIATE SHOWER DEVELOPMENT STILL POSSIBLE
AFTER. VFR CEILINGS WILL QUICKLY LOWER TO LOW END MVFR AND IFR
DURING THAT TIME AND STAY IN PLACE THROUGH EARLY WEDNESDAY
MORNING. WINDS WILL ALSO QUICKLY SHIFT TO THE NORTH WITH
SPEEDS/GUSTS RAMPING UP...AND LOOKING TO STAY GUSTY OUT OF THE
NORTH FOR MOST OF WEDNESDAY. HAVE CONTINUED MENTION OF ADDITIONAL
SHOWER CHANCES THROUGHOUT THE DAY ON WEDNESDAY AND HAVE CONFIDENCE
OF OCCURRENCE...BUT LOWER CONFIDENCE WITH COVERAGE AND DURATION.

RODRIGUEZ

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742...3 AM WEDNESDAY TO 3 PM
     WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...3 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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 040010
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
710 PM CDT TUE MAY 3 2016

.SHORT TERM...(Tonight)
ISSUED AT 225 PM CDT Tue May 3 2016

A Strong shortwave associated with 100kt jet will plunge into the
eastern U.S. trough that has been over the region the past few days.
Relatively strong dynamics with this fast system will have little in
way of deep moisture to work with. An associated cold front will
move across the region after midnight bringing a chance of showers.
The lower layers of the atmosphere are relatively dry and
precipitation amounts should be less than a quarter of an inch.

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 225 PM CDT Tue May 3 2016

Upper low forecast to dive south-southeast into the lower Great
Lakes on Wednesday with the associated cold front and shower
activity expected to be southeast of our forecast area during
the morning. However, 500 mb temperatures forecast to drop to
between -24C to -27C by afternoon over roughly the eastern half
of the forecast area. Will continue to hold onto scattered
showers for the afternoon with some thunder possible as well due
to the steep mid level lapse rates. Seeing some occasional
lightning this afternoon with the deep trof just north of Lake
Superior so will continue to hold with the thunder mention,
especially across the east where the temperatures aloft are the
coldest. The upper low should drift off to our east tomorrow night
with high pressure settling into the region for a couple of quiet
days for Thursday and Friday. After a rather cool couple of
days/nights for Wednesday and Thursday, we should see a nice
warmup for Friday and the weekend when the mercury will rise back
into the 70s, with a few 80s possible ahead of a cool front
Saturday afternoon.

The short lived omega block will begin to break down towards the
end of the week as a vigorous northern stream upper wave shifts
southeast into the upper Great Lakes by Saturday This will drive
another cold front into our area by Saturday afternoon with most
models now suggesting the trof amplifying to our east late
Saturday into Sunday will be strong enough to push the front
further south than earlier expected on Sunday. This would normally
shift the better rain chances further south as well but because a
couple of models have a further north solution to the boundary and
higher POPs, the consensus has mentionable POPs for Sunday into
early Sunday evening, although lower than what we had before,
before the boundary starts to edge back north Sunday night and
Monday resulting in 30-40 Pops CWA-wide again. If this further
south solution continues with the next several runs, we may be
able to lower POPs over most of the area on Sunday. Unfortunately,
with the evolving pattern late in the weekend and especially for
the first half of next week, it appears there will be a daily
threat for showers and thunderstorms through at least next
Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 710 PM CDT Tue May 3 2016

Skies will become scattered this evening, ahead of the next short
wave bringing pcpn to the area later tonight. Could be some
clouds, but think they will be cirrus, so no need to mention.
Believe HRRR model has a good handle on movement of the pcpn into
and through the area tonight, so followed its timing with pcpn
getting to PIA first around 05z, then SPI and BMI around 06z, then
CMI and DEC around 07z. Will have VCSH at all sites and then a
TEMPO group at for 3-4hrs where vis is lower due to showers and
slightly lower cigs. Besides the showers, VFR conditions will
prevail at all sites next 24hrs. After the pcpn, clouds will
become scattered or clear remainder of the night and early
morning. With cyclonic flow continuing tomorrow, clouds will
return and thicken, but only at DEC/CMI and BMI. In addition,
short term models indicate that more showers could be possible at
these three sites, so have included more VCSH. Winds will be
southwest ahead of the trough, but then become northwest and then
northerly tomorrow. Winds will become gusty as well.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Barker
LONG TERM...Smith
AVIATION...Auten




000
FXUS63 KILX 040010
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
710 PM CDT TUE MAY 3 2016

.SHORT TERM...(Tonight)
ISSUED AT 225 PM CDT Tue May 3 2016

A Strong shortwave associated with 100kt jet will plunge into the
eastern U.S. trough that has been over the region the past few days.
Relatively strong dynamics with this fast system will have little in
way of deep moisture to work with. An associated cold front will
move across the region after midnight bringing a chance of showers.
The lower layers of the atmosphere are relatively dry and
precipitation amounts should be less than a quarter of an inch.

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 225 PM CDT Tue May 3 2016

Upper low forecast to dive south-southeast into the lower Great
Lakes on Wednesday with the associated cold front and shower
activity expected to be southeast of our forecast area during
the morning. However, 500 mb temperatures forecast to drop to
between -24C to -27C by afternoon over roughly the eastern half
of the forecast area. Will continue to hold onto scattered
showers for the afternoon with some thunder possible as well due
to the steep mid level lapse rates. Seeing some occasional
lightning this afternoon with the deep trof just north of Lake
Superior so will continue to hold with the thunder mention,
especially across the east where the temperatures aloft are the
coldest. The upper low should drift off to our east tomorrow night
with high pressure settling into the region for a couple of quiet
days for Thursday and Friday. After a rather cool couple of
days/nights for Wednesday and Thursday, we should see a nice
warmup for Friday and the weekend when the mercury will rise back
into the 70s, with a few 80s possible ahead of a cool front
Saturday afternoon.

The short lived omega block will begin to break down towards the
end of the week as a vigorous northern stream upper wave shifts
southeast into the upper Great Lakes by Saturday This will drive
another cold front into our area by Saturday afternoon with most
models now suggesting the trof amplifying to our east late
Saturday into Sunday will be strong enough to push the front
further south than earlier expected on Sunday. This would normally
shift the better rain chances further south as well but because a
couple of models have a further north solution to the boundary and
higher POPs, the consensus has mentionable POPs for Sunday into
early Sunday evening, although lower than what we had before,
before the boundary starts to edge back north Sunday night and
Monday resulting in 30-40 Pops CWA-wide again. If this further
south solution continues with the next several runs, we may be
able to lower POPs over most of the area on Sunday. Unfortunately,
with the evolving pattern late in the weekend and especially for
the first half of next week, it appears there will be a daily
threat for showers and thunderstorms through at least next
Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 710 PM CDT Tue May 3 2016

Skies will become scattered this evening, ahead of the next short
wave bringing pcpn to the area later tonight. Could be some
clouds, but think they will be cirrus, so no need to mention.
Believe HRRR model has a good handle on movement of the pcpn into
and through the area tonight, so followed its timing with pcpn
getting to PIA first around 05z, then SPI and BMI around 06z, then
CMI and DEC around 07z. Will have VCSH at all sites and then a
TEMPO group at for 3-4hrs where vis is lower due to showers and
slightly lower cigs. Besides the showers, VFR conditions will
prevail at all sites next 24hrs. After the pcpn, clouds will
become scattered or clear remainder of the night and early
morning. With cyclonic flow continuing tomorrow, clouds will
return and thicken, but only at DEC/CMI and BMI. In addition,
short term models indicate that more showers could be possible at
these three sites, so have included more VCSH. Winds will be
southwest ahead of the trough, but then become northwest and then
northerly tomorrow. Winds will become gusty as well.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Barker
LONG TERM...Smith
AVIATION...Auten




000
FXUS63 KLOT 032351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
651 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 00Z TAFS...

MAIN FORECAST CONCERNS ARE WITH SHOWER AND THUNDER CHANCES LATER
TONIGHT...LOW END MVFR AND IFR CEILINGS...AND STRONG NORTHERLY
WINDS WEDNESDAY MORNING.

WESTERLY WINDS AND VFR CEILINGS OCCURRING EARLY THIS EVENING WILL
CONTINUE FOR MOST OF THE EVENING UNTIL AN AREA OF LOW PRESSURE AND
FRONTAL BOUNDARY QUICKLY PUSH SOUTH ACROSS THE REGION. DO EXPECT
AROUND A THREE HOUR WINDOW OF PREVAILING SHOWERS WITH SOME
EMBEDDED THUNDER TO OCCUR JUST AFTER THE MIDNIGHT TIME FRAME
TONIGHT. THE MAIN AREA OF PRECIP WILL SWING THROUGH BUT THERE DOES
APPEAR TO BE SOME IMMEDIATE SHOWER DEVELOPMENT STILL POSSIBLE
AFTER. VFR CEILINGS WILL QUICKLY LOWER TO LOW END MVFR AND IFR
DURING THAT TIME AND STAY IN PLACE THROUGH EARLY WEDNESDAY
MORNING. WINDS WILL ALSO QUICKLY SHIFT TO THE NORTH WITH
SPEEDS/GUSTS RAMPING UP...AND LOOKING TO STAY GUSTY OUT OF THE
NORTH FOR MOST OF WEDNESDAY. HAVE CONTINUED MENTION OF ADDITIONAL
SHOWER CHANCES THROUGHOUT THE DAY ON WEDNESDAY AND HAVE CONFIDENCE
OF OCCURRENCE...BUT LOWER CONFIDENCE WITH COVERAGE AND DURATION.

RODRIGUEZ

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ740-LMZ741-LMZ742...3 AM WEDNESDAY TO 3 PM
     WEDNESDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...3 PM WEDNESDAY TO
     10 AM THURSDAY.

     GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...3 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

&&

$$

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

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




000
FXUS63 KLOT 032034
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
334 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
333 PM CDT

A COLD FRONT IS EXPECTED TO SHIFT SOUTHWARD DOWN THE LAKE TONIGHT.
THIS WILL SET UP NORTHERLY FLOW LAKE-WIDE BY DAYBREAK WEDNESDAY. IT
ALSO APPEARS THAT GALE FORCE WINDS WILL OCCUR ON THE SOUTHERN HALF
OF THE LAKE WEDNESDAY INTO WEDNESDAY EVENING AS THE SURFACE GRADIENT
TIGHTENS IN RESPONSE TO A DEVELOPING SURFACE LOW OVER LOWER MICHIGAN
AND NORTHERN OHIO. WITH THIS IN MIND...WE HAVE ISSUED A GALE WARNING
FOR THE SOUTHERN HALF OF THE LAKE. AT THE PRESENT TIME...WE HAVE
LEFT THE ILLINOIS NEAR SHORES OUT OF THIS GALE AS IT APPEARS THE
STRONGEST WINDS WILL REMAIN OVER THE OPEN WATERS AND INTO THE
INDIANA NEAR SHORE WATERS. THEREFORE...THE SMALL CRAFT ADVISORY
CONTINUES FOR THE ILLINOIS WATERS. THE WINDS LOOK TO ABATE LATE
WEDNESDAY NIGHT INTO THURSDAY AS A SURFACE RIDGE OF HIGH PRESSURE
BUILDS OVER THE WESTERN GREAT LAKES. THIS SHOULD RESULT IN A QUICK
END TO THE GALES WEDNESDAY NIGHT.

WINDS LOOK TO BECOME SOUTHERLY AGAIN ON FRIDAY AHEAD OF ANOTHER
STORM SYSTEM MOVING INTO WESTERN ONTARIO. THIS STORM SYSTEM IS
EXPECTED TO PUSH ANOTHER COLD FRONT SOUTHWARD DOWN THE LAKE ON
SATURDAY...AND THIS COULD RESULT IN ANOTHER PERIOD OF ENHANCED
NORTHERLY WINDS ON SATURDAY.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...5 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 AM WEDNESDAY TO
     10 AM THURSDAY.

&&

$$

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 032000
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
300 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
259 PM CDT

WEDNESDAY NIGHT THROUGH TUESDAY...

THE PERIOD WILL BEGIN ON THE CHILLY SIDE WEDNESDAY NIGHT AS THE
LINGERING EFFECTS OF THE UNSEASONABLE STRONG UPPER LOW CONTINUES
TO SHIFT OVER THE LOWER OHIO VALLEY. CLEARING SKIES WEDNESDAY
NIGHT SHOULD ALLOW TEMPERATURES TO RADIATE SOME INTO THE UPPER
30S...ESPECIALLY ACROSS NORTH CENTRAL ILLINOIS AND PORTIONS OF THE
FOX RIVER VALLEY...AND LOWER 40S ELSEWHERE. IT APPEARS THAT A
LIGHT NORTHERLY WIND WILL CONTINUE THROUGH MUCH OF THE NIGHT...SO
THE THREAT OF FROST LOOKS LIKE IT WOULD ONLY BE SPOTTY AND
CONFINED TO WELL PROTECTED AREAS...SO WE WILL LEAVE THIS MENTION
OUT OF THE FORECAST FOR NOW. OTHERWISE...EXPECT A SURFACE RIDGE OF
HIGH PRESSURE TO BUILD OVER THE AREA ON THURSDAY. ONSHORE FLOW
WILL AGAIN RESULT IN NEAR 50 DEGREE TEMPERATURES ALONG THE
LAKEFRONT...BUT FARTHER INLAND TEMPERATURES LOOK TO REBOUND BACK
INTO THE LOWER 60S UNDER MAINLY SUNNY SKIES.

MUCH WARMER CONDITIONS ARE EXPECTED ON FRIDAY AS A WESTERLY WIND
SHIFT ALLOWS THE THERMAL RIDGE OVER THE PLAINS TO SHIFT OVER THE
WESTERN GREAT LAKES. MODEL GUIDANCE IS ADVERTISING 925 MB
TEMPERATURES AROUND +20C BY MIDDAY FRIDAY. THIS SHOULD ALLOW
TEMPERATURES TO WARM INTO THE LOWER 80S...ESPECIALLY OVER NORTH
CENTRAL ILLINOIS. THERE IS A POSSIBILITY THAT A LAKE BREEZE COULD
DEVELOP FRIDAY AFTERNOON DUE TO RELATIVELY WEAK WESTERLY FLOW AT
THE LAKE FRONT...AND THIS COULD RESULT IN SLIGHTLY COOLER
CONDITIONS THERE IF ONE DOES DEVELOP. IN ADDITION TO THE QUICK
WARM-UP...I CANNOT TOTALLY RULE OUT A FEW ISOLATED OR WIDELY
SCATTERED THUNDERSTORMS LATE THURSDAY NIGHT INTO FRIDAY WITHIN THE
STRONG WARM AIR ADVECTION REGIME. HOWEVER...DUE TO THE RELATIVELY
WEAK SIGNAL...AND THE LIKELY LOW AREAL COVERAGE...WE HAVE OPTED TO
LEAVE THE FORECAST DRY AT THIS TIME.

A POTENT AND FAST EASTWARD MOVING STORM SYSTEM ACROSS SOUTHERN
CANADA FRIDAY INTO SATURDAY LOOKS TO DROP A COLD FRONT SOUTHWARD
OVER THE AREA BY LATE SATURDAY. THIS SHOULD SET THE STAGE FOR OUR
NEXT DECENT THREAT FOR SHOWERS AND THUNDERSTORMS. ALTHOUGH DEEP
LAYER SHEAR IS NOT ADVERTISED TO BE OVERLY IMPRESSIVE OVER THE
AREA...WE CANT RULE OUT A FEW STRONG THUNDERSTORMS WITH THIS
FRONTAL PASSAGE SATURDAY AFTERNOON. ALSO...WITH THE TIMING OF THIS
FRONT LOOKING TO BE DURING THE MIDDAY TO AFTERNOON HOURS...IT
APPEARS HIGHS ON SATURDAY COULD AGAIN REACH INTO THE 70S IN MOST
INLAND AREAS...TO POSSIBLY LOW 80S AGAIN SOUTH PRIOR TO THE ONSET
OF CONVECTION WITH THE APPROACHING FRONTAL BOUNDARY.

SURFACE HIGH PRESSURE LOOKS TO SET UP OVER THE AREA BY SUNDAY...SO
DRY...BUT COOLER CONDITIONS IN THE 60S ARE EXPECTED.
HOWEVER...WARMER CONDITIONS...INTO THE 70S...BEGIN TO RETURN BY
EARLY NEXT WEEK. IT ALSO APPEARS THE THE WEATHER PATTERN COULD BE
CONDUCIVE TO ADDITIONAL PERIODS OF SHOWERS AND THUNDERSTORMS INTO
NEXT WEEK AS MODEL/ENSEMBLE GUIDANCE ALL ARE FORECASTING ANOTHER
STORM SYSTEM TO TAKE SHAPE OVER THE PLAINS AND THEN SHIFT INTO THE
UPPER MIDWEST BY THE MIDDLE OF NEXT WEEK.

KJB

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...5 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 AM WEDNESDAY TO
     10 AM THURSDAY.

&&

$$

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 031936
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
236 PM CDT TUE MAY 3 2016

.SHORT TERM...(Tonight)
ISSUED AT 225 PM CDT Tue May 3 2016

A Strong shortwave associated with 100kt jet will plunge into the
eastern U.S. trough that has been over the region the past few days.
Relatively strong dynamics with this fast system will have little in
way of deep moisture to work with. An associated cold front will
move across the region after midnight bringing a chance of showers.
The lower layers of the atmosphere are relatively dry and
precipitation amounts should be less than a quarter of an inch.

