Home > Products > Valid Products > AFD

000
FXUS63 KLOT 191144
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
644 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. FOG
HAS ALSO DEVELOPED...WITH A FEW PATCHES OF DENSE FOG INDICATED
FROM A FEW OBS SITES. EXPECT THE DENSE FOG TO REMAIN CONFINED IN A
FEW OF THE PROTECTED AREAS SINCE THE WINDS ARE NOT COMPLETELY
CALM...THEN SHORTLY AFT SUNRISE FOG SHUD QUICKLY LIFT. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A
CRYSTAL LAKE TO KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN.
THEN AS THE DAY PROGRESSES THE SFC RIDGE AXIS WILL SLIDE
EAST...ALLOWING A TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE
WEST. GOOD MIXING WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND
20KT GUSTS BY MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* SE WINDS TURNING S AND INCREASING TO ARND 10-14KT WITH GUSTS
  DEVELOPING AND NEARING 20KT BY MIDDAY THRU THIS EVENING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO DEPART THE REGION...WHICH IS ALLOWING A
TIGHTENING GRADIENT TO SLIDE OVER NORTHERN IL/NORTHWEST IN
AIRFIELDS. THIS COMBINED WITH MINIMAL CLOUD COVER WILL ALLOW GOOD
MIXING AND LIKELY PRODUCE INCREASING WINDS. BY MIDDAY EXPECT
SUSTAINED WINDS FROM THE SOUTH TO BE NEARING 14KT WITH GUSTS UP TO
20KT. GUIDANCE SUGGESTS THAT JUST A THIN CIRRUS DECK WILL BE
FLOATING OVERHEAD THIS MORNING...POSSIBLY A SCT CIRRUS LATER THIS
AFTN/EVE. GOOD MIXING IS EXPECTED TO PERSIST THRU THIS
EVENING...WHICH SHUD HELP TO PROLONG THE GUSTS AT TAF SITES INTO
THE OVERNIGHT HOURS BUT PERHAPS COME DOWN SLIGHTLY INTO A 16-18KT
RANGE. BY DAYBREAK SAT ADDTL MOISTURE WILL BE POOLING OVER
NORTHERN IL AND PROVIDE ADDTL CLOUD COVER...BUT SHUD REMAIN VFR
CONDS. ANY PRECIP LOOKS TO HOLD OFF UNTIL AFT MID-MORNING SAT.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...THUNDERSTORMS LIKELY. POSSIBLY IFR CONDS WITH
STRONGER STORMS.

SUNDAY THROUGH THURSDAY...VFR.

BEACHLER

&&

.MARINE...
357 AM CDT

A POTENT STORM SYSTEM WILL SHIFT EASTWARD ACROSS SOUTHERN ONTARIO
AND GREAT LAKES REGION TODAY AND THROUGH SATURDAY. THIS WILL RESULT
IN A PERIOD OF SOUTHERLY GALES ACROSS THE NORTHERN 2/3RDS OF LAKE
MICHIGAN BY MID TO LATE THIS AFTERNOON THROUGH EARLY SATURDAY
MORNING. A COLD FRONT WILL SHIFT OVER THE LAKE LATE SATURDAY...WITH
WINDS SHIFTING WESTERLY IN ITS WAKE. THESE WESTERLY WINDS COULD
INCREASE SOME (TO 25 TO 30 KT) SATURDAY NIGHT INTO EARLY SUNDAY AS A
SECONDARY SURFACE LOW/TROUGH DEVELOPS OVER THE EASTERN LAKES REGION.
THIS SHOULD DROP A SECONDARY COLD FRONT...WITH MUCH COLDER
AIR...SOUTHWARD OVER LAKE MICHIGAN BY LATE SUNDAY.

CONDITIONS COULD BECOME FAVORABLE FOR WATERSPOUTS FOR A PERIOD
SUNDAY. HOWEVER...AT THIS TIME I WILL HOLD OFF ON INCLUDING THE
MENTION OF SUCH IN THE FORECAST DUE TO UNCERTAINTIES ON THE OVERALL
EXTENT. OTHERWISE...SURFACE HIGH PRESSURE SHOULD BUILD OVER SOUTHERN
SECTIONS OF THE LAKE BY MONDAY...WITH LIGHTER WESTERLY WINDS EXPECTED
DURING THIS PERIOD.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 191144
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
644 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. FOG
HAS ALSO DEVELOPED...WITH A FEW PATCHES OF DENSE FOG INDICATED
FROM A FEW OBS SITES. EXPECT THE DENSE FOG TO REMAIN CONFINED IN A
FEW OF THE PROTECTED AREAS SINCE THE WINDS ARE NOT COMPLETELY
CALM...THEN SHORTLY AFT SUNRISE FOG SHUD QUICKLY LIFT. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A
CRYSTAL LAKE TO KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN.
THEN AS THE DAY PROGRESSES THE SFC RIDGE AXIS WILL SLIDE
EAST...ALLOWING A TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE
WEST. GOOD MIXING WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND
20KT GUSTS BY MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* SE WINDS TURNING S AND INCREASING TO ARND 10-14KT WITH GUSTS
  DEVELOPING AND NEARING 20KT BY MIDDAY THRU THIS EVENING.

BEACHLER

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

HIGH PRESSURE CONTINUES TO DEPART THE REGION...WHICH IS ALLOWING A
TIGHTENING GRADIENT TO SLIDE OVER NORTHERN IL/NORTHWEST IN
AIRFIELDS. THIS COMBINED WITH MINIMAL CLOUD COVER WILL ALLOW GOOD
MIXING AND LIKELY PRODUCE INCREASING WINDS. BY MIDDAY EXPECT
SUSTAINED WINDS FROM THE SOUTH TO BE NEARING 14KT WITH GUSTS UP TO
20KT. GUIDANCE SUGGESTS THAT JUST A THIN CIRRUS DECK WILL BE
FLOATING OVERHEAD THIS MORNING...POSSIBLY A SCT CIRRUS LATER THIS
AFTN/EVE. GOOD MIXING IS EXPECTED TO PERSIST THRU THIS
EVENING...WHICH SHUD HELP TO PROLONG THE GUSTS AT TAF SITES INTO
THE OVERNIGHT HOURS BUT PERHAPS COME DOWN SLIGHTLY INTO A 16-18KT
RANGE. BY DAYBREAK SAT ADDTL MOISTURE WILL BE POOLING OVER
NORTHERN IL AND PROVIDE ADDTL CLOUD COVER...BUT SHUD REMAIN VFR
CONDS. ANY PRECIP LOOKS TO HOLD OFF UNTIL AFT MID-MORNING SAT.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY NIGHT...THUNDERSTORMS LIKELY. POSSIBLY IFR CONDS WITH
STRONGER STORMS.

SUNDAY THROUGH THURSDAY...VFR.

BEACHLER

&&

.MARINE...
357 AM CDT

A POTENT STORM SYSTEM WILL SHIFT EASTWARD ACROSS SOUTHERN ONTARIO
AND GREAT LAKES REGION TODAY AND THROUGH SATURDAY. THIS WILL RESULT
IN A PERIOD OF SOUTHERLY GALES ACROSS THE NORTHERN 2/3RDS OF LAKE
MICHIGAN BY MID TO LATE THIS AFTERNOON THROUGH EARLY SATURDAY
MORNING. A COLD FRONT WILL SHIFT OVER THE LAKE LATE SATURDAY...WITH
WINDS SHIFTING WESTERLY IN ITS WAKE. THESE WESTERLY WINDS COULD
INCREASE SOME (TO 25 TO 30 KT) SATURDAY NIGHT INTO EARLY SUNDAY AS A
SECONDARY SURFACE LOW/TROUGH DEVELOPS OVER THE EASTERN LAKES REGION.
THIS SHOULD DROP A SECONDARY COLD FRONT...WITH MUCH COLDER
AIR...SOUTHWARD OVER LAKE MICHIGAN BY LATE SUNDAY.

CONDITIONS COULD BECOME FAVORABLE FOR WATERSPOUTS FOR A PERIOD
SUNDAY. HOWEVER...AT THIS TIME I WILL HOLD OFF ON INCLUDING THE
MENTION OF SUCH IN THE FORECAST DUE TO UNCERTAINTIES ON THE OVERALL
EXTENT. OTHERWISE...SURFACE HIGH PRESSURE SHOULD BUILD OVER SOUTHERN
SECTIONS OF THE LAKE BY MONDAY...WITH LIGHTER WESTERLY WINDS EXPECTED
DURING THIS PERIOD.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190914
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
414 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. FOG
HAS ALSO DEVELOPED...WITH A FEW PATCHES OF DENSE FOG INDICATED
FROM A FEW OBS SITES. EXPECT THE DENSE FOG TO REMAIN CONFINED IN A
FEW OF THE PROTECTED AREAS SINCE THE WINDS ARE NOT COMPLETELY
CALM...THEN SHORTLY AFT SUNRISE FOG SHUD QUICKLY LIFT. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A
CRYSTAL LAKE TO KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN.
THEN AS THE DAY PROGRESSES THE SFC RIDGE AXIS WILL SLIDE
EAST...ALLOWING A TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE
WEST. GOOD MIXING WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND
20KT GUSTS BY MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* PATCHY FOG AFT 09Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
357 AM CDT

A POTENT STORM SYSTEM WILL SHIFT EASTWARD ACROSS SOUTHERN ONTARIO
AND GREAT LAKES REGION TODAY AND THROUGH SATURDAY. THIS WILL RESULT
IN A PERIOD OF SOUTHERLY GALES ACROSS THE NORTHERN 2/3RDS OF LAKE
MICHIGAN BY MID TO LATE THIS AFTERNOON THROUGH EARLY SATURDAY
MORNING. A COLD FRONT WILL SHIFT OVER THE LAKE LATE SATURDAY...WITH
WINDS SHIFTING WESTERLY IN ITS WAKE. THESE WESTERLY WINDS COULD
INCREASE SOME (TO 25 TO 30 KT) SATURDAY NIGHT INTO EARLY SUNDAY AS A
SECONDARY SURFACE LOW/TROUGH DEVELOPS OVER THE EASTERN LAKES REGION.
THIS SHOULD DROP A SECONDARY COLD FRONT...WITH MUCH COLDER
AIR...SOUTHWARD OVER LAKE MICHIGAN BY LATE SUNDAY.

CONDITIONS COULD BECOME FAVORABLE FOR WATERSPOUTS FOR A PERIOD
SUNDAY. HOWEVER...AT THIS TIME I WILL HOLD OFF ON INCLUDING THE
MENTION OF SUCH IN THE FORECAST DUE TO UNCERTAINTIES ON THE OVERALL
EXTENT. OTHERWISE...SURFACE HIGH PRESSURE SHOULD BUILD OVER SOUTHERN
SECTIONS OF THE LAKE BY MONDAY...WITH LIGHTER WESTERLY WINDS EXPECTED
DURING THIS PERIOD.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190914
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
414 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. FOG
HAS ALSO DEVELOPED...WITH A FEW PATCHES OF DENSE FOG INDICATED
FROM A FEW OBS SITES. EXPECT THE DENSE FOG TO REMAIN CONFINED IN A
FEW OF THE PROTECTED AREAS SINCE THE WINDS ARE NOT COMPLETELY
CALM...THEN SHORTLY AFT SUNRISE FOG SHUD QUICKLY LIFT. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW
50S...AND JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A
CRYSTAL LAKE TO KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN.
THEN AS THE DAY PROGRESSES THE SFC RIDGE AXIS WILL SLIDE
EAST...ALLOWING A TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE
WEST. GOOD MIXING WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND
20KT GUSTS BY MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* PATCHY FOG AFT 09Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
357 AM CDT

A POTENT STORM SYSTEM WILL SHIFT EASTWARD ACROSS SOUTHERN ONTARIO
AND GREAT LAKES REGION TODAY AND THROUGH SATURDAY. THIS WILL RESULT
IN A PERIOD OF SOUTHERLY GALES ACROSS THE NORTHERN 2/3RDS OF LAKE
MICHIGAN BY MID TO LATE THIS AFTERNOON THROUGH EARLY SATURDAY
MORNING. A COLD FRONT WILL SHIFT OVER THE LAKE LATE SATURDAY...WITH
WINDS SHIFTING WESTERLY IN ITS WAKE. THESE WESTERLY WINDS COULD
INCREASE SOME (TO 25 TO 30 KT) SATURDAY NIGHT INTO EARLY SUNDAY AS A
SECONDARY SURFACE LOW/TROUGH DEVELOPS OVER THE EASTERN LAKES REGION.
THIS SHOULD DROP A SECONDARY COLD FRONT...WITH MUCH COLDER
AIR...SOUTHWARD OVER LAKE MICHIGAN BY LATE SUNDAY.

CONDITIONS COULD BECOME FAVORABLE FOR WATERSPOUTS FOR A PERIOD
SUNDAY. HOWEVER...AT THIS TIME I WILL HOLD OFF ON INCLUDING THE
MENTION OF SUCH IN THE FORECAST DUE TO UNCERTAINTIES ON THE OVERALL
EXTENT. OTHERWISE...SURFACE HIGH PRESSURE SHOULD BUILD OVER SOUTHERN
SECTIONS OF THE LAKE BY MONDAY...WITH LIGHTER WESTERLY WINDS EXPECTED
DURING THIS PERIOD.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190858
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
358 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW 50S...AND
JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A CRYSTAL LAKE TO
KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN. THEN AS THE DAY
PROGRESSES THE SFC RIDGE AXIS WILL SLIDE EAST...ALLOWING A
TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE WEST. GOOD MIXING
WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND 20KT GUSTS BY
MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
357 AM CDT

A POTENT STORM SYSTEM WILL SHIFT EASTWARD ACROSS SOUTHERN ONTARIO
AND GREAT LAKES REGION TODAY AND THROUGH SATURDAY. THIS WILL RESULT
IN A PERIOD OF SOUTHERLY GALES ACROSS THE NORTHERN 2/3RDS OF LAKE
MICHIGAN BY MID TO LATE THIS AFTERNOON THROUGH EARLY SATURDAY
MORNING. A COLD FRONT WILL SHIFT OVER THE LAKE LATE SATURDAY...WITH
WINDS SHIFTING WESTERLY IN ITS WAKE. THESE WESTERLY WINDS COULD
INCREASE SOME (TO 25 TO 30 KT) SATURDAY NIGHT INTO EARLY SUNDAY AS A
SECONDARY SURFACE LOW/TROUGH DEVELOPS OVER THE EASTERN LAKES REGION.
THIS SHOULD DROP A SECONDARY COLD FRONT...WITH MUCH COLDER
AIR...SOUTHWARD OVER LAKE MICHIGAN BY LATE SUNDAY.

CONDITIONS COULD BECOME FAVORABLE FOR WATERSPOUTS FOR A PERIOD
SUNDAY. HOWEVER...AT THIS TIME I WILL HOLD OFF ON INCLUDING THE
MENTION OF SUCH IN THE FORECAST DUE TO UNCERTAINTIES ON THE OVERALL
EXTENT. OTHERWISE...SURFACE HIGH PRESSURE SHOULD BUILD OVER SOUTHERN
SECTIONS OF THE LAKE BY MONDAY...WITH LIGHTER WESTERLY WINDS EXPECTED
DURING THIS PERIOD.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190858
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
358 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW 50S...AND
JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A CRYSTAL LAKE TO
KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN. THEN AS THE DAY
PROGRESSES THE SFC RIDGE AXIS WILL SLIDE EAST...ALLOWING A
TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE WEST. GOOD MIXING
WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND 20KT GUSTS BY
MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
357 AM CDT

A POTENT STORM SYSTEM WILL SHIFT EASTWARD ACROSS SOUTHERN ONTARIO
AND GREAT LAKES REGION TODAY AND THROUGH SATURDAY. THIS WILL RESULT
IN A PERIOD OF SOUTHERLY GALES ACROSS THE NORTHERN 2/3RDS OF LAKE
MICHIGAN BY MID TO LATE THIS AFTERNOON THROUGH EARLY SATURDAY
MORNING. A COLD FRONT WILL SHIFT OVER THE LAKE LATE SATURDAY...WITH
WINDS SHIFTING WESTERLY IN ITS WAKE. THESE WESTERLY WINDS COULD
INCREASE SOME (TO 25 TO 30 KT) SATURDAY NIGHT INTO EARLY SUNDAY AS A
SECONDARY SURFACE LOW/TROUGH DEVELOPS OVER THE EASTERN LAKES REGION.
THIS SHOULD DROP A SECONDARY COLD FRONT...WITH MUCH COLDER
AIR...SOUTHWARD OVER LAKE MICHIGAN BY LATE SUNDAY.

CONDITIONS COULD BECOME FAVORABLE FOR WATERSPOUTS FOR A PERIOD
SUNDAY. HOWEVER...AT THIS TIME I WILL HOLD OFF ON INCLUDING THE
MENTION OF SUCH IN THE FORECAST DUE TO UNCERTAINTIES ON THE OVERALL
EXTENT. OTHERWISE...SURFACE HIGH PRESSURE SHOULD BUILD OVER SOUTHERN
SECTIONS OF THE LAKE BY MONDAY...WITH LIGHTER WESTERLY WINDS EXPECTED
DURING THIS PERIOD.

KJB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190836
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW 50S...AND
JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A CRYSTAL LAKE TO
KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN. THEN AS THE DAY
PROGRESSES THE SFC RIDGE AXIS WILL SLIDE EAST...ALLOWING A
TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE WEST. GOOD MIXING
WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND 20KT GUSTS BY
MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER


LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190836
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
336 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW 50S...AND
JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A CRYSTAL LAKE TO
KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN. THEN AS THE DAY
PROGRESSES THE SFC RIDGE AXIS WILL SLIDE EAST...ALLOWING A
TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE WEST. GOOD MIXING
WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND 20KT GUSTS BY
MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER


LONG TERM SATURDAY THROUGH THURSDAY...

THE MAIN FORECAST CONCERNS DURING THE LONG TERM PERIOD WILL BE THE
CHANCES AND TIMING OF THUNDERSTORMS SATURDAY...WITH THE POTENTIAL
FOR SOME STRONG TO SEVERE STORMS.

THE LARGER SCALE WEATHER PATTERN ACROSS THE COUNTRY IS EXPECTED TO
AMPLIFY AS AN UPPER RIDGE BUILDS ACROSS THE WESTERN CONUS. THIS
PROCESS WILL DRIVE A SIGNIFICANT DISTURBANCE/UPPER LEVEL SPEED MAX
SOUTHEASTWARD ACROSS THE UPPER MIDWEST AND GREAT LAKES BY SATURDAY
THROUGH SUNDAY. THIS SYSTEM WILL BE THE MAIN FOCUS OF INTEREST FOR
SATURDAYS WEATHER. THE UPPER LEVEL SYSTEM WILL DRIVE A SURFACE COLD
FRONT OVER THE AREA SATURDAY AFTERNOON AND EARLY EVENING. A WARM AND
MOIST AIRMASS IS EXPECTED WITHIN THE PREFRONTAL AIRMASS OVER
NORTHERN ILLINOIS SATURDAY. A CORRIDOR OF MID TO POSSIBLY UPPER 60S
DEWPOINTS SHOULD BE ADVECTED OVER THE REGION AS THE LOWER LEVEL FLOW
VEERS SOUTHWESTERLY DURING THE DAY SATURDAY. THIS COMBINED WITH
UPPER LEVEL HEIGHT FALLS...ASSOCIATED WITH THE APPROACHING
DISTURBANCE...LOOKS TO SET THE STAGE FOR THUNDERSTORMS ACROSS THE
AREA.

THE CHANCES FOR THUNDERSTORMS COULD COME AS EARLY AS LATE FRIDAY
NIGHT/EARLY SATURDAY MORNING ACROSS PORTIONS OF NORTHERN ILLINOIS.
ALTHOUGH THE MAIN FOCUS FOR CONVECTION FRIDAY NIGHT LOOKS TO REMAIN
NORTH ACROSS WI...SCATTERED THUNDERSTORM DEVELOPMENT COULD OCCUR
VERY LATE AS THE LOW LEVEL JET VEERS WESTERLY AND INDUCES BETTER LOWER
LEVEL THETA-E ADVECTION OVER THE AREA. THESE EARLY MORNING STORMS
COULD STILL POSS A MARGINALLY SEVERE THREAT...MAINLY DUE TO A SMALL
THREAT FOR HAIL...GIVEN THE DEVELOPMENT OF SOME STEEPER MID LEVEL
LAPSE RATES AROUND 7 DEGREES C/KM.

THIS EARLY MORNING CONVECTION COULD BECOME A COMPLICATING FACTOR FOR
THE SATURDAY AFTERNOON CONVECTION...AND THE OVERALL AFTERNOON SEVERE
THREAT...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS...DEPENDING ON HOW
QUICKLY THINGS BREAK UP. NEVERTHELESS...IT DOES APPEAR THAT
ADDITIONAL THUNDERSTORMS WILL LIKELY DEVELOP ACROSS AT LEAST OVER THE
SOUTHERN HALF OF MY AREA IN THE AFTERNOON AS CONTINUED UPPER
LEVEL HEIGHT FALLS AND MID LEVEL COOLING ACT TO ERODE THE CAP. DEEP
LAYER UNIDIRECTIONAL SHEAR OF 40 TO 45 KT IS FORECAST TO COINCIDE
WITH THIS CONVECTIVE ACTIVITY...WHICH CERTAINLY POINTS TO POTENTIAL
FOR SOME MORE ORGANIZED STORM STRUCTURES. AS SUCH...THE SPC IS
FORECASTING A SLIGHT RISK FOR SEVERE STORMS OVER MUCH OF THE AREA ON
SATURDAY. BRIEF HEAVY DOWNPOURS WILL ALSO LIKELY ACCOMPANY THESE
STORMS...THOUGH SIGNIFICANT FLASH FLOODING APPEARS
UNLIKELY.

TEMPERATURES ON SATURDAY AHEAD OF THE COLD FRONT STILL LOOK TO REACH
THE LOWER 80S. HOWEVER...COOLER WEATHER WILL RETURN TO THE AREA BY
SUNDAY...WITH HIGHS BACK INTO THE UPPER 60S TO NEAR 70 NORTH AND THE
LOWER TO MID 70S SOUTH. A SECONDARY COLD FRONT LOOKS TO PUSH OVER
THE AREA DURING THE DAY SUNDAY AS THE MAIN MID LEVEL VORT MAX SHIFTS
SOUTHEASTWARD OVER SOUTHERN LAKE MICHIGAN. THE COLDER AIR ALOFT
UNDER THIS UPPER TROUGH SHOULD SET UP SOME GOOD LOWER LEVEL LAPSE
RATES...WHICH COULD ALLOW FOR SOME AFTERNOON SHOWERS ACROSS PORTIONS
OF NORTHEASTERN ILLINOIS...ESPECIALLY IF THE FLOW VEERS MORE
NORTHEASTERLY OFF LAKE MICHIGAN.

