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000
FXUS63 KILX 301202
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
702 AM CDT Tue Sep 30 2014

.SHORT TERM...(Today)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Short-term forecast concerns include potential for dense fog across
the southern KILX CWA, as well as, approaching deck of low clouds
across the north.  Clear skies/light winds have once again led to
the development of fog early this morning, particularly from the Saint
Louis area eastward across southern Illinois.  HRRR shows fog
becoming dense across this area over the next few hours before
dissipating after 8am.  So far the fog has not become widespread or
dense, but based on forecast soundings and the HRRR, have included
patchy dense fog south of I-70.  Have also issued a Special Weather
Statement to highlight the low visbys.

07z/2am surface analysis shows cold front settling southward into
central Illinois, with a widespread area of low clouds noted to the
north of the boundary across the Great Lakes into north-central
Illinois.  Latest IR satellite imagery shows leading edge of clouds
along the I-74 corridor.  Main questions today will be how far south
these clouds will push and whether or not they will clear out this
afternoon.  Satellite timing tools suggest the clouds will reach a
Rushville to Mattoon line by daybreak, but additional southward
progress appears unlikely as frontal boundary stalls.  Will
therefore go with a cloudy forecast across the northern two-thirds
of the CWA this morning, with mostly sunny skies across the far
south.  Despite continued northeasterly flow behind the front,
forecast soundings indicate a gradual dissipation of low-level
moisture as the day progresses.  Have gone with decreasing clouds
through the afternoon accordingly.  Due to the cloud cover and shift
in wind direction, temps will be quite a bit cooler today than in
recent days, with afternoon highs ranging from the upper 60s
along/north of I-74 to around 80 far south.

&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Winds will veer to the southeast on Wednesday in response to an
approaching upper wave and its associated cold front.  As a result,
temperatures will rise back into the upper 70s and lower 80s.  As a
deep upper trough slowly approaches from the west, surface low
pressure is expected to develop over the Southern Plains on
Wednesday then lift northward into the Great Lakes by Thursday
night.  Warm-advection showers/thunder will develop ahead of this
system Wednesday night: however, all model guidance keeps any precip
focused mainly across the western half of the CWA.  Given this
slowing trend, have removed PoPs for all locations along/east of a
Paris to Effingham line.  Further west, will go with likely PoPs
across the Illinois River Valley after midnight.  As surface low
deepens and tracks just west of the area on Thursday, strong S/SW
flow will provide one more very warm day with highs in the upper
70s/lower 80s.  Showers and thunderstorms will develop in advance of
a slowly approaching cold front, mainly focused across the west.
With strong upper dynamics in place and increasing amounts of
moisture flowing northward from the Gulf of Mexico, a few strong to
severe thunderstorms will be possible Thursday afternoon across
west-central Illinois.  Once low lifts into the Great Lakes, front
will get a solid push eastward by Thursday evening.  Will go with
categorical PoPs across the board as the boundary interacts with a
moist and moderately unstable environment.

Cold front will push into Indiana by early Friday morning, with
perhaps a few lingering showers across the Wabash River Valley.
Main weather story late in the week will be the sharply cooler
conditions.  850mb temps are progged to drop into the 0 to -2C range
by Saturday morning, supporting daytime highs only in the lower
to middle 60s and overnight lows in the lower 40s this weekend.
Airmass will slowly moderate by early next week, with temperatures
climbing back to around 70 by Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 700 AM CDT TUE SEP 30 2014

The cold front has pushed south of all TAF sites, with northeast
winds around 10-14kt in its wake. A short period of LIFR
fog and ceilings have developed along the leading edge of the
clouds at SPI and DEC with 200FT ceilings and 1/2sm FG. Behind the
front, IFR conditions with ceilings of 400-800 ft and p6sm vis have
developed within 2 hours of FROPA.

Based on the latest observation trends, ceilings should improve
to the MVFR by late morning. The main concern is how soon the
clouds will erode to VFR, with all the low level moisture trapped
under a developing subsidence inversion. Latest guidance off the
NAM-WRF and HRRR continues to suggest we will see some breaks
develop by late morning or early afternoon. Will continue with
the previous trends in the TAFs in scattering out the lower cigs
by afternoon with some broken VFR cigs into the late afternoon
hours. Southern TAFS of DEC and SPI should see VFR the soonest,
and possibly as early as 11 am or Noon.

The gusty northeast winds immediately behind the front will
settle out in the 8 to 14 kt range for much of the day. Mixing
heights will be limited by the low ceiling heights, so gusts
should not get to 20kt at any point.

&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Shimon







000
FXUS63 KILX 301202
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
702 AM CDT Tue Sep 30 2014

.SHORT TERM...(Today)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Short-term forecast concerns include potential for dense fog across
the southern KILX CWA, as well as, approaching deck of low clouds
across the north.  Clear skies/light winds have once again led to
the development of fog early this morning, particularly from the Saint
Louis area eastward across southern Illinois.  HRRR shows fog
becoming dense across this area over the next few hours before
dissipating after 8am.  So far the fog has not become widespread or
dense, but based on forecast soundings and the HRRR, have included
patchy dense fog south of I-70.  Have also issued a Special Weather
Statement to highlight the low visbys.

07z/2am surface analysis shows cold front settling southward into
central Illinois, with a widespread area of low clouds noted to the
north of the boundary across the Great Lakes into north-central
Illinois.  Latest IR satellite imagery shows leading edge of clouds
along the I-74 corridor.  Main questions today will be how far south
these clouds will push and whether or not they will clear out this
afternoon.  Satellite timing tools suggest the clouds will reach a
Rushville to Mattoon line by daybreak, but additional southward
progress appears unlikely as frontal boundary stalls.  Will
therefore go with a cloudy forecast across the northern two-thirds
of the CWA this morning, with mostly sunny skies across the far
south.  Despite continued northeasterly flow behind the front,
forecast soundings indicate a gradual dissipation of low-level
moisture as the day progresses.  Have gone with decreasing clouds
through the afternoon accordingly.  Due to the cloud cover and shift
in wind direction, temps will be quite a bit cooler today than in
recent days, with afternoon highs ranging from the upper 60s
along/north of I-74 to around 80 far south.

&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Winds will veer to the southeast on Wednesday in response to an
approaching upper wave and its associated cold front.  As a result,
temperatures will rise back into the upper 70s and lower 80s.  As a
deep upper trough slowly approaches from the west, surface low
pressure is expected to develop over the Southern Plains on
Wednesday then lift northward into the Great Lakes by Thursday
night.  Warm-advection showers/thunder will develop ahead of this
system Wednesday night: however, all model guidance keeps any precip
focused mainly across the western half of the CWA.  Given this
slowing trend, have removed PoPs for all locations along/east of a
Paris to Effingham line.  Further west, will go with likely PoPs
across the Illinois River Valley after midnight.  As surface low
deepens and tracks just west of the area on Thursday, strong S/SW
flow will provide one more very warm day with highs in the upper
70s/lower 80s.  Showers and thunderstorms will develop in advance of
a slowly approaching cold front, mainly focused across the west.
With strong upper dynamics in place and increasing amounts of
moisture flowing northward from the Gulf of Mexico, a few strong to
severe thunderstorms will be possible Thursday afternoon across
west-central Illinois.  Once low lifts into the Great Lakes, front
will get a solid push eastward by Thursday evening.  Will go with
categorical PoPs across the board as the boundary interacts with a
moist and moderately unstable environment.

Cold front will push into Indiana by early Friday morning, with
perhaps a few lingering showers across the Wabash River Valley.
Main weather story late in the week will be the sharply cooler
conditions.  850mb temps are progged to drop into the 0 to -2C range
by Saturday morning, supporting daytime highs only in the lower
to middle 60s and overnight lows in the lower 40s this weekend.
Airmass will slowly moderate by early next week, with temperatures
climbing back to around 70 by Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 700 AM CDT TUE SEP 30 2014

The cold front has pushed south of all TAF sites, with northeast
winds around 10-14kt in its wake. A short period of LIFR
fog and ceilings have developed along the leading edge of the
clouds at SPI and DEC with 200FT ceilings and 1/2sm FG. Behind the
front, IFR conditions with ceilings of 400-800 ft and p6sm vis have
developed within 2 hours of FROPA.

Based on the latest observation trends, ceilings should improve
to the MVFR by late morning. The main concern is how soon the
clouds will erode to VFR, with all the low level moisture trapped
under a developing subsidence inversion. Latest guidance off the
NAM-WRF and HRRR continues to suggest we will see some breaks
develop by late morning or early afternoon. Will continue with
the previous trends in the TAFs in scattering out the lower cigs
by afternoon with some broken VFR cigs into the late afternoon
hours. Southern TAFS of DEC and SPI should see VFR the soonest,
and possibly as early as 11 am or Noon.

The gusty northeast winds immediately behind the front will
settle out in the 8 to 14 kt range for much of the day. Mixing
heights will be limited by the low ceiling heights, so gusts
should not get to 20kt at any point.

&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Shimon







000
FXUS63 KILX 301202
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
702 AM CDT Tue Sep 30 2014

.SHORT TERM...(Today)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Short-term forecast concerns include potential for dense fog across
the southern KILX CWA, as well as, approaching deck of low clouds
across the north.  Clear skies/light winds have once again led to
the development of fog early this morning, particularly from the Saint
Louis area eastward across southern Illinois.  HRRR shows fog
becoming dense across this area over the next few hours before
dissipating after 8am.  So far the fog has not become widespread or
dense, but based on forecast soundings and the HRRR, have included
patchy dense fog south of I-70.  Have also issued a Special Weather
Statement to highlight the low visbys.

07z/2am surface analysis shows cold front settling southward into
central Illinois, with a widespread area of low clouds noted to the
north of the boundary across the Great Lakes into north-central
Illinois.  Latest IR satellite imagery shows leading edge of clouds
along the I-74 corridor.  Main questions today will be how far south
these clouds will push and whether or not they will clear out this
afternoon.  Satellite timing tools suggest the clouds will reach a
Rushville to Mattoon line by daybreak, but additional southward
progress appears unlikely as frontal boundary stalls.  Will
therefore go with a cloudy forecast across the northern two-thirds
of the CWA this morning, with mostly sunny skies across the far
south.  Despite continued northeasterly flow behind the front,
forecast soundings indicate a gradual dissipation of low-level
moisture as the day progresses.  Have gone with decreasing clouds
through the afternoon accordingly.  Due to the cloud cover and shift
in wind direction, temps will be quite a bit cooler today than in
recent days, with afternoon highs ranging from the upper 60s
along/north of I-74 to around 80 far south.

&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Winds will veer to the southeast on Wednesday in response to an
approaching upper wave and its associated cold front.  As a result,
temperatures will rise back into the upper 70s and lower 80s.  As a
deep upper trough slowly approaches from the west, surface low
pressure is expected to develop over the Southern Plains on
Wednesday then lift northward into the Great Lakes by Thursday
night.  Warm-advection showers/thunder will develop ahead of this
system Wednesday night: however, all model guidance keeps any precip
focused mainly across the western half of the CWA.  Given this
slowing trend, have removed PoPs for all locations along/east of a
Paris to Effingham line.  Further west, will go with likely PoPs
across the Illinois River Valley after midnight.  As surface low
deepens and tracks just west of the area on Thursday, strong S/SW
flow will provide one more very warm day with highs in the upper
70s/lower 80s.  Showers and thunderstorms will develop in advance of
a slowly approaching cold front, mainly focused across the west.
With strong upper dynamics in place and increasing amounts of
moisture flowing northward from the Gulf of Mexico, a few strong to
severe thunderstorms will be possible Thursday afternoon across
west-central Illinois.  Once low lifts into the Great Lakes, front
will get a solid push eastward by Thursday evening.  Will go with
categorical PoPs across the board as the boundary interacts with a
moist and moderately unstable environment.

Cold front will push into Indiana by early Friday morning, with
perhaps a few lingering showers across the Wabash River Valley.
Main weather story late in the week will be the sharply cooler
conditions.  850mb temps are progged to drop into the 0 to -2C range
by Saturday morning, supporting daytime highs only in the lower
to middle 60s and overnight lows in the lower 40s this weekend.
Airmass will slowly moderate by early next week, with temperatures
climbing back to around 70 by Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 700 AM CDT TUE SEP 30 2014

The cold front has pushed south of all TAF sites, with northeast
winds around 10-14kt in its wake. A short period of LIFR
fog and ceilings have developed along the leading edge of the
clouds at SPI and DEC with 200FT ceilings and 1/2sm FG. Behind the
front, IFR conditions with ceilings of 400-800 ft and p6sm vis have
developed within 2 hours of FROPA.

Based on the latest observation trends, ceilings should improve
to the MVFR by late morning. The main concern is how soon the
clouds will erode to VFR, with all the low level moisture trapped
under a developing subsidence inversion. Latest guidance off the
NAM-WRF and HRRR continues to suggest we will see some breaks
develop by late morning or early afternoon. Will continue with
the previous trends in the TAFs in scattering out the lower cigs
by afternoon with some broken VFR cigs into the late afternoon
hours. Southern TAFS of DEC and SPI should see VFR the soonest,
and possibly as early as 11 am or Noon.

The gusty northeast winds immediately behind the front will
settle out in the 8 to 14 kt range for much of the day. Mixing
heights will be limited by the low ceiling heights, so gusts
should not get to 20kt at any point.

&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Shimon







000
FXUS63 KILX 301202
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
702 AM CDT Tue Sep 30 2014

.SHORT TERM...(Today)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Short-term forecast concerns include potential for dense fog across
the southern KILX CWA, as well as, approaching deck of low clouds
across the north.  Clear skies/light winds have once again led to
the development of fog early this morning, particularly from the Saint
Louis area eastward across southern Illinois.  HRRR shows fog
becoming dense across this area over the next few hours before
dissipating after 8am.  So far the fog has not become widespread or
dense, but based on forecast soundings and the HRRR, have included
patchy dense fog south of I-70.  Have also issued a Special Weather
Statement to highlight the low visbys.

07z/2am surface analysis shows cold front settling southward into
central Illinois, with a widespread area of low clouds noted to the
north of the boundary across the Great Lakes into north-central
Illinois.  Latest IR satellite imagery shows leading edge of clouds
along the I-74 corridor.  Main questions today will be how far south
these clouds will push and whether or not they will clear out this
afternoon.  Satellite timing tools suggest the clouds will reach a
Rushville to Mattoon line by daybreak, but additional southward
progress appears unlikely as frontal boundary stalls.  Will
therefore go with a cloudy forecast across the northern two-thirds
of the CWA this morning, with mostly sunny skies across the far
south.  Despite continued northeasterly flow behind the front,
forecast soundings indicate a gradual dissipation of low-level
moisture as the day progresses.  Have gone with decreasing clouds
through the afternoon accordingly.  Due to the cloud cover and shift
in wind direction, temps will be quite a bit cooler today than in
recent days, with afternoon highs ranging from the upper 60s
along/north of I-74 to around 80 far south.

&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Winds will veer to the southeast on Wednesday in response to an
approaching upper wave and its associated cold front.  As a result,
temperatures will rise back into the upper 70s and lower 80s.  As a
deep upper trough slowly approaches from the west, surface low
pressure is expected to develop over the Southern Plains on
Wednesday then lift northward into the Great Lakes by Thursday
night.  Warm-advection showers/thunder will develop ahead of this
system Wednesday night: however, all model guidance keeps any precip
focused mainly across the western half of the CWA.  Given this
slowing trend, have removed PoPs for all locations along/east of a
Paris to Effingham line.  Further west, will go with likely PoPs
across the Illinois River Valley after midnight.  As surface low
deepens and tracks just west of the area on Thursday, strong S/SW
flow will provide one more very warm day with highs in the upper
70s/lower 80s.  Showers and thunderstorms will develop in advance of
a slowly approaching cold front, mainly focused across the west.
With strong upper dynamics in place and increasing amounts of
moisture flowing northward from the Gulf of Mexico, a few strong to
severe thunderstorms will be possible Thursday afternoon across
west-central Illinois.  Once low lifts into the Great Lakes, front
will get a solid push eastward by Thursday evening.  Will go with
categorical PoPs across the board as the boundary interacts with a
moist and moderately unstable environment.

Cold front will push into Indiana by early Friday morning, with
perhaps a few lingering showers across the Wabash River Valley.
Main weather story late in the week will be the sharply cooler
conditions.  850mb temps are progged to drop into the 0 to -2C range
by Saturday morning, supporting daytime highs only in the lower
to middle 60s and overnight lows in the lower 40s this weekend.
Airmass will slowly moderate by early next week, with temperatures
climbing back to around 70 by Monday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 700 AM CDT TUE SEP 30 2014

The cold front has pushed south of all TAF sites, with northeast
winds around 10-14kt in its wake. A short period of LIFR
fog and ceilings have developed along the leading edge of the
clouds at SPI and DEC with 200FT ceilings and 1/2sm FG. Behind the
front, IFR conditions with ceilings of 400-800 ft and p6sm vis have
developed within 2 hours of FROPA.

Based on the latest observation trends, ceilings should improve
to the MVFR by late morning. The main concern is how soon the
clouds will erode to VFR, with all the low level moisture trapped
under a developing subsidence inversion. Latest guidance off the
NAM-WRF and HRRR continues to suggest we will see some breaks
develop by late morning or early afternoon. Will continue with
the previous trends in the TAFs in scattering out the lower cigs
by afternoon with some broken VFR cigs into the late afternoon
hours. Southern TAFS of DEC and SPI should see VFR the soonest,
and possibly as early as 11 am or Noon.

The gusty northeast winds immediately behind the front will
settle out in the 8 to 14 kt range for much of the day. Mixing
heights will be limited by the low ceiling heights, so gusts
should not get to 20kt at any point.

&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Shimon






  [top]

000
FXUS63 KLOT 301140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* PERIODIC IFR CIGS IN LAKE EFFECT CLOUD/DRIZZLE BAND FOR THE NEXT
  FEW HOURS.

* MVFR CIGS GRADUALLY LIFTING LATE MORNING INTO THE AFTERNOON BUT
  REMAINING MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF
  SCATTERING POSSIBLE THIS AFTERNOON.

* NNW-N WINDS WITH LAKE EFFECT BAND NEXT FEW HOURS BUT SHIFT TO
  NNE EXPECTED BY MID MORNING...GOING FURTHER NORTHEAST INTO THE
  AFTERNOON. SPEEDS AROUND 10 KT.

MDB

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

LARGE AREA OF 1000-1500 FT CIGS IS SPREAD ACROSS THE REGION THIS
MORNING. RADAR MOSAIC SHOWS A NARROW BAND OF LAKE EFFECT LIGHT
RAIN/DRIZZLE OFFSHORE OF KMKE SOUTHWARD TO ORD/MDW. THIS IS
PRODUCING IFR CIGS AND MVFR VSBY. WINDS ON THE WEST SIDE OF THIS
BAND HAVE TURNED NNW WITH NNE WINDS ON THE EAST SIDE OF THE BAND.
EXPECT THIS BAND TO SLOWLY PIVOT EASTWARD INTO MID MORNING BUT IN
THE MEANTIME ORD/MDW WILL LIKELY BE IN AND OUT OF IFR CIGS AND
MVFR VSBY IN DRIZZLE. ONCE THE BAND SHIFTS EAST OR EVEN DISSIPATES
WINDS SHOULD TURN NNE THEN FURTHER NORTHEAST INTO THE AFTERNOON.
SPEEDS LOOK TO REMAIN AROUND 10 KT.

ONCE THE IFR IMPROVES MVFR WILL PERSIST BUT SHOULD SEE SCATTERING
TOWARDS RFD/DPA THIS AFTERNOON WITH FLOW OFF THE LAKE LIKELY
KEEPING MVFR CIGS AT ORD/MDW/GYY THROUGH THE DAY...THOUGH
SCATTERING IS POSSIBLE. LOW LEVEL WINDS WILL TURN SOUTHEASTERLY
THIS EVENING WHICH WILL PUSH THE LOW LEVEL MOISTURE AND ASSOCIATED
CLOUD COVER TO THE NORTHWEST. THERE MAY BE SOME EXPANSION OF
COVERAGE AS THIS OCCURS SO RFD/DPA MAY GET BACK INTO MVFR BUT WILL
KEEP COVERAGE SCATTERED FOR NOW. DO NOT HAVE A GREAT DEAL OF
CONFIDENCE IN TIMING OF CIG EVOLUTION TONIGHT AND MAY BE HOLDING
ONTO THEM TOO LONG. SKIES DO LOOK TO HAVE SCATTERED OR LESS
COVERAGE WEDNESDAY MORNING.

MDB


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

* HIGH CONFIDENCE IN AT LEAST PERIODIC IFR NEXT FEW HOURS. MEDIUM
  CONFIDENCE IN END TIME OF IFR.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE DAY WITH BASES RISING
  THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS THIS
  EVENING/TONIGHT...BUT LOW CONFIDENCE IN HOW LONG THEY MAY LAST.
  LOW CONFIDENCE IN POTENTIAL FOR A PERIOD OF SCATTERING THIS
  AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY NIGHT...INCREASING CHANCE FOR SHRA/TSRA. MVFR POSSIBLE.
SOUTHEAST WINDS.

THURSDAY...TSRA AND MVFR LIKELY. SOUTH WINDS.

FRIDAY...LOW CHANCE SHRA. MVFR POSSIBLE EARLY. GUSTY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...VFR. SLIGHT CHANCE SHRA. SOUTHWEST WINDS.

MONDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 301140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* PERIODIC IFR CIGS IN LAKE EFFECT CLOUD/DRIZZLE BAND FOR THE NEXT
  FEW HOURS.

* MVFR CIGS GRADUALLY LIFTING LATE MORNING INTO THE AFTERNOON BUT
  REMAINING MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF
  SCATTERING POSSIBLE THIS AFTERNOON.

* NNW-N WINDS WITH LAKE EFFECT BAND NEXT FEW HOURS BUT SHIFT TO
  NNE EXPECTED BY MID MORNING...GOING FURTHER NORTHEAST INTO THE
  AFTERNOON. SPEEDS AROUND 10 KT.

MDB

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

LARGE AREA OF 1000-1500 FT CIGS IS SPREAD ACROSS THE REGION THIS
MORNING. RADAR MOSAIC SHOWS A NARROW BAND OF LAKE EFFECT LIGHT
RAIN/DRIZZLE OFFSHORE OF KMKE SOUTHWARD TO ORD/MDW. THIS IS
PRODUCING IFR CIGS AND MVFR VSBY. WINDS ON THE WEST SIDE OF THIS
BAND HAVE TURNED NNW WITH NNE WINDS ON THE EAST SIDE OF THE BAND.
EXPECT THIS BAND TO SLOWLY PIVOT EASTWARD INTO MID MORNING BUT IN
THE MEANTIME ORD/MDW WILL LIKELY BE IN AND OUT OF IFR CIGS AND
MVFR VSBY IN DRIZZLE. ONCE THE BAND SHIFTS EAST OR EVEN DISSIPATES
WINDS SHOULD TURN NNE THEN FURTHER NORTHEAST INTO THE AFTERNOON.
SPEEDS LOOK TO REMAIN AROUND 10 KT.

ONCE THE IFR IMPROVES MVFR WILL PERSIST BUT SHOULD SEE SCATTERING
TOWARDS RFD/DPA THIS AFTERNOON WITH FLOW OFF THE LAKE LIKELY
KEEPING MVFR CIGS AT ORD/MDW/GYY THROUGH THE DAY...THOUGH
SCATTERING IS POSSIBLE. LOW LEVEL WINDS WILL TURN SOUTHEASTERLY
THIS EVENING WHICH WILL PUSH THE LOW LEVEL MOISTURE AND ASSOCIATED
CLOUD COVER TO THE NORTHWEST. THERE MAY BE SOME EXPANSION OF
COVERAGE AS THIS OCCURS SO RFD/DPA MAY GET BACK INTO MVFR BUT WILL
KEEP COVERAGE SCATTERED FOR NOW. DO NOT HAVE A GREAT DEAL OF
CONFIDENCE IN TIMING OF CIG EVOLUTION TONIGHT AND MAY BE HOLDING
ONTO THEM TOO LONG. SKIES DO LOOK TO HAVE SCATTERED OR LESS
COVERAGE WEDNESDAY MORNING.

MDB


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

* HIGH CONFIDENCE IN AT LEAST PERIODIC IFR NEXT FEW HOURS. MEDIUM
  CONFIDENCE IN END TIME OF IFR.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE DAY WITH BASES RISING
  THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS THIS
  EVENING/TONIGHT...BUT LOW CONFIDENCE IN HOW LONG THEY MAY LAST.
  LOW CONFIDENCE IN POTENTIAL FOR A PERIOD OF SCATTERING THIS
  AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY NIGHT...INCREASING CHANCE FOR SHRA/TSRA. MVFR POSSIBLE.
SOUTHEAST WINDS.

THURSDAY...TSRA AND MVFR LIKELY. SOUTH WINDS.

FRIDAY...LOW CHANCE SHRA. MVFR POSSIBLE EARLY. GUSTY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...VFR. SLIGHT CHANCE SHRA. SOUTHWEST WINDS.

MONDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 301140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* PERIODIC IFR CIGS IN LAKE EFFECT CLOUD/DRIZZLE BAND FOR THE NEXT
  FEW HOURS.

* MVFR CIGS GRADUALLY LIFTING LATE MORNING INTO THE AFTERNOON BUT
  REMAINING MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF
  SCATTERING POSSIBLE THIS AFTERNOON.

* NNW-N WINDS WITH LAKE EFFECT BAND NEXT FEW HOURS BUT SHIFT TO
  NNE EXPECTED BY MID MORNING...GOING FURTHER NORTHEAST INTO THE
  AFTERNOON. SPEEDS AROUND 10 KT.

MDB

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

LARGE AREA OF 1000-1500 FT CIGS IS SPREAD ACROSS THE REGION THIS
MORNING. RADAR MOSAIC SHOWS A NARROW BAND OF LAKE EFFECT LIGHT
RAIN/DRIZZLE OFFSHORE OF KMKE SOUTHWARD TO ORD/MDW. THIS IS
PRODUCING IFR CIGS AND MVFR VSBY. WINDS ON THE WEST SIDE OF THIS
BAND HAVE TURNED NNW WITH NNE WINDS ON THE EAST SIDE OF THE BAND.
EXPECT THIS BAND TO SLOWLY PIVOT EASTWARD INTO MID MORNING BUT IN
THE MEANTIME ORD/MDW WILL LIKELY BE IN AND OUT OF IFR CIGS AND
MVFR VSBY IN DRIZZLE. ONCE THE BAND SHIFTS EAST OR EVEN DISSIPATES
WINDS SHOULD TURN NNE THEN FURTHER NORTHEAST INTO THE AFTERNOON.
SPEEDS LOOK TO REMAIN AROUND 10 KT.

ONCE THE IFR IMPROVES MVFR WILL PERSIST BUT SHOULD SEE SCATTERING
TOWARDS RFD/DPA THIS AFTERNOON WITH FLOW OFF THE LAKE LIKELY
KEEPING MVFR CIGS AT ORD/MDW/GYY THROUGH THE DAY...THOUGH
SCATTERING IS POSSIBLE. LOW LEVEL WINDS WILL TURN SOUTHEASTERLY
THIS EVENING WHICH WILL PUSH THE LOW LEVEL MOISTURE AND ASSOCIATED
CLOUD COVER TO THE NORTHWEST. THERE MAY BE SOME EXPANSION OF
COVERAGE AS THIS OCCURS SO RFD/DPA MAY GET BACK INTO MVFR BUT WILL
KEEP COVERAGE SCATTERED FOR NOW. DO NOT HAVE A GREAT DEAL OF
CONFIDENCE IN TIMING OF CIG EVOLUTION TONIGHT AND MAY BE HOLDING
ONTO THEM TOO LONG. SKIES DO LOOK TO HAVE SCATTERED OR LESS
COVERAGE WEDNESDAY MORNING.

MDB


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

* HIGH CONFIDENCE IN AT LEAST PERIODIC IFR NEXT FEW HOURS. MEDIUM
  CONFIDENCE IN END TIME OF IFR.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE DAY WITH BASES RISING
  THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS THIS
  EVENING/TONIGHT...BUT LOW CONFIDENCE IN HOW LONG THEY MAY LAST.
  LOW CONFIDENCE IN POTENTIAL FOR A PERIOD OF SCATTERING THIS
  AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY NIGHT...INCREASING CHANCE FOR SHRA/TSRA. MVFR POSSIBLE.
SOUTHEAST WINDS.

THURSDAY...TSRA AND MVFR LIKELY. SOUTH WINDS.

FRIDAY...LOW CHANCE SHRA. MVFR POSSIBLE EARLY. GUSTY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...VFR. SLIGHT CHANCE SHRA. SOUTHWEST WINDS.

MONDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 301140
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
640 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* PERIODIC IFR CIGS IN LAKE EFFECT CLOUD/DRIZZLE BAND FOR THE NEXT
  FEW HOURS.

* MVFR CIGS GRADUALLY LIFTING LATE MORNING INTO THE AFTERNOON BUT
  REMAINING MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF
  SCATTERING POSSIBLE THIS AFTERNOON.