&&

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 225 PM CDT Tue May 3 2016

Upper low forecast to dive south-southeast into the lower Great
Lakes on Wednesday with the associated cold front and shower
activity expected to be southeast of our forecast area during
the morning. However, 500 mb temperatures forecast to drop to
between -24C to -27C by afternoon over roughly the eastern half
of the forecast area. Will continue to hold onto scattered
showers for the afternoon with some thunder possible as well due
to the steep mid level lapse rates. Seeing some occasional
lightning this afternoon with the deep trof just north of Lake
Superior so will continue to hold with the thunder mention,
especially across the east where the temperatures aloft are the
coldest. The upper low should drift off to our east tomorrow night
with high pressure settling into the region for a couple of quiet
days for Thursday and Friday. After a rather cool couple of
days/nights for Wednesday and Thursday, we should see a nice
warmup for Friday and the weekend when the mercury will rise back
into the 70s, with a few 80s possible ahead of a cool front
Saturday afternoon.

The short lived omega block will begin to break down towards the
end of the week as a vigorous northern stream upper wave shifts
southeast into the upper Great Lakes by Saturday This will drive
another cold front into our area by Saturday afternoon with most
models now suggesting the trof amplifying to our east late
Saturday into Sunday will be strong enough to push the front
further south than earlier expected on Sunday. This would normally
shift the better rain chances further south as well but because a
couple of models have a further north solution to the boundary and
higher POPs, the concensus has mentionable POPs for Sunday into
early Sunday evening, although lower than what we had before,
before the boundary starts to edge back north Sunday night and
Monday resulting in 30-40 Pops CWA-wide again. If this further
south solution continues with the next several runs, we may be
able to lower POPs over most of the area on Sunday. Unfortunately,
with the evolving pattern late in the weekend and especially for
the first half of next week, it appears there will be a daily
threat for showers and thunderstorms through at least next
Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1138 AM CDT Tue May 3 2016

Strong low-level lapse rates are combining with daytime heating to
develop cumulus field at midday. Most terminals in central
Illinois will likely have broken VFR ceilings by early this
afternoon. As heating diminishes so will the cumulus field.

A fast moving system over western ontario will race south pushing
a cold front through the state late tonight. Dynamics are
relatively strong, but moisture - particularly in boundary layer -
is somewhat limited. Will introduce a tempo group of MVFR precip for
the period suggested by NAM.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Barker
LONG TERM...Smith
AVIATION...Barker




000
FXUS63 KILX 031936
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
236 PM CDT TUE MAY 3 2016

.SHORT TERM...(Tonight)
ISSUED AT 225 PM CDT Tue May 3 2016

A Strong shortwave associated with 100kt jet will plunge into the
eastern U.S. trough that has been over the region the past few days.
Relatively strong dynamics with this fast system will have little in
way of deep moisture to work with. An associated cold front will
move across the region after midnight bringing a chance of showers.
The lower layers of the atmosphere are relatively dry and
precipitation amounts should be less than a quarter of an inch.

&&

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 225 PM CDT Tue May 3 2016

Upper low forecast to dive south-southeast into the lower Great
Lakes on Wednesday with the associated cold front and shower
activity expected to be southeast of our forecast area during
the morning. However, 500 mb temperatures forecast to drop to
between -24C to -27C by afternoon over roughly the eastern half
of the forecast area. Will continue to hold onto scattered
showers for the afternoon with some thunder possible as well due
to the steep mid level lapse rates. Seeing some occasional
lightning this afternoon with the deep trof just north of Lake
Superior so will continue to hold with the thunder mention,
especially across the east where the temperatures aloft are the
coldest. The upper low should drift off to our east tomorrow night
with high pressure settling into the region for a couple of quiet
days for Thursday and Friday. After a rather cool couple of
days/nights for Wednesday and Thursday, we should see a nice
warmup for Friday and the weekend when the mercury will rise back
into the 70s, with a few 80s possible ahead of a cool front
Saturday afternoon.

The short lived omega block will begin to break down towards the
end of the week as a vigorous northern stream upper wave shifts
southeast into the upper Great Lakes by Saturday This will drive
another cold front into our area by Saturday afternoon with most
models now suggesting the trof amplifying to our east late
Saturday into Sunday will be strong enough to push the front
further south than earlier expected on Sunday. This would normally
shift the better rain chances further south as well but because a
couple of models have a further north solution to the boundary and
higher POPs, the concensus has mentionable POPs for Sunday into
early Sunday evening, although lower than what we had before,
before the boundary starts to edge back north Sunday night and
Monday resulting in 30-40 Pops CWA-wide again. If this further
south solution continues with the next several runs, we may be
able to lower POPs over most of the area on Sunday. Unfortunately,
with the evolving pattern late in the weekend and especially for
the first half of next week, it appears there will be a daily
threat for showers and thunderstorms through at least next
Tuesday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1138 AM CDT Tue May 3 2016

Strong low-level lapse rates are combining with daytime heating to
develop cumulus field at midday. Most terminals in central
Illinois will likely have broken VFR ceilings by early this
afternoon. As heating diminishes so will the cumulus field.

A fast moving system over western ontario will race south pushing
a cold front through the state late tonight. Dynamics are
relatively strong, but moisture - particularly in boundary layer -
is somewhat limited. Will introduce a tempo group of MVFR precip for
the period suggested by NAM.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Barker
LONG TERM...Smith
AVIATION...Barker




000
FXUS63 KLOT 031928
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
228 PM CDT TUE MAY 3 2016

.SHORT TERM...
228 PM CDT

THROUGH WEDNESDAY...

BIG CHANGES ARE IN STORE IN THE SHORT TERM. HIGH PRESSURE IS SLOWLY
SHIFTING SOUTH AS LOW PRESSURE AND A COLD FRONT DROP SOUTH OUT OF
ONTARIO.  EXPECTING A PLEASANT AFTERNOON AND EVENING WITH WEST WINDS
AND FAIR WEATHER CUMULUS CLOUDS.  SHOWERS HAVE ALREADY FORMED AHEAD
OF THE COLD FRONT OVER THE U.P. OF MICHIGAN. REALLY LIKING THE RAP/S
TIMING SO LEANED HEAVILY IN ITS DIRECTION...WITH THE NAM BEING A
SLOWER SOLUTION.  HAVE SLIGHT CHANCE TO CHANCE POPS OUT AHEAD OF THE
MAIN FRONTAL PRECIP JUST IN CASE A FEW STRAY SHOWERS FORM THIS
EVEING. KEPT THE PREVIOUS FORECASTS IDEA OF NUMEROUS SHOWERS WITH A
FEW EMBEDDED THUNDERSTORMS. SEVERE STORMS ARE NOT EXPECTED AS CAPE
VALUES WILL BE MINIMAL AT BEST.

THE BIGGER STORY WILL BE WINDS SHIFTING OUT OF THE NORTH AND GUSTING
TO 30 MPH BEHIND THE FRONT. WINDS WILL BE EVEN GUSTIER ALONG THE
SOUTHERN END OF LAKE MICHIGAN ESPECIALLY ALONG THE INDIANA SHORE.
MUCH COOLER TEMPERATURES FOLLOW THE FRONT WITH HIGHS IN THE LOW TO
MID 50S AWAY FROM THE LAKE.  HIGHS ALONG THE LAKE WILL BE IN THE
UPPER 40S TO MAYBE 50.  THE BACK END OF THE UPPER LEVEL LOW ROTATES
THROUGH TOMORROW AND EXPECTING SCATTERED SHOWERS TO FORM.  FORECAST
SOUNDINGS SHOW VERY SHALLOW CAPE...BUT ANY CONVECTION WOULD BE VERY
LOW TOPPED.  FREEZING LEVELS ARE ALSO LOW AROUND 3000 FT SO THINKING
THE LOW CAPE AND STEEP LAPSE RATES WILL LEAD TO GRAUPEL INSTEAD OF
THUNDER.  NOT EXPECTING A TON OF RAIN...MORE ALONG THE LINES OF
DREARY CONDITIONS WITH OCNL LIGHT RAIN AND POSSIBLY GRAUPEL.

JEE

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ743-LMZ744-LMZ745-LMZ777-LMZ779...5 AM
     WEDNESDAY TO 4 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...4 AM THURSDAY TO 3
     PM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 AM WEDNESDAY TO
     10 AM THURSDAY.

&&

$$

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 031741
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1241 PM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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

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




000
FXUS63 KLOT 031741
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1241 PM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

THE REMAINDER OF THIS AFTERNOON SHOULD BE QUIET WITH HIGH PRESSURE
SLOWLY DRIFTING SOUTH. VFR CU AND NORTHWEST TO WEST WINDS ARE
EXPECTED. THE LOW OVER ONTARIO AND ITS ASSOCIATED COLD FRONT WILL
SHIFT SOUTH THIS EVENING AND OVERNIGHT. SHOWERS AND A FEW EMBEDDED
THUNDERSTORMS WILL MOVE THROUGH AHEAD OF THE FRONT. HAVE MUCH
HIGHER CONFIDENCE IN SHOWERS THAN THUNDER. THUNDER WILL BE AROUND
BUT DO NOT HAVE  ENOUGH CONFIDENCE IN LOCATION...COVERAGE...AND
EXACT TIMING TO INCLUDE THUNDER IN THE TAF. CIGS WILL FALL TO IFR
BEHIND THE FRONT. HAVE A LITTLE LOWER CONFIDENCE IN IFR AT RFD.
ALSO RAISED NORTH WIND SPEEDS WITH GUSTS TO 25 KT EXCEPT FOR
GUSTS TO 30 KT AT GYY. CIGS IMPROVE TO MVFR BY MID MORNING...BUT
ALSO EXPECTING SCATTERED SHOWERS AS THE BACK END OF THE UPPER
LEVEL SYSTEM ROTATES THROUGH. NOT EXPECTING RAIN ALL DAY
TOMORROW...BUT THE SHOWERS SHOULD BE SCATTERED ENOUGH TO JUSTIFY A
VCSH.

JEE

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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

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




000
FXUS63 KILX 031701
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1201 PM CDT TUE MAY 3 2016

.UPDATE...
Issued at 1022 AM CDT Tue May 3 2016

No significant forecast changes anticipated this morning. With
significant low-level lapse rates expect cumulus field to quickly
develop by midday which should slow warming in line with current
package. Clouds should diminish late this afternoon but then
increase again with the approaching cold front tonight. Still
appears best rain chances should be confined to after midnight.

&&

.SHORT TERM...(Today)
ISSUED AT 304 AM CDT Tue May 3 2016

Another mostly quiet day is anticipated today across central and
southeast Illinois. Main concern revolves around cloud cover and if
there will be any precipitation.

Forecast area remains under the influence of a sheared trof axis
aloft, and weakly cyclonic flow at the surface. This scenario will
change little during the day today. A piece of energy within the
sheared trof is coming through the area at the moment with little
fanfare, although there are a few very weak/spotty radar returns.
However, have not seen recent reports of any of these returns
reaching the ground. Some additional sheared energy will impact the
area later today, but it will have very little instability to work
with. So think this feature should come through dry, but have
maintained a very low PoP in extreme SE IL where the instability may
be a bit better. Ultimately, based on forecast soundings & the items
mentioned above, think most of what we will see this afternoon is an
enhanced diurnal CU field and little more than a few sprinkles.

.LONG TERM...(Tonight through Monday)
ISSUED AT 304 AM CDT Tue May 3 2016

Latest models show little change in the projected upper air pattern
over the next several days. Current upper ridge already in place
with high pressure centered over southern Alberta. As the current
system over the central Plains and mid-Mississippi Valley drops
southward today, it will yield to an upper low that is now in
northwest Ontario and is projected to reach Lake Michigan on
Wednesday morning. Cooler conditions are expected for a few days as
a broad trough covers the eastern CONUS, but as the ridge shifts
eastward on Friday, significantly warmer conditions expected. Latest
blended guidance brings highs into the mid 70s over the western CWA
as early as Friday, and 80 degree readings over much of the forecast
area on Saturday.

Surface boundary associated with the Ontario system appears to be
picking up speed, and have increased PoP`s quite a bit and somewhat
faster than earlier, with likely PoP`s over areas north of Peoria as
early as late evening. Also went with a period of 60% PoP`s over
east central Illinois after midnight. The window for rain looks to
only last about a couple hours at any given location, given the
speed of this system. Some steeper mid-level lapse rates favor a few
rumbles of thunder as well. Have maintained some chance PoP`s over
the eastern half of the forecast area as well on Wednesday due to
the arrival of the upper low.

Weekend system starting to come into a little better agreement in
the longer range models. Both the GFS and ECMWF settle a quasi-
stationary front over central Illinois by Saturday afternoon,
lingering in the general area through Sunday. How fast this boundary
retreats northward is more in question, with our region caught
between the southern jet stream being steered south of the upper low
over the 4-corners region, and the northern jet stream coming
through the Great Lakes. Thus, once precipitation chances develop
through the day Saturday, chance PoP`s will remain in the forecast
into Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1138 AM CDT Tue May 3 2016

Strong low-level lapse rates are combining with daytime heating to
develop cumulus field at midday. Most terminals in central
Illinois will likely have broken VFR ceilings by early this
afternoon. As heating diminishes so will the cumulus field.

A fast moving system over western ontario will race south pushing
a cold front through the state late tonight. Dynamics are
relatively strong, but moisture - particularly in boundary layer -
is somewhat limited. Will introduce a tempo group of MVFR precip for
the period suggested by NAM.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Barker
SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...Barker




000
FXUS63 KILX 031701
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1201 PM CDT TUE MAY 3 2016

.UPDATE...
Issued at 1022 AM CDT Tue May 3 2016

No significant forecast changes anticipated this morning. With
significant low-level lapse rates expect cumulus field to quickly
develop by midday which should slow warming in line with current
package. Clouds should diminish late this afternoon but then
increase again with the approaching cold front tonight. Still
appears best rain chances should be confined to after midnight.

&&

.SHORT TERM...(Today)
ISSUED AT 304 AM CDT Tue May 3 2016

Another mostly quiet day is anticipated today across central and
southeast Illinois. Main concern revolves around cloud cover and if
there will be any precipitation.

Forecast area remains under the influence of a sheared trof axis
aloft, and weakly cyclonic flow at the surface. This scenario will
change little during the day today. A piece of energy within the
sheared trof is coming through the area at the moment with little
fanfare, although there are a few very weak/spotty radar returns.
However, have not seen recent reports of any of these returns
reaching the ground. Some additional sheared energy will impact the
area later today, but it will have very little instability to work
with. So think this feature should come through dry, but have
maintained a very low PoP in extreme SE IL where the instability may
be a bit better. Ultimately, based on forecast soundings & the items
mentioned above, think most of what we will see this afternoon is an
enhanced diurnal CU field and little more than a few sprinkles.

.LONG TERM...(Tonight through Monday)
ISSUED AT 304 AM CDT Tue May 3 2016

Latest models show little change in the projected upper air pattern
over the next several days. Current upper ridge already in place
with high pressure centered over southern Alberta. As the current
system over the central Plains and mid-Mississippi Valley drops
southward today, it will yield to an upper low that is now in
northwest Ontario and is projected to reach Lake Michigan on
Wednesday morning. Cooler conditions are expected for a few days as
a broad trough covers the eastern CONUS, but as the ridge shifts
eastward on Friday, significantly warmer conditions expected. Latest
blended guidance brings highs into the mid 70s over the western CWA
as early as Friday, and 80 degree readings over much of the forecast
area on Saturday.

Surface boundary associated with the Ontario system appears to be
picking up speed, and have increased PoP`s quite a bit and somewhat
faster than earlier, with likely PoP`s over areas north of Peoria as
early as late evening. Also went with a period of 60% PoP`s over
east central Illinois after midnight. The window for rain looks to
only last about a couple hours at any given location, given the
speed of this system. Some steeper mid-level lapse rates favor a few
rumbles of thunder as well. Have maintained some chance PoP`s over
the eastern half of the forecast area as well on Wednesday due to
the arrival of the upper low.

Weekend system starting to come into a little better agreement in
the longer range models. Both the GFS and ECMWF settle a quasi-
stationary front over central Illinois by Saturday afternoon,
lingering in the general area through Sunday. How fast this boundary
retreats northward is more in question, with our region caught
between the southern jet stream being steered south of the upper low
over the 4-corners region, and the northern jet stream coming
through the Great Lakes. Thus, once precipitation chances develop
through the day Saturday, chance PoP`s will remain in the forecast
into Monday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1138 AM CDT Tue May 3 2016

Strong low-level lapse rates are combining with daytime heating to
develop cumulus field at midday. Most terminals in central
Illinois will likely have broken VFR ceilings by early this
afternoon. As heating diminishes so will the cumulus field.

A fast moving system over western ontario will race south pushing
a cold front through the state late tonight. Dynamics are
relatively strong, but moisture - particularly in boundary layer -
is somewhat limited. Will introduce a tempo group of MVFR precip for
the period suggested by NAM.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Barker
SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...Barker




000
FXUS63 KILX 031522
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1022 AM CDT TUE MAY 3 2016

.UPDATE...
Issued at 1022 AM CDT Tue May 3 2016

No significant forecast changes anticipated this morning. With
significant low-level lapse rates expect cumulus field to quickly
develop by midday which should slow warming in line with current
package. Clouds should diminish late this afternoon but then
increase again with the approaching cold front tonight. Still
appears best rain chances should be confined to after midnight.

&&

.SHORT TERM...(Today)
ISSUED AT 304 AM CDT Tue May 3 2016

Another mostly quiet day is anticipated today across central and
southeast Illinois. Main concern revolves around cloud cover and if
there will be any precipitation.