SURFACE HIGH PRESSURE SETS UP OVER THE AREA FOR MONDAY THEN SHIFTS
EAST OF THE AREA ON TUESDAY. COOLER TEMPERATURES...MAINLY IN THE
UPPER 60S TO LOW 70S ARE EXPECTED BOTH DAYS...WITH CHILLY OVERNIGHT
LOWS. TEMPERATURES BEGIN TO MODERATE BACK INTO THE 70S MID TO LATE
NEXT WEEK AS THE FLOW TURNS MORE SOUTHERLY. DRY CONDITIONS ARE
EXPECTED THROUGH THIS PERIOD.

KJB

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190757
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW 50S...AND
JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A CRYSTAL LAKE TO
KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN. THEN AS THE DAY
PROGRESSES THE SFC RIDGE AXIS WILL SLIDE EAST...ALLOWING A
TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE WEST. GOOD MIXING
WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND 20KT GUSTS BY
MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

EXTENDED DISCUSSION WILL BE ISSUED SHORTLY...

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190757
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 AM CDT FRI SEP 19 2014

.DISCUSSION...
257 AM CDT

TODAY...
EARLY THIS MORNING SKIES ARE GENERALLY CLEAR ACROSS MUCH OF THE
AREA...WITH EXCEPTION OF FAR NORTHERN IL WHERE SOME THIN CIRRUS
CLOUDS CONTINUE TO SLIDE EAST. THERE WAS ALSO A NARROW AREA OF
STRATUS ALONG THE WESTERN SHORE OF LAKE MICHIGAN FROM WAUKEGAN
NORTH...BUT WITH THE WINDS TURNING EAST/SOUTHEAST THIS SHUD PREVENT
MUCH OF THIS STRATUS FROM SPREADING BACK INTO NORTHEAST IL. TEMPS
EARLY THIS MORNING HAVE BEEN ABLE TO RADIATE INTO THE LOW 50S...AND
JUST BEFORE DAYBREAK EXPECT SOME UPR 40S WEST OF A CRYSTAL LAKE TO
KANKAKEE LINE ALONG WITH PORTIONS OF NORTHWEST IN. THEN AS THE DAY
PROGRESSES THE SFC RIDGE AXIS WILL SLIDE EAST...ALLOWING A
TIGHTENING PRESSURE GRADIENT TO ARRIVE FROM THE WEST. GOOD MIXING
WILL EASILY BRING TO THE SFC UPPER TEENS TO ARND 20KT GUSTS BY
MIDDAY.

MID-LVL HEIGHTS ARE PROGGED TO INCREASE THROUGHOUT THE DAY...WHICH
SHOULD LOCK-IN ANOTHER DRY DAY WITH ABUNDANT SUNSHINE AND TEMPS
RISING TO ARND 70 TO THE LOW 70S. THE FAR WEST/SOUTH COULD SEE TEMPS
TOP OUT IN THE 73-76 DEG RANGE.

TONIGHT...GUIDANCE SUGGESTS THAT MIXING WILL PERSIST BEYOND SUNSET
THIS EVENING. SO HAVE HELD ONTO THE HIGHER GUSTS THRU THE OVERNIGHT
HOURS. WINDS WILL REMAIN SOUTHERLY AS WELL...BUT BEGIN TO TURN
SOUTHWESTERLY CLOSER TO DAYBREAK SAT. A CHANNEL OF HIGHER PWAT AIR
WILL PIVOT EAST AND BE ADVECTING WARMER AIR ACROSS THE FORECAST AREA
LATE TONIGHT. TEMPS SHUD BE ABLE TO COOL INITIALLY...BUT COULD SEE
TEMPS BEGIN TO RISE WITH INCREASING CLOUDS OVERNIGHT. MOST GUIDANCE
HAS CONTINUED TO HOLD PRECIP OUT OF THE FORECAST AREA OR JUST NORTH
INTO WISC THRU THE OVERNIGHT HOURS.

BEACHLER

EXTENDED DISCUSSION WILL BE ISSUED SHORTLY...

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190611
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
111 AM CDT FRI SEP 19 2014

.DISCUSSION...
850 PM CDT

HARDLY ANY CHANGES MADE TO TONIGHTS FORECAST. CONTINUE TO SEE
SMALL AREA OF STRATUS IN FAR SOUTHEAST WI THAT SURVIVED THROUGH
THE DAYLIGHT HOURS. THIS IS LIKELY TO EXPAND OVERNIGHT...WITH
AMDAR DATA OUT OF MKE INDICATING A SATURATED SHARP 4C INVERSION IN
PRESENTLY LIGHT WIND FLOW. THE CLOUD-BEARING WINDS DO INCREASE
OVERNIGHT AND TURN MORE SOUTHERLY...SO THIS SHOULD KEEP MUCH OF
THE STRATUS NEAR THE WI STATE LINE OR NORTH SO NOT TOO WORRIED
ABOUT ANY STICKING AROUND TOO LONG. THE BOUNDARY LAYER DOES NEAR
SATURATION LATE IN PARTS OF NORTH CENTRAL IL SO CONTINUE FOG
MENTION IN THE FORECAST THERE...BUT WITH SOME EASTERLY WIND
COMPONENT NOT EXPECTING ANYTHING OVERLY THICK/DEEP. TEMPERATURES
DID NOT DROP AS SHARPLY EARLY THIS EVE AS PAST EVES THANKS TO THE
WIND COMPONENT AND SOME INCREASE IN LOW-LEVEL MOISTURE. GOING LOWS
LOOK ON TRACK...WHICH ARE A FEW DEGREES BELOW MID-SEPTEMBER
NORMALS.

MTF

//PREV DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190611
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
111 AM CDT FRI SEP 19 2014

.DISCUSSION...
850 PM CDT

HARDLY ANY CHANGES MADE TO TONIGHTS FORECAST. CONTINUE TO SEE
SMALL AREA OF STRATUS IN FAR SOUTHEAST WI THAT SURVIVED THROUGH
THE DAYLIGHT HOURS. THIS IS LIKELY TO EXPAND OVERNIGHT...WITH
AMDAR DATA OUT OF MKE INDICATING A SATURATED SHARP 4C INVERSION IN
PRESENTLY LIGHT WIND FLOW. THE CLOUD-BEARING WINDS DO INCREASE
OVERNIGHT AND TURN MORE SOUTHERLY...SO THIS SHOULD KEEP MUCH OF
THE STRATUS NEAR THE WI STATE LINE OR NORTH SO NOT TOO WORRIED
ABOUT ANY STICKING AROUND TOO LONG. THE BOUNDARY LAYER DOES NEAR
SATURATION LATE IN PARTS OF NORTH CENTRAL IL SO CONTINUE FOG
MENTION IN THE FORECAST THERE...BUT WITH SOME EASTERLY WIND
COMPONENT NOT EXPECTING ANYTHING OVERLY THICK/DEEP. TEMPERATURES
DID NOT DROP AS SHARPLY EARLY THIS EVE AS PAST EVES THANKS TO THE
WIND COMPONENT AND SOME INCREASE IN LOW-LEVEL MOISTURE. GOING LOWS
LOOK ON TRACK...WHICH ARE A FEW DEGREES BELOW MID-SEPTEMBER
NORMALS.

MTF

//PREV DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* PATCHY FOG AFT 08Z...BUT SHUD REMAIN WEST OF ORD/MDW.

* LIGHT SE WINDS STEADILY INCREASING LATER IN THE MORNING...AND
  WINDS BECOMING SOUTHERLY. GUSTS DEVELOPING BY MIDDAY UP TO 20
  KT.

BEACHLER

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

HIGH PRESSURE CONTINUES TO PROVIDE THE MAIN INFLUENCE ON THE
WEATHER ACROSS THE AREA THIS MORNING...ALTHOUGH THIS RIDGE OF HIGH
PRESSURE WAS STEADILY DRIFTING EAST. THIS WILL ALLOW THE LIGHT
EAST/SOUTHEAST WINDS TO INCREASE AS A TIGHTENING GRADIENT
DEVELOPS. OVERNIGHT SOME PATCHY FOG WILL DEVELOP BUT SHOULD ONLY
IMPACT DPA/RFD. A FEW SMALLER AIRFIELDS IN NORTHERN IL/NORTHWEST
IN COULD SEE PATCHY DENSE FOG...BUT NOT EXPECTED TO BE A PROLONGED
OR WIDESPREAD EVENT.

WINDS WILL BECOME SOUTHERLY SHORTLY AFTER DAYBREAK...WITH SPEEDS
INCREASING TO ARND 10-12KT AND GUSTS APPROACHING 17-20KT. IT
APPEARS GOOD MIXING WILL CONTINUE THRU THE EVENING HOURS THAT
GUSTS MAY PERSIST WELL INTO THE EVENING AND PERHAPS INTO EARLY SAT
MORNING.

BEACHLER


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

BEACHLER

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT THU SEP 18 2014

.DISCUSSION...
850 PM CDT

HARDLY ANY CHANGES MADE TO TONIGHTS FORECAST. CONTINUE TO SEE
SMALL AREA OF STRATUS IN FAR SOUTHEAST WI THAT SURVIVED THROUGH
THE DAYLIGHT HOURS. THIS IS LIKELY TO EXPAND OVERNIGHT...WITH
AMDAR DATA OUT OF MKE INDICATING A SATURATED SHARP 4C INVERSION IN
PRESENTLY LIGHT WIND FLOW. THE CLOUD-BEARING WINDS DO INCREASE
OVERNIGHT AND TURN MORE SOUTHERLY...SO THIS SHOULD KEEP MUCH OF
THE STRATUS NEAR THE WI STATE LINE OR NORTH SO NOT TOO WORRIED
ABOUT ANY STICKING AROUND TOO LONG. THE BOUNDARY LAYER DOES NEAR
SATURATION LATE IN PARTS OF NORTH CENTRAL IL SO CONTINUE FOG
MENTION IN THE FORECAST THERE...BUT WITH SOME EASTERLY WIND
COMPONENT NOT EXPECTING ANYTHING OVERLY THICK/DEEP. TEMPERATURES
DID NOT DROP AS SHARPLY EARLY THIS EVE AS PAST EVES THANKS TO THE
WIND COMPONENT AND SOME INCREASE IN LOW-LEVEL MOISTURE. GOING LOWS
LOOK ON TRACK...WHICH ARE A FEW DEGREES BELOW MID-SEPTEMBER
NORMALS.

MTF

//PREV DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS THIS EVENING...BECOMING SOUTHEAST TONIGHT AND
  THEN MORE SOUTHERLY ON FRIDAY.

* FOG OVERNIGHT.

RODRIGUEZ

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

VFR CONDITIONS PREVAIL WHILE A STEADY NORTHEAST WIND PERSISTS
EARLY THIS EVENING. SPEEDS WILL DIMINISH OVER THE NEXT 1-2 HOURS
BEFORE SHIFTING MORE SOUTHEAST TONIGHT AND THEN SOUTH ON
FRIDAY...WITH GUSTS LIKELY BY MIDDAY. OVERALL QUIET FORECAST
PERIOD OUTSIDE OF FOG DEVELOPMENT TONIGHT...AND WITH A LOW CHANCE
FOR REDEVELOPING MVFR/IFR CEILINGS...MAINLY FOR DPA AND RFD. LOW
LEVELS ACROSS THESE AREAS REMAIN FAIRLY MOIST AND AM CONCERNED
THAT CEILINGS COULD DEVELOP ONCE AGAIN WITH COOLING LATER TONIGHT.
THE BULK OF ANY LOW CLOUDS WILL LIKELY STAY TO THE NORTH BUT WITH
RFD POSSIBLY OBSERVING SOME OF THESE LOWER CLOUDS.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH FOG OVERNIGHT...LOW MEDIUM
  CONFIDENCE WITH EXACT TIMING AND LOWEST VIS.

RODRIGUEZ

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT THU SEP 18 2014

.DISCUSSION...
850 PM CDT

HARDLY ANY CHANGES MADE TO TONIGHTS FORECAST. CONTINUE TO SEE
SMALL AREA OF STRATUS IN FAR SOUTHEAST WI THAT SURVIVED THROUGH
THE DAYLIGHT HOURS. THIS IS LIKELY TO EXPAND OVERNIGHT...WITH
AMDAR DATA OUT OF MKE INDICATING A SATURATED SHARP 4C INVERSION IN
PRESENTLY LIGHT WIND FLOW. THE CLOUD-BEARING WINDS DO INCREASE
OVERNIGHT AND TURN MORE SOUTHERLY...SO THIS SHOULD KEEP MUCH OF
THE STRATUS NEAR THE WI STATE LINE OR NORTH SO NOT TOO WORRIED
ABOUT ANY STICKING AROUND TOO LONG. THE BOUNDARY LAYER DOES NEAR
SATURATION LATE IN PARTS OF NORTH CENTRAL IL SO CONTINUE FOG
MENTION IN THE FORECAST THERE...BUT WITH SOME EASTERLY WIND
COMPONENT NOT EXPECTING ANYTHING OVERLY THICK/DEEP. TEMPERATURES
DID NOT DROP AS SHARPLY EARLY THIS EVE AS PAST EVES THANKS TO THE
WIND COMPONENT AND SOME INCREASE IN LOW-LEVEL MOISTURE. GOING LOWS
LOOK ON TRACK...WHICH ARE A FEW DEGREES BELOW MID-SEPTEMBER
NORMALS.

MTF

//PREV DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS THIS EVENING...BECOMING SOUTHEAST TONIGHT AND
  THEN MORE SOUTHERLY ON FRIDAY.

* FOG OVERNIGHT.

RODRIGUEZ

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

VFR CONDITIONS PREVAIL WHILE A STEADY NORTHEAST WIND PERSISTS
EARLY THIS EVENING. SPEEDS WILL DIMINISH OVER THE NEXT 1-2 HOURS
BEFORE SHIFTING MORE SOUTHEAST TONIGHT AND THEN SOUTH ON
FRIDAY...WITH GUSTS LIKELY BY MIDDAY. OVERALL QUIET FORECAST
PERIOD OUTSIDE OF FOG DEVELOPMENT TONIGHT...AND WITH A LOW CHANCE
FOR REDEVELOPING MVFR/IFR CEILINGS...MAINLY FOR DPA AND RFD. LOW
LEVELS ACROSS THESE AREAS REMAIN FAIRLY MOIST AND AM CONCERNED
THAT CEILINGS COULD DEVELOP ONCE AGAIN WITH COOLING LATER TONIGHT.
THE BULK OF ANY LOW CLOUDS WILL LIKELY STAY TO THE NORTH BUT WITH
RFD POSSIBLY OBSERVING SOME OF THESE LOWER CLOUDS.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH FOG OVERNIGHT...LOW MEDIUM
  CONFIDENCE WITH EXACT TIMING AND LOWEST VIS.

RODRIGUEZ

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190150 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
850 PM CDT THU SEP 18 2014

.DISCUSSION...
850 PM CDT

HARDLY ANY CHANGES MADE TO TONIGHTS FORECAST. CONTINUE TO SEE
SMALL AREA OF STRATUS IN FAR SOUTHEAST WI THAT SURVIVED THROUGH
THE DAYLIGHT HOURS. THIS IS LIKELY TO EXPAND OVERNIGHT...WITH
AMDAR DATA OUT OF MKE INDICATING A SATURATED SHARP 4C INVERSION IN
PRESENTLY LIGHT WIND FLOW. THE CLOUD-BEARING WINDS DO INCREASE
OVERNIGHT AND TURN MORE SOUTHERLY...SO THIS SHOULD KEEP MUCH OF
THE STRATUS NEAR THE WI STATE LINE OR NORTH SO NOT TOO WORRIED
ABOUT ANY STICKING AROUND TOO LONG. THE BOUNDARY LAYER DOES NEAR
SATURATION LATE IN PARTS OF NORTH CENTRAL IL SO CONTINUE FOG
MENTION IN THE FORECAST THERE...BUT WITH SOME EASTERLY WIND
COMPONENT NOT EXPECTING ANYTHING OVERLY THICK/DEEP. TEMPERATURES
DID NOT DROP AS SHARPLY EARLY THIS EVE AS PAST EVES THANKS TO THE
WIND COMPONENT AND SOME INCREASE IN LOW-LEVEL MOISTURE. GOING LOWS
LOOK ON TRACK...WHICH ARE A FEW DEGREES BELOW MID-SEPTEMBER
NORMALS.

MTF

&&

.PREV DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS DIMINISHING THIS EVENING...BECOMING SOUTHEAST
  TONIGHT AND THEN MORE SOUTHERLY ON FRIDAY.

* FOG OVERNIGHT.

RODRIGUEZ

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

VFR CONDITIONS PREVAIL WHILE A STEADY NORTHEAST WIND PERSISTS
EARLY THIS EVENING. SPEEDS WILL DIMINISH OVER THE NEXT 1-2 HOURS
BEFORE SHIFTING MORE SOUTHEAST TONIGHT AND THEN SOUTH ON
FRIDAY...WITH GUSTS LIKELY BY MIDDAY. OVERALL QUIET FORECAST
PERIOD OUTSIDE OF FOG DEVELOPMENT TONIGHT...AND WITH A LOW CHANCE
FOR REDEVELOPING MVFR/IFR CEILINGS...MAINLY FOR DPA AND RFD. LOW
LEVELS ACROSS THESE AREAS REMAIN FAIRLY MOIST AND AM CONCERNED
THAT CEILINGS COULD DEVELOP ONCE AGAIN WITH COOLING LATER TONIGHT.
THE BULK OF ANY LOW CLOUDS WILL LIKELY STAY TO THE NORTH BUT WITH
RFD POSSIBLY OBSERVING SOME OF THESE LOWER CLOUDS.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH FOG OVERNIGHT...LOW MEDIUM
  CONFIDENCE WITH EXACT TIMING AND LOWEST VIS.

RODRIGUEZ

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190150 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
850 PM CDT THU SEP 18 2014

.DISCUSSION...
850 PM CDT

HARDLY ANY CHANGES MADE TO TONIGHTS FORECAST. CONTINUE TO SEE
SMALL AREA OF STRATUS IN FAR SOUTHEAST WI THAT SURVIVED THROUGH
THE DAYLIGHT HOURS. THIS IS LIKELY TO EXPAND OVERNIGHT...WITH
AMDAR DATA OUT OF MKE INDICATING A SATURATED SHARP 4C INVERSION IN
PRESENTLY LIGHT WIND FLOW. THE CLOUD-BEARING WINDS DO INCREASE
OVERNIGHT AND TURN MORE SOUTHERLY...SO THIS SHOULD KEEP MUCH OF
THE STRATUS NEAR THE WI STATE LINE OR NORTH SO NOT TOO WORRIED
ABOUT ANY STICKING AROUND TOO LONG. THE BOUNDARY LAYER DOES NEAR
SATURATION LATE IN PARTS OF NORTH CENTRAL IL SO CONTINUE FOG
MENTION IN THE FORECAST THERE...BUT WITH SOME EASTERLY WIND
COMPONENT NOT EXPECTING ANYTHING OVERLY THICK/DEEP. TEMPERATURES
DID NOT DROP AS SHARPLY EARLY THIS EVE AS PAST EVES THANKS TO THE
WIND COMPONENT AND SOME INCREASE IN LOW-LEVEL MOISTURE. GOING LOWS
LOOK ON TRACK...WHICH ARE A FEW DEGREES BELOW MID-SEPTEMBER
NORMALS.

MTF

&&

.PREV DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS DIMINISHING THIS EVENING...BECOMING SOUTHEAST
  TONIGHT AND THEN MORE SOUTHERLY ON FRIDAY.

* FOG OVERNIGHT.

RODRIGUEZ

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

VFR CONDITIONS PREVAIL WHILE A STEADY NORTHEAST WIND PERSISTS
EARLY THIS EVENING. SPEEDS WILL DIMINISH OVER THE NEXT 1-2 HOURS
BEFORE SHIFTING MORE SOUTHEAST TONIGHT AND THEN SOUTH ON
FRIDAY...WITH GUSTS LIKELY BY MIDDAY. OVERALL QUIET FORECAST
PERIOD OUTSIDE OF FOG DEVELOPMENT TONIGHT...AND WITH A LOW CHANCE
FOR REDEVELOPING MVFR/IFR CEILINGS...MAINLY FOR DPA AND RFD. LOW
LEVELS ACROSS THESE AREAS REMAIN FAIRLY MOIST AND AM CONCERNED
THAT CEILINGS COULD DEVELOP ONCE AGAIN WITH COOLING LATER TONIGHT.
THE BULK OF ANY LOW CLOUDS WILL LIKELY STAY TO THE NORTH BUT WITH
RFD POSSIBLY OBSERVING SOME OF THESE LOWER CLOUDS.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH FOG OVERNIGHT...LOW MEDIUM
  CONFIDENCE WITH EXACT TIMING AND LOWEST VIS.

RODRIGUEZ

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...4 PM FRIDAY TO 4
     PM SATURDAY.

     SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM FRIDAY TO 4
     PM SATURDAY.

&&

$$

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 190008
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
708 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS DIMINISHING THIS EVENING...BECOMING SOUTHEAST
  TONIGHT AND THEN MORE SOUTHERLY ON FRIDAY.

* FOG OVERNIGHT.

RODRIGUEZ

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

VFR CONDITIONS PREVAIL WHILE A STEADY NORTHEAST WIND PERSISTS
EARLY THIS EVENING. SPEEDS WILL DIMINISH OVER THE NEXT 1-2 HOURS
BEFORE SHIFTING MORE SOUTHEAST TONIGHT AND THEN SOUTH ON
FRIDAY...WITH GUSTS LIKELY BY MIDDAY. OVERALL QUIET FORECAST
PERIOD OUTSIDE OF FOG DEVELOPMENT TONIGHT...AND WITH A LOW CHANCE
FOR REDEVELOPING MVFR/IFR CEILINGS...MAINLY FOR DPA AND RFD. LOW
LEVELS ACROSS THESE AREAS REMAIN FAIRLY MOIST AND AM CONCERNED
THAT CEILINGS COULD DEVELOP ONCE AGAIN WITH COOLING LATER TONIGHT.
THE BULK OF ANY LOW CLOUDS WILL LIKELY STAY TO THE NORTH BUT WITH
RFD POSSIBLY OBSERVING SOME OF THESE LOWER CLOUDS.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH FOG OVERNIGHT...LOW MEDIUM
  CONFIDENCE WITH EXACT TIMING AND LOWEST VIS.

RODRIGUEZ

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 PM FRIDAY TO 4 PM SATURDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

&&

$$

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 190008
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
708 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS DIMINISHING THIS EVENING...BECOMING SOUTHEAST
  TONIGHT AND THEN MORE SOUTHERLY ON FRIDAY.

* FOG OVERNIGHT.

RODRIGUEZ

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

VFR CONDITIONS PREVAIL WHILE A STEADY NORTHEAST WIND PERSISTS
EARLY THIS EVENING. SPEEDS WILL DIMINISH OVER THE NEXT 1-2 HOURS
BEFORE SHIFTING MORE SOUTHEAST TONIGHT AND THEN SOUTH ON
FRIDAY...WITH GUSTS LIKELY BY MIDDAY. OVERALL QUIET FORECAST
PERIOD OUTSIDE OF FOG DEVELOPMENT TONIGHT...AND WITH A LOW CHANCE
FOR REDEVELOPING MVFR/IFR CEILINGS...MAINLY FOR DPA AND RFD. LOW
LEVELS ACROSS THESE AREAS REMAIN FAIRLY MOIST AND AM CONCERNED
THAT CEILINGS COULD DEVELOP ONCE AGAIN WITH COOLING LATER TONIGHT.
THE BULK OF ANY LOW CLOUDS WILL LIKELY STAY TO THE NORTH BUT WITH
RFD POSSIBLY OBSERVING SOME OF THESE LOWER CLOUDS.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM HIGH CONFIDENCE WITH FOG OVERNIGHT...LOW MEDIUM
  CONFIDENCE WITH EXACT TIMING AND LOWEST VIS.