* NNW-N WINDS WITH LAKE EFFECT BAND NEXT FEW HOURS BUT SHIFT TO
  NNE EXPECTED BY MID MORNING...GOING FURTHER NORTHEAST INTO THE
  AFTERNOON. SPEEDS AROUND 10 KT.

MDB

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

LARGE AREA OF 1000-1500 FT CIGS IS SPREAD ACROSS THE REGION THIS
MORNING. RADAR MOSAIC SHOWS A NARROW BAND OF LAKE EFFECT LIGHT
RAIN/DRIZZLE OFFSHORE OF KMKE SOUTHWARD TO ORD/MDW. THIS IS
PRODUCING IFR CIGS AND MVFR VSBY. WINDS ON THE WEST SIDE OF THIS
BAND HAVE TURNED NNW WITH NNE WINDS ON THE EAST SIDE OF THE BAND.
EXPECT THIS BAND TO SLOWLY PIVOT EASTWARD INTO MID MORNING BUT IN
THE MEANTIME ORD/MDW WILL LIKELY BE IN AND OUT OF IFR CIGS AND
MVFR VSBY IN DRIZZLE. ONCE THE BAND SHIFTS EAST OR EVEN DISSIPATES
WINDS SHOULD TURN NNE THEN FURTHER NORTHEAST INTO THE AFTERNOON.
SPEEDS LOOK TO REMAIN AROUND 10 KT.

ONCE THE IFR IMPROVES MVFR WILL PERSIST BUT SHOULD SEE SCATTERING
TOWARDS RFD/DPA THIS AFTERNOON WITH FLOW OFF THE LAKE LIKELY
KEEPING MVFR CIGS AT ORD/MDW/GYY THROUGH THE DAY...THOUGH
SCATTERING IS POSSIBLE. LOW LEVEL WINDS WILL TURN SOUTHEASTERLY
THIS EVENING WHICH WILL PUSH THE LOW LEVEL MOISTURE AND ASSOCIATED
CLOUD COVER TO THE NORTHWEST. THERE MAY BE SOME EXPANSION OF
COVERAGE AS THIS OCCURS SO RFD/DPA MAY GET BACK INTO MVFR BUT WILL
KEEP COVERAGE SCATTERED FOR NOW. DO NOT HAVE A GREAT DEAL OF
CONFIDENCE IN TIMING OF CIG EVOLUTION TONIGHT AND MAY BE HOLDING
ONTO THEM TOO LONG. SKIES DO LOOK TO HAVE SCATTERED OR LESS
COVERAGE WEDNESDAY MORNING.

MDB


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

* HIGH CONFIDENCE IN AT LEAST PERIODIC IFR NEXT FEW HOURS. MEDIUM
  CONFIDENCE IN END TIME OF IFR.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE DAY WITH BASES RISING
  THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS THIS
  EVENING/TONIGHT...BUT LOW CONFIDENCE IN HOW LONG THEY MAY LAST.
  LOW CONFIDENCE IN POTENTIAL FOR A PERIOD OF SCATTERING THIS
  AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY NIGHT...INCREASING CHANCE FOR SHRA/TSRA. MVFR POSSIBLE.
SOUTHEAST WINDS.

THURSDAY...TSRA AND MVFR LIKELY. SOUTH WINDS.

FRIDAY...LOW CHANCE SHRA. MVFR POSSIBLE EARLY. GUSTY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...VFR. SLIGHT CHANCE SHRA. SOUTHWEST WINDS.

MONDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 300950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
450 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 10Z...

* IFR CIGS POSSIBLE THROUGH DAYBREAK DUE TO LAKE EFFECT
  PROCESSES...ESPECIALLY AT ORD. SOME -RA ALSO POSSIBLE.

* MVFR CIGS GRADUALLY LIFTING LATE MORNING INTO THE AFTERNOON BUT
  REMAINING MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF
  SCATTERING POSSIBLE THIS AFTERNOON.

* NORTH-NORTHEAST WINDS 10-15 KT EASE TO AROUND 10 KT FOR THE REST
  OF THE DAY THEN TURN NORTHEAST THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 10Z...

RADAR MOSAIC HAS STARTED TO SHOW SOME LAKE EFFECT SHOWERS
DEVELOPING OFF THE SE WI/FAR NE IL SHORELINE. KUGN HAS REPORTED
LIGHT RAIN AND A LOWERING TO IFR CIGS WITH KPWK ALSO LOWERING. A
LOOK AT WEB CAMS NEAR KUGN SEEMS TO INDICATE THAT THE RAIN DOES
NOT EXTEND TOO FAR INLAND. HAVE UPDATED ORD TAF TO INCLUDE A LOWER
MVFR CIG WITH TEMPO IFR CIGS AND LIGHT RAIN FOR THE NEXT FEW
HOURS. TRAJECTORIES SO FAR WOULD KEEP THE LOWER CIGS AND RAIN JUST
NORTH/WEST OF MDW BUT WILL NEED TO MONITOR CLOSELY. OTHERWISE
EXPECT STEADY TO SLOWLY LIFTING MVFR CIGS INTO MID MORNING AWAY
FROM THE LAKE BAND OF LOWER CLOUDS.

FROM 06Z...

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 10Z...

* LOW-MEDIUM CONFIDENCE IN SOME IFR CIGS OCCURRING THROUGH
  DAYBREAK IF NOT A BIT LONGER. LOW CONFIDENCE IN DURATION.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE DAY WITH BASES RISING
  THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS THIS
  EVENING/TONIGHT. LOW CONFIDENCE IN POTENTIAL FOR A PERIOD OF
  SCATTERING THIS AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 300950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
450 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 10Z...

* IFR CIGS POSSIBLE THROUGH DAYBREAK DUE TO LAKE EFFECT
  PROCESSES...ESPECIALLY AT ORD. SOME -RA ALSO POSSIBLE.

* MVFR CIGS GRADUALLY LIFTING LATE MORNING INTO THE AFTERNOON BUT
  REMAINING MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF
  SCATTERING POSSIBLE THIS AFTERNOON.

* NORTH-NORTHEAST WINDS 10-15 KT EASE TO AROUND 10 KT FOR THE REST
  OF THE DAY THEN TURN NORTHEAST THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 10Z...

RADAR MOSAIC HAS STARTED TO SHOW SOME LAKE EFFECT SHOWERS
DEVELOPING OFF THE SE WI/FAR NE IL SHORELINE. KUGN HAS REPORTED
LIGHT RAIN AND A LOWERING TO IFR CIGS WITH KPWK ALSO LOWERING. A
LOOK AT WEB CAMS NEAR KUGN SEEMS TO INDICATE THAT THE RAIN DOES
NOT EXTEND TOO FAR INLAND. HAVE UPDATED ORD TAF TO INCLUDE A LOWER
MVFR CIG WITH TEMPO IFR CIGS AND LIGHT RAIN FOR THE NEXT FEW
HOURS. TRAJECTORIES SO FAR WOULD KEEP THE LOWER CIGS AND RAIN JUST
NORTH/WEST OF MDW BUT WILL NEED TO MONITOR CLOSELY. OTHERWISE
EXPECT STEADY TO SLOWLY LIFTING MVFR CIGS INTO MID MORNING AWAY
FROM THE LAKE BAND OF LOWER CLOUDS.

FROM 06Z...

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

//ORD AND MDW CONFIDENCE...UPDATED 10Z...

* LOW-MEDIUM CONFIDENCE IN SOME IFR CIGS OCCURRING THROUGH
  DAYBREAK IF NOT A BIT LONGER. LOW CONFIDENCE IN DURATION.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE DAY WITH BASES RISING
  THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS THIS
  EVENING/TONIGHT. LOW CONFIDENCE IN POTENTIAL FOR A PERIOD OF
  SCATTERING THIS AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 300919
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
419 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR CIGS GRADUALLY LIFTING INTO THE AFTERNOON BUT REMAINING
  MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF SCATTERING
  POSSIBLE THIS AFTERNOON.

* NORTH-NORTHEAST WINDS 10-15 KT EASE TO AROUND 10 KT FOR THE REST
  OF THE DAY THEN TURN NORTHEAST THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 09Z...

CLOUD BASES HAVE BEEN VERY SLOWLY RISING AND IFR THREAT APPEARS TO
BE JUST ABUT OVER...THOUGH RFD COULD SEE A BRIEF REDUCTION IN THE
NEXT HOUR OR TWO. OTHERWISE THE SLOW UPWARD TREND SHOULD CONTINUE.
STILL UNCLEAR ON HOW MUCH SCATTERING WILL OCCUR THIS AFTERNOON BUT
RFD AND DPA STILL LOOK TO HAVE THE BEST CHANCE TO SCATTER OUT.
NORTH-NORTHEAST WINDS WILL GRADUALLY EASE THROUGH THE MORNING
BEFORE TURNING NORTHEAST THIS AFTERNOON.

FROM 06Z...

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN MVFR CIGS CONTINUING THROUGH THE DAY WITH
  BASES RISING THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS
  THIS EVENING/TONIGHT. LOW CONFIDENCE IN POTENTIAL FOR A PERIOD
  OF SCATTERING THIS AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 300919
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
419 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR CIGS GRADUALLY LIFTING INTO THE AFTERNOON BUT REMAINING
  MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF SCATTERING
  POSSIBLE THIS AFTERNOON.

* NORTH-NORTHEAST WINDS 10-15 KT EASE TO AROUND 10 KT FOR THE REST
  OF THE DAY THEN TURN NORTHEAST THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 09Z...

CLOUD BASES HAVE BEEN VERY SLOWLY RISING AND IFR THREAT APPEARS TO
BE JUST ABUT OVER...THOUGH RFD COULD SEE A BRIEF REDUCTION IN THE
NEXT HOUR OR TWO. OTHERWISE THE SLOW UPWARD TREND SHOULD CONTINUE.
STILL UNCLEAR ON HOW MUCH SCATTERING WILL OCCUR THIS AFTERNOON BUT
RFD AND DPA STILL LOOK TO HAVE THE BEST CHANCE TO SCATTER OUT.
NORTH-NORTHEAST WINDS WILL GRADUALLY EASE THROUGH THE MORNING
BEFORE TURNING NORTHEAST THIS AFTERNOON.

FROM 06Z...

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN MVFR CIGS CONTINUING THROUGH THE DAY WITH
  BASES RISING THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS
  THIS EVENING/TONIGHT. LOW CONFIDENCE IN POTENTIAL FOR A PERIOD
  OF SCATTERING THIS AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 300919
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
419 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR CIGS GRADUALLY LIFTING INTO THE AFTERNOON BUT REMAINING
  MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF SCATTERING
  POSSIBLE THIS AFTERNOON.

* NORTH-NORTHEAST WINDS 10-15 KT EASE TO AROUND 10 KT FOR THE REST
  OF THE DAY THEN TURN NORTHEAST THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 09Z...

CLOUD BASES HAVE BEEN VERY SLOWLY RISING AND IFR THREAT APPEARS TO
BE JUST ABUT OVER...THOUGH RFD COULD SEE A BRIEF REDUCTION IN THE
NEXT HOUR OR TWO. OTHERWISE THE SLOW UPWARD TREND SHOULD CONTINUE.
STILL UNCLEAR ON HOW MUCH SCATTERING WILL OCCUR THIS AFTERNOON BUT
RFD AND DPA STILL LOOK TO HAVE THE BEST CHANCE TO SCATTER OUT.
NORTH-NORTHEAST WINDS WILL GRADUALLY EASE THROUGH THE MORNING
BEFORE TURNING NORTHEAST THIS AFTERNOON.

FROM 06Z...

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN MVFR CIGS CONTINUING THROUGH THE DAY WITH
  BASES RISING THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS
  THIS EVENING/TONIGHT. LOW CONFIDENCE IN POTENTIAL FOR A PERIOD
  OF SCATTERING THIS AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 300919
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
419 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* MVFR CIGS GRADUALLY LIFTING INTO THE AFTERNOON BUT REMAINING
  MVFR...POSSIBLY THROUGH THE EVENING. PERIOD OF SCATTERING
  POSSIBLE THIS AFTERNOON.

* NORTH-NORTHEAST WINDS 10-15 KT EASE TO AROUND 10 KT FOR THE REST
  OF THE DAY THEN TURN NORTHEAST THIS AFTERNOON.

MDB

//DISCUSSION...UPDATED 09Z...

CLOUD BASES HAVE BEEN VERY SLOWLY RISING AND IFR THREAT APPEARS TO
BE JUST ABUT OVER...THOUGH RFD COULD SEE A BRIEF REDUCTION IN THE
NEXT HOUR OR TWO. OTHERWISE THE SLOW UPWARD TREND SHOULD CONTINUE.
STILL UNCLEAR ON HOW MUCH SCATTERING WILL OCCUR THIS AFTERNOON BUT
RFD AND DPA STILL LOOK TO HAVE THE BEST CHANCE TO SCATTER OUT.
NORTH-NORTHEAST WINDS WILL GRADUALLY EASE THROUGH THE MORNING
BEFORE TURNING NORTHEAST THIS AFTERNOON.

FROM 06Z...

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN MVFR CIGS CONTINUING THROUGH THE DAY WITH
  BASES RISING THROUGH AFTERNOON. MEDIUM CONFIDENCE IN MVFR CIGS
  THIS EVENING/TONIGHT. LOW CONFIDENCE IN POTENTIAL FOR A PERIOD
  OF SCATTERING THIS AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS. MEDIUM CONFIDENCE THAT SPEEDS
  WILL BE 10 KT OR LESS THIS AFTERNOON.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 300836
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 300836
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 AM CDT TUE SEP 30 2014

.DISCUSSION...
332 AM CDT

MAIN FORECAST CONCERNS/CHALLENGES ARE WITH CLOUD COVER AND TEMPS
TODAY...AND THEN INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS
LATE WEDNESDAY NIGHT INTO THURSDAY AND THURSDAY NIGHT.

COLD FRONT NOW SOUTH OF THE CWA EARLY THIS MORNING AS LOW STRATUS
HAS MOVED OVER MUCH OF THE REGION...WHILE TEMPS CONTINUE TO FALL
INTO THE 40S AND 50S UNDER A STEADY NORTHEAST WIND. WITH ISOLATED
SHOWERS NOW EAST OF THE CWA EXPECT DRY CONDITIONS TODAY BUT WITH
THIS STRATUS LIKELY HANGING AROUND FOR SOME TIME THIS MORNING.
GUIDANCE APPEARING TO BE TOO QUICK SCATTERING OUT THESE CLOUDS
THIS MORNING AND TRYING TO INDICATE THERE WILL BE HOLES BY 12Z.
WITH THIS NOT A LIKELY SCENARIO HAVE GONE MORE PESSIMISTIC WITH
TRENDS THIS MORNING AND DONT HAVE ANY REAL CLEARING UNTIL LATE
MORNING/MIDDAY. MOST AREAS WILL LIKELY OBSERVE A SCATTERING TREND
INTO THE AFTERNOON...BUT WITH AREAS NEAR THE LAKE HOLDING ONTO
THESE CLOUDS FOR MUCH OF THE DAY. DID LOWER HIGH TEMPS AS WELL AS
SLOWED TEMP TREND THIS MORNING...WITH IT POSSIBLE FOR LOCATIONS IN
FAR NORTHEAST ILLINOIS AND NORTHWEST INDIANA NOT MAKING IT OUT OF
THE 50S TODAY.

QUIET BUT COOL NIGHT TONIGHT AS BOUNDARY LAYER FLOW VEERS AND ANY
LINGERING CLOUD COVER COMING OFF THE LAKE PUSHES NORTH INTO
WISCONSIN LATER THIS EVENING...AND MOST LOCATIONS OBSERVING CLEAR
TO PARTLY CLOUDY SKIES. FAIRLY ENERGETIC VORT MAX CURRENTLY
LIFTING NORTH THROUGH THE CENTRAL PLAINS WILL CONTINUE NORTH INTO
THE NORTHERN PLAINS TODAY INTO TONIGHT. AS THIS OCCURS...UPPER
LEVEL RIDGING WILL BE BRIEF TONIGHT AS RIDGE AXIS SHIFTS TO THE
EAST AND WE QUICKLY TRANSITION TOWARDS A SOUTHWEST FLOW PATTERN.
THIS WILL ALLOW FOR A PERIOD OF WAA GOING INTO WEDNESDAY WITH
TEMPS REBOUNDING BACK INTO THE 70S FOR MOST LOCATIONS. MADE
MINIMAL CHANGES TO GOING FORECAST HIGHS ON WEDNESDAY AS
UNCERTAINTY WITH APPROACHING MID/HIGH LEVEL CLOUD COVER COULD PLAY
INTO THE EXTENT OF WARMING THAT OCCURS.

THE BEST WAA/MOIST ADVECTION WILL REMAIN JUST TO THE WEST FOR MOST
OF THE DAY WEDNESDAY BUT THIS WILL CHANGE WEDNESDAY NIGHT AS
MID/UPPER LEVEL TROUGH DIGS ACROSS THE CENTRAL PLAINS...AND
STRENGTHENING LLJ BECOMES ORIENTED TOWARDS NORTHERN ILLINOIS. THIS
COINCIDING WITH FAIRLY ENERGETIC MID LEVEL FLOW...DEVELOPING
PRECIP SHIELD SHOULD BEGIN REACHING MOST LOCATIONS IN NORTHERN
ILLINOIS AFTER THE MIDNIGHT TIME FRAME. DESPITE INCREASING
INSTABILITY WEDNESDAY NIGHT...INSTABILITY AXIS DOES APPEAR TO STAY
JUST TO THE WEST/SOUTHWEST OF THE CWA DURING THIS TIME. ALTHOUGH
THIS MAY BE THE CASE...STRENGTHENING LLJ COULD OFFSET ANY LACKING
INSTABILITY AND SO HAVE MAINTAINED CHANCE THUNDER WORDING OVER THE
ENTIRE CWA...WITH THE FAR WEST AND SOUTHWEST AREAS LIKELY
OBSERVING BEST CHANCES FOR THUNDER. MOISTURE WILL CONTINUE TO
INCREASE DURING THIS TIME AND DO FEEL THERE COULD BE SOME PERIODS
OF MORE MODERATE RAINFALL...BUT THIS WONT LIKELY OCCUR UNTIL VERY
LATE IN THE NIGHT AND TOWARDS EARLY THURSDAY MORNING.

BETTER AGREEMENT OBSERVED WITH VARYING MODELS THIS MORNING
REGARDING APPROACHING MID/UPPER LEVEL TROUGH AND ASSOCIATED
SURFACE FEATURE THURSDAY AND THURSDAY NIGHT. SURFACE LOW SHOULD
LIFT RIGHT ALONG THE MISSISSIPPI RIVER AREA INTO SOUTHWEST
WISCONSIN THURSDAY AND THEN INTO THE GREAT LAKES REGION THURSDAY
NIGHT. CONTINUED LARGE SCALE SUPPORT DURING THIS PERIOD WILL ALLOW
FOR A WET DAY THURSDAY INTO THURSDAY NIGHT AS PERIODS OF SHOWERS
AND THUNDERSTORMS ARE LIKELY. A SLOWER DEPARTING TREND WILL OCCUR
THURSDAY NIGHT...AND DID KEEP LIKELY WORDING LONGER INTO THE
NIGHT. ALTHOUGH MOISTURE AND INSTABILITY WILL CONTINUE TO INCREASE
DURING THIS TIME...IT DOES LOOK LIKE THE BEST INSTABILITY WILL
REMAIN SOUTH OF THE CWA. SO AT THIS TIME...AM NOT OVERLY CONCERNED
WITH ANY SEVERE POTENTIAL BUT AM MORE CONCERNED WITH HEAVY
RAINFALL AND POSSIBLE LOCALIZED FLOODING...ESPECIALLY AS THE BEST
OVERALL MOIST ADVECTION OCCURS INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KILX 300813
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
313 AM CDT Tue Sep 30 2014

.SHORT TERM...(Today)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Short-term forecast concerns include potential for dense fog across
the southern KILX CWA, as well as, approaching deck of low clouds
across the north.  Clear skies/light winds have once again led to
the development of fog early this morning, particularly from the Saint
Louis area eastward across southern Illinois.  HRRR shows fog
becoming dense across this area over the next few hours before
dissipating after 8am.  So far the fog has not become widespread or
dense, but based on forecast soundings and the HRRR, have included
patchy dense fog south of I-70.  Have also issued a Special Weather
Statement to highlight the low visbys.

07z/2am surface analysis shows cold front settling southward into
central Illinois, with a widespread area of low clouds noted to the
north of the boundary across the Great Lakes into north-central
Illinois.  Latest IR satellite imagery shows leading edge of clouds
along the I-74 corridor.  Main questions today will be how far south
these clouds will push and whether or not they will clear out this
afternoon.  Satellite timing tools suggest the clouds will reach a
Rushville to Mattoon line by daybreak, but additional southward
progress appears unlikely as frontal boundary stalls.  Will
therefore go with a cloudy forecast across the northern two-thirds
of the CWA this morning, with mostly sunny skies across the far
south.  Despite continued northeasterly flow behind the front,
forecast soundings indicate a gradual dissipation of low-level
moisture as the day progresses.  Have gone with decreasing clouds
through the afternoon accordingly.  Due to the cloud cover and shift
in wind direction, temps will be quite a bit cooler today than in
recent days, with afternoon highs ranging from the upper 60s
along/north of I-74 to around 80 far south.


&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Winds will veer to the southeast on Wednesday in response to an
approaching upper wave and its associated cold front.  As a result,
temperatures will rise back into the upper 70s and lower 80s.  As a
deep upper trough slowly approaches from the west, surface low
pressure is expected to develop over the Southern Plains on
Wednesday then lift northward into the Great Lakes by Thursday
night.  Warm-advection showers/thunder will develop ahead of this
system Wednesday night: however, all model guidance keeps any precip
focused mainly across the western half of the CWA.  Given this
slowing trend, have removed PoPs for all locations along/east of a
Paris to Effingham line.  Further west, will go with likely PoPs
across the Illinois River Valley after midnight.  As surface low
deepens and tracks just west of the area on Thursday, strong S/SW
flow will provide one more very warm day with highs in the upper
70s/lower 80s.  Showers and thunderstorms will develop in advance of
a slowly approaching cold front, mainly focused across the west.
With strong upper dynamics in place and increasing amounts of
moisture flowing northward from the Gulf of Mexico, a few strong to
severe thunderstorms will be possible Thursday afternoon across
west-central Illinois.  Once low lifts into the Great Lakes, front
will get a solid push eastward by Thursday evening.  Will go with
categorical PoPs across the board as the boundary interacts with a
moist and moderately unstable environment.

Cold front will push into Indiana by early Friday morning, with
perhaps a few lingering showers across the Wabash River Valley.
Main weather story late in the week will be the sharply cooler
conditions.  850mb temps are progged to drop into the 0 to -2C range
by Saturday morning, supporting daytime highs only in the lower
to middle 60s and overnight lows in the lower 40s this weekend.
Airmass will slowly moderate by early next week, with temperatures
climbing back to around 70 by Monday.


&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1110 PM CDT MON SEP 29 2014

Cold front has just passed Pontiac and continues to make steady
progress south-southwest into our forecast area. Based on the
present movement, it appears it will push across PIA and BMI
between 05-06z with our southern TAF sites seeing FROPA in the
08z-10z time frame. Winds initially after frontal passage will
gust up to 20 kts from the northeast (020-050) but will begin
to diminish an hour or two after passage. Based on the latest
satellite trends, the MVFR and local IFR cigs will follow within
an hour of the wind shift with cigs in the 500-1000 foot range,
especially at KBMI with even the possibility for a little drizzle
and vsby restriction in fog for an hour or two as the lower clouds
settle in. The real challenge will be how quickly the lower cigs
are able to lift late tomorrow morning or early afternoon with
the low level moisture trapped under a developing subsidence
inversion. Latest guidance off the NAM-WRF and HRRR continues to
suggest we will see some breaks develop by late morning or early
afternoon so will continue with the previous trends in the TAFs
in scattering out the lower cigs by afternoon with some broken
VFR cigs into the late afternoon hours.

Ahead of the front, surface winds will be light and variable and
then switch into the northeast after frontal passage with speeds
in the 10 to 15 kts with a few gusts around 20 kts for a brief
time. Winds on Tuesday will be from the northeast at 8 to 15 kts.


&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Smith






000
FXUS63 KILX 300813
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
313 AM CDT Tue Sep 30 2014

.SHORT TERM...(Today)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Short-term forecast concerns include potential for dense fog across
the southern KILX CWA, as well as, approaching deck of low clouds
across the north.  Clear skies/light winds have once again led to
the development of fog early this morning, particularly from the Saint
Louis area eastward across southern Illinois.  HRRR shows fog
becoming dense across this area over the next few hours before
dissipating after 8am.  So far the fog has not become widespread or
dense, but based on forecast soundings and the HRRR, have included
patchy dense fog south of I-70.  Have also issued a Special Weather
Statement to highlight the low visbys.

07z/2am surface analysis shows cold front settling southward into
central Illinois, with a widespread area of low clouds noted to the
north of the boundary across the Great Lakes into north-central
Illinois.  Latest IR satellite imagery shows leading edge of clouds
along the I-74 corridor.  Main questions today will be how far south
these clouds will push and whether or not they will clear out this
afternoon.  Satellite timing tools suggest the clouds will reach a
Rushville to Mattoon line by daybreak, but additional southward
progress appears unlikely as frontal boundary stalls.  Will
therefore go with a cloudy forecast across the northern two-thirds
of the CWA this morning, with mostly sunny skies across the far
south.  Despite continued northeasterly flow behind the front,
forecast soundings indicate a gradual dissipation of low-level
moisture as the day progresses.  Have gone with decreasing clouds
through the afternoon accordingly.  Due to the cloud cover and shift
in wind direction, temps will be quite a bit cooler today than in
recent days, with afternoon highs ranging from the upper 60s
along/north of I-74 to around 80 far south.


&&

.LONG TERM...(Tonight through Monday)
ISSUED AT 312 AM CDT TUE SEP 30 2014

Winds will veer to the southeast on Wednesday in response to an
approaching upper wave and its associated cold front.  As a result,
temperatures will rise back into the upper 70s and lower 80s.  As a
deep upper trough slowly approaches from the west, surface low
pressure is expected to develop over the Southern Plains on
Wednesday then lift northward into the Great Lakes by Thursday
night.  Warm-advection showers/thunder will develop ahead of this
system Wednesday night: however, all model guidance keeps any precip
focused mainly across the western half of the CWA.  Given this
slowing trend, have removed PoPs for all locations along/east of a
Paris to Effingham line.  Further west, will go with likely PoPs
across the Illinois River Valley after midnight.  As surface low
deepens and tracks just west of the area on Thursday, strong S/SW
flow will provide one more very warm day with highs in the upper
70s/lower 80s.  Showers and thunderstorms will develop in advance of
a slowly approaching cold front, mainly focused across the west.
With strong upper dynamics in place and increasing amounts of
moisture flowing northward from the Gulf of Mexico, a few strong to
severe thunderstorms will be possible Thursday afternoon across
west-central Illinois.  Once low lifts into the Great Lakes, front
will get a solid push eastward by Thursday evening.  Will go with
categorical PoPs across the board as the boundary interacts with a
moist and moderately unstable environment.

Cold front will push into Indiana by early Friday morning, with
perhaps a few lingering showers across the Wabash River Valley.
Main weather story late in the week will be the sharply cooler
conditions.  850mb temps are progged to drop into the 0 to -2C range
by Saturday morning, supporting daytime highs only in the lower
to middle 60s and overnight lows in the lower 40s this weekend.
Airmass will slowly moderate by early next week, with temperatures
climbing back to around 70 by Monday.


&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1110 PM CDT MON SEP 29 2014

Cold front has just passed Pontiac and continues to make steady
progress south-southwest into our forecast area. Based on the
present movement, it appears it will push across PIA and BMI
between 05-06z with our southern TAF sites seeing FROPA in the
08z-10z time frame. Winds initially after frontal passage will
gust up to 20 kts from the northeast (020-050) but will begin
to diminish an hour or two after passage. Based on the latest
satellite trends, the MVFR and local IFR cigs will follow within
an hour of the wind shift with cigs in the 500-1000 foot range,
especially at KBMI with even the possibility for a little drizzle
and vsby restriction in fog for an hour or two as the lower clouds
settle in. The real challenge will be how quickly the lower cigs
are able to lift late tomorrow morning or early afternoon with
the low level moisture trapped under a developing subsidence
inversion. Latest guidance off the NAM-WRF and HRRR continues to
suggest we will see some breaks develop by late morning or early
afternoon so will continue with the previous trends in the TAFs
in scattering out the lower cigs by afternoon with some broken
VFR cigs into the late afternoon hours.

Ahead of the front, surface winds will be light and variable and
then switch into the northeast after frontal passage with speeds
in the 10 to 15 kts with a few gusts around 20 kts for a brief
time. Winds on Tuesday will be from the northeast at 8 to 15 kts.