Forecast area remains under the influence of a sheared trof axis
aloft, and weakly cyclonic flow at the surface. This scenario will
change little during the day today. A piece of energy within the
sheared trof is coming through the area at the moment with little
fanfare, although there are a few very weak/spotty radar returns.
However, have not seen recent reports of any of these returns
reaching the ground. Some additional sheared energy will impact the
area later today, but it will have very little instability to work
with. So think this feature should come through dry, but have
maintained a very low PoP in extreme SE IL where the instability may
be a bit better. Ultimately, based on forecast soundings & the items
mentioned above, think most of what we will see this afternoon is an
enhanced diurnal CU field and little more than a few sprinkles.

.LONG TERM...(Tonight through Monday)
ISSUED AT 304 AM CDT Tue May 3 2016

Latest models show little change in the projected upper air pattern
over the next several days. Current upper ridge already in place
with high pressure centered over southern Alberta. As the current
system over the central Plains and mid-Mississippi Valley drops
southward today, it will yield to an upper low that is now in
northwest Ontario and is projected to reach Lake Michigan on
Wednesday morning. Cooler conditions are expected for a few days as
a broad trough covers the eastern CONUS, but as the ridge shifts
eastward on Friday, significantly warmer conditions expected. Latest
blended guidance brings highs into the mid 70s over the western CWA
as early as Friday, and 80 degree readings over much of the forecast
area on Saturday.

Surface boundary associated with the Ontario system appears to be
picking up speed, and have increased PoP`s quite a bit and somewhat
faster than earlier, with likely PoP`s over areas north of Peoria as
early as late evening. Also went with a period of 60% PoP`s over
east central Illinois after midnight. The window for rain looks to
only last about a couple hours at any given location, given the
speed of this system. Some steeper mid-level lapse rates favor a few
rumbles of thunder as well. Have maintained some chance PoP`s over
the eastern half of the forecast area as well on Wednesday due to
the arrival of the upper low.

Weekend system starting to come into a little better agreement in
the longer range models. Both the GFS and ECMWF settle a quasi-
stationary front over central Illinois by Saturday afternoon,
lingering in the general area through Sunday. How fast this boundary
retreats northward is more in question, with our region caught
between the southern jet stream being steered south of the upper low
over the 4-corners region, and the northern jet stream coming
through the Great Lakes. Thus, once precipitation chances develop
through the day Saturday, chance PoP`s will remain in the forecast
into Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 700 AM CDT Tue May 3 2016

Aside from some patchy MVFR fog early this morning, VFR conditions
are expected to prevail through the bulk of the 12Z TAF valid
time. Clouds will thicken up tonight as a cold front pushes into
the area. This front will likely be accompanied by showers, and
have included a VCSH mention after midnight for now.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Barker
SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...BAK




000
FXUS63 KILX 031206
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
706 AM CDT TUE MAY 3 2016

.SHORT TERM...(Today)
ISSUED AT 304 AM CDT Tue May 3 2016

Another mostly quiet day is anticipated today across central and
southeast Illinois. Main concern revolves around cloud cover and if
there will be any precipitation.

Forecast area remains under the influence of a sheared trof axis
aloft, and weakly cyclonic flow at the surface. This scenario will
change little during the day today. A piece of energy within the
sheared trof is coming through the area at the moment with little
fanfare, although there are a few very weak/spotty radar returns.
However, have not seen recent reports of any of these returns
reaching the ground. Some additional sheared energy will impact the
area later today, but it will have very little instability to work
with. So think this feature should come through dry, but have
maintained a very low PoP in extreme SE IL where the instability may
be a bit better. Ultimately, based on forecast soundings & the items
mentioned above, think most of what we will see this afternoon is an
enhanced diurnal CU field and little more than a few sprinkles.

.LONG TERM...(Tonight through Monday)
ISSUED AT 304 AM CDT Tue May 3 2016

Latest models show little change in the projected upper air pattern
over the next several days. Current upper ridge already in place
with high pressure centered over southern Alberta. As the current
system over the central Plains and mid-Mississippi Valley drops
southward today, it will yield to an upper low that is now in
northwest Ontario and is projected to reach Lake Michigan on
Wednesday morning. Cooler conditions are expected for a few days as
a broad trough covers the eastern CONUS, but as the ridge shifts
eastward on Friday, significantly warmer conditions expected. Latest
blended guidance brings highs into the mid 70s over the western CWA
as early as Friday, and 80 degree readings over much of the forecast
area on Saturday.

Surface boundary associated with the Ontario system appears to be
picking up speed, and have increased PoP`s quite a bit and somewhat
faster than earlier, with likely PoP`s over areas north of Peoria as
early as late evening. Also went with a period of 60% PoP`s over
east central Illinois after midnight. The window for rain looks to
only last about a couple hours at any given location, given the
speed of this system. Some steeper mid-level lapse rates favor a few
rumbles of thunder as well. Have maintained some chance PoP`s over
the eastern half of the forecast area as well on Wednesday due to
the arrival of the upper low.

Weekend system starting to come into a little better agreement in
the longer range models. Both the GFS and ECMWF settle a quasi-
stationary front over central Illinois by Saturday afternoon,
lingering in the general area through Sunday. How fast this boundary
retreats northward is more in question, with our region caught
between the southern jet stream being steered south of the upper low
over the 4-corners region, and the northern jet stream coming
through the Great Lakes. Thus, once precipitation chances develop
through the day Saturday, chance PoP`s will remain in the forecast
into Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 700 AM CDT Tue May 3 2016

Aside from some patchy MVFR fog early this morning, VFR conditions
are expected to prevail through the bulk of the 12Z TAF valid
time. Clouds will thicken up tonight as a cold front pushes into
the area. This front will likely be accompanied by showers, and
have included a VCSH mention after midnight for now.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...BAK




000
FXUS63 KLOT 031122
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
622 AM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

RIDGE AXIS IN PLACE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA
EARLY THIS MORNING WILL SHIFT SOUTH TODAY ALLOWING WESTERLY
WINDS TO PICK UP THROUGH THE DAY. GUSTS TO NEAR 20 KT ARE POSSIBLE
DURING THE AFTERNOON HOURS AS THE GRADIENT TIGHTENS AHEAD OF AN
APPROACHING COLD FRONT. EXPECT VFR CONDITIONS WITH MAINLY MID/HIGH
LEVEL CLOUD COVER TODAY. LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS...A COLD FRONT WILL SWEEP ACROSS THE REGION.
EXPECT SCATTERED SHOWERS AND A PERHAPS A FEW THUNDERSTORMS TO BE
IN PLACE AHEAD OF THE FRONT LATE THIS EVENING. GIVEN THE OVERNIGHT
TIMING OF THE FRONT AND VERY WEAK INSTABILITY NOTED IN FORECAST
SOUNDINGS THIS EVENING...WILL NOT MENTION THUNDER IN THE TAFS FOR
NOW...THOUGH THEY REMAIN A SMALL POSSIBILITY. ONCE THE FRONT
SWEEPS THROUGH...PRECIP SHOULD TAPER AND LOW MVFR OR EVEN IFR CIGS
ALONG WITH STRONG NORTHERLY WINDS ARE EXPECTED TO OVERSPREAD THE
TERMINALS. GUSTS INTO THE LOW TO MID 20 KT RANGE ARE POSSIBLE LATE
TONIGHT AND THROUGH MUCH OF THE DAY WEDNESDAY. CIGS SHOULD LIFT
DURING THE DAY WEDNESDAY AS WE HEAT UP...AND BY WEDNESDAY
AFTERNOON...ADDITIONAL SCATTERED SHOWERS ARE POSSIBLE.

BMD

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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 031122
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
622 AM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 12Z TAFS...

RIDGE AXIS IN PLACE ACROSS NORTHERN ILLINOIS AND NORTHWEST INDIANA
EARLY THIS MORNING WILL SHIFT SOUTH TODAY ALLOWING WESTERLY
WINDS TO PICK UP THROUGH THE DAY. GUSTS TO NEAR 20 KT ARE POSSIBLE
DURING THE AFTERNOON HOURS AS THE GRADIENT TIGHTENS AHEAD OF AN
APPROACHING COLD FRONT. EXPECT VFR CONDITIONS WITH MAINLY MID/HIGH
LEVEL CLOUD COVER TODAY. LATE THIS EVENING INTO THE EARLY
OVERNIGHT HOURS...A COLD FRONT WILL SWEEP ACROSS THE REGION.
EXPECT SCATTERED SHOWERS AND A PERHAPS A FEW THUNDERSTORMS TO BE
IN PLACE AHEAD OF THE FRONT LATE THIS EVENING. GIVEN THE OVERNIGHT
TIMING OF THE FRONT AND VERY WEAK INSTABILITY NOTED IN FORECAST
SOUNDINGS THIS EVENING...WILL NOT MENTION THUNDER IN THE TAFS FOR
NOW...THOUGH THEY REMAIN A SMALL POSSIBILITY. ONCE THE FRONT
SWEEPS THROUGH...PRECIP SHOULD TAPER AND LOW MVFR OR EVEN IFR CIGS
ALONG WITH STRONG NORTHERLY WINDS ARE EXPECTED TO OVERSPREAD THE
TERMINALS. GUSTS INTO THE LOW TO MID 20 KT RANGE ARE POSSIBLE LATE
TONIGHT AND THROUGH MUCH OF THE DAY WEDNESDAY. CIGS SHOULD LIFT
DURING THE DAY WEDNESDAY AS WE HEAT UP...AND BY WEDNESDAY
AFTERNOON...ADDITIONAL SCATTERED SHOWERS ARE POSSIBLE.

BMD

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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000
FXUS63 KLOT 030824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
324 AM CDT TUE MAY 3 2016

.SHORT TERM...
322 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

FORECAST FOCUS IS ON BRIEF WARM-UP TODAY...SHOWERS AND A FEW
THUNDERSTORMS TONIGHT WITH COLD FRONT PUSHING THROUGH THE
AREA...AND A RETURN TO COOL AND SHOWERY WEATHER WEDNESDAY.

BAGGY UPPER TROUGH REMAINS STUBBORNLY ACROSS THE MIDWEST THIS
MORNING...THOUGH THE WFO LOT CWA IS POSITIONED BETWEEN ONE SHORT
WAVE MOVING AWAY TO THE EAST ACROSS INDIANA AND OHIO...AND A
DEEPER WAVE WELL TO OUR NORTH ACROSS MANITOBA AND WESTERN ONTARIO.
WEAK HIGH PRESSURE RIDGING WAS AT THE SURFACE BETWEEN THESE TWO
FEATURES EARLY THIS MORNING. THIS RIDGE WILL DRIFT SOUTH OF THE
AREA TODAY ALLOWING WINDS TO BACK TO THE WEST...EVENTUALLY
BECOMING BREEZY AT 15-20 MPH THIS AFTERNOON IN RESPONSE TO
TIGHTENING OF THE SURFACE PRESSURE GRADIENT AHEAD OF THE SURFACE
LOW/COLD FRONTAL TROUGH ASSOCIATED WITH THE CANADIAN SHORT WAVE.
FORECAST SOUNDINGS FROM VARIOUS MODELS INDICATE FAIRLY DEEP MIXING
OF RELATIVELY DRY AIR MASS THIS AFTERNOON WHICH WILL BOOST TEMPS
INTO THE MID-UPPER 60S ACROSS THE AREA AND PERHAPS A 70 OR TWO
OVER NORTHWEST/NORTH CENTRAL IL. LIGHT WINDS EARLY IN THE DAY MAY
ALLOW A WEAK LAKE BREEZE TO DEVELOP RIGHT ALONG THE SHORE OF LAKE
MICHIGAN BY MID-DAY...THOUGH WOULD EXPECT GRADUALLY INCREASING
WEST WINDS THIS AFTERNOON TO PUSH THE BOUNDARY BACK OVER THE WATER
ESPECIALLY ALONG THE IL LAKE SHORE. DEEP MIXING SEEN IN WRF AND
GFS SOUNDINGS DOES GENERATE SOME WEAK CAPE...THOUGH SURFACE DEW
POINTS IN THE LOW 40S LOOK A BIT OVER-DONE AND ANTICIPATE A HIGH
BASED SCT-BKN CU/SC DECK WITHOUT PRECIP THROUGH THE AFTERNOON
HOURS.

THE CANADIAN SHORT WAVE DIGS QUICKLY ACROSS THE UPPER MIDWEST BY
EVENING...AND ACROSS THE FORECAST AREA OVERNIGHT WITH STRONG
FORCING ALOFT COINCIDENT WITH APPROACH OF SHARP SURFACE COLD
FRONT. RAPID HEIGHT FALLS AND MID-LEVEL COOLING YIELDS 700-500 MB
LAPSE RATES OF 7-7.5 C/KM WHICH YIELDS 200-300 J/KG OF MUCAPE PER
00Z WRF SOUNDINGS WHICH SHOULD SUPPORT EMBEDDED THUNDER
CONSIDERING STRONG FORCING AIDED BY JUXTAPOSITION OF DIVERGENT
LEFT EXIT REGION OF UPPER JET. TIMING VARIES A BIT BETWEEN VARIOUS
GUIDANCE MEMBERS...THOUGH SHOWERS/STORMS SHOULD BE MOVING INTO THE
AREA BY MID-LATE EVENING AND CLEARING THE SOUTHEAST PART OF THE
CWA BEFORE/NEAR SUNRISE WEDNESDAY MORNING. BEHIND THE
FRONT...WINDS WILL QUICKLY VEER NORTH AND BECOME GUSTY 25-30 MPH
WITH TEMPS DROPPING INTO THE 40S.

SHORT WAVE ENERGY WORKS TO CARVE OUT A DEEP UPPER TROUGH ACROSS
EASTERN NORTH AMERICA WEDNESDAY...WITH ANOTHER CLOSED UPPER LOW
DEVELOPING OVER THE WESTERN GREAT LAKES. CYCLONIC FLOW AND COOL
AIR ALOFT WILL SUPPORT MOSTLY CLOUDY/SHOWERY CONDITIONS THROUGH
THE DAY AS SEVERAL SMALLER VORTS ROTATE SOUTHWARD AROUND THE MAIN
MID-LEVEL CIRCULATION TO OUR EAST. THESE SHOWERS...EXTENSIVE CLOUD
COVER AND COOL...BLUSTERY NORTH WINDS WILL MAKE FOR ANOTHER CHILLY
SPRING DAY. TEMPS WILL LIKELY STRUGGLE TO EXCEED 50 DEGREES ALONG
THE LAKE MICHIGAN SHORE AND DOWNWIND INTO NORTHWEST INDIANA...AND
WILL LIKELY ONLY BE IN THE UPPER 50S/NEAR 60 FARTHER WEST ACROSS
NORTH CENTRAL IL. THE GOOD NEWS IS THAT THE UPPER FLOW PATTERN
WILL BE AMPLIFYING ACROSS THE CONTINENT...WITH STRONG UPPER
RIDGING DEVELOPING OVER THE CENTRAL CONUS HELPING TO NUDGE THE
DOWNSTREAM EASTERN TROUGH AND UPPER LOW AWAY FROM THE AREA BY THE
END OF THE SHORT TERM PERIOD. THIS ALLOWS WEAK SURFACE HIGH
PRESSURE TO SPREAD INTO THE MISSISSIPPI VALLEY AND WESTERN GREAT
LAKES REGION LATER WEDNESDAY NIGHT...WITH SHOWERS
ENDING...DECREASING CLOUDS AND DIMINISHING WINDS. THIS WILL
SUPPORT CHILLY OVERNIGHT TEMPS ESPECIALLY ACROSS NORTH CENTRAL AND
FAR NORTHERN IL...WHERE MINS IN THE MID-UPPER 30S ARE PROGGED BY
SUNRISE THURSDAY. HAVE ADDED A MENTION OF PATCHY FROST FOR THE
NORTHERN COUPLE OF TIERS OF ILLINOIS COUNTIES AWAY FROM THE CORE
OF THE CHICAGO METRO HEAT ISLAND TO THE PRE-DAWN HOURS OF THURSDAY
MORNING.

RATZER

&&

.LONG TERM...
322 AM CDT

THURSDAY THROUGH MONDAY...

THE EXTENDED PORTION OF THE FORECAST FEATURES A LATE-WEEK WARM-UP
FRIDAY INTO THE WEEKEND...THOUGH ANOTHER COLD FRONT WILL SAG
ACROSS THE AREA SATURDAY. THIS WILL TEMPER THE WARM-UP ALONG LAKE
MICHIGAN AND ACROSS FAR NORTHERN IL SUNDAY AND MONDAY AS WINDS
TURN OFF THE LAKE...AND WILL ALSO PRESENT THE POTENTIAL FOR
PERIODIC SHOWERS AND THUNDERSTORMS.

SURFACE HIGH PRESSURE RIDGING WILL SPREAD EAST INTO THE MIDWEST
ON THURSDAY AS THE UPPER TROUGH OVER THE EASTERN CONUS DRIFTS AWAY
TO THE EAST. NORTHERLY FLOW WILL INITIALLY MAINTAIN COOL
TEMPERATURES ESPECIALLY NEAR AND DOWNWIND OF LAKE MICHIGAN INTO
NORTHWEST INDIANA. SUNSHINE WILL RETURN HOWEVER...AS DRY/SINKING
AIR HELPS TO CLEAR OUT ANY LINGERING CLOUDS. AFTERNOON TEMPS
THURSDAY SHOULD CLIMB TO THE LOW-MID 60S ACROSS NORTHERN IL AWAY
FROM THE LAKE...WHILE HOLDING IN THE 50S ACROSS NORTHWEST INDIANA.
BETTER THINGS ARE IN STORE HOWEVER AS THE UPPER RIDGE OVER THE
CENTRAL CONUS BUILDS EAST THURSDAY NIGHT INTO FRIDAY...ALLOWING
TEMPERATURES TO SURGE WELL INTO THE 70S AND POSSIBLY TO THE 80
DEGREE MARK IN A FEW SPOTS ON FRIDAY. MODEST WEST TO SOUTHWEST
WINDS WILL LIKELY ALLOW A WEAK LAKE BREEZE TO DEVELOP BY
AFTERNOON...COOLING IMMEDIATE SHORE AREAS A BIT.