RODRIGUEZ

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

SATURDAY...THUNDERSTORMS LIKELY.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

WEDNESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 PM FRIDAY TO 4 PM SATURDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

&&

$$

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 182159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
459 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS AT 10 KT THROUGH 01Z THIS EVENING.
* FOG DEVELOPMENT OVERNIGHT.

DZ/RODRIGUEZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ/RODRIGUEZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 PM FRIDAY TO 4 PM SATURDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

&&

$$

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 182159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
459 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* NORTHEAST WINDS AT 10 KT THROUGH 01Z THIS EVENING.
* FOG DEVELOPMENT OVERNIGHT.

DZ/RODRIGUEZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ/RODRIGUEZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...1 PM FRIDAY TO 4 PM SATURDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ669-LMZ868-LMZ870...4 PM FRIDAY TO 10 AM SATURDAY.

&&

$$

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 181957
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.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 181957
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.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 181903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
203 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.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 181903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
203 PM CDT THU SEP 18 2014

.DISCUSSION...
203 PM CDT

FORECAST CONCERNS ON OUR WARM UP FOR FRIDAY AND SATURDAY...FOLLOWED
BY THUNDERSTORM CHANCES FOR SATURDAY AND SATURDAY EVENING.

SURFACE HIGH PRESSURE IS IN CONTROL TO OUR NORTH AND IS GRADUALLY
SHIFTING TO THE EAST THIS AFTERNOON. COLD FRONT HAS STALLED OUT OVER
THE AREA THIS AFTERNOON AND ONSHORE FLOW IS IN PLACE. STRATUS HAS BEEN
ERODING FROM THE SOUTH AS LOWER LEVEL FLOW BEGINS TO TURN MORE
SOUTHERLY...AND WE ARE LEFT WITH SOME LINGERING STRATOCUMULUS
CLOUDS THAT LOOK TO DISSIPATE AFTER SUNSET. EXPECT ANOTHER COOL
NIGHT UNDER CLEAR SKIES.

FRIDAY WILL BE A TRANSITION DAY AS THE HIGH DRIFTS TO THE EAST.
MID/UPPER LEVEL HEIGHTS INCREASE WITH ZONAL FLOW WITH ANY SHORTWAVE
ENERGY PASSING BY TO THE NORTH. LOW LEVEL SOUTHERLY FLOW WILL BOOST
TEMPS WELL INTO THE 70S WITH AN INCREASE IN HIGH CLOUDS FROM THE
WEST AND NORTH LATER IN THE DAY...THOUGH IT SHOULD BE MOSTLY SUNNY.
EXPECT AN INCREASE IN SOUTHERLY WINDS THROUGH THE DAY. FRIDAY NIGHT
TEMPERATURES WILL BE UP SOME 5-10 DEGREES WITH WARM ADVECTION STILL
IN PLACE AND CLOUD COVER DRIFTING OVERHEAD.

OUR NEXT FEATURE OF INTEREST IS AN UPPER TROUGH AXIS ALONG THE
PACIFIC COAST. THE CLOSED OFF PORTION OF THIS LOW WILL CONTINUE TO
SINK SOUTH AND CUT OFF FROM THE MAIN MID LEVEL WESTERLY FLOW.
MEANWHILE...A STRONG UPPER LEVEL JET OFF THE BRITISH COLUMBIA COAST
WILL CONTINUE TO PUSH INLAND ACROSS THE CANADIAN ROCKIES FRIDAY. LEE
SURFACE TROUGHING WILL DEVELOP EAST OF THE ROCKIES. AS THE UPPER JET
NEARS THE AREA SATURDAY...A SHARP NEUTRALLY TILTED UPPER TROUGH WILL
DEVELOP OVER THE NORTHERN PLAINS WITH THE MAIN SURFACE LOW EXPECTED
TO PASS ALONG LAKE SUPERIOR ON SATURDAY CLOSER TO THE MAIN UPPER
TROUGH AXIS.

ON SATURDAY MORNING...THERE MAY BE SOME LINGERING WARM ADVECTION
INDUCED SHOWERS AND STORMS OUT AHEAD OF THE UPPER TROUGH...BUT THE
LOW LEVEL JET FRIDAY NIGHT INTO SATURDAY MORNING IS LARGELY FOCUSED
WEST AND NORTH OF OUR AREA BEFORE VEERING OVER OUR AREA...BUT
GUIDANCE STILL SUGGESTS SOME OF THIS ACTIVITY MAY SNEAK INTO OUR
NORTHERN ZONES THEN DRIFT SOUTH BEFORE DISSIPATING THROUGH THE
MORNING.  SATURDAY LOOKS TO BE WARMER THAN NORMAL...EVEN IN SPITE OF
LINGERING MORNING CLOUD COVER. AM RELUCTANT TO CUT TEMPS GIVEN THAT
THAT LOW LEVEL AIR MASS IS CERTAINLY SUPPORTIVE OF LOW 80S...BUT
WILL NEED TO WATCH CLOUD COVER AS THERE IS SOME BUST POTENTIAL HERE. THE
BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS COMES AS COLD FRONT
EXTENDING SOUTHWEST FROM THE SURFACE LOW APPROACHES IN THE
AFTERNOON/EVENING TIME FRAME. EXPECTING A PRETTY QUICK MOVING LINE
OF STORMS ALONG THE FRONT AS IT MOVES THROUGH. BULK SHEAR VALUES GET
TO 40-45 KT...BUT QUESTIONS AROUND AVAILABLE INSTABILITY AND
MARGINAL MID LEVEL LAPSE RATES AT THIS TIME. STILL...DEWPOINTS
SHOULD BE IN THE MID TO UPPER 60S PRODUCING MIXED LAYER CAPE IN THE
700-1200 J/KG RANGE.  THIS SUGGESTS THAT THERE MAY BE SOME SEVERE
WIND GUSTS OR HAIL WITH ANY STRONGER STORMS. PW VALUES ARE 2 S.D.
ABOVE NORMAL...THUS SOME HEAVIER DOWNPOURS ARE POSSIBLE BUT TRAINING
IS NOT ANTICIPATED. WITH THE MAIN SURFACE LOW AND UPPER DYNAMICS
PASSING BY TO THE NORTH...STILL SOME CONCERNS ON COVERAGE OF
STORMS...BUT THERE IS A PRETTY STRONG SIGNAL FROM MODELS AND
ENSEMBLES WITH A PERIOD OF STORMS SATURDAY AFTERNOON INTO SATURDAY
EVENING...SOME WHICH MAY BE STRONG TO SEVERE.

THE FRONT IS QUICKLY THROUGH SATURDAY NIGHT INTO EARLY SUNDAY.THE
CORE OF THE UPPER TROUGH PASSES BY TO OUR NORTH DURING THIS TIME...THUS
ANY POST-FRONTAL SHOWERS LOOK TO REMAIN OUT OF THE AREA.  SURFACE
HIGH PRESSURE GRADUALLY BUILDS IN BEHIND THE FRONT BRINGING A RETURN
TO GENERALLY DRY AND COOLER CONDITIONS.  THE UPPER FLOW LOOKS HIGHLY
AMPLIFIED AS THE RIDGE IN THE WEST CONTINUES TO BUILD...AND A
ANOTHER STRONGER RIDGE REMAINS IN PLACE OVER THE ATLANTIC. THIS WILL
KEEP THE UPPER TROUGH AXIS IN PLACE OVER THE EASTERN THIRD OF THE
COUNTRY. THE RESULT FOR THE EARLY HALF OF THE WEEK IS AFTERNOON
CUMULUS IN THE NORTHWEST FLOW ON THE BACK SIDE OF THE UPPER
TROUGH. BY MID WEEK THE RIDGE IN THE WEST BUILDS OVERHEAD FOR DRY
AND SEASONABLY WARM CONDITIONS. KMD

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.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 181848
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
148 PM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.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 181848
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
148 PM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
148 PM CDT

THE COLD FRONT HAS PUSHED SOUTH OF THE LAKE WITH HIGH PRESSURE
EXTENDING ALONG THE WEST SHORE OF THE LAKE AND OVER WISCONSIN AND
INTO NRN IL...WHILE AN INVERTED TROUGH HAS DEVELOPED OVER THE EAST
SIDE OF THE LAKE AND WESTERN LOWER MICHIGAN. THIS HAS SET UP A
MESOLOW OVER THE SOUTH END OF THE LAKE WITH A LINE OF CONVERGENCE
CLOUD OVER THE SRN PORTION OF THE LAKE. THERE COULD BE SOME ISOLD
SHRA ALONG THE BOUNDARY...BUT OTHERWISE...CONDITIONS SHOULD REMAIN
QUIET THROUGH THE EVENING AND OVERNIGHT. AS HIGH PRESSURE PUSHES
OFF TO THE EAST AND A TROUGH OF LOW PRESSURE AND AN ASSOCIATED
COLD FRONT DEVELOP OVER THE CENTRAL PLAINS...WINDS WILL BECOME
SOUTHERLY BY FRIDAY MORNING AND STRENGTHEN AS THE PARENT LOW OF
THE COLD FRONT DEEPENS OVER HUDSON BAY. SINCE THE SOUTHERLY WINDS
WILL BRING MUCH WARMER AIR ACROSS LAKE MICHIGAN...THERE REMAINS A
QUESTION OF HOW SOON THE AIRMASS WILL MODIFY OVER THE LAKE TO THE
POINT WHERE THE STRONGER WINDS ALOFT WILL BE ABLE TO MIX DOWN TO
THE SURFACE. THE FORECAST MODELS ARE ADVERTISING WINDS IN EXCESS
OF 45KT AT ARND 1500 FT ABOVE THE SURFACE...BUT THE MARINE LAYER
SHOULD PROHIBIT THE STRONGEST WINDS FROM MIXING ALL THE WAY DOWN
TO THE SURFACE...BUT AT THIS POINT...FEEL THAT GALE FORCE WINDS
ARE POSSIBLE FOR THE NORTHERN 2/3 OF THE LAKE...WHILE THE SURFACE
LAYER OF THE SOUTHERN PORTIONS OF THE LAKE SHOULD REMAIN TOO
STABLE FOR GALE FORCE WINDS TO MIX DOWN TO THE SURFACE. SO...WILL
HOIST A GALE WATCH FOR THE PERIOD FROM FRIDAY AFTERNOON THROUGH
LATE SATURDAY MORNING AS THE PERIOD MOST LIKELY TO SEE GALES OVER
THE LAKE. WHILE GALES ARE CURRENTLY NOT ANTICIPATED FOR THE
SOUTHERN 1/3 OF THE LAKE...WINDS WILL LIKELY REACH SMALL CRAFT
ADVISORY LEVELS. WITH SOUTHERLY FLOW...WAVES SHOULD REMAIN UNDER
CRITERIA...BUT A SMALL CRAFT ADVISORY MAY BE NEEDED FOR BOTH THE
ILLINOIS AND INDIANA NEARSHORE WATERS. FOLLOWING THE FRONTAL
PASSAGE SATURDAY...WINDS SHOULD TURN NWLY FOR SATURDAY AFTERNOON
AND INTO SUNDAY...BUT THERE IS NOT A STRONG PUSH OF COLD AIR
BEHIND THE FRONT...SO ONLY EXPECT A SHORT PERIOD OF BRISK NWLY
WINDS. ANTICIPATE THAT CONDITIONS COULD BE CLOSE TO SMALL CRAFT
ADVISORY LEVELS FOR A SHORT PERIOD...ESPECIALLY FOR THE INDIANA
NEARSHORE WATERS SATURDAY NIGHT. HIGH PRESSURE WILL THEN
OVERSPREAD THE MIDWEST AND LOWER GREAT LAKES REGION WHILE LOW
PRESSURE DROPS OUT OF NORTHERN CANADA AND SOUTH OF JAMES BAY BY
MONDAY NIGHT AND THEN HIGH PRESSURE WILL QUICKLY BUILD IN BEHIND
THIS SYSTEM...SO...WINDS ACROSS THE LAKE WILL REMAIN RELATIVELY
LIGHT FROM SUNDAY THROUGH MIDWEEK.

KREIN

&&

.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 181807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
107 PM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 181807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
107 PM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WIND SPEEDS THIS AFTERNOON.
* FOG DEVELOPMENT OVERNIGHT.
DZ

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

IFR/LIFR STRATUS DECK OVER PORTIONS OF FAR NORTHEAST IL IS
THINNING AND BREAKING RESULTING IN SHALLOW CONVECTIVE CUMULUS
CLOUDS. CLOUD DECK EXPECTED TO ERODE FURTHER AS AFTERNOON SUN
HELPS TO MIX DRIER AIR TOWARD THE SURFACE. AS THIS OCCURS..WIND SPEED
MAY INCREASE AT TIMES FOR AN HOUR OR TWO.

WITH HIGH PRESSURE OVERHEAD WIND TO DECREASE RAPIDLY BY EARLY EVENING.
THE STABLE ATMOSPHERIC CONDITIONS AND RESIDUAL MOISTURE MAY LEAD
TO MVFR/IFR FOG DEVELOPMENT OVERNIGHT ESPECIALLY IN OUTLYING
AREAS.

WINDS TO GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST
TONIGHT AND SOUTH TOMORROW. DZ

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

* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN FOG DEVELOPMENT AND TIMING.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 181610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THIS MORNING.
* WIND SPEEDS TODAY.
DZ

//DISCUSSION...UPDATED 14Z...

VISIBLE SATELLITE IMAGERY INDICATES THE EAST OR BACK EDGE OF
IFR/LIFR STRATUS DECK AT THE TERMINALS.  THE SOUTHERN EDGE OF THESE
CEILINGS EXTENDS OVER MUCH OF NORTHEAST IL AND IS MOVING STEADILY TO
THE SOUTHWEST. THIS CELING DECK AND ASSOCIATED VISIBILITIES ARE
EXPECTED TO CONTINUE TO ERODE AND LIFT WITH DAYTIME HEATING.
ANOTHER AREA OF MORE CONVECTIVE YET SHALLOW CLOUDS OVER LAKE MI TO
BRING A PERIOD OF MVFR CEILINGS INLAND.

DAYTIME HEATING WILL ALSO HELP TO MIX OUT THE AIRMASS.  AS THIS
OCCURS WIND ARE EXPECTED TO INCREASE SLIGHTLY. WINDS WILL ALSO
GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST TONIGHT
AND SOUTH TOMORROW. DZ

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

* MED-HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.
* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS TODAY.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 181610
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1110 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THIS MORNING.
* WIND SPEEDS TODAY.
DZ

//DISCUSSION...UPDATED 14Z...

VISIBLE SATELLITE IMAGERY INDICATES THE EAST OR BACK EDGE OF
IFR/LIFR STRATUS DECK AT THE TERMINALS.  THE SOUTHERN EDGE OF THESE
CEILINGS EXTENDS OVER MUCH OF NORTHEAST IL AND IS MOVING STEADILY TO
THE SOUTHWEST. THIS CELING DECK AND ASSOCIATED VISIBILITIES ARE
EXPECTED TO CONTINUE TO ERODE AND LIFT WITH DAYTIME HEATING.
ANOTHER AREA OF MORE CONVECTIVE YET SHALLOW CLOUDS OVER LAKE MI TO
BRING A PERIOD OF MVFR CEILINGS INLAND.

DAYTIME HEATING WILL ALSO HELP TO MIX OUT THE AIRMASS.  AS THIS
OCCURS WIND ARE EXPECTED TO INCREASE SLIGHTLY. WINDS WILL ALSO
GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST TONIGHT
AND SOUTH TOMORROW. DZ

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

* MED-HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.
* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS TODAY.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 181427
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
927 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THIS MORNING.
* WIND SPEEDS TODAY.
DZ

//DISCUSSION...UPDATED 14Z...

VISIBLE SATELLITE IMAGERY INDICATES THE EAST OR BACK EDGE OF
IFR/LIFR STRATUS DECK AT THE TERMINALS.  THE SOUTHERN EDGE OF THESE
CEILINGS EXTENDS OVER MUCH OF NORTHEAST IL AND IS MOVING STEADILY TO
THE SOUTHWEST. THIS CELING DECK AND ASSOCIATED VISIBILITIES ARE
EXPECTED TO CONTINUE TO ERODE AND LIFT WITH DAYTIME HEATING.
ANOTHER AREA OF MORE CONVECTIVE YET SHALLOW CLOUDS OVER LAKE MI TO
BRING A PERIOD OF MVFR CEILINGS INLAND.

DAYTIME HEATING WILL ALSO HELP TO MIX OUT THE AIRMASS.  AS THIS
OCCURS WIND ARE EXPECTED TO INCREASE SLIGHTLY. WINDS WILL ALSO
GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST BY
TONIGHT AND SOUTH TOMORROW. DZ

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

* MED-HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.
* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS TODAY.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 181427
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
927 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THIS MORNING.
* WIND SPEEDS TODAY.
DZ

//DISCUSSION...UPDATED 14Z...

VISIBLE SATELLITE IMAGERY INDICATES THE EAST OR BACK EDGE OF
IFR/LIFR STRATUS DECK AT THE TERMINALS.  THE SOUTHERN EDGE OF THESE
CEILINGS EXTENDS OVER MUCH OF NORTHEAST IL AND IS MOVING STEADILY TO
THE SOUTHWEST. THIS CELING DECK AND ASSOCIATED VISIBILITIES ARE
EXPECTED TO CONTINUE TO ERODE AND LIFT WITH DAYTIME HEATING.
ANOTHER AREA OF MORE CONVECTIVE YET SHALLOW CLOUDS OVER LAKE MI TO
BRING A PERIOD OF MVFR CEILINGS INLAND.

DAYTIME HEATING WILL ALSO HELP TO MIX OUT THE AIRMASS.  AS THIS
OCCURS WIND ARE EXPECTED TO INCREASE SLIGHTLY. WINDS WILL ALSO
GRADUALLY TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST BY
TONIGHT AND SOUTH TOMORROW. DZ

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

* MED-HIGH CONFIDENCE IN MVFR CIGS THIS MORNING.
* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS TODAY.

DZ

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 181120
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
620 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* IFR CIGS THIS MORNING.
* WIND SPEEDS TODAY.

BMD

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

A COLD FRONT HAS PUSHED SOUTH ACROSS THE TERMINALS EARLY THIS
MORNING TURNING WINDS NNE/NE BEHIND AND BRINGING IN SOME LOWER
CIGS. IFR CIGS ARE EXPECTED TO LAST THROUGH MID MORNING THEN
SHOULD SCATTER OUT WITH VFR PERSISTING THROUGH THE REMAINDER OF
THE DAY. WINDS WILL INCREASE SLIGHTLY TO AROUND 10 KT THIS
AFTERNOON AS WE MIX DEEPER...AND THEN SHOULD DROP WELL BELOW BY
MID TO LATE EVENING AS WE LOSE MIXING. WINDS WILL ALSO GRADUALLY
TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST BY TONIGHT AND
SOUTH TOMORROW.

BMD


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

* HIGH CONFIDENCE IN IFR CIGS THROUGH MID MORNING AT ORD...MEDIUM-
  HIGH AT MDW.
* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS TODAY.

BMD

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 181120
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
620 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* IFR CIGS THIS MORNING.
* WIND SPEEDS TODAY.

BMD

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

A COLD FRONT HAS PUSHED SOUTH ACROSS THE TERMINALS EARLY THIS
MORNING TURNING WINDS NNE/NE BEHIND AND BRINGING IN SOME LOWER
CIGS. IFR CIGS ARE EXPECTED TO LAST THROUGH MID MORNING THEN
SHOULD SCATTER OUT WITH VFR PERSISTING THROUGH THE REMAINDER OF
THE DAY. WINDS WILL INCREASE SLIGHTLY TO AROUND 10 KT THIS
AFTERNOON AS WE MIX DEEPER...AND THEN SHOULD DROP WELL BELOW BY
MID TO LATE EVENING AS WE LOSE MIXING. WINDS WILL ALSO GRADUALLY
TURN CLOCKWISE THROUGH THE DAY BECOMING SOUTHEAST BY TONIGHT AND
SOUTH TOMORROW.

BMD


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

* HIGH CONFIDENCE IN IFR CIGS THROUGH MID MORNING AT ORD...MEDIUM-
  HIGH AT MDW.
* MEDIUM-HIGH CONFIDENCE IN WIND SPEEDS TODAY.

BMD

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

FRIDAY NIGHT...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH WEDNESDAY...VFR.

BMD

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 180905
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
405 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WINDS TURNING NORTHEAST EARLY THURSDAY MORNING...THEN INCREASING
  TO AROUND 10 KT BY EARLY AFTERNOON.
* POTENTIAL FOR MVFR CIGS BEHIND THE COLD FRONT THURSDAY MORNING.

BMD

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

QUIET WEATHER WILL BE IN PLACE MOST OF THE OVERNIGHT HOURS HOWEVER
A COLD FRONT IS MOVING SOUTH ACROSS LAKE MICHIGAN WITH WINDS
EXPECTED TO TURN NORTHEAST BY EARLY THURSDAY MORNING BEHIND THE
FRONT. SOME MODELS ARE HINTING AT THE POSSIBILITY OF POST FRONTAL
MVFR STRATUS AND CURRENTLY THERE IS IFR/MVFR CIGS IN PLACE ACROSS
NORTHERN WISCONSIN SO WILL MAINTAIN MENTION OF MVFR CIGS MID
MORNING THOUGH CONFIDENCE IS NOT PARTICULARLY HIGH. IF IT DOES
OCCUR...IT WOULD BE EXPECTED TO MIX OUT BY EARLY TO MID AFTERNOON
WITH VFR CONDITIONS PREVAILING THE REMAINDER OF THE FORECAST
PERIOD. WINDS WILL GRADUALLY VEER THROUGH THE PERIOD AS HIGH
PRESSURE BUILDS EAST ACROSS THE GREAT LAKES REGION. WINDS DURING
THE AFTERNOON ARE EXPECTED TO BE AROUND 10 KT...THEN THEY WILL
DIMINISH BACK BELOW 10 KT DURING THE EVENING AND OVERNIGHT HOURS.

BMD

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

* HIGH CONFIDENCE IN FROPA/WIND SHIFT TIMING. MEDIUM CONFIDENCE
  IN WIND SPEEDS.
* LOW-MEDIUM CONFIDENCE IN IFR/LOWER MVFR CIGS THIS MORNING.

BMD

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 180905
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
405 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WINDS TURNING NORTHEAST EARLY THURSDAY MORNING...THEN INCREASING
  TO AROUND 10 KT BY EARLY AFTERNOON.
* POTENTIAL FOR MVFR CIGS BEHIND THE COLD FRONT THURSDAY MORNING.