&&

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

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Smith







000
FXUS63 KLOT 300759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 AM CDT TUE SEP 30 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 300759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 AM CDT TUE SEP 30 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 300759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 AM CDT TUE SEP 30 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 300759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 AM CDT TUE SEP 30 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB

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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

STRONG NORTHERLY WINDS WILL GRADUALLY DECREASE IN SPEED INTO THE
AFTERNOON AS HIGH PRESSURE RIDGING MOVES ACROSS LAKE MICHIGAN. THE
PRESSURE GRADIENT WILL TIGHTEN UP SOMEWHAT WEDNESDAY AS THE RIDGE
SHIFTS EAST AND LOW PRESSURE OVER THE CENTRAL HIGH PLAINS TRACKS
NORTH TO MANITOBA BY WEDNESDAY AFTERNOON. THIS WILL ALLOW WINDS TO
SHIFT TO THE SOUTHEAST TONIGHT. WILL CONTINUE WITH THE SMALL CRAFT
ADVISORY THROUGH THIS AFTERNOON. STEADY SOUTH TO SOUTHEAST WINDS
WILL CONTINUE INTO THURSDAY WHEN LOW PRESSURE DEVELOPS OVER THE
TEXAS/OKLAHOMA PANHANDLE AND TRACKS NORTHEAST TO THE U.P. OF
MICHIGAN THURSDAY NIGHT. FORECAST MODELS HAVE STRUGGLED WITH THE
TRACK AND INTENSITY OF THIS SYSTEM THOUGH THERE HAS BEEN VERY
GENERAL AGREEMENT IN THE LOW TRACKING NORTHWEST OF THE LAKE AND
DEEPENING WHILE DOING SO. WHILE SPECIFICS ARE STILL UNDETERMINED
THE STAGE WILL BE SET FOR A PERIOD OF STRONGER WINDS ACROSS THE
LAKE...STARTING OUT SOUTHERLY THEN TURNING WESTERLY AS A COLD
FRONT PASSES THURSDAY NIGHT. SEVERAL OTHER MORE SUBTLE SURFACE
TROUGHS MAY CROSS FRIDAY INTO SATURDAY ALLOWING WINDS TO FLUCTUATE
BETWEEN WEST AND NORTHWEST. A PERIOD OF GALES STILL LOOKS
POSSIBLE...PRIMARILY AFTER THE PASSAGE OF THE MAIN FRONT AS COLDER
AIR SPREADS IN. WIND SPEEDS WILL GRADUALLY EASE GOING INTO SUNDAY.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 300600
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
100 AM CDT TUE SEP 30 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB


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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 300600
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
100 AM CDT TUE SEP 30 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* CIGS AROUND 1000 FT CONTINUING THROUGH THE OVERNIGHT WITH
  OCCASIONAL LOWERING TO 800-900 FT...ESPECIALLY AT ORD.

* MVFR CIGS EXPECTED TO CONTINUE INTO THE EVENING WITH LIFTING
  DURING THE AFTERNOON.

* NORTHEAST WINDS WILL DIMINISH LATE TONIGHT AND REMAIN NEAR 10 KT
  THIS AFTERNOON.

MDB

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

LOW MVFR CIGS CONTINUE TO BE SPREAD ACROSS THE THE TERMINALS AND
WILL REMAIN IN PLACE OVERNIGHT. SOME PERIODIC LOWERING TO IFR WILL
LIKELY OCCUR BUT CIGS UPSTREAM HAVE IMPROVED SLIGHTLY IN SPOTS
LIKELY BECAUSE OF AN INFLUX OF DRIER AIR. EXPECT THAT THE LOWEST
CIGS MAY BE OCCURRING NOW THROUGH THE NEXT FEW HOURS THEN MAY
START TO LIFT TOWARDS DAYBREAK...WITH STEADIER LIFTING THROUGH THE
MORNING. AM THINKING THAT RFD/DPA MAY SCATTER DURING THE AFTERNOON
AT SOME POINT WITH FLOW OFF THE LAKE KEEPING CLOUD COVER BROKEN AT
ORD/MDW/GYY THOUGH SOME SCATTERING COULD OCCUR. LOW LEVEL FLOW AT
CLOUD LEVEL TURNS SOUTHEASTERLY THIS EVENING WHICH MAY PROMOTE AN
INCREASE IN CLOUD COVER AS WELL AS PUSH IT FURTHER INLAND.
THEREFORE A RETURN TO MVFR CIGS IS POSSIBLE AT DPA/RFD THIS
EVENING. WILL KEEP COVERAGE SCATTERED FOR NOW. NORTHEAST SURFACE
WINDS WILL BE GRADUALLY EASING THROUGH THE REST OF THE NIGHT AND
GENERALLY BE NEAR 10 KT FOR THE MORNING/AFTERNOON BEFORE TURNING
EAST THIS EVENING.

MDB


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

* HIGH CONFIDENCE IN CIGS HOVERING AROUND 1000 FT OVERNIGHT.
  MEDIUM CONFIDENCE IN OCCASIONAL LOWERING BELOW 1000
  FT...ESPECIALLY AT ORD.

* MEDIUM-HIGH CONFIDENCE IN MVFR CONTINUING THROUGH THE DAY...HIGH
  CONFIDENCE IN BASES LIFTING DURING THE AFTERNOON. SCATTERING IS
  POSSIBLE.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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





000
FXUS63 KILX 300414
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1114 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 852 PM CDT MON SEP 29 2014

The cold front has slipped south of Joliet over the past hour and
continues to make steady progress towards our area this evening.
Not much in the way of weather other than a wind shift and an
increase in clouds. Based on the present movement, it appears the
boundary will shift south thru Peoria and Bloomington between
Midnight and 2 am. Radar mosaic showing a decreasing area of
showers north of the boundary, so not expecting any measureable
precip with the front, other than the possibility for a brief
period of drizzle as the low clouds settle south into the forecast
area after midnight. Other than some adjustments to the evening
temperature trends, no other changes were needed to the grids that
would require an evening update.

&&

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1110 PM CDT MON SEP 29 2014

Cold front has just passed Pontiac and continues to make steady
progress south-southwest into our forecast area. Based on the
present movement, it appears it will push across PIA and BMI
between 05-06z with our southern TAF sites seeing FROPA in the
08z-10z time frame. Winds initially after frontal passage will
gust up to 20 kts from the northeast (020-050) but will begin
to diminish an hour or two after passage. Based on the latest
satellite trends, the MVFR and local IFR cigs will follow within
an hour of the wind shift with cigs in the 500-1000 foot range,
especially at KBMI with even the possibility for a little drizzle
and vsby restriction in fog for an hour or two as the lower clouds
settle in. The real challenge will be how quickly the lower cigs
are able to lift late tomorrow morning or early afternoon with
the low level moisture trapped under a developing subsidence
inversion. Latest guidance off the NAM-WRF and HRRR continues to
suggest we will see some breaks develop by late morning or early
afternoon so will continue with the previous trends in the TAFs
in scattering out the lower cigs by afternoon with some broken
VFR cigs into the late afternoon hours.

Ahead of the front, surface winds will be light and variable and
then switch into the northeast after frontal passage with speeds
in the 10 to 15 kts with a few gusts around 20 kts for a brief
time. Winds on Tuesday will be from the northeast at 8 to 15 kts.

&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith





000
FXUS63 KILX 300414
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1114 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 852 PM CDT MON SEP 29 2014

The cold front has slipped south of Joliet over the past hour and
continues to make steady progress towards our area this evening.
Not much in the way of weather other than a wind shift and an
increase in clouds. Based on the present movement, it appears the
boundary will shift south thru Peoria and Bloomington between
Midnight and 2 am. Radar mosaic showing a decreasing area of
showers north of the boundary, so not expecting any measureable
precip with the front, other than the possibility for a brief
period of drizzle as the low clouds settle south into the forecast
area after midnight. Other than some adjustments to the evening
temperature trends, no other changes were needed to the grids that
would require an evening update.

&&

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1110 PM CDT MON SEP 29 2014

Cold front has just passed Pontiac and continues to make steady
progress south-southwest into our forecast area. Based on the
present movement, it appears it will push across PIA and BMI
between 05-06z with our southern TAF sites seeing FROPA in the
08z-10z time frame. Winds initially after frontal passage will
gust up to 20 kts from the northeast (020-050) but will begin
to diminish an hour or two after passage. Based on the latest
satellite trends, the MVFR and local IFR cigs will follow within
an hour of the wind shift with cigs in the 500-1000 foot range,
especially at KBMI with even the possibility for a little drizzle
and vsby restriction in fog for an hour or two as the lower clouds
settle in. The real challenge will be how quickly the lower cigs
are able to lift late tomorrow morning or early afternoon with
the low level moisture trapped under a developing subsidence
inversion. Latest guidance off the NAM-WRF and HRRR continues to
suggest we will see some breaks develop by late morning or early
afternoon so will continue with the previous trends in the TAFs
in scattering out the lower cigs by afternoon with some broken
VFR cigs into the late afternoon hours.

Ahead of the front, surface winds will be light and variable and
then switch into the northeast after frontal passage with speeds
in the 10 to 15 kts with a few gusts around 20 kts for a brief
time. Winds on Tuesday will be from the northeast at 8 to 15 kts.

&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith





000
FXUS63 KILX 300414
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1114 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 852 PM CDT MON SEP 29 2014

The cold front has slipped south of Joliet over the past hour and
continues to make steady progress towards our area this evening.
Not much in the way of weather other than a wind shift and an
increase in clouds. Based on the present movement, it appears the
boundary will shift south thru Peoria and Bloomington between
Midnight and 2 am. Radar mosaic showing a decreasing area of
showers north of the boundary, so not expecting any measureable
precip with the front, other than the possibility for a brief
period of drizzle as the low clouds settle south into the forecast
area after midnight. Other than some adjustments to the evening
temperature trends, no other changes were needed to the grids that
would require an evening update.

&&

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1110 PM CDT MON SEP 29 2014

Cold front has just passed Pontiac and continues to make steady
progress south-southwest into our forecast area. Based on the
present movement, it appears it will push across PIA and BMI
between 05-06z with our southern TAF sites seeing FROPA in the
08z-10z time frame. Winds initially after frontal passage will
gust up to 20 kts from the northeast (020-050) but will begin
to diminish an hour or two after passage. Based on the latest
satellite trends, the MVFR and local IFR cigs will follow within
an hour of the wind shift with cigs in the 500-1000 foot range,
especially at KBMI with even the possibility for a little drizzle
and vsby restriction in fog for an hour or two as the lower clouds
settle in. The real challenge will be how quickly the lower cigs
are able to lift late tomorrow morning or early afternoon with
the low level moisture trapped under a developing subsidence
inversion. Latest guidance off the NAM-WRF and HRRR continues to
suggest we will see some breaks develop by late morning or early
afternoon so will continue with the previous trends in the TAFs
in scattering out the lower cigs by afternoon with some broken
VFR cigs into the late afternoon hours.

Ahead of the front, surface winds will be light and variable and
then switch into the northeast after frontal passage with speeds
in the 10 to 15 kts with a few gusts around 20 kts for a brief
time. Winds on Tuesday will be from the northeast at 8 to 15 kts.

&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith





000
FXUS63 KILX 300414
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1114 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 852 PM CDT MON SEP 29 2014

The cold front has slipped south of Joliet over the past hour and
continues to make steady progress towards our area this evening.
Not much in the way of weather other than a wind shift and an
increase in clouds. Based on the present movement, it appears the
boundary will shift south thru Peoria and Bloomington between
Midnight and 2 am. Radar mosaic showing a decreasing area of
showers north of the boundary, so not expecting any measureable
precip with the front, other than the possibility for a brief
period of drizzle as the low clouds settle south into the forecast
area after midnight. Other than some adjustments to the evening
temperature trends, no other changes were needed to the grids that
would require an evening update.

&&

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1110 PM CDT MON SEP 29 2014

Cold front has just passed Pontiac and continues to make steady
progress south-southwest into our forecast area. Based on the
present movement, it appears it will push across PIA and BMI
between 05-06z with our southern TAF sites seeing FROPA in the
08z-10z time frame. Winds initially after frontal passage will
gust up to 20 kts from the northeast (020-050) but will begin
to diminish an hour or two after passage. Based on the latest
satellite trends, the MVFR and local IFR cigs will follow within
an hour of the wind shift with cigs in the 500-1000 foot range,
especially at KBMI with even the possibility for a little drizzle
and vsby restriction in fog for an hour or two as the lower clouds
settle in. The real challenge will be how quickly the lower cigs
are able to lift late tomorrow morning or early afternoon with
the low level moisture trapped under a developing subsidence
inversion. Latest guidance off the NAM-WRF and HRRR continues to
suggest we will see some breaks develop by late morning or early
afternoon so will continue with the previous trends in the TAFs
in scattering out the lower cigs by afternoon with some broken
VFR cigs into the late afternoon hours.

Ahead of the front, surface winds will be light and variable and
then switch into the northeast after frontal passage with speeds
in the 10 to 15 kts with a few gusts around 20 kts for a brief
time. Winds on Tuesday will be from the northeast at 8 to 15 kts.

&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith





000
FXUS63 KLOT 300313
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1013 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NORTH-NORTHEAST WINDS GUSTING NEAR 20 KT GRADUALLY DIMINISHING
  INTO TUESDAY MORNING.
* IFR/MVFR CIGS 800-1200 FT WITH A WINDOW OF LIGHT RAIN OR DRIZZLE
  THROUGH ABOUT 3 AM.
* NORTHEAST WINDS AND MVFR CIGS LINGER TUESDAY.

RATZER

//DISCUSSION...UPDATED 03Z...

COLD FRONT HAS PUSHED SOUTH OF TERMINALS THIS EVENING...WITH GUSTY
NORTHEAST WINDS AND HIGH IFR/LOW MVFR CIGS 800-1000 FT HAVING
SPREAD ACROSS THE AREA. AN UPPER DISTURBANCE WILL PRODUCE
SCATTERED SHOWERS/LIGHT RAIN AT TIMES THROUGH 3-4 AM...THOUGH
COVERAGE IS NOT EXPECTED TO BE GREAT. OVERALL...WINDS WILL VERY
SLOWLY DIMINISH THROUGH THE NIGHT WITH CIGS REMAINING 800-1200 FT
WITH SLOW IMPROVEMENT EXPECTED TUESDAY MORNING.

PREVIOUS DISCUSSION FROM 00Z...

STRONG COLD FRONT HAS SURGED SOUTH DOWN THE LAKE ACROSS FAR
NORTHEAST IL/NORTHWEST INDIANA AS OF 2330Z. NORTHEAST WINDS
GUSTING AROUND 25 KT EARLY WILL SLOWLY DIMINISH OVERNIGHT AS
SURFACE HIGH PRESSURE BUILDS ACROSS THE UPPER MIDWEST. IFR CIGS
WERE NOTED SPREADING ACROSS SOUTHEAST WI/NORTHEAST IL...AND EXPECT
ORD/MDW TO DEVELOP IFR CIGS 700-800 FT WITHIN THE HOUR AND PERSIST
THROUGH THE EVENING.

NORTHEAST WINDS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE
10-15 KT RANGE AND BECOME MORE EASTERLY TUESDAY AS THE GRADIENT
BEGINS TO WEAKEN WITH THE APPROACH OF THE SURFACE HIGH FROM THE
NORTH. COOL/MOIST LOW LEVELS BENEATH SUBSIDENCE INVERSION EXPECTED
TO MAINTAIN BKN-OVC MVFR CIGS RISING INTO THE 1500-2000 FT RANGE
BY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* LOW-MEDIUM CONFIDENCE IN LIGHT RAIN COVERAGE...OTHERWISE HIGH
  CONFIDENCE ALL REMAINING ELEMENTS.

RATZER

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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







000
FXUS63 KLOT 300313
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1013 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NORTH-NORTHEAST WINDS GUSTING NEAR 20 KT GRADUALLY DIMINISHING
  INTO TUESDAY MORNING.
* IFR/MVFR CIGS 800-1200 FT WITH A WINDOW OF LIGHT RAIN OR DRIZZLE
  THROUGH ABOUT 3 AM.
* NORTHEAST WINDS AND MVFR CIGS LINGER TUESDAY.

RATZER

//DISCUSSION...UPDATED 03Z...

COLD FRONT HAS PUSHED SOUTH OF TERMINALS THIS EVENING...WITH GUSTY
NORTHEAST WINDS AND HIGH IFR/LOW MVFR CIGS 800-1000 FT HAVING
SPREAD ACROSS THE AREA. AN UPPER DISTURBANCE WILL PRODUCE
SCATTERED SHOWERS/LIGHT RAIN AT TIMES THROUGH 3-4 AM...THOUGH
COVERAGE IS NOT EXPECTED TO BE GREAT. OVERALL...WINDS WILL VERY
SLOWLY DIMINISH THROUGH THE NIGHT WITH CIGS REMAINING 800-1200 FT
WITH SLOW IMPROVEMENT EXPECTED TUESDAY MORNING.

PREVIOUS DISCUSSION FROM 00Z...

STRONG COLD FRONT HAS SURGED SOUTH DOWN THE LAKE ACROSS FAR
NORTHEAST IL/NORTHWEST INDIANA AS OF 2330Z. NORTHEAST WINDS
GUSTING AROUND 25 KT EARLY WILL SLOWLY DIMINISH OVERNIGHT AS
SURFACE HIGH PRESSURE BUILDS ACROSS THE UPPER MIDWEST. IFR CIGS
WERE NOTED SPREADING ACROSS SOUTHEAST WI/NORTHEAST IL...AND EXPECT
ORD/MDW TO DEVELOP IFR CIGS 700-800 FT WITHIN THE HOUR AND PERSIST
THROUGH THE EVENING.

NORTHEAST WINDS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE
10-15 KT RANGE AND BECOME MORE EASTERLY TUESDAY AS THE GRADIENT
BEGINS TO WEAKEN WITH THE APPROACH OF THE SURFACE HIGH FROM THE
NORTH. COOL/MOIST LOW LEVELS BENEATH SUBSIDENCE INVERSION EXPECTED
TO MAINTAIN BKN-OVC MVFR CIGS RISING INTO THE 1500-2000 FT RANGE
BY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* LOW-MEDIUM CONFIDENCE IN LIGHT RAIN COVERAGE...OTHERWISE HIGH
  CONFIDENCE ALL REMAINING ELEMENTS.

RATZER

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 300313
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1013 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NORTH-NORTHEAST WINDS GUSTING NEAR 20 KT GRADUALLY DIMINISHING
  INTO TUESDAY MORNING.
* IFR/MVFR CIGS 800-1200 FT WITH A WINDOW OF LIGHT RAIN OR DRIZZLE
  THROUGH ABOUT 3 AM.
* NORTHEAST WINDS AND MVFR CIGS LINGER TUESDAY.

RATZER

//DISCUSSION...UPDATED 03Z...

COLD FRONT HAS PUSHED SOUTH OF TERMINALS THIS EVENING...WITH GUSTY
NORTHEAST WINDS AND HIGH IFR/LOW MVFR CIGS 800-1000 FT HAVING
SPREAD ACROSS THE AREA. AN UPPER DISTURBANCE WILL PRODUCE
SCATTERED SHOWERS/LIGHT RAIN AT TIMES THROUGH 3-4 AM...THOUGH
COVERAGE IS NOT EXPECTED TO BE GREAT. OVERALL...WINDS WILL VERY
SLOWLY DIMINISH THROUGH THE NIGHT WITH CIGS REMAINING 800-1200 FT
WITH SLOW IMPROVEMENT EXPECTED TUESDAY MORNING.

PREVIOUS DISCUSSION FROM 00Z...

STRONG COLD FRONT HAS SURGED SOUTH DOWN THE LAKE ACROSS FAR
NORTHEAST IL/NORTHWEST INDIANA AS OF 2330Z. NORTHEAST WINDS
GUSTING AROUND 25 KT EARLY WILL SLOWLY DIMINISH OVERNIGHT AS
SURFACE HIGH PRESSURE BUILDS ACROSS THE UPPER MIDWEST. IFR CIGS
WERE NOTED SPREADING ACROSS SOUTHEAST WI/NORTHEAST IL...AND EXPECT
ORD/MDW TO DEVELOP IFR CIGS 700-800 FT WITHIN THE HOUR AND PERSIST
THROUGH THE EVENING.

NORTHEAST WINDS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE
10-15 KT RANGE AND BECOME MORE EASTERLY TUESDAY AS THE GRADIENT
BEGINS TO WEAKEN WITH THE APPROACH OF THE SURFACE HIGH FROM THE
NORTH. COOL/MOIST LOW LEVELS BENEATH SUBSIDENCE INVERSION EXPECTED
TO MAINTAIN BKN-OVC MVFR CIGS RISING INTO THE 1500-2000 FT RANGE
BY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* LOW-MEDIUM CONFIDENCE IN LIGHT RAIN COVERAGE...OTHERWISE HIGH
  CONFIDENCE ALL REMAINING ELEMENTS.

RATZER

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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







000
FXUS63 KLOT 300313
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1013 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* NORTH-NORTHEAST WINDS GUSTING NEAR 20 KT GRADUALLY DIMINISHING
  INTO TUESDAY MORNING.
* IFR/MVFR CIGS 800-1200 FT WITH A WINDOW OF LIGHT RAIN OR DRIZZLE
  THROUGH ABOUT 3 AM.
* NORTHEAST WINDS AND MVFR CIGS LINGER TUESDAY.

RATZER

//DISCUSSION...UPDATED 03Z...

COLD FRONT HAS PUSHED SOUTH OF TERMINALS THIS EVENING...WITH GUSTY
NORTHEAST WINDS AND HIGH IFR/LOW MVFR CIGS 800-1000 FT HAVING
SPREAD ACROSS THE AREA. AN UPPER DISTURBANCE WILL PRODUCE
SCATTERED SHOWERS/LIGHT RAIN AT TIMES THROUGH 3-4 AM...THOUGH
COVERAGE IS NOT EXPECTED TO BE GREAT. OVERALL...WINDS WILL VERY
SLOWLY DIMINISH THROUGH THE NIGHT WITH CIGS REMAINING 800-1200 FT
WITH SLOW IMPROVEMENT EXPECTED TUESDAY MORNING.

PREVIOUS DISCUSSION FROM 00Z...

STRONG COLD FRONT HAS SURGED SOUTH DOWN THE LAKE ACROSS FAR
NORTHEAST IL/NORTHWEST INDIANA AS OF 2330Z. NORTHEAST WINDS
GUSTING AROUND 25 KT EARLY WILL SLOWLY DIMINISH OVERNIGHT AS
SURFACE HIGH PRESSURE BUILDS ACROSS THE UPPER MIDWEST. IFR CIGS
WERE NOTED SPREADING ACROSS SOUTHEAST WI/NORTHEAST IL...AND EXPECT
ORD/MDW TO DEVELOP IFR CIGS 700-800 FT WITHIN THE HOUR AND PERSIST
THROUGH THE EVENING.

NORTHEAST WINDS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE
10-15 KT RANGE AND BECOME MORE EASTERLY TUESDAY AS THE GRADIENT
BEGINS TO WEAKEN WITH THE APPROACH OF THE SURFACE HIGH FROM THE
NORTH. COOL/MOIST LOW LEVELS BENEATH SUBSIDENCE INVERSION EXPECTED
TO MAINTAIN BKN-OVC MVFR CIGS RISING INTO THE 1500-2000 FT RANGE
BY AFTERNOON.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* LOW-MEDIUM CONFIDENCE IN LIGHT RAIN COVERAGE...OTHERWISE HIGH
  CONFIDENCE ALL REMAINING ELEMENTS.

RATZER

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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







000
FXUS63 KILX 300156
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
856 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 852 PM CDT MON SEP 29 2014

The cold front has slipped south of Joliet over the past hour and
continues to make steady progress towards our area this evening.
Not much in the way of weather other than a wind shift and an
increase in clouds. Based on the present movement, it appears the
boundary will shift south thru Peoria and Bloomington between
Midnight and 2 am. Radar mosaic showing a decreasing area of
showers north of the boundary, so not expecting any measureable
precip with the front, other than the possibility for a brief
period of drizzle as the low clouds settle south into the forecast
area after midnight. Other than some adjustments to the evening
temperature trends, no other changes were needed to the grids that
would require an evening update.

&&

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 600 PM CDT MON SEP 29 2014

Cold front expected to bring a period of MVFR and local IFR cigs
and vsbys with it as the boundary settles south into our area later
this evening across the north (KPIA and KBMI from 05z-07z). Models
suggest the southward surge in the front will lessen with time
overnight but still feel it will have enough momentum to pass our
southern TAF sites in the 07z-10z time frame. Along with the low
cigs moving in, there may be a period of drizzle and fog which
will bring vsbys down to between 3-5sm just behind the FROPA. The
MVFR and local IFR cigs are expected to gradually lift aftr 15z
Tuesday as drier air advects in. Surface winds will remain light
and variable ahead of the front with a shift into the northeast
aftr FROPA with speeds initially in the 10 to 15 kt range with a
few gusts around 20 kts possible, especially at KBMI for about an
hour after FROPA. Winds should then become easterly on Tuesday at
8 to 12 kts.


&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith






000
FXUS63 KILX 300156
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
856 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 852 PM CDT MON SEP 29 2014

The cold front has slipped south of Joliet over the past hour and
continues to make steady progress towards our area this evening.
Not much in the way of weather other than a wind shift and an
increase in clouds. Based on the present movement, it appears the
boundary will shift south thru Peoria and Bloomington between
Midnight and 2 am. Radar mosaic showing a decreasing area of
showers north of the boundary, so not expecting any measureable
precip with the front, other than the possibility for a brief
period of drizzle as the low clouds settle south into the forecast
area after midnight. Other than some adjustments to the evening
temperature trends, no other changes were needed to the grids that
would require an evening update.

&&

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 600 PM CDT MON SEP 29 2014

Cold front expected to bring a period of MVFR and local IFR cigs
and vsbys with it as the boundary settles south into our area later
this evening across the north (KPIA and KBMI from 05z-07z). Models
suggest the southward surge in the front will lessen with time
overnight but still feel it will have enough momentum to pass our
southern TAF sites in the 07z-10z time frame. Along with the low
cigs moving in, there may be a period of drizzle and fog which
will bring vsbys down to between 3-5sm just behind the FROPA. The
MVFR and local IFR cigs are expected to gradually lift aftr 15z
Tuesday as drier air advects in. Surface winds will remain light
and variable ahead of the front with a shift into the northeast
aftr FROPA with speeds initially in the 10 to 15 kt range with a
few gusts around 20 kts possible, especially at KBMI for about an
hour after FROPA. Winds should then become easterly on Tuesday at
8 to 12 kts.


&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith







000
FXUS63 KLOT 292342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* NORTHEAST WINDS GUSTING 25 KT THIS EVENING.
* IFR CIGS WITH A WINDOW OF LIGHT RAIN OR DRIZZLE EXPECTED.
* MVFR CIGS LINGER TUESDAY.

RATZER

//DISCUSSION...UPDATED 00Z...

STRONG COLD FRONT HAS SURGED SOUTH DOWN THE LAKE ACROSS FAR
NORTHEAST IL/NORTHWEST INDIANA AS OF 2330Z. NORTHEAST WINDS
GUSTING AROUND 25 KT EARLY WILL SLOWLY DIMINISH OVERNIGHT AS
SURFACE HIGH PRESSURE BUILDS ACROSS THE UPPER MIDWEST. IFR CIGS
WERE NOTED SPREADING ACROSS SOUTHEAST WI/NORTHEAST IL...AND EXPECT
ORD/MDW TO DEVELOP IFR CIGS 700-800 FT WITHIN THE HOUR AND PERSIST
THROUGH THE EVENING.

NORTHEAST WINDS WILL CONTINUE TO GRADUALLY DIMINISH THROUGH THE
10-15 KT RANGE AND BECOME MORE EASTERLY TUESDAY AS THE GRADIENT
BEGINS TO WEAKEN WITH THE APPROACH OF THE SURFACE HIGH FROM THE
NORTH. COOL/MOIST LOW LEVELS BENEATH SUBSIDENCE INVERSION EXPECTED
TO MAINTAIN BKN-OVC MVFR CIGS RISING INTO THE 1500-2000 FT RANGE
BY AFTERNOON.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* HIGH CONFIDENCE IN WIND AND IFR/MVFR CIG TRENDS.

* LOW-MEDIUM CONFIDENCE IN A PERIOD OF LIGHT RAIN OR DRIZZLE
  TONIGHT.

RATZER

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

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

SUNDAY...SLIGHT CHANCE SHRA. WEST-SOUTHWEST WINDS.

RATZER

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 7 PM TUESDAY.