GUIDANCE HAS TRENDED FASTER WITH A SHORT WAVE TROUGH WHICH TOPS
THE RIDGE FRIDAY NIGHT INTO SATURDAY...INDUCING A SURFACE LOW
WHICH MOVES ACROSS THE NORTHERN LAKES AND TRAILS A COLD FRONT INTO
THE CWA DURING THE DAT SATURDAY. THUS WHILE TEMPS WILL ONCE AGAIN
REACH THE MID-UPPER 70S ACROSS WESTERN AND SOUTHERN PARTS OF THE
CWA SATURDAY...IT APPEARS THAT THE COLD FRONT WILL SHIFT WINDS
ONSHORE NEAR THE LAKE. WITH THIS SCENARIO IN MIND HAVE LIMITED
TEMPS TO THE MID-UPPER 60S ALONG THE IL SHORE AND MAY SEE FALLING
TEMPS NEAR THE LAKE SATURDAY AFTERNOON. INCREASED CLOUD COVER AND
SCATTERED SHOWERS AND THUNDERSTORMS WILL ALSO LIKELY ACCOMPANY THE
FRONT WHICH PUSHES INTO DOWNSTATE IL/IN SATURDAY NIGHT BEFORE
BECOMING STATIONARY. WEAK HIGH PRESSURE SPREADS ACROSS THE GREAT
LAKES NORTH OF THE FRONT AND PRODUCES COOLER ONSHORE WINDS SUNDAY
AND MONDAY...WITH THE ELEVATED BAROCLINIC ZONE NORTH OF THE
SURFACE FRONT CONTINUING TO BE A FOCUS FOR INCREASED CLOUD COVER
AND POTENTIAL SHOWERS/THUNDERSTORMS. BOTH DAYS WILL FEATURE A
CONTRAST IN TEMPERATURES FROM NEAR 60 UP NEAR WAUKEGAN TO THE LOW-
MID 70S ACROSS THE FAR SOUTHERN PARTS OF THE CWA. SUNDAY COULD BE
RELATIVELY DRY WITH THE FRONT WELL TO THE SOUTH... WITH POPS
INCREASING MONDAY AS THE FRONT BEGINS TO LIFT BACK NORTH AS A WARM
FRONT.

RATZER

&&

.AVIATION...
FOR THE 06Z TAFS...

RIDGE OF HIGH PRESSURE OVER THE REGION WILL BRING LIGHT WINDS AND
VFR CONDITIONS TO THE NORTHERN ILLINOIS AND NORTHWEST TERMINALS
OVERNIGHT. THE RIDGE AXIS WILL SHIFT TO OUR SOUTH AS A COLD FRONT
DROPS INTO WISCONSIN DURING THE DAY TUESDAY. WEST-SOUTHWEST WINDS
WILL OVERSPREAD THE TERMINALS AS THIS HAPPENS...BECOMING GUSTY
DURING THE MID TO LATE AFTERNOON. BY AROUND 06Z TUESDAY EVENING
THE FRONT SHOULD BE NEAR THE IL/WI STATE LINE...THOUGH THERE IS
STILL A 2-3 HOUR WINDOW OF UNCERTAINTY DUE TO VARIOUS TIMING
SOLUTIONS FROM THE MODELS. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED OUT AHEAD OF THE FRONT WHICH WILL CROSS
THE TERMINALS SOMETIME DURING THE EARLY OVERNIGHT HOURS. BEHIND
THE FRONT...WINDS WILL TURN NORTHERLY AND BECOME GUSTY ONCE
AGAIN...WITH GUSTS INTO THE LOW TO MID 20 KT RANGE POSSIBLE
TUESDAY NIGHT. LOW CIGS ARE EXPECTED TO OVERSPREAD THE REGION
BEHIND THE FRONT AS WELL...WITH LOW END MVFR CONDITIONS CURRENTLY
ANTICIPATED.

BMD

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 AM WEDNESDAY TO
     10 AM THURSDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...7 AM WEDNESDAY TO
     3 PM THURSDAY.

&&

$$

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000
FXUS63 KILX 030805
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
305 AM CDT TUE MAY 3 2016

.SHORT TERM...(Today)
ISSUED AT 304 AM CDT Tue May 3 2016

Another mostly quiet day is anticipated today across central and
southeast Illinois. Main concern revolves around cloud cover and if
there will be any precipitation.

Forecast area remains under the influence of a sheared trof axis
aloft, and weakly cyclonic flow at the surface. This scenario will
change little during the day today. A piece of energy within the
sheared trof is coming through the area at the moment with little
fanfare, although there are a few very weak/spotty radar returns.
However, have not seen recent reports of any of these returns
reaching the ground. Some additional sheared energy will impact the
area later today, but it will have very little instability to work
with. So think this feature should come through dry, but have
maintained a very low PoP in extreme SE IL where the instability may
be a bit better. Ultimately, based on forecast soundings & the items
mentioned above, think most of what we will see this afternoon is an
enhanced diurnal CU field and little more than a few sprinkles.

&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 304 AM CDT Tue May 3 2016

Latest models show little change in the projected upper air pattern
over the next several days. Current upper ridge already in place
with high pressure centered over southern Alberta. As the current
system over the central Plains and mid-Mississippi Valley drops
southward today, it will yield to an upper low that is now in
northwest Ontario and is projected to reach Lake Michigan on
Wednesday morning. Cooler conditions are expected for a few days as
a broad trough covers the eastern CONUS, but as the ridge shifts
eastward on Friday, significantly warmer conditions expected. Latest
blended guidance brings highs into the mid 70s over the western CWA
as early as Friday, and 80 degree readings over much of the forecast
area on Saturday.

Surface boundary associated with the Ontario system appears to be
picking up speed, and have increased PoP`s quite a bit and somewhat
faster than earlier, with likely PoP`s over areas north of Peoria as
early as late evening. Also went with a period of 60% PoP`s over
east central Illinois after midnight. The window for rain looks to
only last about a couple hours at any given location, given the
speed of this system. Some steeper mid-level lapse rates favor a few
rumbles of thunder as well. Have maintained some chance PoP`s over
the eastern half of the forecast area as well on Wednesday due to
the arrival of the upper low.

Weekend system starting to come into a little better agreement in
the longer range models. Both the GFS and ECMWF settle a quasi-
stationary front over central Illinois by Saturday afternoon,
lingering in the general area through Sunday. How fast this boundary
retreats northward is more in question, with our region caught
between the southern jet stream being steered south of the upper low
over the 4-corners region, and the northern jet stream coming
through the Great Lakes. Thus, once precipitation chances develop
through the day Saturday, chance PoP`s will remain in the forecast
into Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1124 PM CDT Mon May 2 2016

The clearing line has advanced south late this evening, with no
ceiling anymore at PIA, BMI and CMI. VFR ceilings remain at SPI
and DEC at 7-8K FT, but even those ceilings should erode shortly
after 06z as the upper shortwave shifts east of the region and
drier air continues to work in from the north. Scattered cumulus
will develop by mid morning and may periodically go broken with
bases remaining above MVFR levels through afternoon. A sprinkle or
two can not be ruled out during the flare-up of cumulus during the
day, but most areas will remain dry.

Winds will become light and variable tonight as a weak high
pressure ridge shifts into Illinois overnight. Winds tomorrow will
veer to the WNW and climb to 10-13 kts by mid-afternoon on Tuesday,
ahead of a cold front approaching from the north. Winds will
weaken below 10kt Tue eve as they back to the west-southwest.

Rain showers could develop near the northern terminals of PIA,
BMI, and CMI late in this TAF period, but the better chances will
hold off until after 06z Tuesday night.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...Shimon




000
FXUS63 KLOT 030723
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
223 AM CDT TUE MAY 3 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTH
CENTRAL IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE
LOWER 40S. CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE
AREA...WITH SOME DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA.
JUST BEYOND PEAK HEATING OF THE AFTERNOON THE DIURNAL CUMULUS
SHOULD BEGIN TO DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING
TO AROUND 5 TO 10 MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE
AREA WILL KEEP WINDS LIGHT AND VARIABLE OVERNIGHT...WHICH COULD
ALLOW TEMPERATURES TO STEADILY RADIATE INTO THE LOWER 40S. HOWEVER
AREAS THAT HAVE HAD DEW POINTS THIS AFTERNOON FALL INTO THE MIDDLE
30S...TEMPS TONIGHT COULD DIP INTO THE UPPER 30S BETWEEN ROCKFORD
AND WAUKEGAN DOWN TO DEKALB. HAVE INCLUDED PATCHY FROST WORDING
OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 06Z TAFS...

RIDGE OF HIGH PRESSURE OVER THE REGION WILL BRING LIGHT WINDS AND
VFR CONDITIONS TO THE NORTHERN ILLINOIS AND NORTHWEST TERMINALS
OVERNIGHT. THE RIDGE AXIS WILL SHIFT TO OUR SOUTH AS A COLD FRONT
DROPS INTO WISCONSIN DURING THE DAY TUESDAY. WEST-SOUTHWEST WINDS
WILL OVERSPREAD THE TERMINALS AS THIS HAPPENS...BECOMING GUSTY
DURING THE MID TO LATE AFTERNOON. BY AROUND 06Z TUESDAY EVENING
THE FRONT SHOULD BE NEAR THE IL/WI STATE LINE...THOUGH THERE IS
STILL A 2-3 HOUR WINDOW OF UNCERTAINTY DUE TO VARIOUS TIMING
SOLUTIONS FROM THE MODELS. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED OUT AHEAD OF THE FRONT WHICH WILL CROSS
THE TERMINALS SOMETIME DURING THE EARLY OVERNIGHT HOURS. BEHIND
THE FRONT...WINDS WILL TURN NORTHERLY AND BECOME GUSTY ONCE
AGAIN...WITH GUSTS INTO THE LOW TO MID 20 KT RANGE POSSIBLE
TUESDAY NIGHT. LOW CIGS ARE EXPECTED TO OVERSPREAD THE REGION
BEHIND THE FRONT AS WELL...WITH LOW END MVFR CONDITIONS CURRENTLY
ANTICIPATED.

BMD

&&

.MARINE...
221 AM CDT

HIGH PRESSURE IS OVER THE REGION EARLY THIS MORNING PROVIDING
LIGHT FLOW ACROSS LAKE MICHIGAN...HOWEVER A COLD FRONT IS EXPECTED
TO MOVE SOUTH ACROSS LAKE MICHIGAN LATE THIS EVENING AND OVERNIGHT
BRINGING NEAR GALE FORCE NORTHERLY WINDS. SOUTHWEST FLOW WILL
INCREASE THROUGH THE DAY TODAY AHEAD OF THE FRONT. SHOWERS AND A
FEW THUNDERSTORMS ARE ALSO EXPECTED TO OCCUR IMMEDIATELY ALONG AND
AHEAD OF THE FRONT...THEN WINDS WILL TURN NORTHERLY AND INCREASE
WITH GUSTS TO AROUND 30 KT EXPECTED BEHIND THE FRONT. WINDS WILL
REMAIN STRONG THROUGH THE DAY WEDNESDAY...THEN GRADUALLY COME DOWN
THROUGH THE DAY THURSDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE
NEEDED FOR THE ILLINOIS AND INDIANA NEARSHORE WATERS THROUGH THIS
TIMEFRAME. WINDS DIMINISH ENOUGH FOR LAKE BREEZES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE ONCE AGAIN MOVES OVERHEAD...THEN
SOUTHWESTERLY FLOW RETURNS THURSDAY NIGHT AS THE RIDGE AXIS SAGS
SOUTHEAST OF THE LAKE. ANOTHER COLD FRONT IS EXPECTED TO PUSH
ACROSS LAKE MICHIGAN OVER THE WEEKEND.

BMD

&&

.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:
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000
FXUS63 KLOT 030522
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1222 AM CDT TUE MAY 3 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTH
CENTRAL IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE
LOWER 40S. CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE
AREA...WITH SOME DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA.
JUST BEYOND PEAK HEATING OF THE AFTERNOON THE DIURNAL CUMULUS
SHOULD BEGIN TO DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING
TO AROUND 5 TO 10 MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE
AREA WILL KEEP WINDS LIGHT AND VARIABLE OVERNIGHT...WHICH COULD
ALLOW TEMPERATURES TO STEADILY RADIATE INTO THE LOWER 40S. HOWEVER
AREAS THAT HAVE HAD DEW POINTS THIS AFTERNOON FALL INTO THE MIDDLE
30S...TEMPS TONIGHT COULD DIP INTO THE UPPER 30S BETWEEN ROCKFORD
AND WAUKEGAN DOWN TO DEKALB. HAVE INCLUDED PATCHY FROST WORDING
OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 06Z TAFS...

RIDGE OF HIGH PRESSURE OVER THE REGION WILL BRING LIGHT WINDS AND
VFR CONDITIONS TO THE NORTHERN ILLINOIS AND NORTHWEST TERMINALS
OVERNIGHT. THE RIDGE AXIS WILL SHIFT TO OUR SOUTH AS A COLD FRONT
DROPS INTO WISCONSIN DURING THE DAY TUESDAY. WEST-SOUTHWEST WINDS
WILL OVERSPREAD THE TERMINALS AS THIS HAPPENS...BECOMING GUSTY
DURING THE MID TO LATE AFTERNOON. BY AROUND 06Z TUESDAY EVENING
THE FRONT SHOULD BE NEAR THE IL/WI STATE LINE...THOUGH THERE IS
STILL A 2-3 HOUR WINDOW OF UNCERTAINTY DUE TO VARIOUS TIMING
SOLUTIONS FROM THE MODELS. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED OUT AHEAD OF THE FRONT WHICH WILL CROSS
THE TERMINALS SOMETIME DURING THE EARLY OVERNIGHT HOURS. BEHIND
THE FRONT...WINDS WILL TURN NORTHERLY AND BECOME GUSTY ONCE
AGAIN...WITH GUSTS INTO THE LOW TO MID 20 KT RANGE POSSIBLE
TUESDAY NIGHT. LOW CIGS ARE EXPECTED TO OVERSPREAD THE REGION
BEHIND THE FRONT AS WELL...WITH LOW END MVFR CONDITIONS CURRENTLY
ANTICIPATED.

BMD

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

.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 030424
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1124 PM CDT MON MAY 2 2016

.UPDATE...
Issued at 900 PM CDT Mon May 2 2016

The upper shortwave departing to the east along with the arrival
of dry air from near Lake Michigan has allowed clouds to clear out
in our northeast counties early this evening. Farther NW of
Peoria and Galesburg where diurnal cumulus were more prevalent,
clouds are also decreasing in coverage in general. HRRR output
remains very optimistic that clearing with push quickly east
across our forecast area by sunrise Tuesday. Have sped up the
clearing in the forecast for tonight. Will monitor trends closely,
as night-time clearing can be more troublesome than daytime
clearing trends, due to subsidence inversions and decoupling of
low level winds.

Spotty showers or sprinkles will still be possible in any cloud
cover as the surface trough slowly drifts south toward southern
IL. Will keep isolated rain chances going in the south, with
diminishing coverage from NW to SE the rest of the night.

Have trimmed a degree or two from the overnight lows to account
for possible earlier clearing. Lower 40s appear likely in
locations north of I-72, especially in a areas where clearing has
already developed this evening. Lows should bottom out in the
upper 40s southeast of I-70 where clouds linger the longest.

Updated forecast info is already available.

&&

.SHORT TERM...(Tonight)
ISSUED AT 313 PM CDT Mon May 2 2016

Main short-term forecast concern will be timing of potential
clearing tonight.  While the main surface boundary has dropped south
of the Ohio River, a trailing upper trough extending from Wisconsin
southwestward to Kansas has provided enough synoptic lift to produce
widespread overcast conditions today.  Visible satellite loops show
the low cloud cover pivoting southward on the back side of a subtle
upper wave currently over central Illinois.  As this feature tracks
further eastward, think clouds will gradually dissipate/clear the
Illinois River Valley this evening.  Due to trajectory of cloud
cover and relatively light flow, clouds will likely hold throughout
the entire night along/east of the I-57 corridor.  May see a few
isolated light showers this evening: however, most locations will
remain dry.  Overnight low temperatures will range from the lower
40s northwest of the Illinois River where clearing will occur
earliest...to around 50 degrees far southeast around Robinson and
Lawrenceville.

.LONG TERM...(Tuesday through Monday)
ISSUED AT 313 PM CDT Mon May 2 2016

Cyclonic flow will continue over the area through Wed. A lull in the
pcpn chances will be seen Tuesday as CWA will be in between troughs
rotating through the area. However, will still keep a slight chance
of showers in the east and southeast Tuesday due to a 500mb trough
moving south through the area...just without any surface reflection.
A bigger and more dominate trough will drop into the area Tue night
through Wed. Pcpn will start in the north Tue evening and then move
south through the area the remainder of the night and then in the
east on Wed. Isolated thunder will also be possible given greater
lapse rates due to cold 500mb temps moving over the area in
association with the upper level low. The pcpn will move off to the
east Wed night, which will allow high pressure to build into the
region with dry weather and slowly warming temps for Thur through
Fri. This surface high pressure ridge will get flattened by the end
of the week as another frontal system drops into the area for the
weekend. With warm and moist air being advected into the area Friday
and Saturday, will be plenty of instability for thunderstorms along
and ahead of the front Sat night through Monday. The front does seem
to hang around the area through the weekend since there will be an
upper level low just east of the US and another one over the
southwest US.