BMD

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

QUIET WEATHER WILL BE IN PLACE MOST OF THE OVERNIGHT HOURS HOWEVER
A COLD FRONT IS MOVING SOUTH ACROSS LAKE MICHIGAN WITH WINDS
EXPECTED TO TURN NORTHEAST BY EARLY THURSDAY MORNING BEHIND THE
FRONT. SOME MODELS ARE HINTING AT THE POSSIBILITY OF POST FRONTAL
MVFR STRATUS AND CURRENTLY THERE IS IFR/MVFR CIGS IN PLACE ACROSS
NORTHERN WISCONSIN SO WILL MAINTAIN MENTION OF MVFR CIGS MID
MORNING THOUGH CONFIDENCE IS NOT PARTICULARLY HIGH. IF IT DOES
OCCUR...IT WOULD BE EXPECTED TO MIX OUT BY EARLY TO MID AFTERNOON
WITH VFR CONDITIONS PREVAILING THE REMAINDER OF THE FORECAST
PERIOD. WINDS WILL GRADUALLY VEER THROUGH THE PERIOD AS HIGH
PRESSURE BUILDS EAST ACROSS THE GREAT LAKES REGION. WINDS DURING
THE AFTERNOON ARE EXPECTED TO BE AROUND 10 KT...THEN THEY WILL
DIMINISH BACK BELOW 10 KT DURING THE EVENING AND OVERNIGHT HOURS.

BMD

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

* HIGH CONFIDENCE IN FROPA/WIND SHIFT TIMING. MEDIUM CONFIDENCE
  IN WIND SPEEDS.
* LOW-MEDIUM CONFIDENCE IN IFR/LOWER MVFR CIGS THIS MORNING.

BMD

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 180758
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WINDS TURNING NORTHEAST EARLY THURSDAY MORNING...THEN INCREASING
  TO AROUND 10 KT BY EARLY AFTERNOON.
* POTENTIAL FOR MVFR CIGS BEHIND THE COLD FRONT THURSDAY MORNING.

BMD

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

QUIET WEATHER WILL BE IN PLACE MOST OF THE OVERNIGHT HOURS HOWEVER
A COLD FRONT IS MOVING SOUTH ACROSS LAKE MICHIGAN WITH WINDS
EXPECTED TO TURN NORTHEAST BY EARLY THURSDAY MORNING BEHIND THE
FRONT. SOME MODELS ARE HINTING AT THE POSSIBILITY OF POST FRONTAL
MVFR STRATUS AND CURRENTLY THERE IS IFR/MVFR CIGS IN PLACE ACROSS
NORTHERN WISCONSIN SO WILL MAINTAIN MENTION OF MVFR CIGS MID
MORNING THOUGH CONFIDENCE IS NOT PARTICULARLY HIGH. IF IT DOES
OCCUR...IT WOULD BE EXPECTED TO MIX OUT BY EARLY TO MID AFTERNOON
WITH VFR CONDITIONS PREVAILING THE REMAINDER OF THE FORECAST
PERIOD. WINDS WILL GRADUALLY VEER THROUGH THE PERIOD AS HIGH
PRESSURE BUILDS EAST ACROSS THE GREAT LAKES REGION. WINDS DURING
THE AFTERNOON ARE EXPECTED TO BE AROUND 10 KT...THEN THEY WILL
DIMINISH BACK BELOW 10 KT DURING THE EVENING AND OVERNIGHT HOURS.

BMD

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

* MEDIUM-HIGH CONFIDENCE IN FROPA/WIND SHIFT TIMING. MEDIUM
  CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN MVFR CIGS.

BMD

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 180758
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
258 AM CDT THU SEP 18 2014

.DISCUSSION...
258 AM CDT

FORECAST CONCERNS THIS MORNING INCLUDE CLOUD COVER AND TEMPS
TODAY...FOLLOWED BY BRIEF SURGE OF UNSEASONABLE WARMTH AND T-STORM
CHANCES LATE FRIDAY INTO SATURDAY.

COLD FRONT CURRENTLY DROPPING SOUTH ACROSS THE WESTERN GREAT LAKES
AND IS PICKING UP MOMENTUM DOWN LAKE MICHIGAN WITH THE FRONT ON THE
WESTERN SHORE ALREADY THROUGH MKE AT 07Z. FRONT WILL CONTINUE SOUTH
INTO NORTHERN AND NORTHEASTERN ILLINOIS EARLY THIS MORNING BEFORE
EVENTUALLY WASHING OUT THIS AFTERNOON. WHILE THE FRONT WILL BE
LOSING SOME OF ITS UMPH...STILL SHOULD SEE A MODEST-MODERATE
NORTHEAST WIND OFF THE LAKE RESULTING IN SUBSTANTIAL LAKE COOLING
RIGHT ALONG THE SHORE WHERE TEMPS SHOULD HOLD IN THE UPPER 50S TO
LOWER 60S THIS AFTERNOON WITH STILL MILD TEMPS IN THE 70S WELL
INLAND WEST AND SOUTH OF THE LAKE. LAKE STRATUS HAS SLOWED ITS
SOUTHWARD ADVANCE ALREADY SO NOT THINKING IT WILL MAKE IT AS FAR
SOUTH AS OUR AREA...BUT IF IT DOES SHOULD MAINLY BE INTO NE IL AND
TEND TO CLEAR OUT THIS AFTERNOON WITH SUNNY SKIES EXPECTED
ELSEWHERE.

WARM AIR ADVECTION SHOULD BEGIN TONIGHT...BUT PROBABLY NOT SOON
ENOUGH OR WITH ENOUGH GUSTO TO PREVENT ANOTHER COOL NIGHT ACROSS THE
CWA. WARM ADVECTION SHOULD REALLY BECOME PRONOUNCED FRIDAY WITH H8
TEMPS PROGGED TO WARM 6-8C FROM 12Z FRI TO 00Z SAT. FORECAST
SOUNDINGS SUGGEST SKIES SHOULD BE GENERALLY SUNNY SO BIG QUESTION IS
HOW MUCH OF THE WARMING ALOFT WILL BE REALIZED AT THE SURFACE. THE
PROGGED 18Z 850/925 TEMPS FAVOR MID-UPPER 70S WHILE 00Z TEMPS
SUGGEST 80S...FOR NOW HAVE CONSERVATIVELY MAINTAINED MID-UPPER 70S
WHICH IS GENERALLY A BIT ABOVE OBJECTIVE GUIDANCE. MODERATE
SOUTHERLY WINDS AND CONTINUED LOW LEVEL WARM AIR ADVECTION SHOULD
ALLOW FOR AN UNSEASONABLY MILD NIGHT FRIDAY SETTING THE STAGE FOR A
WARM AND POTENTIALLY VERY WARM SATURDAY. ANY LINGERING CONVECTION
AND DEBRIS CLOUDINESS LOOKS TO REMAIN NORTH OF THE AREA EARLY
SATURDAY...SO IT IS LOOKING LIKE AMPLE SUNSHINE AND STRONG SOUTHWEST
WINDS SHOULD ALLOW TEMPS TO SOAR INTO THE 80S. QUESTION IS HOW FAR
INTO THE 80S? THE FORECAST 850/925 TEMPS ACTUALLY COULD SUPPORT
MID-UPPER 80S...THOUGH GUIDANCE IS ONLY CRANKING OUT TEMPS AROUND 80
SO AM LEARY ABOUT GOING TO CRAZY WITH TEMPS PARTICULARLY WITH TIMING
OF CONVECTION AND CLOUD COVER QUESTIONABLE. MAINTAINED THE GOING
FORECAST HIGHS WHICH ARE ABOVE GUIDANCE BUT SET-UP REALLY LOOKS
FAVORABLE TO ME FOR HIGHS GETTING WELL INTO THE 80S IF CLOUDINESS
DOESNT MUCK THINGS UP.

COLD FRONT IS SLATED TO DROP SOUTHEASTWARD TOWARD THE AREA DURING
THE LATE AFTERNOON/EVENING. MODERATE INSTABILITY IS PROGGED TO
DEVELOP IN ADVANCE OF THE FRONT...THOUGH DEEPER MIXING THAT FORECAST
COULD CAUSE DEWPOINTS TO MIX OUT AND RESULT IN WEAKER INSTABILITY.
NONE THE LESS...MODEST CAPE AND MODERATE-STRONG DEEP LAYER SHEAR
SHOULD STILL SUPPORT A SEVERE THREAT WITH STORM THAT DO DEVELOP.
SYNOPTICALLY SPEAKING THIS ISNT A TYPICAL BIG SEVERE WEATHER AND
WIDESPREAD CONVECTIVE SET-UP AND COVERAGE OF STORMS MAY NOT BE AS
SIGNIFICANT AS THE LOWER RES GLOBAL MODEL QPF WOULD SUGGEST...SO
HAVE MAINTAINED ONLY LOW END LIKELY POPS AND THOSE COULD BE A BIT
OVERDONE.

STILL LOOKS LIKE A MODERATELY HEALTHY SHOT OF COLDER AIR ARRIVES
LATE SUNDAY INTO EARLY NEXT WEEK. SUNDAY THROUGH MUCH OF NEXT WEEK
LOOKS LIKE ANOTHER STRETCH OF DRY WEATHER WITH AMPLE SUNSHINE AND
MODERATING TEMPS FROM CONSIDERABLY BELOW AVERAGE MONDAY REBOUNDING
BACK CLOSER TO AND PERHAPS A BIT ABOVE AVERAGE BY MID-LATE WEEK.

IZZI

&&

.AVIATION...

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

* WINDS TURNING NORTHEAST EARLY THURSDAY MORNING...THEN INCREASING
  TO AROUND 10 KT BY EARLY AFTERNOON.
* POTENTIAL FOR MVFR CIGS BEHIND THE COLD FRONT THURSDAY MORNING.

BMD

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

QUIET WEATHER WILL BE IN PLACE MOST OF THE OVERNIGHT HOURS HOWEVER
A COLD FRONT IS MOVING SOUTH ACROSS LAKE MICHIGAN WITH WINDS
EXPECTED TO TURN NORTHEAST BY EARLY THURSDAY MORNING BEHIND THE
FRONT. SOME MODELS ARE HINTING AT THE POSSIBILITY OF POST FRONTAL
MVFR STRATUS AND CURRENTLY THERE IS IFR/MVFR CIGS IN PLACE ACROSS
NORTHERN WISCONSIN SO WILL MAINTAIN MENTION OF MVFR CIGS MID
MORNING THOUGH CONFIDENCE IS NOT PARTICULARLY HIGH. IF IT DOES
OCCUR...IT WOULD BE EXPECTED TO MIX OUT BY EARLY TO MID AFTERNOON
WITH VFR CONDITIONS PREVAILING THE REMAINDER OF THE FORECAST
PERIOD. WINDS WILL GRADUALLY VEER THROUGH THE PERIOD AS HIGH
PRESSURE BUILDS EAST ACROSS THE GREAT LAKES REGION. WINDS DURING
THE AFTERNOON ARE EXPECTED TO BE AROUND 10 KT...THEN THEY WILL
DIMINISH BACK BELOW 10 KT DURING THE EVENING AND OVERNIGHT HOURS.

BMD

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

* MEDIUM-HIGH CONFIDENCE IN FROPA/WIND SHIFT TIMING. MEDIUM
  CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN MVFR CIGS.

BMD

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
254 AM CDT

A COLD FRONT WILL CONTINUE TO SAG SOUTH ACROSS LAKE MICHIGAN TODAY
WITH WINDS TURNING NORTHEASTERLY 15 TO 25 KT IN ITS WAKE. THE
FRONT WILL WEAKEN BY THE TIME IT REACHES THE SOUTH END OF THE
LAKE ALONG WITH THE HIGHER MAGNITUDE WINDS. WINDS TURN SOUTHEAST
TONIGHT AND BEGIN TO FRESHEN UP AGAIN...INCREASING TO 30 KT BY
FRIDAY AHEAD OF THE NEXT COLD FRONT. GALES ARE POSSIBLE MAINLY
OVER THE NORTH HALF OF THE LAKE LATE FRIDAY AFTERNOON THROUGH THE
EVENING. IT IS STILL UNCERTAIN HOW WIDESPREAD OR LONG GALES WILL
LAST WITH SOMEWHAT STABLE CONDITIONS EXPECTED TO INHIBIT
MIXING...AND MODERATE DIFFERENCES BETWEEN THE MODELS MAKING THE
DETAILS A BIT MURKY THIS FAR OUT. A GALE WATCH MAY BE NEEDED AT
SOME POINT THOUGH. WINDS REMAIN BREEZY OVER THE WEEKEND AS ANOTHER
COLD FRONT DROPS ACROSS THE LAKE SATURDAY NIGHT WITH WINDS TURNING
BACK TO THE NORTHWEST BEHIND.

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 180527
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1227 AM CDT THU SEP 18 2014

.DISCUSSION...
819 PM CDT

NO BIG CHANGES TO MADE TO THE FORECAST THROUGH THURSDAY MORNING.
ANOTHER EARLY EVENING OF RAPID HEATING ESCAPE WITH OUTLYING
LOCATIONS DROPPING 10 TO AS MUCH AS 15 DEGREES IN THE PAST TWO
HOURS. LOOKING AT 24-HOUR CHANGE DOES INDICATE TEMPERATURES AND
DEW POINTS ARE AROUND 5 DEGREES HIGHER THAN LAST EVE AT THIS TIME
AT MOST LOCATIONS. DO THINK LOW TEMPERATURES WILL FALL OUT PRETTY
CLOSE TO THAT DEPARTURE FROM THIS MORNINGS LOWS. THIS IS RIGHT IN
THE NEIGHBORHOOD OF THE GOING FORECAST.

THE BACKDOOR COLD FRONT WITH AN IMPRESSIVE BAROCLINIC GRADIENT
BEHIND IT IS WORKING ITS WAY SOUTHWARD DOWN LAKE MICHIGAN. THE
PRIMARY COLD AIR ADVECTION WITH THIS WILL WEAKEN BY MORNING AND
ONLY GIVE A GLANCING SHOT TO THE AREA. WITH SOMEWHAT OF A SUBTLE
PUSH...THE DEGREE OF MORNING CLOUD COVER MAY END UP BEING LESS
THAN FORECAST OVER FAR NORTHEAST ILLINOIS AND FAR NORTHWEST
INDIANA...AND MOISTURE FORECASTS FROM LATEST GUIDANCE ARE TRENDING
LESS. WITH SATELLITE IMAGERY STILL INDICATING PLENTY OF CLOUDS
BEHIND THE FRONT UPSTREAM WILL OPT TO WAIT AT THIS TIME FOR ANY
CHANGES.

MTF

//PREV DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* WINDS TURNING NORTHEAST EARLY THURSDAY MORNING...THEN INCREASING
  TO AROUND 10 KT BY EARLY AFTERNOON.
* POTENTIAL FOR MVFR CIGS BEHIND THE COLD FRONT THURSDAY MORNING.

BMD

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

QUIET WEATHER WILL BE IN PLACE MOST OF THE OVERNIGHT HOURS HOWEVER
A COLD FRONT IS MOVING SOUTH ACROSS LAKE MICHIGAN WITH WINDS
EXPECTED TO TURN NORTHEAST BY EARLY THURSDAY MORNING BEHIND THE
FRONT. SOME MODELS ARE HINTING AT THE POSSIBILITY OF POST FRONTAL
MVFR STRATUS AND CURRENTLY THERE IS IFR/MVFR CIGS IN PLACE ACROSS
NORTHERN WISCONSIN SO WILL MAINTAIN MENTION OF MVFR CIGS MID
MORNING THOUGH CONFIDENCE IS NOT PARTICULARLY HIGH. IF IT DOES
OCCUR...IT WOULD BE EXPECTED TO MIX OUT BY EARLY TO MID AFTERNOON
WITH VFR CONDITIONS PREVAILING THE REMAINDER OF THE FORECAST
PERIOD. WINDS WILL GRADAULLY VEER THROUGH THE PERIOD AS HIGH
PRESSURE BUILDS EAST ACROSS THE GREAT LAKES REGION. WINDS DURING
THE AFTERNOON ARE EXPECTED TO BE AROUND 10 KT...THEN THEY WILL
DIMINISH BACK BELOW 10 KT DURING THE EVENING AND OVERNIGHT HOURS.

BMD


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

* MEDIUM-HIGH CONFIDENCE IN FROPA/WIND SHIFT TIMING. MEDIUM
  CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN MVFR CIGS.

BMD

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 180527
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1227 AM CDT THU SEP 18 2014

.DISCUSSION...
819 PM CDT

NO BIG CHANGES TO MADE TO THE FORECAST THROUGH THURSDAY MORNING.
ANOTHER EARLY EVENING OF RAPID HEATING ESCAPE WITH OUTLYING
LOCATIONS DROPPING 10 TO AS MUCH AS 15 DEGREES IN THE PAST TWO
HOURS. LOOKING AT 24-HOUR CHANGE DOES INDICATE TEMPERATURES AND
DEW POINTS ARE AROUND 5 DEGREES HIGHER THAN LAST EVE AT THIS TIME
AT MOST LOCATIONS. DO THINK LOW TEMPERATURES WILL FALL OUT PRETTY
CLOSE TO THAT DEPARTURE FROM THIS MORNINGS LOWS. THIS IS RIGHT IN
THE NEIGHBORHOOD OF THE GOING FORECAST.

THE BACKDOOR COLD FRONT WITH AN IMPRESSIVE BAROCLINIC GRADIENT
BEHIND IT IS WORKING ITS WAY SOUTHWARD DOWN LAKE MICHIGAN. THE
PRIMARY COLD AIR ADVECTION WITH THIS WILL WEAKEN BY MORNING AND
ONLY GIVE A GLANCING SHOT TO THE AREA. WITH SOMEWHAT OF A SUBTLE
PUSH...THE DEGREE OF MORNING CLOUD COVER MAY END UP BEING LESS
THAN FORECAST OVER FAR NORTHEAST ILLINOIS AND FAR NORTHWEST
INDIANA...AND MOISTURE FORECASTS FROM LATEST GUIDANCE ARE TRENDING
LESS. WITH SATELLITE IMAGERY STILL INDICATING PLENTY OF CLOUDS
BEHIND THE FRONT UPSTREAM WILL OPT TO WAIT AT THIS TIME FOR ANY
CHANGES.

MTF

//PREV DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* WINDS TURNING NORTHEAST EARLY THURSDAY MORNING...THEN INCREASING
  TO AROUND 10 KT BY EARLY AFTERNOON.
* POTENTIAL FOR MVFR CIGS BEHIND THE COLD FRONT THURSDAY MORNING.

BMD

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

QUIET WEATHER WILL BE IN PLACE MOST OF THE OVERNIGHT HOURS HOWEVER
A COLD FRONT IS MOVING SOUTH ACROSS LAKE MICHIGAN WITH WINDS
EXPECTED TO TURN NORTHEAST BY EARLY THURSDAY MORNING BEHIND THE
FRONT. SOME MODELS ARE HINTING AT THE POSSIBILITY OF POST FRONTAL
MVFR STRATUS AND CURRENTLY THERE IS IFR/MVFR CIGS IN PLACE ACROSS
NORTHERN WISCONSIN SO WILL MAINTAIN MENTION OF MVFR CIGS MID
MORNING THOUGH CONFIDENCE IS NOT PARTICULARLY HIGH. IF IT DOES
OCCUR...IT WOULD BE EXPECTED TO MIX OUT BY EARLY TO MID AFTERNOON
WITH VFR CONDITIONS PREVAILING THE REMAINDER OF THE FORECAST
PERIOD. WINDS WILL GRADAULLY VEER THROUGH THE PERIOD AS HIGH
PRESSURE BUILDS EAST ACROSS THE GREAT LAKES REGION. WINDS DURING
THE AFTERNOON ARE EXPECTED TO BE AROUND 10 KT...THEN THEY WILL
DIMINISH BACK BELOW 10 KT DURING THE EVENING AND OVERNIGHT HOURS.

BMD


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

* MEDIUM-HIGH CONFIDENCE IN FROPA/WIND SHIFT TIMING. MEDIUM
  CONFIDENCE IN WIND SPEEDS.
* LOW CONFIDENCE IN MVFR CIGS.

BMD

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 180314
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1014 PM CDT WED SEP 17 2014

.DISCUSSION...
819 PM CDT

NO BIG CHANGES TO MADE TO THE FORECAST THROUGH THURSDAY MORNING.
ANOTHER EARLY EVENING OF RAPID HEATING ESCAPE WITH OUTLYING
LOCATIONS DROPPING 10 TO AS MUCH AS 15 DEGREES IN THE PAST TWO
HOURS. LOOKING AT 24-HOUR CHANGE DOES INDICATE TEMPERATURES AND
DEW POINTS ARE AROUND 5 DEGREES HIGHER THAN LAST EVE AT THIS TIME
AT MOST LOCATIONS. DO THINK LOW TEMPERATURES WILL FALL OUT PRETTY
CLOSE TO THAT DEPARTURE FROM THIS MORNINGS LOWS. THIS IS RIGHT IN
THE NEIGHBORHOOD OF THE GOING FORECAST.

THE BACKDOOR COLD FRONT WITH AN IMPRESSIVE BAROCLINIC GRADIENT
BEHIND IT IS WORKING ITS WAY SOUTHWARD DOWN LAKE MICHIGAN. THE
PRIMARY COLD AIR ADVECTION WITH THIS WILL WEAKEN BY MORNING AND
ONLY GIVE A GLANCING SHOT TO THE AREA. WITH SOMEWHAT OF A SUBTLE
PUSH...THE DEGREE OF MORNING CLOUD COVER MAY END UP BEING LESS
THAN FORECAST OVER FAR NORTHEAST ILLINOIS AND FAR NORTHWEST
INDIANA...AND MOISTURE FORECASTS FROM LATEST GUIDANCE ARE TRENDING
LESS. WITH SATELLITE IMAGERY STILL INDICATING PLENTY OF CLOUDS
BEHIND THE FRONT UPSTREAM WILL OPT TO WAIT AT THIS TIME FOR ANY
CHANGES.

MTF

//PREV DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* LIGHT AND VARIABLE WINDS TONIGHT...THEN INCREASING OUT OF THE
  NORTHEAST THROUGH THURSDAY MORNING WITH FROPA...LIKELY AT 10 KT
  THROUGH THE AFTERNOON.

* MVFR STRATUS POST FROPA THURSDAY MORNING.