&&

$$

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

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






000
FXUS63 KILX 292304
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
604 PM CDT Mon Sep 29 2014

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 600 PM CDT MON SEP 29 2014

Cold front expected to bring a period of MVFR and local IFR cigs
and vsbys with it as the boundary settles south into our area later
this evening across the north (KPIA and KBMI from 05z-07z). Models
suggest the southward surge in the front will lessen with time
overnight but still feel it will have enough momentum to pass our
southern TAF sites in the 07z-10z time frame. Along with the low
cigs moving in, there may be a period of drizzle and fog which
will bring vsbys down to between 3-5sm just behind the FROPA. The
MVFR and local IFR cigs are expected to gradually lift aftr 15z
Tuesday as drier air advects in. Surface winds will remain light
and variable ahead of the front with a shift into the northeast
aftr FROPA with speeds initially in the 10 to 15 kt range with a
few gusts around 20 kts possible, especially at KBMI for about an
hour after FROPA. Winds should then become easterly on Tuesday at
8 to 12 kts.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith




000
FXUS63 KILX 292304
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
604 PM CDT Mon Sep 29 2014

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
ISSUED AT 600 PM CDT MON SEP 29 2014

Cold front expected to bring a period of MVFR and local IFR cigs
and vsbys with it as the boundary settles south into our area later
this evening across the north (KPIA and KBMI from 05z-07z). Models
suggest the southward surge in the front will lessen with time
overnight but still feel it will have enough momentum to pass our
southern TAF sites in the 07z-10z time frame. Along with the low
cigs moving in, there may be a period of drizzle and fog which
will bring vsbys down to between 3-5sm just behind the FROPA. The
MVFR and local IFR cigs are expected to gradually lift aftr 15z
Tuesday as drier air advects in. Surface winds will remain light
and variable ahead of the front with a shift into the northeast
aftr FROPA with speeds initially in the 10 to 15 kt range with a
few gusts around 20 kts possible, especially at KBMI for about an
hour after FROPA. Winds should then become easterly on Tuesday at
8 to 12 kts.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith





000
FXUS63 KLOT 292212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
512 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST NEXT 60-90 MINUTES OR
  SO. GUSTS ABOVE 20 KT EXPECTED WITH WIND SHIFT.

* MVFR/IFR CIGS OVERSPREADING TERMINALS 1-2 HOURS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

RATZER

//DISCUSSION...UPDATED 22Z...

COLD FRONTAL BOUNDARY SURGING SOUTHWARD ALONG LAKE MICHIGAN SHORE
WITH SHIFT TO NORTHEAST WINDS CURRENTLY ACROSS LAKE COUNTY IL.
EXPECT WIND SHIFT INTO ORD/MDW NEXT 60-90 MINUTES WITH NORTHEAST
WINDS GUSTING 25 KT. IFR CIGS IMMEDIATELY BEHIND THE BOUNDARY
ALONG THE LAKE...BUT MAY LAG THE FRONT BY AN HOUR OR SO FARTHER
INLAND.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH CONFIDENCE IN IMMINENT WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD/RATZER

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM TUESDAY.

&&

$$

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

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







000
FXUS63 KLOT 292212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
512 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST NEXT 60-90 MINUTES OR
  SO. GUSTS ABOVE 20 KT EXPECTED WITH WIND SHIFT.

* MVFR/IFR CIGS OVERSPREADING TERMINALS 1-2 HOURS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

RATZER

//DISCUSSION...UPDATED 22Z...

COLD FRONTAL BOUNDARY SURGING SOUTHWARD ALONG LAKE MICHIGAN SHORE
WITH SHIFT TO NORTHEAST WINDS CURRENTLY ACROSS LAKE COUNTY IL.
EXPECT WIND SHIFT INTO ORD/MDW NEXT 60-90 MINUTES WITH NORTHEAST
WINDS GUSTING 25 KT. IFR CIGS IMMEDIATELY BEHIND THE BOUNDARY
ALONG THE LAKE...BUT MAY LAG THE FRONT BY AN HOUR OR SO FARTHER
INLAND.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH CONFIDENCE IN IMMINENT WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD/RATZER

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM TUESDAY.

&&

$$

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

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







000
FXUS63 KLOT 292212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
512 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST NEXT 60-90 MINUTES OR
  SO. GUSTS ABOVE 20 KT EXPECTED WITH WIND SHIFT.

* MVFR/IFR CIGS OVERSPREADING TERMINALS 1-2 HOURS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

RATZER

//DISCUSSION...UPDATED 22Z...

COLD FRONTAL BOUNDARY SURGING SOUTHWARD ALONG LAKE MICHIGAN SHORE
WITH SHIFT TO NORTHEAST WINDS CURRENTLY ACROSS LAKE COUNTY IL.
EXPECT WIND SHIFT INTO ORD/MDW NEXT 60-90 MINUTES WITH NORTHEAST
WINDS GUSTING 25 KT. IFR CIGS IMMEDIATELY BEHIND THE BOUNDARY
ALONG THE LAKE...BUT MAY LAG THE FRONT BY AN HOUR OR SO FARTHER
INLAND.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH CONFIDENCE IN IMMINENT WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD/RATZER

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM TUESDAY.

&&

$$

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

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







000
FXUS63 KLOT 292212
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
512 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST NEXT 60-90 MINUTES OR
  SO. GUSTS ABOVE 20 KT EXPECTED WITH WIND SHIFT.

* MVFR/IFR CIGS OVERSPREADING TERMINALS 1-2 HOURS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

RATZER

//DISCUSSION...UPDATED 22Z...

COLD FRONTAL BOUNDARY SURGING SOUTHWARD ALONG LAKE MICHIGAN SHORE
WITH SHIFT TO NORTHEAST WINDS CURRENTLY ACROSS LAKE COUNTY IL.
EXPECT WIND SHIFT INTO ORD/MDW NEXT 60-90 MINUTES WITH NORTHEAST
WINDS GUSTING 25 KT. IFR CIGS IMMEDIATELY BEHIND THE BOUNDARY
ALONG THE LAKE...BUT MAY LAG THE FRONT BY AN HOUR OR SO FARTHER
INLAND.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH CONFIDENCE IN IMMINENT WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD/RATZER

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 7 PM TUESDAY.

&&

$$

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

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







000
FXUS63 KILX 292021
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
321 PM CDT Mon Sep 29 2014

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1255 PM CDT MON SEP 29 2014

Few to scattered cumulus clouds of 5-7k ft to occur this afternoon
with broken ceilings mainly west and nw of PIA and SPI. Winds to
remain light around 5 kts or less into this evening compliments of
weak high pressure of 1018 mb over IL/MO. A cold front over
southeast WI and northwest IA will push south into central IL
during overnight, and into southern IL during Tue. Broken to
overcast stratus clouds behind the front to move to I-74 from
08-10Z and near SPI and DEC around 12Z. Have ceilings from
700-1500 feet and lowest at PIA and BMI with MVFR vsbys 4-5 miles
possible later tonight into Tue morning. Ceilings to lift to MVFR
after 15Z Tue. Models have trended further southward with stratus
clouds but vary on the cloud bases with NAM model being the lowest
below 1k ft. Winds to switch NE behind the front during overnight
around 5-9 kts.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...07






000
FXUS63 KILX 292021
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
321 PM CDT Mon Sep 29 2014

.SHORT TERM...(Tonight)
ISSUED AT 321 PM CDT MON SEP 29 2014

Weak high pressure will continue fair weather into this evening as
few to scattered cumulus clouds with 5-7k ft bases away from the IN
dissipate around sunset. Patchy shallow ground fog will develop
again near rivers and streams in southeast IL during overnight.
A cold front over southeast WI and central IA will push south into
central IL overnight, reaching I-70 by sunrise Tue, and weaken over
southeast IL on Tuesday. Stratus clouds behind/north of the front
will move south into central IL during overnight and especially
affect areas from I-74 north while southeast IL likely stays clear
most of tonight. Light winds into this evening will become northeast
at 5 to 10 mph during overnight over central IL. Lows tonight will
mostly be in the mid 50s with lower 50s north of Peoria.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 321 PM CDT MON SEP 29 2014

A dry front, located just north of the state is forecast to slowly
drop into the area tonight through tomorrow. NAM-WRF model has been
consistent with forecasting an increase in low clouds across the
northern half of the state tonight and tomorrow. It looks like it
could get to I-74 by morning and could progress further south
tomorrow. How far south it gets will depend on how much of the
southern edge of the cloud deck gets eroded away by the strong sun
during the day tomorrow. So, current thinking is it sill get past
I-74 and could get to I-72 in the eastern part of the CWA. During
the day tomorrow, the sunshine should dissipate a lot of the clouds,
like what is occurring in parts of SD/MN/and IA today. Then mostly
clear and dry conditions are expected tomorrow night through Wed.

A weather system in the western US will the lift northeast into the
northern plains and will have a trailing cold front that will extend
down into the southern plains. Showers and thunderstorms are
expected to develop along and ahead of this front Wed well west of
the CWA. However, these storms will advect eastward into the state
beginning Wed night. A second low pressure area will develop along
the front and will move northeast into the Midwest and bring the
cold front through the area Thur and Thur night. Additional
thunderstorms will develop along the front Thursday and move across
the area during the day and through Thur night. Conditions do not
look right for any of the storms to produce severe weather, but this
could change in the next couple of days. However, lightning and
brief heavy rainfall will be likely with any storms that move
through the area late Wed night and Thursday. Once the front and pcpn
pass, there could be some lingering showers behind the front, so
will be keeping some chance pops in the east for Friday.

Beyond Friday, conditions will improve as a drier and cooler air
mass pushes into the area for the weekend. There is one small, weak
wave that could bring some light showers to the northeastern parts
of the area, along and north of I-74, but its too far away to have
much confidence, so will just have slight chance pops for Sunday,
which will not be mentioned in the worded forecast.

Temps will remain above normal tomorrow, when the sunshine is able
to break through the clouds, and Wed as well. Then clouds and rain
for Thur will keep temps milder and around normal. Once the front
moves through at the end of the week, temps will become much cooler
and actually be below normal for the beginning of Oct.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1255 PM CDT MON SEP 29 2014

Few to scattered cumulus clouds of 5-7k ft to occur this afternoon
with broken ceilings mainly west and nw of PIA and SPI. Winds to
remain light around 5 kts or less into this evening compliments of
weak high pressure of 1018 mb over IL/MO. A cold front over
southeast WI and northwest IA will push south into central IL
during overnight, and into southern IL during Tue. Broken to
overcast stratus clouds behind the front to move to I-74 from
08-10Z and near SPI and DEC around 12Z. Have ceilings from
700-1500 feet and lowest at PIA and BMI with MVFR vsbys 4-5 miles
possible later tonight into Tue morning. Ceilings to lift to MVFR
after 15Z Tue. Models have trended further southward with stratus
clouds but vary on the cloud bases with NAM model being the lowest
below 1k ft. Winds to switch NE behind the front during overnight
around 5-9 kts.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...07







000
FXUS63 KLOT 292008
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
308 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST LATE THIS AFTERNOON.
* MVFR/IFR CIGS OVERSPREADING TERMINALS BEHIND THE FRONT...WITH A
  WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

//DISCUSSION...UPDATED 20Z...
BOUNDARY HAS ACCELERATED SOUTH SO HAVE BUMPED UP TIMING A COUPLE
TIMES ALREADY EARLY THIS AFTERNOON. ALSO INCREASED WINDS WITH
UPSTREAM OBS SHOWING A BRIEF WINDOW OF 25-30KT WIND GUSTS
IMMEDIATELY BEHIND THE FRONT. IFR SEEMS MORE CERTAIN SO CHANGED
THE SCT007 TO BKN007.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
305 PM CDT

A SHARP COLD FRONT IS MARCHING DOWN THE LAKE THIS AFTERNOON WITH A
WIND SHIFT TO NORTH- NORTHEASTERLY BEHIND THE FRONT. THE FRONT HAS
ALREADY PASSED THROUGH MILWAUKEE AS OF 300 PM CDT. OBSERVATIONS BEHIND
THE FRONT HAVE HELD AT 30 KT OR LESS...SO FEEL CONFIDENT THAT
WINDS WILL GENERALLY REMAIN SUB- GALE THROUGH THIS COLD FRONT
PASSAGE AS THE PRESSURE GRADIENT WILL WEAKEN SOMEWHAT AS THE FRONT
PUSHES SOUTH. THERE COULD BE A FEW GUSTS ABOVE 30 KT WITH THE
FRONTAL PASSAGE. EXPECT WAVES TO BUILD THROUGH TUESDAY AS WE
REMAIN UNDER NORTH FLOW THROUGH THE DAY...WITH THE HIGHEST WAVES
ON SOUTHERN PORTIONS OF THE LAKE.

HIGH PRESSURE OVER SOUTHERN ONTARIO WILL WEAKEN AND SLOWLY SHIFT
EAST WHILE THE RIDGE AXIS ASSOCIATED WITH IT WILL SHIFT OVER THE
LAKE TOMORROW AFTERNOON...THEN MOVE EAST OF THE LAKE ON WEDNESDAY.
AS THIS OCCURS ADDITIONAL LOWS IN THE PLAINS WILL LEAD TO A
TIGHTENING PRESSURE GRADIENT LATER WEDNESDAY INTO THURSDAY. AT THIS
POINT THE STRONGER LOW HEADS NORTH THROUGH MANITOBA WHILE ANOTHER
LOW MOVES OVER THE LAKE ON THURSDAY NIGHT. GUIDANCE STILL REMAINS
MIXED AS TO WHETHER THIS LOW WILL BE IN A DEEPENING PHASE AS IT
TRANSITS THE LAKE OR IF IT WILL INTENSIFY MORE SO NORTH AND EAST OF
LAKE MICHIGAN.

A STRONG COLD FRONT WILL THEN MOVE THROUGH LATER THURSDAY NIGHT INTO
FRIDAY BRINGING GUSTY NORTHWESTERLY WINDS. IF THE LOW IS
STRONGER...THERE COULD BE GALES IN THE BETTER MIXED ATMOSPHERE
BEHIND THE LOW FRIDAY. KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 7
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 291956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST LATE THIS AFTERNOON.
* MVFR/IFR CIGS OVERSPREADING TERMINALS BEHIND THE FRONT...WITH A
  WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

//DISCUSSION...UPDATED 20Z...
BOUNDARY HAS ACCELERATED SOUTH SO HAVE BUMPED UP TIMING A COUPLE
TIMES ALREADY EARLY THIS AFTERNOON. ALSO INCREASED WINDS WITH
UPSTREAM OBS SHOWING A BRIEF WINDOW OF 25-30KT WIND GUSTS
IMMEDIATELY BEHIND THE FRONT. IFR SEEMS MORE CERTAIN SO CHANGED
THE SCT007 TO BKN007.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 7
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 291956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST LATE THIS AFTERNOON.
* MVFR/IFR CIGS OVERSPREADING TERMINALS BEHIND THE FRONT...WITH A
  WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

//DISCUSSION...UPDATED 20Z...
BOUNDARY HAS ACCELERATED SOUTH SO HAVE BUMPED UP TIMING A COUPLE
TIMES ALREADY EARLY THIS AFTERNOON. ALSO INCREASED WINDS WITH
UPSTREAM OBS SHOWING A BRIEF WINDOW OF 25-30KT WIND GUSTS
IMMEDIATELY BEHIND THE FRONT. IFR SEEMS MORE CERTAIN SO CHANGED
THE SCT007 TO BKN007.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 7
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 291956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST LATE THIS AFTERNOON.
* MVFR/IFR CIGS OVERSPREADING TERMINALS BEHIND THE FRONT...WITH A
  WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

//DISCUSSION...UPDATED 20Z...
BOUNDARY HAS ACCELERATED SOUTH SO HAVE BUMPED UP TIMING A COUPLE
TIMES ALREADY EARLY THIS AFTERNOON. ALSO INCREASED WINDS WITH
UPSTREAM OBS SHOWING A BRIEF WINDOW OF 25-30KT WIND GUSTS
IMMEDIATELY BEHIND THE FRONT. IFR SEEMS MORE CERTAIN SO CHANGED
THE SCT007 TO BKN007.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 7
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 291956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
256 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST LATE THIS AFTERNOON.
* MVFR/IFR CIGS OVERSPREADING TERMINALS BEHIND THE FRONT...WITH A
  WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

//DISCUSSION...UPDATED 20Z...
BOUNDARY HAS ACCELERATED SOUTH SO HAVE BUMPED UP TIMING A COUPLE
TIMES ALREADY EARLY THIS AFTERNOON. ALSO INCREASED WINDS WITH
UPSTREAM OBS SHOWING A BRIEF WINDOW OF 25-30KT WIND GUSTS
IMMEDIATELY BEHIND THE FRONT. IFR SEEMS MORE CERTAIN SO CHANGED
THE SCT007 TO BKN007.

PREVIOUS DISCUSSION 18Z...

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT.
* HIGH CONFIDENCE IN MVFR/IFR CIGS...LOW-MEDIUM CONFIDENCE IN A
  WINDOW OF LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 7
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 291930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST EARLY THIS EVENING.
* MVFR AND POSSIBLY IFR CIGS OVERSPREADING TERMINALS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

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

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT TO WITHIN AN HOUR.
* HIGH CONFIDENCE IN MVFR CIGS...LOW-MEDIUM CONFIDENCE IN A WINDOW
  OF IFR CIGS AND LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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







000
FXUS63 KLOT 291930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST EARLY THIS EVENING.
* MVFR AND POSSIBLY IFR CIGS OVERSPREADING TERMINALS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

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

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT TO WITHIN AN HOUR.
* HIGH CONFIDENCE IN MVFR CIGS...LOW-MEDIUM CONFIDENCE IN A WINDOW
  OF IFR CIGS AND LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
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000
FXUS63 KLOT 291930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST EARLY THIS EVENING.
* MVFR AND POSSIBLY IFR CIGS OVERSPREADING TERMINALS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

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

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT TO WITHIN AN HOUR.
* HIGH CONFIDENCE IN MVFR CIGS...LOW-MEDIUM CONFIDENCE IN A WINDOW
  OF IFR CIGS AND LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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







000
FXUS63 KLOT 291930
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 PM CDT MON SEP 29 2014

.DISCUSSION...
230 PM CDT

OUR STRETCH OF ONE WEEK OF ABOVE NORMAL TEMPERATURES IS ABOUT TO GET
A TOUCH OF EARLY AUTUMN REALITY...AND A MUCH RUDER PUNCH LATE IN THE
WEEK. FORECAST CONCERNS WERE ON THE TEMPERATURE DROP LATE THIS
AFTERNOON INTO THE EVE AND SUBSEQUENT LIGHT RAIN/DRIZZLE
CHANCES...THEN CLOUD COVER TUESDAY WHICH COULD GREATLY HINDER
WARMING...AND FINALLY THE STORM SYSTEM WEDNESDAY NIGHT THROUGH
FRIDAY BRINGING WIDESPREAD SHOWER AND STORM CHANCES.

LATE THIS AFTERNOON INTO TONIGHT...
OBSERVATIONS...SATELLITE...AND MKE RADAR ALL HAVE A GOOD HANDLE ON
THE SHARP COLD FRONT DROPPING SOUTHWARD ACROSS THE GREAT LAKES
REGION THIS AFTERNOON. OBSERVATIONS IN EAST CENTRAL WI HAVE DROPPED
BY AS MUCH AS 23 DEGREES IN AN HOUR EARLY THIS AFTERNOON WITH THE
SYNOPTIC AND LAKE-ENHANCED COOL SURGE. WHILE PRESSURE RISES WILL
EASE BEHIND THE FRONT DUE TO THE PARENT LOW WELL OFF TO THE
NORTHEAST...THIS FRONT SHOULD STILL COME BARRELING INTO NORTHEAST IL
BY 530-630 PM WITH SOME GUSTS TO NEAR 30 MPH AND A 20-25 DEGREE
TEMPERATURE DROP IN TWO-THREE HOURS. THIS FRONT WILL THEN CONTINUE
TO MOVE SOUTHWARD THROUGH THE FORECAST AREA EASING SOME IN
BAROCLINICITY.

ANAFRONTAL FORCING IS SUPPORTING SCATTERED SHOWERS ACROSS CENTRAL
WI. THIS MID-LEVEL FRONTOGENESIS AND OMEGA WILL DIMINISH SOME AS
THIS FRONT SLIDES INTO OUR AREA AND SOUNDINGS SUPPORT MORE OF LIGHT
RAIN OR DRIZZLE IF PRECIPITATION CAN OCCUR. THIS SEEMS MOST FAVORED
IN THE MID-LATE EVE OVER NORTHERN IL AND POSSIBLY REACHING INTO FAR
NORTHWEST INDIANA. CLOUDS SHOULD BECOME WIDESPREAD AS VISIBLE
SATELLITE SHOWS UPSTREAM AND THE SLOWING BOUNDARY TRAPS THE MOISTURE
BENEATH A STRENGTHENING INVERSION.

TUESDAY...
SURFACE RIDGING WILL POKE INTO THE WESTERN GREAT LAKES DURING THIS
TIME...BUT THROUGH EARLY AFTERNOON NORTHEAST LOW-LEVEL FLOW SHOULD
CONTINUE OVER THE AREA. CONCEPTUALLY IN A STRONG POST-FRONTAL AIR
MASS WITH A STRONG INVERSION IN PLACE...THINK STRATUS WILL CONTINUE
THROUGH AT LEAST EARLY AFTERNOON IF NOT THE ENTIRE DAY ESPECIALLY
FOR LAKE ADJACENT AREAS. HAVE EXTENDED THE DURATION OF FORECAST
CLOUD COVER CONSIDERABLY AND HAVE CORRELATED TEMPERATURES
DOWNWARD...WITH THE MERCURY ONLY RISING A HANDFUL OF DEGREES IN
NEAR-LAKE AREAS INCLUDING CHICAGO. FURTHER SOUTH AND WEST...MID 60S
MAY BE REALIZED. INCREASING SUBSIDENCE IN THE AFTERNOON SHOULD HELP
TO OPEN SOME HOLES IN THE CLOUDS.

LATTER HALF OF THE WEEK AND NEXT WEEKEND...
NORTHERN HEMISPHERIC WATER VAPOR SHOWS AN ACTIVE PATTERN OVER THE
WESTERN U.S. INTO THE NORTHERN PACIFIC AND THIS WILL EVOLVE OVER OUR
REGION DURING THIS PERIOD. PHASING OF THE CURRENT WESTERN U.S. UPPER
LOW AND A TROUGH MOVING ONSHORE OF WESTERN CANADA IS LIKELY ONE
CULPRIT TO FAIRLY SUBSTANTIAL MODEL DIFFERENCES OVER OUR REGION.
HAVE LEANED TOWARD THE MORE CONSISTENT GFS OUTPUT FOR THIS TIME WITH
CONFIDENCE BEING ESPECIALLY LOW SATURDAY-MONDAY.

SOUTHERLY FLOW WILL DEVELOP BACK INTO THE AREA WEDNESDAY AND
THURSDAY IN RESPONSE TO MULTIPLE ROUNDS OF CYCLOGENESIS. THIS LOOKS
TO YIELD HIGHS IN THE 70S THOUGH WITH HIGHS ON THURSDAY DEPENDENT ON
RAIN COVERAGE. THE RAIN CHANCES LOOK TO INCREASE LATER WEDNESDAY
NIGHT AND THROUGH THURSDAY AS DEEP LAYER MOISTURE CONVERGENCE
INCREASES WITHIN BETTER SUPPORT AND FOCUS FOR ASCENT. WHILE
SPECIFICS ON EXACT PRECIP EVOLUTION REMAIN UNCERTAIN ALONG WITH
WHICH PERIOD WITHIN 24-36H WINDOW WILL HAVE THE MOST WIDESPREAD
COVERAGE...CONTINUE THE BROAD LIKELY POPS MENTION. WOULD EXPECT TO
SEE SOME THUNDER WITH SUCH A DEEPENING SYSTEM ON THURSDAY AFTERNOON
INTO THE NIGHT AND A RIBBON OF INSTABILITY AHEAD OF THE INCOMING
COLD FRONT. WHILE THERE IS AT LEAST AN ISOLATED SEVERE WEATHER
POTENTIAL IN THE OVERALL REGION...IT WOULD SEEM TO BE BETTER OVER
THE MID-MISSISSIPPI VALLEY TO OUR SOUTH WITH MOISTURE
TRANSPORT/DEEPER INSTABILITY POTENTIALLY INHIBITED TO REACH THIS FAR
NORTH FROM CONVECTION OVER THE AREA.

MODELS SHOW WIDESPREAD DIFFERENCES BEHIND THIS SYSTEM IN AN
UNSETTLED NORTHWEST FLOW. THE GFS IS NOT AS PRONOUNCED WITH THE COLD
AIR INCOMING ON FRIDAY/FRIDAY NIGHT AND LEANING THAT ROUTE STILL
PROVIDES LOWS IN THE UPPER 30S-MID 40S ACROSS MOST OF THE AREA
FRIDAY/SATURDAY/SUNDAY NIGHTS...ALTHOUGH THERE WILL CERTAINLY BE
SOME DEPENDENCY ON CLOUD COVER. FRIDAY LOOKS WINDY THOUGH MAINLY DRY
WITH SUBSIDENCE BEHIND THE AFOREMENTIONED SYSTEM. WEEKEND CHANCES OF
RAIN ARE TOUGH TO SAY AND DEPENDENT ON WHEN A CLEARER PICTURE IS
PAINTED WITH NORTHWEST FLOW DISTURBANCES.

MTF

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST EARLY THIS EVENING.
* MVFR AND POSSIBLY IFR CIGS OVERSPREADING TERMINALS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

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

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD

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

* HIGH CONFIDENCE IN TIMING WIND SHIFT TO WITHIN AN HOUR.
* HIGH CONFIDENCE IN MVFR CIGS...LOW-MEDIUM CONFIDENCE IN A WINDOW
  OF IFR CIGS AND LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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







000
FXUS63 KILX 291756
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1256 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 1045 AM CDT MON SEP 29 2014

Forecast looks on track today and just a few minor tweaks done
today. Late morning temperatures are running a bit higher than
this time yesterday and may nudge highs up a bit in spots with
highs generally in the mid 80s with a few areas reaching the upper
80s with ample sunshine. The RAP/NAM curule shows few cumulus
clouds this afternoon at 5-7k ft especially from I-74 north and
western CWA while limited cumulus clouds near the Wabash river
today. Sunny skies this morning across much of IL with mostly
sunny skies expected this afternoon. Weak surface high pressure of
1018 mb over IL/MO to keep winds light again today.

&&

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1255 PM CDT MON SEP 29 2014

Few to scattered cumulus clouds of 5-7k ft to occur this afternoon
with broken ceilings mainly west and nw of PIA and SPI. Winds to
remain light around 5 kts or less into this evening compliments of
weak high pressure of 1018 mb over IL/MO. A cold front over
southeast WI and northwest IA will push south into central IL
during overnight, and into southern IL during Tue. Broken to
overcast stratus clouds behind the front to move to I-74 from
08-10Z and near SPI and DEC around 12Z. Have ceilings from
700-1500 feet and lowest at PIA and BMI with MVFR vsbys 4-5 miles
possible later tonight into Tue morning. Ceilings to lift to MVFR
after 15Z Tue. Models have trended further southward with stratus
clouds but vary on the cloud bases with NAM model being the lowest
below 1k ft. Winds to switch NE behind the front during overnight
around 5-9 kts.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07







000
FXUS63 KILX 291756
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1256 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 1045 AM CDT MON SEP 29 2014

Forecast looks on track today and just a few minor tweaks done
today. Late morning temperatures are running a bit higher than
this time yesterday and may nudge highs up a bit in spots with
highs generally in the mid 80s with a few areas reaching the upper
80s with ample sunshine. The RAP/NAM curule shows few cumulus
clouds this afternoon at 5-7k ft especially from I-74 north and
western CWA while limited cumulus clouds near the Wabash river
today. Sunny skies this morning across much of IL with mostly
sunny skies expected this afternoon. Weak surface high pressure of
1018 mb over IL/MO to keep winds light again today.

&&

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1255 PM CDT MON SEP 29 2014

Few to scattered cumulus clouds of 5-7k ft to occur this afternoon
with broken ceilings mainly west and nw of PIA and SPI. Winds to
remain light around 5 kts or less into this evening compliments of
weak high pressure of 1018 mb over IL/MO. A cold front over
southeast WI and northwest IA will push south into central IL
during overnight, and into southern IL during Tue. Broken to
overcast stratus clouds behind the front to move to I-74 from
08-10Z and near SPI and DEC around 12Z. Have ceilings from
700-1500 feet and lowest at PIA and BMI with MVFR vsbys 4-5 miles
possible later tonight into Tue morning. Ceilings to lift to MVFR
after 15Z Tue. Models have trended further southward with stratus
clouds but vary on the cloud bases with NAM model being the lowest
below 1k ft. Winds to switch NE behind the front during overnight
around 5-9 kts.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07







000
FXUS63 KILX 291756
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1256 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 1045 AM CDT MON SEP 29 2014

Forecast looks on track today and just a few minor tweaks done
today. Late morning temperatures are running a bit higher than
this time yesterday and may nudge highs up a bit in spots with
highs generally in the mid 80s with a few areas reaching the upper
80s with ample sunshine. The RAP/NAM curule shows few cumulus
clouds this afternoon at 5-7k ft especially from I-74 north and
western CWA while limited cumulus clouds near the Wabash river
today. Sunny skies this morning across much of IL with mostly
sunny skies expected this afternoon. Weak surface high pressure of
1018 mb over IL/MO to keep winds light again today.