Temps will remain below normal most of the week, but begin to warm
back up as the high pressure that builds in Thursday moves off to
the east, bringing back southerly winds. The warmer temps will
continue through the weekend and into the beginning of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1124 PM CDT Mon May 2 2016

The clearing line has advanced south late this evening, with no
ceiling anymore at PIA, BMI and CMI. VFR ceilings remain at SPI
and DEC at 7-8K FT, but even those ceilings should erode shortly
after 06z as the upper shortwave shifts east of the region and
drier air continues to work in from the north. Scattered cumulus
will develop by mid morning and may periodically go broken with
bases remaining above MVFR levels through afternoon. A sprinkle or
two can not be ruled out during the flare-up of cumulus during the
day, but most areas will remain dry.

Winds will become light and variable tonight as a weak high
pressure ridge shifts into Illinois overnight. Winds tomorrow will
veer to the WNW and climb to 10-13 kts by mid-afternoon on Tuesday,
ahead of a cold front approaching from the north. Winds will
weaken below 10kt Tue eve as they back to the west-southwest.

Rain showers could develop near the northern terminals of PIA,
BMI, and CMI late in this TAF period, but the better chances will
hold off until after 06z Tuesday night.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Shimon
SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Shimon




000
FXUS63 KILX 030424
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1124 PM CDT MON MAY 2 2016

.UPDATE...
Issued at 900 PM CDT Mon May 2 2016

The upper shortwave departing to the east along with the arrival
of dry air from near Lake Michigan has allowed clouds to clear out
in our northeast counties early this evening. Farther NW of
Peoria and Galesburg where diurnal cumulus were more prevalent,
clouds are also decreasing in coverage in general. HRRR output
remains very optimistic that clearing with push quickly east
across our forecast area by sunrise Tuesday. Have sped up the
clearing in the forecast for tonight. Will monitor trends closely,
as night-time clearing can be more troublesome than daytime
clearing trends, due to subsidence inversions and decoupling of
low level winds.

Spotty showers or sprinkles will still be possible in any cloud
cover as the surface trough slowly drifts south toward southern
IL. Will keep isolated rain chances going in the south, with
diminishing coverage from NW to SE the rest of the night.

Have trimmed a degree or two from the overnight lows to account
for possible earlier clearing. Lower 40s appear likely in
locations north of I-72, especially in a areas where clearing has
already developed this evening. Lows should bottom out in the
upper 40s southeast of I-70 where clouds linger the longest.

Updated forecast info is already available.

&&

.SHORT TERM...(Tonight)
ISSUED AT 313 PM CDT Mon May 2 2016

Main short-term forecast concern will be timing of potential
clearing tonight.  While the main surface boundary has dropped south
of the Ohio River, a trailing upper trough extending from Wisconsin
southwestward to Kansas has provided enough synoptic lift to produce
widespread overcast conditions today.  Visible satellite loops show
the low cloud cover pivoting southward on the back side of a subtle
upper wave currently over central Illinois.  As this feature tracks
further eastward, think clouds will gradually dissipate/clear the
Illinois River Valley this evening.  Due to trajectory of cloud
cover and relatively light flow, clouds will likely hold throughout
the entire night along/east of the I-57 corridor.  May see a few
isolated light showers this evening: however, most locations will
remain dry.  Overnight low temperatures will range from the lower
40s northwest of the Illinois River where clearing will occur
earliest...to around 50 degrees far southeast around Robinson and
Lawrenceville.

.LONG TERM...(Tuesday through Monday)
ISSUED AT 313 PM CDT Mon May 2 2016

Cyclonic flow will continue over the area through Wed. A lull in the
pcpn chances will be seen Tuesday as CWA will be in between troughs
rotating through the area. However, will still keep a slight chance
of showers in the east and southeast Tuesday due to a 500mb trough
moving south through the area...just without any surface reflection.
A bigger and more dominate trough will drop into the area Tue night
through Wed. Pcpn will start in the north Tue evening and then move
south through the area the remainder of the night and then in the
east on Wed. Isolated thunder will also be possible given greater
lapse rates due to cold 500mb temps moving over the area in
association with the upper level low. The pcpn will move off to the
east Wed night, which will allow high pressure to build into the
region with dry weather and slowly warming temps for Thur through
Fri. This surface high pressure ridge will get flattened by the end
of the week as another frontal system drops into the area for the
weekend. With warm and moist air being advected into the area Friday
and Saturday, will be plenty of instability for thunderstorms along
and ahead of the front Sat night through Monday. The front does seem
to hang around the area through the weekend since there will be an
upper level low just east of the US and another one over the
southwest US.

Temps will remain below normal most of the week, but begin to warm
back up as the high pressure that builds in Thursday moves off to
the east, bringing back southerly winds. The warmer temps will
continue through the weekend and into the beginning of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1124 PM CDT Mon May 2 2016

The clearing line has advanced south late this evening, with no
ceiling anymore at PIA, BMI and CMI. VFR ceilings remain at SPI
and DEC at 7-8K FT, but even those ceilings should erode shortly
after 06z as the upper shortwave shifts east of the region and
drier air continues to work in from the north. Scattered cumulus
will develop by mid morning and may periodically go broken with
bases remaining above MVFR levels through afternoon. A sprinkle or
two can not be ruled out during the flare-up of cumulus during the
day, but most areas will remain dry.

Winds will become light and variable tonight as a weak high
pressure ridge shifts into Illinois overnight. Winds tomorrow will
veer to the WNW and climb to 10-13 kts by mid-afternoon on Tuesday,
ahead of a cold front approaching from the north. Winds will
weaken below 10kt Tue eve as they back to the west-southwest.

Rain showers could develop near the northern terminals of PIA,
BMI, and CMI late in this TAF period, but the better chances will
hold off until after 06z Tuesday night.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Shimon
SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Shimon




000
FXUS63 KILX 030206
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
906 PM CDT MON MAY 2 2016

.UPDATE...
Issued at 900 PM CDT Mon May 2 2016

The upper shortwave departing to the east along with the arrival
of dry air from near Lake Michigan has allowed clouds to clear out
in our northeast counties early this evening. Farther NW of
Peoria and Galesburg where diurnal cumulus were more prevalent,
clouds are also decreasing in coverage in general. HRRR output
remains very optimistic that clearing with push quickly east
across our forecast area by sunrise Tuesday. Have sped up the
clearing in the forecast for tonight. Will monitor trends closely,
as night-time clearing can be more troublesome than daytime
clearing trends, due to subsidence inversions and decoupling of
low level winds.

Spotty showers or sprinkles will still be possible in any cloud
cover as the surface trough slowly drifts south toward southern
IL. Will keep isolated rain chances going in the south, with
diminishing coverage from NW to SE the rest of the night.

Have trimmed a degree or two from the overnight lows to account
for possible earlier clearing. Lower 40s appear likely in
locations north of I-72, especially in a areas where clearing has
already developed this evening. Lows should bottom out in the
upper 40s southeast of I-70 where clouds linger the longest.

Updated forecast info is already available.

&&

.SHORT TERM...(Tonight)
ISSUED AT 313 PM CDT Mon May 2 2016

Main short-term forecast concern will be timing of potential
clearing tonight.  While the main surface boundary has dropped south
of the Ohio River, a trailing upper trough extending from Wisconsin
southwestward to Kansas has provided enough synoptic lift to produce
widespread overcast conditions today.  Visible satellite loops show
the low cloud cover pivoting southward on the back side of a subtle
upper wave currently over central Illinois.  As this feature tracks
further eastward, think clouds will gradually dissipate/clear the
Illinois River Valley this evening.  Due to trajectory of cloud
cover and relatively light flow, clouds will likely hold throughout
the entire night along/east of the I-57 corridor.  May see a few
isolated light showers this evening: however, most locations will
remain dry.  Overnight low temperatures will range from the lower
40s northwest of the Illinois River where clearing will occur
earliest...to around 50 degrees far southeast around Robinson and
Lawrenceville.

.LONG TERM...(Tuesday through Monday)
ISSUED AT 313 PM CDT Mon May 2 2016

Cyclonic flow will continue over the area through Wed. A lull in the
pcpn chances will be seen Tuesday as CWA will be in between troughs
rotating through the area. However, will still keep a slight chance
of showers in the east and southeast Tuesday due to a 500mb trough
moving south through the area...just without any surface reflection.
A bigger and more dominate trough will drop into the area Tue night
through Wed. Pcpn will start in the north Tue evening and then move
south through the area the remainder of the night and then in the
east on Wed. Isolated thunder will also be possible given greater
lapse rates due to cold 500mb temps moving over the area in
association with the upper level low. The pcpn will move off to the
east Wed night, which will allow high pressure to build into the
region with dry weather and slowly warming temps for Thur through
Fri. This surface high pressure ridge will get flattened by the end
of the week as another frontal system drops into the area for the
weekend. With warm and moist air being advected into the area Friday
and Saturday, will be plenty of instability for thunderstorms along
and ahead of the front Sat night through Monday. The front does seem
to hang around the area through the weekend since there will be an
upper level low just east of the US and another one over the
southwest US.

Temps will remain below normal most of the week, but begin to warm
back up as the high pressure that builds in Thursday moves off to
the east, bringing back southerly winds. The warmer temps will
continue through the weekend and into the beginning of next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 618 PM CDT Mon May 2 2016

Ceilings have lifted to VFR levels by late afternoon, and should
erode tonight as a weak shortwave shifts east of the region and
drier air works in from the north. Scattered cumulus will develop
by mid morning and may periodically go broken with bases
remaining above MVFR levels through afternoon. A weak high
pressure ridge will bring light/variable winds overnight before
veering to the WNW near/under 10 kts on Tuesday, ahead of a cold
front approaching from the north.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Shimon
SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...25




000
FXUS63 KLOT 030003
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
656 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 00Z TAFS...

CONCERNS/HIGHLIGHTS FOR THE 0Z TAFS INCLUDE
-WINDS TURNING WESTERLY WITH GUSTS IN THE UPPER TEENS POSSIBLE IN
THE AFTERNOON.
-SHOWERS AT THE END OF THE 30 HR ORD TAF CYCLE...WITH A
THUNDERSTORM NOT OUT OF THE QUESTION.

VFR CIGS WITH BASES OF 7000-8000 FEET WILL ERODE QUICKLY AFTER
SUNSET. ANOTHER POCKET OF LOWER VFR CIGS ACROSS THE LAKE AND
ADJACENT CHICAGOLAND TERMINALS...WITH BASES AROUND 5000-6000 FEET
IN NE IL...AND 3000-4000 FEET IN NORTHWEST INDIANA...WILL ERODE
BUT WILL TAKE A FEW HOURS TO DO SO.

THE SURFACE RIDGE AXIS WILL BUILD OVERHEAD TONIGHT...THUS A QUICK
COLLAPSE TO THE EAST WIND IS EXPECTED WITH A PERIOD OF
LIGHT/VARIABLE WINDS TURNING LIGHT WESTERLY OVERNIGHT. AN UPPER
LEVEL DISTURBANCE WILL BUILD SOUTH LATER TUESDAY AND ESPECIALLY
TUESDAY EVENING. WINDS WILL INCREASE FROM THE WEST...THEN SHIFT TO
SOUTHWEST AHEAD OF THE DISTURBANCE. AN ISOLATED SHOWER CANNOT BE
RULED OUT IN THE AFTERNOON...BUT THERE WILL BE A PERIOD OF SHOWERS
MID TO LATE EVENING TUESDAY INTO TUESDAY NIGHT. MODEL CAPE VALUES
ARE LOW WHICH WOULD SUGGEST A NON-ZERO THUNDER THREAT...AND
FORECAST SOUNDINGS DO SHOW THE EROSION OF A CAP THROUGH THE
EVENING...BUT CONFIDENCE IS STILL TOO LOW TO INCLUDE IN THE TAF AT
THIS DISTANCE. THE THUNDER TIMING IF IT WOULD OCCUR WOULD BE MOST
FAVORED IN THE 3Z-6Z TIME FRAME.

KMD

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

.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 030003
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
656 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 00Z TAFS...

CONCERNS/HIGHLIGHTS FOR THE 0Z TAFS INCLUDE
-WINDS TURNING WESTERLY WITH GUSTS IN THE UPPER TEENS POSSIBLE IN
THE AFTERNOON.
-SHOWERS AT THE END OF THE 30 HR ORD TAF CYCLE...WITH A
THUNDERSTORM NOT OUT OF THE QUESTION.

VFR CIGS WITH BASES OF 7000-8000 FEET WILL ERODE QUICKLY AFTER
SUNSET. ANOTHER POCKET OF LOWER VFR CIGS ACROSS THE LAKE AND
ADJACENT CHICAGOLAND TERMINALS...WITH BASES AROUND 5000-6000 FEET
IN NE IL...AND 3000-4000 FEET IN NORTHWEST INDIANA...WILL ERODE
BUT WILL TAKE A FEW HOURS TO DO SO.

THE SURFACE RIDGE AXIS WILL BUILD OVERHEAD TONIGHT...THUS A QUICK
COLLAPSE TO THE EAST WIND IS EXPECTED WITH A PERIOD OF
LIGHT/VARIABLE WINDS TURNING LIGHT WESTERLY OVERNIGHT. AN UPPER
LEVEL DISTURBANCE WILL BUILD SOUTH LATER TUESDAY AND ESPECIALLY
TUESDAY EVENING. WINDS WILL INCREASE FROM THE WEST...THEN SHIFT TO
SOUTHWEST AHEAD OF THE DISTURBANCE. AN ISOLATED SHOWER CANNOT BE
RULED OUT IN THE AFTERNOON...BUT THERE WILL BE A PERIOD OF SHOWERS
MID TO LATE EVENING TUESDAY INTO TUESDAY NIGHT. MODEL CAPE VALUES
ARE LOW WHICH WOULD SUGGEST A NON-ZERO THUNDER THREAT...AND
FORECAST SOUNDINGS DO SHOW THE EROSION OF A CAP THROUGH THE
EVENING...BUT CONFIDENCE IS STILL TOO LOW TO INCLUDE IN THE TAF AT
THIS DISTANCE. THE THUNDER TIMING IF IT WOULD OCCUR WOULD BE MOST
FAVORED IN THE 3Z-6Z TIME FRAME.

KMD

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

.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 022356
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
656 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 00Z TAFS...

CONCERNS/HIGHLIGHTS FOR THE 0Z TAFS INCLUDE
-WINDS TURNING WESTERLY WITH GUSTS IN THE UPPER TEENS POSSIBLE IN
THE AFTERNOON.
-SHOWERS AT THE END OF THE 30 HR ORD TAF CYCLE...WITH A
THUNDERSTORM NOT OUT OF THE QUESTION.

VFR CIGS WITH BASES OF 7000-8000 FEET WILL ERODE QUICKLY AFTER
SUNSET. ANOTHER POCKET OF LOWER VFR CIGS ACROSS THE LAKE AND
ADJACENT CHICAGOLAND TERMINALS...WITH BASES AROUND 5000-6000 FEET
IN NE IL...AND 3000-4000 FEET IN NORTHWEST INDIANA...WILL ERODE
BUT WILL TAKE A FEW HOURS TO DO SO.

THE SURFACE RIDGE AXIS WILL BUILD OVERHEAD TONIGHT...THUS A QUICK
COLLAPSE TO THE EAST WIND IS EXPECTED WITH A PERIOD OF
LIGHT/VARIABLE WINDS TURNING LIGHT WESTERLY OVERNIGHT. AN UPPER
LEVEL DISTURBANCE WILL BUILD SOUTH LATER TUESDAY AND ESPECIALLY
TUESDAY EVENING. WINDS WILL INCREASE FROM THE WEST...THEN SHIFT TO
SOUTHWEST AHEAD OF THE DISTURBANCE. AN ISOLATED SHOWER CANNOT BE
RULED OUT IN THE AFTERNOON...BUT THERE WILL BE A PERIOD OF SHOWERS
MID TO LATE EVENING TUESDAY INTO TUESDAY NIGHT. MODEL CAPE VALUES
ARE LOW WHICH WOULD SUGGEST A NON-ZERO THUNDER THREAT...AND
FORECAST SOUNDINGS DO SHOW THE EROSION OF A CAP THROUGH THE
EVENING...BUT CONFIDENCE IS STILL TOO LOW TO INCLUDE IN THE TAF
AT THIS DISTANCE...EVEN AT THE PROB30 LEVEL.

KMD

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

.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 022356
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
656 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 00Z TAFS...

CONCERNS/HIGHLIGHTS FOR THE 0Z TAFS INCLUDE
-WINDS TURNING WESTERLY WITH GUSTS IN THE UPPER TEENS POSSIBLE IN
THE AFTERNOON.
-SHOWERS AT THE END OF THE 30 HR ORD TAF CYCLE...WITH A
THUNDERSTORM NOT OUT OF THE QUESTION.

VFR CIGS WITH BASES OF 7000-8000 FEET WILL ERODE QUICKLY AFTER
SUNSET. ANOTHER POCKET OF LOWER VFR CIGS ACROSS THE LAKE AND
ADJACENT CHICAGOLAND TERMINALS...WITH BASES AROUND 5000-6000 FEET
IN NE IL...AND 3000-4000 FEET IN NORTHWEST INDIANA...WILL ERODE
BUT WILL TAKE A FEW HOURS TO DO SO.