RODRIGUEZ

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

WITH LAKE BREEZE PASSAGE...WINDS HAVE SHIFTED TO MORE OF AN
EASTERLY DIRECTION AT 7-9 KT WHILE VFR CONDITIONS PREVAIL. CURRENT
SPEEDS ARE AT THE HIGHEST WITH SPEEDS EXPECTED TO RAPIDLY DIMINISH
OVER THE NEXT COUPLE OF HOURS. MOST OF TONIGHT WILL REMAIN QUIET
AS FRONT TO THE NORTH DROPS SOUTH TOWARDS THE TERMINALS. TIMING OF
THIS FRONT DOES APPEAR AS IF IT WILL BE SLIGHTLY SOONER EARLY
THURSDAY MORNING...SO HAVE PUSHED UP TIMING OF FROPA. HAVE LOWER
CONFIDENCE WITH CEILINGS/TRENDS THURSDAY MORNING BEHIND THE FRONT.
THERE ARE CURRENTLY MVFR CEILINGS BEHIND THE FRONT ACROSS FAR
NORTHERN LAKE MICHIGAN AND DO EXPECT THESE TO PUSH DOWN THE LAKE
WITH THE FRONT TONIGHT ALTHOUGH...GUIDANCE DOES VARY WITH THE
EXTENT OF THIS SOUTHWARD PUSH. GUIDANCE DOES TRY TO KEEP THE BULK
OF THE LOWER CLOUDS TO THE NORTHWEST AS LOW LEVEL FLOW QUICKLY
VEERS BUT WITH A STRONG NORTHERLY PUSH...CANT RULE OUT THESE LOWER
CLOUDS STILL REACHING THE TERMINALS. SO HAVE MAINTAINED MVFR
CEILINGS IN THE TAFS...BUT DID MAKE SOME MINOR CHANGES TO
HEIGHT/DURATION. DONT THINK CEILINGS SHOULD BE IN PLACE ALL
DAY...WITH SKIES CLEARING IN THE AFTERNOON.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW MEDIUM CONFIDENCE WITH MVFR CEILINGS/TIMING/DURATION.

RODRIGUEZ

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 180314
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1014 PM CDT WED SEP 17 2014

.DISCUSSION...
819 PM CDT

NO BIG CHANGES TO MADE TO THE FORECAST THROUGH THURSDAY MORNING.
ANOTHER EARLY EVENING OF RAPID HEATING ESCAPE WITH OUTLYING
LOCATIONS DROPPING 10 TO AS MUCH AS 15 DEGREES IN THE PAST TWO
HOURS. LOOKING AT 24-HOUR CHANGE DOES INDICATE TEMPERATURES AND
DEW POINTS ARE AROUND 5 DEGREES HIGHER THAN LAST EVE AT THIS TIME
AT MOST LOCATIONS. DO THINK LOW TEMPERATURES WILL FALL OUT PRETTY
CLOSE TO THAT DEPARTURE FROM THIS MORNINGS LOWS. THIS IS RIGHT IN
THE NEIGHBORHOOD OF THE GOING FORECAST.

THE BACKDOOR COLD FRONT WITH AN IMPRESSIVE BAROCLINIC GRADIENT
BEHIND IT IS WORKING ITS WAY SOUTHWARD DOWN LAKE MICHIGAN. THE
PRIMARY COLD AIR ADVECTION WITH THIS WILL WEAKEN BY MORNING AND
ONLY GIVE A GLANCING SHOT TO THE AREA. WITH SOMEWHAT OF A SUBTLE
PUSH...THE DEGREE OF MORNING CLOUD COVER MAY END UP BEING LESS
THAN FORECAST OVER FAR NORTHEAST ILLINOIS AND FAR NORTHWEST
INDIANA...AND MOISTURE FORECASTS FROM LATEST GUIDANCE ARE TRENDING
LESS. WITH SATELLITE IMAGERY STILL INDICATING PLENTY OF CLOUDS
BEHIND THE FRONT UPSTREAM WILL OPT TO WAIT AT THIS TIME FOR ANY
CHANGES.

MTF

//PREV DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* LIGHT AND VARIABLE WINDS TONIGHT...THEN INCREASING OUT OF THE
  NORTHEAST THROUGH THURSDAY MORNING WITH FROPA...LIKELY AT 10 KT
  THROUGH THE AFTERNOON.

* MVFR STRATUS POST FROPA THURSDAY MORNING.

RODRIGUEZ

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

WITH LAKE BREEZE PASSAGE...WINDS HAVE SHIFTED TO MORE OF AN
EASTERLY DIRECTION AT 7-9 KT WHILE VFR CONDITIONS PREVAIL. CURRENT
SPEEDS ARE AT THE HIGHEST WITH SPEEDS EXPECTED TO RAPIDLY DIMINISH
OVER THE NEXT COUPLE OF HOURS. MOST OF TONIGHT WILL REMAIN QUIET
AS FRONT TO THE NORTH DROPS SOUTH TOWARDS THE TERMINALS. TIMING OF
THIS FRONT DOES APPEAR AS IF IT WILL BE SLIGHTLY SOONER EARLY
THURSDAY MORNING...SO HAVE PUSHED UP TIMING OF FROPA. HAVE LOWER
CONFIDENCE WITH CEILINGS/TRENDS THURSDAY MORNING BEHIND THE FRONT.
THERE ARE CURRENTLY MVFR CEILINGS BEHIND THE FRONT ACROSS FAR
NORTHERN LAKE MICHIGAN AND DO EXPECT THESE TO PUSH DOWN THE LAKE
WITH THE FRONT TONIGHT ALTHOUGH...GUIDANCE DOES VARY WITH THE
EXTENT OF THIS SOUTHWARD PUSH. GUIDANCE DOES TRY TO KEEP THE BULK
OF THE LOWER CLOUDS TO THE NORTHWEST AS LOW LEVEL FLOW QUICKLY
VEERS BUT WITH A STRONG NORTHERLY PUSH...CANT RULE OUT THESE LOWER
CLOUDS STILL REACHING THE TERMINALS. SO HAVE MAINTAINED MVFR
CEILINGS IN THE TAFS...BUT DID MAKE SOME MINOR CHANGES TO
HEIGHT/DURATION. DONT THINK CEILINGS SHOULD BE IN PLACE ALL
DAY...WITH SKIES CLEARING IN THE AFTERNOON.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW MEDIUM CONFIDENCE WITH MVFR CEILINGS/TIMING/DURATION.

RODRIGUEZ

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 180119 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
819 PM CDT WED SEP 17 2014

.DISCUSSION...
819 PM CDT

NO BIG CHANGES TO MADE TO THE FORECAST THROUGH THURSDAY MORNING.
ANOTHER EARLY EVENING OF RAPID HEATING ESCAPE WITH OUTLYING
LOCATIONS DROPPING 10 TO AS MUCH AS 15 DEGREES IN THE PAST TWO
HOURS. LOOKING AT 24-HOUR CHANGE DOES INDICATE TEMPERATURES AND
DEW POINTS ARE AROUND 5 DEGREES HIGHER THAN LAST EVE AT THIS TIME
AT MOST LOCATIONS. DO THINK LOW TEMPERATURES WILL FALL OUT PRETTY
CLOSE TO THAT DEPARTURE FROM THIS MORNINGS LOWS. THIS IS RIGHT IN
THE NEIGHBORHOOD OF THE GOING FORECAST.

THE BACKDOOR COLD FRONT WITH AN IMPRESSIVE BAROCLINIC GRADIENT
BEHIND IT IS WORKING ITS WAY SOUTHWARD DOWN LAKE MICHIGAN. THE
PRIMARY COLD AIR ADVECTION WITH THIS WILL WEAKEN BY MORNING AND
ONLY GIVE A GLANCING SHOT TO THE AREA. WITH SOMEWHAT OF A SUBTLE
PUSH...THE DEGREE OF MORNING CLOUD COVER MAY END UP BEING LESS
THAN FORECAST OVER FAR NORTHEAST ILLINOIS AND FAR NORTHWEST
INDIANA...AND MOISTURE FORECASTS FROM LATEST GUIDANCE ARE TRENDING
LESS. WITH SATELLITE IMAGERY STILL INDICATING PLENTY OF CLOUDS
BEHIND THE FRONT UPSTREAM WILL OPT TO WAIT AT THIS TIME FOR ANY
CHANGES.

MTF

&&

.PREV DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* EASTERLY WINDS 7-9 KT DIMINISHING EARLY THIS EVENING...THEN
  INCREASING OUT OF THE NORTHEAST THROUGH THURSDAY MORNING WITH
  FROPA...LIKELY AT 10 KT THROUGH THE AFTERNOON.

* MVFR STRATUS POST FROPA THURSDAY MORNING.

RODRIGUEZ

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

WITH LAKE BREEZE PASSAGE...WINDS HAVE SHIFTED TO MORE OF AN
EASTERLY DIRECTION AT 7-9 KT WHILE VFR CONDITIONS PREVAIL. CURRENT
SPEEDS ARE AT THE HIGHEST WITH SPEEDS EXPECTED TO RAPIDLY DIMINISH
OVER THE NEXT COUPLE OF HOURS. MOST OF TONIGHT WILL REMAIN QUIET
AS FRONT TO THE NORTH DROPS SOUTH TOWARDS THE TERMINALS. TIMING OF
THIS FRONT DOES APPEAR AS IF IT WILL BE SLIGHTLY SOONER EARLY
THURSDAY MORNING...SO HAVE PUSHED UP TIMING OF FROPA. HAVE LOWER
CONFIDENCE WITH CEILINGS/TRENDS THURSDAY MORNING BEHIND THE FRONT.
THERE ARE CURRENTLY MVFR CEILINGS BEHIND THE FRONT ACROSS FAR
NORTHERN LAKE MICHIGAN AND DO EXPECT THESE TO PUSH DOWN THE LAKE
WITH THE FRONT TONIGHT ALTHOUGH...GUIDANCE DOES VARY WITH THE
EXTENT OF THIS SOUTHWARD PUSH. GUIDANCE DOES TRY TO KEEP THE BULK
OF THE LOWER CLOUDS TO THE NORTHWEST AS LOW LEVEL FLOW QUICKLY
VEERS BUT WITH A STRONG NORTHERLY PUSH...CANT RULE OUT THESE LOWER
CLOUDS STILL REACHING THE TERMINALS. SO HAVE MAINTAINED MVFR
CEILINGS IN THE TAFS...BUT DID MAKE SOME MINOR CHANGES TO
HEIGHT/DURATION. DONT THINK CEILINGS SHOULD BE IN PLACE ALL
DAY...WITH SKIES CLEARING IN THE AFTERNOON.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW MEDIUM CONFIDENCE WITH MVFR CEILINGS/TIMING/DURATION.

RODRIGUEZ

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 180119 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
819 PM CDT WED SEP 17 2014

.DISCUSSION...
819 PM CDT

NO BIG CHANGES TO MADE TO THE FORECAST THROUGH THURSDAY MORNING.
ANOTHER EARLY EVENING OF RAPID HEATING ESCAPE WITH OUTLYING
LOCATIONS DROPPING 10 TO AS MUCH AS 15 DEGREES IN THE PAST TWO
HOURS. LOOKING AT 24-HOUR CHANGE DOES INDICATE TEMPERATURES AND
DEW POINTS ARE AROUND 5 DEGREES HIGHER THAN LAST EVE AT THIS TIME
AT MOST LOCATIONS. DO THINK LOW TEMPERATURES WILL FALL OUT PRETTY
CLOSE TO THAT DEPARTURE FROM THIS MORNINGS LOWS. THIS IS RIGHT IN
THE NEIGHBORHOOD OF THE GOING FORECAST.

THE BACKDOOR COLD FRONT WITH AN IMPRESSIVE BAROCLINIC GRADIENT
BEHIND IT IS WORKING ITS WAY SOUTHWARD DOWN LAKE MICHIGAN. THE
PRIMARY COLD AIR ADVECTION WITH THIS WILL WEAKEN BY MORNING AND
ONLY GIVE A GLANCING SHOT TO THE AREA. WITH SOMEWHAT OF A SUBTLE
PUSH...THE DEGREE OF MORNING CLOUD COVER MAY END UP BEING LESS
THAN FORECAST OVER FAR NORTHEAST ILLINOIS AND FAR NORTHWEST
INDIANA...AND MOISTURE FORECASTS FROM LATEST GUIDANCE ARE TRENDING
LESS. WITH SATELLITE IMAGERY STILL INDICATING PLENTY OF CLOUDS
BEHIND THE FRONT UPSTREAM WILL OPT TO WAIT AT THIS TIME FOR ANY
CHANGES.

MTF

&&

.PREV DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* EASTERLY WINDS 7-9 KT DIMINISHING EARLY THIS EVENING...THEN
  INCREASING OUT OF THE NORTHEAST THROUGH THURSDAY MORNING WITH
  FROPA...LIKELY AT 10 KT THROUGH THE AFTERNOON.

* MVFR STRATUS POST FROPA THURSDAY MORNING.

RODRIGUEZ

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

WITH LAKE BREEZE PASSAGE...WINDS HAVE SHIFTED TO MORE OF AN
EASTERLY DIRECTION AT 7-9 KT WHILE VFR CONDITIONS PREVAIL. CURRENT
SPEEDS ARE AT THE HIGHEST WITH SPEEDS EXPECTED TO RAPIDLY DIMINISH
OVER THE NEXT COUPLE OF HOURS. MOST OF TONIGHT WILL REMAIN QUIET
AS FRONT TO THE NORTH DROPS SOUTH TOWARDS THE TERMINALS. TIMING OF
THIS FRONT DOES APPEAR AS IF IT WILL BE SLIGHTLY SOONER EARLY
THURSDAY MORNING...SO HAVE PUSHED UP TIMING OF FROPA. HAVE LOWER
CONFIDENCE WITH CEILINGS/TRENDS THURSDAY MORNING BEHIND THE FRONT.
THERE ARE CURRENTLY MVFR CEILINGS BEHIND THE FRONT ACROSS FAR
NORTHERN LAKE MICHIGAN AND DO EXPECT THESE TO PUSH DOWN THE LAKE
WITH THE FRONT TONIGHT ALTHOUGH...GUIDANCE DOES VARY WITH THE
EXTENT OF THIS SOUTHWARD PUSH. GUIDANCE DOES TRY TO KEEP THE BULK
OF THE LOWER CLOUDS TO THE NORTHWEST AS LOW LEVEL FLOW QUICKLY
VEERS BUT WITH A STRONG NORTHERLY PUSH...CANT RULE OUT THESE LOWER
CLOUDS STILL REACHING THE TERMINALS. SO HAVE MAINTAINED MVFR
CEILINGS IN THE TAFS...BUT DID MAKE SOME MINOR CHANGES TO
HEIGHT/DURATION. DONT THINK CEILINGS SHOULD BE IN PLACE ALL
DAY...WITH SKIES CLEARING IN THE AFTERNOON.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW MEDIUM CONFIDENCE WITH MVFR CEILINGS/TIMING/DURATION.

RODRIGUEZ

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 172351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
651 PM CDT WED SEP 17 2014

.DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* EASTERLY WINDS 7-9 KT DIMINISHING EARLY THIS EVENING...THEN
  INCREASING OUT OF THE NORTHEAST THROUGH THURSDAY MORNING WITH
  FROPA...LIKELY AT 10 KT THROUGH THE AFTERNOON.

* MVFR STRATUS POST FROPA THURSDAY MORNING.

RODRIGUEZ

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

WITH LAKE BREEZE PASSAGE...WINDS HAVE SHIFTED TO MORE OF AN
EASTERLY DIRECTION AT 7-9 KT WHILE VFR CONDITIONS PREVAIL. CURRENT
SPEEDS ARE AT THE HIGHEST WITH SPEEDS EXPECTED TO RAPIDLY DIMINISH
OVER THE NEXT COUPLE OF HOURS. MOST OF TONIGHT WILL REMAIN QUIET
AS FRONT TO THE NORTH DROPS SOUTH TOWARDS THE TERMINALS. TIMING OF
THIS FRONT DOES APPEAR AS IF IT WILL BE SLIGHTLY SOONER EARLY
THURSDAY MORNING...SO HAVE PUSHED UP TIMING OF FROPA. HAVE LOWER
CONFIDENCE WITH CEILINGS/TRENDS THURSDAY MORNING BEHIND THE FRONT.
THERE ARE CURRENTLY MVFR CEILINGS BEHIND THE FRONT ACROSS FAR
NORTHERN LAKE MICHIGAN AND DO EXPECT THESE TO PUSH DOWN THE LAKE
WITH THE FRONT TONIGHT ALTHOUGH...GUIDANCE DOES VARY WITH THE
EXTENT OF THIS SOUTHWARD PUSH. GUIDANCE DOES TRY TO KEEP THE BULK
OF THE LOWER CLOUDS TO THE NORTHWEST AS LOW LEVEL FLOW QUICKLY
VEERS BUT WITH A STRONG NORTHERLY PUSH...CANT RULE OUT THESE LOWER
CLOUDS STILL REACHING THE TERMINALS. SO HAVE MAINTAINED MVFR
CEILINGS IN THE TAFS...BUT DID MAKE SOME MINOR CHANGES TO
HEIGHT/DURATION. DONT THINK CEILINGS SHOULD BE IN PLACE ALL
DAY...WITH SKIES CLEARING IN THE AFTERNOON.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW MEDIUM CONFIDENCE WITH MVFR CEILINGS/TIMING/DURATION.

RODRIGUEZ

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 172351
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
651 PM CDT WED SEP 17 2014

.DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* EASTERLY WINDS 7-9 KT DIMINISHING EARLY THIS EVENING...THEN
  INCREASING OUT OF THE NORTHEAST THROUGH THURSDAY MORNING WITH
  FROPA...LIKELY AT 10 KT THROUGH THE AFTERNOON.

* MVFR STRATUS POST FROPA THURSDAY MORNING.

RODRIGUEZ

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

WITH LAKE BREEZE PASSAGE...WINDS HAVE SHIFTED TO MORE OF AN
EASTERLY DIRECTION AT 7-9 KT WHILE VFR CONDITIONS PREVAIL. CURRENT
SPEEDS ARE AT THE HIGHEST WITH SPEEDS EXPECTED TO RAPIDLY DIMINISH
OVER THE NEXT COUPLE OF HOURS. MOST OF TONIGHT WILL REMAIN QUIET
AS FRONT TO THE NORTH DROPS SOUTH TOWARDS THE TERMINALS. TIMING OF
THIS FRONT DOES APPEAR AS IF IT WILL BE SLIGHTLY SOONER EARLY
THURSDAY MORNING...SO HAVE PUSHED UP TIMING OF FROPA. HAVE LOWER
CONFIDENCE WITH CEILINGS/TRENDS THURSDAY MORNING BEHIND THE FRONT.
THERE ARE CURRENTLY MVFR CEILINGS BEHIND THE FRONT ACROSS FAR
NORTHERN LAKE MICHIGAN AND DO EXPECT THESE TO PUSH DOWN THE LAKE
WITH THE FRONT TONIGHT ALTHOUGH...GUIDANCE DOES VARY WITH THE
EXTENT OF THIS SOUTHWARD PUSH. GUIDANCE DOES TRY TO KEEP THE BULK
OF THE LOWER CLOUDS TO THE NORTHWEST AS LOW LEVEL FLOW QUICKLY
VEERS BUT WITH A STRONG NORTHERLY PUSH...CANT RULE OUT THESE LOWER
CLOUDS STILL REACHING THE TERMINALS. SO HAVE MAINTAINED MVFR
CEILINGS IN THE TAFS...BUT DID MAKE SOME MINOR CHANGES TO
HEIGHT/DURATION. DONT THINK CEILINGS SHOULD BE IN PLACE ALL
DAY...WITH SKIES CLEARING IN THE AFTERNOON.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW MEDIUM CONFIDENCE WITH MVFR CEILINGS/TIMING/DURATION.

RODRIGUEZ

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

FRIDAY...VFR.

SATURDAY...CHANCE OF THUNDERSTORMS.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...VFR.

RODRIGUEZ

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 172154
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
454 PM CDT WED SEP 17 2014

.DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* LAKE BREEZE PUSHING THROUGH BY 2215Z...WITH WIND SHIFT TO
  EASTERLY DIRECTION UNDER 10 KT.

* COLD FRONT PASSAGE EARLY THURSDAY MORNING WITH MVFR STRATUS
  BEHIND...CHANCE THAT CIGS COULD BRIEFLY DROP TO IFR FOR AN HOUR
  OR SO.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN/RODRIGUEZ

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* HIGH CONFIDENCE IN LAKE BREEZE TIMING AND HIGH CONFIDENCE WITH
  SPEEDS STAYING UNDER 10 KT.

* MEDIUM TO HIGH CONFIDENCE IN MVFR CIGS THURSDAY MORNING...LOWER
  CONFIDENCE IN CHANCES FOR IFR CIGS.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 172154
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
454 PM CDT WED SEP 17 2014

.DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* LAKE BREEZE PUSHING THROUGH BY 2215Z...WITH WIND SHIFT TO
  EASTERLY DIRECTION UNDER 10 KT.

* COLD FRONT PASSAGE EARLY THURSDAY MORNING WITH MVFR STRATUS
  BEHIND...CHANCE THAT CIGS COULD BRIEFLY DROP TO IFR FOR AN HOUR
  OR SO.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN/RODRIGUEZ

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* HIGH CONFIDENCE IN LAKE BREEZE TIMING AND HIGH CONFIDENCE WITH
  SPEEDS STAYING UNDER 10 KT.

* MEDIUM TO HIGH CONFIDENCE IN MVFR CIGS THURSDAY MORNING...LOWER
  CONFIDENCE IN CHANCES FOR IFR CIGS.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN/RODRIGUEZ

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 172020
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
320 PM CDT WED SEP 17 2014

.DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON...MOVED TIMING OF BOUNDARY PASSAGE
  AND WIND SHIFT TO ELY UP TO 22Z AND BUMPED UP WINDS TO 8KT.

* COLD FRONT PASSAGE EARLY THURSDAY MORNING WITH MVFR STRATUS
  BEHIND...CHANCE THAT CIGS COULD BRIEFLY DROP TO IFR FOR AN HOUR
  OR SO.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING.

* MEDIUM TO HIGH CONFIDENCE IN MVFR CIGS THURSDAY MORNING...LOWER
  CONFIDENCE IN CHANCES FOR IFR CIGS.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 172020
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
320 PM CDT WED SEP 17 2014

.DISCUSSION...
319 PM CDT

THE LAKE BREEZE SLOWLY EASING INLAND ACROSS FAR EASTERN COOK AND
LAKE COUNTIES IN ILLINOIS...AND AS SUCH...THIS IS PRODUCING
SLIGHTLY COOLER CONDITIONS LAKESIDE WITH THE ONSHORE FLOW.

ATTENTION IS FOCUSED ON A COLD FRONTAL BOUNDARY...CURRENTLY SHIFTING
SOUTHWARD ACROSS THE U.P. OF MICHIGAN. THIS BOUNDARY IS THE LEADING
EDGE OF A RATHER STOUT BAROCLINIC ZONE. MUCH COLDER AIR...COLD
ENOUGH TO SUPPORT SNOW...IS IN PLACE NORTH OF THE FRONT ACROSS
SOUTHERN CANADA. FORTUNATELY FOR US...THE CORE OF THIS COLD AIRMASS
WILL SLIDE EAST-SOUTHEASTWARD ACROSS SOUTHEASTERN CANADA AND NEW
ENGLAND. HOWEVER...THE SURFACE BOUNDARY IS EXPECTED TO SHIFT OVER
THE AREA AS A BACK DOOR COLD FRONT BY EARLY THURSDAY MORNING. THIS
SHOULD RESULT IN WINDS COMING IN OFF THE LAKE THROUGH THE DAY
TOMORROW...ALONG WITH INCREASED CLOUDINESS. IT APPEARS THAT SOME
LOWER STRATOCU WILL OVERSPREAD PORTIONS OF NORTHERN ILLINOIS BY
AROUND DAYBREAK THURSDAY...POSSIBLY LASTING INTO THE AFTERNOON
BEFORE SLOWLY DISSIPATING. THERE COULD EVEN BE A FEW LIGHT LAKE
EFFECT RAIN SHOWERS/SPRINKLES LATER THURSDAY MORNING. MODELS
SOUNDINGS INDICATE JUST ENOUGH COOL AIR MOVING OVER THE LAKE TO
RESULT IN SOME HIGHER EL`S UP TO AROUND 7500 FEET AGL. THIS COULD BE
ENOUGH TO SQUEEZE OUT A FEW VERY LIGHT SHOWERS. I ADDED A SLIGHT
CHANCE OF SPRINKLES TO COVER THIS MINOR THREAT. OTHERWISE...COOLER
CONDITIONS...IN THE LOWER 60S...WILL BE FAVORED ACROSS NORTHEASTERN
ILLINOIS DUE TO THE ONSHORE FLOW.