&&

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1255 PM CDT MON SEP 29 2014

Few to scattered cumulus clouds of 5-7k ft to occur this afternoon
with broken ceilings mainly west and nw of PIA and SPI. Winds to
remain light around 5 kts or less into this evening compliments of
weak high pressure of 1018 mb over IL/MO. A cold front over
southeast WI and northwest IA will push south into central IL
during overnight, and into southern IL during Tue. Broken to
overcast stratus clouds behind the front to move to I-74 from
08-10Z and near SPI and DEC around 12Z. Have ceilings from
700-1500 feet and lowest at PIA and BMI with MVFR vsbys 4-5 miles
possible later tonight into Tue morning. Ceilings to lift to MVFR
after 15Z Tue. Models have trended further southward with stratus
clouds but vary on the cloud bases with NAM model being the lowest
below 1k ft. Winds to switch NE behind the front during overnight
around 5-9 kts.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07







000
FXUS63 KILX 291756
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1256 PM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 1045 AM CDT MON SEP 29 2014

Forecast looks on track today and just a few minor tweaks done
today. Late morning temperatures are running a bit higher than
this time yesterday and may nudge highs up a bit in spots with
highs generally in the mid 80s with a few areas reaching the upper
80s with ample sunshine. The RAP/NAM curule shows few cumulus
clouds this afternoon at 5-7k ft especially from I-74 north and
western CWA while limited cumulus clouds near the Wabash river
today. Sunny skies this morning across much of IL with mostly
sunny skies expected this afternoon. Weak surface high pressure of
1018 mb over IL/MO to keep winds light again today.

&&

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1255 PM CDT MON SEP 29 2014

Few to scattered cumulus clouds of 5-7k ft to occur this afternoon
with broken ceilings mainly west and nw of PIA and SPI. Winds to
remain light around 5 kts or less into this evening compliments of
weak high pressure of 1018 mb over IL/MO. A cold front over
southeast WI and northwest IA will push south into central IL
during overnight, and into southern IL during Tue. Broken to
overcast stratus clouds behind the front to move to I-74 from
08-10Z and near SPI and DEC around 12Z. Have ceilings from
700-1500 feet and lowest at PIA and BMI with MVFR vsbys 4-5 miles
possible later tonight into Tue morning. Ceilings to lift to MVFR
after 15Z Tue. Models have trended further southward with stratus
clouds but vary on the cloud bases with NAM model being the lowest
below 1k ft. Winds to switch NE behind the front during overnight
around 5-9 kts.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07







000
FXUS63 KLOT 291737
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1237 PM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST EARLY THIS EVENING.
* MVFR AND POSSIBLY IFR CIGS OVERSPREADING TERMINALS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

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

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD


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

* HIGH CONFIDENCE IN TIMING WIND SHIFT TO WITHIN AN HOUR.
* HIGH CONFIDENCE IN MVFR CIGS...LOW-MEDIUM CONFIDENCE IN A WINDOW
  OF IFR CIGS AND LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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000
FXUS63 KLOT 291737
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1237 PM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* COLD FRONT SHIFTING WINDS TO THE NORTHEAST EARLY THIS EVENING.
* MVFR AND POSSIBLY IFR CIGS OVERSPREADING TERMINALS BEHIND THE
  FRONT...WITH A WINDOW OF LIGHT RAIN AND DRIZZLE EXPECTED.

BMD

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

A COLD FRONT CONTINUES TO SLIP SOUTH ACROSS WISCONSIN AND LAKE
MICHIGAN THIS AFTERNOON BUT IN THE MEANTIME...VFR CONDITIONS AND
LIGHT WESTERLY FLOW WILL PREVAIL AT THE TERMINALS. THE FRONT WILL
ARRIVE BY EARLY THIS EVENING TURNING WINDS SHARPLY TO THE NORTHEAST
WITH GUSTS UP TO AROUND 20 KT AT TIMES BEHIND THE FRONT. LOWER CIGS
ARE ALSO EXPECTED TO OVERSPREAD THE TERMINALS BEHIND THE
FRONT...WITH HIGH CONFIDENCE IN LOWER END MVFR CIGS AND A DECENT
SHOT AT IFR CIGS. MOISTURE BEHIND THE FRONT IS SOMEWHAT SHALLOW BUT
THERE IS MODEST POST FRONTAL FORCING THAT COULD HELP SQUEEZE OUT
SOME LIGHT RAIN OR DRIZZLE THIS EVENING INTO THE OVERNIGHT HOURS. BY
THE PREDAWN HOURS TUESDAY FORCING DISSIPATES WHILE LOWER MOISTURE
LINGERS. THERE IS EXPECTED TO BE A SLIGHT DIURNAL LIFT OF THE CLOUD
BASES DURING THE DAY TUESDAY...HOWEVER MVFR CIGS ARE EXPECTED TO
LINGER THROUGH THE DAY.

BMD


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

* HIGH CONFIDENCE IN TIMING WIND SHIFT TO WITHIN AN HOUR.
* HIGH CONFIDENCE IN MVFR CIGS...LOW-MEDIUM CONFIDENCE IN A WINDOW
  OF IFR CIGS AND LIGHT RAIN/DRIZZLE.

BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 291610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT WEST WINDS THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB/BMD

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB

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

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THROUGH EARLY AFTERNOON. MEDIUM-HIGH
  CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
  TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB/BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 291610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT WEST WINDS THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB/BMD

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB

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

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THROUGH EARLY AFTERNOON. MEDIUM-HIGH
  CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
  TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB/BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KILX 291545
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1045 AM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 1045 AM CDT MON SEP 29 2014

Temps are running a bit higher than this time yesterday and may
nudge highs up a bit in spots with highs generally in the mid 80s
with a few areas reaching th upper 80s with ample sunshine. The
RAP/NAM curule shows few cumulus clouds this afternoon at 5-7k ft
mainly from I-74 ne while limited cumulus clouds near the Wabash
river today. Sunny skies this morning across much of IL.

&&

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 635 AM CDT MON SEP 29 2014

There is some potential for some patchy MVFR vsbys in fog from
thru 13z for PIA and SPI. Otherwise, VFR conditions are expected
today and this evening. Mid-level moisture evident on forecast
soundings indicate some scattered high based cumulus are expected
after 16z, which should dissipate by 00z. This evening a cold
front will progress south into northern Illinois, with low clouds
trailing close behind. The leading edge of the clouds appear to
start MVFR, but could quickly drop to IFR of 600-800 feet. Current
thinking is that the band of lower clouds will affect our northern
TAF sites (KPIA, KBMI) first between 08z and 09z, and possibly as
far east as CMI toward 11z. Surface winds will become light north
to northwest today under weak high pressure. Behind the front
later tonight, winds will shift to northeast for PIA, BMI and CMI.


&&

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

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...Shimon






000
FXUS63 KILX 291545
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1045 AM CDT Mon Sep 29 2014

.UPDATE...
ISSUED AT 1045 AM CDT MON SEP 29 2014

Temps are running a bit higher than this time yesterday and may
nudge highs up a bit in spots with highs generally in the mid 80s
with a few areas reaching th upper 80s with ample sunshine. The
RAP/NAM curule shows few cumulus clouds this afternoon at 5-7k ft
mainly from I-74 ne while limited cumulus clouds near the Wabash
river today. Sunny skies this morning across much of IL.

&&

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 635 AM CDT MON SEP 29 2014

There is some potential for some patchy MVFR vsbys in fog from
thru 13z for PIA and SPI. Otherwise, VFR conditions are expected
today and this evening. Mid-level moisture evident on forecast
soundings indicate some scattered high based cumulus are expected
after 16z, which should dissipate by 00z. This evening a cold
front will progress south into northern Illinois, with low clouds
trailing close behind. The leading edge of the clouds appear to
start MVFR, but could quickly drop to IFR of 600-800 feet. Current
thinking is that the band of lower clouds will affect our northern
TAF sites (KPIA, KBMI) first between 08z and 09z, and possibly as
far east as CMI toward 11z. Surface winds will become light north
to northwest today under weak high pressure. Behind the front
later tonight, winds will shift to northeast for PIA, BMI and CMI.


&&

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

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...Shimon







000
FXUS63 KLOT 291410
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
910 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT WEST-NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB/BMD

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB

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

* HIGH CONFIDENCE IN VSBY TRENDS.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON. MEDIUM-
  HIGH CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS
  EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
  TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB/BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 291410
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
910 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT WEST-NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB/BMD

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB

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

* HIGH CONFIDENCE IN VSBY TRENDS.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON. MEDIUM-
  HIGH CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS
  EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
  TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB/BMD

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KLOT 291138
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB


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

* HIGH CONFIDENCE IN VSBY TRENDS THROUGH THE MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON. MEDIUM-
  HIGH CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS
  EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
 TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 291138
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB


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

* HIGH CONFIDENCE IN VSBY TRENDS THROUGH THE MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON. MEDIUM-
  HIGH CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS
  EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
 TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 291138
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB


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

* HIGH CONFIDENCE IN VSBY TRENDS THROUGH THE MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON. MEDIUM-
  HIGH CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS
  EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
 TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 291138
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
638 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND 15-20 KT GUSTS DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING...IMPROVING
  TUESDAY AFTERNOON.

MDB

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

CALM TO LIGHT AND VARIABLE WINDS CONTINUE THIS MORNING. QUITE A
BIT OF MVFR VSBY ACROSS THE AREA WITH SHALLOW FOG PERIODICALLY
LOWERING VSBY TO IFR IN SPOTS. VSBY WILL STEADILY RISE STARTING
12-13Z WITH VFR THEN EXPECTED THROUGH THE AFTERNOON. WINDS WILL BE
LIGHT AND VARIABLE BUT FAVOR A WEST TO SOUTHWEST DIRECTION TURNING
NORTHWEST IN THE AFTERNOON. LAKE INFLUENCE WILL LIKELY BRING WINDS
TO LIGHT NE AT GYY.

BIGGEST CONCERN IS A COLD FRONTAL PASSAGE VERY LATE THIS AFTERNOON
AND EARLY THIS EVENING. THE FRONT WILL QUICKLY MOVE SOUTHWARD DOWN
THE LAKE TURNING WINDS NORTH TO NORTHEAST AS IT PASSES. HAVE A
GOOD DEGREE OF CONFIDENCE IN THE TIMING OF THE FRONTAL WIND SHIFT
BUT SOME TWEAKING MAY STILL BE NEEDED. SPEEDS WILL INCREASE
BEHIND THE FRONT WITH GUSTS NEAR 20 KT AND CANNOT RULE OUT
SLIGHTLY HIGHER GUSTS FOR A SHORT TIME...ESPECIALLY AT GYY GIVEN
THE LONG FETCH DOWN THE LAKE AND THEIR PROXIMITY TO THE SHORELINE.
STRATUS LOOKS TO MOVE IN BEHIND THE FRONT AS WELL AND WILL
CONTINUE WITH 010 CIGS BUT IFR 007-009 CIGS ARE POSSIBLE. WINDS
WILL LIKELY EASE THROUGH THE EVENING THOUGH STRATUS LOOKS TO
PERSIST THROUGH THE NIGHT AND LIKELY A GOOD PORTION OF TUESDAY
MORNING. DO EXPECT IT TO RISE/SCATTER INTO TUESDAY AFTERNOON
THOUGH.

MDB


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

* HIGH CONFIDENCE IN VSBY TRENDS THROUGH THE MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON. MEDIUM-
  HIGH CONFIDENCE IN TIMING OF SHIFT TO NORTHEAST WINDS THIS
  EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT. MEDIUM-HIGH CONFIDENCE IN IMPROVEMENT
 TUESDAY AFTERNOON...LOW CONFIDENCE IN TIMING.

MDB

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

TUESDAY NIGHT...VFR. EAST WINDS.

WEDNESDAY...VFR. SOUTHEAST WINDS.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS TURNING
SOUTHWEST LATE.

FRIDAY...SLIGHT CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...SLIGHT CHANCE SHRA. VFR. WEST WINDS.

SUNDAY...VFR. SOUTHWEST WINDS.

MDB

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KILX 291135
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
635 AM CDT Mon Sep 29 2014

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 635 AM CDT MON SEP 29 2014

There is some potential for some patchy MVFR vsbys in fog from
thru 13z for PIA and SPI. Otherwise, VFR conditions are expected
today and this evening. Mid-level moisture evident on forecast
soundings indicate some scattered high based cumulus are expected
after 16z, which should dissipate by 00z. This evening a cold
front will progress south into northern Illinois, with low clouds
trailing close behind. The leading edge of the clouds appear to
start MVFR, but could quickly drop to IFR of 600-800 feet. Current
thinking is that the band of lower clouds will affect our northern
TAF sites (KPIA, KBMI) first between 08z and 09z, and possibly as
far east as CMI toward 11z. Surface winds will become light north
to northwest today under weak high pressure. Behind the front
later tonight, winds will shift to northeast for PIA, BMI and CMI.

&&

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

$$

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






000
FXUS63 KILX 291135
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
635 AM CDT Mon Sep 29 2014

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
ISSUED AT 635 AM CDT MON SEP 29 2014

There is some potential for some patchy MVFR vsbys in fog from
thru 13z for PIA and SPI. Otherwise, VFR conditions are expected
today and this evening. Mid-level moisture evident on forecast
soundings indicate some scattered high based cumulus are expected
after 16z, which should dissipate by 00z. This evening a cold
front will progress south into northern Illinois, with low clouds
trailing close behind. The leading edge of the clouds appear to
start MVFR, but could quickly drop to IFR of 600-800 feet. Current
thinking is that the band of lower clouds will affect our northern
TAF sites (KPIA, KBMI) first between 08z and 09z, and possibly as
far east as CMI toward 11z. Surface winds will become light north
to northwest today under weak high pressure. Behind the front
later tonight, winds will shift to northeast for PIA, BMI and CMI.

&&

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

$$

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







000
FXUS63 KLOT 290904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB

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

* MEDIUM CONFIDENCE IN VSBY IN FOG THROUGH EARLY MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 290904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB

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

* MEDIUM CONFIDENCE IN VSBY IN FOG THROUGH EARLY MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 290904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB

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

* MEDIUM CONFIDENCE IN VSBY IN FOG THROUGH EARLY MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 290904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG THROUGH EARLY MORNING. MVFR VSBY LIKELY WITH IFR VSBY
  POSSIBLE.

* VARIABLE/CALM WINDS THROUGH THE MORNING...BECOMING LIGHT WEST-
  NORTHWEST THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB

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

* MEDIUM CONFIDENCE IN VSBY IN FOG THROUGH EARLY MORNING.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 290844
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
344 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG LATE TONIGHT THROUGH EARLY MORNING. MVFR VSBY LIKELY
  WITH IFR VSBY POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST-NORTHWEST
  THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB

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

* MEDIUM CONFIDENCE IN VSBY IN FOG LATE TONIGHT/EARLY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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





000
FXUS63 KLOT 290844
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
344 AM CDT MON SEP 29 2014

.DISCUSSION...
344 AM CDT

HIGH PRESSURE SPANNING THE REGION THIS MORNING PROVIDING ANOTHER
RELATIVELY QUIET START TO THE FORECAST PERIOD...AS TEMPS HAVE
FALLEN TO THE LOW TO MID 50S UNDER CLEAR SKIES. PATCHY FOG HAS
ONCE AGAIN DEVELOP OVER THE ENTIRE CWA EARLY THIS MORNING AND
SIMILAR TO YESTERDAY MORNING...SOME AREAS ARE OCCASIONALLY
OBSERVING VIS FALL UNDER A MILE AT TIMES. WIDESPREAD DENSE FOG
WILL ONCE AGAIN NOT BE OBSERVED THIS MORNING BUT WITH VISIBILITY
LIKELY VARYING OVER SHORT DISTANCES AND AT TIMES UNDER ONE
MILE...DID GO AHEAD AND ISSUE AN SPS THROUGH AROUND SUNRISE.
UPSTREAM TROUGH OF LOW PRESSURE AND COLD FRONT CURRENTLY MOVING
INTO FAR NORTHERN LAKE MICHIGAN THIS MORNING AS VORT MAX OBSERVED
DROPPING INTO THE UPPER MIDWEST. THESE FEATURES WILL DROP SOUTH
TOWARDS THE CWA TODAY BUT BEFORE THEY DO...ANOTHER WARM AND
PLEASANT DAY WILL OCCUR. MADE LITTLE CHANGES TO GOING MAX TEMPS
TODAY AND EXPECT A GOOD PORTION OF THE CWA TO OBSERVE LOWER 80S
TODAY UNDER MOSTLY SUNNY CONDITIONS. ALTHOUGH THERE WILL BE SOME
LAKE COOLING TODAY...DONT ANTICIPATE IT TO BE TOO MUCH NOT LET
AREAS NEAR THE LAKE OBSERVE SLIGHTLY WARMER CONDITIONS THAN HAS
BEEN OBSERVED OVER THE LAST COUPLE DAYS. THIS WILL BE DUE TO
WESTERLY WINDS KEEPING THE LAKE BREEZE RIGHT ALONG THE SHORE...AND
HAVE INCREASED TEMPS TO MID TO UPPER 70S IN THESE AREAS.

EXPECT RAPIDLY CHANGING CONDITIONS LATER TODAY WITH THE APPROACH
OF THE FRONT TO THE NORTH...WITH IT APPEARING TO HAVE A FASTER
ARRIVAL TIME. THIS FRONT ALONG WITH CLOUDIER AND COLDER CONDITIONS
SHOULD REACH THE FAR NORTHERN TIER OF COUNTIES BY THE 23-00Z TIME
FRAME....LIKELY SENDING THE WARMER TEMPS INTO THE 50S BY THE
EVENING. PREVIOUS TRENDS OF PRECIP POSSIBLY REACHING THE
NORTH/NORTHEAST PORTION OF THE CWA WITH THE APPROACH OF THIS
FRONT/VORT MAX HAVE CONTINUED...AND HAVE EXPANDED PRECIP MENTION
TO AREAS IN NORTH/NORTHEAST ILLINOIS LATE THIS AFTERNOON INTO THE
EVENING. ONLY HAVE SLIGHT CHANCE WORDING AS AM NOT OVERLY
CONFIDENT WITH OVERALL COVERAGE AND INTENSITY WITH WHATEVER
APPROACHING PRECIP LIKELY OBSERVING A DIMINISHING TREND WITH THE
DEPARTURE OF THE BEST FORCING TO THE EAST. CLOUDY AND COOL
CONDITIONS WILL THEN BE OBSERVED TONIGHT WITH THE ARRIVAL OF THIS
COLDER AIRMASS...AS TEMPS IN THE LOW/MID 40S LIKELY OVER NORTHERN
ILLINOIS AND LOW 50S ELSEWHERE.

WITH LINGERING CLOUD COVER AND THIS COLDER AIRMASS IN PLACE...ALSO
LOWERED TEMPS ON TUESDAY WITH SOME LOCATIONS POSSIBLY NOT MAKING
IT OUT OF THE 50S. TUESDAY WILL BE DRY THOUGH AS VORT MAX WILL BE
WELL EAST OF THE REGION AND A PERIOD OF RIDGING OCCURS OVER THE
MIDWEST AND GREAT LAKES REGION. LONGWAVE TROUGH WILL BE PUSHING
THROUGH WESTERN AND CENTRAL CONUS DURING THIS TIME...WITH A FAIRLY
VIGOROUS VORT MAX LIFTING NORTH THROUGH THE CENTRAL AND NORTHERN
PLAINS INTO TUESDAY NIGHT. BACKING WINDS ALOFT OUT AHEAD OF THIS
SYSTEM WILL HELP TEMPS REBOUND ON WEDNESDAY AS A PERIOD WAA
OCCURS...WITH 70 DEGREE WEATHER TRYING TO RETURN. VORT MAX WILL
QUICKLY LIFT NORTH INTO CANADA WEDNESDAY AS ANOTHER TROUGH DIGS
INTO THE CENTRAL PLAINS. THIS WILL SHIFT THE LONGWAVE TROUGH
TOWARDS THE CWA BY EARLY THURSDAY...AS ATTENDANT SURFACE
TROUGH/LOW MOVE THROUGH THE MID MISSISSIPPI VALLEY. GUIDANCE
VARIES WITH REGARDS TO EVOLUTION OF SURFACE FEATURES DURING THIS
TIME BUT SHORTWAVE ENERGY RIDING OUT AHEAD OF THIS TROUGH AS WELL
AS INCREASING MOISTURE WILL ALLOW FOR PRECIP TO WORK ITS WAY INTO
THE CWA...LIKELY REACHING THE WESTERN CWA EARLY THURSDAY. BEST
CHANCES CWA WIDE WILL BE DURING THE DAY ON THURSDAY...WITH THE
BEST CHANCES FOR THUNDER ALSO OCCURRING DURING THIS TIME.
CONFIDENCE IS LOW WITH REGARDS TO THE EXTENT OF INSTABILITY
PRESENT BUT WITH INCREASING MOISTURE AND BETTER FORCING MOVING
OVERHEAD...ENOUGH INSTABILITY SHOULD BE PRESENT FOR THUNDERSTORM
DEVELOPMENT ACROSS THE CWA.

RODRIGUEZ

&&

.AVIATION...

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

* PATCHY FOG LATE TONIGHT THROUGH EARLY MORNING. MVFR VSBY LIKELY
  WITH IFR VSBY POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST-NORTHWEST
  THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB

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

* MEDIUM CONFIDENCE IN VSBY IN FOG LATE TONIGHT/EARLY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 290758
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 AM CDT MON SEP 29 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

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

* PATCHY FOG LATE TONIGHT THROUGH EARLY MORNING. MVFR VSBY LIKELY
  WITH IFR VSBY POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST-NORTHWEST
  THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB

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

* MEDIUM CONFIDENCE IN VSBY IN FOG LATE TONIGHT/EARLY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
257 AM CDT

A STRONG COLD FRONT WILL MOVE SOUTHWARD DOWN LAKE MICHIGAN TODAY
BRINGING A SHIFT TO NORTH AND NORTHEAST WINDS WITH A SHARP INCREASE
IN SPEEDS. HIGH PRESSURE WHICH HAS BEEN ACROSS THE REGION FOR
SEVERAL DAYS IS WEAKENING AND PUSHING SOUTHWARD ACROSS THE OHIO
VALLEY AND SOUTHEAST U.S. WEAK SURFACE LOW PRESSURE HAS DEVELOPED
AND IS MOVING EASTWARD ACROSS NORTHERN LAKE MICHIGAN EARLY THIS
MORNING DRAGGING THE COLD FRONT WITH IT. STRONG HIGH PRESSURE IS
CENTERED OVER NORTHERN ONTARIO AND WILL MOVE SOUTHWARD BUT WEAKEN AS
IT DOES SO. THE FRONT WILL REACH THE NORTHERN SHORE OF THE LAKE
TOWARD OR SOON AFTER DAYBREAK AND PUSH SOUTHWARD REACHING THE
SOUTHERN TIP EARLY THIS EVENING. SPEEDS WILL INCREASE INTO THE 20-25
KT RANGE WITH GUSTS PUSHING 30 KT BEHIND THE FRONT...ESPECIALLY
ACROSS NORTHERN SECTIONS OF THE LAKE. STRONGER GUSTS HAVE OCCURRED
ACROSS LAKE SUPERIOR EARLY THIS MORNING BUT THE PRESSURE GRADIENT
WILL LIKELY NOT BE QUITE AS STRONG AS IT MOVES ACROSS LAKE MICHIGAN.
CANNOT RULE OUT A SHORT PERIOD OF GUSTS TOPPING 30 KT NORTH THIS
MORNING HOWEVER. EXPECT THE 25-30 KT GUSTS TO SPREAD ACROSS THE
SOUTH END OF THE LAKE THIS AFTERNOON AS WELL AND WILL HOIST A SMALL
CRAFT ADVISORY FOR THE IL/IN NEARSHORE WATERS FROM FIRST THING THIS
EVENING CONTINUING UNTIL LATE TUESDAY AFTERNOON. WINDS WILL STEADILY
DIMINISH TUESDAY AS HIGH PRESSURE RIDGING BUILDS IN BUT WAVES WILL
REMAIN ELEVATED THANKS TO THE LONG FETCH DOWN THE LAKE.

THE RIDGE WILL SHIFT EAST INTO WEDNESDAY TURNING WINDS
SOUTHEASTERLY. LOW PRESSURE WILL TRACK ACROSS THE NORTHERN PLAINS
INTO MANITOBA WEDNESDAY AND WEDNESDAY NIGHT SO THE PRESSURE GRADIENT
WILL BE TIGHTENING SO A BREEZY SOUTH TO SOUTHEAST WIND WILL DEVELOP.
AN UPPER TROUGH WILL BE MOVING EASTWARD ACROSS THE CENTRAL U.S.
SPAWNING ANOTHER SURFACE LOW ACROSS THE SOUTHERN HIGH PLAINS WHICH
WILL THEN TRACK NORTHEASTWARD. GUIDANCE HAS BEEN MORE CONSISTENT
TAKING THE LOW ACROSS THE LAKE LATER THURSDAY INTO FRIDAY BUT IS
HAVING DIFFICULTY LATCHING ONTO THE STRENGTH. THERE WILL LIKELY BE
FURTHER FLUCTUATIONS WITH STRENGTH AND THEREFORE THE INTENSITY OF
WIND SPEEDS. WILL CONTINUE TO MONITOR THE POTENTIAL FOR A PERIOD OF
STRONG WINDS WITH THIS LOW THOUGH LATEST GUIDANCE HAS BACKED OFF
SIGNIFICANTLY ON THE STRENGTH.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...5 PM MONDAY TO 4
     PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...8 PM MONDAY TO 4
     PM TUESDAY.

&&

$$

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

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






000
FXUS63 KILX 290752
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
252 AM CDT Mon Sep 29 2014

.SHORT TERM...(Today)
ISSUED AT 251 AM CDT MON SEP 29 2014

Weak high pressure will provide another sunny and mild day across
central IL. Some early morning ground fog will develop in low lying
areas mainly near rivers and streams, but it will dissipate quickly
after sunrise. Some diurnally driven cumulus clouds in the 5-7k ft
layer could develop again today, based on the moisture profiles in
forecast soundings. Still plenty of dry air above and below that
moisture layer will mix together to keep clouds in check. Winds will
become north to northwest at 4 to 7 mph today, as a winds flow
clockwise around high pressure centered over N Missouri.


&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 251 AM CDT MON SEP 29 2014

Shortwave evident on water vapor imagery across northern parts of
North Dakota and Minnesota early this morning, and this should pinch
off into a closed low over lower Michigan by late evening. Latest
model guidance is pushing the associated surface boundary a bit
further south than previous runs, perhaps as far as I-72 by Tuesday
morning. However, the main energy will be near the closed low, so a
dry passage is on tap for us. Highs on Tuesday behind the front
should be in the mid to upper 70s across the northern CWA, with the
cooler 60s in northern Illinois. Some bust potential for highs
across the south if the front makes more progress than expected, but
will keep 80-85 degrees going there.

Main focus remains with midweek storm system. Upper low currently
spinning across southern Nevada, and is still progged to lift into
North Dakota by late Tuesday evening. As this feature lifts into
Canada, a deep long wave trough will drop across the Rockies on
Wednesday, reaching the Mississippi Valley by early Friday. The
trailing cold front from the earlier system should be moving into
the state on Thursday, with its speed depending on a surface low
riding along the boundary as the upper trough approaches. Severe
weather parameters are fair, with MUCAPE values of 500-1000 J/kg and
0-6km shear around 40 knots across the southern half of the CWA, per
the GFS and ECMWF models, as dew points rise into the upper 60s.
Initial surge of showers and storms expected to move in from west to
east Wednesday night, with likely PoP`s everywhere by Thursday. Some
model spread by Thursday night as to how fast the precipitation
ends, as the GFS is much slower and lingers the threat most of the
night, while the ECMWF and Canadian models are a bit more
progressive with the upper trough and dry it out west of I-55
already by early evening. Right now, will contain the likely PoP`s
to east of I-55 mainly during the evening.

Decent slug of cooler air to plunge into the Midwest behind this
front, as a cutoff low moves into the Upper Peninsula of Michigan.
ECMWF model brings the zero degree 850 mb isotherm into central
Illinois by late Friday evening, while the GFS is a couple degrees
warmer. Have kept Saturday highs at 60-65 for now, but if these
solutions persist, they would need to be lowered. Latest ECMWF would
give highs in the mid to upper 50s, with the GFS a few degrees
warmer.

Dry conditions expected during the weekend. Some moderation in
temperatures also on tap as the deeper part of the upper trough
shifts into the northeast states.


&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1100 PM CDT SUN SEP 28 2014

Little change from previous discussion with the main forecast
concern being the potential for some patchy MVFR vsbys in fog
from 10z thru 12z, otherwise, the majority of the forecast
period will have VFR conditions. Temp-dew point spreads were
still greater than 5 degrees across the entire area late this
evening. Similar conditions are expected during the daylight
hours on Monday that we had today with some scattered high
based cumulus forming after 16z, which should dissipate by
00z. Beyond 00z Tuesday, we will be watching a cold front slip
south into northern Illinois by early evening with a band of
MVFR cigs just behind the frontal boundary. Current thinking
is that the band of lower clouds will affect our northern TAF
sites (KPIA, KBMI) first, but not until after 06z. Surface
winds will remain calm overnight and be light and variable
on Monday.


&&

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

$$

SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...Smith







000
FXUS63 KLOT 290558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1258 AM CDT MON SEP 29 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

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

* PATCHY FOG LATE TONIGHT THROUGH EARLY MORNING. MVFR VSBY LIKELY
  WITH IFR VSBY POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST-NORTHWEST
  THIS AFTERNOON.

* COLD FRONTAL PASSAGE EARLY THIS EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIGS LIKELY BEHIND COLD FRONT THIS EVENING.

MDB

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

HIGH PRESSURE REMAINS IN CONTROL ACROSS THE AREA BUT IS WEAKENING.
CALM TO LIGHT AND VARIABLE WINDS ARE IN PLACE ONCE AGAIN WITH
CLEAR SKIES AND DEWPOINTS SIMILAR TO LAST NIGHT. PATCHY FOG HAS
ALREADY BEGUN TO DEVELOP AND WILL CONTINUE TO DO SO THROUGH THE
OVERNIGHT. EXPECT A GENERAL MVFR VSBY FOR MOST OF THE AREA IN THE
NEXT FEW HOURS WITH DENSER PATCHY/SHALLOW FOG BRINGING SOME IFR
VSBY AT TIMES. VISIBILITY WILL IMPROVE WITH SUNRISE WITH VFR BY
MID MORNING CONTINUING THROUGH THE AFTERNOON WITH LIGHT WEST TO
WEST-NORTHWEST WINDS THROUGH THE DAY.

A SHARP COLD FRONT WILL PUSH ACROSS THE TERMINALS FIRST THING THIS
EVENING BRINGING A SHIFT TO NORTHEAST WINDS AND AN INCREASE IN
WIND SPEEDS/GUSTS. HAVE SPED UP THE TIMING SLIGHTLY WITH FRONTS
SUCH AS THIS OFTEN ACCELERATING DOWN LAKE MICHIGAN. COOLER AIR
WILL SPREAD IN BRINGING AN INCREASE IN LOW STRATUS. WILL CARRY LOW
END MVFR CIGS BEHIND THE FRONT THIS EVENING BUT IFR IS POSSIBLE.
VSBY MAY BE REDUCED IN MIST/HAZE AS THE COLDER AIR ARRIVES AND
THERE MAY BE SOME DRIZZLE THAT TRIES TO SET UP. MAY NEED TO LOWER
CIGS/VSBY FOR THE EVENING IF THE DRIZZLE ENDS UP BECOMING
WIDESPREAD.

MDB


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

* MEDIUM CONFIDENCE IN VSBY IN FOG LATE TONIGHT/EARLY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS THIS MORNING/EARLY AFTERNOON AND EXACT
  TIMING OF SHIFT TO NORTHEAST WINDS THIS EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIGS DEVELOPING THIS
  EVENING BEHIND COLD FRONT.

MDB

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 290401
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1101 PM CDT Sun Sep 28 2014

.UPDATE...
ISSUED AT 825 PM CDT SUN SEP 28 2014

Quiet weather to continue through the overnight hours as high
pressure holds just north of our area this evening. Weak cold
front across far northern Wisconsin will slip south across the
lower Great Lakes Monday evening and may bring us some cooler
temperatures by Tuesday. Until then, little change is expected
with a pleasant overnight as lows dip into the 50s and another
rather large diurnal swing in temps expected on Monday with
afternoon highs soaring back into the middle 80s. Have made some
adjustments to the temperatures for Monday afternoon as
temperatures aloft will change little, so am not expecting any
significant changes in afternoon highs compared with the last two
days. Should have the update out by 845 pm.

&&

.SHORT TERM...(Tonight)
ISSUED AT 302 PM CDT SUN SEP 28 2014

The 581 dm 500mb low over central Iowa will become an open wave and
drift southeast across MO and sw IL tonight. That will just bring
scattered cirrus clouds with it to central IL, while diurnally driven
few to scattered cumulus clouds 5-7k ft dissipate around sunset. A
shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to develop again near river valleys like the
IL and Wabash rivers overnight. Any fog that develops overnight
should dissipate by 830 am Monday morning. Lows overnight will be
similar to last night lows and current dewpoints in the low to mid
50s with coolest readings over east central IL. Winds will remain
light to calm through Monday morning under a weak surface pressure
gradient as 1021 mb high pressure and ridging into WI, northern IL
and eastern IA remains in place through Monday.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 302 PM CDT SUN SEP 28 2014

Quiet weather is still expected for the start of the work week.
Shortwave currently entering western Saskatchewan will be digging as
it approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will push a cold front southward, with all
models indicating it getting into central IL before lifting back
north as a warm front on Wednesday.

Then a broad trough in the Rockies will slowly move east into the
plains. The first surface low associated with this feature will lift
northeast into the northern plains with showers and thunderstorms
trailing just ahead of a front in the plains, slowly moving east.
This first batch of pcpn will not make it into the CWA, as it will
be well away from it`s best support and it will be moving into a
strong ridge. The cold front will still be west of the area, but
will refire with showers and thunderstorms Wed night. The front will
also be moving into the area Wed night and Thur, so pcpn will become
likely through Thur night, across the CWA. A strong surge of cooler
air move into the midwest on Friday behind the front. Models differ
on timing of all this pcpn and believe the ECMWF/GEM have the best
handle on the timing of onset of the pcpn, while the GFS is too
fast. Beyond this system and into the weekend, much cooler high
pressure will build into the area for the weekend.

850 mb temperatures in the 13-15C range will keep our highs above
normal, with some cooling on Tuesday as the front moves south into
the CWA and then back north Tue night. Temps will stay above normal
for Thur ahead of the cold front and pcpn, but then cool behind this
front for the remainder of the week and into the weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
ISSUED AT 1100 PM CDT SUN SEP 28 2014

Little change from previous discussion with the main forecast
concern being the potential for some patchy MVFR vsbys in fog
from 10z thru 12z, otherwise, the majority of the forecast
period will have VFR conditions. Temp-dew point spreads were
still greater than 5 degrees across the entire area late this
evening. Similar conditions are expected during the daylight
hours on Monday that we had today with some scattered high
based cumulus forming after 16z, which should dissipate by
00z. Beyond 00z Tuesday, we will be watching a cold front slip
south into northern Illinois by early evening with a band of
MVFR cigs just behind the frontal boundary. Current thinking
is that the band of lower clouds will affect our northern TAF
sites (KPIA, KBMI) first, but not until after 06z. Surface
winds will remain calm overnight and be light and variable
on Monday.

&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith





000
FXUS63 KLOT 290259
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
959 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* PATCHY FOG LATE TONIGHT AND EARLY MONDAY MORNING. MVFR VIS
  LIKELY WITH IFR VIS POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST- NORTHWEST
  MONDAY.

* COLD FRONTAL PASSAGE EARLY MONDAY EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIG LIKELY BEHIND COLD FRONT MONDAY EVENING.

RATZER

//DISCUSSION...UPDATED 00Z...

SURFACE HIGH PRESSURE RIDGE REMAINS OVER THE REGION THIS EVENING.
OTHER THAN LINGERING LIGHT EAST-NORTHEAST LAKE BREEZE WIND EARLY
THIS EVENING...LIGHT/VARIABLE OR CALM WINDS ARE EXPECTED
OVERNIGHT. THE COMBINATION OF CALM WINDS...MAINLY CLEAR SKIES AND
STABLE LOW LEVELS WILL ALLOW FOR PATCHY FOG DEVELOPMENT WHICH WILL
LIKELY PRODUCE MVFR VSBYS IN MANY AREAS...WITH IFR VSBYS POSSIBLE
TOWARD SUNRISE.

WINDS WILL REMAINS LIGHT MONDAY...WITH A VARIABLE BUT MAINLY
WESTERLY DIRECTION DEVELOPING AHEAD OF AN APPROACHING STRONG COLD
FRONT. CURRENT GUIDANCE CONTINUES TO PUSH THE FRONT INTO TERMINAL
AREA IN THE 00-02Z TIME FRAME EARLY MONDAY EVENING...WITH A QUICK
SHIFT TO BREEZY NORTHEAST WINDS WITH GUSTS 15-20 KT. STRONG COLD
ADVECTION BEHIND THE FRONT IS EXPECTED TO SATURATE THE LOW
LEVELS...WITH LOW MVFR OR IFR CEILINGS EXPECTED. FRONT LOOKS TO
COME THROUGH WITHOUT SIGNIFICANT PRECIPITATION...THOUGH SOME
SPRINKLES OR DRIZZLE WILL BE POSSIBLE MONDAY NIGHT IN THE
COOL/MOIST AIR BEHIND THE FRONT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM CONFIDENCE IN VIS IN FOG LATE TONIGHT/MONDAY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS MONDAY AND EXACT TIMING OF SHIFT TO
  NORTHEAST WINDS MONDAY EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIG DEVELOPING MONDAY
  EVENING.

RATZER

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 290259
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
959 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* PATCHY FOG LATE TONIGHT AND EARLY MONDAY MORNING. MVFR VIS
  LIKELY WITH IFR VIS POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST- NORTHWEST
  MONDAY.

* COLD FRONTAL PASSAGE EARLY MONDAY EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIG LIKELY BEHIND COLD FRONT MONDAY EVENING.

RATZER

//DISCUSSION...UPDATED 00Z...

SURFACE HIGH PRESSURE RIDGE REMAINS OVER THE REGION THIS EVENING.
OTHER THAN LINGERING LIGHT EAST-NORTHEAST LAKE BREEZE WIND EARLY
THIS EVENING...LIGHT/VARIABLE OR CALM WINDS ARE EXPECTED
OVERNIGHT. THE COMBINATION OF CALM WINDS...MAINLY CLEAR SKIES AND
STABLE LOW LEVELS WILL ALLOW FOR PATCHY FOG DEVELOPMENT WHICH WILL
LIKELY PRODUCE MVFR VSBYS IN MANY AREAS...WITH IFR VSBYS POSSIBLE
TOWARD SUNRISE.

WINDS WILL REMAINS LIGHT MONDAY...WITH A VARIABLE BUT MAINLY
WESTERLY DIRECTION DEVELOPING AHEAD OF AN APPROACHING STRONG COLD
FRONT. CURRENT GUIDANCE CONTINUES TO PUSH THE FRONT INTO TERMINAL
AREA IN THE 00-02Z TIME FRAME EARLY MONDAY EVENING...WITH A QUICK
SHIFT TO BREEZY NORTHEAST WINDS WITH GUSTS 15-20 KT. STRONG COLD
ADVECTION BEHIND THE FRONT IS EXPECTED TO SATURATE THE LOW
LEVELS...WITH LOW MVFR OR IFR CEILINGS EXPECTED. FRONT LOOKS TO
COME THROUGH WITHOUT SIGNIFICANT PRECIPITATION...THOUGH SOME
SPRINKLES OR DRIZZLE WILL BE POSSIBLE MONDAY NIGHT IN THE
COOL/MOIST AIR BEHIND THE FRONT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM CONFIDENCE IN VIS IN FOG LATE TONIGHT/MONDAY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS MONDAY AND EXACT TIMING OF SHIFT TO
  NORTHEAST WINDS MONDAY EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIG DEVELOPING MONDAY
  EVENING.

RATZER

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 290259
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
959 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* PATCHY FOG LATE TONIGHT AND EARLY MONDAY MORNING. MVFR VIS
  LIKELY WITH IFR VIS POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST- NORTHWEST
  MONDAY.

* COLD FRONTAL PASSAGE EARLY MONDAY EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIG LIKELY BEHIND COLD FRONT MONDAY EVENING.

RATZER

//DISCUSSION...UPDATED 00Z...

SURFACE HIGH PRESSURE RIDGE REMAINS OVER THE REGION THIS EVENING.
OTHER THAN LINGERING LIGHT EAST-NORTHEAST LAKE BREEZE WIND EARLY
THIS EVENING...LIGHT/VARIABLE OR CALM WINDS ARE EXPECTED
OVERNIGHT. THE COMBINATION OF CALM WINDS...MAINLY CLEAR SKIES AND
STABLE LOW LEVELS WILL ALLOW FOR PATCHY FOG DEVELOPMENT WHICH WILL
LIKELY PRODUCE MVFR VSBYS IN MANY AREAS...WITH IFR VSBYS POSSIBLE
TOWARD SUNRISE.

WINDS WILL REMAINS LIGHT MONDAY...WITH A VARIABLE BUT MAINLY
WESTERLY DIRECTION DEVELOPING AHEAD OF AN APPROACHING STRONG COLD
FRONT. CURRENT GUIDANCE CONTINUES TO PUSH THE FRONT INTO TERMINAL
AREA IN THE 00-02Z TIME FRAME EARLY MONDAY EVENING...WITH A QUICK
SHIFT TO BREEZY NORTHEAST WINDS WITH GUSTS 15-20 KT. STRONG COLD
ADVECTION BEHIND THE FRONT IS EXPECTED TO SATURATE THE LOW
LEVELS...WITH LOW MVFR OR IFR CEILINGS EXPECTED. FRONT LOOKS TO
COME THROUGH WITHOUT SIGNIFICANT PRECIPITATION...THOUGH SOME
SPRINKLES OR DRIZZLE WILL BE POSSIBLE MONDAY NIGHT IN THE
COOL/MOIST AIR BEHIND THE FRONT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM CONFIDENCE IN VIS IN FOG LATE TONIGHT/MONDAY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS MONDAY AND EXACT TIMING OF SHIFT TO
  NORTHEAST WINDS MONDAY EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIG DEVELOPING MONDAY
  EVENING.

RATZER

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KLOT 290259
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
959 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 03Z...

* PATCHY FOG LATE TONIGHT AND EARLY MONDAY MORNING. MVFR VIS
  LIKELY WITH IFR VIS POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST- NORTHWEST
  MONDAY.

* COLD FRONTAL PASSAGE EARLY MONDAY EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIG LIKELY BEHIND COLD FRONT MONDAY EVENING.

RATZER

//DISCUSSION...UPDATED 00Z...

SURFACE HIGH PRESSURE RIDGE REMAINS OVER THE REGION THIS EVENING.
OTHER THAN LINGERING LIGHT EAST-NORTHEAST LAKE BREEZE WIND EARLY
THIS EVENING...LIGHT/VARIABLE OR CALM WINDS ARE EXPECTED
OVERNIGHT. THE COMBINATION OF CALM WINDS...MAINLY CLEAR SKIES AND
STABLE LOW LEVELS WILL ALLOW FOR PATCHY FOG DEVELOPMENT WHICH WILL
LIKELY PRODUCE MVFR VSBYS IN MANY AREAS...WITH IFR VSBYS POSSIBLE
TOWARD SUNRISE.

WINDS WILL REMAINS LIGHT MONDAY...WITH A VARIABLE BUT MAINLY
WESTERLY DIRECTION DEVELOPING AHEAD OF AN APPROACHING STRONG COLD
FRONT. CURRENT GUIDANCE CONTINUES TO PUSH THE FRONT INTO TERMINAL
AREA IN THE 00-02Z TIME FRAME EARLY MONDAY EVENING...WITH A QUICK
SHIFT TO BREEZY NORTHEAST WINDS WITH GUSTS 15-20 KT. STRONG COLD
ADVECTION BEHIND THE FRONT IS EXPECTED TO SATURATE THE LOW
LEVELS...WITH LOW MVFR OR IFR CEILINGS EXPECTED. FRONT LOOKS TO
COME THROUGH WITHOUT SIGNIFICANT PRECIPITATION...THOUGH SOME
SPRINKLES OR DRIZZLE WILL BE POSSIBLE MONDAY NIGHT IN THE
COOL/MOIST AIR BEHIND THE FRONT.

RATZER

//ORD AND MDW CONFIDENCE...UPDATED 03Z...

* MEDIUM CONFIDENCE IN VIS IN FOG LATE TONIGHT/MONDAY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS MONDAY AND EXACT TIMING OF SHIFT TO
  NORTHEAST WINDS MONDAY EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIG DEVELOPING MONDAY
  EVENING.

RATZER

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO








000
FXUS63 KILX 290132
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
832 PM CDT Sun Sep 28 2014

.UPDATE...
ISSUED AT 825 PM CDT SUN SEP 28 2014

Quiet weather to continue through the overnight hours as high
pressure holds just north of our area this evening. Weak cold
front across far northern Wisconsin will slip south across the
lower Great Lakes Monday evening and may bring us some cooler
temperatures by Tuesday. Until then, little change is expected
with a pleasant overnight as lows dip into the 50s and another
rather large diurnal swing in temps expected on Monday with
afternoon highs soaring back into the middle 80s. Have made some
adjustments to the temperatures for Monday afternoon as
temperatures aloft will change little, so am not expecting any
significant changes in afternoon highs compared with the last two
days. Should have the update out by 845 pm.

&&

.SHORT TERM...(Tonight)
ISSUED AT 302 PM CDT SUN SEP 28 2014

The 581 dm 500mb low over central Iowa will become an open wave and
drift southeast across MO and sw IL tonight. That will just bring
scattered cirrus clouds with it to central IL, while diurnally driven
few to scattered cumulus clouds 5-7k ft dissipate around sunset. A
shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to develop again near river valleys like the
IL and Wabash rivers overnight. Any fog that develops overnight
should dissipate by 830 am Monday morning. Lows overnight will be
similar to last night lows and current dewpoints in the low to mid
50s with coolest readings over east central IL. Winds will remain
light to calm through Monday morning under a weak surface pressure
gradient as 1021 mb high pressure and ridging into WI, northern IL
and eastern IA remains in place through Monday.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 302 PM CDT SUN SEP 28 2014

Quiet weather is still expected for the start of the work week.
Shortwave currently entering western Saskatchewan will be digging as
it approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will push a cold front southward, with all
models indicating it getting into central IL before lifting back
north as a warm front on Wednesday.

Then a broad trough in the Rockies will slowly move east into the
plains. The first surface low associated with this feature will lift
northeast into the northern plains with showers and thunderstorms
trailing just ahead of a front in the plains, slowly moving east.
This first batch of pcpn will not make it into the CWA, as it will
be well away from it`s best support and it will be moving into a
strong ridge. The cold front will still be west of the area, but
will refire with showers and thunderstorms Wed night. The front will
also be moving into the area Wed night and Thur, so pcpn will become
likely through Thur night, across the CWA. A strong surge of cooler
air move into the midwest on Friday behind the front. Models differ
on timing of all this pcpn and believe the ECMWF/GEM have the best
handle on the timing of onset of the pcpn, while the GFS is too
fast. Beyond this system and into the weekend, much cooler high
pressure will build into the area for the weekend.

850 mb temperatures in the 13-15C range will keep our highs above
normal, with some cooling on Tuesday as the front moves south into
the CWA and then back north Tue night. Temps will stay above normal
for Thur ahead of the cold front and pcpn, but then cool behind this
front for the remainder of the week and into the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 600 PM CDT SUN SEP 28 2014

Other than the threat for patchy MVFR vsbys in fog between 10z-
12z, VFR conditions are expected for the rest of this forecast
period. High pressure off to our east will continue to dominate
the weather for the next 24 to 36 hours. Forecast soundings
once again indicate some high based cumulus to form late tomorrow
morning into the afternoon hours with bases in the 5000-6000 foot
range. Surface winds will remain light and variable thru the period.


&&

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

$$

UPDATE...Smith
SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith






000
FXUS63 KLOT 282353
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
653 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* PATCHY FOG LATE TONIGHT AND EARLY MONDAY MORNING. MVFR VIS
  LIKELY WITH IFR VIS POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST- NORTHWEST
  MONDAY.

* COLD FRONTAL PASSAGE EARLY MONDAY EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIG LIKELY BEHIND COLD FRONT MONDAY EVENING.

RATZER

//DISCUSSION...UPDATED 00Z...

SURFACE HIGH PRESSURE RIDGE REMAINS OVER THE REGION THIS EVENING.
OTHER THAN LINGERING LIGHT EAST-NORTHEAST LAKE BREEZE WIND EARLY
THIS EVENING...LIGHT/VARIABLE OR CALM WINDS ARE EXPECTED
OVERNIGHT. THE COMBINATION OF CALM WINDS...MAINLY CLEAR SKIES AND
STABLE LOW LEVELS WILL ALLOW FOR PATCHY FOG DEVELOPMENT WHICH WILL
LIKELY PRODUCE MVFR VSBYS IN MANY AREAS...WITH IFR VSBYS POSSIBLE
TOWARD SUNRISE.

WINDS WILL REMAINS LIGHT MONDAY...WITH A VARIABLE BUT MAINLY
WESTERLY DIRECTION DEVELOPING AHEAD OF AN APPROACHING STRONG COLD
FRONT. CURRENT GUIDANCE CONTINUES TO PUSH THE FRONT INTO TERMINAL
AREA IN THE 00-02Z TIME FRAME EARLY MONDAY EVENING...WITH A QUICK
SHIFT TO BREEZY NORTHEAST WINDS WITH GUSTS 15-20 KT. STRONG COLD
ADVECTION BEHIND THE FRONT IS EXPECTED TO SATURATE THE LOW
LEVELS...WITH LOW MVFR OR IFR CEILINGS EXPECTED. FRONT LOOKS TO
COME THROUGH WITHOUT SIGNIFICANT PRECIPITATION...THOUGH SOME
SPRINKLES OR DRIZZLE WILL BE POSSIBLE MONDAY NIGHT IN THE
COOL/MOIST AIR BEHIND THE FRONT.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN VIS IN FOG LATE TONIGHT/MONDAY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS MONDAY AND EXACT TIMING OF SHIFT TO
  NORTHEAST WINDS MONDAY EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIG DEVELOPING MONDAY
  EVENING.

RATZER

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KLOT 282353
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
653 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 00Z...

* PATCHY FOG LATE TONIGHT AND EARLY MONDAY MORNING. MVFR VIS
  LIKELY WITH IFR VIS POSSIBLE.

* VARIABLE/CALM WINDS OVERNIGHT...BECOMING LIGHT WEST- NORTHWEST
  MONDAY.

* COLD FRONTAL PASSAGE EARLY MONDAY EVENING WITH WIND SHIFT TO THE
  NORTHEAST AND GUSTS 15-20 KT DEVELOPING.

* MVFR/IFR CIG LIKELY BEHIND COLD FRONT MONDAY EVENING.

RATZER

//DISCUSSION...UPDATED 00Z...

SURFACE HIGH PRESSURE RIDGE REMAINS OVER THE REGION THIS EVENING.
OTHER THAN LINGERING LIGHT EAST-NORTHEAST LAKE BREEZE WIND EARLY
THIS EVENING...LIGHT/VARIABLE OR CALM WINDS ARE EXPECTED
OVERNIGHT. THE COMBINATION OF CALM WINDS...MAINLY CLEAR SKIES AND
STABLE LOW LEVELS WILL ALLOW FOR PATCHY FOG DEVELOPMENT WHICH WILL
LIKELY PRODUCE MVFR VSBYS IN MANY AREAS...WITH IFR VSBYS POSSIBLE
TOWARD SUNRISE.

WINDS WILL REMAINS LIGHT MONDAY...WITH A VARIABLE BUT MAINLY
WESTERLY DIRECTION DEVELOPING AHEAD OF AN APPROACHING STRONG COLD
FRONT. CURRENT GUIDANCE CONTINUES TO PUSH THE FRONT INTO TERMINAL
AREA IN THE 00-02Z TIME FRAME EARLY MONDAY EVENING...WITH A QUICK
SHIFT TO BREEZY NORTHEAST WINDS WITH GUSTS 15-20 KT. STRONG COLD
ADVECTION BEHIND THE FRONT IS EXPECTED TO SATURATE THE LOW
LEVELS...WITH LOW MVFR OR IFR CEILINGS EXPECTED. FRONT LOOKS TO
COME THROUGH WITHOUT SIGNIFICANT PRECIPITATION...THOUGH SOME
SPRINKLES OR DRIZZLE WILL BE POSSIBLE MONDAY NIGHT IN THE
COOL/MOIST AIR BEHIND THE FRONT.

RATZER


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN VIS IN FOG LATE TONIGHT/MONDAY AM.

* HIGH CONFIDENCE IN WIND TRENDS...THOUGH MEDIUM CONFIDENCE IN
  DIRECTION OF LIGHT WINDS MONDAY AND EXACT TIMING OF SHIFT TO
  NORTHEAST WINDS MONDAY EVENING.

* MEDIUM-HIGH CONFIDENCE IN LOW MVFR/HIGH IFR CIG DEVELOPING MONDAY
  EVENING.

RATZER

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

TUESDAY...MVFR CIGS LIKELY AND IFR CIG POSSIBLE IN THE MORNING.
NORTHEAST WINDS.

WEDNESDAY...VFR. LAKE BREEZE LIKELY.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

RATZER

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KILX 282310
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
610 PM CDT Sun Sep 28 2014

.SHORT TERM...(Tonight)
ISSUED AT 302 PM CDT SUN SEP 28 2014

The 581 dm 500mb low over central Iowa will become an open wave and
drift southeast across MO and sw IL tonight. That will just bring
scattered cirrus clouds with it to central IL, while diurnally driven
few to scattered cumulus clouds 5-7k ft dissipate around sunset. A
shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to develop again near river valleys like the
IL and Wabash rivers overnight. Any fog that develops overnight
should dissipate by 830 am Monday morning. Lows overnight will be
similar to last night lows and current dewpoints in the low to mid
50s with coolest readings over east central IL. Winds will remain
light to calm through Monday morning under a weak surface pressure
gradient as 1021 mb high pressure and ridging into WI, northern IL
and eastern IA remains in place through Monday.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 302 PM CDT SUN SEP 28 2014

Quiet weather is still expected for the start of the work week.
Shortwave currently entering western Saskatchewan will be digging as
it approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will push a cold front southward, with all
models indicating it getting into central IL before lifting back
north as a warm front on Wednesday.

Then a broad trough in the Rockies will slowly move east into the
plains. The first surface low associated with this feature will lift
northeast into the northern plains with showers and thunderstorms
trailing just ahead of a front in the plains, slowly moving east.
This first batch of pcpn will not make it into the CWA, as it will
be well away from it`s best support and it will be moving into a
strong ridge. The cold front will still be west of the area, but
will refire with showers and thunderstorms Wed night. The front will
also be moving into the area Wed night and Thur, so pcpn will become
likely through Thur night, across the CWA. A strong surge of cooler
air move into the midwest on Friday behind the front. Models differ
on timing of all this pcpn and believe the ECMWF/GEM have the best
handle on the timing of onset of the pcpn, while the GFS is too
fast. Beyond this system and into the weekend, much cooler high
pressure will build into the area for the weekend.

850 mb temperatures in the 13-15C range will keep our highs above
normal, with some cooling on Tuesday as the front moves south into
the CWA and then back north Tue night. Temps will stay above normal
for Thur ahead of the cold front and pcpn, but then cool behind this
front for the remainder of the week and into the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 600 PM CDT SUN SEP 28 2014

Other than the threat for patchy MVFR vsbys in fog between 10z-
12z, VFR conditions are expected for the rest of this forecast
period. High pressure off to our east will continue to dominate
the weather for the next 24 to 36 hours. Forecast soundings
once again indicate some high based cumulus to form late tomorrow
morning into the afternoon hours with bases in the 5000-6000 foot
range. Surface winds will remain light and variable thru the period.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith





000
FXUS63 KILX 282310
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
610 PM CDT Sun Sep 28 2014

.SHORT TERM...(Tonight)
ISSUED AT 302 PM CDT SUN SEP 28 2014

The 581 dm 500mb low over central Iowa will become an open wave and
drift southeast across MO and sw IL tonight. That will just bring
scattered cirrus clouds with it to central IL, while diurnally driven
few to scattered cumulus clouds 5-7k ft dissipate around sunset. A
shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to develop again near river valleys like the
IL and Wabash rivers overnight. Any fog that develops overnight
should dissipate by 830 am Monday morning. Lows overnight will be
similar to last night lows and current dewpoints in the low to mid
50s with coolest readings over east central IL. Winds will remain
light to calm through Monday morning under a weak surface pressure
gradient as 1021 mb high pressure and ridging into WI, northern IL
and eastern IA remains in place through Monday.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 302 PM CDT SUN SEP 28 2014

Quiet weather is still expected for the start of the work week.
Shortwave currently entering western Saskatchewan will be digging as
it approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will push a cold front southward, with all
models indicating it getting into central IL before lifting back
north as a warm front on Wednesday.

Then a broad trough in the Rockies will slowly move east into the
plains. The first surface low associated with this feature will lift
northeast into the northern plains with showers and thunderstorms
trailing just ahead of a front in the plains, slowly moving east.
This first batch of pcpn will not make it into the CWA, as it will
be well away from it`s best support and it will be moving into a
strong ridge. The cold front will still be west of the area, but
will refire with showers and thunderstorms Wed night. The front will
also be moving into the area Wed night and Thur, so pcpn will become
likely through Thur night, across the CWA. A strong surge of cooler
air move into the midwest on Friday behind the front. Models differ
on timing of all this pcpn and believe the ECMWF/GEM have the best
handle on the timing of onset of the pcpn, while the GFS is too
fast. Beyond this system and into the weekend, much cooler high
pressure will build into the area for the weekend.

850 mb temperatures in the 13-15C range will keep our highs above
normal, with some cooling on Tuesday as the front moves south into
the CWA and then back north Tue night. Temps will stay above normal
for Thur ahead of the cold front and pcpn, but then cool behind this
front for the remainder of the week and into the weekend.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 600 PM CDT SUN SEP 28 2014

Other than the threat for patchy MVFR vsbys in fog between 10z-
12z, VFR conditions are expected for the rest of this forecast
period. High pressure off to our east will continue to dominate
the weather for the next 24 to 36 hours. Forecast soundings
once again indicate some high based cumulus to form late tomorrow
morning into the afternoon hours with bases in the 5000-6000 foot
range. Surface winds will remain light and variable thru the period.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...Smith






000
FXUS63 KLOT 282205
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
505 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* LIGHT EAST WINDS AT 8KT OR LESS FOR REMAINDER OF AFTERNOON.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KRIEN/RATZER

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN/RATZER

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO






000
FXUS63 KILX 282003
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
303 PM CDT Sun Sep 28 2014

.SHORT TERM...(Tonight)
ISSUED AT 302 PM CDT SUN SEP 28 2014

The 581 dm 500mb low over central Iowa will become an open wave and
drift southeast across MO and sw IL tonight. That will just bring
scattered cirrus clouds with it to central IL, while diurnally driven
few to scattered cumulus clouds 5-7k ft dissipate around sunset. A
shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to develop again near river valleys like the
IL and Wabash rivers overnight. Any fog that develops overnight
should dissipate by 830 am Monday morning. Lows overnight will be
similar to last night lows and current dewpoints in the low to mid
50s with coolest readings over east central IL. Winds will remain
light to calm through Monday morning under a weak surface pressure
gradient as 1021 mb high pressure and ridging into WI, northern IL
and eastern IA remains in place through Monday.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 302 PM CDT SUN SEP 28 2014

Quiet weather is still expected for the start of the work week.
Shortwave currently entering western Saskatchewan will be digging as
it approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will push a cold front southward, with all
models indicating it getting into central IL before lifting back
north as a warm front on Wednesday.

Then a broad trough in the Rockies will slowly move east into the
plains. The first surface low associated with this feature will lift
northeast into the northern plains with showers and thunderstorms
trailing just ahead of a front in the plains, slowly moving east.
This first batch of pcpn will not make it into the CWA, as it will
be well away from it`s best support and it will be moving into a
strong ridge. The cold front will still be west of the area, but
will refire with showers and thunderstorms Wed night. The front will
also be moving into the area Wed night and Thur, so pcpn will become
likely through Thur night, across the CWA. A strong surge of cooler
air move into the midwest on Friday behind the front. Models differ
on timing of all this pcpn and believe the ECMWF/GEM have the best
handle on the timing of onset of the pcpn, while the GFS is too
fast. Beyond this system and into the weekend, much cooler high
pressure will build into the area for the weekend.

850 mb temperatures in the 13-15C range will keep our highs above
normal, with some cooling on Tuesday as the front moves south into
the CWA and then back north Tue night. Temps will stay above normal
for Thur ahead of the cold front and pcpn, but then cool behind this
front for the remainder of the week and into the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1245 PM CDT SUN SEP 28 2014

Used persistance for the central IL aviation forecast next 24 hours
through 18Z/Mon. Few to scattered cumulus clouds 5-7k ft this
afternoon especially from I-55 west, will dissipate by sunset at
2345Z. Otherwise patches of high clouds to occur next 24 hours
while few-scattered cumulus clouds reappear after 16Z Mon especially
from I-55 west again. Light and variable winds to prevail through
early Mon morning and then have nnw winds 3-5 kts after 16Z Monday.
1022 mb high pressure over lower MI and ridging westward into WI,
northern IL and eastern IA to remain near central IL through
Monday. This to continue fair weather through Monday as upper
level ridge extends from Texas up to IL. Patchy shallow ground fog
possible from 09-13Z along IL river at PIA where vsbys could lower
to MVFR of 5 miles.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...07







000
FXUS63 KILX 282003
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
303 PM CDT Sun Sep 28 2014

.SHORT TERM...(Tonight)
ISSUED AT 302 PM CDT SUN SEP 28 2014

The 581 dm 500mb low over central Iowa will become an open wave and
drift southeast across MO and sw IL tonight. That will just bring
scattered cirrus clouds with it to central IL, while diurnally driven
few to scattered cumulus clouds 5-7k ft dissipate around sunset. A
shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to develop again near river valleys like the
IL and Wabash rivers overnight. Any fog that develops overnight
should dissipate by 830 am Monday morning. Lows overnight will be
similar to last night lows and current dewpoints in the low to mid
50s with coolest readings over east central IL. Winds will remain
light to calm through Monday morning under a weak surface pressure
gradient as 1021 mb high pressure and ridging into WI, northern IL
and eastern IA remains in place through Monday.

&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 302 PM CDT SUN SEP 28 2014

Quiet weather is still expected for the start of the work week.
Shortwave currently entering western Saskatchewan will be digging as
it approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will push a cold front southward, with all
models indicating it getting into central IL before lifting back
north as a warm front on Wednesday.

Then a broad trough in the Rockies will slowly move east into the
plains. The first surface low associated with this feature will lift
northeast into the northern plains with showers and thunderstorms
trailing just ahead of a front in the plains, slowly moving east.
This first batch of pcpn will not make it into the CWA, as it will
be well away from it`s best support and it will be moving into a
strong ridge. The cold front will still be west of the area, but
will refire with showers and thunderstorms Wed night. The front will
also be moving into the area Wed night and Thur, so pcpn will become
likely through Thur night, across the CWA. A strong surge of cooler
air move into the midwest on Friday behind the front. Models differ
on timing of all this pcpn and believe the ECMWF/GEM have the best
handle on the timing of onset of the pcpn, while the GFS is too
fast. Beyond this system and into the weekend, much cooler high
pressure will build into the area for the weekend.

850 mb temperatures in the 13-15C range will keep our highs above
normal, with some cooling on Tuesday as the front moves south into
the CWA and then back north Tue night. Temps will stay above normal
for Thur ahead of the cold front and pcpn, but then cool behind this
front for the remainder of the week and into the weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1245 PM CDT SUN SEP 28 2014

Used persistance for the central IL aviation forecast next 24 hours
through 18Z/Mon. Few to scattered cumulus clouds 5-7k ft this
afternoon especially from I-55 west, will dissipate by sunset at
2345Z. Otherwise patches of high clouds to occur next 24 hours
while few-scattered cumulus clouds reappear after 16Z Mon especially
from I-55 west again. Light and variable winds to prevail through
early Mon morning and then have nnw winds 3-5 kts after 16Z Monday.
1022 mb high pressure over lower MI and ridging westward into WI,
northern IL and eastern IA to remain near central IL through
Monday. This to continue fair weather through Monday as upper
level ridge extends from Texas up to IL. Patchy shallow ground fog
possible from 09-13Z along IL river at PIA where vsbys could lower
to MVFR of 5 miles.

&&

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

$$

SHORT TERM...07
LONG TERM...Auten
AVIATION...07






000
FXUS63 KLOT 281959
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
259 PM CDT SUN SEP 28 2014

.DISCUSSION...
259 PM CDT

SYNOPSIS...

THE LONG STRETCH OF WARM AND DRY WEATHER WILL COME TO AN
END THIS WEEK...BUT NOT BEFORE ONE MORE BEAUTIFUL DAY ON MONDAY. THE
FIRST SIGN OF A CHANGE IN THE WEATHER PATTERN WILL COME WITH A COLD
FRONT PASSAGE ON MONDAY NIGHT THAT WILL RESULT IN MUCH COOLER
TEMPERATURES ON TUESDAY...MOST NOTABLY NEAR THE LAKE. A STORM SYSTEM
LATE IN THE WEEK WILL BRING THE POTENTIAL FOR AT LEAST A PERIOD OR
TWO OF FAIRLY WIDESPREAD SHOWERS AND STORMS WEDNESDAY NIGHT INTO
THURSDAY NIGHT...THEN MUCH COOLER AIR WILL ARRIVE AREA WIDE FRIDAY
INTO NEXT WEEKEND.

TONIGHT AND MONDAY...

ANOTHER NIGHT OF LITTLE TO NO CHANGE IN AIR MASS AND CALM WINDS WITH
SFC HIGH OVER REGION...SO STAYED CLOSED TO OBSERVED LOWS FOR MINS
TONIGHT. THOUGH DEW POINTS DID MIX OUT IN SPOTS THIS
AFTERNOON...STATISTICAL AND HI-RES GUIDANCE IN GOOD AGREEMENT IN
PATCHY FOG AND HAZE OVERNIGHT...WITH AREAS OF FOG IN FAR NORTHEAST
IL. COULD SEE LOCALLY DENSE FOG IN SOME SPOTS. THIS SEEMS REASONABLE
GIVEN THAT FOG WAS ABLE TO DEVELOP EARLY THIS MORNING DESPITE FAIRLY
DENSE CIRRUS AND EXPECTING LESS CIRRUS TONIGHT. BOUNDARY LAYER FLOW
WILL SHIFT TO LIGHT WEST-NORTHWEST AHEAD OF COLD FRONT ON
MONDAY...BUT FLOW SHOULD STILL BE LIGHT ENOUGH FOR LAKE BREEZE TO
FORM. ANTICIPATING HIGHS GENERALLY IN THE LOWER 80S INLAND...WITH A
FEW MID 80S IN SW 1/3 OF CWA. LATER LAKE BREEZE FORMATION SHOULD
ENABLE SHORE TO REACH MID TO UPPER 70S.

MONDAY NIGHT AND TUESDAY...

SHARP BACKDOOR COLD FRONT WILL SWEEP SOUTH DURING EVENING WITH GUSTY
NORTHERLY WINDS AND FALLING TEMPS. THIS WILL BE FOLLOWED BY
EXTENSIVE STRATUS DECK OOZING SOUTHWARD THROUGH THE NIGHT. CONTINUE
TO FEATURE SLIGHT CHANCE POPS IN NORTHEAST ILLINOIS DURING EVENING
AND OVERNIGHT AS FORCING FROM SHARP UPPER TROUGH PASSING THROUGH THE
GREAT LAKES GIVES A GLANCING BLOW...THOUGH COULD BE MORE OF A
SPRINKLES/DRIZZLE SET-UP.

THE MODELS ARE IN GOOD AGREEMENT IN MOISTURE GETTING TRAPPED BENEATH
INVERSION AND POSSIBLY TAKING MUCH OF THE DAY ON TUESDAY TO SCOUR
OUT...ESPECIALLY NEAR THE LAKE. ONSHORE FLOW AND ONLY SLOW EROSION
OF CLOUD COVER EXPECTED TO KEEP LAKESHORE HIGHS IN THE UPPER 50S TO
LOWER 60S...WHILE AREAS WELL AWAY FROM THE LAKE SHOULD WARM INTO 60S
AND 70S WITH EXPECTATION OF CLOUD DECK ERODING FROM SOUTH/SOUTHWEST.
CONFIDENCE IS HIGH IN LOW STRATUS DECK TO START DAY...BUT LOWER IN
HOW LONG IT WILL TAKE TO ERODE...WHICH COULD IMPACT TEMPS IN SPOTS.

TUESDAY NIGHT THROUGH SUNDAY...

ATTENTION TURNS TO DEEP UPPER TROUGH OVER NORTHWESTERN CONUS THAT
WILL BRING AN ACTIVE PERIOD WEDNESDAY NIGHT THROUGH THURSDAY NIGHT
AFTER OUR LONG DRY STRETCH. DRY AND COOL TUESDAY NIGHT WITH HIGH
PRESSURE RIDGING OVER AREA WILL BE FOLLOWED BY A QUICK RECOVERY ON
WEDS IN WAA PATTERN WITH H85 TEMPS WARMING BACK TO MID TEENS
CELSIUS. CLOUDS WILL INCREASE FROM WEST...AND SOME SHOWER ACTIVITY
COULD SNEAK INTO FAR NW DURING AFTERNOON. MUCH BETTER CHANCE FOR
SHRA WEDNESDAY NIGHT AS LOW LEVEL JET RAMPS UP THOUGH INSTABILITY
LOOKS TO BE MINIMAL LIMITING THREAT FOR WIDESPREAD TSRA.

MAINTAINED LIKELY POPS ON THURSDAY...THOUGH THERE IS A DIFFERENCE IN
TIMING AND EVOLUTION OF SFC LOW EXPECTED TO DEVELOP OVER THE REGION
ON OPERATIONAL AND ENSEMBLE GUIDANCE...WITH GFS A STRONG OUTLIER.
THIS WILL LIKELY PLAY ROLE IN OVERALL INTENSITY OF SHRA/TSRA. COLD
FRONT WILL BE EAST OF CWA BY EARLY FRIDAY...THOUGH UPPER TROUGH AND
MUCH COOLER AIR MASS OVER AREA COULD TOUCH OFF SHRA DUE TO STEEP
LAPSE RATES. HAVE A DRY FORECAST FOR NOW ON SATURDAY...THOUGH SOME
GUIDANCE AT THAT RANGE INDICATING POTENTIAL FOR SHRA BEFORE SFC
RIDGE BUILDS OVERHEAD SATURDAY NIGHT. TEMPERATURES EXPECTED TO BE
NEAR TO BELOW SEASONABLE ON FRIDAY IN 60S...BUT THEN COOLER THAN
NORMAL ON SATURDAY WITH SOME AREAS POSSIBLY NOT GETTING OUT OF THE
50S. IF SKIES ARE CLEAR ON SATURDAY NIGHT...COOLNESS OF AIR MASS
COULD PRESENT POTENTIAL FOR FIRST FREEZE OF SEASON IN PARTS OF
CWA...RECOVERING TO SEASONABLE HIGHS ON SUNDAY.

RC

&&

.AVIATION...

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

* LIGHT EAST TO NORTHEAST WINDS AT 8KT OR LESS.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KREIN

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN

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

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/EARLY TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281936
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
236 PM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT EAST TO NORTHEAST WINDS AT 8KT OR LESS.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KREIN

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN

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

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/EARLY TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281916
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
216 PM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT EAST TO NORTHEAST WINDS AT 7KT OR LESS.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KREIN

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN

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

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/EARLY TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
213 PM CDT

QUIET WEATHER WILL CONTINUE OVER LAKE MICHIGAN REST OF TODAY INTO
EARLY MONDAY UNDER HIGH PRESSURE...HOWEVER A COLD FRONT WILL START
TO PUSH SOUTH ACROSS THE LAKE MONDAY WITH WINDS TURNING NORTHERLY
AND FRESHENING UP INTO THE 15 TO 25 KT RANGE. A SMALL CRAFT
ADVISORY WILL EVENTUALLY BE NEEDED FOR THE INDIANA AND ILLINOIS
NEARSHORE WATERS FOR MONDAY NIGHT THROUGH TUESDAY EVENING. WINDS
TURN BACK SOUTHEAST TUESDAY NIGHT AS A WARM FRONT LIFTS BACK
ACROSS LAKE MICHIGAN. BY THURSDAY LOW PRESSURE IS PROGGED TO LIFT
NORTH ACROSS THE UPPER MIDWEST INTO CANADA WHILE DEEPENING...
THOUGH THERE ARE SIGNIFICANT DIFFERENCES BETWEEN MODELS REGARDING
THE TRACK AND STRENGTH OF THIS LOW. THE GFS PAINTS THE WORST
CONDITIONS OVER THE LAKE AND SUGGESTS THE POSSIBILITY OF STRONG
GALES FOR A COUPLE PERIODS BETWEEN THURSDAY NIGHT THROUGH EARLY
SATURDAY. THE GFS FOR NOW THOUGH IS A BIT OF AN OUTLIER SO WILL
REMAIN CONSERVATIVE NOW WITH RESPECT TO THE WIND SPEED FORECAST
LATE IN THE WEEK THOUGH GALES DO APPEAR TO BE A DISTINCT
POSSIBILITY.

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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 281748
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1248 PM CDT Sun Sep 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT SUN SEP 28 2014

Forecast generally looks on track today and just slight modifications
with sky cover today. A fair amount of sunshine expected again
today with patches of mid/high clouds and few cumulus clouds this
afternoon mainly from I-55 west and over the Wabash river valley.
Warm highs in the low to mid 80s today and Monday with light winds.

Patchy fog along the Wabash and IL rivers dissipated by 830 am
leaving sunny to mostly sunny skies by mid/late morning. 1023 mb
high pressure over lower MI and ridging westward into WI and central
and eastern IA and northern IL will remain over the Great Lakes
through monday and maintain fair wx with warm days. Dewpoints
currently in the mid 50s to near 60F will slip a few degrees this
afternoon so humidity levels will be fairly low again this afternoon.
Temps currently in the low to mid 70s (except 68F at Lacon which
had valley fog earlier this morning) will climb another 10 degrees
into the low to mid 80s by mid afternoon. Weak 580 dm 500 mb low
over far western IA near Nebraska border drift se into MO by
sunset and keep its isolated convection west of IL. RAP/NAM curule
shows few cumulus clouds this afternoon from I-55 west and over
the Wabash river valley in southeast IL. Some patches of mid/high
clouds drift over IL today but still a mostly sunny day expected.

&&

.SHORT TERM...(Today)
ISSUED AT 250 AM CDT SUN SEP 28 2014

A shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to linger near river valleys early this
morning (IL and Wabash rivers). Any fog should dissipate by 830
am.

The 580dm 500mb low centered over NW Iowa will become an open wave
and drift southeast across IL later today. That will bring scattered
cirrus clouds with it, but sunshine should generally prevail across
IL today. That will help high temps climb above all guidance numbers
again today, as the dry low levels warm quickly. Temps should top
out in the low to mid 80s this afternoon. Winds will remain light
under a weak surface pressure gradient, with east to southeast winds
of 5 to 8 mph again today.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 250 AM CDT SUN SEP 28 2014

Quiet weather expected for the start of the work week. Shortwave
currently entering western Saskatchewan will be digging as it
approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will drive a cold front southward, but general
model consensus only brings it into northern Illinois before
beginning to lift back north. The 850 mb temperatures in the
11-13C range will keep our highs above normal, with some modest
cooling on Tuesday as the front approaches. Have favored the
warmer MAV MOS guidance during this period.

Large upper low currently spinning over western Nevada still
expected to swing northeast and weaken early this week, with a small
closed low lifting through the Dakotas on Tuesday. This will help
draw the previously mentioned front back north, before a stronger
cold front moves in from the northwest. Still looks like Wednesday
will largely be dry, before showers increase Wednesday night ahead
of the front. Shear profiles increase nicely as the front gets
closer on Thursday, with 0-6km bulk shear progged to reach 40-50
knots across much of the CWA Thursday afternoon per the ECMWF model,
while the GFS is on the lower end of that range. Will need to
continue watching the threat for some stronger storms Thursday
afternoon and evening. Highest PoPs will be during the evening
hours, with a quick decrease in rain from west to east after
midnight following the passage of the front itself.

Strong surge of cooler air to plunge into the Midwest on Friday in
the wake of the front. Some model discrepancies exist at this range,
as the GFS was more prominent on driving a surface low northeast
along the front and amplifying as a significant upper low drops into
Wisconsin. The ECMWF is continues with a smaller but strong open
wave that races through the region on Friday. Both keep the coolest
air to our north, but the GFS would be more of a threat with
lingering wraparound showers. For PoPs, have continued to mention
them in the 30 to 40% range, but currently think this would
mainly be early in the morning. Temperature-wise, the GFS brings
the 850 mb zero isotherm into central Illinois by late Friday and
dipping below zero by early Saturday, while the ECMWF is already
spreading warmer air back in by that point. With this discrepancy,
the GFS would indicate highs only in the 50s on Saturday, while
the ECMWF favors mid to upper 60s. Have favored more of a blend
with Saturday as the coolest day, with highs mostly 60 to 65 degrees.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1245 PM CDT SUN SEP 28 2014

Used persistance for the central IL aviation forecast next 24 hours
through 18Z/Mon. Few to scattered cumulus clouds 5-7k ft this
afternoon especially from I-55 west, will dissipate by sunset at
2345Z. Otherwise patches of high clouds to occur next 24 hours
while few-scattered cumulus clouds reappear after 16Z Mon especially
from I-55 west again. Light and variable winds to prevail through
early Mon morning and then have nnw winds 3-5 kts after 16Z Monday.
1022 mb high pressure over lower MI and ridging westward into WI,
northern IL and eastern IA to remain near central IL through
Monday. This to continue fair weather through Monday as upper
level ridge extends from Texas up to IL. Patchy shallow ground fog
possible from 09-13Z along IL river at PIA where vsbys could lower
to MVFR of 5 miles.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07








000
FXUS63 KILX 281748
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1248 PM CDT Sun Sep 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT SUN SEP 28 2014

Forecast generally looks on track today and just slight modifications
with sky cover today. A fair amount of sunshine expected again
today with patches of mid/high clouds and few cumulus clouds this
afternoon mainly from I-55 west and over the Wabash river valley.
Warm highs in the low to mid 80s today and Monday with light winds.

Patchy fog along the Wabash and IL rivers dissipated by 830 am
leaving sunny to mostly sunny skies by mid/late morning. 1023 mb
high pressure over lower MI and ridging westward into WI and central
and eastern IA and northern IL will remain over the Great Lakes
through monday and maintain fair wx with warm days. Dewpoints
currently in the mid 50s to near 60F will slip a few degrees this
afternoon so humidity levels will be fairly low again this afternoon.
Temps currently in the low to mid 70s (except 68F at Lacon which
had valley fog earlier this morning) will climb another 10 degrees
into the low to mid 80s by mid afternoon. Weak 580 dm 500 mb low
over far western IA near Nebraska border drift se into MO by
sunset and keep its isolated convection west of IL. RAP/NAM curule
shows few cumulus clouds this afternoon from I-55 west and over
the Wabash river valley in southeast IL. Some patches of mid/high
clouds drift over IL today but still a mostly sunny day expected.

&&

.SHORT TERM...(Today)
ISSUED AT 250 AM CDT SUN SEP 28 2014

A shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to linger near river valleys early this
morning (IL and Wabash rivers). Any fog should dissipate by 830
am.

The 580dm 500mb low centered over NW Iowa will become an open wave
and drift southeast across IL later today. That will bring scattered
cirrus clouds with it, but sunshine should generally prevail across
IL today. That will help high temps climb above all guidance numbers
again today, as the dry low levels warm quickly. Temps should top
out in the low to mid 80s this afternoon. Winds will remain light
under a weak surface pressure gradient, with east to southeast winds
of 5 to 8 mph again today.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 250 AM CDT SUN SEP 28 2014

Quiet weather expected for the start of the work week. Shortwave
currently entering western Saskatchewan will be digging as it
approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will drive a cold front southward, but general
model consensus only brings it into northern Illinois before
beginning to lift back north. The 850 mb temperatures in the
11-13C range will keep our highs above normal, with some modest
cooling on Tuesday as the front approaches. Have favored the
warmer MAV MOS guidance during this period.

Large upper low currently spinning over western Nevada still
expected to swing northeast and weaken early this week, with a small
closed low lifting through the Dakotas on Tuesday. This will help
draw the previously mentioned front back north, before a stronger
cold front moves in from the northwest. Still looks like Wednesday
will largely be dry, before showers increase Wednesday night ahead
of the front. Shear profiles increase nicely as the front gets
closer on Thursday, with 0-6km bulk shear progged to reach 40-50
knots across much of the CWA Thursday afternoon per the ECMWF model,
while the GFS is on the lower end of that range. Will need to
continue watching the threat for some stronger storms Thursday
afternoon and evening. Highest PoPs will be during the evening
hours, with a quick decrease in rain from west to east after
midnight following the passage of the front itself.

Strong surge of cooler air to plunge into the Midwest on Friday in
the wake of the front. Some model discrepancies exist at this range,
as the GFS was more prominent on driving a surface low northeast
along the front and amplifying as a significant upper low drops into
Wisconsin. The ECMWF is continues with a smaller but strong open
wave that races through the region on Friday. Both keep the coolest
air to our north, but the GFS would be more of a threat with
lingering wraparound showers. For PoPs, have continued to mention
them in the 30 to 40% range, but currently think this would
mainly be early in the morning. Temperature-wise, the GFS brings
the 850 mb zero isotherm into central Illinois by late Friday and
dipping below zero by early Saturday, while the ECMWF is already
spreading warmer air back in by that point. With this discrepancy,
the GFS would indicate highs only in the 50s on Saturday, while
the ECMWF favors mid to upper 60s. Have favored more of a blend
with Saturday as the coolest day, with highs mostly 60 to 65 degrees.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1245 PM CDT SUN SEP 28 2014

Used persistance for the central IL aviation forecast next 24 hours
through 18Z/Mon. Few to scattered cumulus clouds 5-7k ft this
afternoon especially from I-55 west, will dissipate by sunset at
2345Z. Otherwise patches of high clouds to occur next 24 hours
while few-scattered cumulus clouds reappear after 16Z Mon especially
from I-55 west again. Light and variable winds to prevail through
early Mon morning and then have nnw winds 3-5 kts after 16Z Monday.
1022 mb high pressure over lower MI and ridging westward into WI,
northern IL and eastern IA to remain near central IL through
Monday. This to continue fair weather through Monday as upper
level ridge extends from Texas up to IL. Patchy shallow ground fog
possible from 09-13Z along IL river at PIA where vsbys could lower
to MVFR of 5 miles.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07








000
FXUS63 KILX 281748
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1248 PM CDT Sun Sep 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT SUN SEP 28 2014

Forecast generally looks on track today and just slight modifications
with sky cover today. A fair amount of sunshine expected again
today with patches of mid/high clouds and few cumulus clouds this
afternoon mainly from I-55 west and over the Wabash river valley.
Warm highs in the low to mid 80s today and Monday with light winds.

Patchy fog along the Wabash and IL rivers dissipated by 830 am
leaving sunny to mostly sunny skies by mid/late morning. 1023 mb
high pressure over lower MI and ridging westward into WI and central
and eastern IA and northern IL will remain over the Great Lakes
through monday and maintain fair wx with warm days. Dewpoints
currently in the mid 50s to near 60F will slip a few degrees this
afternoon so humidity levels will be fairly low again this afternoon.
Temps currently in the low to mid 70s (except 68F at Lacon which
had valley fog earlier this morning) will climb another 10 degrees
into the low to mid 80s by mid afternoon. Weak 580 dm 500 mb low
over far western IA near Nebraska border drift se into MO by
sunset and keep its isolated convection west of IL. RAP/NAM curule
shows few cumulus clouds this afternoon from I-55 west and over
the Wabash river valley in southeast IL. Some patches of mid/high
clouds drift over IL today but still a mostly sunny day expected.

&&

.SHORT TERM...(Today)
ISSUED AT 250 AM CDT SUN SEP 28 2014

A shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to linger near river valleys early this
morning (IL and Wabash rivers). Any fog should dissipate by 830
am.

The 580dm 500mb low centered over NW Iowa will become an open wave
and drift southeast across IL later today. That will bring scattered
cirrus clouds with it, but sunshine should generally prevail across
IL today. That will help high temps climb above all guidance numbers
again today, as the dry low levels warm quickly. Temps should top
out in the low to mid 80s this afternoon. Winds will remain light
under a weak surface pressure gradient, with east to southeast winds
of 5 to 8 mph again today.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 250 AM CDT SUN SEP 28 2014

Quiet weather expected for the start of the work week. Shortwave
currently entering western Saskatchewan will be digging as it
approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will drive a cold front southward, but general
model consensus only brings it into northern Illinois before
beginning to lift back north. The 850 mb temperatures in the
11-13C range will keep our highs above normal, with some modest
cooling on Tuesday as the front approaches. Have favored the
warmer MAV MOS guidance during this period.

Large upper low currently spinning over western Nevada still
expected to swing northeast and weaken early this week, with a small
closed low lifting through the Dakotas on Tuesday. This will help
draw the previously mentioned front back north, before a stronger
cold front moves in from the northwest. Still looks like Wednesday
will largely be dry, before showers increase Wednesday night ahead
of the front. Shear profiles increase nicely as the front gets
closer on Thursday, with 0-6km bulk shear progged to reach 40-50
knots across much of the CWA Thursday afternoon per the ECMWF model,
while the GFS is on the lower end of that range. Will need to
continue watching the threat for some stronger storms Thursday
afternoon and evening. Highest PoPs will be during the evening
hours, with a quick decrease in rain from west to east after
midnight following the passage of the front itself.

Strong surge of cooler air to plunge into the Midwest on Friday in
the wake of the front. Some model discrepancies exist at this range,
as the GFS was more prominent on driving a surface low northeast
along the front and amplifying as a significant upper low drops into
Wisconsin. The ECMWF is continues with a smaller but strong open
wave that races through the region on Friday. Both keep the coolest
air to our north, but the GFS would be more of a threat with
lingering wraparound showers. For PoPs, have continued to mention
them in the 30 to 40% range, but currently think this would
mainly be early in the morning. Temperature-wise, the GFS brings
the 850 mb zero isotherm into central Illinois by late Friday and
dipping below zero by early Saturday, while the ECMWF is already
spreading warmer air back in by that point. With this discrepancy,
the GFS would indicate highs only in the 50s on Saturday, while
the ECMWF favors mid to upper 60s. Have favored more of a blend
with Saturday as the coolest day, with highs mostly 60 to 65 degrees.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1245 PM CDT SUN SEP 28 2014

Used persistance for the central IL aviation forecast next 24 hours
through 18Z/Mon. Few to scattered cumulus clouds 5-7k ft this
afternoon especially from I-55 west, will dissipate by sunset at
2345Z. Otherwise patches of high clouds to occur next 24 hours
while few-scattered cumulus clouds reappear after 16Z Mon especially
from I-55 west again. Light and variable winds to prevail through
early Mon morning and then have nnw winds 3-5 kts after 16Z Monday.
1022 mb high pressure over lower MI and ridging westward into WI,
northern IL and eastern IA to remain near central IL through
Monday. This to continue fair weather through Monday as upper
level ridge extends from Texas up to IL. Patchy shallow ground fog
possible from 09-13Z along IL river at PIA where vsbys could lower
to MVFR of 5 miles.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07








000
FXUS63 KILX 281748
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1248 PM CDT Sun Sep 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT SUN SEP 28 2014

Forecast generally looks on track today and just slight modifications
with sky cover today. A fair amount of sunshine expected again
today with patches of mid/high clouds and few cumulus clouds this
afternoon mainly from I-55 west and over the Wabash river valley.
Warm highs in the low to mid 80s today and Monday with light winds.

Patchy fog along the Wabash and IL rivers dissipated by 830 am
leaving sunny to mostly sunny skies by mid/late morning. 1023 mb
high pressure over lower MI and ridging westward into WI and central
and eastern IA and northern IL will remain over the Great Lakes
through monday and maintain fair wx with warm days. Dewpoints
currently in the mid 50s to near 60F will slip a few degrees this
afternoon so humidity levels will be fairly low again this afternoon.
Temps currently in the low to mid 70s (except 68F at Lacon which
had valley fog earlier this morning) will climb another 10 degrees
into the low to mid 80s by mid afternoon. Weak 580 dm 500 mb low
over far western IA near Nebraska border drift se into MO by
sunset and keep its isolated convection west of IL. RAP/NAM curule
shows few cumulus clouds this afternoon from I-55 west and over
the Wabash river valley in southeast IL. Some patches of mid/high
clouds drift over IL today but still a mostly sunny day expected.

&&

.SHORT TERM...(Today)
ISSUED AT 250 AM CDT SUN SEP 28 2014

A shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to linger near river valleys early this
morning (IL and Wabash rivers). Any fog should dissipate by 830
am.

The 580dm 500mb low centered over NW Iowa will become an open wave
and drift southeast across IL later today. That will bring scattered
cirrus clouds with it, but sunshine should generally prevail across
IL today. That will help high temps climb above all guidance numbers
again today, as the dry low levels warm quickly. Temps should top
out in the low to mid 80s this afternoon. Winds will remain light
under a weak surface pressure gradient, with east to southeast winds
of 5 to 8 mph again today.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 250 AM CDT SUN SEP 28 2014

Quiet weather expected for the start of the work week. Shortwave
currently entering western Saskatchewan will be digging as it
approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will drive a cold front southward, but general
model consensus only brings it into northern Illinois before
beginning to lift back north. The 850 mb temperatures in the
11-13C range will keep our highs above normal, with some modest
cooling on Tuesday as the front approaches. Have favored the
warmer MAV MOS guidance during this period.

Large upper low currently spinning over western Nevada still
expected to swing northeast and weaken early this week, with a small
closed low lifting through the Dakotas on Tuesday. This will help
draw the previously mentioned front back north, before a stronger
cold front moves in from the northwest. Still looks like Wednesday
will largely be dry, before showers increase Wednesday night ahead
of the front. Shear profiles increase nicely as the front gets
closer on Thursday, with 0-6km bulk shear progged to reach 40-50
knots across much of the CWA Thursday afternoon per the ECMWF model,
while the GFS is on the lower end of that range. Will need to
continue watching the threat for some stronger storms Thursday
afternoon and evening. Highest PoPs will be during the evening
hours, with a quick decrease in rain from west to east after
midnight following the passage of the front itself.

Strong surge of cooler air to plunge into the Midwest on Friday in
the wake of the front. Some model discrepancies exist at this range,
as the GFS was more prominent on driving a surface low northeast
along the front and amplifying as a significant upper low drops into
Wisconsin. The ECMWF is continues with a smaller but strong open
wave that races through the region on Friday. Both keep the coolest
air to our north, but the GFS would be more of a threat with
lingering wraparound showers. For PoPs, have continued to mention
them in the 30 to 40% range, but currently think this would
mainly be early in the morning. Temperature-wise, the GFS brings
the 850 mb zero isotherm into central Illinois by late Friday and
dipping below zero by early Saturday, while the ECMWF is already
spreading warmer air back in by that point. With this discrepancy,
the GFS would indicate highs only in the 50s on Saturday, while
the ECMWF favors mid to upper 60s. Have favored more of a blend
with Saturday as the coolest day, with highs mostly 60 to 65 degrees.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1245 PM CDT SUN SEP 28 2014

Used persistance for the central IL aviation forecast next 24 hours
through 18Z/Mon. Few to scattered cumulus clouds 5-7k ft this
afternoon especially from I-55 west, will dissipate by sunset at
2345Z. Otherwise patches of high clouds to occur next 24 hours
while few-scattered cumulus clouds reappear after 16Z Mon especially
from I-55 west again. Light and variable winds to prevail through
early Mon morning and then have nnw winds 3-5 kts after 16Z Monday.
1022 mb high pressure over lower MI and ridging westward into WI,
northern IL and eastern IA to remain near central IL through
Monday. This to continue fair weather through Monday as upper
level ridge extends from Texas up to IL. Patchy shallow ground fog
possible from 09-13Z along IL river at PIA where vsbys could lower
to MVFR of 5 miles.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...07








000
FXUS63 KLOT 281746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT EAST TO NORTHEAST WINDS AT 7KT OR LESS.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KREIN

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN


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

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/EARLY TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT EAST TO NORTHEAST WINDS AT 7KT OR LESS.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KREIN

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN


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

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/EARLY TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT EAST TO NORTHEAST WINDS AT 7KT OR LESS.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KREIN

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN


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

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/EARLY TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281746
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1246 PM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT EAST TO NORTHEAST WINDS AT 7KT OR LESS.

* PATCHY FOG DURG THE EARLY MORNING HOURS. IFR VIS POSSIBLE AT ORD
  AND MVFR VIS MORE LIKELY AT MDW.

KREIN

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

SFC HIGH PRESSURE REMAINS THE DOMINANT FEATURE ACROSS THE REGION.
WITH A VERY WEAK PRESSURE GRADIENT IN PLACE...LGT/VRBL WINDS
SHOULD GIVE WAY TO ELY-NELY WINDS WITH THE FORMATION OF A LAKE
BREEZE. HOWEVER...WITH LITTLE PUSH BEHIND THE LAKE BREEZE...WINDS
SHOULD REMAIN AT 7KT OR LESS. THE ONLY SKY COVER OF CONSEQUENCE IS
SOME SCT CI...WITH SHOULD DECREASE AS THE UPPER LOW OVER THE IA/MN
BORDER WEAKENS INTO AN OPEN WAVE AND LIFTS OFF TO THE EAST.
SO...SKC IS EXPECTED FOR TONIGHT WITH WINDS...ONCE
AGAIN...BECOMING CALM OR LGT/VRBL. WITH LITTLE CHANGE TO THE
AIRMASS ACROSS THE REGION...PATCHY FOG IS LIKELY AGAIN FOR THE
EARLY MORNING HOURS...WITH IFR VIS LIKELY AT ALL SITES EXCEPT
MDW...WHICH SHOULD WILL LIKELY ONLY LOWER TO MVFR VIS DUE TO URBAN
HEAT ISLAND EFFECTS. CONDITIONS WILL IMPROVE THROUGH THE MORNING
WITH DAYTIME WARMING.

KREIN


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

* MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT/EARLY TOMORROW MORNING.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 18Z...

TUESDAY...MVFR CIGS LIKELY AND IFR CIGS POSSIBLE IN THE MORNING. LAKE
BREEZE PROBABLE IN THE AFTERNOON.

WEDNESDAY...VFR. LAKE BREEZE PROBABLE IN THE AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281555
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1055 AM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT/CALM WINDS THIS MORNING BECOMING EAST-NORTHEAST 5-10 KT
  THIS AFTERNOON.

* CHANCE FOR PATCHY FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE CONTINUES TO PROVIDE CALM/LIGHT AND VARIABLE WINDS
THIS MORNING. SLIGHTLY HIGHER DEWPOINT AIR HAS ALLOWED DENSER
SHALLOW FOG TO DEVELOP WITHIN A MORE WIDESPREAD 3-6SM VSBY ACROSS
THE AREA. VSBY WILL IMPROVE WITH SUNRISE THIS MORNING THOUGH WINDS
WILL BE SLOW TO COME UP SO VSBY IMPROVEMENT MAY BE A LITTLE SLOWER
TO IMPROVE THAN TAFS INDICATE. ONCE IT DOES COME UP...VFR WILL
PREVAIL THROUGH THE EVENING WITH PERIODIC INCREASES IN CIRRUS
COVER. WINDS WILL BECOME STEADIER FROM THE EAST OR EAST-NORTHEAST
THIS AFTERNOON WITH SPEEDS IN THE 5-10 KT RANGE. CALM TO LIGHT AND
VARIABLE WINDS ARE EXPECTED AGAIN TONIGHT WITH ANOTHER ROUND OF
SHALLOW/PATCHY FOG EXPECTED.

MDB

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

TUESDAY AND WEDNESDAY...VFR. LAKE BREEZE PROBABLE EACH AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281555
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1055 AM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT/CALM WINDS THIS MORNING BECOMING EAST-NORTHEAST 5-10 KT
  THIS AFTERNOON.

* CHANCE FOR PATCHY FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE CONTINUES TO PROVIDE CALM/LIGHT AND VARIABLE WINDS
THIS MORNING. SLIGHTLY HIGHER DEWPOINT AIR HAS ALLOWED DENSER
SHALLOW FOG TO DEVELOP WITHIN A MORE WIDESPREAD 3-6SM VSBY ACROSS
THE AREA. VSBY WILL IMPROVE WITH SUNRISE THIS MORNING THOUGH WINDS
WILL BE SLOW TO COME UP SO VSBY IMPROVEMENT MAY BE A LITTLE SLOWER
TO IMPROVE THAN TAFS INDICATE. ONCE IT DOES COME UP...VFR WILL
PREVAIL THROUGH THE EVENING WITH PERIODIC INCREASES IN CIRRUS
COVER. WINDS WILL BECOME STEADIER FROM THE EAST OR EAST-NORTHEAST
THIS AFTERNOON WITH SPEEDS IN THE 5-10 KT RANGE. CALM TO LIGHT AND
VARIABLE WINDS ARE EXPECTED AGAIN TONIGHT WITH ANOTHER ROUND OF
SHALLOW/PATCHY FOG EXPECTED.

MDB

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

TUESDAY AND WEDNESDAY...VFR. LAKE BREEZE PROBABLE EACH AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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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WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281555
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1055 AM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT/CALM WINDS THIS MORNING BECOMING EAST-NORTHEAST 5-10 KT
  THIS AFTERNOON.

* CHANCE FOR PATCHY FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE CONTINUES TO PROVIDE CALM/LIGHT AND VARIABLE WINDS
THIS MORNING. SLIGHTLY HIGHER DEWPOINT AIR HAS ALLOWED DENSER
SHALLOW FOG TO DEVELOP WITHIN A MORE WIDESPREAD 3-6SM VSBY ACROSS
THE AREA. VSBY WILL IMPROVE WITH SUNRISE THIS MORNING THOUGH WINDS
WILL BE SLOW TO COME UP SO VSBY IMPROVEMENT MAY BE A LITTLE SLOWER
TO IMPROVE THAN TAFS INDICATE. ONCE IT DOES COME UP...VFR WILL
PREVAIL THROUGH THE EVENING WITH PERIODIC INCREASES IN CIRRUS
COVER. WINDS WILL BECOME STEADIER FROM THE EAST OR EAST-NORTHEAST
THIS AFTERNOON WITH SPEEDS IN THE 5-10 KT RANGE. CALM TO LIGHT AND
VARIABLE WINDS ARE EXPECTED AGAIN TONIGHT WITH ANOTHER ROUND OF
SHALLOW/PATCHY FOG EXPECTED.

MDB

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

TUESDAY AND WEDNESDAY...VFR. LAKE BREEZE PROBABLE EACH AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KLOT 281555
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1055 AM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* LIGHT/CALM WINDS THIS MORNING BECOMING EAST-NORTHEAST 5-10 KT
  THIS AFTERNOON.

* CHANCE FOR PATCHY FOG LATE TONIGHT.

KREIN

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

HIGH PRESSURE CONTINUES TO PROVIDE CALM/LIGHT AND VARIABLE WINDS
THIS MORNING. SLIGHTLY HIGHER DEWPOINT AIR HAS ALLOWED DENSER
SHALLOW FOG TO DEVELOP WITHIN A MORE WIDESPREAD 3-6SM VSBY ACROSS
THE AREA. VSBY WILL IMPROVE WITH SUNRISE THIS MORNING THOUGH WINDS
WILL BE SLOW TO COME UP SO VSBY IMPROVEMENT MAY BE A LITTLE SLOWER
TO IMPROVE THAN TAFS INDICATE. ONCE IT DOES COME UP...VFR WILL
PREVAIL THROUGH THE EVENING WITH PERIODIC INCREASES IN CIRRUS
COVER. WINDS WILL BECOME STEADIER FROM THE EAST OR EAST-NORTHEAST
THIS AFTERNOON WITH SPEEDS IN THE 5-10 KT RANGE. CALM TO LIGHT AND
VARIABLE WINDS ARE EXPECTED AGAIN TONIGHT WITH ANOTHER ROUND OF
SHALLOW/PATCHY FOG EXPECTED.

MDB

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

TUESDAY AND WEDNESDAY...VFR. LAKE BREEZE PROBABLE EACH AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





000
FXUS63 KILX 281545
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1045 AM CDT Sun Sep 28 2014

.UPDATE...
ISSUED AT 1045 AM CDT SUN SEP 28 2014

Forecast generally looks on track today and just slight modifications
with sky cover today. A fair amount of sunshine expected again
today with patches of mid/high clouds and few cumulus clouds this
afternoon mainly from I-55 west and over the Wabash river valley.
Warm highs in the low to mid 80s today and Monday with light winds.

Patchy fog along the Wabash and IL rivers dissipated by 830 am
leaving sunny to mostly sunny skies by mid/late morning. 1023 mb
high pressure over lower MI and ridging westward into WI and central
and eastern IA and northern IL will remain over the Great Lakes
through monday and maintain fair wx with warm days. Dewpoints
currently in the mid 50s to near 60F will slip a few degrees this
afternoon so humidity levels will be fairly low again this afternoon.
Temps currently in the low to mid 70s (except 68F at Lacon which
had valley fog earlier this morning) will climb another 10 degrees
into the low to mid 80s by mid afternoon. Weak 580 dm 500 mb low
over far western IA near Nebraska border drift se into MO by
sunset and keep its isolated convection west of IL. RAP/NAM curule
shows few cumulus clouds this afternoon from I-55 west and over
the Wabash river valley in southeast IL. Some patches of mid/high
clouds drift over IL today but still a mostly sunny day expected.

&&

.SHORT TERM...(Today)
ISSUED AT 250 AM CDT SUN SEP 28 2014

A shallow layer of moisture below a subsidence inversion will allow
some patchy ground fog to linger near river valleys early this
morning (IL and Wabash rivers). Any fog should dissipate by 830
am.

The 580dm 500mb low centered over NW Iowa will become an open wave
and drift southeast across IL later today. That will bring scattered
cirrus clouds with it, but sunshine should generally prevail across
IL today. That will help high temps climb above all guidance numbers
again today, as the dry low levels warm quickly. Temps should top
out in the low to mid 80s this afternoon. Winds will remain light
under a weak surface pressure gradient, with east to southeast winds
of 5 to 8 mph again today.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 250 AM CDT SUN SEP 28 2014

Quiet weather expected for the start of the work week. Shortwave
currently entering western Saskatchewan will be digging as it
approaches Lake Superior, forming a closed low over Lake Huron by
early Tuesday. This will drive a cold front southward, but general
model consensus only brings it into northern Illinois before
beginning to lift back north. 850 mb temperatures in the 11-13C
range will keep our highs above normal, with some modest cooling on
Tuesday as the front approaches. Have favored the warmer MAV MOS
guidance during this period.

Large upper low currently spinning over western Nevada still
expected to swing northeast and weaken early this week, with a small
closed low lifting through the Dakotas on Tuesday. This will help
draw the previously mentioned front back north, before a stronger
cold front moves in from the northwest. Still looks like Wednesday
will largely be dry, before showers increase Wednesday night ahead
of the front. Shear profiles increase nicely as the front gets
closer on Thursday, with 0-6km bulk shear progged to reach 40-50
knots across much of the CWA Thursday afternoon per the ECMWF model,
while the GFS is on the lower end of that range. Will need to
continue watching the threat for some stronger storms Thursday
afternoon and evening. Highest PoP`s will be during the evening
hours, with a quick decrease in rain from west to east after
midnight following the passage of the front itself.

Strong surge of cooler air to plunge into the Midwest on Friday in
the wake of the front. Some model discrepancies exist at this range,
as the GFS was more prominent on driving a surface low northeast
along the front and amplifying as a significant upper low drops into
Wisconsin. The ECMWF is continues with a smaller but strong open
wave that races through the region on Friday. Both keep the coolest
air to our north, but the GFS would be more of a threat with
lingering wraparound showers. For PoP`s, have continued to mention
them in the 30-40% range, but currently think this would mainly be
early in the morning. Temperature-wise, the GFS brings the 850 mb
zero isotherm into central Illinois by late Friday and dipping below
zero by early Saturday, while the ECMWF is already spreading warmer
air back in by that point. With this discrepancy, the GFS would
indicate highs only in the 50s on Saturday, while the ECMWF favors
mid to upper 60s. Have favored more of a blend with Saturday as the
coolest day, with highs mostly 60-65.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 637 AM CDT SUN SEP 28 2014

Fog has not developed near the terminal sites so far this
morning, and any light fog over the first hour of the TAF period
would be very brief if it develops. Overall, VFR conditions will
prevail for the balance of the forecast period. A weak upper low
passing over IL today will mainly bring an increase in high
clouds. A few cumulus may form in the 4-5k ft layer as the 12z ILX
sounding shows moisture in that layer. So any BKN ceilings would
remain VFR. Surface winds will remain light east or northeast
today and tonight with speeds of 3 to 7 kts.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Shimon
LONG TERM...Geelhart
AVIATION...Shimon





000
FXUS63 KLOT 281403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* VSBY IMPROVING TO PREVAILING VFR LATE MORNING.

* LIGHT/CALM WINDS THIS MORNING BECOMING EAST-NORTHEAST 5-10 KT
  THIS AFTERNOON.

KREIN

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

HIGH PRESSURE CONTINUES TO PROVIDE CALM/LIGHT AND VARIABLE WINDS
THIS MORNING. SLIGHTLY HIGHER DEWPOINT AIR HAS ALLOWED DENSER
SHALLOW FOG TO DEVELOP WITHIN A MORE WIDESPREAD 3-6SM VSBY ACROSS
THE AREA. VSBY WILL IMPROVE WITH SUNRISE THIS MORNING THOUGH WINDS
WILL BE SLOW TO COME UP SO VSBY IMPROVEMENT MAY BE A LITTLE SLOWER
TO IMPROVE THAN TAFS INDICATE. ONCE IT DOES COME UP...VFR WILL
PREVAIL THROUGH THE EVENING WITH PERIODIC INCREASES IN CIRRUS
COVER. WINDS WILL BECOME STEADIER FROM THE EAST OR EAST-NORTHEAST
THIS AFTERNOON WITH SPEEDS IN THE 5-10 KT RANGE. CALM TO LIGHT AND
VARIABLE WINDS ARE EXPECTED AGAIN TONIGHT WITH ANOTHER ROUND OF
SHALLOW/PATCHY FOG EXPECTED.

MDB

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

* HIGH FOR ALL FORECAST ELEMENTS.

KREIN

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

TUESDAY AND WEDNESDAY...VFR. LAKE BREEZE PROBABLE EACH AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

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

$$

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FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 281403
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 AM CDT SUN SEP 28 2014

.DISCUSSION...
327 AM CDT

RELATIVELY QUIET CONDITIONS THIS MORNING...AS EARLY MORNING FOG
HAS DEVELOPED ONCE AGAIN. THIS HAS OCCURRED EVEN AS FAIRLY DENSE
CIRRUS HAS BEEN OVERHEAD AND ACROSS MOST OF THE CWA. WITH THE
DENSE CIRRUS DEPARTING TO THE NORTH/NORTHEAST OVER THE NEXT ONE TO
TWO HOURS AND WITH LOW DEWPOINT DEPRESSIONS EXPECT THIS FOG TO
REMAIN IN PLACE THROUGH SUNRISE...WITH SOME LOCATIONS LIKELY
FALLING BELOW ONE MILE AT TIMES. DONT ANTICIPATE WIDESPREAD DENSE
FOG AT THIS TIME...BUT WILL CONTINUE TO MONITOR FOG/VIS TRENDS. AS
CLOSED UPPER LEVEL LOW IS STILL SITUATED WELL TO THE WEST OF THE
CWA...SEVERAL WAVES OF ENERGY HAVING LIFTED OVER THE REGION AND
PROVIDED THIS DENSE CIRRUS. UPSTREAM MOISTURE DOES NOT APPEAR TOO
DENSE AND WOULD EXPECT MOSTLY SUNNY CONDITIONS FOR MOST AREAS AS
THE SUN RISES THIS MORNING. THIS MIGHT CHANGE LATER THIS AFTERNOON
POSSIBLY BECOMING PARTLY CLOUDY WITH NOTHING MORE THAN CIRRUS ONCE
AGAIN...AS THIS UPPER LEVEL CENTER OPENS UP AND THEN SHIFTS EAST
THROUGH THE REGION. SIMILAR TEMPS TODAY WITH LOW 80S OVER INLAND
AREAS AND AREAS NEAR THE LAKE STILL OBSERVING COOLER CONDITIONS IN
THE LOW 70S.

ATTENTION THEN SHIFTS TO APPROACH VORT MAX DROPPING SOUTH THROUGH
THE GREAT LAKES REGION ON MONDAY...WITH ASSOCIATED SURFACE FRONT
DROPPING DOWN THE LAKE THROUGHOUT THE DAY. MOST OF MONDAY WILL
LIKELY BE MOSTLY SUNNY ACROSS THE CWA...WITH ANOTHER WARM/PLEASANT
DAY FORECAST. DID BUMP UP TEMPS ON MONDAY WITH LOW 80S EXPECTED
FOR INLAND AREAS AND ALSO INCREASED TEMPS NEAR THE LAKE...WHERE
WESTERLY FLOW COULD KEEP A LAKE BREEZE RIGHT ALONG THE SHORE.
FRONT SHOULD ARRIVE SOMETIME EARLY MONDAY EVENING...WITH TEMPS
POSSIBLY FALLING QUICKLY INTO THE REMAINING EVENING. THE CWA
SHOULD REMAIN MOSTLY DRY AS BEST FORCING STAYS TO THE
EAST/NORTHEAST MONDAY NIGHT...BUT IT IS APPEARING AS SOME OF THIS
MID/UPPER LEVEL ENERGY COULD RIDE RIGHT ALONG THE NORTHEAST THIRD
OF THE CWA. WITH THIS POSSIBILITY...DID INCLUDE A SLIGHT CHANCE
FOR SHOWERS FOR FAR NORTHEAST ILLINOIS. IF THIS TREND CONTINUES
MORE OF NORTHERN ILLINOIS COULD OBSERVE SOME RAIN MONDAY NIGHT.

COOLER AND DRY CONDITIONS WILL BRIEFLY BE OBSERVED ON TUESDAY
BEFORE ATTENTION SHIFTS TO APPROACHING LONGWAVE TROUGH OVER THE
WESTERN CONUS. TEMP/MOISTURE ADVECTION WILL OCCUR OUT AHEAD OF IT
WEDNESDAY AND THURSDAY WITH A RETURN TO SLIGHTLY WARMER
CONDITIONS...AS WELL AS THIS MOISTURE RETURN PROVIDING A BETTER
SETUP FOR THUNDERSTORMS LATE IN THE WORK WEEK.

RODRIGUEZ

&&

.AVIATION...

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

* VSBY IMPROVING TO PREVAILING VFR LATE MORNING.

* LIGHT/CALM WINDS THIS MORNING BECOMING EAST-NORTHEAST 5-10 KT
  THIS AFTERNOON.

KREIN

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

HIGH PRESSURE CONTINUES TO PROVIDE CALM/LIGHT AND VARIABLE WINDS
THIS MORNING. SLIGHTLY HIGHER DEWPOINT AIR HAS ALLOWED DENSER
SHALLOW FOG TO DEVELOP WITHIN A MORE WIDESPREAD 3-6SM VSBY ACROSS
THE AREA. VSBY WILL IMPROVE WITH SUNRISE THIS MORNING THOUGH WINDS
WILL BE SLOW TO COME UP SO VSBY IMPROVEMENT MAY BE A LITTLE SLOWER
TO IMPROVE THAN TAFS INDICATE. ONCE IT DOES COME UP...VFR WILL
PREVAIL THROUGH THE EVENING WITH PERIODIC INCREASES IN CIRRUS
COVER. WINDS WILL BECOME STEADIER FROM THE EAST OR EAST-NORTHEAST
THIS AFTERNOON WITH SPEEDS IN THE 5-10 KT RANGE. CALM TO LIGHT AND
VARIABLE WINDS ARE EXPECTED AGAIN TONIGHT WITH ANOTHER ROUND OF
SHALLOW/PATCHY FOG EXPECTED.

MDB

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

* HIGH FOR ALL FORECAST ELEMENTS.

KREIN

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

TUESDAY AND WEDNESDAY...VFR. LAKE BREEZE PROBABLE EACH AFTERNOON.

THURSDAY...TSRA LIKELY...MVFR POSSIBLE. SOUTH WINDS.

FRIDAY...CHANCE SHRA...MVFR POSSIBLE. BREEZY WEST WINDS.

SATURDAY...VFR. WEST WINDS.

&&

.MARINE...
233 AM CDT

HIGH PRESSURE ACROSS THE GREAT LAKES IS CONTINUING TO PROVIDE LIGHT
WINDS TO LAKE MICHIGAN EARLY THIS MORNING. A COOL FRONT IS STRETCHED
FROM LOW PRESSURE OVER NORTHERN QUEBEC BACK ACROSS CENTRAL ONTARIO
AND WILL PUSH SOUTHWARD REACHING FAR NORTHERN PARTS OF THE LAKE
MONDAY MORNING. THE FRONT WILL THEN PUSH SOUTHWARD THROUGH THE DAY
MONDAY SHIFTING WINDS TO THE NORTH AND BRINGING AN INCREASE IN
SPEEDS. EXPECT THAT SPEEDS OF 20-25 KT WILL OCCUR ACROSS A GOOD
PORTION OF THE LAKE BY MONDAY EVENING GRADUALLY DIMINISHING
OVERNIGHT THANKS TO STRONG HIGH PRESSURE BEHIND THE FRONT. THE
STRONGEST PORTION OF THE HIGH WILL TRACK EASTWARD BUT A RIDGE AXIS
WILL MOVE ACROSS THE LAKE TUESDAY BEFORE SHIFTING EAST. SOUTHERLY
WINDS WILL THEN SET UP INTO WEDNESDAY. THE FLOW PATTERN WILL SHIFT
AS A LARGE SCALE UPPER TROUGH MOVES EASTWARD ACROSS THE COUNTRY.
THIS WILL BRING A STRONG SFC LOW NORTHWARD ACROSS THE NORTHERN HIGH
PLAINS AND INTO CENTRAL CANADA. A TIGHT PRESSURE GRADIENT WILL SET
UP ACROSS THE LAKE BETWEEN THE LOW AND HIGH PRESSURE RIDGING TO THE
EAST SO SOUTHERLY WINDS WILL MODESTLY INCREASE THROUGH THURSDAY. THE
UPPER TROUGH BECOMES REINFORCED AS IT MOVES EAST INTO FRIDAY
PRODUCING ANOTHER STRONG SURFACE LOW. THIS LOW WILL BE FURTHER EAST
ACROSS THE SOUTHERN PLAINS AND GUIDANCE CONTINUES TO POINT TOWARDS A
TRACK CLOSE TO OR OVER LAKE MICHIGAN THURSDAY NIGHT/FRIDAY. SIGNALS
CONTINUE TO POINT TOWARDS A DEEPENING OF THE LOW AS IT MOVES THROUGH
THE REGION. THIS IS STILL A WAYS OUT THERE BUT THIS SET UP...IF THE
LOW MOVES CLOSE ENOUGH TO THE LAKE WHICH HAS YET TO BE
DETERMINED...IS PRIME FOR A PERIOD OF GALES...THOUGH THE TRACK COULD
BE SUCH THAT THERE WOULD BE A SHORTER FETCH ACROSS THE LAKE WITH A
MORE WESTERLY WIND COMPONENT BEHIND THE LOW...THOUGH IT WOULD BE
SOUTHERLY AHEAD OF IT. REGARDLESS...THE THURSDAY-FRIDAY PERIOD WILL
NEED TO BE WATCHED CLOSELY.

MDB

&&

.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/US.NATIONALWEATHERSERVICE.CHICAGO.GOV
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO





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