THE SURFACE RIDGE AXIS WILL BUILD OVERHEAD TONIGHT...THUS A QUICK
COLLAPSE TO THE EAST WIND IS EXPECTED WITH A PERIOD OF
LIGHT/VARIABLE WINDS TURNING LIGHT WESTERLY OVERNIGHT. AN UPPER
LEVEL DISTURBANCE WILL BUILD SOUTH LATER TUESDAY AND ESPECIALLY
TUESDAY EVENING. WINDS WILL INCREASE FROM THE WEST...THEN SHIFT TO
SOUTHWEST AHEAD OF THE DISTURBANCE. AN ISOLATED SHOWER CANNOT BE
RULED OUT IN THE AFTERNOON...BUT THERE WILL BE A PERIOD OF SHOWERS
MID TO LATE EVENING TUESDAY INTO TUESDAY NIGHT. MODEL CAPE VALUES
ARE LOW WHICH WOULD SUGGEST A NON-ZERO THUNDER THREAT...AND
FORECAST SOUNDINGS DO SHOW THE EROSION OF A CAP THROUGH THE
EVENING...BUT CONFIDENCE IS STILL TOO LOW TO INCLUDE IN THE TAF
AT THIS DISTANCE...EVEN AT THE PROB30 LEVEL.

KMD

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

.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 022318
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
618 PM CDT MON MAY 2 2016

.SHORT TERM...(Tonight)
ISSUED AT 313 PM CDT Mon May 2 2016

Main short-term forecast concern will be timing of potential
clearing tonight.  While the main surface boundary has dropped south
of the Ohio River, a trailing upper trough extending from Wisconsin
southwestward to Kansas has provided enough synoptic lift to produce
widespread overcast conditions today.  Visible satellite loops show
the low cloud cover pivoting southward on the back side of a subtle
upper wave currently over central Illinois.  As this feature tracks
further eastward, think clouds will gradually dissipate/clear the
Illinois River Valley this evening.  Due to trajectory of cloud
cover and relatively light flow, clouds will likely hold throughout
the entire night along/east of the I-57 corridor.  May see a few
isolated light showers this evening: however, most locations will
remain dry.  Overnight low temperatures will range from the lower
40s northwest of the Illinois River where clearing will occur
earliest...to around 50 degrees far southeast around Robinson and
Lawrenceville.

.LONG TERM...(Tuesday through Monday)
ISSUED AT 313 PM CDT Mon May 2 2016

Cyclonic flow will continue over the area through Wed. A lull in the
pcpn chances will be seen Tuesday as CWA will be in between troughs
rotating through the area. However, will still keep a slight chance
of showers in the east and southeast Tuesday due to a 500mb trough
moving south through the area...just without any surface reflection.
A bigger and more dominate trough will drop into the area Tue night
through Wed. Pcpn will start in the north Tue evening and then move
south through the area the remainder of the night and then in the
east on Wed. Isolated thunder will also be possible given greater
lapse rates due to cold 500mb temps moving over the area in
association with the upper level low. The pcpn will move off to the
east Wed night, which will allow high pressure to build into the
region with dry weather and slowly warming temps for Thur through
Fri. This surface high pressure ridge will get flattened by the end
of the week as another frontal system drops into the area for the
weekend. With warm and moist air being advected into the area Friday
and Saturday, will be plenty of instability for thunderstorms along
and ahead of the front Sat night through Monday. The front does seem
to hang around the area through the weekend since there will be an
upper level low just east of the US and another one over the
southwest US.

Temps will remain below normal most of the week, but begin to warm
back up as the high pressure that builds in Thursday moves off to
the east, bringing back southerly winds. The warmer temps will
continue through the weekend and into the beginning of next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 618 PM CDT Mon May 2 2016

Ceilings have lifted to VFR levels by late afternoon, and should
erode tonight as a weak shortwave shifts east of the region and
drier air works in from the north. Scattered cumulus will develop
by mid morning and may periodically go broken with bases
remaining above MVFR levels through afternoon. A weak high
pressure ridge will bring light/variable winds overnight before
veering to the WNW near/under 10 kts on Tuesday, ahead of a cold
front approaching from the north.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...25




000
FXUS63 KILX 022318
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
618 PM CDT MON MAY 2 2016

.SHORT TERM...(Tonight)
ISSUED AT 313 PM CDT Mon May 2 2016

Main short-term forecast concern will be timing of potential
clearing tonight.  While the main surface boundary has dropped south
of the Ohio River, a trailing upper trough extending from Wisconsin
southwestward to Kansas has provided enough synoptic lift to produce
widespread overcast conditions today.  Visible satellite loops show
the low cloud cover pivoting southward on the back side of a subtle
upper wave currently over central Illinois.  As this feature tracks
further eastward, think clouds will gradually dissipate/clear the
Illinois River Valley this evening.  Due to trajectory of cloud
cover and relatively light flow, clouds will likely hold throughout
the entire night along/east of the I-57 corridor.  May see a few
isolated light showers this evening: however, most locations will
remain dry.  Overnight low temperatures will range from the lower
40s northwest of the Illinois River where clearing will occur
earliest...to around 50 degrees far southeast around Robinson and
Lawrenceville.

.LONG TERM...(Tuesday through Monday)
ISSUED AT 313 PM CDT Mon May 2 2016

Cyclonic flow will continue over the area through Wed. A lull in the
pcpn chances will be seen Tuesday as CWA will be in between troughs
rotating through the area. However, will still keep a slight chance
of showers in the east and southeast Tuesday due to a 500mb trough
moving south through the area...just without any surface reflection.
A bigger and more dominate trough will drop into the area Tue night
through Wed. Pcpn will start in the north Tue evening and then move
south through the area the remainder of the night and then in the
east on Wed. Isolated thunder will also be possible given greater
lapse rates due to cold 500mb temps moving over the area in
association with the upper level low. The pcpn will move off to the
east Wed night, which will allow high pressure to build into the
region with dry weather and slowly warming temps for Thur through
Fri. This surface high pressure ridge will get flattened by the end
of the week as another frontal system drops into the area for the
weekend. With warm and moist air being advected into the area Friday
and Saturday, will be plenty of instability for thunderstorms along
and ahead of the front Sat night through Monday. The front does seem
to hang around the area through the weekend since there will be an
upper level low just east of the US and another one over the
southwest US.

Temps will remain below normal most of the week, but begin to warm
back up as the high pressure that builds in Thursday moves off to
the east, bringing back southerly winds. The warmer temps will
continue through the weekend and into the beginning of next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 618 PM CDT Mon May 2 2016

Ceilings have lifted to VFR levels by late afternoon, and should
erode tonight as a weak shortwave shifts east of the region and
drier air works in from the north. Scattered cumulus will develop
by mid morning and may periodically go broken with bases
remaining above MVFR levels through afternoon. A weak high
pressure ridge will bring light/variable winds overnight before
veering to the WNW near/under 10 kts on Tuesday, ahead of a cold
front approaching from the north.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...25




000
FXUS63 KILX 022013
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
313 PM CDT MON MAY 2 2016

.SHORT TERM...(Tonight)
ISSUED AT 313 PM CDT Mon May 2 2016

Main short-term forecast concern will be timing of potential
clearing tonight.  While the main surface boundary has dropped south
of the Ohio River, a trailing upper trough extending from Wisconsin
southwestward to Kansas has provided enough synoptic lift to produce
widespread overcast conditions today.  Visible satellite loops show
the low cloud cover pivoting southward on the back side of a subtle
upper wave currently over central Illinois.  As this feature tracks
further eastward, think clouds will gradually dissipate/clear the
Illinois River Valley this evening.  Due to trajectory of cloud
cover and relatively light flow, clouds will likely hold throughout
the entire night along/east of the I-57 corridor.  May see a few
isolated light showers this evening: however, most locations will
remain dry.  Overnight low temperatures will range from the lower
40s northwest of the Illinois River where clearing will occur
earliest...to around 50 degrees far southeast around Robinson and
Lawrenceville.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 313 PM CDT Mon May 2 2016

Cyclonic flow will continue over the area through Wed. A lull in the
pcpn chances will be seen Tuesday as CWA will be in between troughs
rotating through the area. However, will still keep a slight chance
of showers in the east and southeast Tuesday due to a 500mb trough
moving south through the area...just without any surface reflection.
A bigger and more dominate trough will drop into the area Tue night
through Wed. Pcpn will start in the north Tue evening and then move
south through the area the remainder of the night and then in the
east on Wed. Isolated thunder will also be possible given greater
lapse rates due to cold 500mb temps moving over the area in
association with the upper level low. The pcpn will move off to the
east Wed night, which will allow high pressure to build into the
region with dry weather and slowly warming temps for Thur through
Fri. This surface high pressure ridge will get flattened by the end
of the week as another frontal system drops into the area for the
weekend. With warm and moist air being advected into the area Friday
and Saturday, will be plenty of instability for thunderstorms along
and ahead of the front Sat night through Monday. The front does seem
to hang around the area through the weekend since there will be an
upper level low just east of the US and another one over the
southwest US.

Temps will remain below normal most of the week, but begin to warm
back up as the high pressure that builds in Thursday moves off to
the east, bringing back southerly winds. The warmer temps will
continue through the weekend and into the beginning of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1253 PM CDT Mon May 2 2016

MVFR ceilings prevail at the central Illinois terminals early this
afternoon. Latest water vapor imagery shows a weak short-wave
trough over west-central Illinois between KSTL and KUIN. As this
feature tracks eastward, the low cloud cover will tend to pivot
southward in its wake, resulting in rising ceilings and eventually
a clearing trend from west to east later this afternoon and
evening. HRRR forecast suggests ceilings improving to VFR at KPIA
as early as 20z...but holding off until 03-04z further southeast
at KCMI/KDEC. Think skies will clear along/west of I-55 during the
evening, then further east late tonight toward dawn Tuesday. After
that, forecast soundings indicate steep lapse rates developing on
Tuesday, which should lead to at least SCT diurnal clouds at
around 5000ft. Winds will be light through the entire
period...initially from the northeast this afternoon, shifting to
the northwest by Tuesday morning.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...Barnes
LONG TERM...Auten
AVIATION...Barnes




000
FXUS63 KLOT 021952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
252 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 18Z TAFS...

DRY AIR CONTINUES TO SLIDE SOUTH FROM SOUTHERN WISCONSIN INTO
NORTHERN IL AIRFIELDS...WITH MINIMAL CLOUD COVER AND VFR CONDS
EXPECTED TO PERSIST THROUGH THE NEXT 24 HOURS. WITH HIGH PRESSURE
CENTERED TO THE NORTH...WINDS HAVE REMAINED NORTHEASTERLY BETWEEN
030 TO 050 DEGREES AND SPEEDS OF 10 TO 12KT WITH OCCASIONAL GUSTS
TO 20KT. CLOSER TO SUNSET WINDS ARE EXPECTED TO FURTHER
DIMINISH...THEN BEGIN TO TURN NORTHERLY WITH SPEEDS AROUND 4-6KT
BY 3Z. WINDS WILL THEN BECOME VARIABLE TO NORTHWESTERLY OVERNIGHT
WITH NEAR CLOUDLESS SKIES. SHORTLY AFTER DAYBREAK TUE WINDS WILL
BECOME WESTERLY WITH INCREASING SPEEDS TO AROUND 12-15KT AND
OCCASIONAL GUSTS DEVELOPING BY MIDDAY TO 18KT. CLOUDS WILL BE
SLOWLY ON THE INCREASE BY LATE AFTERNOON INTO EARLY TUESDAY
EVENING.

BEACHLER

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

.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 021952
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
252 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
248 PM CDT

WEDNESDAY NIGHT THROUGH MONDAY...

NOAM WATER VAPOR IMAGERY SHOWS A PACIFIC JET COMING ONSHORE IN THE
WESTERN US BEING FORCED NORTHWARD INTO CANADA WITH AN UPPER LEVEL
HIGH HELPING TO CURVE THIS JET ANTI-CYCLONICALLY AROUND WESTERN
CANADA. THE LEADING EDGE OF THIS JET CONTINUES TO PUSH SOUTHWARD IN
THE CANADIAN PRAIRIES. BY TUESDAY NIGHT...NORTHERN ILLINOIS WILL BE
IN THE LEFT EXIT REGION OF THIS JET AS 500 MB HEIGHTS FALL
IMPRESSIVELY DURING CYCLOGENESIS. THE SURFACE LOW WILL PULL A COLD
FRONT ACROSS THE REGION TUESDAY NIGHT AND SPREAD RAIN SHOWERS ACROSS
THE CWA. GIVEN THE RAPID UPPER LEVEL HEIGHT FALLS...THERE IS A SMALL
CHANCE FOR THUNDERSTORMS TO OCCUR ALONG THE LINE OF SHOWERS.

HEIGHT FALLS TO NEAR 540 DAM ARE PROJECTED WITH THIS FEATURE...AND
H85 TEMPS WILL DROP INTO THE NEGATIVE SINGLE DIGITS. COLD AIR OF
THIS NATURE FALLS INTO THE 10TH PERCENTILE OF ILX/DVN SOUNDINGS
FOR THE FIRST WEEK OF MAY. GIVEN THESE ANOMALIES...DAYTIME
TEMPERATURES WILL NOT RISE MUCH ON WEDNESDAY WITH SOME LOCATIONS
ONLY HITTING THE UPPER 40S. WITH THE STEEP LAPSE RATES ACROSS THE
AREA AND THE CENTER OF THE 500 MB LOW PASSING OVER LAKE
MICHIGAN...EXPECT WEAK CONVECTIVE SHOWERS AND POSSIBLY SOME
GRAUPEL DURING THE AFTERNOON. AN ADDITIONAL SHOCK WILL COME WITH
THE NEAR FREEZING CONDITIONS FOR WEDNESDAY NIGHT. SKIES MAY CLEAR
OUT SOME...BUT SURFACE TO H85 RH REMAINS ABOVE 80 PERCENT NEAR THE
LAKE. LUCKILY THE WINDS WILL ALSO REMAIN ABOVE 5-10KT THANKS TO A
LINGERING PRESSURE GRADIENT. IF EITHER OF THESE TWO INGREDIENTS GO
AWAY IN FUTURE FORECASTS...EXPECT TEMPS TO DROP 5 DEGREES COOLER.

THE REMAINDER OF THE EXTENDED FORECAST WILL FEATURE A PSEUDO OMEGA
BLOCK PATTERN ADVANCING AND SHRINKING ACROSS THE CENTER OF THE
CONUS. EXPECT A SHARP INCREASE IN TEMPERATURES FRIDAY AND SATURDAY
AS WARM ADVECTION FROM THE WEST-SOUTHWEST WILL BE ONGOING. A COLD
FRONT LOOKS TO DROP THROUGH THE GREAT LAKES SATURDAY NIGHT AND
BECOME STATIONARY. THIS WILL DROP TEMPS ACROSS THE AREA AGAIN WHILE
KEEPING A PERSISTENT CHANCE FOR THUNDERSTORMS IN THE DAYS 6-7
FORECAST.

MM

&&

.AVIATION...
FOR THE 18Z TAFS...

DRY AIR CONTINUES TO SLIDE SOUTH FROM SOUTHERN WISCONSIN INTO
NORTHERN IL AIRFIELDS...WITH MINIMAL CLOUD COVER AND VFR CONDS
EXPECTED TO PERSIST THROUGH THE NEXT 24 HOURS. WITH HIGH PRESSURE
CENTERED TO THE NORTH...WINDS HAVE REMAINED NORTHEASTERLY BETWEEN
030 TO 050 DEGREES AND SPEEDS OF 10 TO 12KT WITH OCCASIONAL GUSTS
TO 20KT. CLOSER TO SUNSET WINDS ARE EXPECTED TO FURTHER
DIMINISH...THEN BEGIN TO TURN NORTHERLY WITH SPEEDS AROUND 4-6KT
BY 3Z. WINDS WILL THEN BECOME VARIABLE TO NORTHWESTERLY OVERNIGHT
WITH NEAR CLOUDLESS SKIES. SHORTLY AFTER DAYBREAK TUE WINDS WILL
BECOME WESTERLY WITH INCREASING SPEEDS TO AROUND 12-15KT AND
OCCASIONAL GUSTS DEVELOPING BY MIDDAY TO 18KT. CLOUDS WILL BE
SLOWLY ON THE INCREASE BY LATE AFTERNOON INTO EARLY TUESDAY
EVENING.

BEACHLER

&&

.MARINE...
248 PM CDT

WEAK UPPER LEVEL FLOW OVER THE NEXT 24 HOURS WILL KEEP CALM
CONDITIONS PRESENT OVER LAKE MICHIGAN. LITTLE DIFFERENCE IN LAKE
TO LAND TEMPERATURES WILL ASSIST IN STABILITY OVER THE LAKE AS
WELL. ON TUESDAY...SOUTHERLY WINDS WILL INCREASE AHEAD OF A COLD
FRONT BEFORE SHARPLY SHIFTING NORTHERLY BEHIND THE FRONT TUESDAY
NIGHT. COLD AIR ADVECTION AND A PRESSURE GRADIENT BEHIND THE FRONT
WILL ALLOW GUSTS IN THE UPPER 20S INTO WEDNESDAY. FOLLOWING THAT
FRONTAL FEATURE...A STABLE HIGH PRESSURE REGIME IS EXPECTED INTO
THE WEEKEND.

MM

&&

.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 021915
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
215 PM CDT MON MAY 2 2016

.SHORT TERM...
215 PM CDT

THROUGH TUESDAY...