THE WARMER AIR WILL MAKE A QUICK RETURN TO THE AREA ON FRIDAY AS
WARM AIR ADVECTION AND UPPER LEVEL HEIGHT RISES RAMP UP AHEAD OF AN
AREA OF LOW PRESSURE ACROSS CANADA. THIS SHOULD RESULT IN
TEMPERATURES WELL INTO THE 70S AREA-WIDE BY FRIDAY...AND INTO THE
LOWER 80S FOR SATURDAY.

THUNDERSTORMS STILL LOOK LIKE A GOOD BET ON SATURDAY INTO SATURDAY
EVENING AS A COLD FRONT APPROACHES THE AREA. VERY WARM AND MOIST
CONDITIONS ARE FORECAST TO SETUP ALONG A CORRIDOR TO THE SOUTH OF THE
APPROACHING COLD FRONT...AND THIS SHOULD YIELD CONDITIONS FAVORABLE
FOR THUNDERSTORMS WITH AT LEAST A BRIEF TORRENTIAL DOWNPOUR THREAT.
GUIDANCE INDICATES PWATS COULD EXCEED 1.6 INCHES WITHIN THE
PREFRONTAL AIRMASS ACROSS NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
SATURDAY. AS SUCH...THIS COULD LEAD TO SOME EFFICIENT RAIN RATES WITH
ANY STORMS THAT DEVELOP. THERE COULD ALSO BE A FEW STRONG...MORE
ORGANIZED...STORMS SATURDAY AFTERNOON GIVEN THE POTENTIAL OF A MID
LEVEL JET DEVELOPING SOUTHWARD OVER THE AREA.

FOLLOWING THIS SYSTEM TEMPERATURES WILL TREND COOLER AGAIN...AND THE
WEATHER SHOULD BE DRY FOR A COUPLE OF DAYS EARLY NEXT WEEK AS ANOTHER
SURFACE HIGH IS PROGGED TO SHIFT RIGHT OVER THE AREA BY LATE MONDAY
INTO TUESDAY.

KJB

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON...MOVED TIMING OF BOUNDARY PASSAGE
  AND WIND SHIFT TO ELY UP TO 22Z AND BUMPED UP WINDS TO 8KT.

* COLD FRONT PASSAGE EARLY THURSDAY MORNING WITH MVFR STRATUS
  BEHIND...CHANCE THAT CIGS COULD BRIEFLY DROP TO IFR FOR AN HOUR
  OR SO.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING.

* MEDIUM TO HIGH CONFIDENCE IN MVFR CIGS THURSDAY MORNING...LOWER
  CONFIDENCE IN CHANCES FOR IFR CIGS.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 171941
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
241 PM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON...MOVED TIMING OF BOUNDARY PASSAGE
  AND WIND SHIFT TO ELY UP TO 22Z AND BUMPED UP WINDS TO 8KT.

* COLD FRONT PASSAGE EARLY THURSDAY MORNING WITH MVFR STRATUS
  BEHIND...CHANCE THAT CIGS COULD BRIEFLY DROP TO IFR FOR AN HOUR
  OR SO.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING.

* MEDIUM TO HIGH CONFIDENCE IN MVFR CIGS THURSDAY MORNING...LOWER
  CONFIDENCE IN CHANCES FOR IFR CIGS.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 171941
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
241 PM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON...MOVED TIMING OF BOUNDARY PASSAGE
  AND WIND SHIFT TO ELY UP TO 22Z AND BUMPED UP WINDS TO 8KT.

* COLD FRONT PASSAGE EARLY THURSDAY MORNING WITH MVFR STRATUS
  BEHIND...CHANCE THAT CIGS COULD BRIEFLY DROP TO IFR FOR AN HOUR
  OR SO.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING.

* MEDIUM TO HIGH CONFIDENCE IN MVFR CIGS THURSDAY MORNING...LOWER
  CONFIDENCE IN CHANCES FOR IFR CIGS.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 171829
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
129 PM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH CHANCE OF LOWER STRATUS
  BEHIND.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 171829
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
129 PM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH CHANCE OF LOWER STRATUS
  BEHIND.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
128 PM CDT

AN AREA OF LOW PRESSURE OVER THE EASTERN UPPER PENINSULA OF MICHIGAN
EARLY THIS AFTERNOON WILL CONTINUE TO MOVE EAST TONIGHT...TRAILING A
COLD FRONT WHICH WILL PUSH SOUTH DOWN THE LENGTH OF LAKE MICHIGAN
THROUGH TONIGHT AND EARLY THURSDAY MORNING. AS THE FRONT BEGINS TO
DROP SOUTH OVER THE NORTHERN END OF LAKE MICHIGAN BY EARLY THIS
EVENING...WINDS WILL VEER TO THE NORTH IN THE 20-25 KT RANGE. WINDS
WILL DIMINISH LATE TONIGHT AND THURSDAY AS THE FRONT PUSHES FARTHER
DOWN THE LAKE...AND LOSES SOME OF ITS PUNCH. HIGH PRESSURE WILL THEN
BUILD SOUTHEAST ACROSS THE NORTHERN LAKES AND EVENTUALLY ACROSS NEW
ENGLAND BY FRIDAY...WITH WINDS ON LAKE MICHIGAN SHIFTING BACK TO THE
SOUTH AND INCREASING LATE THURSDAY NIGHT. SOUTH WINDS TO 30 KT ARE
ANTICIPATED ACROSS THE LAKE FRIDAY AS THE GRADIENT TIGHTENS IN
RESPONSE TO LOW PRESSURE MOVING NORTH OF THE LAKES...AND A PERIOD OF
GALES OR AT LEAST SOME GALE FORCE GUSTS ARE POSSIBLE ESPECIALLY
ACROSS NORTHERN LAKE MICHIGAN LATE FRIDAY INTO EARLY SATURDAY.
FORECAST SOUNDINGS DEPICT 35-40 KT ABOVE THE SHALLOW MARINE BOUNDARY
LAYER DURING THIS TIME...WITH THE DRIVING FACTOR BEING THE DEPTH OF
MIXING IN THE SOUTHERLY WARM ADVECTION FLOW. THE LOW WILL PASS NORTH
OF THE LAKE LATE SATURDAY INTO SUNDAY...WITH A COLD FRONT PUSHING
SOUTHEAST SATURDAY NIGHT RESULTING IN A SHIFT TO NORTHWEST WINDS FOR
SUNDAY AND MONDAY.

RATZER

&&

.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 171806
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 PM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH CHANCE OF LOWER STRATUS
  BEHIND.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 171806
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
106 PM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH CHANCE OF LOWER STRATUS
  BEHIND.

* NELY WINDS TO 10KT THURSDAY AFTERNOON.

KREIN

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

A LARGE AREA OF HIGH PRESSURE COVERS THE REGION. THE WEAK PRESSURE
GRADIENT SHOULD ALLOW FOR A LAKE BREEZE TO DEVELOP LATE THIS
AFTERNOON. WITH LAND AND WATER TEMPERATURES SOMEWHAT
SIMILAR...THERE WILL NOT BE MUCH PUSH BEHIND THE BOUNDARY...SO
EXPECT THAT EXPECTED ELY WINDS SHOULD ONLY BE 5-7 KT.

WITH SUNSET...THE LAKE BREEZE SHOULD WASH OUT AND WINDS WILL
BECOME LGT/VRBL. THE LIGHT WINDS AND MOSTLY CLEAR SKIES SHOULD
ALLOW SOME PATCHY SHALLOW GROUND FOG TO DEVELOP...MAINLY IN RURAL
AREAS.

A COLD FRONT IS EXPECTED TO DROP SOUTH OUT OF WISCONSIN AND DOWN
THE LENGTH OF LAKE MICHIGAN...SETTING UP NELY WINDS BY THE LATE
MORNING HOURS. WITH A STRONGER COLD PUSH BEHIND THIS
BOUNDARY...ANTICIPATE THAT THE NELY WINDS SHOULD APPROACH 10KT
DURG THE AFTERNOON HOURS. THERE IS A CHANCE OF SOME LOWER STRATUS
BEHIND THE COLD FRONT...ESPECIALLY CLOSER TO THE LAKE FRONT...BUT
THE MODEL GUIDANCE IS STILL SHOWING A FAIR AMOUNT OF VARIABILITY
TO THE LOW LEVEL MOISTURE PROFILES...SO WILL KEEP THE GOING
FORECAST FOR VFR SKIES AND MONITOR CONDITIONS AS THE COLD FRONT
WORKS DOWN THE LAKE LATER THIS EVENING AND TONIGHT.

KREIN

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* MEDIUM CONFIDENCE THAT WINDS COULD REACH OR SLIGHTLY EXCEED 10
  KT TOMORROW AFTERNOON.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 171609
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1109 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH POSSIBILITY OF LOWER
  STRATUS BEHIND.

KREIN

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

HIGH PRESSURE WILL BE IN PLACE TODAY WITH CONTINUED LIGHT WINDS AND
PRIMARILY VFR CONDITIONS OUTSIDE OF EARLY MORNING FOG. CONFIDENCE IN
WIND DIRECTION IS LOWER MAINLY DUE TO THE OVERALL LIGHT
MAGNITUDE...BUT EXPECT A GENERALLY SOUTHWEST WIND EARLY THIS MORNING
TO GRADUALLY VEER TO NORTHWEST BY EARLY AFTERNOON...THEN A LAKE
BREEZE WILL TURN WINDS EASTERLY MID TO LATE THIS AFTERNOON.
THROUGHOUT WINDS SHOULD REMAIN LESS THAN 10 KT. MOSTLY SUNNY SKIES
WILL BE IN PLACE AGAIN TODAY WITH A FEW MORE MID AND HIGH CLOUDS AS
COMPARED TO YESTERDAY. WINDS ARE EXPECTED TO GO LIGHT AND VARIABLE
OVERNIGHT...THEN LATE TONIGHT INTO EARLY THURSDAY A COLD FRONT WILL
DROP ACROSS THE REGION TURNING WINDS BACK TO THE NORTHEAST. SOME
MODELS HINT AT THE POSSIBILITY OF SOME MVFR STRATUS COMING IN BEHIND
THE FRONT.

BMD

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* HIGH CONFIDENCE IN WINDS LESS THAN 10 KT.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 171609
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1109 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH POSSIBILITY OF LOWER
  STRATUS BEHIND.

KREIN

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

HIGH PRESSURE WILL BE IN PLACE TODAY WITH CONTINUED LIGHT WINDS AND
PRIMARILY VFR CONDITIONS OUTSIDE OF EARLY MORNING FOG. CONFIDENCE IN
WIND DIRECTION IS LOWER MAINLY DUE TO THE OVERALL LIGHT
MAGNITUDE...BUT EXPECT A GENERALLY SOUTHWEST WIND EARLY THIS MORNING
TO GRADUALLY VEER TO NORTHWEST BY EARLY AFTERNOON...THEN A LAKE
BREEZE WILL TURN WINDS EASTERLY MID TO LATE THIS AFTERNOON.
THROUGHOUT WINDS SHOULD REMAIN LESS THAN 10 KT. MOSTLY SUNNY SKIES
WILL BE IN PLACE AGAIN TODAY WITH A FEW MORE MID AND HIGH CLOUDS AS
COMPARED TO YESTERDAY. WINDS ARE EXPECTED TO GO LIGHT AND VARIABLE
OVERNIGHT...THEN LATE TONIGHT INTO EARLY THURSDAY A COLD FRONT WILL
DROP ACROSS THE REGION TURNING WINDS BACK TO THE NORTHEAST. SOME
MODELS HINT AT THE POSSIBILITY OF SOME MVFR STRATUS COMING IN BEHIND
THE FRONT.

BMD

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* HIGH CONFIDENCE IN WINDS LESS THAN 10 KT.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 171353
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
853 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH POSSIBILITY OF LOWER
  STRATUS BEHIND.

KREIN

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

HIGH PRESSURE WILL BE IN PLACE TODAY WITH CONTINUED LIGHT WINDS AND
PRIMARILY VFR CONDITIONS OUTSIDE OF EARLY MORNING FOG. CONFIDENCE IN
WIND DIRECTION IS LOWER MAINLY DUE TO THE OVERALL LIGHT
MAGNITUDE...BUT EXPECT A GENERALLY SOUTHWEST WIND EARLY THIS MORNING
TO GRADUALLY VEER TO NORTHWEST BY EARLY AFTERNOON...THEN A LAKE
BREEZE WILL TURN WINDS EASTERLY MID TO LATE THIS AFTERNOON.
THROUGHOUT WINDS SHOULD REMAIN LESS THAN 10 KT. MOSTLY SUNNY SKIES
WILL BE IN PLACE AGAIN TODAY WITH A FEW MORE MID AND HIGH CLOUDS AS
COMPARED TO YESTERDAY. WINDS ARE EXPECTED TO GO LIGHT AND VARIABLE
OVERNIGHT...THEN LATE TONIGHT INTO EARLY THURSDAY A COLD FRONT WILL
DROP ACROSS THE REGION TURNING WINDS BACK TO THE NORTHEAST. SOME
MODELS HINT AT THE POSSIBILITY OF SOME MVFR STRATUS COMING IN BEHIND
THE FRONT.

BMD

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* HIGH CONFIDENCE IN WINDS LESS THAN 10 KT.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 171353
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
853 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.

* COLD FRONT PASSAGE EARLY THURSDAY WITH POSSIBILITY OF LOWER
  STRATUS BEHIND.

KREIN

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

HIGH PRESSURE WILL BE IN PLACE TODAY WITH CONTINUED LIGHT WINDS AND
PRIMARILY VFR CONDITIONS OUTSIDE OF EARLY MORNING FOG. CONFIDENCE IN
WIND DIRECTION IS LOWER MAINLY DUE TO THE OVERALL LIGHT
MAGNITUDE...BUT EXPECT A GENERALLY SOUTHWEST WIND EARLY THIS MORNING
TO GRADUALLY VEER TO NORTHWEST BY EARLY AFTERNOON...THEN A LAKE
BREEZE WILL TURN WINDS EASTERLY MID TO LATE THIS AFTERNOON.
THROUGHOUT WINDS SHOULD REMAIN LESS THAN 10 KT. MOSTLY SUNNY SKIES
WILL BE IN PLACE AGAIN TODAY WITH A FEW MORE MID AND HIGH CLOUDS AS
COMPARED TO YESTERDAY. WINDS ARE EXPECTED TO GO LIGHT AND VARIABLE
OVERNIGHT...THEN LATE TONIGHT INTO EARLY THURSDAY A COLD FRONT WILL
DROP ACROSS THE REGION TURNING WINDS BACK TO THE NORTHEAST. SOME
MODELS HINT AT THE POSSIBILITY OF SOME MVFR STRATUS COMING IN BEHIND
THE FRONT.

BMD

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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.

* LOW CONFIDENCE IN CIGS THURSDAY MORNING.

* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.

* HIGH CONFIDENCE IN WINDS LESS THAN 10 KT.

KREIN

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 171119
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
619 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.
* COLD FRONT EARLY THURSDAY WITH POSSIBILITY OF LOWER STRATUS
  BEHIND.

BMD

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

HIGH PRESSURE WILL BE IN PLACE TODAY WITH CONTINUED LIGHT WINDS AND
PRIMARILY VFR CONDITIONS OUTSIDE OF EARLY MORNING FOG. CONFIDENCE IN
WIND DIRECTION IS LOWER MAINLY DUE TO THE OVERALL LIGHT
MAGNITUDE...BUT EXPECT A GENERALLY SOUTHWEST WIND EARLY THIS MORNING
TO GRADUALLY VEER TO NORTHWEST BY EARLY AFTERNOON...THEN A LAKE
BREEZE WILL TURN WINDS EASTERLY MID TO LATE THIS AFTERNOON.
THROUGHOUT WINDS SHOULD REMAIN LESS THAN 10 KT. MOSTLY SUNNY SKIES
WILL BE IN PLACE AGAIN TODAY WITH A FEW MORE MID AND HIGH CLOUDS AS
COMPARED TO YESTERDAY. WINDS ARE EXPECTED TO GO LIGHT AND VARIABLE
OVERNIGHT...THEN LATE TONIGHT INTO EARLY THURSDAY A COLD FRONT WILL
DROP ACROSS THE REGION TURNING WINDS BACK TO THE NORTHEAST. SOME
MODELS HINT AT THE POSSIBILITY OF SOME MVFR STRATUS COMING IN BEHIND
THE FRONT.

BMD


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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.
* LOW CONFIDENCE IN CIGS THURSDAY MORNING.
* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.
* HIGH CONFIDENCE IN WINDS LESS THAN 10 KT.

BMD

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 171119
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
619 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE THIS AFTERNOON.
* COLD FRONT EARLY THURSDAY WITH POSSIBILITY OF LOWER STRATUS
  BEHIND.

BMD

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

HIGH PRESSURE WILL BE IN PLACE TODAY WITH CONTINUED LIGHT WINDS AND
PRIMARILY VFR CONDITIONS OUTSIDE OF EARLY MORNING FOG. CONFIDENCE IN
WIND DIRECTION IS LOWER MAINLY DUE TO THE OVERALL LIGHT
MAGNITUDE...BUT EXPECT A GENERALLY SOUTHWEST WIND EARLY THIS MORNING
TO GRADUALLY VEER TO NORTHWEST BY EARLY AFTERNOON...THEN A LAKE
BREEZE WILL TURN WINDS EASTERLY MID TO LATE THIS AFTERNOON.
THROUGHOUT WINDS SHOULD REMAIN LESS THAN 10 KT. MOSTLY SUNNY SKIES
WILL BE IN PLACE AGAIN TODAY WITH A FEW MORE MID AND HIGH CLOUDS AS
COMPARED TO YESTERDAY. WINDS ARE EXPECTED TO GO LIGHT AND VARIABLE
OVERNIGHT...THEN LATE TONIGHT INTO EARLY THURSDAY A COLD FRONT WILL
DROP ACROSS THE REGION TURNING WINDS BACK TO THE NORTHEAST. SOME
MODELS HINT AT THE POSSIBILITY OF SOME MVFR STRATUS COMING IN BEHIND
THE FRONT.

BMD


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

* MEDIUM-HIGH CONFIDENCE IN LAKE BREEZE TIMING TO WITHIN AN HOUR
  OR TWO.
* LOW CONFIDENCE IN CIGS THURSDAY MORNING.
* HIGH CONFIDENCE IN VFR CONDITIONS TODAY AND MOST OF TONIGHT.
* HIGH CONFIDENCE IN WINDS LESS THAN 10 KT.

BMD

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

THURSDAY NIGHT THROUGH FRIDAY...VFR
SATURDAY...CHANCE OF THUNDERSTORMS.
SUNDAY THROUGH TUESDAY...VFR.

BMD

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 170906
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
406 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD

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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 170906
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
406 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD

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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 170731
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
231 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD

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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 170731
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
231 AM CDT WED SEP 17 2014

.DISCUSSION...
231 AM CDT

OVERARCHING THEME OF THE FORECAST FOR THE NEXT SEVEN DAYS IS FAIRLY
NICE EARLY FALL WEATHER WITH A DASH OF UNSEASONABLE WARMTH AND
SPLASH OF THUNDERSTORMS.

TODAY LOOKS TO BE ANOTHER GLORIOUS DAY...LIKELY A COUPLE/FEW DEGREES
WARMER THAN TUESDAY. GUIDANCE WAS A COUPLE DEGREES TOO COOL WITH
HIGHS TUESDAY AND WITH 925MB AND 850MB TEMPS PROGGED TO BE 2-3C
WARMER THAN YESTERDAY HAVE OPTED TO GO A COUPLE DEGREES ABOVE
GUIDANCE WITH HIGHS NEAR OR INTO THE LOWER 70S MOST AREAS. SOME
ACCAS AND MID LEVEL CLOUDINESS UPSTREAM ASSOCIATED WITH MID-LEVEL
WARM AIR ADVECTION COULD LEAD TO A BIT MORE CLOUDINESS THAN THE
NEARLY CLOUD FREE SKIES TUESDAY BUT STILL LOOK FOR PLENTY OF
SUNSHINE TODAY.

WEAKENING BACKDOOR COLD FRONT MOVES IN OFF THE LAKE EARLY THURSDAY
MORNING RESULTING IN SOME SLIGHTLY COOLER TEMPS THURS...ESPECIALLY
DOWNWIND OF THE LAKE WHERE NORTHEAST WINDS WILL HAVE A BETTER UMPH
BEHIND THE FRONT AND RESULT IN A GREATER LAKE INFLUENCE TO TEMPS.
WINDS BEGIN TO VEER AND SHOULD BECOMING SOUTHEASTERLY THURSDAY NIGHT
WITH WARM AIR ADVECTION GETTING UNDERWAY. WARM AIR ADVECTION GETS
GOING INTO FULL GEAR BY LATE FRIDAY AND GIVEN THE LATER ARRIVAL OF
THE TOASTIER TEMPS ITS UNCLEAR HOW MUCH WARMING WILL BE REALIZED
WITH HIGHS FRIDAY. HAVE CONSERVATIVELY BUMPED TEMPS UP INTO THE 70S
AREA WIDE...BUT PROGGED 00Z 850MB/925MB TEMPS WOULD ACTUALLY SUPPORT
TEMPS AROUND 80F. FRIDAY NIGHT LOOKS TO BE FAIRLY WARM WITH
SOUTHERLY WINDS CONTINUING...IN FACT MANY AREAS WILL SEE LOW TEMPS
FRI NIGHT WARMER THAN HIGH TEMPS WERE LAST WEEK! GUIDANCE CONTINUES
TO ADVERTISE 850MB TEMPS IN THE MID-UPPER TEENS WITH 925MB TEMPS
AROUND 20C...WHICH CLIMO SUGGESTS HIGHS WELL INTO THE 80S. HAVE
TRENDED TEMPS UPWARD SOME INTO THE LOW TO MID 80S AND WITH ENOUGH
SUNSHINE EVEN THOSE FORECAST HIGHS COULD END UP BEING A BIT TOO LOW!