DRY AIR CONTINUES TO SLIDE SOUTH/SOUTHWEST ACROSS NORTHERN IL...AS
DEW POINTS HAVE FALLEN INTO THE MID/UPR 30S ACROSS FAR NORTHCENTRAL
IL. FURTHER SOUTH DEW POINTS ARE GENERALLY AROUND 40 THE LOWER 40S.
CLOUDS HAVE REMAINED MINIMAL ACROSS MUCH OF THE AREA...WITH SOME
DIURNAL CUMULUS WEST OF THE CHICAGO METRO AREA. JUST BEYOND PEAK
HEATING OF THE AFTERNOON THE DIURNAL CUMULUS SHOULD BEGIN TO
DISSIPATE...WITH THE NORTHEAST WINDS DIMINISHING TO AROUND 5 TO 10
MPH. HIGH PRESSURE CENTERED TO THE NORTH OF THE AREA WILL KEEP WINDS
LIGHT AND VARIABLE OVERNIGHT...WHICH COULD ALLOW TEMPERATURES TO
STEADILY RADIATE INTO THE LOWER 40S. HOWEVER AREAS THAT HAVE HAD DEW
POINTS THIS AFTERNOON FALL INTO THE MIDDLE 30S...TEMPS TONIGHT COULD
DIP INTO THE UPPER 30S BETWEEN ROCKFORD AND WAUKEGAN DOWN TO DEKALB.
HAVE INCLUDED PATCHY FROST WORDING OVERNIGHT.

TUESDAY... BROAD SFC RIDGING WILL CONSOLIDATE TO A RIDGE OVER THE
CENTRAL ROCKIES/PLAINS...WHICH WILL ALLOW A WEST/EAST GRADIENT TO
DEVELOP MIDDAY TUESDAY. WITH MINIMAL CLOUD COVER TO START THE DAY
TEMPS WILL QUICKLY WARM INTO THE 50S AND EVENTUALLY MIDDLE TO UPPER
60S BY EARLY AFTERNOON ACROSS NORTHERN IL. WEST WINDS WILL INCREASE
AS WELL...WITH THE FOCUS FOR LATE AFTERNOON/EVENING TURNING TOWARDS
A SHORTWAVE SLIDING EAST ACROSS LAKE SUPERIOR AND A TRAILING FRONTAL
BOUNDARY PROGGED TO DIVE SOUTH ACROSS THE WESTERN GREAT LAKES.
GUIDANCE HAS REMAINED RELATIVELY CONSISTENT WITH THE BEST CHANCE FOR
PRECIP ARRIVING AROUND THE EVENING HOURS FROM THE NORTH TUESDAY.

BEACHLER

&&

.LONG TERM...
356 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

UPPER PATTERN IS HIGHLY AMPLIFIED BY MID-WEEK...WITH DEEP TROUGHS
OVER BOTH COASTS AND AN UPPER RIDGE ACROSS THE CENTRAL CONUS. AS
THE RIDGE DRIFTS EASTWARD...RISING HEIGHTS/SUBSIDENCE RESULT IN
SURFACE HIGH PRESSURE BUILDING INTO THE REGION THURSDAY AND
BRINGING DRY AND WARMER WEATHER TO THE AREA FOR THE END OF THE
WEEK. THURSDAY WILL STILL BE A BIT ON THE COOL SIDE WITH TEMPS IN
THE UPPER 50S-LOW 60S IN THE VICINITY OF THE SURFACE RIDGE AND
WITH LIGHT NORTHERLY WINDS AND LAKE BREEZES. 70S RETURN FRIDAY AND
SATURDAY HOWEVER AS WINDS TURN SOUTHWEST AS AN AREA OF LOW
PRESSURE TRACKS NORTH OF LAKE SUPERIOR AND TRAILS A COLD FRONT
ACROSS THE UPPER MIDWEST. THIS FRONT WILL SAG ACROSS THE AREA LATE
SATURDAY...WITH AN ATTENDANT CHANCE OF THUNDERSTORMS...THEN BECOME
STATIONARY SOUTH OF THE CWA SUNDAY AS WEAK HIGH PRESSURE SPREADS
ACROSS THE NORTHERN LAKES. THIS WILL LIKELY SET UP A NORTH-SOUTH
GRADIENT OF TEMPS WITH 70S ACROSS CENTRAL IL/IN SUNDAY...AND
COOLER 50S-60S ACROSS FAR NORTHEAST IL NEAR LAKE MICHIGAN.
PRESENCE OF THE SURFACE FRONT AND ELEVATED BAROCLINIC ZONE TO ITS
NORTH WILL MAINTAIN THE POTENTIAL FOR SCATTERED SHOWERS AND
THUNDERSTORMS THROUGH SUNDAY.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

DRY AIR CONTINUES TO SLIDE SOUTH FROM SOUTHERN WISCONSIN INTO
NORTHERN IL AIRFIELDS...WITH MINIMAL CLOUD COVER AND VFR CONDS
EXPECTED TO PERSIST THROUGH THE NEXT 24 HOURS. WITH HIGH PRESSURE
CENTERED TO THE NORTH...WINDS HAVE REMAINED NORTHEASTERLY BETWEEN
030 TO 050 DEGREES AND SPEEDS OF 10 TO 12KT WITH OCCASIONAL GUSTS
TO 20KT. CLOSER TO SUNSET WINDS ARE EXPECTED TO FURTHER
DIMINISH...THEN BEGIN TO TURN NORTHERLY WITH SPEEDS AROUND 4-6KT
BY 3Z. WINDS WILL THEN BECOME VARIABLE TO NORTHWESTERLY OVERNIGHT
WITH NEAR CLOUDLESS SKIES. SHORTLY AFTER DAYBREAK TUE WINDS WILL
BECOME WESTERLY WITH INCREASING SPEEDS TO AROUND 12-15KT AND
OCCASIONAL GUSTS DEVELOPING BY MIDDAY TO 18KT. CLOUDS WILL BE
SLOWLY ON THE INCREASE BY LATE AFTERNOON INTO EARLY TUESDAY
EVENING.

BEACHLER

&&

.MARINE...
300 AM CDT

LOW PRESSURE IS DEPARTING THE REGION EARLY THIS MORNING WITH SOME
LINGERING 15 TO 20 KT WINDS STILL IN PLACE ACROSS SOUTHERN LAKE
MICHIGAN...BUT PROGGED TO CONTINUE TO DIMINISH THROUGH THE
MORNING. HIGH PRESSURE WILL BUILD ACROSS LAKE MICHIGAN THIS
EVENING AND TONIGHT...THEN SOUTHWESTERLY FLOW WILL DEVELOP ON
TUESDAY AS LOW PRESSURE MOVES ACROSS ONTARIO. THE LOW WILL MOVE
SOUTHEAST TO THE EASTERN GREAT LAKES REGION BY WEDNESDAY...BUT A
TRAILING COLD FRONT IS PROGGED TO MOVE SOUTH ACROSS LAKE MICHIGAN
TUESDAY NIGHT. NORTH WINDS GUSTING TO 30 KT ARE EXPECTED TO
DEVELOP BEHIND THE FRONT LATE TUESDAY NIGHT AND CONTINUE THROUGH
THE DAY WEDNESDAY. WINDS SHOULD BEGIN TO DIMINISH THURSDAY AS
ANOTHER RIDGE APPROACHES THE REGION.

BMD

&&

.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:
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000
FXUS63 KLOT 021759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1259 PM CDT MON MAY 2 2016

.UPDATE...1031 AM CDT

SHORTLY BEFORE SUNRISE SKIES BEGAN TO THIN ACROSS NORTHEAST
ILLINOIS AS DRIER AIR BEGAN TO DRIFT SOUTH FROM THE WEAK ANTI-
CYCLONIC FEATURE POSITIONED OVER CENTRAL WISCONSIN AND STRETCHES
WEST THROUGH THE ROCKIES. THIS RIDGE OF HIGH PRESSURE WILL LIKELY
MAINTAIN LESS CLOUD COVER ACROSS FAR NORTHERN IL...HOWEVER THE
FRONTAL BOUNDARY AND STRATUS LAYER WILL PERSIST ALONG AND SOUTH OF
I-80. TEMPERATURES AS A RESULT MAY WARM A DEGREE OR TWO WARMER
INTO THE MIDDLE TO PERHAPS UPPER 50S WHERE SKIES REMAIN SUNNY.
HOWEVER FOR AREAS ADJACENT TO LAKE MICHIGAN TEMPERATURES MAY
REMAIN IN THE UPPER 40S TO AROUND 50 AS WINDS WILL BE FROM A NORTH
TO AT TIMES NORTHEAST DIRECTION.

BEACHLER

&&

.SHORT TERM...
348 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

SOMEWHAT UNSETTLED WEATHER PATTERN WILL CONTINUE ACROSS THE AREA
THROUGH MID-WEEK...AS A LONG WAVE UPPER TROUGH EVOLVES ACROSS
EASTERN NORTH AMERICA. MOSTLY CLOUDY...COOL AND OCCASIONALLY
SHOWERY CONDITIONS WILL PLAGUE THE REGION TODAY AND AGAIN
WEDNESDAY... INTERRUPTED BRIEFLY TUESDAY AS WARMER WESTERLY FLOW
DEVELOPS IN ADVANCE OF STRONG DIGGING SHORT WAVE AND SURFACE COLD
FRONT RESPONSIBLE FOR CARVING OUT THE AFOREMENTIONED LARGE SCALE
EASTERN TROUGH.

IN THE NEAR TERM...MID-LEVEL WAVE AND ASSOCIATED SURFACE LOW
WHICH PROVIDED OUR RAINY WEEKEND WERE MOVING OFF TO THE EAST OF
THE AREA EARLY THIS MORNING...WITH ONLY A FEW SPRINKLES AND PATCHY
DRIZZLE LINGERING MAINLY ACROSS OUR NORTHWEST INDIANA COUNTIES AS
OF 3 AM. LOW LEVEL WINDS BACKING MORE NORTHERLY THIS MORNING WILL
BRING MODEST DRYING WHICH SHOULD SHUT OFF ANY LINGERING LIGHT
PRECIP...AND THIN OUT SOME OF THE EXTENSIVE CLOUD COVER ESPECIALLY
OVER FAR NORTHERN IL. SIGNIFICANT CLEARING IS NOT EXPECTED
HOWEVER...AS ANOTHER STRONG MID-LEVEL WAVE DROPPING SOUTHEAST INTO
THE DAKOTAS EARLY THIS MORNING APPROACHES THE AREA THIS AFTERNOON.
ASSOCIATED HEIGHT FALLS AND COOLING MID-LEVEL TEMPS SHOULD SUPPORT
STRATOCU DEVELOPMENT AND MAY SUPPORT A FEW SPRINKLES MAINLY
WEST/NORTHWEST OF THE CWA BY AFTERNOON. HIGH-RES GUIDANCE ALSO
CONTINUES TO DEPICT SOME LIGHT QPF ACROSS OUR FAR SOUTHEAST
COUNTIES WHERE LOW LEVEL MOISTURE WILL LINGER INTO TONIGHT IN THE
VICINITY OF WEAK SURFACE TROUGH LEFT BEHIND DEPARTING LOW
PRESSURE. NORTHEAST WINDS OFF OF THE LAKE COMBINED WITH
CONSIDERABLE CLOUD COVER AND RELATIVELY COOL TEMPS ALOFT WILL
LIMIT HIGH TEMPS TO THE 50S IN MOST AREAS TODAY...WITH UPPER 40S
LIKELY ALONG THE IMMEDIATE LAKE MICHIGAN SHORE. FAR NORTHWEST
COUNTIES MAY TAG 60 BRIEFLY WELL INLAND OF MAIN LAKE COOLING PUSH
AND WHERE SOME PEAKS OF SUN MAY BE POSSIBLE AT TIMES.

NORTHERN PLAINS SHORT WAVE PUSHES SOUTHEAST ACROSS THE AREA
OVERNIGHT AND THEN DRIFTS OFF TO OUR SOUTHEAST ON TUESDAY...WITH A
BRIEF PERIOD OF SUBSIDENCE AND A WEAK SURFACE HIGH PRESSURE RIDGE
OVER THE AREA DURING THE DAY. LOW LEVEL WINDS WILL BACK TO THE
WEST AS THIS RIDGE MOVES OFF TO THE SOUTHEAST IN THE
AFTERNOON...AND IN RESPONSE TO LOW PRESSURE DEVELOPING OVER THE
NORTHERN LAKES IN ASSOCIATION WITH ANOTHER DEEP UPPER LOW DIGGING
SOUTHEAST ACROSS THE REGION. THE GOOD NEWS IS THAT WE BRIEFLY WARM
UP TUESDAY AHEAD OF THIS NEXT SYSTEM... WITH HIGHS IN THE MID-
UPPER 60S EXPECTED. WEST WINDS AHEAD OF THE APPROACHING COLD FRONT
SHOULD LIMIT ANY LAKE COOLING PRIMARILY TO THE SOUTH SHORE OF THE
LAKE IN LAKE/PORTER COUNTIES. RAIN CHANCES RAMP UP QUICKLY AGAIN
TUESDAY EVENING AS THE STRONG MID-LEVEL WAVE AND SURFACE COLD
FRONT APPROACH. GIVEN CONSISTENT SIGNAL IN MODEL RUNS HAVE GONE
WITH LIKELY POPS TUESDAY NIGHT ESPECIALLY ACROSS THE EASTERN HALF
OR SO OF THE CWA...AND INCLUDED SLGT CHANCE MENTION OF THUNDER
GIVEN COOL TEMPS ALOFT WITHIN THE UPPER TROUGH. THE COLD FRONT
CLEARS THE AREA BY WEDNESDAY MORNING...THOUGH PRECIP WILL LIKELY
LINGER DURING THE DAY AS INSTABILITY SHOWERS DEVELOP BY AFTERNOON.
RENEWED PUSH OF COOLER AIR ON BLUSTERY NORTH WINDS WILL LIMIT
TEMPS ONCE AGAIN. HIGHS WEDNESDAY MAY NOT GET OUT OF THE 40S ALONG
THE INDIANA IMMEDIATE LAKE SHORE...THOUGH INLAND PARTS OF NORTHERN
IL MAY REACH 60. PRECIP THREAT DWINDLES WEDNESDAY NIGHT WITH
DIURNAL STABILIZATION. DECREASING WINDS AND CLEARING SKIES LOOK TO
PRODUCE A CHILLY NIGHT FOR EARLY MAY...WITH LOWS DIPPING INTO THE
UPPER 30S IN SOME SPOTS.

RATZER

&&

.LONG TERM...
356 AM CDT

THURSDAY THROUGH SUNDAY...

UPPER PATTERN IS HIGHLY AMPLIFIED BY MID-WEEK...WITH DEEP TROUGHS
OVER BOTH COASTS AND AN UPPER RIDGE ACROSS THE CENTRAL CONUS. AS
THE RIDGE DRIFTS EASTWARD...RISING HEIGHTS/SUBSIDENCE RESULT IN
SURFACE HIGH PRESSURE BUILDING INTO THE REGION THURSDAY AND
BRINGING DRY AND WARMER WEATHER TO THE AREA FOR THE END OF THE
WEEK. THURSDAY WILL STILL BE A BIT ON THE COOL SIDE WITH TEMPS IN
THE UPPER 50S-LOW 60S IN THE VICINITY OF THE SURFACE RIDGE AND
WITH LIGHT NORTHERLY WINDS AND LAKE BREEZES. 70S RETURN FRIDAY AND
SATURDAY HOWEVER AS WINDS TURN SOUTHWEST AS AN AREA OF LOW
PRESSURE TRACKS NORTH OF LAKE SUPERIOR AND TRAILS A COLD FRONT
ACROSS THE UPPER MIDWEST. THIS FRONT WILL SAG ACROSS THE AREA LATE
SATURDAY...WITH AN ATTENDANT CHANCE OF THUNDERSTORMS...THEN BECOME
STATIONARY SOUTH OF THE CWA SUNDAY AS WEAK HIGH PRESSURE SPREADS
ACROSS THE NORTHERN LAKES. THIS WILL LIKELY SET UP A NORTH-SOUTH
GRADIENT OF TEMPS WITH 70S ACROSS CENTRAL IL/IN SUNDAY...AND
COOLER 50S-60S ACROSS FAR NORTHEAST IL NEAR LAKE MICHIGAN.
PRESENCE OF THE SURFACE FRONT AND ELEVATED BAROCLINIC ZONE TO ITS
NORTH WILL MAINTAIN THE POTENTIAL FOR SCATTERED SHOWERS AND
THUNDERSTORMS THROUGH SUNDAY.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

DRY AIR CONTINUES TO SLIDE SOUTH FROM SOUTHERN WISCONSIN INTO
NORTHERN IL AIRFIELDS...WITH MINIMAL CLOUD COVER AND VFR CONDS
EXPECTED TO PERSIST THROUGH THE NEXT 24 HOURS. WITH HIGH PRESSURE
CENTERED TO THE NORTH...WINDS HAVE REMAINED NORTHEASTERLY BETWEEN
030 TO 050 DEGREES AND SPEEDS OF 10 TO 12KT WITH OCCASIONAL GUSTS
TO 20KT. CLOSER TO SUNSET WINDS ARE EXPECTED TO FURTHER
DIMINISH...THEN BEGIN TO TURN NORTHERLY WITH SPEEDS AROUND 4-6KT
BY 3Z. WINDS WILL THEN BECOME VARIABLE TO NORTHWESTERLY OVERNIGHT
WITH NEAR CLOUDLESS SKIES. SHORTLY AFTER DAYBREAK TUE WINDS WILL
BECOME WESTERLY WITH INCREASING SPEEDS TO AROUND 12-15KT AND
OCCASIONAL GUSTS DEVELOPING BY MIDDAY TO 18KT. CLOUDS WILL BE
SLOWLY ON THE INCREASE BY LATE AFTERNOON INTO EARLY TUESDAY
EVENING.

BEACHLER

&&

.MARINE...
300 AM CDT

LOW PRESSURE IS DEPARTING THE REGION EARLY THIS MORNING WITH SOME
LINGERING 15 TO 20 KT WINDS STILL IN PLACE ACROSS SOUTHERN LAKE
MICHIGAN...BUT PROGGED TO CONTINUE TO DIMINISH THROUGH THE
MORNING. HIGH PRESSURE WILL BUILD ACROSS LAKE MICHIGAN THIS
EVENING AND TONIGHT...THEN SOUTHWESTERLY FLOW WILL DEVELOP ON
TUESDAY AS LOW PRESSURE MOVES ACROSS ONTARIO. THE LOW WILL MOVE
SOUTHEAST TO THE EASTERN GREAT LAKES REGION BY WEDNESDAY...BUT A
TRAILING COLD FRONT IS PROGGED TO MOVE SOUTH ACROSS LAKE MICHIGAN
TUESDAY NIGHT. NORTH WINDS GUSTING TO 30 KT ARE EXPECTED TO
DEVELOP BEHIND THE FRONT LATE TUESDAY NIGHT AND CONTINUE THROUGH
THE DAY WEDNESDAY. WINDS SHOULD BEGIN TO DIMINISH THURSDAY AS
ANOTHER RIDGE APPROACHES THE REGION.

BMD

&&

.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 021759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1259 PM CDT MON MAY 2 2016

.UPDATE...1031 AM CDT

SHORTLY BEFORE SUNRISE SKIES BEGAN TO THIN ACROSS NORTHEAST
ILLINOIS AS DRIER AIR BEGAN TO DRIFT SOUTH FROM THE WEAK ANTI-
CYCLONIC FEATURE POSITIONED OVER CENTRAL WISCONSIN AND STRETCHES
WEST THROUGH THE ROCKIES. THIS RIDGE OF HIGH PRESSURE WILL LIKELY
MAINTAIN LESS CLOUD COVER ACROSS FAR NORTHERN IL...HOWEVER THE
FRONTAL BOUNDARY AND STRATUS LAYER WILL PERSIST ALONG AND SOUTH OF
I-80. TEMPERATURES AS A RESULT MAY WARM A DEGREE OR TWO WARMER
INTO THE MIDDLE TO PERHAPS UPPER 50S WHERE SKIES REMAIN SUNNY.
HOWEVER FOR AREAS ADJACENT TO LAKE MICHIGAN TEMPERATURES MAY
REMAIN IN THE UPPER 40S TO AROUND 50 AS WINDS WILL BE FROM A NORTH
TO AT TIMES NORTHEAST DIRECTION.

BEACHLER

&&

.SHORT TERM...
348 AM CDT

TODAY THROUGH WEDNESDAY NIGHT...

SOMEWHAT UNSETTLED WEATHER PATTERN WILL CONTINUE ACROSS THE AREA
THROUGH MID-WEEK...AS A LONG WAVE UPPER TROUGH EVOLVES ACROSS
EASTERN NORTH AMERICA. MOSTLY CLOUDY...COOL AND OCCASIONALLY
SHOWERY CONDITIONS WILL PLAGUE THE REGION TODAY AND AGAIN
WEDNESDAY... INTERRUPTED BRIEFLY TUESDAY AS WARMER WESTERLY FLOW
DEVELOPS IN ADVANCE OF STRONG DIGGING SHORT WAVE AND SURFACE COLD
FRONT RESPONSIBLE FOR CARVING OUT THE AFOREMENTIONED LARGE SCALE
EASTERN TROUGH.

IN THE NEAR TERM...MID-LEVEL WAVE AND ASSOCIATED SURFACE LOW
WHICH PROVIDED OUR RAINY WEEKEND WERE MOVING OFF TO THE EAST OF
THE AREA EARLY THIS MORNING...WITH ONLY A FEW SPRINKLES AND PATCHY
DRIZZLE LINGERING MAINLY ACROSS OUR NORTHWEST INDIANA COUNTIES AS
OF 3 AM. LOW LEVEL WINDS BACKING MORE NORTHERLY THIS MORNING WILL
BRING MODEST DRYING WHICH SHOULD SHUT OFF ANY LINGERING LIGHT
PRECIP...AND THIN OUT SOME OF THE EXTENSIVE CLOUD COVER ESPECIALLY
OVER FAR NORTHERN IL. SIGNIFICANT CLEARING IS NOT EXPECTED
HOWEVER...AS ANOTHER STRONG MID-LEVEL WAVE DROPPING SOUTHEAST INTO
THE DAKOTAS EARLY THIS MORNING APPROACHES THE AREA THIS AFTERNOON.
ASSOCIATED HEIGHT FALLS AND COOLING MID-LEVEL TEMPS SHOULD SUPPORT
STRATOCU DEVELOPMENT AND MAY SUPPORT A FEW SPRINKLES MAINLY
WEST/NORTHWEST OF THE CWA BY AFTERNOON. HIGH-RES GUIDANCE ALSO
CONTINUES TO DEPICT SOME LIGHT QPF ACROSS OUR FAR SOUTHEAST
COUNTIES WHERE LOW LEVEL MOISTURE WILL LINGER INTO TONIGHT IN THE
VICINITY OF WEAK SURFACE TROUGH LEFT BEHIND DEPARTING LOW
PRESSURE. NORTHEAST WINDS OFF OF THE LAKE COMBINED WITH
CONSIDERABLE CLOUD COVER AND RELATIVELY COOL TEMPS ALOFT WILL
LIMIT HIGH TEMPS TO THE 50S IN MOST AREAS TODAY...WITH UPPER 40S
LIKELY ALONG THE IMMEDIATE LAKE MICHIGAN SHORE. FAR NORTHWEST
COUNTIES MAY TAG 60 BRIEFLY WELL INLAND OF MAIN LAKE COOLING PUSH
AND WHERE SOME PEAKS OF SUN MAY BE POSSIBLE AT TIMES.

NORTHERN PLAINS SHORT WAVE PUSHES SOUTHEAST ACROSS THE AREA
OVERNIGHT AND THEN DRIFTS OFF TO OUR SOUTHEAST ON TUESDAY...WITH A
BRIEF PERIOD OF SUBSIDENCE AND A WEAK SURFACE HIGH PRESSURE RIDGE
OVER THE AREA DURING THE DAY. LOW LEVEL WINDS WILL BACK TO THE
WEST AS THIS RIDGE MOVES OFF TO THE SOUTHEAST IN THE
AFTERNOON...AND IN RESPONSE TO LOW PRESSURE DEVELOPING OVER THE
NORTHERN LAKES IN ASSOCIATION WITH ANOTHER DEEP UPPER LOW DIGGING
SOUTHEAST ACROSS THE REGION. THE GOOD NEWS IS THAT WE BRIEFLY WARM
UP TUESDAY AHEAD OF THIS NEXT SYSTEM... WITH HIGHS IN THE MID-
UPPER 60S EXPECTED. WEST WINDS AHEAD OF THE APPROACHING COLD FRONT
SHOULD LIMIT ANY LAKE COOLING PRIMARILY TO THE SOUTH SHORE OF THE
LAKE IN LAKE/PORTER COUNTIES. RAIN CHANCES RAMP UP QUICKLY AGAIN
TUESDAY EVENING AS THE STRONG MID-LEVEL WAVE AND SURFACE COLD
FRONT APPROACH. GIVEN CONSISTENT SIGNAL IN MODEL RUNS HAVE GONE
WITH LIKELY POPS TUESDAY NIGHT ESPECIALLY ACROSS THE EASTERN HALF
OR SO OF THE CWA...AND INCLUDED SLGT CHANCE MENTION OF THUNDER
GIVEN COOL TEMPS ALOFT WITHIN THE UPPER TROUGH. THE COLD FRONT
CLEARS THE AREA BY WEDNESDAY MORNING...THOUGH PRECIP WILL LIKELY
LINGER DURING THE DAY AS INSTABILITY SHOWERS DEVELOP BY AFTERNOON.
RENEWED PUSH OF COOLER AIR ON BLUSTERY NORTH WINDS WILL LIMIT
TEMPS ONCE AGAIN. HIGHS WEDNESDAY MAY NOT GET OUT OF THE 40S ALONG
THE INDIANA IMMEDIATE LAKE SHORE...THOUGH INLAND PARTS OF NORTHERN
IL MAY REACH 60. PRECIP THREAT DWINDLES WEDNESDAY NIGHT WITH
DIURNAL STABILIZATION. DECREASING WINDS AND CLEARING SKIES LOOK TO
PRODUCE A CHILLY NIGHT FOR EARLY MAY...WITH LOWS DIPPING INTO THE
UPPER 30S IN SOME SPOTS.

RATZER

&&

.LONG TERM...
356 AM CDT

THURSDAY THROUGH SUNDAY...

UPPER PATTERN IS HIGHLY AMPLIFIED BY MID-WEEK...WITH DEEP TROUGHS
OVER BOTH COASTS AND AN UPPER RIDGE ACROSS THE CENTRAL CONUS. AS
THE RIDGE DRIFTS EASTWARD...RISING HEIGHTS/SUBSIDENCE RESULT IN
SURFACE HIGH PRESSURE BUILDING INTO THE REGION THURSDAY AND
BRINGING DRY AND WARMER WEATHER TO THE AREA FOR THE END OF THE
WEEK. THURSDAY WILL STILL BE A BIT ON THE COOL SIDE WITH TEMPS IN
THE UPPER 50S-LOW 60S IN THE VICINITY OF THE SURFACE RIDGE AND
WITH LIGHT NORTHERLY WINDS AND LAKE BREEZES. 70S RETURN FRIDAY AND
SATURDAY HOWEVER AS WINDS TURN SOUTHWEST AS AN AREA OF LOW
PRESSURE TRACKS NORTH OF LAKE SUPERIOR AND TRAILS A COLD FRONT
ACROSS THE UPPER MIDWEST. THIS FRONT WILL SAG ACROSS THE AREA LATE
SATURDAY...WITH AN ATTENDANT CHANCE OF THUNDERSTORMS...THEN BECOME
STATIONARY SOUTH OF THE CWA SUNDAY AS WEAK HIGH PRESSURE SPREADS
ACROSS THE NORTHERN LAKES. THIS WILL LIKELY SET UP A NORTH-SOUTH
GRADIENT OF TEMPS WITH 70S ACROSS CENTRAL IL/IN SUNDAY...AND
COOLER 50S-60S ACROSS FAR NORTHEAST IL NEAR LAKE MICHIGAN.
PRESENCE OF THE SURFACE FRONT AND ELEVATED BAROCLINIC ZONE TO ITS
NORTH WILL MAINTAIN THE POTENTIAL FOR SCATTERED SHOWERS AND
THUNDERSTORMS THROUGH SUNDAY.

RATZER

&&

.AVIATION...
FOR THE 18Z TAFS...

DRY AIR CONTINUES TO SLIDE SOUTH FROM SOUTHERN WISCONSIN INTO
NORTHERN IL AIRFIELDS...WITH MINIMAL CLOUD COVER AND VFR CONDS
EXPECTED TO PERSIST THROUGH THE NEXT 24 HOURS. WITH HIGH PRESSURE
CENTERED TO THE NORTH...WINDS HAVE REMAINED NORTHEASTERLY BETWEEN
030 TO 050 DEGREES AND SPEEDS OF 10 TO 12KT WITH OCCASIONAL GUSTS
TO 20KT. CLOSER TO SUNSET WINDS ARE EXPECTED TO FURTHER
DIMINISH...THEN BEGIN TO TURN NORTHERLY WITH SPEEDS AROUND 4-6KT
BY 3Z. WINDS WILL THEN BECOME VARIABLE TO NORTHWESTERLY OVERNIGHT
WITH NEAR CLOUDLESS SKIES. SHORTLY AFTER DAYBREAK TUE WINDS WILL
BECOME WESTERLY WITH INCREASING SPEEDS TO AROUND 12-15KT AND
OCCASIONAL GUSTS DEVELOPING BY MIDDAY TO 18KT. CLOUDS WILL BE
SLOWLY ON THE INCREASE BY LATE AFTERNOON INTO EARLY TUESDAY
EVENING.

BEACHLER

&&

.MARINE...
300 AM CDT

LOW PRESSURE IS DEPARTING THE REGION EARLY THIS MORNING WITH SOME
LINGERING 15 TO 20 KT WINDS STILL IN PLACE ACROSS SOUTHERN LAKE
MICHIGAN...BUT PROGGED TO CONTINUE TO DIMINISH THROUGH THE
MORNING. HIGH PRESSURE WILL BUILD ACROSS LAKE MICHIGAN THIS
EVENING AND TONIGHT...THEN SOUTHWESTERLY FLOW WILL DEVELOP ON
TUESDAY AS LOW PRESSURE MOVES ACROSS ONTARIO. THE LOW WILL MOVE
SOUTHEAST TO THE EASTERN GREAT LAKES REGION BY WEDNESDAY...BUT A
TRAILING COLD FRONT IS PROGGED TO MOVE SOUTH ACROSS LAKE MICHIGAN
TUESDAY NIGHT. NORTH WINDS GUSTING TO 30 KT ARE EXPECTED TO
DEVELOP BEHIND THE FRONT LATE TUESDAY NIGHT AND CONTINUE THROUGH
THE DAY WEDNESDAY. WINDS SHOULD BEGIN TO DIMINISH THURSDAY AS
ANOTHER RIDGE APPROACHES THE REGION.

BMD

&&

.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 021753
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1253 PM CDT MON MAY 2 2016

.UPDATE...
Issued at 1020 AM CDT Mon May 2 2016

Another mostly cloudy and cool day is unfolding across central
Illinois, thanks to a slow-moving upper trough extending from
Wisconsin southwestward to Kansas. Weak synoptic lift ahead of
this feature will be enough to trigger isolated showers today.
With cool surface temps and corresponding instability parameters
remaining quite weak, do not think thunder will develop. Latest
visible satellite imagery generally shows overcast conditions:
however, some partial clearing is trying to work into the far
northern KILX CWA from the northeast. Think any clear spots that
develop will fill back in due to adequately steep lapse rates in
the vicinity of the approaching upper trough axis. As a result,
will maintain the mostly cloudy forecast across the board. Thanks
to the clouds and a continued northeasterly flow, high
temperatures this afternoon will remain below normal for this time
of year, mainly in the middle to upper 50s.

&&

.SHORT TERM...(Today)
ISSUED AT 322 AM CDT Mon May 2 2016

While cooler/drier post-frontal air has overspread all of central &
southeast Illinois since yesterday, the threat for a few showers
will persist today. Forecast area remains on the southern side of a
sheared upper-level trof that extends from eastern Canada into the
southwestern United States. Another disturbance within this mean
flow, currently over the central Plains, will track across the area
today. Radar returns associated with this disturbance are already
tracking across Missouri and approaching Illinois. This feature will
have limited moisture to work on today as it moves through, and
limited diurnal instability is expected to develop. With this
thinking in mind, only Slight Chance PoPs and low QPF are warranted
with the passage of this disturbance. Otherwise, abundant cloud
cover and cool northerly low-level flow support cooler than normal
highs today, with most locations topping out in the 50s.

.LONG TERM...(Tonight through Sunday)
ISSUED AT 322 AM CDT Mon May 2 2016

Little change indicated from previous model runs in terms of the
upper air pattern this week, with significant ridging along the
Rockies and a cold core low dropping southward through the Great
Lakes by Wednesday night. The ridge will get squeezed and shift
eastward with time, as a second upper low comes onshore of
California. A slow breakdown of the ridge will take place this
weekend as a more significant trough drops southeast through central
Canada. Although temperatures will be relatively cool for the middle
of the week, a significant warming trend will take place beginning
Friday as the thermal axis approaches from the west.

The presence of the current elongated trough from the Great Lakes to
the central Plains will continue a threat of a few showers on
Tuesday, mainly over the southeast parts of the CWA. Better chances
of scattered showers are expected Wednesday as the upper low moves
in from the north. Have increased the PoP`s late Tuesday night and
Wednesday with the main frontal boundary, with chance PoP`s as far
south as I-70 by late Tuesday night. While showers will taper for
awhile Wednesday morning as the front exits, scattered showers are
again expected in the afternoon across mainly eastern Illinois, as
the upper low arrives. Coldest air aloft will be centered over
Indiana in the afternoon, and have maintained a mention of isolated
thunder over eastern Illinois due to the steep lapse rates expected.

Late in the period, the extended models start to show some
disagreement. While the upper features are similar, with an upper
low over Colorado or eastern Utah and shortwaves rotating through
the Great Lakes, the ECMWF is further south with a surface warm
front connecting the two. This would result in scattered showers
into central Illinois Saturday night, whereas the GFS does not bring
the boundary into the area until late Sunday afternoon. For now have
mentioned only slight chances of showers and thunderstorms until
this starts to clear up a bit.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1253 PM CDT Mon May 2 2016

MVFR ceilings prevail at the central Illinois terminals early this
afternoon. Latest water vapor imagery shows a weak short-wave
trough over west-central Illinois between KSTL and KUIN. As this
feature tracks eastward, the low cloud cover will tend to pivot
southward in its wake, resulting in rising ceilings and eventually
a clearing trend from west to east later this afternoon and
evening. HRRR forecast suggests ceilings improving to VFR at KPIA
as early as 20z...but holding off until 03-04z further southeast
at KCMI/KDEC. Think skies will clear along/west of I-55 during the
evening, then further east late tonight toward dawn Tuesday. After
that, forecast soundings indicate steep lapse rates developing on
Tuesday, which should lead to at least SCT diurnal clouds at
around 5000ft. Winds will be light through the entire
period...initially from the northeast this afternoon, shifting to
the northwest by Tuesday morning.

&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...Barnes
SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...Barnes




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