COLD FRONT STILL LOOKS SLATED TO ARRIVE LATE SATURDAY WITH SHOWERS
AND THUNDERSTORMS CERTAINLY LOOKING LIKE A DECENT BET ALONG THE
FRONT. MEDIUM RANGE GUIDANCE HAS TRENDED TOWARD LESS PHASING WITH
THE NORTHERN STREAM TROUGH AND THE REMNANTS OF ODILE...SO NOT
LOOKING LIKE QUITE AS BIG OF A RAIN PRODUCER AS PREVIOUS RUNS
SUGGESTED. THE PUSH OF COLDER AIR BEHIND THE FRONT SATURDAY LOOKS TO
COME IN PHASES...WITH THE FIRST PHASE INITIALLY LOOKING LIKE MORE OF
A PUSH OF PACIFIC AIR SUNDAY BEFORE SECONDARY PUSH OF MORE
SUBSTANTIAL COLD AIR ARRIVES EARLY NEXT WEEK SENDING TEMPS DROPPING
BELOW AVERAGE AGAIN.

IZZI

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD

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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 170723
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
223 AM CDT WED SEP 17 2014

.DISCUSSION...
908 PM CDT

ONLY MINOR CHANGES MADE TO THE REST OF TONIGHTS FORECAST. WITH
CLEAR SKIES AND LIGHT WINDS ALLOWING FOR IDEAL RADIATIONAL COOLING
IN THE CONTINUED COOL AND DRY AIR MASS...TEMPERATURES DROPPED AS
MUCH AS 15 DEGREES IN TWO HOURS EARLY THIS EVENING. CONSIDERING
MINIMUM TEMPERATURES LAST NIGHT AND DEW POINTS RUNNING LOWER AT
MOST LOCATIONS...HAVE NUDGED MINIMUM TEMPERATURES DOWN A COUPLE
DEGREES. WOULD EXPECT TO SEE SOME ISOLATED SUB 40 DEGREE READINGS
IN THE USUAL OUTLYING LOCATIONS.

SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE EXISTS IN PARTS OF EAST
CENTRAL IL AND NORTHWEST IN...AS EVIDENCED BY DEW POINTS AND
EARLIER DAYTIME CUMULUS. THIS PROBABLY WILL ALLOW FOR PATCHY
SHALLOW FOG IN THIS AREA. HAVE ADDED INTO THE FORECAST BUT SHOULD
NOT BE A BIG IMPACT.

MTF

//PREV DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD

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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 170723
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
223 AM CDT WED SEP 17 2014

.DISCUSSION...
908 PM CDT

ONLY MINOR CHANGES MADE TO THE REST OF TONIGHTS FORECAST. WITH
CLEAR SKIES AND LIGHT WINDS ALLOWING FOR IDEAL RADIATIONAL COOLING
IN THE CONTINUED COOL AND DRY AIR MASS...TEMPERATURES DROPPED AS
MUCH AS 15 DEGREES IN TWO HOURS EARLY THIS EVENING. CONSIDERING
MINIMUM TEMPERATURES LAST NIGHT AND DEW POINTS RUNNING LOWER AT
MOST LOCATIONS...HAVE NUDGED MINIMUM TEMPERATURES DOWN A COUPLE
DEGREES. WOULD EXPECT TO SEE SOME ISOLATED SUB 40 DEGREE READINGS
IN THE USUAL OUTLYING LOCATIONS.

SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE EXISTS IN PARTS OF EAST
CENTRAL IL AND NORTHWEST IN...AS EVIDENCED BY DEW POINTS AND
EARLIER DAYTIME CUMULUS. THIS PROBABLY WILL ALLOW FOR PATCHY
SHALLOW FOG IN THIS AREA. HAVE ADDED INTO THE FORECAST BUT SHOULD
NOT BE A BIG IMPACT.

MTF

//PREV DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD

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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
222 AM CDT

AREAS OF HIGH PRESSURE LIE ACROSS THE OHIO VALLEY AND THE CANADIAN
PRAIRIES EARLY THIS MORNING WITH COLD FRONT IN BETWEEN THESE TWO
FEATURES JUST NORTH OF LAKE MICHIGAN. THIS FRONT WILL MOVE SOUTH
ACROSS THE LAKE THIS EVENING AND TONIGHT WITH WINDS TURNING
NORTHEAST AND INCREASING SHARPLY INTO THE 20-25 KT RANGE
PARTICULARLY OVER THE NORTH HALF OF THE LAKE. WINDS DIMINISH
THURSDAY..THEN TURN BACK TO THE SOUTHEAST AND INCREASE AGAIN
THURSDAY NIGHT INTO FRIDAY. BY FRIDAY...SOUTH WINDS TO 30 KT ARE
EXPECTED OVER THE NORTH HALF OF THE LAKE AND A BRIEF PERIOD OF SOUTH
GALES IS NOT OUT OF THE QUESTION. WINDS WILL REMAIN FRESH THROUGH
THE WEEKEND...TURNING NORTHWEST ON SUNDAY AS ANOTHER COLD FRONT
MOVES ACROSS THE LAKE.

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 170522
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1222 AM CDT WED SEP 17 2014

.DISCUSSION...
908 PM CDT

ONLY MINOR CHANGES MADE TO THE REST OF TONIGHTS FORECAST. WITH
CLEAR SKIES AND LIGHT WINDS ALLOWING FOR IDEAL RADIATIONAL COOLING
IN THE CONTINUED COOL AND DRY AIR MASS...TEMPERATURES DROPPED AS
MUCH AS 15 DEGREES IN TWO HOURS EARLY THIS EVENING. CONSIDERING
MINIMUM TEMPERATURES LAST NIGHT AND DEW POINTS RUNNING LOWER AT
MOST LOCATIONS...HAVE NUDGED MINIMUM TEMPERATURES DOWN A COUPLE
DEGREES. WOULD EXPECT TO SEE SOME ISOLATED SUB 40 DEGREE READINGS
IN THE USUAL OUTLYING LOCATIONS.

SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE EXISTS IN PARTS OF EAST
CENTRAL IL AND NORTHWEST IN...AS EVIDENCED BY DEW POINTS AND
EARLIER DAYTIME CUMULUS. THIS PROBABLY WILL ALLOW FOR PATCHY
SHALLOW FOG IN THIS AREA. HAVE ADDED INTO THE FORECAST BUT SHOULD
NOT BE A BIG IMPACT.

MTF

//PREV DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD


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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 170522
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1222 AM CDT WED SEP 17 2014

.DISCUSSION...
908 PM CDT

ONLY MINOR CHANGES MADE TO THE REST OF TONIGHTS FORECAST. WITH
CLEAR SKIES AND LIGHT WINDS ALLOWING FOR IDEAL RADIATIONAL COOLING
IN THE CONTINUED COOL AND DRY AIR MASS...TEMPERATURES DROPPED AS
MUCH AS 15 DEGREES IN TWO HOURS EARLY THIS EVENING. CONSIDERING
MINIMUM TEMPERATURES LAST NIGHT AND DEW POINTS RUNNING LOWER AT
MOST LOCATIONS...HAVE NUDGED MINIMUM TEMPERATURES DOWN A COUPLE
DEGREES. WOULD EXPECT TO SEE SOME ISOLATED SUB 40 DEGREE READINGS
IN THE USUAL OUTLYING LOCATIONS.

SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE EXISTS IN PARTS OF EAST
CENTRAL IL AND NORTHWEST IN...AS EVIDENCED BY DEW POINTS AND
EARLIER DAYTIME CUMULUS. THIS PROBABLY WILL ALLOW FOR PATCHY
SHALLOW FOG IN THIS AREA. HAVE ADDED INTO THE FORECAST BUT SHOULD
NOT BE A BIG IMPACT.

MTF

//PREV DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

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

ANOTHER QUIET WEATHER DAY IS ON TAP FOR THE REGION WITH HIGH
PRESSURE CENTERED SOUTH OF THE AREA PROVIDING CONTINUED LIGHT FLOW
AND PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG. FOG IS
EXPECTED TO STAY SOUTH OF THE TERMINALS TONIGHT. A FEW MID LEVEL
CLOUDS MAY DEVELOP MIDDAY WEDNESDAY. A LAKE BREEZE IS ALSO EXPECTED
TO DEVELOP AND SHOULD PUSH ACROSS THE TERMINALS EARLY TO MID
AFTERNOON TURNING WINDS EASTERLY AND BRIEFLY INCREASING SPEEDS INTO
THE 7-9 KT RANGE.

BMD


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

* MEDIUM-HIGH ON LAKE BREEZE TO WITHIN A COUPLE HOURS.
* HIGH ON REMAINING FORECAST ELEMENTS.

BMD

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 170303
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1003 PM CDT TUE SEP 16 2014

.DISCUSSION...
908 PM CDT

ONLY MINOR CHANGES MADE TO THE REST OF TONIGHTS FORECAST. WITH
CLEAR SKIES AND LIGHT WINDS ALLOWING FOR IDEAL RADIATIONAL COOLING
IN THE CONTINUED COOL AND DRY AIR MASS...TEMPERATURES DROPPED AS
MUCH AS 15 DEGREES IN TWO HOURS EARLY THIS EVENING. CONSIDERING
MINIMUM TEMPERATURES LAST NIGHT AND DEW POINTS RUNNING LOWER AT
MOST LOCATIONS...HAVE NUDGED MINIMUM TEMPERATURES DOWN A COUPLE
DEGREES. WOULD EXPECT TO SEE SOME ISOLATED SUB 40 DEGREE READINGS
IN THE USUAL OUTLYING LOCATIONS.

SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE EXISTS IN PARTS OF EAST
CENTRAL IL AND NORTHWEST IN...AS EVIDENCED BY DEW POINTS AND
EARLIER DAYTIME CUMULUS. THIS PROBABLY WILL ALLOW FOR PATCHY
SHALLOW FOG IN THIS AREA. HAVE ADDED INTO THE FORECAST BUT SHOULD
NOT BE A BIG IMPACT.

MTF

//PREV DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE LATE WEDNESDAY AFTERNOON. CMS

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

THE LAKE BREEZE HAS SURGED INLAND AND IS CURRENTLY MOVING WEST
THROUGH ORD/MDW. SPEEDS MAY REACH 8-10KTS WITH ITS PASSAGE BUT
THEN DIMINISH BACK TO 4-6KTS FOR A FEW HOURS. HIGH PRESSURE OVER
THE REGION TONIGHT WILL ALLOW WINDS TO BECOME LIGHT AND VARIABLE
OR CALM BY LATE EVENING. WINDS WILL THEN BECOME LIGHT SOUTHWEST
OR WEST WEDNESDAY MORNING WITH THE WEAK GRADIENT REMAINING AS THE
CENTER OF THE HIGH SHIFTS EAST. ANOTHER LAKE BREEZE SHOULD
DEVELOP WEDNESDAY AFTERNOON...POSSIBLY REACHING ORD/MDW BY LATE
AFTERNOON. CMS

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

* MEDIUM FOR A LAKE BREEZE REACHING ORD/MDW WEDNESDAY AFTERNOON.
  CMS

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 170209 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 PM CDT TUE SEP 16 2014

.DISCUSSION...
908 PM CDT

ONLY MINOR CHANGES MADE TO THE REST OF TONIGHTS FORECAST. WITH
CLEAR SKIES AND LIGHT WINDS ALLOWING FOR IDEAL RADIATIONAL COOLING
IN THE CONTINUED COOL AND DRY AIR MASS...TEMPERATURES DROPPED AS
MUCH AS 15 DEGREES IN TWO HOURS EARLY THIS EVENING. CONSIDERING
MINIMUM TEMPERATURES LAST NIGHT AND DEW POINTS RUNNING LOWER AT
MOST LOCATIONS...HAVE NUDGED MINIMUM TEMPERATURES DOWN A COUPLE
DEGREES. WOULD EXPECT TO SEE SOME ISOLATED SUB 40 DEGREE READINGS
IN THE USUAL OUTLYING LOCATIONS.

SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE EXISTS IN PARTS OF EAST
CENTRAL IL AND NORTHWEST IN...AS EVIDENCED BY DEW POINTS AND
EARLIER DAYTIME CUMULUS. THIS PROBABLY WILL ALLOW FOR PATCHY
SHALLOW FOG IN THIS AREA. HAVE ADDED INTO THE FORECAST BUT SHOULD
NOT BE A BIG IMPACT.

MTF

&&

.PREV DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE EARLY THIS EVENING.
* LAKE BREEZE LATE WEDNESDAY AFTERNOON. CMS

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

THE LAKE BREEZE HAS SURGED INLAND AND IS CURRENTLY MOVING WEST
THROUGH ORD/MDW. SPEEDS MAY REACH 8-10KTS WITH ITS PASSAGE BUT
THEN DIMINISH BACK TO 4-6KTS FOR A FEW HOURS. HIGH PRESSURE OVER
THE REGION TONIGHT WILL ALLOW WINDS TO BECOME LIGHT AND VARIABLE
OR CALM BY LATE EVENING. WINDS WILL THEN BECOME LIGHT SOUTHWEST
OR WEST WEDNESDAY MORNING WITH THE WEAK GRADIENT REMAINING AS THE
CENTER OF THE HIGH SHIFTS EAST. ANOTHER LAKE BREEZE SHOULD
DEVELOP WEDNESDAY AFTERNOON...POSSIBLY REACHING ORD/MDW BY LATE
AFTERNOON. CMS

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

* MEDIUM FOR A LAKE BREEZE REACHING ORD/MDW WEDNESDAY AFTERNOON.
  CMS

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 170209 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 PM CDT TUE SEP 16 2014

.DISCUSSION...
908 PM CDT

ONLY MINOR CHANGES MADE TO THE REST OF TONIGHTS FORECAST. WITH
CLEAR SKIES AND LIGHT WINDS ALLOWING FOR IDEAL RADIATIONAL COOLING
IN THE CONTINUED COOL AND DRY AIR MASS...TEMPERATURES DROPPED AS
MUCH AS 15 DEGREES IN TWO HOURS EARLY THIS EVENING. CONSIDERING
MINIMUM TEMPERATURES LAST NIGHT AND DEW POINTS RUNNING LOWER AT
MOST LOCATIONS...HAVE NUDGED MINIMUM TEMPERATURES DOWN A COUPLE
DEGREES. WOULD EXPECT TO SEE SOME ISOLATED SUB 40 DEGREE READINGS
IN THE USUAL OUTLYING LOCATIONS.

SLIGHTLY HIGHER BOUNDARY LAYER MOISTURE EXISTS IN PARTS OF EAST
CENTRAL IL AND NORTHWEST IN...AS EVIDENCED BY DEW POINTS AND
EARLIER DAYTIME CUMULUS. THIS PROBABLY WILL ALLOW FOR PATCHY
SHALLOW FOG IN THIS AREA. HAVE ADDED INTO THE FORECAST BUT SHOULD
NOT BE A BIG IMPACT.

MTF

&&

.PREV DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE EARLY THIS EVENING.
* LAKE BREEZE LATE WEDNESDAY AFTERNOON. CMS

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

THE LAKE BREEZE HAS SURGED INLAND AND IS CURRENTLY MOVING WEST
THROUGH ORD/MDW. SPEEDS MAY REACH 8-10KTS WITH ITS PASSAGE BUT
THEN DIMINISH BACK TO 4-6KTS FOR A FEW HOURS. HIGH PRESSURE OVER
THE REGION TONIGHT WILL ALLOW WINDS TO BECOME LIGHT AND VARIABLE
OR CALM BY LATE EVENING. WINDS WILL THEN BECOME LIGHT SOUTHWEST
OR WEST WEDNESDAY MORNING WITH THE WEAK GRADIENT REMAINING AS THE
CENTER OF THE HIGH SHIFTS EAST. ANOTHER LAKE BREEZE SHOULD
DEVELOP WEDNESDAY AFTERNOON...POSSIBLY REACHING ORD/MDW BY LATE
AFTERNOON. CMS

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

* MEDIUM FOR A LAKE BREEZE REACHING ORD/MDW WEDNESDAY AFTERNOON.
  CMS

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 162342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE EARLY THIS EVENING.
* LAKE BREEZE LATE WEDNESDAY AFTERNOON. CMS

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

THE LAKE BREEZE HAS SURGED INLAND AND IS CURRENTLY MOVING WEST
THROUGH ORD/MDW. SPEEDS MAY REACH 8-10KTS WITH ITS PASSAGE BUT
THEN DIMINISH BACK TO 4-6KTS FOR A FEW HOURS. HIGH PRESSURE OVER
THE REGION TONIGHT WILL ALLOW WINDS TO BECOME LIGHT AND VARIABLE
OR CALM BY LATE EVENING. WINDS WILL THEN BECOME LIGHT SOUTHWEST
OR WEST WEDNESDAY MORNING WITH THE WEAK GRADIENT REMAINING AS THE
CENTER OF THE HIGH SHIFTS EAST. ANOTHER LAKE BREEZE SHOULD
DEVELOP WEDNESDAY AFTERNOON...POSSIBLY REACHING ORD/MDW BY LATE
AFTERNOON. CMS

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

* MEDIUM FOR A LAKE BREEZE REACHING ORD/MDW WEDNESDAY AFTERNOON.
  CMS

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 162342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE EARLY THIS EVENING.
* LAKE BREEZE LATE WEDNESDAY AFTERNOON. CMS

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

THE LAKE BREEZE HAS SURGED INLAND AND IS CURRENTLY MOVING WEST
THROUGH ORD/MDW. SPEEDS MAY REACH 8-10KTS WITH ITS PASSAGE BUT
THEN DIMINISH BACK TO 4-6KTS FOR A FEW HOURS. HIGH PRESSURE OVER
THE REGION TONIGHT WILL ALLOW WINDS TO BECOME LIGHT AND VARIABLE
OR CALM BY LATE EVENING. WINDS WILL THEN BECOME LIGHT SOUTHWEST
OR WEST WEDNESDAY MORNING WITH THE WEAK GRADIENT REMAINING AS THE
CENTER OF THE HIGH SHIFTS EAST. ANOTHER LAKE BREEZE SHOULD
DEVELOP WEDNESDAY AFTERNOON...POSSIBLY REACHING ORD/MDW BY LATE
AFTERNOON. CMS

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

* MEDIUM FOR A LAKE BREEZE REACHING ORD/MDW WEDNESDAY AFTERNOON.
  CMS

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

* THURSDAY AND FRIDAY...DRY/VFR.
* SATURDAY...CHANCE TSRA. GUSTY SOUTHWEST WINDS.
* SUNDAY...SLIGHT CHANCE OF TSRA.
* MONDAY...DRY/VFR.

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 162201
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
501 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* POSSIBLE LAKE BREEZE EARLY THIS EVENING. CMS

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

A WEAK LAKE BREEZE IS SLOWLY MOVING INLAND AND WILL LIKELY REACH
MDW BY 00Z AND POSSIBLY ORD BY 01Z. BUT WIND SPEEDS BEHIND THE
LAKE BREEZE ARE EXPECTED TO BE LESS THEN 8 KTS AND THEN SPEEDS
WILL DIMINISH THIS EVENING. CMS

PREVIOUS 18Z DISCUSSION...

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* MEDIUM FOR LAKE BREEZE REACHING ORD/MDW. CMS

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 162201
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
501 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* POSSIBLE LAKE BREEZE EARLY THIS EVENING. CMS

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

A WEAK LAKE BREEZE IS SLOWLY MOVING INLAND AND WILL LIKELY REACH
MDW BY 00Z AND POSSIBLY ORD BY 01Z. BUT WIND SPEEDS BEHIND THE
LAKE BREEZE ARE EXPECTED TO BE LESS THEN 8 KTS AND THEN SPEEDS
WILL DIMINISH THIS EVENING. CMS

PREVIOUS 18Z DISCUSSION...

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* MEDIUM FOR LAKE BREEZE REACHING ORD/MDW. CMS

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 161957
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE MAY IMPACT KMDW AFTER 22 UTC WITH A VRB OR EAST-
  NORTHEAST WIND DIRECTION. SPEEDS SHOULD BE UNDER 7 KT.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* LOW-MEDIUM FOR LAKE BREEZE MAKING IT TO KMDW AFTER 22 UTC.

* HIGH FOR ALL OTHER ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 161957
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
257 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* LAKE BREEZE MAY IMPACT KMDW AFTER 22 UTC WITH A VRB OR EAST-
  NORTHEAST WIND DIRECTION. SPEEDS SHOULD BE UNDER 7 KT.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* LOW-MEDIUM FOR LAKE BREEZE MAKING IT TO KMDW AFTER 22 UTC.

* HIGH FOR ALL OTHER ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 161954
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
254 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* NONE.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* HIGH FOR ALL ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 161954
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
254 PM CDT TUE SEP 16 2014

.DISCUSSION...
254 PM CDT

TONIGHT...
HIGH PRESSURE HAS BECOME CENTERED OVER THE REGION TODAY...PROVIDING
ABUNDANT SUNSHINE AND LIGHT WINDS. THIS EVENING IS SETTING UP TO BE
A BEAUTIFUL ONE WITH MOSTLY CLEAR SKIES AND NEARLY CALM WINDS FOR
MUCH OF THE OVERNIGHT HOURS. TEMPS WILL RADIATE ONCE AGAIN INTO THE
LOW 40S FOR MUCH OF THE FORECAST AREA...WITH THE EXCEPTION BEING
DOWNTOWN CHICAGO WHERE TEMPS WILL LIKELY HOLD IN THE UPR 40S/ARND
50.

WEDNESDAY THROUGH FRIDAY...
MID-LVL TROUGH WILL REMAIN OVERHEAD THRU WED WITH A CONTINUED LIGHT
NORTHWEST FLOW. AT THE SFC BROAD SFC RIDGING WILL REMAIN IN
PLACE...WITH ABUNDANT SUNSHINE ONCE AGAIN WED AFTN. A BACKDOOR FRONT
WILL SLIP SOUTH ACROSS THE LAKE/NORTHERN GREAT LAKES WED EARLY
MORNING...EVENTUALLY ARRIVING ACROSS NORTHERN IL/NORTHWEST IN LATE
WED NGT/EARLY THUR MORNING. THIS WILL LIKELY PRODUCE AN AREA OF
STRATUS AS IT ARRIVES...HOWEVER AT THIS TIME DRY CONDS ARE EXPECTED
TO PERSIST THRU THUR. THEN ANOTHER SFC RIDGE IS POISED TO SLIDE
SOUTH FROM CENTRAL CANADA...AND LINGER OVER THE REGION THRU EARLY
FRI.

AS THE SFC RIDGE FRI BEGINS TO DRIFT EAST...THE MID-LVL FLOW WILL
BEGIN TO FLATTEN. THIS WILL ALLOW A STEADY TURNING IN THE LLVL FLOW
TO THE SOUTH/SOUTHWEST AND BEGIN ADVECTING WARMER/MOIST AIR INTO THE
REGION FRI NGT. GUIDANCE HAS BEEN STEADILY PUSHING POPS BACK UNTIL
FRI NGT...AND COULD SEE THE SFC RIDGE HOLDING INTO FRI NGT WITH POPS
HOLDING OFF UNTIL EARLY SAT.

TEMPS WED/THUR WILL GENERALLY BE IN THE MID/UPR 60S...WITH A FEW
POINTS POSSIBLY TOUCHING 70 MAINLY SOUTH OF I-80. WITH THE BACKDOOR
FRONT SLIPPING SOUTH IT IS POSSIBLE THE CLOUDS COULD LINGER LONG
ENOUGH THUR THAT TEMPS HOLD IN THE LOW 60S TO POSSIBLY UPR 50S
ACROSS THE NORTHERN IL SECTIONS. THEN FOR FRI TEMPS WILL LIKELY
BEGIN TO CLIMB INTO THE LOW TO POSSIBLY MID 70S. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 40S TO LOW 50S.

CONFIDENCE...HIGH.

SATURDAY THROUGH MONDAY...
ENSEMBLES HAVE COME INTO SLIGHTLY BETTER AGREEMENT IN THE SAT/SUN
TIMEFRAME WITH THE 500MB FLOW REMAINING SOMEWHAT FLAT...WHICH SHOULD
HELP TO BRING THE EXPECTED CHANNEL OF MOISTURE/CONVECTION INTO THE
REGION BUT REMAIN PROGRESSIVE. THEN FOR THE SECOND HALF OF THE
WEEKEND ENSEMBLES RETURN THE MID-LVL RIDGE TO THE WESTERN
CONUS...WITH DOWNSTREAM TROUGHING DEVELOPING OVER THE GREAT LAKES
REGION EARLY NEXT WEEK. IT APPEARS THE BEST DAY FOR CONVECTION WILL
END UP BEING SAT NGT/SUN MORNING. TEMPS WILL LIKELY APPROACH 80 DEG
SAT...AND PERHAPS EVEN THE LOW 80S ACROSS THE SOUTHERN CWFA. HOWEVER
THIS WARM-UP APPEARS TO ONLY BE BRIEF WITH TEMPS SUN BACK INTO THE
LOW 70S AND 60S FOR MON.

CONFIDENCE...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

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

* NONE.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* HIGH FOR ALL ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 161929
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
229 PM CDT TUE SEP 16 2014

.DISCUSSION...
320 AM CDT

SHOULD SEE "CHAMBER OF COMMERCE" TYPE WEATHER FOR THE REMAINDER OF
THE WORK WEEK WITH A GRADUAL WARMING TREND. A PERIOD WARM AND STORMY
WEATHER IS ON TAP FOR THE WEEKEND BEFORE THE TRANSITION TO THE NEXT
COOL DOWN TAKES PLACE TOWARD END OF THE FORECAST CYCLE.

COOL CANADIAN HIGH PRESSURE WILL SLOWLY MOVE EASTWARD ACROSS THE
REGION THIS WEEK BRINGING A CONTINUATION OF BELOW AVERAGE
TEMPERATURES. ON THE PLUS SIDE...LOOKS LIKE THERE WILL BE AMPLE
SUNSHINE AND LITTLE THREAT OF RAIN THROUGH AT LEAST THURSDAY NIGHT
AND PROBABLY THROUGH FRIDAY AS WELL. WARM FRONT IS PROGGED TO MOVE
ACROSS THE REGION FRIDAY...WITH GFS/ECMWF BRINGING IT THROUGH DRY
FOLLOWED BY A BRIEF WARM UP LATER FRIDAY AND ESPECIALLY SATURDAY AS
TRANSIENT UPPER RIDGE MOVES ACROSS THE REGION IN ADVANCE OF
APPROACHING TROUGH. LATEST GFS/ECMWF PROGGED 850MB/925MB TEMPS WOULD
SUPPORT HIGHS IN THE LOW TO MID 80S...BUT A LOT COULD CHANGE BETWEEN
NOW AND THEN SO KEPT HIGHS MORE CONSERVATIVE FOR NOW AND FIGURE WE
CAN TREND TOWARD 80S IN LATER FORECASTS IF LATER RUNS WARRANT DOING
SO.

LATER SATURDAY INTO SATURDAY NIGHT GFS AND ECMWF BOTH PHASE THE
REMNANTS OF EASTERN PACIFIC HURRICANE ODILE WITH A DEEPENING
NORTHERN STRONG SHORTWAVE RESULTING IN PERIOD OF POTENTIALLY HEAVY
SHOWERS AND THUNDERSTORMS ALONG A COLD FRONT. PRETTY COMMON FOR
SIGNIFICANT AMPLIFICATION OF LONG WAVE TROUGHS AS THEY PHASE WITH
REMNANT TROPICAL CYCLONES...AND GFS AND ECMWF BOTH SUGGEST THIS WILL
BE THE CASE EARLY NEXT WEEK WITH THE POTENTIAL FOR ANOTHER
SIGNIFICANT EARLY SEASON COLD SNAP.

IZZI

&&

.AVIATION...

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

* NONE.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* HIGH FOR ALL ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 161929
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
229 PM CDT TUE SEP 16 2014

.DISCUSSION...
320 AM CDT

SHOULD SEE "CHAMBER OF COMMERCE" TYPE WEATHER FOR THE REMAINDER OF
THE WORK WEEK WITH A GRADUAL WARMING TREND. A PERIOD WARM AND STORMY
WEATHER IS ON TAP FOR THE WEEKEND BEFORE THE TRANSITION TO THE NEXT
COOL DOWN TAKES PLACE TOWARD END OF THE FORECAST CYCLE.

COOL CANADIAN HIGH PRESSURE WILL SLOWLY MOVE EASTWARD ACROSS THE
REGION THIS WEEK BRINGING A CONTINUATION OF BELOW AVERAGE
TEMPERATURES. ON THE PLUS SIDE...LOOKS LIKE THERE WILL BE AMPLE
SUNSHINE AND LITTLE THREAT OF RAIN THROUGH AT LEAST THURSDAY NIGHT
AND PROBABLY THROUGH FRIDAY AS WELL. WARM FRONT IS PROGGED TO MOVE
ACROSS THE REGION FRIDAY...WITH GFS/ECMWF BRINGING IT THROUGH DRY
FOLLOWED BY A BRIEF WARM UP LATER FRIDAY AND ESPECIALLY SATURDAY AS
TRANSIENT UPPER RIDGE MOVES ACROSS THE REGION IN ADVANCE OF
APPROACHING TROUGH. LATEST GFS/ECMWF PROGGED 850MB/925MB TEMPS WOULD
SUPPORT HIGHS IN THE LOW TO MID 80S...BUT A LOT COULD CHANGE BETWEEN
NOW AND THEN SO KEPT HIGHS MORE CONSERVATIVE FOR NOW AND FIGURE WE
CAN TREND TOWARD 80S IN LATER FORECASTS IF LATER RUNS WARRANT DOING
SO.

LATER SATURDAY INTO SATURDAY NIGHT GFS AND ECMWF BOTH PHASE THE
REMNANTS OF EASTERN PACIFIC HURRICANE ODILE WITH A DEEPENING
NORTHERN STRONG SHORTWAVE RESULTING IN PERIOD OF POTENTIALLY HEAVY
SHOWERS AND THUNDERSTORMS ALONG A COLD FRONT. PRETTY COMMON FOR
SIGNIFICANT AMPLIFICATION OF LONG WAVE TROUGHS AS THEY PHASE WITH
REMNANT TROPICAL CYCLONES...AND GFS AND ECMWF BOTH SUGGEST THIS WILL
BE THE CASE EARLY NEXT WEEK WITH THE POTENTIAL FOR ANOTHER
SIGNIFICANT EARLY SEASON COLD SNAP.

IZZI

&&

.AVIATION...

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

* NONE.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* HIGH FOR ALL ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
228 PM CDT

HIGH PRESSURE HAS BUILT ACROSS SOUTHERN LAKE MICHIGAN THIS
AFTERNOON. HOWEVER THE SOUTH TO SOUTHWEST GRADIENT HAS INCREASED
ACROSS THE NORTHERN HALF OF THE LAKE AHEAD OF THE NEXT COLD FRONT
OVER LAKE SUPERIOR. THE FRONT WILL SAG SOUTH ACROSS THE
LAKE FOR THE LATTER HALF OF WEDNESDAY INTO WEDNESDAY NIGHT. HIGH
PRESSURE IS RIGHT ON THE HEELS OF THIS FRONT CAUSING A SHARP
INCREASE IN WINDS BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF
THE NORTH-NORTHEAST WEDNESDAY EVENING. EXPECT WINDS WILL BE SLIGHTLY
LESS FARTHER SOUTH AS THE PRESSURE GRADIENT WILL NOT QUITE AS TIGHT
FOR THE SOUTHERN HALF OF THE LAKE. WINDS WILL VEER BACK AROUND TO
THE SOUTHEAST THURSDAY AND THURSDAY NIGHT WHILE DIMINISHING...THEN
BECOME SOUTH TO SOUTHWEST FRIDAY INCREASING INTO THE 25 TO 30 KT
RANGE AS BROAD LOW PRESSURE DEVELOPS OVER THE PLAINS AND CANADIAN
PRAIRIES. WINDS MAY STRENGTHEN TO NEAR GALE FORCE SUNDAY AS THE LOW
STRENGTHENS EAST TOWARD LAKE SUPERIOR THEN SHIFTS EAST.

KMD

&&

.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 161656
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1156 AM CDT TUE SEP 16 2014

.DISCUSSION...
320 AM CDT

SHOULD SEE "CHAMBER OF COMMERCE" TYPE WEATHER FOR THE REMAINDER OF
THE WORK WEEK WITH A GRADUAL WARMING TREND. A PERIOD WARM AND STORMY
WEATHER IS ON TAP FOR THE WEEKEND BEFORE THE TRANSITION TO THE NEXT
COOL DOWN TAKES PLACE TOWARD END OF THE FORECAST CYCLE.

COOL CANADIAN HIGH PRESSURE WILL SLOWLY MOVE EASTWARD ACROSS THE
REGION THIS WEEK BRINGING A CONTINUATION OF BELOW AVERAGE
TEMPERATURES. ON THE PLUS SIDE...LOOKS LIKE THERE WILL BE AMPLE
SUNSHINE AND LITTLE THREAT OF RAIN THROUGH AT LEAST THURSDAY NIGHT
AND PROBABLY THROUGH FRIDAY AS WELL. WARM FRONT IS PROGGED TO MOVE
ACROSS THE REGION FRIDAY...WITH GFS/ECMWF BRINGING IT THROUGH DRY
FOLLOWED BY A BRIEF WARM UP LATER FRIDAY AND ESPECIALLY SATURDAY AS
TRANSIENT UPPER RIDGE MOVES ACROSS THE REGION IN ADVANCE OF
APPROACHING TROUGH. LATEST GFS/ECMWF PROGGED 850MB/925MB TEMPS WOULD
SUPPORT HIGHS IN THE LOW TO MID 80S...BUT A LOT COULD CHANGE BETWEEN
NOW AND THEN SO KEPT HIGHS MORE CONSERVATIVE FOR NOW AND FIGURE WE
CAN TREND TOWARD 80S IN LATER FORECASTS IF LATER RUNS WARRANT DOING
SO.

LATER SATURDAY INTO SATURDAY NIGHT GFS AND ECMWF BOTH PHASE THE
REMNANTS OF EASTERN PACIFIC HURRICANE ODILE WITH A DEEPENING
NORTHERN STRONG SHORTWAVE RESULTING IN PERIOD OF POTENTIALLY HEAVY
SHOWERS AND THUNDERSTORMS ALONG A COLD FRONT. PRETTY COMMON FOR
SIGNIFICANT AMPLIFICATION OF LONG WAVE TROUGHS AS THEY PHASE WITH
REMNANT TROPICAL CYCLONES...AND GFS AND ECMWF BOTH SUGGEST THIS WILL
BE THE CASE EARLY NEXT WEEK WITH THE POTENTIAL FOR ANOTHER
SIGNIFICANT EARLY SEASON COLD SNAP.

IZZI

&&

.AVIATION...

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

* NONE.

KJB

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

AN AREA OF SURFACE HIGH PRESSURE WILL DOMINATE ACROSS THE REGION
THROUGH WEDNESDAY. OVERALL THIS WILL RESULT IN VERY LIGHT
WESTERLY WINDS...MAINLY CLEAR SKIES AND OVERALL NICE WEATHER
THROUGH THE FORECAST PERIOD. AFTERNOON LAKE BREEZES ARE EXPECTED
TODAY AND AGAIN ON WEDNESDAY. HOWEVER...IT APPEARS UNLIKELY THAT
THIS BOUNDARY WILL MAKE IT FAR ENOUGH INLAND TO IMPACT KORD OR
KMDW.

KJB

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

* HIGH FOR ALL ELEMENTS.

KJB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
314 AM CDT

HIGH PRESSURE WILL BUILD ACROSS SOUTHERN LAKE MICHIGAN TODAY
ALLOWING WINDS TO DIMINISH...HOWEVER NORTHERN LAKE MICHIGAN WILL
SEE SOUTHWEST FLOW FRESHEN UP AHEAD OF THE NEXT COLD FRONT. THE
FRONT WILL SAG SOUTH ACROSS THE LAKE WEDNESDAY WITH HIGH PRESSURE
QUICKLY BUILDING IN BEHIND CAUSING A SHARP INCREASE IN WINDS
BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF THE NORTHEAST
WEDNESDAY EVENING. WINDS WILL VEER BACK AROUND TO THE SOUTHEAST
THURSDAY AND THURSDAY NIGHT DIMINISHING...THEN SOUTH TO SOUTHWEST
FRIDAY INCREASING BACK INTO THE 20 TO 25 KT RANGE...POSSIBLY 30 KT
AS BROAD LOW DEVELOPS OVER THE PLAINS AND CANADIAN PRAIRIES.

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 161557
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1057 AM CDT TUE SEP 16 2014

.DISCUSSION...
320 AM CDT

SHOULD SEE "CHAMBER OF COMMERCE" TYPE WEATHER FOR THE REMAINDER OF
THE WORK WEEK WITH A GRADUAL WARMING TREND. A PERIOD WARM AND STORMY
WEATHER IS ON TAP FOR THE WEEKEND BEFORE THE TRANSITION TO THE NEXT
COOL DOWN TAKES PLACE TOWARD END OF THE FORECAST CYCLE.

COOL CANADIAN HIGH PRESSURE WILL SLOWLY MOVE EASTWARD ACROSS THE
REGION THIS WEEK BRINGING A CONTINUATION OF BELOW AVERAGE
TEMPERATURES. ON THE PLUS SIDE...LOOKS LIKE THERE WILL BE AMPLE
SUNSHINE AND LITTLE THREAT OF RAIN THROUGH AT LEAST THURSDAY NIGHT
AND PROBABLY THROUGH FRIDAY AS WELL. WARM FRONT IS PROGGED TO MOVE
ACROSS THE REGION FRIDAY...WITH GFS/ECMWF BRINGING IT THROUGH DRY
FOLLOWED BY A BRIEF WARM UP LATER FRIDAY AND ESPECIALLY SATURDAY AS
TRANSIENT UPPER RIDGE MOVES ACROSS THE REGION IN ADVANCE OF
APPROACHING TROUGH. LATEST GFS/ECMWF PROGGED 850MB/925MB TEMPS WOULD
SUPPORT HIGHS IN THE LOW TO MID 80S...BUT A LOT COULD CHANGE BETWEEN
NOW AND THEN SO KEPT HIGHS MORE CONSERVATIVE FOR NOW AND FIGURE WE
CAN TREND TOWARD 80S IN LATER FORECASTS IF LATER RUNS WARRANT DOING
SO.

LATER SATURDAY INTO SATURDAY NIGHT GFS AND ECMWF BOTH PHASE THE
REMNANTS OF EASTERN PACIFIC HURRICANE ODILE WITH A DEEPENING
NORTHERN STRONG SHORTWAVE RESULTING IN PERIOD OF POTENTIALLY HEAVY
SHOWERS AND THUNDERSTORMS ALONG A COLD FRONT. PRETTY COMMON FOR
SIGNIFICANT AMPLIFICATION OF LONG WAVE TROUGHS AS THEY PHASE WITH
REMNANT TROPICAL CYCLONES...AND GFS AND ECMWF BOTH SUGGEST THIS WILL
BE THE CASE EARLY NEXT WEEK WITH THE POTENTIAL FOR ANOTHER
SIGNIFICANT EARLY SEASON COLD SNAP.

IZZI

&&

.AVIATION...

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

* NONE.

KB

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

HIGH PRESSURE WILL RESULT IN LIGHT WINDS AND PRIMARILY VFR
CONDITIONS THROUGH THE FORECAST PERIOD...WITH THE EXCEPTION OF SOME
PATCHY GROUND FOG DURING THE EARLY MORNING HOURS MAINLY AT THE
OUTLYING TERMINALS. WINDS WILL GENERALLY BE SOME SORT OF
NORTHWESTERLY DIRECTION THROUGH MIDDAY THOUGH THERE WILL LIKELY BE
VARIABILITY DUE TO THE LIGHT MAGNITUDE. WINDS SHOULD FAVOR A MORE
WESTERLY DIRECTION THIS AFTERNOON/EVENING. A LAKE BREEZE IS POSSIBLE
THIS AFTERNOON...THOUGH WEAK THERMAL CONTRAST AND OPPOSING FLOW
SHOULD KEEP IT FROM PUSHING IN ACROSS THE TERMINALS.

BMD

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

* HIGH WITH ALL FORECAST ELEMENTS.

KB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
314 AM CDT

HIGH PRESSURE WILL BUILD ACROSS SOUTHERN LAKE MICHIGAN TODAY
ALLOWING WINDS TO DIMINISH...HOWEVER NORTHERN LAKE MICHIGAN WILL
SEE SOUTHWEST FLOW FRESHEN UP AHEAD OF THE NEXT COLD FRONT. THE
FRONT WILL SAG SOUTH ACROSS THE LAKE WEDNESDAY WITH HIGH PRESSURE
QUICKLY BUILDING IN BEHIND CAUSING A SHARP INCREASE IN WINDS
BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF THE NORTHEAST
WEDNESDAY EVENING. WINDS WILL VEER BACK AROUND TO THE SOUTHEAST
THURSDAY AND THURSDAY NIGHT DIMINISHING...THEN SOUTH TO SOUTHWEST
FRIDAY INCREASING BACK INTO THE 20 TO 25 KT RANGE...POSSIBLY 30 KT
AS BROAD LOW DEVELOPS OVER THE PLAINS AND CANADIAN PRAIRIES.

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 161348
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
848 AM CDT TUE SEP 16 2014

.DISCUSSION...
320 AM CDT

SHOULD SEE "CHAMBER OF COMMERCE" TYPE WEATHER FOR THE REMAINDER OF
THE WORK WEEK WITH A GRADUAL WARMING TREND. A PERIOD WARM AND STORMY
WEATHER IS ON TAP FOR THE WEEKEND BEFORE THE TRANSITION TO THE NEXT
COOL DOWN TAKES PLACE TOWARD END OF THE FORECAST CYCLE.

COOL CANADIAN HIGH PRESSURE WILL SLOWLY MOVE EASTWARD ACROSS THE
REGION THIS WEEK BRINGING A CONTINUATION OF BELOW AVERAGE
TEMPERATURES. ON THE PLUS SIDE...LOOKS LIKE THERE WILL BE AMPLE
SUNSHINE AND LITTLE THREAT OF RAIN THROUGH AT LEAST THURSDAY NIGHT
AND PROBABLY THROUGH FRIDAY AS WELL. WARM FRONT IS PROGGED TO MOVE
ACROSS THE REGION FRIDAY...WITH GFS/ECMWF BRINGING IT THROUGH DRY
FOLLOWED BY A BRIEF WARM UP LATER FRIDAY AND ESPECIALLY SATURDAY AS
TRANSIENT UPPER RIDGE MOVES ACROSS THE REGION IN ADVANCE OF
APPROACHING TROUGH. LATEST GFS/ECMWF PROGGED 850MB/925MB TEMPS WOULD
SUPPORT HIGHS IN THE LOW TO MID 80S...BUT A LOT COULD CHANGE BETWEEN
NOW AND THEN SO KEPT HIGHS MORE CONSERVATIVE FOR NOW AND FIGURE WE
CAN TREND TOWARD 80S IN LATER FORECASTS IF LATER RUNS WARRANT DOING
SO.

LATER SATURDAY INTO SATURDAY NIGHT GFS AND ECMWF BOTH PHASE THE
REMNANTS OF EASTERN PACIFIC HURRICANE ODILE WITH A DEEPENING
NORTHERN STRONG SHORTWAVE RESULTING IN PERIOD OF POTENTIALLY HEAVY
SHOWERS AND THUNDERSTORMS ALONG A COLD FRONT. PRETTY COMMON FOR
SIGNIFICANT AMPLIFICATION OF LONG WAVE TROUGHS AS THEY PHASE WITH
REMNANT TROPICAL CYCLONES...AND GFS AND ECMWF BOTH SUGGEST THIS WILL
BE THE CASE EARLY NEXT WEEK WITH THE POTENTIAL FOR ANOTHER
SIGNIFICANT EARLY SEASON COLD SNAP.

IZZI

&&

.AVIATION...

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

* NONE.

KB

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

HIGH PRESSURE WILL RESULT IN LIGHT WINDS AND PRIMARILY VFR
CONDITIONS THROUGH THE FORECAST PERIOD...WITH THE EXCEPTION OF SOME
PATCHY GROUND FOG DURING THE EARLY MORNING HOURS MAINLY AT THE
OUTLYING TERMINALS. WINDS WILL GENERALLY BE SOME SORT OF
NORTHWESTERLY DIRECTION THROUGH MIDDAY THOUGH THERE WILL LIKELY BE
VARIABILITY DUE TO THE LIGHT MAGNITUDE. WINDS SHOULD FAVOR A MORE
WESTERLY DIRECTION THIS AFTERNOON/EVENING. A LAKE BREEZE IS POSSIBLE
THIS AFTERNOON...THOUGH WEAK THERMAL CONTRAST AND OPPOSING FLOW
SHOULD KEEP IT FROM PUSHING IN ACROSS THE TERMINALS.

BMD

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

* HIGH WITH ALL FORECAST ELEMENTS.

KB

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

WEDNESDAY NIGHT THROUGH FRIDAY...VFR.
SATURDAY...THUNDERSTORMS.
SUNDAY THROUGH MONDAY...VFR.

BMD

&&

.MARINE...
314 AM CDT

HIGH PRESSURE WILL BUILD ACROSS SOUTHERN LAKE MICHIGAN TODAY
ALLOWING WINDS TO DIMINISH...HOWEVER NORTHERN LAKE MICHIGAN WILL
SEE SOUTHWEST FLOW FRESHEN UP AHEAD OF THE NEXT COLD FRONT. THE
FRONT WILL SAG SOUTH ACROSS THE LAKE WEDNESDAY WITH HIGH PRESSURE
QUICKLY BUILDING IN BEHIND CAUSING A SHARP INCREASE IN WINDS
BEHIND THE FRONT INTO THE 20 TO 25 KT RANGE OUT OF THE NORTHEAST
WEDNESDAY EVENING. WINDS WILL VEER BACK AROUND TO THE SOUTHEAST
THURSDAY AND THURSDAY NIGHT DIMINISHING...THEN SOUTH TO SOUTHWEST
FRIDAY INCREASING BACK INTO THE 20 TO 25 KT RANGE...POSSIBLY 30 KT
AS BROAD LOW DEVELOPS OVER THE PLAINS AND CANADIAN PRAIRIES.

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







    US Dept of Commerce
    National Oceanic and Atmospheric Administration
    National Weather Service
    1325 East West Highway
    Silver Spring, MD 20910
    Page Author: NWS Internet Services Team
Disclaimer
Information Quality
Credits
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities