Home > Products > Valid Products > AFD

000
FXUS63 KLOT 241511
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1011 AM CDT FRI OCT 24 2014

.DISCUSSION...
326 AM CDT

SHORT TERM...THROUGH FRIDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO FRIDAY MORNING...THE INITIAL
CONCERN WILL BE CLOUD COVER...AND IMPACTS ON VISIBILITY.  FOLLOWING
THE PASSAGE OF A WEAK SFC TROUGH/PACIFIC-SOURCED WEAK COLD
FRONT...WEAK HIGH PRESSURE HAS BUILT ACROSS THE REGION.  A LOW
STRATUS DECK HAS BEEN IN PLACE FOLLOWING THE FROPA...BUT THE STRATUS
DECK IS ERODING IN PLACES...AND WITH CALM TO LGT/VRBL WINDS IN
PLACE...THE CLEARING LOCATIONS ARE EXPERIENCING RAPID FOG
DEVELOPMENT.  THE FOG IS INITIALLY MOSTLY IMPACTING NWRN IL...ARND
THE ROCKFORD AREA...BUT AS THE STRATUS CONTINUES TO
DISSIPATE...ADDITIONAL FOG MAY DEVELOP...BUT ANY DENSE FOG SHOULD BE
LIMITED TO NORTH CENTRAL AND NWRN IL...AWAY FROM THE CHICAGO METRO
AREA.  EXCEPT FOR LOCATIONS THAT CLEAR OUT...TEMPERATURES SHOULD
GENERALLY BOTTOM OUT IN THE LOWER TO MIDDLE 50S...EXCEPT FOR SOME
ISOLATED...SHELTERED LOW LYING AREAS...WHICH COULD RADIATE DOWN INTO
THE UPPER 40S.

FOR THE REMAINDER OF FRIDAY...THE WARMING TREND SHOULD CONTINUE AS
UPPER RIDGING CONTINUES TO BUILD OUT OF THE ROCKIES AND INTO THE
WESTERN PLAINS.  THE MORNING STRATUS AND STRATOCU SHOULD DISSIPATE
THROUGH THE MORNING HOURS...BUT TOTAL SUNSHINE WILL BE LIMITED AS A
THICK CIRRUS LAYER AND SOME MID LEVEL CLOUDINESS WILL OVERSPREAD THE
REGION THROUGH THIS AFTERNOON AND EVENING AS A STRONG UPPER LEVEL
JET STREAM DIVES OVER THE UPPER MISSISSIPPI VALLEY AND INTO THE
MIDWEST. THE SHORT RANGE GUIDANCE IS ALSO INDICATING SOME SHORTWAVE
ENERGY OVERTOPPING THE RIDGE THIS EVENING...WITH SOME GUIDANCE
INDICATING A LITTLE QPF.  HAVE A HARD TIME INTRODUCING ANY
MENTIONABLE POPS WITH THIS SYSTEM AS MOISTURE PROFILE FORECASTS ALSO
INDICATE LITTLE DEEP LAYER MOISTURE.  HOWEVER...SOME OF THE HIGH RES
SHORT TERM GUIDANCE IS SHOWING SOME INCREASE RH LATE FRIDAY NIGHT
UNDER INCREASINGLY SWLY FLOW...BUT AS FLOW OFF OF THE GULF OF MEXICO
WILL BE LIMITED BY HIGH PRESSURE RIDGING EXTENDING FROM THE CNTRL
APPALACHIANS THROUGH ERN TX...FEEL THAT THIS INCREASED RH COULD BE
MORE INDICATIVE OF SOME FOG POTENTIAL RATHER THAN PCPN POTENTIAL.
AS FOR TEMPERATURES...UNDER INCREASING LOW LEVEL WARM ADVECTION AND
BUILDING HEIGHTS ALOFT...EXPECT THAT TEMPERATURES FOR FRIDAY WILL
LIKELY BE AROUND 5 DEGREES HIGHER THAN THURSDAY WITH HIGHS IN THE
MIDDLE 60S. FRIDAY NIGHT SHOULD REMAIN MILD WITH DEWPOINTS
INCREASING INTO LOWER TO MIDDLE 50S THROUGH FRIDAY AND INTO FRIDAY
EVENING...SO OVERNIGHT LOWS SATURDAY MORNING SHOULD BE UNSEASONABLY
MILD...AND ONLY DROP INTO THE LOWER TO MIDDLE 50S.

KREIN

SATURDAY THROUGH MONDAY...
500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE GREAT LAKES
REGION...WITH A TRAILING FRONTAL BOUNDARY STRETCHING SOUTH AND
EXPECTED TO PUSH EAST ACROSS THE FORECAST AREA SATURDAY MORNING.
MID-LVL HEIGHTS WILL STEADILY RISE AS THE RIDGE PARKED ACROSS THE
CENTRAL CONUS PUSHES EAST...BRINGING MILDER AIR TO THE REGION SAT
WITH HIGHS IN THE MID/UPR 60S. THE FAR SOUTHERN CWFA COULD TOUCH 70
DEG SAT. TEMPS SUN ARE EXPECTED TO BE SLIGHTLY COOLER AS THE FLOW
BEGINS TO TRANSITION BRIEFLY INTO A QUASI-ZONAL SETUP. HOWEVER THIS
DOES NOT LOOK TO REMAIN VERY LONG...AS RIDGING RETURNS FOR MON AND
TEMPS SHUD QUICKLY WARM INTO THE 70S ACROSS MUCH OF THE AREA. A WARM
FRONTAL BOUNDARY WILL LIFT ACROSS THE AREA EARLY MON...AS SOUTHERLY
FLOW STRENGTHENS. EXPECT MUCH OF THE DAY MON TO REMAIN DRY...HOWEVER
LATE AFTN/EVE A DEVELOPING LOW ACROSS THE CENTRAL PLAINS MAY HELP TO
GENERATE A FEW SHOWERS/THUNDERSTORMS LATE MON.

TUESDAY-WEDNESDAY...
TOWARDS THE MIDDLE OF NEXT WEEK ENSEMBLES CONTINUE TO SUGGEST THE
RIDGING OVERHEAD WILL SHIFT EAST...WITH FLOW TRYING TO FLATTEN.
SUGGESTING THAT A SEMI-ZONAL SETUP MAY DEVELOP BY WED...WHICH WILL
LIKELY RESULT IN PERIODIC CHANCES FOR SHOWERS. TEMPS SHUD RETURN TO
MORE SEASONAL CONDS TUE/WED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 15Z...

* MVFR CIGS/VSBY LIKELY AGAIN LATE TONIGHT. IFR CIGS/VSBY POSSIBLE.

MDB

//DISCUSSION...UPDATED 15Z...

CLOUDS CONTINUE TO ERODE FROM PWK TO DPA TO JOT TO PIA AND POINTS
EAST WITH A LARGE GAP IN COVERAGE HAVING DEVELOPED. EXPANSIVE AREA
OF LIFR AND LOWER CIGS/VSBY REMAINS PERSISTENT TO THE WEST. THE
EASTERN FLANK OF THIS HAS SHOWN SOME VERY SLOW DRIFT TO THE EAST
SO AM A LITTLE CONCERNED THAT CLOUDS COULD FILL IN A BIT AGAIN AT
DPA SO WILL KEEP SCATTERED MENTION THERE BUT THE LONGER IT TAKES
FOR ANY CLOUDS TO ARRIVE THERE THE HIGHER THEY WOULD LIKELY BE
THANKS TO SOME WARMING IN THE MEANTIME. OTHERWISE HAVE FURTHER
SLOWED IMPROVEMENT AT RFD AND MAY STILL BE A BIT FAST...ESPECIALLY
SINCE FAIRLY DENSE CIRRUS IS MOVING IN OVERHEAD. OTHERWISE LIGHT
AND VARIABLE SOUTHWEST TO NORTHWEST WINDS ARE EXPECTED.

MDB

FROM 12Z...

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...HOWEVER...AN AREA OF
STRATUS FILTERED IN BEHIND THE WEAK BOUNDARY. LATEST SATELLITE
IMAGERY INDICATES THAT THE STRATUS IS BREAKING UP OVER NRN IL AND
IN LOCATIONS THAT HAD SEEN SOME PCPN YESTERDAY...MAINLY ARND THE
RFD AREA...SOME PATCHY DENSE FOG HAS FORMED...THOUGH OF THE TAF
SITES...ONLY RFD HAS OBSERVED THE DENSE FOG. BASED ON THE LATEST
HIGH RES MODEL GUIDANCE AND SATELLITE TRENDS...ANTICIPATE THAT
CONDITIONS SHOULD IMPROVE TO VFR OVER THE AREA BY LATE MORNING.

ANOTHER SFC TROUGH WILL TRACK ACROSS THE CNTRL PLAINS TO THE
UPPER MISSISSIPPI VALLEY BY EARLY EVENING. WINDS WILL BECOME SSWLY
THOUGH THE DAY...THOUGH WITH A WEAK PRESSURE GRADIENT...WIND
SPEEDS SHOULD BE LESS THAN 10KT THROUGH THE DAY. FOR THE EARLY
EVENING HOURS...A MODEST MID LEVEL IMPULSE IS EXPECTED TO CROSS
THE AREA INVOF THE WI/IL BORDER. THERE IS A CHANCE THAT THIS
SYSTEM COULD TRIGGER SOME ISOLD/SCT -SHRA...BUT CONFIDENCE IN
TIMING AND COVERAGE IS TOO LOW TO INCLUDE PCPN IN THE TAFS AT THIS
TIME. CONFIDENCE IS A LITTLE HIGHER THAT MORE FOG SHOULD DEVELOP
OVERNIGHT TONIGHT...PER THE LATEST HIGH RES MODEL RH
TIME SECTIONS...SO HAVE INTRODUCED IFR VIS FOR LATE THIS EVENING
AND OVERNIGHT. SOME GUIDANCE IS POINTING TOWARD THE POSSIBILITY OF
VIS DROPPING TO 1/4SM...BUT GIVEN THE AMOUNT OF CLOUD COVER
EXPECTED...DO NOT HAVE HIGH ENOUGH CONFIDENCE TO DROP VIS LOWER
THAN 1SM FOR NOW.

KREIN

//ORD AND MDW CONFIDENCE...UPDATED 15Z...

* MEDIUM CONFIDENCE IN CIG TRENDS LATE TONIGHT.

* LOW TO MEDIUM CONFIDENCE IN VSBY TRENDS LATE TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

MDB

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

SATURDAY NIGHT...VFR. WX NIL.

SUNDAY...VFR. WX NIL.

MONDAY...VFR. WX NIL.

MONDAY NIGHT AND TUESDAY...CHANCE SHRA/SLIGHT CHANCE TSRA.

TUESDAY NIGHT...SLIGHT CHANCE SHRA.

WEDNESDAY AND THURSDAY...VFR. WX NIL.

KREIN

&&

.MARINE...
215 AM CDT

A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM WESTERN QUEBEC
SOUTHWEST THROUGH THE CENTRAL GREAT LAKES...INTO THE TENNESSEE
VALLEY. THIS RIDGE WILL CONTINUE TO DRIFT EAST OF THE REGION THIS
AFTERNOON...MEANWHILE A TROUGH OF LOW PRESSURE OVER CENTRAL CANADA
CONTINUES TO SLIDE EAST TOWARDS HUDSON BAY SATURDAY. THE GRADIENT
WILL REMAIN LIGHT THROUGH THIS AFTERNOON...THEN SLOWLY TURN
SOUTH/SOUTHWESTERLY. AS THE LOW NEARS HUDSON BAY ON SATURDAY...A
FRONTAL BOUNDARY WILL TRAIL AND SLOWLY SLIDE SOUTH ACROSS LAKE
MICHIGAN. THIS WILL RESULT IN WINDS TURNING WEST/NORTHWEST
SATURDAY AFTERNOON/EVENING. COOLER AIR WILL FLOW ACROSS THE LAKE
ALONG WITH A TIGHTENING GRADIENT...RESULTING IN INCREASING WINDS
NEARING 30KT AT TIMES. THEN ANOTHER RIDGE OF HIGH PRESSURE WILL
QUICKLY SLIDE SOUTHEAST FROM THE UPPER MIDWEST/NORTHERN PLAINS
SUNDAY...STEADILY DIMINISHING THE GRADIENT. ANOTHER TROUGH OF LOW
PRESSURE IS EXPECTED TO DEVELOP EARLY NEXT WEEK ACROSS THE CENTRAL
PLAINS...THEN APPROACH LAKE MICHIGAN CLOSER TO MID-WEEK. THIS WILL
BRING WINDS BACK TO THE SOUTHWEST WITH OCCASIONALLY WINDS GUSTING
TO 30KT.

BEACHLER

&&

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

$$

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

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







000
FXUS63 KLOT 241409
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 AM CDT FRI OCT 24 2014

.DISCUSSION...
326 AM CDT

SHORT TERM...THROUGH FRIDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO FRIDAY MORNING...THE INITIAL
CONCERN WILL BE CLOUD COVER...AND IMPACTS ON VISIBILITY.  FOLLOWING
THE PASSAGE OF A WEAK SFC TROUGH/PACIFIC-SOURCED WEAK COLD
FRONT...WEAK HIGH PRESSURE HAS BUILT ACROSS THE REGION.  A LOW
STRATUS DECK HAS BEEN IN PLACE FOLLOWING THE FROPA...BUT THE STRATUS
DECK IS ERODING IN PLACES...AND WITH CALM TO LGT/VRBL WINDS IN
PLACE...THE CLEARING LOCATIONS ARE EXPERIENCING RAPID FOG
DEVELOPMENT.  THE FOG IS INITIALLY MOSTLY IMPACTING NWRN IL...ARND
THE ROCKFORD AREA...BUT AS THE STRATUS CONTINUES TO
DISSIPATE...ADDITIONAL FOG MAY DEVELOP...BUT ANY DENSE FOG SHOULD BE
LIMITED TO NORTH CENTRAL AND NWRN IL...AWAY FROM THE CHICAGO METRO
AREA.  EXCEPT FOR LOCATIONS THAT CLEAR OUT...TEMPERATURES SHOULD
GENERALLY BOTTOM OUT IN THE LOWER TO MIDDLE 50S...EXCEPT FOR SOME
ISOLATED...SHELTERED LOW LYING AREAS...WHICH COULD RADIATE DOWN INTO
THE UPPER 40S.

FOR THE REMAINDER OF FRIDAY...THE WARMING TREND SHOULD CONTINUE AS
UPPER RIDGING CONTINUES TO BUILD OUT OF THE ROCKIES AND INTO THE
WESTERN PLAINS.  THE MORNING STRATUS AND STRATOCU SHOULD DISSIPATE
THROUGH THE MORNING HOURS...BUT TOTAL SUNSHINE WILL BE LIMITED AS A
THICK CIRRUS LAYER AND SOME MID LEVEL CLOUDINESS WILL OVERSPREAD THE
REGION THROUGH THIS AFTERNOON AND EVENING AS A STRONG UPPER LEVEL
JET STREAM DIVES OVER THE UPPER MISSISSIPPI VALLEY AND INTO THE
MIDWEST. THE SHORT RANGE GUIDANCE IS ALSO INDICATING SOME SHORTWAVE
ENERGY OVERTOPPING THE RIDGE THIS EVENING...WITH SOME GUIDANCE
INDICATING A LITTLE QPF.  HAVE A HARD TIME INTRODUCING ANY
MENTIONABLE POPS WITH THIS SYSTEM AS MOISTURE PROFILE FORECASTS ALSO
INDICATE LITTLE DEEP LAYER MOISTURE.  HOWEVER...SOME OF THE HIGH RES
SHORT TERM GUIDANCE IS SHOWING SOME INCREASE RH LATE FRIDAY NIGHT
UNDER INCREASINGLY SWLY FLOW...BUT AS FLOW OFF OF THE GULF OF MEXICO
WILL BE LIMITED BY HIGH PRESSURE RIDGING EXTENDING FROM THE CNTRL
APPALACHIANS THROUGH ERN TX...FEEL THAT THIS INCREASED RH COULD BE
MORE INDICATIVE OF SOME FOG POTENTIAL RATHER THAN PCPN POTENTIAL.
AS FOR TEMPERATURES...UNDER INCREASING LOW LEVEL WARM ADVECTION AND
BUILDING HEIGHTS ALOFT...EXPECT THAT TEMPERATURES FOR FRIDAY WILL
LIKELY BE AROUND 5 DEGREES HIGHER THAN THURSDAY WITH HIGHS IN THE
MIDDLE 60S. FRIDAY NIGHT SHOULD REMAIN MILD WITH DEWPOINTS
INCREASING INTO LOWER TO MIDDLE 50S THROUGH FRIDAY AND INTO FRIDAY
EVENING...SO OVERNIGHT LOWS SATURDAY MORNING SHOULD BE UNSEASONABLY
MILD...AND ONLY DROP INTO THE LOWER TO MIDDLE 50S.

KREIN

SATURDAY THROUGH MONDAY...
500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE GREAT LAKES
REGION...WITH A TRAILING FRONTAL BOUNDARY STRETCHING SOUTH AND
EXPECTED TO PUSH EAST ACROSS THE FORECAST AREA SATURDAY MORNING.
MID-LVL HEIGHTS WILL STEADILY RISE AS THE RIDGE PARKED ACROSS THE
CENTRAL CONUS PUSHES EAST...BRINGING MILDER AIR TO THE REGION SAT
WITH HIGHS IN THE MID/UPR 60S. THE FAR SOUTHERN CWFA COULD TOUCH 70
DEG SAT. TEMPS SUN ARE EXPECTED TO BE SLIGHTLY COOLER AS THE FLOW
BEGINS TO TRANSITION BRIEFLY INTO A QUASI-ZONAL SETUP. HOWEVER THIS
DOES NOT LOOK TO REMAIN VERY LONG...AS RIDGING RETURNS FOR MON AND
TEMPS SHUD QUICKLY WARM INTO THE 70S ACROSS MUCH OF THE AREA. A WARM
FRONTAL BOUNDARY WILL LIFT ACROSS THE AREA EARLY MON...AS SOUTHERLY
FLOW STRENGTHENS. EXPECT MUCH OF THE DAY MON TO REMAIN DRY...HOWEVER
LATE AFTN/EVE A DEVELOPING LOW ACROSS THE CENTRAL PLAINS MAY HELP TO
GENERATE A FEW SHOWERS/THUNDERSTORMS LATE MON.

TUESDAY-WEDNESDAY...
TOWARDS THE MIDDLE OF NEXT WEEK ENSEMBLES CONTINUE TO SUGGEST THE
RIDGING OVERHEAD WILL SHIFT EAST...WITH FLOW TRYING TO FLATTEN.
SUGGESTING THAT A SEMI-ZONAL SETUP MAY DEVELOP BY WED...WHICH WILL
LIKELY RESULT IN PERIODIC CHANCES FOR SHOWERS. TEMPS SHUD RETURN TO
MORE SEASONAL CONDS TUE/WED.

BEACHLER

&&

.AVIATION...

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

* MVFR CIGS SCATTERING NEXT 1-2 HRS.

* MVFR CIGS/VSBY LIKELY AGAIN LATE TONIGHT. IFR CIGS/VSBY POSSIBLE.

MDB

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

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...HOWEVER...AN AREA OF
STRATUS FILTERED IN BEHIND THE WEAK BOUNDARY. LATEST SATELLITE
IMAGERY INDICATES THAT THE STRATUS IS BREAKING UP OVER NRN IL AND
IN LOCATIONS THAT HAD SEEN SOME PCPN YESTERDAY...MAINLY ARND THE
RFD AREA...SOME PATCHY DENSE FOG HAS FORMED...THOUGH OF THE TAF
SITES...ONLY RFD HAS OBSERVED THE DENSE FOG. BASED ON THE LATEST
HIGH RES MODEL GUIDANCE AND SATELLITE TRENDS...ANTICIPTE THAT
CONDITIONS SHOULD IMPROVE TO VFR OVER THE AREA BY LATE MORNING.

ANOTHER SFC TROUGH WILL TRACK ACROSS THE CNTRL PLAINS TO THE
UPPER MISSISSIPPI VALLEY BY EARLY EVENING. WINDS WILL BECOME SSWLY
THOUGH THE DAY...THOUGH WITH A WEAK PRESSURE GRADIENT...WIND
SPEEDS SHOULD BE LESS THAN 10KT THROUGH THE DAY. FOR THE EARLY
EVENING HOURS...A MODEST MID LEVEL IMPULSE IS EXPECTED TO CROSS
THE AREA INVOF THE WI/IL BORDER. THERE IS A CHANCE THAT THIS
SYSTEM COULD TRIGGER SOME ISOLD/SCT -SHRA...BUT CONFIDENCE IN
TIMING AND COVERAGE IS TOO LOW TO INCLUDE PCPN IN THE TAFS AT THIS
TIME. CONFIDENCE IS A LITTLE HIGHER THAT MORE FOG SHOULD DEVELOP
OVERNIGHT TONIGHT...PER THE LATEST HIGH RES MODEL RH
TIMESECTIONS...SO HAVE INTRODUCED IFR VIS FOR LATE THIS EVENING
AND OVERNIGHT. SOME GUIDANCE IS POINTING TOWARD THE POSSIBILITY OF
VIS DROPPING TO 1/4SM...BUT GIVEN THE AMOUNT OF CLOUD COVER
EXPECTED...DO NOT HAVE HIGH ENOUGH CONFIDENCE TO DROP VIS LOWER
THAN 1SM FOR NOW.

KREIN

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

* HIGH CONFIDENCE IN CIG TRENDS THIS MORNING.

* MEDIUM CONFIDENCE IN CIG TRENDS LATE TONIGHT.

* LOW TO MEDIUM CONFIDENCE IN VSBY TRENDS LATE TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

MDB

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

SATURDAY NIGHT...VFR. WX NIL.

SUNDAY...VFR. WX NIL.

MONDAY...VFR. WX NIL.

MONDAY NIGHT AND TUESDAY...CHANCE SHRA/SLIGHT CHANCE TSRA.

TUESDAY NIGHT...SLIGHT CHANCE SHRA.

WEDNESDAY AND THURSDAY...VFR. WX NIL.

KREIN

&&

.MARINE...
215 AM CDT

A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM WESTERN QUEBEC
SOUTHWEST THROUGH THE CENTRAL GREAT LAKES...INTO THE TENNESSEE
VALLEY. THIS RIDGE WILL CONTINUE TO DRIFT EAST OF THE REGION THIS
AFTERNOON...MEANWHILE A TROUGH OF LOW PRESSURE OVER CENTRAL CANADA
CONTINUES TO SLIDE EAST TOWARDS HUDSON BAY SATURDAY. THE GRADIENT
WILL REMAIN LIGHT THROUGH THIS AFTERNOON...THEN SLOWLY TURN
SOUTH/SOUTHWESTERLY. AS THE LOW NEARS HUDSON BAY ON SATURDAY...A
FRONTAL BOUNDARY WILL TRAIL AND SLOWLY SLIDE SOUTH ACROSS LAKE
MICHIGAN. THIS WILL RESULT IN WINDS TURNING WEST/NORTHWEST
SATURDAY AFTERNOON/EVENING. COOLER AIR WILL FLOW ACROSS THE LAKE
ALONG WITH A TIGHTENING GRADIENT...RESULTING IN INCREASING WINDS
NEARING 30KT AT TIMES. THEN ANOTHER RIDGE OF HIGH PRESSURE WILL
QUICKLY SLIDE SOUTHEAST FROM THE UPPER MIDWEST/NORTHERN PLAINS
SUNDAY...STEADILY DIMINISHING THE GRADIENT. ANOTHER TROUGH OF LOW
PRESSURE IS EXPECTED TO DEVELOP EARLY NEXT WEEK ACROSS THE CENTRAL
PLAINS...THEN APPROACH LAKE MICHIGAN CLOSER TO MID-WEEK. THIS WILL
BRING WINDS BACK TO THE SOUTHWEST WITH OCCASIONALLY WINDS GUSTING
TO 30KT.

BEACHLER

&&

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

$$

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

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







000
FXUS63 KLOT 241409
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
909 AM CDT FRI OCT 24 2014

.DISCUSSION...
326 AM CDT

SHORT TERM...THROUGH FRIDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO FRIDAY MORNING...THE INITIAL
CONCERN WILL BE CLOUD COVER...AND IMPACTS ON VISIBILITY.  FOLLOWING
THE PASSAGE OF A WEAK SFC TROUGH/PACIFIC-SOURCED WEAK COLD
FRONT...WEAK HIGH PRESSURE HAS BUILT ACROSS THE REGION.  A LOW
STRATUS DECK HAS BEEN IN PLACE FOLLOWING THE FROPA...BUT THE STRATUS
DECK IS ERODING IN PLACES...AND WITH CALM TO LGT/VRBL WINDS IN
PLACE...THE CLEARING LOCATIONS ARE EXPERIENCING RAPID FOG
DEVELOPMENT.  THE FOG IS INITIALLY MOSTLY IMPACTING NWRN IL...ARND
THE ROCKFORD AREA...BUT AS THE STRATUS CONTINUES TO
DISSIPATE...ADDITIONAL FOG MAY DEVELOP...BUT ANY DENSE FOG SHOULD BE
LIMITED TO NORTH CENTRAL AND NWRN IL...AWAY FROM THE CHICAGO METRO
AREA.  EXCEPT FOR LOCATIONS THAT CLEAR OUT...TEMPERATURES SHOULD
GENERALLY BOTTOM OUT IN THE LOWER TO MIDDLE 50S...EXCEPT FOR SOME
ISOLATED...SHELTERED LOW LYING AREAS...WHICH COULD RADIATE DOWN INTO
THE UPPER 40S.

FOR THE REMAINDER OF FRIDAY...THE WARMING TREND SHOULD CONTINUE AS
UPPER RIDGING CONTINUES TO BUILD OUT OF THE ROCKIES AND INTO THE
WESTERN PLAINS.  THE MORNING STRATUS AND STRATOCU SHOULD DISSIPATE
THROUGH THE MORNING HOURS...BUT TOTAL SUNSHINE WILL BE LIMITED AS A
THICK CIRRUS LAYER AND SOME MID LEVEL CLOUDINESS WILL OVERSPREAD THE
REGION THROUGH THIS AFTERNOON AND EVENING AS A STRONG UPPER LEVEL
JET STREAM DIVES OVER THE UPPER MISSISSIPPI VALLEY AND INTO THE
MIDWEST. THE SHORT RANGE GUIDANCE IS ALSO INDICATING SOME SHORTWAVE
ENERGY OVERTOPPING THE RIDGE THIS EVENING...WITH SOME GUIDANCE
INDICATING A LITTLE QPF.  HAVE A HARD TIME INTRODUCING ANY
MENTIONABLE POPS WITH THIS SYSTEM AS MOISTURE PROFILE FORECASTS ALSO
INDICATE LITTLE DEEP LAYER MOISTURE.  HOWEVER...SOME OF THE HIGH RES
SHORT TERM GUIDANCE IS SHOWING SOME INCREASE RH LATE FRIDAY NIGHT
UNDER INCREASINGLY SWLY FLOW...BUT AS FLOW OFF OF THE GULF OF MEXICO
WILL BE LIMITED BY HIGH PRESSURE RIDGING EXTENDING FROM THE CNTRL
APPALACHIANS THROUGH ERN TX...FEEL THAT THIS INCREASED RH COULD BE
MORE INDICATIVE OF SOME FOG POTENTIAL RATHER THAN PCPN POTENTIAL.
AS FOR TEMPERATURES...UNDER INCREASING LOW LEVEL WARM ADVECTION AND
BUILDING HEIGHTS ALOFT...EXPECT THAT TEMPERATURES FOR FRIDAY WILL
LIKELY BE AROUND 5 DEGREES HIGHER THAN THURSDAY WITH HIGHS IN THE
MIDDLE 60S. FRIDAY NIGHT SHOULD REMAIN MILD WITH DEWPOINTS
INCREASING INTO LOWER TO MIDDLE 50S THROUGH FRIDAY AND INTO FRIDAY
EVENING...SO OVERNIGHT LOWS SATURDAY MORNING SHOULD BE UNSEASONABLY
MILD...AND ONLY DROP INTO THE LOWER TO MIDDLE 50S.

KREIN

SATURDAY THROUGH MONDAY...
500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE GREAT LAKES
REGION...WITH A TRAILING FRONTAL BOUNDARY STRETCHING SOUTH AND
EXPECTED TO PUSH EAST ACROSS THE FORECAST AREA SATURDAY MORNING.
MID-LVL HEIGHTS WILL STEADILY RISE AS THE RIDGE PARKED ACROSS THE
CENTRAL CONUS PUSHES EAST...BRINGING MILDER AIR TO THE REGION SAT
WITH HIGHS IN THE MID/UPR 60S. THE FAR SOUTHERN CWFA COULD TOUCH 70
DEG SAT. TEMPS SUN ARE EXPECTED TO BE SLIGHTLY COOLER AS THE FLOW
BEGINS TO TRANSITION BRIEFLY INTO A QUASI-ZONAL SETUP. HOWEVER THIS
DOES NOT LOOK TO REMAIN VERY LONG...AS RIDGING RETURNS FOR MON AND
TEMPS SHUD QUICKLY WARM INTO THE 70S ACROSS MUCH OF THE AREA. A WARM
FRONTAL BOUNDARY WILL LIFT ACROSS THE AREA EARLY MON...AS SOUTHERLY
FLOW STRENGTHENS. EXPECT MUCH OF THE DAY MON TO REMAIN DRY...HOWEVER
LATE AFTN/EVE A DEVELOPING LOW ACROSS THE CENTRAL PLAINS MAY HELP TO
GENERATE A FEW SHOWERS/THUNDERSTORMS LATE MON.

TUESDAY-WEDNESDAY...
TOWARDS THE MIDDLE OF NEXT WEEK ENSEMBLES CONTINUE TO SUGGEST THE
RIDGING OVERHEAD WILL SHIFT EAST...WITH FLOW TRYING TO FLATTEN.
SUGGESTING THAT A SEMI-ZONAL SETUP MAY DEVELOP BY WED...WHICH WILL
LIKELY RESULT IN PERIODIC CHANCES FOR SHOWERS. TEMPS SHUD RETURN TO
MORE SEASONAL CONDS TUE/WED.

BEACHLER

&&

.AVIATION...

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

* MVFR CIGS SCATTERING NEXT 1-2 HRS.

* MVFR CIGS/VSBY LIKELY AGAIN LATE TONIGHT. IFR CIGS/VSBY POSSIBLE.

MDB

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

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...HOWEVER...AN AREA OF
STRATUS FILTERED IN BEHIND THE WEAK BOUNDARY. LATEST SATELLITE
IMAGERY INDICATES THAT THE STRATUS IS BREAKING UP OVER NRN IL AND
IN LOCATIONS THAT HAD SEEN SOME PCPN YESTERDAY...MAINLY ARND THE
RFD AREA...SOME PATCHY DENSE FOG HAS FORMED...THOUGH OF THE TAF
SITES...ONLY RFD HAS OBSERVED THE DENSE FOG. BASED ON THE LATEST
HIGH RES MODEL GUIDANCE AND SATELLITE TRENDS...ANTICIPTE THAT
CONDITIONS SHOULD IMPROVE TO VFR OVER THE AREA BY LATE MORNING.

ANOTHER SFC TROUGH WILL TRACK ACROSS THE CNTRL PLAINS TO THE
UPPER MISSISSIPPI VALLEY BY EARLY EVENING. WINDS WILL BECOME SSWLY
THOUGH THE DAY...THOUGH WITH A WEAK PRESSURE GRADIENT...WIND
SPEEDS SHOULD BE LESS THAN 10KT THROUGH THE DAY. FOR THE EARLY
EVENING HOURS...A MODEST MID LEVEL IMPULSE IS EXPECTED TO CROSS
THE AREA INVOF THE WI/IL BORDER. THERE IS A CHANCE THAT THIS
SYSTEM COULD TRIGGER SOME ISOLD/SCT -SHRA...BUT CONFIDENCE IN
TIMING AND COVERAGE IS TOO LOW TO INCLUDE PCPN IN THE TAFS AT THIS
TIME. CONFIDENCE IS A LITTLE HIGHER THAT MORE FOG SHOULD DEVELOP
OVERNIGHT TONIGHT...PER THE LATEST HIGH RES MODEL RH
TIMESECTIONS...SO HAVE INTRODUCED IFR VIS FOR LATE THIS EVENING
AND OVERNIGHT. SOME GUIDANCE IS POINTING TOWARD THE POSSIBILITY OF
VIS DROPPING TO 1/4SM...BUT GIVEN THE AMOUNT OF CLOUD COVER
EXPECTED...DO NOT HAVE HIGH ENOUGH CONFIDENCE TO DROP VIS LOWER
THAN 1SM FOR NOW.

KREIN

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

* HIGH CONFIDENCE IN CIG TRENDS THIS MORNING.

* MEDIUM CONFIDENCE IN CIG TRENDS LATE TONIGHT.

* LOW TO MEDIUM CONFIDENCE IN VSBY TRENDS LATE TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

MDB

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

SATURDAY NIGHT...VFR. WX NIL.

SUNDAY...VFR. WX NIL.

MONDAY...VFR. WX NIL.

MONDAY NIGHT AND TUESDAY...CHANCE SHRA/SLIGHT CHANCE TSRA.

TUESDAY NIGHT...SLIGHT CHANCE SHRA.

WEDNESDAY AND THURSDAY...VFR. WX NIL.

KREIN

&&

.MARINE...
215 AM CDT

A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM WESTERN QUEBEC
SOUTHWEST THROUGH THE CENTRAL GREAT LAKES...INTO THE TENNESSEE
VALLEY. THIS RIDGE WILL CONTINUE TO DRIFT EAST OF THE REGION THIS
AFTERNOON...MEANWHILE A TROUGH OF LOW PRESSURE OVER CENTRAL CANADA
CONTINUES TO SLIDE EAST TOWARDS HUDSON BAY SATURDAY. THE GRADIENT
WILL REMAIN LIGHT THROUGH THIS AFTERNOON...THEN SLOWLY TURN
SOUTH/SOUTHWESTERLY. AS THE LOW NEARS HUDSON BAY ON SATURDAY...A
FRONTAL BOUNDARY WILL TRAIL AND SLOWLY SLIDE SOUTH ACROSS LAKE
MICHIGAN. THIS WILL RESULT IN WINDS TURNING WEST/NORTHWEST
SATURDAY AFTERNOON/EVENING. COOLER AIR WILL FLOW ACROSS THE LAKE
ALONG WITH A TIGHTENING GRADIENT...RESULTING IN INCREASING WINDS
NEARING 30KT AT TIMES. THEN ANOTHER RIDGE OF HIGH PRESSURE WILL
QUICKLY SLIDE SOUTHEAST FROM THE UPPER MIDWEST/NORTHERN PLAINS
SUNDAY...STEADILY DIMINISHING THE GRADIENT. ANOTHER TROUGH OF LOW
PRESSURE IS EXPECTED TO DEVELOP EARLY NEXT WEEK ACROSS THE CENTRAL
PLAINS...THEN APPROACH LAKE MICHIGAN CLOSER TO MID-WEEK. THIS WILL
BRING WINDS BACK TO THE SOUTHWEST WITH OCCASIONALLY WINDS GUSTING
TO 30KT.

BEACHLER

&&

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

$$

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

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







000
FXUS63 KLOT 241159
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
659 AM CDT FRI OCT 24 2014

.DISCUSSION...
326 AM CDT

SHORT TERM...THROUGH FRIDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO FRIDAY MORNING...THE INITIAL
CONCERN WILL BE CLOUD COVER...AND IMPACTS ON VISIBILITY.  FOLLOWING
THE PASSAGE OF A WEAK SFC TROUGH/PACIFIC-SOURCED WEAK COLD
FRONT...WEAK HIGH PRESSURE HAS BUILT ACROSS THE REGION.  A LOW
STRATUS DECK HAS BEEN IN PLACE FOLLOWING THE FROPA...BUT THE STRATUS
DECK IS ERODING IN PLACES...AND WITH CALM TO LGT/VRBL WINDS IN
PLACE...THE CLEARING LOCATIONS ARE EXPERIENCING RAPID FOG
DEVELOPMENT.  THE FOG IS INITIALLY MOSTLY IMPACTING NWRN IL...ARND
THE ROCKFORD AREA...BUT AS THE STRATUS CONTINUES TO
DISSIPATE...ADDITIONAL FOG MAY DEVELOP...BUT ANY DENSE FOG SHOULD BE
LIMITED TO NORTH CENTRAL AND NWRN IL...AWAY FROM THE CHICAGO METRO
AREA.  EXCEPT FOR LOCATIONS THAT CLEAR OUT...TEMPERATURES SHOULD
GENERALLY BOTTOM OUT IN THE LOWER TO MIDDLE 50S...EXCEPT FOR SOME
ISOLATED...SHELTERED LOW LYING AREAS...WHICH COULD RADIATE DOWN INTO
THE UPPER 40S.

FOR THE REMAINDER OF FRIDAY...THE WARMING TREND SHOULD CONTINUE AS
UPPER RIDGING CONTINUES TO BUILD OUT OF THE ROCKIES AND INTO THE
WESTERN PLAINS.  THE MORNING STRATUS AND STRATOCU SHOULD DISSIPATE
THROUGH THE MORNING HOURS...BUT TOTAL SUNSHINE WILL BE LIMITED AS A
THICK CIRRUS LAYER AND SOME MID LEVEL CLOUDINESS WILL OVERSPREAD THE
REGION THROUGH THIS AFTERNOON AND EVENING AS A STRONG UPPER LEVEL
JET STREAM DIVES OVER THE UPPER MISSISSIPPI VALLEY AND INTO THE
MIDWEST. THE SHORT RANGE GUIDANCE IS ALSO INDICATING SOME SHORTWAVE
ENERGY OVERTOPPING THE RIDGE THIS EVENING...WITH SOME GUIDANCE
INDICATING A LITTLE QPF.  HAVE A HARD TIME INTRODUCING ANY
MENTIONABLE POPS WITH THIS SYSTEM AS MOISTURE PROFILE FORECASTS ALSO
INDICATE LITTLE DEEP LAYER MOISTURE.  HOWEVER...SOME OF THE HIGH RES
SHORT TERM GUIDANCE IS SHOWING SOME INCREASE RH LATE FRIDAY NIGHT
UNDER INCREASINGLY SWLY FLOW...BUT AS FLOW OFF OF THE GULF OF MEXICO
WILL BE LIMITED BY HIGH PRESSURE RIDGING EXTENDING FROM THE CNTRL
APPALACHIANS THROUGH ERN TX...FEEL THAT THIS INCREASED RH COULD BE
MORE INDICATIVE OF SOME FOG POTENTIAL RATHER THAN PCPN POTENTIAL.
AS FOR TEMPERATURES...UNDER INCREASING LOW LEVEL WARM ADVECTION AND
BUILDING HEIGHTS ALOFT...EXPECT THAT TEMPERATURES FOR FRIDAY WILL
LIKELY BE AROUND 5 DEGREES HIGHER THAN THURSDAY WITH HIGHS IN THE
MIDDLE 60S. FRIDAY NIGHT SHOULD REMAIN MILD WITH DEWPOINTS
INCREASING INTO LOWER TO MIDDLE 50S THROUGH FRIDAY AND INTO FRIDAY
EVENING...SO OVERNIGHT LOWS SATURDAY MORNING SHOULD BE UNSEASONABLY
MILD...AND ONLY DROP INTO THE LOWER TO MIDDLE 50S.

KREIN

SATURDAY THROUGH MONDAY...
500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE GREAT LAKES
REGION...WITH A TRAILING FRONTAL BOUNDARY STRETCHING SOUTH AND
EXPECTED TO PUSH EAST ACROSS THE FORECAST AREA SATURDAY MORNING.
MID-LVL HEIGHTS WILL STEADILY RISE AS THE RIDGE PARKED ACROSS THE
CENTRAL CONUS PUSHES EAST...BRINGING MILDER AIR TO THE REGION SAT
WITH HIGHS IN THE MID/UPR 60S. THE FAR SOUTHERN CWFA COULD TOUCH 70
DEG SAT. TEMPS SUN ARE EXPECTED TO BE SLIGHTLY COOLER AS THE FLOW
BEGINS TO TRANSITION BRIEFLY INTO A QUASI-ZONAL SETUP. HOWEVER THIS
DOES NOT LOOK TO REMAIN VERY LONG...AS RIDGING RETURNS FOR MON AND
TEMPS SHUD QUICKLY WARM INTO THE 70S ACROSS MUCH OF THE AREA. A WARM
FRONTAL BOUNDARY WILL LIFT ACROSS THE AREA EARLY MON...AS SOUTHERLY
FLOW STRENGTHENS. EXPECT MUCH OF THE DAY MON TO REMAIN DRY...HOWEVER
LATE AFTN/EVE A DEVELOPING LOW ACROSS THE CENTRAL PLAINS MAY HELP TO
GENERATE A FEW SHOWERS/THUNDERSTORMS LATE MON.

TUESDAY-WEDNESDAY...
TOWARDS THE MIDDLE OF NEXT WEEK ENSEMBLES CONTINUE TO SUGGEST THE
RIDGING OVERHEAD WILL SHIFT EAST...WITH FLOW TRYING TO FLATTEN.
SUGGESTING THAT A SEMI-ZONAL SETUP MAY DEVELOP BY WED...WHICH WILL
LIKELY RESULT IN PERIODIC CHANCES FOR SHOWERS. TEMPS SHUD RETURN TO
MORE SEASONAL CONDS TUE/WED.

BEACHLER

&&

.AVIATION...

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

* MVFR CIGS POSSIBLE THROUGH LATE MORNING.

* MVFR CIGS/VIS LIKELY AGAIN LATE TONIGHT. IFR CIGS/VIS POSSIBLE.

KREIN

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

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...HOWEVER...AN AREA OF
STRATUS FILTERED IN BEHIND THE WEAK BOUNDARY. LATEST SATELLITE
IMAGERY INDICATES THAT THE STRATUS IS BREAKING UP OVER NRN IL AND
IN LOCATIONS THAT HAD SEEN SOME PCPN YESTERDAY...MAINLY ARND THE
RFD AREA...SOME PATCHY DENSE FOG HAS FORMED...THOUGH OF THE TAF
SITES...ONLY RFD HAS OBSERVED THE DENSE FOG. BASED ON THE LATEST
HIGH RES MODEL GUIDANCE AND SATELLITE TRENDS...ANTICIPTE THAT
CONDITIONS SHOULD IMPROVE TO VFR OVER THE AREA BY LATE MORNING.

ANOTHER SFC TROUGH WILL TRACK ACROSS THE CNTRL PLAINS TO THE
UPPER MISSISSIPPI VALLEY BY EARLY EVENING. WINDS WILL BECOME SSWLY
THOUGH THE DAY...THOUGH WITH A WEAK PRESSURE GRADIENT...WIND
SPEEDS SHOULD BE LESS THAN 10KT THROUGH THE DAY. FOR THE EARLY
EVENING HOURS...A MODEST MID LEVEL IMPULSE IS EXPECTED TO CROSS
THE AREA INVOF THE WI/IL BORDER. THERE IS A CHANCE THAT THIS
SYSTEM COULD TRIGGER SOME ISOLD/SCT -SHRA...BUT CONFIDENCE IN
TIMING AND COVERAGE IS TOO LOW TO INCLUDE PCPN IN THE TAFS AT THIS
TIME. CONFIDENCE IS A LITTLE HIGHER THAT MORE FOG SHOULD DEVELOP
OVERNIGHT TONIGHT...PER THE LATEST HIGH RES MODEL RH
TIMESECTIONS...SO HAVE INTRODUCED IFR VIS FOR LATE THIS EVENING
AND OVERNIGHT. SOME GUIDANCE IS POINTING TOWARD THE POSSIBILITY OF
VIS DROPPING TO 1/4SM...BUT GIVEN THE AMOUNT OF CLOUD COVER
EXPECTED...DO NOT HAVE HIGH ENOUGH CONFIDENCE TO DROP VIS LOWER
THAN 1SM FOR NOW.

KREIN


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

* MEDIUM TO HIGH CONFIDENCE IN CIG TRENDS THIS MORNING.

* MEDIUM CONFIDENCE IN CIG TRENDS LATE TONIGHT.

* LOW TO MEDIUM CONFIDENCE IN VIS TRENDS LATE TONIGHT.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

KREIN

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

SATURDAY NIGHT...VFR. WX NIL.

SUNDAY...VFR. WX NIL.

MONDAY...VFR. WX NIL.

MONDAY NIGHT AND TUESDAY...CHANCE SHRA/SLIGHT CHANCE TSRA.

TUESDAY NIGHT...SLIGHT CHANCE SHRA.

WEDNESDAY AND THURSDAY...VFR. WX NIL.

KREIN

&&

.MARINE...
215 AM CDT

A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM WESTERN QUEBEC
SOUTHWEST THROUGH THE CENTRAL GREAT LAKES...INTO THE TENNESSEE
VALLEY. THIS RIDGE WILL CONTINUE TO DRIFT EAST OF THE REGION THIS
AFTERNOON...MEANWHILE A TROUGH OF LOW PRESSURE OVER CENTRAL CANADA
CONTINUES TO SLIDE EAST TOWARDS HUDSON BAY SATURDAY. THE GRADIENT
WILL REMAIN LIGHT THROUGH THIS AFTERNOON...THEN SLOWLY TURN
SOUTH/SOUTHWESTERLY. AS THE LOW NEARS HUDSON BAY ON SATURDAY...A
FRONTAL BOUNDARY WILL TRAIL AND SLOWLY SLIDE SOUTH ACROSS LAKE
MICHIGAN. THIS WILL RESULT IN WINDS TURNING WEST/NORTHWEST
SATURDAY AFTERNOON/EVENING. COOLER AIR WILL FLOW ACROSS THE LAKE
ALONG WITH A TIGHTENING GRADIENT...RESULTING IN INCREASING WINDS
NEARING 30KT AT TIMES. THEN ANOTHER RIDGE OF HIGH PRESSURE WILL
QUICKLY SLIDE SOUTHEAST FROM THE UPPER MIDWEST/NORTHERN PLAINS
SUNDAY...STEADILY DIMINISHING THE GRADIENT. ANOTHER TROUGH OF LOW
PRESSURE IS EXPECTED TO DEVELOP EARLY NEXT WEEK ACROSS THE CENTRAL
PLAINS...THEN APPROACH LAKE MICHIGAN CLOSER TO MID-WEEK. THIS WILL
BRING WINDS BACK TO THE SOUTHWEST WITH OCCASIONALLY WINDS GUSTING
TO 30KT.

BEACHLER

&&

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

$$

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

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







000
FXUS63 KLOT 240903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
403 AM CDT FRI OCT 24 2014

.DISCUSSION...
326 AM CDT

SHORT TERM...THROUGH FRIDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO FRIDAY MORNING...THE INITIAL
CONCERN WILL BE CLOUD COVER...AND IMPACTS ON VISIBILITY.  FOLLOWING
THE PASSAGE OF A WEAK SFC TROUGH/PACIFIC-SOURCED WEAK COLD
FRONT...WEAK HIGH PRESSURE HAS BUILT ACROSS THE REGION.  A LOW
STRATUS DECK HAS BEEN IN PLACE FOLLOWING THE FROPA...BUT THE STRATUS
DECK IS ERODING IN PLACES...AND WITH CALM TO LGT/VRBL WINDS IN
PLACE...THE CLEARING LOCATIONS ARE EXPERIENCING RAPID FOG
DEVELOPMENT.  THE FOG IS INITIALLY MOSTLY IMPACTING NWRN IL...ARND
THE ROCKFORD AREA...BUT AS THE STRATUS CONTINUES TO
DISSIPATE...ADDITIONAL FOG MAY DEVELOP...BUT ANY DENSE FOG SHOULD BE
LIMITED TO NORTH CENTRAL AND NWRN IL...AWAY FROM THE CHICAGO METRO
AREA.  EXCEPT FOR LOCATIONS THAT CLEAR OUT...TEMPERATURES SHOULD
GENERALLY BOTTOM OUT IN THE LOWER TO MIDDLE 50S...EXCEPT FOR SOME
ISOLATED...SHELTERED LOW LYING AREAS...WHICH COULD RADIATE DOWN INTO
THE UPPER 40S.

FOR THE REMAINDER OF FRIDAY...THE WARMING TREND SHOULD CONTINUE AS
UPPER RIDGING CONTINUES TO BUILD OUT OF THE ROCKIES AND INTO THE
WESTERN PLAINS.  THE MORNING STRATUS AND STRATOCU SHOULD DISSIPATE
THROUGH THE MORNING HOURS...BUT TOTAL SUNSHINE WILL BE LIMITED AS A
THICK CIRRUS LAYER AND SOME MID LEVEL CLOUDINESS WILL OVERSPREAD THE
REGION THROUGH THIS AFTERNOON AND EVENING AS A STRONG UPPER LEVEL
JET STREAM DIVES OVER THE UPPER MISSISSIPPI VALLEY AND INTO THE
MIDWEST. THE SHORT RANGE GUIDANCE IS ALSO INDICATING SOME SHORTWAVE
ENERGY OVERTOPPING THE RIDGE THIS EVENING...WITH SOME GUIDANCE
INDICATING A LITTLE QPF.  HAVE A HARD TIME INTRODUCING ANY
MENTIONABLE POPS WITH THIS SYSTEM AS MOISTURE PROFILE FORECASTS ALSO
INDICATE LITTLE DEEP LAYER MOISTURE.  HOWEVER...SOME OF THE HIGH RES
SHORT TERM GUIDANCE IS SHOWING SOME INCREASE RH LATE FRIDAY NIGHT
UNDER INCREASINGLY SWLY FLOW...BUT AS FLOW OFF OF THE GULF OF MEXICO
WILL BE LIMITED BY HIGH PRESSURE RIDGING EXTENDING FROM THE CNTRL
APPALACHIANS THROUGH ERN TX...FEEL THAT THIS INCREASED RH COULD BE
MORE INDICATIVE OF SOME FOG POTENTIAL RATHER THAN PCPN POTENTIAL.
AS FOR TEMPERATURES...UNDER INCREASING LOW LEVEL WARM ADVECTION AND
BUILDING HEIGHTS ALOFT...EXPECT THAT TEMPERATURES FOR FRIDAY WILL
LIKELY BE AROUND 5 DEGREES HIGHER THAN THURSDAY WITH HIGHS IN THE
MIDDLE 60S. FRIDAY NIGHT SHOULD REMAIN MILD WITH DEWPOINTS
INCREASING INTO LOWER TO MIDDLE 50S THROUGH FRIDAY AND INTO FRIDAY
EVENING...SO OVERNIGHT LOWS SATURDAY MORNING SHOULD BE UNSEASONABLY
MILD...AND ONLY DROP INTO THE LOWER TO MIDDLE 50S.

KREIN

SATURDAY THROUGH MONDAY...
500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE GREAT LAKES
REGION...WITH A TRAILING FRONTAL BOUNDARY STRETCHING SOUTH AND
EXPECTED TO PUSH EAST ACROSS THE FORECAST AREA SATURDAY MORNING.
MID-LVL HEIGHTS WILL STEADILY RISE AS THE RIDGE PARKED ACROSS THE
CENTRAL CONUS PUSHES EAST...BRINGING MILDER AIR TO THE REGION SAT
WITH HIGHS IN THE MID/UPR 60S. THE FAR SOUTHERN CWFA COULD TOUCH 70
DEG SAT. TEMPS SUN ARE EXPECTED TO BE SLIGHTLY COOLER AS THE FLOW
BEGINS TO TRANSITION BRIEFLY INTO A QUASI-ZONAL SETUP. HOWEVER THIS
DOES NOT LOOK TO REMAIN VERY LONG...AS RIDGING RETURNS FOR MON AND
TEMPS SHUD QUICKLY WARM INTO THE 70S ACROSS MUCH OF THE AREA. A WARM
FRONTAL BOUNDARY WILL LIFT ACROSS THE AREA EARLY MON...AS SOUTHERLY
FLOW STRENGTHENS. EXPECT MUCH OF THE DAY MON TO REMAIN DRY...HOWEVER
LATE AFTN/EVE A DEVELOPING LOW ACROSS THE CENTRAL PLAINS MAY HELP TO
GENERATE A FEW SHOWERS/THUNDERSTORMS LATE MON.

TUESDAY-WEDNESDAY...
TOWARDS THE MIDDLE OF NEXT WEEK ENSEMBLES CONTINUE TO SUGGEST THE
RIDGING OVERHEAD WILL SHIFT EAST...WITH FLOW TRYING TO FLATTEN.
SUGGESTING THAT A SEMI-ZONAL SETUP MAY DEVELOP BY WED...WHICH WILL
LIKELY RESULT IN PERIODIC CHANCES FOR SHOWERS. TEMPS SHUD RETURN TO
MORE SEASONAL CONDS TUE/WED.

BEACHLER

&&

.AVIATION...

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

* MVFR CIGS DURG THE EARLY MORNING HOURS. CHANCE CIGS MAY SCT AND
  VIS MAY DROP TO MVFR LEVELS.

KREIN

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

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...ANY RESIDUAL PCPN
REMAINS ISOLD AND SOUTH OF THE TERMINALS. HOWEVER...THERE IS SOLE
RESIDUAL LOW LEVEL MOISTURE AND AS HIGH CLOUD PUSHES AWAY...A BAND
OF STRATUS CAN BE SEEN IN THE LATEST SATELLITE IMAGERY. AS A
NOCTURNAL SUBSIDENCE INVERSION LOWERS OVERNIGHT...CLOUD BASES
SHOULD GRADUALLY LOWER TO LOWER END MVFR LEVELS. THERE IS A CHANCE
FOR SOME PATCHY IFR CIGS DURG THE EARLY MORNING HOURS...ESPECIALLY
OVER NWRN IL WHERE SOME RAIN FELL EARLIER...WHICH WOULD MOST
LIKELY AFFECT RFD AND POSSIBLY DPA. AS WINDS BECM LGT/VRBL
OVERNIGHT...VIS SHOULD DROP TO 3-5SM DURG THE EARLY MORNING
HOURS...AND IF THE WESTERN EDGE OF THE STRATUS DECK CAN ERODE OVER
NWRN IL BEFORE SUNRISE...THERE IS A CHANCE FOR RFD TO DROP INTO
IFR OR EVEN LIFR VIS LEVELS. HOWEVER...THAT WOULD BE HIGHLY
DEPENDENT ON THE CIG TRENDS.

THROUGH THE DAY ON FRIDAY...ANOTHER SFC TROUGH WILL TRACK ACROSS
THE CNTRL PLAINS TO THE UPPER MISSISSIPPI VALLEY BY EARLY EVENING.
WINDS WILL BECOME SSWLY THOUGH THE DAY...THOUGH WITH A WEAK
PRESSURE GRADIENT...WIND SPEEDS SHOULD BE LESS THAN 10KT THROUGH
THE DAY. FOR THE EARLY EVENING HOURS...SOME OF THE MODELS ARE
SUGGESTING THAT THERE COULD BE SOME LIGHT PCPN WITH THE PASSAGE OF
THE NEXT SFC TROUGH. HOWEVER...SINCE FORCING WITH THIS TROUGH AXIS
LOOKS TO BE RATHER WEAK...CONFIDENCE IS TOO LOW TO ADD PCPN TO THE
TAFS AT THIS TIME.

KREIN

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

* MEDIUM CONFIDENCE IN CIG/VIS TRENDS OVERNIGHT.

* LOW CONFIDENCE IN SPECIFIC TIMING OF IMPROVEMENT TO VFR FRIDAY.

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE DAY ON
  FRIDAY.

* LOW CONFIDENCE IN THE CHANCES FOR PCPN FRIDAY EVENING.

KREIN

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
215 AM CDT

A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM WESTERN QUEBEC
SOUTHWEST THROUGH THE CENTRAL GREAT LAKES...INTO THE TENNESSEE
VALLEY. THIS RIDGE WILL CONTINUE TO DRIFT EAST OF THE REGION THIS
AFTERNOON...MEANWHILE A TROUGH OF LOW PRESSURE OVER CENTRAL CANADA
CONTINUES TO SLIDE EAST TOWARDS HUDSON BAY SATURDAY. THE GRADIENT
WILL REMAIN LIGHT THROUGH THIS AFTERNOON...THEN SLOWLY TURN
SOUTH/SOUTHWESTERLY. AS THE LOW NEARS HUDSON BAY ON SATURDAY...A
FRONTAL BOUNDARY WILL TRAIL AND SLOWLY SLIDE SOUTH ACROSS LAKE
MICHIGAN. THIS WILL RESULT IN WINDS TURNING WEST/NORTHWEST
SATURDAY AFTERNOON/EVENING. COOLER AIR WILL FLOW ACROSS THE LAKE
ALONG WITH A TIGHTENING GRADIENT...RESULTING IN INCREASING WINDS
NEARING 30KT AT TIMES. THEN ANOTHER RIDGE OF HIGH PRESSURE WILL
QUICKLY SLIDE SOUTHEAST FROM THE UPPER MIDWEST/NORTHERN PLAINS
SUNDAY...STEADILY DIMINISHING THE GRADIENT. ANOTHER TROUGH OF LOW
PRESSURE IS EXPECTED TO DEVELOP EARLY NEXT WEEK ACROSS THE CENTRAL
PLAINS...THEN APPROACH LAKE MICHIGAN CLOSER TO MID-WEEK. THIS WILL
BRING WINDS BACK TO THE SOUTHWEST WITH OCCASIONALLY WINDS GUSTING
TO 30KT.

BEACHLER

&&

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

$$

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

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







000
FXUS63 KLOT 240827
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
327 AM CDT FRI OCT 24 2014

.DISCUSSION...
326 AM CDT

SHORT TERM...THROUGH FRIDAY NIGHT...
FOR THE REMAINDER OF THE NIGHT AND INTO FRIDAY MORNING...THE INITIAL
CONCERN WILL BE CLOUD COVER...AND IMPACTS ON VISIBILITY.  FOLLOWING
THE PASSAGE OF A WEAK SFC TROUGH/PACIFIC-SOURCED WEAK COLD
FRONT...WEAK HIGH PRESSURE HAS BUILT ACROSS THE REGION.  A LOW
STRATUS DECK HAS BEEN IN PLACE FOLLOWING THE FROPA...BUT THE STRATUS
DECK IS ERODING IN PLACES...AND WITH CALM TO LGT/VRBL WINDS IN
PLACE...THE CLEARING LOCATIONS ARE EXPERIENCING RAPID FOG
DEVELOPMENT.  THE FOG IS INITIALLY MOSTLY IMPACTING NWRN IL...ARND
THE ROCKFORD AREA...BUT AS THE STRATUS CONTINUES TO
DISSIPATE...ADDITIONAL FOG MAY DEVELOP...BUT ANY DENSE FOG SHOULD BE
LIMITED TO NORTH CENTRAL AND NWRN IL...AWAY FROM THE CHICAGO METRO
AREA.  EXCEPT FOR LOCATIONS THAT CLEAR OUT...TEMPERATURES SHOULD
GENERALLY BOTTOM OUT IN THE LOWER TO MIDDLE 50S...EXCEPT FOR SOME
ISOLATED...SHELTERED LOW LYING AREAS...WHICH COULD RADIATE DOWN INTO
THE UPPER 40S.

FOR THE REMAINDER OF FRIDAY...THE WARMING TREND SHOULD CONTINUE AS
UPPER RIDGING CONTINUES TO BUILD OUT OF THE ROCKIES AND INTO THE
WESTERN PLAINS.  THE MORNING STRATUS AND STRATOCU SHOULD DISSIPATE
THROUGH THE MORNING HOURS...BUT TOTAL SUNSHINE WILL BE LIMITED AS A
THICK CIRRUS LAYER AND SOME MID LEVEL CLOUDINESS WILL OVERSPREAD THE
REGION THROUGH THIS AFTERNOON AND EVENING AS A STRONG UPPER LEVEL
JET STREAM DIVES OVER THE UPPER MISSISSIPPI VALLEY AND INTO THE
MIDWEST. THE SHORT RANGE GUIDANCE IS ALSO INDICATING SOME SHORTWAVE
ENERGY OVERTOPPING THE RIDGE THIS EVENING...WITH SOME GUIDANCE
INDICATING A LITTLE QPF.  HAVE A HARD TIME INTRODUCING ANY
MENTIONABLE POPS WITH THIS SYSTEM AS MOISTURE PROFILE FORECASTS ALSO
INDICATE LITTLE DEEP LAYER MOISTURE.  HOWEVER...SOME OF THE HIGH RES
SHORT TERM GUIDANCE IS SHOWING SOME INCREASE RH LATE FRIDAY NIGHT
UNDER INCREASINGLY SWLY FLOW...BUT AS FLOW OFF OF THE GULF OF MEXICO
WILL BE LIMITED BY HIGH PRESSURE RIDGING EXTENDING FROM THE CNTRL
APPALACHIANS THROUGH ERN TX...FEEL THAT THIS INCREASED RH COULD BE
MORE INDICATIVE OF SOME FOG POTENTIAL RATHER THAN PCPN POTENTIAL.
AS FOR TEMPERATURES...UNDER INCREASING LOW LEVEL WARM ADVECTION AND
BUILDING HEIGHTS ALOFT...EXPECT THAT TEMPERATURES FOR FRIDAY WILL
LIKELY BE AROUND 5 DEGREES HIGHER THAN THURSDAY WITH HIGHS IN THE
MIDDLE 60S. FRIDAY NIGHT SHOULD REMAIN MILD WITH DEWPOINTS
INCREASING INTO LOWER TO MIDDLE 50S THROUGH FRIDAY AND INTO FRIDAY
EVENING...SO OVERNIGHT LOWS SATURDAY MORNING SHOULD BE UNSEASONABLY
MILD...AND ONLY DROP INTO THE LOWER TO MIDDLE 50S.

KREIN

SATURDAY THROUGH MONDAY...
500MB TROUGH AXIS WILL BE PIVOTING EAST ACROSS THE GREAT LAKES
REGION...WITH A TRAILING FRONTAL BOUNDARY STRETCHING SOUTH AND
EXPECTED TO PUSH EAST ACROSS THE FORECAST AREA SATURDAY MORNING.
MID-LVL HEIGHTS WILL STEADILY RISE AS THE RIDGE PARKED ACROSS THE
CENTRAL CONUS PUSHES EAST...BRINGING MILDER AIR TO THE REGION SAT
WITH HIGHS IN THE MID/UPR 60S. THE FAR SOUTHERN CWFA COULD TOUCH 70
DEG SAT. TEMPS SUN ARE EXPECTED TO BE SLIGHTLY COOLER AS THE FLOW
BEGINS TO TRANSITION BRIEFLY INTO A QUASI-ZONAL SETUP. HOWEVER THIS
DOES NOT LOOK TO REMAIN VERY LONG...AS RIDGING RETURNS FOR MON AND
TEMPS SHUD QUICKLY WARM INTO THE 70S ACROSS MUCH OF THE AREA. A WARM
FRONTAL BOUNDARY WILL LIFT ACROSS THE AREA EARLY MON...AS SOUTHERLY
FLOW STRENGTHENS. EXPECT MUCH OF THE DAY MON TO REMAIN DRY...HOWEVER
LATE AFTN/EVE A DEVELOPING LOW ACROSS THE CENTRAL PLAINS MAY HELP TO
GENERATE A FEW SHOWERS/THUNDERSTORMS LATE MON.

TUESDAY-WEDNESDAY...
TOWARDS THE MIDDLE OF NEXT WEEK ENSEMBLES CONTINUE TO SUGGEST THE
RIDGING OVERHEAD WILL SHIFT EAST...WITH FLOW TRYING TO FLATTEN.
SUGGESTING THAT A SEMI-ZONAL SETUP MAY DEVELOP BY WED...WHICH WILL
LIKELY RESULT IN PERIODIC CHANCES FOR SHOWERS. TEMPS SHUD RETURN TO
MORE SEASONAL CONDS TUE/WED.

BEACHLER

&&

.AVIATION...

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

* MVFR CIGS/VIS DURG THE LATE NIGHT/EARLY MORNING HOURS. CHANCE
  CIGS COULD DROP TO IFR LEVELS.

KREIN

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

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...ANY RESIDUAL PCPN
REMAINS ISOLD AND SOUTH OF THE TERMINALS. HOWEVER...THERE IS SOLE
RESIDUAL LOW LEVEL MOISTURE AND AS HIGH CLOUD PUSHES AWAY...A BAND
OF STRATUS CAN BE SEEN IN THE LATEST SATELLITE IMAGERY. AS A
NOCTURNAL SUBSIDENCE INVERSION LOWERS OVERNIGHT...CLOUD BASES
SHOULD GRADUALLY LOWER TO LOWER END MVFR LEVELS. THERE IS A CHANCE
FOR SOME PATCHY IFR CIGS DURG THE EARLY MORNING HOURS...ESPECIALLY
OVER NWRN IL WHERE SOME RAIN FELL EARLIER...WHICH WOULD MOST
LIKELY AFFECT RFD AND POSSIBLY DPA. AS WINDS BECM LGT/VRBL
OVERNIGHT...VIS SHOULD DROP TO 3-5SM DURG THE EARLY MORNING
HOURS...AND IF THE WESTERN EDGE OF THE STRATUS DECK CAN ERODE OVER
NWRN IL BEFORE SUNRISE...THERE IS A CHANCE FOR RFD TO DROP INTO
IFR OR EVEN LIFR VIS LEVELS. HOWEVER...THAT WOULD BE HIGHLY
DEPENDENT ON THE CIG TRENDS.

THROUGH THE DAY ON FRIDAY...ANOTHER SFC TROUGH WILL TRACK ACROSS
THE CNTRL PLAINS TO THE UPPER MISSISSIPPI VALLEY BY EARLY EVENING.
WINDS WILL BECOME SSWLY THOUGH THE DAY...THOUGH WITH A WEAK
PRESSURE GRADIENT...WIND SPEEDS SHOULD BE LESS THAN 10KT THROUGH
THE DAY. FOR THE EARLY EVENING HOURS...SOME OF THE MODELS ARE
SUGGESTING THAT THERE COULD BE SOME LIGHT PCPN WITH THE PASSAGE OF
THE NEXT SFC TROUGH. HOWEVER...SINCE FORCING WITH THIS TROUGH AXIS
LOOKS TO BE RATHER WEAK...CONFIDENCE IS TOO LOW TO ADD PCPN TO THE
TAFS AT THIS TIME.

KREIN

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

* MEDIUM CONFIDENCE IN CIG/VIS TRENDS OVERNIGHT.

* LOW CONFIDENCE IN SPECIFIC TIMING OF IMPROVEMENT TO VFR FRIDAY.

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE DAY ON
  FRIDAY.

* LOW CONFIDENCE IN THE CHANCES FOR PCPN FRIDAY EVENING.

KREIN

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
215 AM CDT

A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM WESTERN QUEBEC
SOUTHWEST THROUGH THE CENTRAL GREAT LAKES...INTO THE TENNESSEE
VALLEY. THIS RIDGE WILL CONTINUE TO DRIFT EAST OF THE REGION THIS
AFTERNOON...MEANWHILE A TROUGH OF LOW PRESSURE OVER CENTRAL CANADA
CONTINUES TO SLIDE EAST TOWARDS HUDSON BAY SATURDAY. THE GRADIENT
WILL REMAIN LIGHT THROUGH THIS AFTERNOON...THEN SLOWLY TURN
SOUTH/SOUTHWESTERLY. AS THE LOW NEARS HUDSON BAY ON SATURDAY...A
FRONTAL BOUNDARY WILL TRAIL AND SLOWLY SLIDE SOUTH ACROSS LAKE
MICHIGAN. THIS WILL RESULT IN WINDS TURNING WEST/NORTHWEST
SATURDAY AFTERNOON/EVENING. COOLER AIR WILL FLOW ACROSS THE LAKE
ALONG WITH A TIGHTENING GRADIENT...RESULTING IN INCREASING WINDS
NEARING 30KT AT TIMES. THEN ANOTHER RIDGE OF HIGH PRESSURE WILL
QUICKLY SLIDE SOUTHEAST FROM THE UPPER MIDWEST/NORTHERN PLAINS
SUNDAY...STEADILY DIMINISHING THE GRADIENT. ANOTHER TROUGH OF LOW
PRESSURE IS EXPECTED TO DEVELOP EARLY NEXT WEEK ACROSS THE CENTRAL
PLAINS...THEN APPROACH LAKE MICHIGAN CLOSER TO MID-WEEK. THIS WILL
BRING WINDS BACK TO THE SOUTHWEST WITH OCCASIONALLY WINDS GUSTING
TO 30KT.

BEACHLER

&&

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

$$

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

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







000
FXUS63 KLOT 240730
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 AM CDT FRI OCT 24 2014

.DISCUSSION...
903 PM CDT

THE CHANGES TO THE FORECAST WERE TO DISSIPATE POPS AT A QUICKER
RATE...HOLD ONTO MORE CLOUD COVER THROUGH THE NIGHT...AND ADD
DENSE MENTION TO THE FOG WORDING OVER NORTH CENTRAL ILLINOIS.

THE SURFACE TROUGH THAT HAD BEEN APPROACHING STEADILY TOWARD THE
AREA THE PAST 24 HOURS HAS DIMINISHED GREATLY SINCE MID-
AFTERNOON...LOSING MUCH OF ITS LOW-LEVEL CONVERGENCE. FORCING FOR
RAIN SHOWERS HAS ALSO BEEN DIMINISHING WITH MORE LIMITED MOISTURE
CONVERGENCE WITHIN THE AREA OF ASCENT...SO SHOWERS HAVE QUICKLY
BEEN WANING. THE SPOTTY LIGHT SHOWERS SURVIVING SHOULD CONTINUE
SLOWLY EAST WITH A GRADUAL FADE INTO OVERNIGHT.

WITH THE HIGHER DEW POINT PLUME OF UPPER 40S TO LOWER 50S BROUGHT
UP TO EASTERN IA AND NORTHWEST/NORTH CENTRAL IL BY THE
TROUGH...CONDITIONS ARE IN PLACE FOR FOG. ONE THING AGAINST FOG
DEVELOPMENT IS EXISTING CLOUDS WHICH AS SEEN ON THE 00Z DVN RAOB
ARE FAIRLY DEEP /SEVERAL THOUSAND FEET SATURATED LAYER/. THIS AREA
LOOKS TO SLOW ITS MOVEMENT EAST OVER THE CWA THUS NOT ALLOWING
MUCH CLEARING FOR NORTHEAST IL AND NORTHWEST IN...INCLUDING
CHICAGO. MORE PROBLEMATIC WILL BE POSSIBLY SOME CLEARING OF THIS
CLOUD LAYER IN NORTH CENTRAL IL LATE ALLOWING FOR NEARBY VERY LOW
STRATUS AND SOME FOG ALREADY BEING OBSERVED TO JUST EXPAND IN AND
WORSEN THROUGH DAYBREAK. FORECAST SOUNDINGS AND HIGH-RES GUIDANCE
FIELDS HAVE TRENDED THIS ROUTE IN THE GENERAL ROCKFORD AND DIXON
AREAS. HAVE BUMPED UP FOG WORDING THERE AND COULD SEE A DENSE FOG
ADVISORY BEING NEEDED DEPENDING ON HOW AGGRESSIVE THE LOWERING IS.
AGAIN FURTHER EASTWARD TOWARD CHICAGO EXPECT THE CLOUDS TO LIMIT
ANY FOG THAT GRADUALLY DEVELOPS FROM GETTING TOO BAD.

HAVE BUMPED UP MINS A DEGREE OR TWO WARMER WITH THE CLOUDS
EXPECTED TO HANG ON A GOOD PART OF THE NIGHT IN MOST PLACES.

MTF

//PREV DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* MVFR CIGS/VIS DURG THE LATE NIGHT/EARLY MORNING HOURS. CHANCE
  CIGS COULD DROP TO IFR LEVELS.

KREIN

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

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...ANY RESIDUAL PCPN
REMAINS ISOLD AND SOUTH OF THE TERMINALS. HOWEVER...THERE IS SOLE
RESIDUAL LOW LEVEL MOISTURE AND AS HIGH CLOUD PUSHES AWAY...A BAND
OF STRATUS CAN BE SEEN IN THE LATEST SATELLITE IMAGERY. AS A
NOCTURNAL SUBSIDENCE INVERSION LOWERS OVERNIGHT...CLOUD BASES
SHOULD GRADUALLY LOWER TO LOWER END MVFR LEVELS. THERE IS A CHANCE
FOR SOME PATCHY IFR CIGS DURG THE EARLY MORNING HOURS...ESPECIALLY
OVER NWRN IL WHERE SOME RAIN FELL EARLIER...WHICH WOULD MOST
LIKELY AFFECT RFD AND POSSIBLY DPA. AS WINDS BECM LGT/VRBL
OVERNIGHT...VIS SHOULD DROP TO 3-5SM DURG THE EARLY MORNING
HOURS...AND IF THE WESTERN EDGE OF THE STRATUS DECK CAN ERODE OVER
NWRN IL BEFORE SUNRISE...THERE IS A CHANCE FOR RFD TO DROP INTO
IFR OR EVEN LIFR VIS LEVELS. HOWEVER...THAT WOULD BE HIGHLY
DEPENDENT ON THE CIG TRENDS.

THROUGH THE DAY ON FRIDAY...ANOTHER SFC TROUGH WILL TRACK ACROSS
THE CNTRL PLAINS TO THE UPPER MISSISSIPPI VALLEY BY EARLY EVENING.
WINDS WILL BECOME SSWLY THOUGH THE DAY...THOUGH WITH A WEAK
PRESSURE GRADIENT...WIND SPEEDS SHOULD BE LESS THAN 10KT THROUGH
THE DAY. FOR THE EARLY EVENING HOURS...SOME OF THE MODELS ARE
SUGGESTING THAT THERE COULD BE SOME LIGHT PCPN WITH THE PASSAGE OF
THE NEXT SFC TROUGH. HOWEVER...SINCE FORCING WITH THIS TROUGH AXIS
LOOKS TO BE RATHER WEAK...CONFIDENCE IS TOO LOW TO ADD PCPN TO THE
TAFS AT THIS TIME.

KREIN

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

* MEDIUM CONFIDENCE IN CIG/VIS TRENDS OVERNIGHT.

* LOW CONFIDENCE IN SPECIFIC TIMING OF IMPROVEMENT TO VFR FRIDAY.

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE DAY ON
  FRIDAY.

* LOW CONFIDENCE IN THE CHANCES FOR PCPN FRIDAY EVENING.

KREIN

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
215 AM CDT

A WEAK RIDGE OF HIGH PRESSURE EXTENDS FROM WESTERN QUEBEC
SOUTHWEST THROUGH THE CENTRAL GREAT LAKES...INTO THE TENNESSEE
VALLEY. THIS RIDGE WILL CONTINUE TO DRIFT EAST OF THE REGION THIS
AFTERNOON...MEANWHILE A TROUGH OF LOW PRESSURE OVER CENTRAL CANADA
CONTINUES TO SLIDE EAST TOWARDS HUDSON BAY SATURDAY. THE GRADIENT
WILL REMAIN LIGHT THROUGH THIS AFTERNOON...THEN SLOWLY TURN
SOUTH/SOUTHWESTERLY. AS THE LOW NEARS HUDSON BAY ON SATURDAY...A
FRONTAL BOUNDARY WILL TRAIL AND SLOWLY SLIDE SOUTH ACROSS LAKE
MICHIGAN. THIS WILL RESULT IN WINDS TURNING WEST/NORTHWEST
SATURDAY AFTERNOON/EVENING. COOLER AIR WILL FLOW ACROSS THE LAKE
ALONG WITH A TIGHTENING GRADIENT...RESULTING IN INCREASING WINDS
NEARING 30KT AT TIMES. THEN ANOTHER RIDGE OF HIGH PRESSURE WILL
QUICKLY SLIDE SOUTHEAST FROM THE UPPER MIDWEST/NORTHERN PLAINS
SUNDAY...STEADILY DIMINISHING THE GRADIENT. ANOTHER TROUGH OF LOW
PRESSURE IS EXPECTED TO DEVELOP EARLY NEXT WEEK ACROSS THE CENTRAL
PLAINS...THEN APPROACH LAKE MICHIGAN CLOSER TO MID-WEEK. THIS WILL
BRING WINDS BACK TO THE SOUTHWEST WITH OCCASIONALLY WINDS GUSTING
TO 30KT.

BEACHLER

&&

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

$$

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

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







000
FXUS63 KLOT 240549
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1249 AM CDT FRI OCT 24 2014

.DISCUSSION...
903 PM CDT

THE CHANGES TO THE FORECAST WERE TO DISSIPATE POPS AT A QUICKER
RATE...HOLD ONTO MORE CLOUD COVER THROUGH THE NIGHT...AND ADD
DENSE MENTION TO THE FOG WORDING OVER NORTH CENTRAL ILLINOIS.

THE SURFACE TROUGH THAT HAD BEEN APPROACHING STEADILY TOWARD THE
AREA THE PAST 24 HOURS HAS DIMINISHED GREATLY SINCE MID-
AFTERNOON...LOSING MUCH OF ITS LOW-LEVEL CONVERGENCE. FORCING FOR
RAIN SHOWERS HAS ALSO BEEN DIMINISHING WITH MORE LIMITED MOISTURE
CONVERGENCE WITHIN THE AREA OF ASCENT...SO SHOWERS HAVE QUICKLY
BEEN WANING. THE SPOTTY LIGHT SHOWERS SURVIVING SHOULD CONTINUE
SLOWLY EAST WITH A GRADUAL FADE INTO OVERNIGHT.

WITH THE HIGHER DEW POINT PLUME OF UPPER 40S TO LOWER 50S BROUGHT
UP TO EASTERN IA AND NORTHWEST/NORTH CENTRAL IL BY THE
TROUGH...CONDITIONS ARE IN PLACE FOR FOG. ONE THING AGAINST FOG
DEVELOPMENT IS EXISTING CLOUDS WHICH AS SEEN ON THE 00Z DVN RAOB
ARE FAIRLY DEEP /SEVERAL THOUSAND FEET SATURATED LAYER/. THIS AREA
LOOKS TO SLOW ITS MOVEMENT EAST OVER THE CWA THUS NOT ALLOWING
MUCH CLEARING FOR NORTHEAST IL AND NORTHWEST IN...INCLUDING
CHICAGO. MORE PROBLEMATIC WILL BE POSSIBLY SOME CLEARING OF THIS
CLOUD LAYER IN NORTH CENTRAL IL LATE ALLOWING FOR NEARBY VERY LOW
STRATUS AND SOME FOG ALREADY BEING OBSERVED TO JUST EXPAND IN AND
WORSEN THROUGH DAYBREAK. FORECAST SOUNDINGS AND HIGH-RES GUIDANCE
FIELDS HAVE TRENDED THIS ROUTE IN THE GENERAL ROCKFORD AND DIXON
AREAS. HAVE BUMPED UP FOG WORDING THERE AND COULD SEE A DENSE FOG
ADVISORY BEING NEEDED DEPENDING ON HOW AGGRESSIVE THE LOWERING IS.
AGAIN FURTHER EASTWARD TOWARD CHICAGO EXPECT THE CLOUDS TO LIMIT
ANY FOG THAT GRADUALLY DEVELOPS FROM GETTING TOO BAD.

HAVE BUMPED UP MINS A DEGREE OR TWO WARMER WITH THE CLOUDS
EXPECTED TO HANG ON A GOOD PART OF THE NIGHT IN MOST PLACES.

MTF

//PREV DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* MVFR CIGS/VIS DURG THE LATE NIGHT/EARLY MORNING HOURS. CHANCE
  CIGS COULD DROP TO IFR LEVELS.

KREIN

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

FOLLOWING THE PASSAGE OF A WEAK SFC TROUGH...ANY RESIDUAL PCPN
REMAINS ISOLD AND SOUTH OF THE TERMINALS. HOWEVER...THERE IS SOLE
RESIDUAL LOW LEVEL MOISTURE AND AS HIGH CLOUD PUSHES AWAY...A BAND
OF STRATUS CAN BE SEEN IN THE LATEST SATELLITE IMAGERY. AS A
NOCTURNAL SUBSIDENCE INVERSION LOWERS OVERNIGHT...CLOUD BASES
SHOULD GRADUALLY LOWER TO LOWER END MVFR LEVELS. THERE IS A CHANCE
FOR SOME PATCHY IFR CIGS DURG THE EARLY MORNING HOURS...ESPECIALLY
OVER NWRN IL WHERE SOME RAIN FELL EARLIER...WHICH WOULD MOST
LIKELY AFFECT RFD AND POSSIBLY DPA. AS WINDS BECM LGT/VRBL
OVERNIGHT...VIS SHOULD DROP TO 3-5SM DURG THE EARLY MORNING
HOURS...AND IF THE WESTERN EDGE OF THE STRATUS DECK CAN ERODE OVER
NWRN IL BEFORE SUNRISE...THERE IS A CHANCE FOR RFD TO DROP INTO
IFR OR EVEN LIFR VIS LEVELS. HOWEVER...THAT WOULD BE HIGHLY
DEPENDENT ON THE CIG TRENDS.

THROUGH THE DAY ON FRIDAY...ANOTHER SFC TROUGH WILL TRACK ACROSS
THE CNTRL PLAINS TO THE UPPER MISSISSIPPI VALLEY BY EARLY EVENING.
WINDS WILL BECOME SSWLY THOUGH THE DAY...THOUGH WITH A WEAK
PRESSURE GRADIENT...WIND SPEEDS SHOULD BE LESS THAN 10KT THROUGH
THE DAY. FOR THE EARLY EVENING HOURS...SOME OF THE MODELS ARE
SUGGESTING THAT THERE COULD BE SOME LIGHT PCPN WITH THE PASSAGE OF
THE NEXT SFC TROUGH. HOWEVER...SINCE FORCING WITH THIS TROUGH AXIS
LOOKS TO BE RATHER WEAK...CONFIDENCE IS TOO LOW TO ADD PCPN TO THE
TAFS AT THIS TIME.

KREIN

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

* MEDIUM CONFIDENCE IN CIG/VIS TRENDS OVERNIGHT.

* LOW CONFIDENCE IN SPECIFIC TIMING OF IMPROVEMENT TO VFR FRIDAY.

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE DAY ON
  FRIDAY.

* LOW CONFIDENCE IN THE CHANCES FOR PCPN FRIDAY EVENING.

KREIN

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 240257
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
957 PM CDT THU OCT 23 2014

.DISCUSSION...
903 PM CDT

THE CHANGES TO THE FORECAST WERE TO DISSIPATE POPS AT A QUICKER
RATE...HOLD ONTO MORE CLOUD COVER THROUGH THE NIGHT...AND ADD
DENSE MENTION TO THE FOG WORDING OVER NORTH CENTRAL ILLINOIS.

THE SURFACE TROUGH THAT HAD BEEN APPROACHING STEADILY TOWARD THE
AREA THE PAST 24 HOURS HAS DIMINISHED GREATLY SINCE MID-
AFTERNOON...LOSING MUCH OF ITS LOW-LEVEL CONVERGENCE. FORCING FOR
RAIN SHOWERS HAS ALSO BEEN DIMINISHING WITH MORE LIMITED MOISTURE
CONVERGENCE WITHIN THE AREA OF ASCENT...SO SHOWERS HAVE QUICKLY
BEEN WANING. THE SPOTTY LIGHT SHOWERS SURVIVING SHOULD CONTINUE
SLOWLY EAST WITH A GRADUAL FADE INTO OVERNIGHT.

WITH THE HIGHER DEW POINT PLUME OF UPPER 40S TO LOWER 50S BROUGHT
UP TO EASTERN IA AND NORTHWEST/NORTH CENTRAL IL BY THE
TROUGH...CONDITIONS ARE IN PLACE FOR FOG. ONE THING AGAINST FOG
DEVELOPMENT IS EXISTING CLOUDS WHICH AS SEEN ON THE 00Z DVN RAOB
ARE FAIRLY DEEP /SEVERAL THOUSAND FEET SATURATED LAYER/. THIS AREA
LOOKS TO SLOW ITS MOVEMENT EAST OVER THE CWA THUS NOT ALLOWING
MUCH CLEARING FOR NORTHEAST IL AND NORTHWEST IN...INCLUDING
CHICAGO. MORE PROBLEMATIC WILL BE POSSIBLY SOME CLEARING OF THIS
CLOUD LAYER IN NORTH CENTRAL IL LATE ALLOWING FOR NEARBY VERY LOW
STRATUS AND SOME FOG ALREADY BEING OBSERVED TO JUST EXPAND IN AND
WORSEN THROUGH DAYBREAK. FORECAST SOUNDINGS AND HIGH-RES GUIDANCE
FIELDS HAVE TRENDED THIS ROUTE IN THE GENERAL ROCKFORD AND DIXON
AREAS. HAVE BUMPED UP FOG WORDING THERE AND COULD SEE A DENSE FOG
ADVISORY BEING NEEDED DEPENDING ON HOW AGGRESSIVE THE LOWERING IS.
AGAIN FURTHER EASTWARD TOWARD CHICAGO EXPECT THE CLOUDS TO LIMIT
ANY FOG THAT GRADUALLY DEVELOPS FROM GETTING TOO BAD.

HAVE BUMPED UP MINS A DEGREE OR TWO WARMER WITH THE CLOUDS
EXPECTED TO HANG ON A GOOD PART OF THE NIGHT IN MOST PLACES.

MTF

//PREV DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* MVFR CIGS AND VSBY OVERNIGHT INTO FRIDAY MORNING. IFR CONDITIONS
  POSSIBLE LATE TONIGHT.

KMD

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

SHOWERS ARE GENERALLY FALLING APART OVER NE ILLINOIS...JUST SOME
ISOLATED -SHRA AT THIS POINT. CIGS ARE SLOWLY LOWERING FROM WEST
TO EAST. GUIDANCE IS BACKING OFF ON THE EASTWARD EXTEND OF LOW
VISIBILITIES GIVEN THAT THE CLOUD COVER WILL REMAIN PERSISTENT
THROUGH THE NIGHT...BUT WE DO EXPECT CONTINUED GRADUAL LOWERING OF
CIGS INTO MVFR EVERYWHERE....AND TO IFR IN WESTERN AREAS.
WIDESPREAD DENSE FOG IS NO LONGER EXPECTED...BUT THERE COULD BE
SOME MVFR OR POSSIBLY IFR VSBYS TOWARD DAYBREAK GIVEN THE MOIST
LOW LEVELS AND LIGHT FLOW AND THE LOWERING INVERSION. KMD

PREVIOUS DISCUSSION FROM 00Z...

SLOW MOVING BAND OF SCATTERED SHOWERS WILL CONTINUE TO MIGRATE
EAST THIS EVENING. EXPECT THE BEST CHANCE FOR A SHOWER WILL BE
ALONG AND NORTH OF A KRPJ-KDPA-KORD LINE OR GENERALLY NORTH OF
INTERSTATE 88.

WIDESPREAD MVFR CIGS BEHIND THE SHOWERS WILL SPREAD INTO NE
ILLINOIS AND NW INDIANA THROUGH THE NIGHT. EXPECT WITH LIGHT WINDS
AND NO DRY AIR PUSHING IN BEHIND THE FRONT THAT CONDITIONS WILL
DETERIORATE THROUGH THE NIGHT. AREAS TO THE WEST SUCH AS AROUND
KRFD AND WEST OF THE MAIN CHICAGOLAND TERMINALS HAVE THE BEST
CHANCE OF REALLY TANKING TONIGHT WITH LIFR CIGS AND VSBYS.
GUIDANCE IS HINTING AT IFR AND EVEN LIFR CONDITIONS EAST TO
CHICAGO LATE TONIGHT AS WELL...BUT WILL HAVE TO WATCH TRENDS AS WE
HAVE A HARD TIME BELIEVING CLOUDS WILL CLEAR AWAY FROM WESTERN
AREAS AND WOULD STILL GENERALLY EXPECT A GRADUAL LOWERING TO LOW
END MVFR. IF CLOUDS ARE ABLE TO CLEAR FARTHER EAST...THEN THE LIFR
CONDITIONS SUGGESTED BY MOS GUIDANCE THE HRRR WOULD BE POSSIBLE
ACROSS THE AREA.

EXPECT DECENT CLEARING TO BE SLOW GOING BUT EXPECT LIFTING TO VFR
BY THE MIDDAY OR SO. LAKE BREEZE LOOKS TO BE CONTAINED ALONG THE
LAKESHORE FRIDAY AFTERNOON.

KMD

KMD

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

* HIGH IN CEILING TRENDS...BUT LOW-MEDIUM IN HOW LOW THE CIGS/VSBY
  WILL BE.

* LOW-MEDIUM IN SPECIFIC LIFTING TIMES ON FRIDAY.

KMD

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 240257
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
957 PM CDT THU OCT 23 2014

.DISCUSSION...
903 PM CDT

THE CHANGES TO THE FORECAST WERE TO DISSIPATE POPS AT A QUICKER
RATE...HOLD ONTO MORE CLOUD COVER THROUGH THE NIGHT...AND ADD
DENSE MENTION TO THE FOG WORDING OVER NORTH CENTRAL ILLINOIS.

THE SURFACE TROUGH THAT HAD BEEN APPROACHING STEADILY TOWARD THE
AREA THE PAST 24 HOURS HAS DIMINISHED GREATLY SINCE MID-
AFTERNOON...LOSING MUCH OF ITS LOW-LEVEL CONVERGENCE. FORCING FOR
RAIN SHOWERS HAS ALSO BEEN DIMINISHING WITH MORE LIMITED MOISTURE
CONVERGENCE WITHIN THE AREA OF ASCENT...SO SHOWERS HAVE QUICKLY
BEEN WANING. THE SPOTTY LIGHT SHOWERS SURVIVING SHOULD CONTINUE
SLOWLY EAST WITH A GRADUAL FADE INTO OVERNIGHT.

WITH THE HIGHER DEW POINT PLUME OF UPPER 40S TO LOWER 50S BROUGHT
UP TO EASTERN IA AND NORTHWEST/NORTH CENTRAL IL BY THE
TROUGH...CONDITIONS ARE IN PLACE FOR FOG. ONE THING AGAINST FOG
DEVELOPMENT IS EXISTING CLOUDS WHICH AS SEEN ON THE 00Z DVN RAOB
ARE FAIRLY DEEP /SEVERAL THOUSAND FEET SATURATED LAYER/. THIS AREA
LOOKS TO SLOW ITS MOVEMENT EAST OVER THE CWA THUS NOT ALLOWING
MUCH CLEARING FOR NORTHEAST IL AND NORTHWEST IN...INCLUDING
CHICAGO. MORE PROBLEMATIC WILL BE POSSIBLY SOME CLEARING OF THIS
CLOUD LAYER IN NORTH CENTRAL IL LATE ALLOWING FOR NEARBY VERY LOW
STRATUS AND SOME FOG ALREADY BEING OBSERVED TO JUST EXPAND IN AND
WORSEN THROUGH DAYBREAK. FORECAST SOUNDINGS AND HIGH-RES GUIDANCE
FIELDS HAVE TRENDED THIS ROUTE IN THE GENERAL ROCKFORD AND DIXON
AREAS. HAVE BUMPED UP FOG WORDING THERE AND COULD SEE A DENSE FOG
ADVISORY BEING NEEDED DEPENDING ON HOW AGGRESSIVE THE LOWERING IS.
AGAIN FURTHER EASTWARD TOWARD CHICAGO EXPECT THE CLOUDS TO LIMIT
ANY FOG THAT GRADUALLY DEVELOPS FROM GETTING TOO BAD.

HAVE BUMPED UP MINS A DEGREE OR TWO WARMER WITH THE CLOUDS
EXPECTED TO HANG ON A GOOD PART OF THE NIGHT IN MOST PLACES.

MTF

//PREV DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* MVFR CIGS AND VSBY OVERNIGHT INTO FRIDAY MORNING. IFR CONDITIONS
  POSSIBLE LATE TONIGHT.

KMD

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

SHOWERS ARE GENERALLY FALLING APART OVER NE ILLINOIS...JUST SOME
ISOLATED -SHRA AT THIS POINT. CIGS ARE SLOWLY LOWERING FROM WEST
TO EAST. GUIDANCE IS BACKING OFF ON THE EASTWARD EXTEND OF LOW
VISIBILITIES GIVEN THAT THE CLOUD COVER WILL REMAIN PERSISTENT
THROUGH THE NIGHT...BUT WE DO EXPECT CONTINUED GRADUAL LOWERING OF
CIGS INTO MVFR EVERYWHERE....AND TO IFR IN WESTERN AREAS.
WIDESPREAD DENSE FOG IS NO LONGER EXPECTED...BUT THERE COULD BE
SOME MVFR OR POSSIBLY IFR VSBYS TOWARD DAYBREAK GIVEN THE MOIST
LOW LEVELS AND LIGHT FLOW AND THE LOWERING INVERSION. KMD

PREVIOUS DISCUSSION FROM 00Z...

SLOW MOVING BAND OF SCATTERED SHOWERS WILL CONTINUE TO MIGRATE
EAST THIS EVENING. EXPECT THE BEST CHANCE FOR A SHOWER WILL BE
ALONG AND NORTH OF A KRPJ-KDPA-KORD LINE OR GENERALLY NORTH OF
INTERSTATE 88.

WIDESPREAD MVFR CIGS BEHIND THE SHOWERS WILL SPREAD INTO NE
ILLINOIS AND NW INDIANA THROUGH THE NIGHT. EXPECT WITH LIGHT WINDS
AND NO DRY AIR PUSHING IN BEHIND THE FRONT THAT CONDITIONS WILL
DETERIORATE THROUGH THE NIGHT. AREAS TO THE WEST SUCH AS AROUND
KRFD AND WEST OF THE MAIN CHICAGOLAND TERMINALS HAVE THE BEST
CHANCE OF REALLY TANKING TONIGHT WITH LIFR CIGS AND VSBYS.
GUIDANCE IS HINTING AT IFR AND EVEN LIFR CONDITIONS EAST TO
CHICAGO LATE TONIGHT AS WELL...BUT WILL HAVE TO WATCH TRENDS AS WE
HAVE A HARD TIME BELIEVING CLOUDS WILL CLEAR AWAY FROM WESTERN
AREAS AND WOULD STILL GENERALLY EXPECT A GRADUAL LOWERING TO LOW
END MVFR. IF CLOUDS ARE ABLE TO CLEAR FARTHER EAST...THEN THE LIFR
CONDITIONS SUGGESTED BY MOS GUIDANCE THE HRRR WOULD BE POSSIBLE
ACROSS THE AREA.

EXPECT DECENT CLEARING TO BE SLOW GOING BUT EXPECT LIFTING TO VFR
BY THE MIDDAY OR SO. LAKE BREEZE LOOKS TO BE CONTAINED ALONG THE
LAKESHORE FRIDAY AFTERNOON.

KMD

KMD

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

* HIGH IN CEILING TRENDS...BUT LOW-MEDIUM IN HOW LOW THE CIGS/VSBY
  WILL BE.

* LOW-MEDIUM IN SPECIFIC LIFTING TIMES ON FRIDAY.

KMD

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 240203 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 PM CDT THU OCT 23 2014

.DISCUSSION...
903 PM CDT

THE CHANGES TO THE FORECAST WERE TO DISSIPATE POPS AT A QUICKER
RATE...HOLD ONTO MORE CLOUD COVER THROUGH THE NIGHT...AND ADD
DENSE MENTION TO THE FOG WORDING OVER NORTH CENTRAL ILLINOIS.

THE SURFACE TROUGH THAT HAD BEEN APPROACHING STEADILY TOWARD THE
AREA THE PAST 24 HOURS HAS DIMINISHED GREATLY SINCE MID-
AFTERNOON...LOSING MUCH OF ITS LOW-LEVEL CONVERGENCE. FORCING FOR
RAIN SHOWERS HAS ALSO BEEN DIMINISHING WITH MORE LIMITED MOISTURE
CONVERGENCE WITHIN THE AREA OF ASCENT...SO SHOWERS HAVE QUICKLY
BEEN WANING. THE SPOTTY LIGHT SHOWERS SURVIVING SHOULD CONTINUE
SLOWLY EAST WITH A GRADUAL FADE INTO OVERNIGHT.

WITH THE HIGHER DEW POINT PLUME OF UPPER 40S TO LOWER 50S BROUGHT
UP TO EASTERN IA AND NORTHWEST/NORTH CENTRAL IL BY THE
TROUGH...CONDITIONS ARE IN PLACE FOR FOG. ONE THING AGAINST FOG
DEVELOPMENT IS EXISTING CLOUDS WHICH AS SEEN ON THE 00Z DVN RAOB
ARE FAIRLY DEEP /SEVERAL THOUSAND FEET SATURATED LAYER/. THIS AREA
LOOKS TO SLOW ITS MOVEMENT EAST OVER THE CWA THUS NOT ALLOWING
MUCH CLEARING FOR NORTHEAST IL AND NORTHWEST IN...INCLUDING
CHICAGO. MORE PROBLEMATIC WILL BE POSSIBLY SOME CLEARING OF THIS
CLOUD LAYER IN NORTH CENTRAL IL LATE ALLOWING FOR NEARBY VERY LOW
STRATUS AND SOME FOG ALREADY BEING OBSERVED TO JUST EXPAND IN AND
WORSEN THROUGH DAYBREAK. FORECAST SOUNDINGS AND HIGH-RES GUIDANCE
FIELDS HAVE TRENDED THIS ROUTE IN THE GENERAL ROCKFORD AND DIXON
AREAS. HAVE BUMPED UP FOG WORDING THERE AND COULD SEE A DENSE FOG
ADVISORY BEING NEEDED DEPENDING ON HOW AGGRESSIVE THE LOWERING IS.
AGAIN FURTHER EASTWARD TOWARD CHICAGO EXPECT THE CLOUDS TO LIMIT
ANY FOG THAT GRADUALLY DEVELOPS FROM GETTING TOO BAD.

HAVE BUMPED UP MINS A DEGREE OR TWO WARMER WITH THE CLOUDS
EXPECTED TO HANG ON A GOOD PART OF THE NIGHT IN MOST PLACES.

MTF

&&

.PREV DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL LATE TONIGHT.

KMD

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

SLOW MOVING BAND OF SCATTERED SHOWERS WILL CONTINUE TO MIGRATE
EAST THIS EVENING. EXPECT THE BEST CHANCE FOR A SHOWER WILL BE
ALONG AND NORTH OF A KRPJ-KDPA-KORD LINE OR GENERALLY NORTH OF
INTERSTATE 88.

WIDESPREAD MVFR CIGS BEHIND THE SHOWERS WILL SPREAD INTO NE
ILLINOIS AND NW INDIANA THROUGH THE NIGHT. EXPECT WITH LIGHT WINDS
AND NO DRY AIR PUSHING IN BEHIND THE FRONT THAT CONDITIONS WILL
DETERIORATE THROUGH THE NIGHT. AREAS TO THE WEST SUCH AS AROUND
KRFD AND WEST OF THE MAIN CHICAGOLAND TERMINALS HAVE THE BEST
CHANCE OF REALLY TANKING TONIGHT WITH LIFR CIGS AND VSBYS.
GUIDANCE IS HINTING AT IFR AND EVEN LIFR CONDITIONS EAST TO
CHICAGO LATE TONIGHT AS WELL...BUT WILL HAVE TO WATCH TRENDS AS WE
HAVE A HARD TIME BELIEVING CLOUDS WILL CLEAR AWAY FROM WESTERN
AREAS AND WOULD STILL GENERALLY EXPECT A GRADUAL LOWERING TO LOW
END MVFR. IF CLOUDS ARE ABLE TO CLEAR FARTHER EAST...THEN THE LIFR
CONDITIONS SUGGESTED BY MOS GUIDANCE THE HRRR WOULD BE POSSIBLE
ACROSS THE AREA.

EXPECT DECENT CLEARING TO BE SLOW GOING BUT EXPECT LIFTING TO VFR
BY THE MIDDAY OR SO. LAKE BREEZE LOOKS TO BE CONTAINED ALONG THE
LAKESHORE FRIDAY AFTERNOON.

KMD

KMD

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

* MEDIUM IN COVERAGE AND OCCURRENCE OF -SHRA. BETTER CHANCE FOR
  ORD. HIGH CONFIDENCE IN TIMING.

* HIGH IN MVFR CIGS/VSBY AND MEDIUM ON TIMING. LOW-MEDIUM IN HOW
  LOW THE CIGS/VSBY WILL BE. MEDIUM ON LIFTING TIMES.

KMD

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 240203 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 PM CDT THU OCT 23 2014

.DISCUSSION...
903 PM CDT

THE CHANGES TO THE FORECAST WERE TO DISSIPATE POPS AT A QUICKER
RATE...HOLD ONTO MORE CLOUD COVER THROUGH THE NIGHT...AND ADD
DENSE MENTION TO THE FOG WORDING OVER NORTH CENTRAL ILLINOIS.

THE SURFACE TROUGH THAT HAD BEEN APPROACHING STEADILY TOWARD THE
AREA THE PAST 24 HOURS HAS DIMINISHED GREATLY SINCE MID-
AFTERNOON...LOSING MUCH OF ITS LOW-LEVEL CONVERGENCE. FORCING FOR
RAIN SHOWERS HAS ALSO BEEN DIMINISHING WITH MORE LIMITED MOISTURE
CONVERGENCE WITHIN THE AREA OF ASCENT...SO SHOWERS HAVE QUICKLY
BEEN WANING. THE SPOTTY LIGHT SHOWERS SURVIVING SHOULD CONTINUE
SLOWLY EAST WITH A GRADUAL FADE INTO OVERNIGHT.

WITH THE HIGHER DEW POINT PLUME OF UPPER 40S TO LOWER 50S BROUGHT
UP TO EASTERN IA AND NORTHWEST/NORTH CENTRAL IL BY THE
TROUGH...CONDITIONS ARE IN PLACE FOR FOG. ONE THING AGAINST FOG
DEVELOPMENT IS EXISTING CLOUDS WHICH AS SEEN ON THE 00Z DVN RAOB
ARE FAIRLY DEEP /SEVERAL THOUSAND FEET SATURATED LAYER/. THIS AREA
LOOKS TO SLOW ITS MOVEMENT EAST OVER THE CWA THUS NOT ALLOWING
MUCH CLEARING FOR NORTHEAST IL AND NORTHWEST IN...INCLUDING
CHICAGO. MORE PROBLEMATIC WILL BE POSSIBLY SOME CLEARING OF THIS
CLOUD LAYER IN NORTH CENTRAL IL LATE ALLOWING FOR NEARBY VERY LOW
STRATUS AND SOME FOG ALREADY BEING OBSERVED TO JUST EXPAND IN AND
WORSEN THROUGH DAYBREAK. FORECAST SOUNDINGS AND HIGH-RES GUIDANCE
FIELDS HAVE TRENDED THIS ROUTE IN THE GENERAL ROCKFORD AND DIXON
AREAS. HAVE BUMPED UP FOG WORDING THERE AND COULD SEE A DENSE FOG
ADVISORY BEING NEEDED DEPENDING ON HOW AGGRESSIVE THE LOWERING IS.
AGAIN FURTHER EASTWARD TOWARD CHICAGO EXPECT THE CLOUDS TO LIMIT
ANY FOG THAT GRADUALLY DEVELOPS FROM GETTING TOO BAD.

HAVE BUMPED UP MINS A DEGREE OR TWO WARMER WITH THE CLOUDS
EXPECTED TO HANG ON A GOOD PART OF THE NIGHT IN MOST PLACES.

MTF

&&

.PREV DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL LATE TONIGHT.

KMD

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

SLOW MOVING BAND OF SCATTERED SHOWERS WILL CONTINUE TO MIGRATE
EAST THIS EVENING. EXPECT THE BEST CHANCE FOR A SHOWER WILL BE
ALONG AND NORTH OF A KRPJ-KDPA-KORD LINE OR GENERALLY NORTH OF
INTERSTATE 88.

WIDESPREAD MVFR CIGS BEHIND THE SHOWERS WILL SPREAD INTO NE
ILLINOIS AND NW INDIANA THROUGH THE NIGHT. EXPECT WITH LIGHT WINDS
AND NO DRY AIR PUSHING IN BEHIND THE FRONT THAT CONDITIONS WILL
DETERIORATE THROUGH THE NIGHT. AREAS TO THE WEST SUCH AS AROUND
KRFD AND WEST OF THE MAIN CHICAGOLAND TERMINALS HAVE THE BEST
CHANCE OF REALLY TANKING TONIGHT WITH LIFR CIGS AND VSBYS.
GUIDANCE IS HINTING AT IFR AND EVEN LIFR CONDITIONS EAST TO
CHICAGO LATE TONIGHT AS WELL...BUT WILL HAVE TO WATCH TRENDS AS WE
HAVE A HARD TIME BELIEVING CLOUDS WILL CLEAR AWAY FROM WESTERN
AREAS AND WOULD STILL GENERALLY EXPECT A GRADUAL LOWERING TO LOW
END MVFR. IF CLOUDS ARE ABLE TO CLEAR FARTHER EAST...THEN THE LIFR
CONDITIONS SUGGESTED BY MOS GUIDANCE THE HRRR WOULD BE POSSIBLE
ACROSS THE AREA.

EXPECT DECENT CLEARING TO BE SLOW GOING BUT EXPECT LIFTING TO VFR
BY THE MIDDAY OR SO. LAKE BREEZE LOOKS TO BE CONTAINED ALONG THE
LAKESHORE FRIDAY AFTERNOON.

KMD

KMD

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

* MEDIUM IN COVERAGE AND OCCURRENCE OF -SHRA. BETTER CHANCE FOR
  ORD. HIGH CONFIDENCE IN TIMING.

* HIGH IN MVFR CIGS/VSBY AND MEDIUM ON TIMING. LOW-MEDIUM IN HOW
  LOW THE CIGS/VSBY WILL BE. MEDIUM ON LIFTING TIMES.

KMD

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 240018
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
718 PM CDT THU OCT 23 2014

.DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL LATE TONIGHT.

KMD

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

SLOW MOVING BAND OF SCATTERED SHOWERS WILL CONTINUE TO MIGRATE
EAST THIS EVENING. EXPECT THE BEST CHANCE FOR A SHOWER WILL BE
ALONG AND NORTH OF A KRPJ-KDPA-KORD LINE OR GENERALLY NORTH OF
INTERSTATE 88.

WIDESPREAD MVFR CIGS BEHIND THE SHOWERS WILL SPREAD INTO NE
ILLINOIS AND NW INDIANA THROUGH THE NIGHT. EXPECT WITH LIGHT WINDS
AND NO DRY AIR PUSHING IN BEHIND THE FRONT THAT CONDITIONS WILL
DETERIORATE THROUGH THE NIGHT. AREAS TO THE WEST SUCH AS AROUND
KRFD AND WEST OF THE MAIN CHICAGOLAND TERMINALS HAVE THE BEST
CHANCE OF REALLY TANKING TONIGHT WITH LIFR CIGS AND VSBYS.
GUIDANCE IS HINTING AT IFR AND EVEN LIFR CONDITIONS EAST TO
CHICAGO LATE TONIGHT AS WELL...BUT WILL HAVE TO WATCH TRENDS AS WE
HAVE A HARD TIME BELIEVING CLOUDS WILL CLEAR AWAY FROM WESTERN
AREAS AND WOULD STILL GENERALLY EXPECT A GRADUAL LOWERING TO LOW
END MVFR. IF CLOUDS ARE ABLE TO CLEAR FARTHER EAST...THEN THE LIFR
CONDITIONS SUGGESTED BY MOS GUIDANCE THE HRRR WOULD BE POSSIBLE
ACROSS THE AREA.

EXPECT DECENT CLEARING TO BE SLOW GOING BUT EXPECT LIFTING TO VFR
BY THE MIDDAY OR SO. LAKE BREEZE LOOKS TO BE CONTAINED ALONG THE
LAKESHORE FRIDAY AFTERNOON.

KMD

KMD


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

* MEDIUM IN COVERAGE AND OCCURRENCE OF -SHRA. BETTER CHANCE FOR
  ORD. HIGH CONFIDENCE IN TIMING.

* HIGH IN MVFR CIGS/VSBY AND MEDIUM ON TIMING. LOW-MEDIUM IN HOW
  LOW THE CIGS/VSBY WILL BE. MEDIUM ON LIFTING TIMES.

KMD

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

* FRIDAY NIGHT...MAINLY DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTHEAST WINDS.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST-SOUTHWEST WINDS.

KMD

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 232211
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
511 PM CDT THU OCT 23 2014

.DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL.

JEE

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

AN UPPER LEVEL WAVE IS APPROACHING FROM THE WEST WITH A LINE OF
SHOWERS EXTENDING INTO NORTHWEST IL. THE BAND OF SHOWERS WILL
CONTINUE EAST AND EXPECTING IT TO REMAIN RAGGED WITH HIT OR MISS
SHOWERS. RFD HAS THE BEST CHANCE OF SEEING AN ORGANIZED SHOWER
THIS AFTN. THE EASTERN TERMINALS WILL MOST LIKELY SEE SCATTERED
SHOWERS OR DRIZZLE THIS EVENING.

UPSTREAM OBS INDICATE THAT CIGS WILL FALL TO MVFR OR LOWER BEHIND
THE SHOWERS. HAVE THE MOST CONFIDENCE IN THE RFD TAF WITH IFR
CIGS. HAVE HIGH CONFIDENCE IN FOG AT RFD AND MEDIUM IN 1/4SM.

CLOUDS SHOULD LAST LONGER OVER THE EASTERN TERMINALS SO KEPT CIGS
IN THE MVFR RANGE WITH FOG ONLY AT DPA. CONDITIONS WILL IMPROVE TO
VFR QUICKLY TOMORROW AS THE CLOUDS SHIFT EAST. LIGHT WINDS
OVERNIGHT BECOME SW BTWN 5 AND 8 KT.

JEE

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

* MEDIUM CONFIDENCE IN COVERAGE AND OCCURRENCE OF -SHRA. BETTER
  CHANCE FOR ORD. HIGH CONFIDENCE IN TIMING.

* MEDIUM CONFIDENCE IN MVFR CIGS AND TIMING...LOW-MEDIUM CONFIDENCE
  IN HOW LOW THE CIGS WILL BE.

KMD


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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 232027
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
327 PM CDT THU OCT 23 2014

.DISCUSSION...
327 PM CDT

AFTERNOON GOES VAPOR IMAGERY DEPICTS A MID-LEVEL SHORT WAVE TROUGH
PROPAGATING THROUGH THE UPPER MISSISSIPPI VALLEY...WITH A WEAK
SURFACE LOW PRESSURE REFLECTION OVER EAST CENTRAL IOWA. AS EXPECTED
THE MOISTURE TRANSPORT AHEAD/INTO THIS SYSTEM IS RATHER SPARSE...
WITH A FAIRLY NARROW RIBBON OF LOW LEVEL MOISTURE AHEAD OF THE
TROUGH INTO PORTIONS OF NORTHWEST IL AND SOUTHERN WI. HIGH-RES
GUIDANCE CONTINUES TO INDICATE THE POTENTIAL OF SCATTERED SHOWERS
SPREADING EAST ACROSS THE CWA THROUGH THIS EVENING...THOUGH WITH
COVERAGE ANTICIPATED TO REMAIN SOMEWHAT LIMITED AS LOW LEVEL
MOISTURE TRANSPORT CONTINUES TO WEAKEN WITH LOSS OF DEFINITION OF
THE SURFACE WAVE AND LOW PRESSURE TROUGH. IN ADDITION TO THE
EXTENSIVE MID-HIGH LEVEL CLOUD COVER ACROSS THE AREA THIS
AFTERNOON...WHICH WILL LIKELY OBSCURE PARTIAL SOLAR ECLIPSE LATE
THIS AFTERNOON...LOWER CLOUDS ALSO EXPECTED AS LOW LEVEL MOISTURE
AXIS ARRIVES. SOME POTENTIAL FOR FOG DEVELOPMENT ESPECIALLY ACROSS
THE WESTERN PORTION OF THE CWA WHERE LIGHT WINDS AND 45-50 DEGREE
SURFACE DEW POINT TEMPS WILL RESULT IN HIGH LOW LEVEL RH...THOUGH
CLEARING SKIES WILL BE MORE LIKELY WEST OF THE CWA WHERE SIGNIFICANT
DENSE FOG/STRATUS DEVELOPMENT IS POSSIBLE LATE TONIGHT/EARLY FRIDAY
MORNING. AT LEAST CLOUD COVER AND MORE HUMID AIR WILL KEEP TEMPS A
LITTLE MILDER OVERNIGHT.

SHORT-WAVE WILL MOVE QUICKLY SOUTHEAST OF THE FORECAST AREA FRIDAY
MORNING...WITH MODEST HEIGHT RISES AND A SUBTLE SURFACE RIDGE AXIS
DEVELOPING OVER THE AREA. ANOTHER TRAILING SHORT WAVE CURRENTLY OVER
THE ROCKIES IS PROGGED TO MOVE SOUTHEAST ACROSS MISSOURI AND
CENTRAL/SOUTHERN ILLINOIS FRIDAY MORNING/EARLY AFTERNOON WHICH MAY
KEEP A LITTLE CLOUD COVER AROUND. OTHERWISE...DOMINANT WEATHER
FEATURE BECOMES A BROAD UPPER RIDGE CENTERED OVER WEST TEXAS WHICH
COVERS MUCH OF THE CENTRAL CONUS INTO THE WEEKEND. A STRONG 150+ KT
UPPER JET FLATTENS THE TOP OF THE RIDGE AS IT RIDES ALONG THE
CANADIAN BORDER FRIDAY...THOUGH THE MAIN AREA OF SFC LOW PRESSURE
REMAINS WELL NORTH OF THE GREAT LAKES REGION THROUGH SATURDAY. A
COLD FRONT DOES TRAIL INTO THE REGION HOWEVER...MOVING ACROSS THE
CWA EARLY SATURDAY MORNING. SOME GUIDANCE DOES INDICATE SOME VERY
SPOTTY/VERY LIGHT QPF WITH FROPA DURING THE PRE-DAWN HOURS SATURDAY
ALTHOUGH MODELS ARE MUCH LESS IMPRESSIVE WITH PRECIP THAN WITH
CURRENT WAVE...WITH SREF POPS LESS THAN 20 PERCENT. COLD FRONT
COMPLETES THE TRANSIT OF THE CWA SATURDAY MORNING...THOUGH PACIFIC
NATURE OF THE FRONT PRODUCES ONLY MODEST COOLING AS IT SHIFTS WINDS
TO THE WEST-NORTHWEST DURING THE DAY. LOW LEVEL THERMAL PROGS AND
POTENTIAL FOR A GOOD DEAL OF SUNSHINE SUPPORT TEMPS IN THE 65-AROUND
70 RANGE DESPITE THE SLIGHT COOL ADVECTION BEHIND THE FRONT...AS
UPPER RIDGE BEGINS TO AMPLIFY AND DEVELOP INTO THE CENTRAL CONUS
THROUGH SATURDAY NIGHT. UPPER RIDGE CONTINUES TO AMPLIFY SUNDAY AS
LARGE SCALE UPPER TROUGH PUSHES ASHORE IN THE WEST...WITH A LARGE
LEE TROUGH DEVELOPING EAST OF THE CENTRAL AND NORTHERN ROCKIES. LOW
PRESSURE BEGINS TO DEVELOP ACROSS THE PLAINS...WITH A WARM FRONT
LIFTING ACROSS IA-IL SUNDAY NIGHT. SOUTHEAST LOW LEVEL FLOW AHEAD OF
THE WARM FRONT...IN ADDITION TO CLOUD DEVELOPMENT NORTH OF THE WARM
FRONT LOOK TO TEMPER WARM-UP ONLY SLIGHTLY...WITH 60-66 FOR HIGHS
WITH COOLEST AIR ALONG THE IL LAKE SHORE. SOME POTENTIAL FOR
ELEVATED SHOWERS/ISOLATED THUNDERSTORMS NORTH OF THE WARM FRONT
SUNDAY NIGHT...PARTICULARLY ACROSS FAR NORTHERN IL.

WARM FRONT LIFTS NORTH OF THE CWA MONDAY...WITH BREEZY/WARM AND MORE
HUMID AIR IN THE WARM SECTOR SUPPORTING TEMPS IN THE 70S AREA-WIDE.
ECMWF/GFS AND GEM ALL INDICATE VERY LITTLE PRECIP IN THE WARM SECTOR
WITH THE MAIN FOCUS ALONG THE TRAILING COLD FRONT TO OUR WEST. RAIN
AND THUNDERSTORM CHANCES THUS INCREASE MONDAY NIGHT AND TUESDAY AS
THE SURFACE LOW PRESSURE CENTER LIFTS NORTHEAST ACROSS THE UPPER
MIDWEST AND TRAILING COLD FRONT PUSHES EAST THROUGH THE REGION.
BREEZY AND COOLER CONDITIONS THEN RETURN AS THE LOW PULLS AWAY TO
THE NORTHEAST TUESDAY NIGHT AND WEDNESDAY. SOME DIFFERENCES REMAIN
WITH THE HANDLING OF THE LOW DEVELOPMENT AND TRACK...THOUGH THIS
MAINLY AFFECTS HOW QUICKLY WE DRY OUT ON TUESDAY. OTHERWISE GUIDANCE
IS ACTUALLY QUITE REASONABLE IN AGREEMENT THROUGH THE PERIOD.

RATZER

&&

.AVIATION...

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

* SW WINDS GUSTING TO ARND 17KT THIS AFTN.

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL.

JEE

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

AN UPPER LEVEL WAVE IS APPROACHING FROM THE WEST WITH A LINE OF
SHOWERS EXTENDING INTO NORTHWEST IL. THE BAND OF SHOWERS WILL
CONTINUE EAST AND EXPECTING IT TO REMAIN RAGGED WITH HIT OR MISS
SHOWERS. RFD HAS THE BEST CHANCE OF SEEING AN ORGANIZED SHOWER
THIS AFTN. THE EASTERN TERMINALS WILL MOST LIKELY SEE SCATTERED
SHOWERS OR DRIZZLE THIS EVENING.

UPSTREAM OBS INDICATE THAT CIGS WILL FALL TO MVFR OR LOWER BEHIND
THE SHOWERS. HAVE THE MOST CONFIDENCE IN THE RFD TAF WITH IFR
CIGS. HAVE HIGH CONFIDENCE IN FOG AT RFD AND MEDIUM IN 1/4SM.

CLOUDS SHOULD LAST LONGER OVER THE EASTERN TERMINALS SO KEPT CIGS
IN THE MVFR RANGE WITH FOG ONLY AT DPA. CONDITIONS WILL IMPROVE TO
VFR QUICKLY TOMORROW AS THE CLOUDS SHIFT EAST. LIGHT WINDS
OVERNIGHT BECOME SW BTWN 5 AND 8 KT.

JEE

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

* MEDIUM CONFIDENCE IN COVERAGE AND OCCURRENCE OF -SHRA...MEDIUM-
  HIGH CONFIDENCE IN TIMING.

* MEDIUM CONFIDENCE IN MVFR CIGS AND TIMING...LOW CONFIDENCE IN
  HOW LOW THE CIGS WILL BE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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








000
FXUS63 KLOT 231946
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
246 PM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SW WINDS GUSTING TO ARND 17KT THIS AFTN.

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL.

JEE

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

AN UPPER LEVEL WAVE IS APPROACHING FROM THE WEST WITH A LINE OF
SHOWERS EXTENDING INTO NORTHWEST IL. THE BAND OF SHOWERS WILL
CONTINUE EAST AND EXPECTING IT TO REMAIN RAGGED WITH HIT OR MISS
SHOWERS. RFD HAS THE BEST CHANCE OF SEEING AN ORGANIZED SHOWER
THIS AFTN. THE EASTERN TERMINALS WILL MOST LIKELY SEE SCATTERED
SHOWERS OR DRIZZLE THIS EVENING.

UPSTREAM OBS INDICATE THAT CIGS WILL FALL TO MVFR OR LOWER BEHIND
THE SHOWERS. HAVE THE MOST CONFIDENCE IN THE RFD TAF WITH IFR
CIGS. HAVE HIGH CONFIDENCE IN FOG AT RFD AND MEDIUM IN 1/4SM.

CLOUDS SHOULD LAST LONGER OVER THE EASTERN TERMINALS SO KEPT CIGS
IN THE MVFR RANGE WITH FOG ONLY AT DPA. CONDITIONS WILL IMPROVE TO
VFR QUICKLY TOMORROW AS THE CLOUDS SHIFT EAST. LIGHT WINDS
OVERNIGHT BECOME SW BTWN 5 AND 8 KT.

JEE

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

* MEDIUM CONFIDENCE IN COVERAGE AND OCCURRENCE OF -SHRA...MEDIUM-
  HIGH CONFIDENCE IN TIMING.

* MEDIUM CONFIDENCE IN MVFR CIGS AND TIMING...LOW CONFIDENCE IN
  HOW LOW THE CIGS WILL BE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 231946
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
246 PM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SW WINDS GUSTING TO ARND 17KT THIS AFTN.

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL.

JEE

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

AN UPPER LEVEL WAVE IS APPROACHING FROM THE WEST WITH A LINE OF
SHOWERS EXTENDING INTO NORTHWEST IL. THE BAND OF SHOWERS WILL
CONTINUE EAST AND EXPECTING IT TO REMAIN RAGGED WITH HIT OR MISS
SHOWERS. RFD HAS THE BEST CHANCE OF SEEING AN ORGANIZED SHOWER
THIS AFTN. THE EASTERN TERMINALS WILL MOST LIKELY SEE SCATTERED
SHOWERS OR DRIZZLE THIS EVENING.

UPSTREAM OBS INDICATE THAT CIGS WILL FALL TO MVFR OR LOWER BEHIND
THE SHOWERS. HAVE THE MOST CONFIDENCE IN THE RFD TAF WITH IFR
CIGS. HAVE HIGH CONFIDENCE IN FOG AT RFD AND MEDIUM IN 1/4SM.

CLOUDS SHOULD LAST LONGER OVER THE EASTERN TERMINALS SO KEPT CIGS
IN THE MVFR RANGE WITH FOG ONLY AT DPA. CONDITIONS WILL IMPROVE TO
VFR QUICKLY TOMORROW AS THE CLOUDS SHIFT EAST. LIGHT WINDS
OVERNIGHT BECOME SW BTWN 5 AND 8 KT.

JEE

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

* MEDIUM CONFIDENCE IN COVERAGE AND OCCURRENCE OF -SHRA...MEDIUM-
  HIGH CONFIDENCE IN TIMING.

* MEDIUM CONFIDENCE IN MVFR CIGS AND TIMING...LOW CONFIDENCE IN
  HOW LOW THE CIGS WILL BE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...
244 PM CDT

HIGH PRESSURE WILL CONTINUE TO MOVE AWAY FROM LAKE MICHIGAN THROUGH
THE REMAINDER OF THE WEEK INTO THE WEEKEND AS LOW PRESSURE MOVES
EAST ACROSS THE CANADIAN PRAIRIES RESULTING IN GENERALLY SOUTH TO
SOUTHWEST FLOW OVER THE LAKE. THIS LOW WILL MOVE OVER JAMES BAY
SATURDAY DRAGGING A COLD FRONT ACROSS LAKE MICHIGAN AND TURNING
WINDS TO THE WEST/NORTHWEST. THE COLD AIR BEHIND THE FRONT IS SLOW
TO TRICKLE IN AND THE AIRMASS IS SHALLOW...SO WHILE THERE ARE
GALES JUST OFF THE DECK...IT DOESNT APPEAR THAT THEY WOULD MIX
DOWN TO THE LAKE SURFACE AT THIS TIME. WINDS WILL PEAK
OCCASIONALLY TO 30 KT SATURDAY AND SATURDAY NIGHT...THEN SHOULD
TREND DOWN THROUGH THE DAY SUNDAY AS HIGH PRESSURE BUILDS BACK
OVER THE REGION. ANOTHER AREA OF LOW PRESSURE IS PROGGED TO LIFT
ACROSS THE REGION AROUND MIDWEEK NEXT WEEK AND WILL ONCE AGAIN
BRING MODERATE WINDS TO LAKE MICHIGAN.

BMD

&&

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

$$

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

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







000
FXUS63 KLOT 231737
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1237 PM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SW WINDS GUSTING TO ARND 17KT THIS AFTN.

* SCATTERED -SHRA THIS EVENING.

* MVFR CIGS EXPECTED AFTER THE SHOWERS...IFR PSBL.

JEE

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

AN UPPER LEVEL WAVE IS APPROACHING FROM THE WEST WITH A LINE OF
SHOWERS EXTENDING INTO NORTHWEST IL. THE BAND OF SHOWERS WILL
CONTINUE EAST AND EXPECTING IT TO REMAIN RAGGED WITH HIT OR MISS
SHOWERS. RFD HAS THE BEST CHANCE OF SEEING AN ORGANIZED SHOWER
THIS AFTN. THE EASTERN TERMINALS WILL MOST LIKELY SEE SCATTERED
SHOWERS OR DRIZZLE THIS EVENING.

UPSTREAM OBS INDICATE THAT CIGS WILL FALL TO MVFR OR LOWER BEHIND
THE SHOWERS. HAVE THE MOST CONFIDENCE IN THE RFD TAF WITH IFR
CIGS. HAVE HIGH CONFIDENCE IN FOG AT RFD AND MEDIUM IN 1/4SM.

CLOUDS SHOULD LAST LONGER OVER THE EASTERN TERMINALS SO KEPT CIGS
IN THE MVFR RANGE WITH FOG ONLY AT DPA. CONDITIONS WILL IMPROVE TO
VFR QUICKLY TOMORROW AS THE CLOUDS SHIFT EAST. LIGHT WINDS
OVERNIGHT BECOME SW BTWN 5 AND 8 KT.

JEE


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

* MEDIUM CONFIDENCE IN COVERAGE AND OCCURRENCE OF -SHRA...MEDIUM-
  HIGH CONFIDENCE IN TIMING.

* MEDIUM CONFIDENCE IN MVFR CIGS AND TIMING...LOW CONFIDENCE IN
  HOW LOW THE CIGS WILL BE.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 231605
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1105 AM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* S WINDS 10-12 KTS...WITH A FEW HIGHER GUSTS PSBL LATE AFTN.

* CHANCE OF SHRA THIS EVENING.

* MVFR CIGS TONIGHT.

* FOG PSBL FRIDAY MORNING.

JEE

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

LIGHT FOG HAS FORMED ACROSS NORTHEAST IL AND SOME OF THE TERMINALS
BUT THIS SHOULD BE SHORT LIVED THIS MORNING. FURTHER EAST INTO
NORTHWEST INDIANA...MORE WIDESPREAD AND DENSE FOG HAS DEVELOPED
AND THIS WILL TAKE A FEW HOURS TO DISSIPATE LATER THIS MORNING.

A WEAK TROUGH MOVING ACROSS MN AND IA WILL REACH THE AREA LATER
THIS AFTERNOON AND THIS EVENING AS IT DISSIPATES. LIGHT SHOWERS
WILL BE POSSIBLE ACROSS NORTHWEST IL BY EARLY THIS AFTERNOON AND
THEN ACROSS THE REST OF TERMINALS MAINLY THIS EVENING. STILL
FAIRLY LOW CONFIDENCE REGARDING COVERAGE AND INTENSITY SO HAVE
KEPT VICINITY MENTION. VFR CIGS ARE EXPECTED UNTIL THIS EVENING
WHEN PRECIP SATURATES THE LOW LEVELS AND MVFR CIGS ARE EXPECTED
TO DEVELOP. THESE CIGS SHOULD BEGIN TO CLEAR ACROSS NORTHWEST IL
OVERNIGHT AND POSSIBLY AS FAR EAST AS ORD/MDW BY SUNRISE FRIDAY
MORNING. WHERE CLOUDS DO CLEAR...EXPECT FOG TO DEVELOP WHICH MAY
BECOME DENSE. INCLUDED FOG AT RFD/DPA AS CONFIDENCE FURTHER EAST
IS TOO LOW AT THIS TIME.

SOUTH/SOUTHEAST WINDS 4-8KTS TO START WILL INCREASE TO 10-12KTS
THIS MORNING AND TURN TO THE SOUTH/SOUTHWEST. THERE WILL ALSO
LIKELY BE SOME GUSTS INTO THE 15-17KT RANGE BUT NOT SURE HOW
PREVAILING THEY WILL BECOME. THUS LEFT THEM OUT OF THIS FORECAST
AND TRENDS WILL NEED TO BE MONITORED. WINDS TURN LIGHT SOUTHWEST
THIS EVENING AND THEN WILL BECOME LIGHT AND VARIABLE TONIGHT. CMS

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

* HIGH CONFIDENCE IN WIND DIRECTION...MEDIUM FOR SPEEDS AND
  POSSIBLE GUSTS.

* MEDIUM CONFIDENCE IN SHRA OCCURRENCE AND TIMING THIS EVE.

* MEDIUM CONFIDENCE IN MVFR CIGS TONIGHT AND TIMING.

* LOW CONFIDENCE IN FOG FRIDAY MORNING.

JEE

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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 231347
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
847 AM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* S WINDS 10-12 KTS...WITH A FEW HIGHER GUSTS PSBL MID MORNING
  THRU LATE AFTN.

* CHANCE OF SHRA LATE THIS AFTN THRU MID EVENING.

* MVFR CIGS TONIGHT.

* FOG PSBL FRIDAY MORNING.

JEE

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

LIGHT FOG HAS FORMED ACROSS NORTHEAST IL AND SOME OF THE TERMINALS
BUT THIS SHOULD BE SHORT LIVED THIS MORNING. FURTHER EAST INTO
NORTHWEST INDIANA...MORE WIDESPREAD AND DENSE FOG HAS DEVELOPED
AND THIS WILL TAKE A FEW HOURS TO DISSIPATE LATER THIS MORNING.

A WEAK TROUGH MOVING ACROSS MN AND IA WILL REACH THE AREA LATER
THIS AFTERNOON AND THIS EVENING AS IT DISSIPATES. LIGHT SHOWERS
WILL BE POSSIBLE ACROSS NORTHWEST IL BY EARLY THIS AFTERNOON AND
THEN ACROSS THE REST OF TERMINALS MAINLY THIS EVENING. STILL
FAIRLY LOW CONFIDENCE REGARDING COVERAGE AND INTENSITY SO HAVE
KEPT VICINITY MENTION. VFR CIGS ARE EXPECTED UNTIL THIS EVENING
WHEN PRECIP SATURATES THE LOW LEVELS AND MVFR CIGS ARE EXPECTED
TO DEVELOP. THESE CIGS SHOULD BEGIN TO CLEAR ACROSS NORTHWEST IL
OVERNIGHT AND POSSIBLY AS FAR EAST AS ORD/MDW BY SUNRISE FRIDAY
MORNING. WHERE CLOUDS DO CLEAR...EXPECT FOG TO DEVELOP WHICH MAY
BECOME DENSE. INCLUDED FOG AT RFD/DPA AS CONFIDENCE FURTHER EAST
IS TOO LOW AT THIS TIME.

SOUTH/SOUTHEAST WINDS 4-8KTS TO START WILL INCREASE TO 10-12KTS
THIS MORNING AND TURN TO THE SOUTH/SOUTHWEST. THERE WILL ALSO
LIKELY BE SOME GUSTS INTO THE 15-17KT RANGE BUT NOT SURE HOW
PREVAILING THEY WILL BECOME. THUS LEFT THEM OUT OF THIS FORECAST
AND TRENDS WILL NEED TO BE MONITORED. WINDS TURN LIGHT SOUTHWEST
THIS EVENING AND THEN WILL BECOME LIGHT AND VARIABLE TONIGHT. CMS

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

* HIGH CONFIDENCE IN WIND DIRECTION...MEDIUM FOR SPEEDS AND
  POSSIBLE GUSTS.

* MEDIUM CONFIDENCE IN SHRA AND TIMING THIS AFTN/EVE.

* MEDIUM CONFIDENCE IN MVFR CIGS TONIGHT.

* LOW CONFIDENCE IN FOG FRIDAY MORNING.

JEE

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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 231150
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
650 AM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SOUTHERLY WINDS 10-12 KTS...WITH A FEW HIGHER GUSTS POSSIBLE...
  MID MORNING THRU LATE AFTERNOON.
* CHANCE OF SHRA LATE AFTERNOON THRU MID EVENING.
* MVFR CIGS TONIGHT.
* FOG POSSIBLE FRIDAY MORNING. CMS

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

LIGHT FOG HAS FORMED ACROSS NORTHEAST IL AND SOME OF THE TERMINALS
BUT THIS SHOULD BE SHORT LIVED THIS MORNING. FURTHER EAST INTO
NORTHWEST INDIANA...MORE WIDESPREAD AND DENSE FOG HAS DEVELOPED
AND THIS WILL TAKE A FEW HOURS TO DISSIPATE LATER THIS MORNING.

A WEAK TROUGH MOVING ACROSS MN AND IA WILL REACH THE AREA LATER
THIS AFTERNOON AND THIS EVENING AS IT DISSIPATES. LIGHT SHOWERS
WILL BE POSSIBLE ACROSS NORTHWEST IL BY EARLY THIS AFTERNOON AND
THEN ACROSS THE REST OF TERMINALS MAINLY THIS EVENING. STILL
FAIRLY LOW CONFIDENCE REGARDING COVERAGE AND INTENSITY SO HAVE
KEPT VICINITY MENTION. VFR CIGS ARE EXPECTED UNTIL THIS EVENING
WHEN PRECIP SATURATES THE LOW LEVELS AND MVFR CIGS ARE EXPECTED
TO DEVELOP. THESE CIGS SHOULD BEGIN TO CLEAR ACROSS NORTHWEST IL
OVERNIGHT AND POSSIBLY AS FAR EAST AS ORD/MDW BY SUNRISE FRIDAY
MORNING. WHERE CLOUDS DO CLEAR...EXPECT FOG TO DEVELOP WHICH MAY
BECOME DENSE. INCLUDED FOG AT RFD/DPA AS CONFIDENCE FURTHER EAST
IS TOO LOW AT THIS TIME.

SOUTH/SOUTHEAST WINDS 4-8KTS TO START WILL INCREASE TO 10-12KTS
THIS MORNING AND TURN TO THE SOUTH/SOUTHWEST. THERE WILL ALSO
LIKELY BE SOME GUSTS INTO THE 15-17KT RANGE BUT NOT SURE HOW
PREVAILING THEY WILL BECOME. THUS LEFT THEM OUT OF THIS FORECAST
AND TRENDS WILL NEED TO BE MONITORED. WINDS TURN LIGHT SOUTHWEST
THIS EVENING AND THEN WILL BECOME LIGHT AND VARIABLE TONIGHT. CMS

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

* HIGH FOR WIND DIRECTION...MEDIUM FOR SPEEDS AND POSSIBLE GUSTS.
* MEDIUM FOR SHRA LATE AFTERNOON/EARLY EVENING.
* MEDIUM FOR MVFR CIGS TONIGHT.
* LOW FOR FOG FRIDAY MORNING. CMS

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

* FRIDAY NIGHT...DRY. MVFR/FOG POSSIBLE.
* SATURDAY...DRY/VFR. GUSTY WEST/NORTHWEST WINDS.
* SUNDAY...DRY/VFR. WEST WINDS BECOMING SOUTHEAST.
* MONDAY...DRY/VFR. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.
* WEDNESDAY...CHANCE OF SHRA. WEST WINDS.

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 230904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SOUTHERLY WINDS 10-12 KTS MID MORNING THRU LATE AFTERNOON.
* CHANCE OF SHRA LATE AFTERNOON/EARLY EVENING.
* MVFR CIGS TONIGHT. CMS

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

A WEAK COLD FRONT/TROUGH WILL MOVE ACROSS THE AREA LATER THIS
AFTERNOON AND THIS EVENING...AS IT WEAKENS. LIGHT SOUTHEAST WINDS
WILL TURN MORE SOUTH/SOUTHWEST BY MID MORNING AND INCREASE INTO
THE 10-12KT RANGE WITH SOME HIGHER GUSTS POSSIBLE THRU EARLY
AFTERNOON. SHOWERS ARE EXPECTED TO SPREAD INTO NORTHWEST IL BY
EARLY AFTERNOON AND THEN ACROSS THE REST OF THE AREA BY LATE
AFTERNOON AND EARLY EVENING. NO CHANGE TO TIMING WHICH LOOKS ON
TRACK BUT OVERALL COVERAGE AND INTENSITY REMAINS SOMEWHAT LOWER
AT THE CHICAGO AREA TERMINALS AND BACKED OFF TO VICINITY MENTION
FOR NOW. CIGS SHOULD REMAIN VFR UNTIL THE SHOWERS END AND THEN
LOWER TO MVFR THIS EVENING...EARLIER AT RFD. AS CLOUDS CLEAR FROM
WEST TO EAST LATE TONIGHT/EARLY FRIDAY MORNING...SOME FOG WILL BE
POSSIBLE. CMS

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

* HIGH FOR WIND DIRECTION...MEDIUM FOR SPEEDS AND POSSIBLE GUSTS.
* MEDIUM FOR SHRA LATE AFTERNOON/EARLY EVENING.
* MEDIUM FOR MVFR CIGS TONIGHT. CMS

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 230812
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
312 AM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SOUTHERLY WINDS 10-12 KTS MID MORNING THRU LATE AFTERNOON.
* CHANCE OF SHRA LATE AFTERNOON/EARLY EVENING.
* MVFR CIGS TONIGHT. CMS

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

A WEAK COLD FRONT/TROUGH WILL MOVE ACROSS THE AREA LATER THIS
AFTERNOON AND THIS EVENING...AS IT WEAKENS. LIGHT SOUTHEAST WINDS
WILL TURN MORE SOUTH/SOUTHWEST BY MID MORNING AND INCREASE INTO
THE 10-12KT RANGE WITH SOME HIGHER GUSTS POSSIBLE THRU EARLY
AFTERNOON. SHOWERS ARE EXPECTED TO SPREAD INTO NORTHWEST IL BY
EARLY AFTERNOON AND THEN ACROSS THE REST OF THE AREA BY LATE
AFTERNOON AND EARLY EVENING. NO CHANGE TO TIMING WHICH LOOKS ON
TRACK BUT OVERALL COVERAGE AND INTENSITY REMAINS SOMEWHAT LOWER
AT THE CHICAGO AREA TERMINALS AND BACKED OFF TO VICINITY MENTION
FOR NOW. CIGS SHOULD REMAIN VFR UNTIL THE SHOWERS END AND THEN
LOWER TO MVFR THIS EVENING...EARLIER AT RFD. AS CLOUDS CLEAR FROM
WEST TO EAST LATE TONIGHT/EARLY FRIDAY MORNING...SOME FOG WILL BE
POSSIBLE. CMS

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

* HIGH FOR WIND DIRECTION...MEDIUM FOR SPEEDS AND POSSIBLE GUSTS.
* MEDIUM FOR SHRA LATE AFTERNOON/EARLY EVENING.
* MEDIUM FOR MVFR CIGS TONIGHT. CMS

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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








000
FXUS63 KLOT 230812
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
312 AM CDT THU OCT 23 2014

.DISCUSSION...
303 AM CDT

A RIDGE OF HIGH PRESSURE STRETCHES FROM CENTRAL QUEBEC SOUTHWEST
THROUGH LOWER MICHIGAN INTO THE OHIO VALLEY. EARLY THIS MORNING THIS
RIDGE HAS BEEN ABLE TO KEEP CLOUD COVER DISPLACED WEST OF THE
REGION. BASED ON LATEST SFC OBS THE PRESSURE FALLS ARE NOT VERY
LARGE...WHICH COULD BE AN INDICATOR THAT LATER TODAY THE ABILITY FOR
THE ATMOSPHERE TO PRODUCE ABUNDANT MOISTURE/PRECIP MAY BE
DIMINISHED. IR IMAGERY EARLY THIS MORNING SHOWS A MOIST CHANNEL THAT
EXTENDS FROM THE CANADIAN BORDER OF THE UPPER MIDWEST...SOUTH TO
THE MEXICO BORDER/WESTERN GULF. THE PROGRESSION TO THE EAST HAS BEEN
VERY SLOW...AND LATEST HI-RES GUIDANCE INDICATES THAT AS THIS
FEATURE PUSHES EAST IT WILL ENCOUNTER MUCH DRIER AIR AND DIMINISH
THE COVERAGE AND INTENSITY OF PRECIP.

WITH THE LGT WINDS AND MINIMAL CLOUD COVER EARLY THIS MORNING...SOME
LOCATIONS ARE BEGINNING TO SEE PATCHY FOG DEVELOP...MAINLY ACROSS
NORTHWEST INDIANA. TEMPS HAVE BEEN ABLE TO RADIATE INTO THE MID
30S...WITH THE EXCEPTION OF THE FAR WESTERN CWFA WHERE A THIN
CIRRUS DECK HAS ARRIVED AND HELD TEMPS IN THE UPR 30S/NEAR 40.

AS THE MOIST CHANNEL SLOWLY SLIDES EAST TODAY...EXPECT A STEADY
THICKENING TO THE CLOUD COVER. WINDS WILL TURN SOUTHERLY WITH SOME
BETTER MIXING DEVELOPING AND PERHAPS BRINGING WINDS UP TO 10-20MPH
BY LATE AFTN. GUIDANCE HAS BECOME MORE PESSIMISTIC WITH PRECIP
COVERAGE/INTENSITY LATER TODAY...AND AS A RESULT HAVE BACKED OFF ON
POPS ALONG WITH QUANTITY OF PRECIP. THE NEAR SFC ENVIRONMENT STILL
LOOKS TO REMAIN RELATIVELY DRY...ALTHOUGH SOME MOISTENING WILL
OCCUR. EXPECT THE BEST PRECIP COVERAGE TO OCCUR FURTHER
NORTH...HOWEVER WILL CONTINUE THE MENTION OF LGT RAIN ACROSS ENTIRE
FORECAST AREA LATE THIS AFTN/EARLY EVE. TROUGH AXIS WILL BE SLIDING
EAST ACROSS EAST-CENTRAL WISC BY 3Z. TEMPS TODAY WILL WARM INTO THE
50S FOR MUCH OF THE AREA...AND SOUTH OF I-80 A FEW 60S.

FOR TONIGHT ON THE BACK SIDE OF THE TROUGH...AND DEPARTING
PRECIP/CLOUD COVER...THERE IS SOME CONCERN THAT PATCHY FOG WILL
DEVELOP. UPSTREAM THIS HAS ALREADY BEEN NOTED...AND EXPECT THIS
SIMILAR SETUP TO OCCUR OVER A PORTION OF THE CWFA OVERNIGHT TONIGHT
BUT WILL HINGE UPON HOW QUICKLY CLOUDS WILL DEPART. LOWS WILL
GENERALLY BE IN THE MID/UPR 40S.

FRIDAY THROUGH SUNDAY...
A WEAK LOBE OF VORTICITY IS PROGGED TO SLIDE EAST ACROSS THE CENTRAL
PLAINS...ARRIVING OVER THE FORECAST AREA FRI AFTN/EVE. LOCAL ARW8KM
GUIDANCE AND NAM SUGGEST SOME LGT PRECIP MAY DEVELOP WITH THIS
SYSTEM...BUT NOT EXPECTING MUCH TO THE COVERAGE AT THIS TIME. HAVE
OPTED TO HOLD ONTO THE DRY FORECAST...BUT MAY NEED TO ADJUST POPS
SLIGHTLY TO REFLECT A FEW SPRINKLES/LGT RAIN SHOWERS. THEN BY EARLY
SAT MORNING ANTI-CYCLONIC FLOW BUILDS INTO THE REGION AND DRIES THE
ATMOSPHERE OUT. SFC RIDGE WILL REMAIN IN PLACE THRU SUN...THEN THE
MID-LVL RIDGE OVERHEAD FLATTENS AND THE FLOW BECOMES QUASI-ZONAL FOR
LATE IN THE WEEKEND INTO EARLY NEXT WEEK.

TEMPS FRI-SUN WILL BE SLOWLY MODERATING...WITH HIGHS IN THE 60S TO
PERHAPS A FEW LOW 70S FRI/SAT. A WEAK FRONTAL BOUNDARY WILL SLIDE
ACROSS THE REGION SUN AND COULD BRING TEMPS BACK INTO THE UPR
50S/LOW 60S.

MONDAY-WEDNESDAY...
ENSEMBLES ARE SHOWING THE WESTERN CONUS TROUGH PUSHING EAST BY EARLY
NEXT WEEK...HELPING TO SETUP THE POTENTIAL FOR PERIODIC CHANCES FOR
SHOWERS AND PERHAPS A FEW THUNDERSTORMS IN THE MON/TUE TIMEFRAME.
TEMPS MON SHUD REBOUND WITH A SOUTHWEST FLOW AND PUSH INTO THE UPR
60S/LOW 70S. THEN INCREASED CLOUD COVER TUE/WED WILL KEEP TEMPS IN
THE UPR 50S TO LOW 60S.

BEACHLER

&&

.AVIATION...

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

* SOUTHERLY WINDS 10-12 KTS MID MORNING THRU LATE AFTERNOON.
* CHANCE OF SHRA LATE AFTERNOON/EARLY EVENING.
* MVFR CIGS TONIGHT. CMS

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

A WEAK COLD FRONT/TROUGH WILL MOVE ACROSS THE AREA LATER THIS
AFTERNOON AND THIS EVENING...AS IT WEAKENS. LIGHT SOUTHEAST WINDS
WILL TURN MORE SOUTH/SOUTHWEST BY MID MORNING AND INCREASE INTO
THE 10-12KT RANGE WITH SOME HIGHER GUSTS POSSIBLE THRU EARLY
AFTERNOON. SHOWERS ARE EXPECTED TO SPREAD INTO NORTHWEST IL BY
EARLY AFTERNOON AND THEN ACROSS THE REST OF THE AREA BY LATE
AFTERNOON AND EARLY EVENING. NO CHANGE TO TIMING WHICH LOOKS ON
TRACK BUT OVERALL COVERAGE AND INTENSITY REMAINS SOMEWHAT LOWER
AT THE CHICAGO AREA TERMINALS AND BACKED OFF TO VICINITY MENTION
FOR NOW. CIGS SHOULD REMAIN VFR UNTIL THE SHOWERS END AND THEN
LOWER TO MVFR THIS EVENING...EARLIER AT RFD. AS CLOUDS CLEAR FROM
WEST TO EAST LATE TONIGHT/EARLY FRIDAY MORNING...SOME FOG WILL BE
POSSIBLE. CMS

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

* HIGH FOR WIND DIRECTION...MEDIUM FOR SPEEDS AND POSSIBLE GUSTS.
* MEDIUM FOR SHRA LATE AFTERNOON/EARLY EVENING.
* MEDIUM FOR MVFR CIGS TONIGHT. CMS

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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








000
FXUS63 KLOT 230745
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
245 AM CDT THU OCT 23 2014

.DISCUSSION...
310 PM CDT

SHORT TERM...THIS AFTERNOON THROUGH TONIGHT...FOR THE REMAINDER OF
THE AFTERNOON AND TONIGHT...MOSTLY CLEAR SKIES AND SLIGHTLY HIGHER
TEMPERATURES ARE MAKING FOR A TRANSITION DAY TODAY BEFORE A MORE
NOTABLE WARMING TREND EXPECTED FOR THE NEXT FEW DAYS. UNDER THE
CLEAR SKIES AND LIGHT WINDS...TEMPERATURES THIS AFTERNOON ARE
CLIMBING INTO THE LOW 50S NEAR LAKE MICHIGAN TO AROUND 60F WELL
INLAND.  A RIDGE OF HIGH PRESSURE MOVING ACROSS THE WESTERN GREAT
LAKES HAS SET UP LIGHT ONSHORE FLOW NEAR THE LAKE...PREVENTING THE
WARMER CONDITIONS NEAR THE LAKE.  FOR TONIGHT...UNDER CLEAR
SKIES...LIGHT WINDS AND WITH A RELATIVELY DRY AIRMASS IN
PLACE...TEMPERATURES WILL ONCE AGAIN HAVE AN OPPORTUNITY TO RADIATE
DOWN INTO THE MIDDLE TO UPPER 30S.  THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD REMAIN A BIT WARMER...WITH LOWS ONLY
IN THE LOWER 40S.  EVEN THOUGH THE AIRMASS IS EXPECTED TO BE
RELATIVELY DRY...DEWPOINTS SHOULD BE THE LOWER TO MIDDLE 30S...SO
TEMPERATURES WILL LIKELY RADIATE CLOSE TO THE DEWPOINTS.  DO NOT
ANTICIPATE WIDESPREAD DENSE FOG...BUT RATHER THERE COULD MORE LIKELY
BE SOME PATCHY...SHALLOW GROUND FOG IN LOW-LYING...SHELTERED...RURAL
LOCATIONS.

LONGER TERM...THURSDAY THROUGH WEDNESDAY...AS THE HIGH SLIDES OFF TO
THE EAST AND A SFC TROUGH AND ASSOCIATED COLD FRONT CROSS THE
CENTRAL PLAINS...A RETURN FLOW OF SLIGHTLY WARMER...MOISTER AIR WILL
SET UP.  WHILE THE NORTHERN PORTION OF THE SFC HIGH WILL PUSH WELL
EAST OF THE AREA...THE MIDWEST WILL REMAIN CUT OFF FROM THE RICHER
GULF MOISTURE AS A RIDGE AXIS EXTENDS SWWD THROUGH ERN TX.  THIS
COMBINATION WILL AFFECT BOTH MAX TEMP POTENTIAL FOR THE DAY AS WELL
AS PCPN POTENTIAL WITH THE PASSAGE OF THE COLD FRONT.  WHILE
INCREASING CLOUD COVER WILL SOMEWHAT TEMPER THE POTENTIAL MAX TEMPS
FOR THE DAY...HIGHS THURSDAY SHOULD RANGE FROM THE UPPER 50S TO
AROUND 60F.  AS FOR PCPN POTENTIAL...THERE SHOULD BE ADEQUATE SFC
FORCING WITH THE COLD FRONT AS WELL AS MID LEVEL FORCING FROM A NRN
STREAM SHORTWAVE TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY AND
WRN GREAT LAKES AS WELL AS SOME PHASING WITH A SRN STREAM SHORTWAVE
PASSING ACROSS THE MIDDLE MISSISSIPPI VALLEY.  EVEN THOUGH THE
SURFACE LAYER WILL BE SOMEWHAT CUT OFF FROM THE RICHEST LOW LEVEL
GULF MOISTURE...THE SRN STREAM SHORT WAVE WILL BRING SOME ENHANCED
MID LEVEL MOISTURE...SO THE OVERALL MOISTURE PROFILE WILL STILL BE
RELATIVELY MOIST WITH THE MODELS INDICATING PWATS OF AROUND 1 INCH
WITH THE FROPA.  SO...EXPECT THAT ENTIRE CWA SHOULD SEE WETTING
RAINFALL THROUGH THE DAY TOMORROW...POSSIBLY LINGERING INTO TOMORROW
EVENING OVER THE FAR ERN PORTIONS OF THE CWA...THE STEADILY
PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO
ARND A TENTH TO A QUARTER OF AN INCH WITH SOME OF THE HEAVIER
SHOWERS.  MODELS SOUNDINGS INDICATE LITTLE OR NO CAPE...SO THUNDER
SHOULD NOT BE AN ISSUE.

FOLLOWING THE PASSAGE OF THE FRONT...THE REAL WARMING TREND WILL
BEGIN IN EARNEST ON FRIDAY AS UPPER RIDGING BUILDS ACROSS THE
ROCKIES AND INTO THE WESTERN PLAINS...WHILE THE UPPER TROUGH AND
COLD FRONT MOVE TO THE EAST COAST.  BY FRIDAY...850MB TEMPS ARND 15C
WILL MOVE ACROSS THE AREA AND EXPECT THAT TEMPS SHOULD REACH INTO
THE MIDDLE TO UPPER 60S.  BY SATURDAY...THE THERMAL AXIS WILL SHIFT
TO THE SOUTH...ACROSS CNTRL/SRN IL/IN WHILE A DEEP UPPER LOW TRACKS
ACROSS THE UPPER GREAT LAKES.  THIS WILL LEAD TO MORE NWLY FLOW
ACROSS THE UPPER MIDWEST...AND POSSIBLY LIMITING WARMING ACROSS THE
NRN PORTIONS OF THE AREA...SO...WILL CARRY TEMPS IN THE LOWER TO
MIDDLE 60S NORTH OF THE I-80 CORRIDOR WITH TEMPS IN THE UPPER 60S
ACROSS THE SRN PORTIONS OF THE CWA.  WITH ENOUGH SUNSHINE...SOME 70F
MAX TEMPS ARE NOT OUT OF THE QUESTION FOR LOCATIONS SOUTH OF A
PONTIAC TO REMINGTON LINE.  THE RELATIVELY WARM AND DRY WEATHER WILL
PERSIST THROUGH THE WEEKEND AS THE UPPER RIDGE SLOWLY PROGRESSES
ACROSS THE CENTRAL CONUS.

THE NEXT SIGNIFICANT CHANCE FOR PCPN WILL NOT BE UNTIL EARLY NEXT
WEEK WHEN THE UPPER RIDGE BUILDS TO THE EAST COAST AND A STRONG
PACIFIC SHORTWAVE DROPS FROM THE PACIFIC NORTHWEST TO THE FOUR
CORNERS AREA BY MONDAY AFTERNOON.  THIS WILL SET UP STRONG SWLY FLOW
ALOFT...WITH A TRAIN OF SOUTHERN STREAM SHORTWAVE ENERGY...WHILE AN
OPEN GULF OF MEXICO EVOLVES AT THE SURFACE.  INCREASED LOW LEVEL
MOISTURE AND MID LEVEL SHORT WAVE ENERGY WILL BRING A CHANCE FOR
SHOWERS AND POSSIBLY SOME THUNDERSTORMS FOR MONDAY NIGHT AND INTO
TUESDAY.  THE UNSEASONABLY HIGH TEMPERATURES WILL COME TO AN END BY
EARLY NEXT WEEK AS ANOTHER COLD FRONT IS EXPECTED TO CROSS THE
REGION.  THE LATEST LONG RANGE GUIDANCE SUGGESTS THAT THIS FRONT
SHOULD PUSH THROUGH THE AREA BY TUESDAY NIGHT OR WEDNESDAY...
BRINGING MAX TEMPS BACK INTO THE 50S.

KREIN

&&

.AVIATION...

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

* SOUTHERLY WINDS 10-12 KTS MID MORNING THRU LATE AFTERNOON.
* CHANCE OF SHRA LATE AFTERNOON/EARLY EVENING.
* MVFR CIGS TONIGHT. CMS

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

A WEAK COLD FRONT/TROUGH WILL MOVE ACROSS THE AREA LATER THIS
AFTERNOON AND THIS EVENING...AS IT WEAKENS. LIGHT SOUTHEAST WINDS
WILL TURN MORE SOUTH/SOUTHWEST BY MID MORNING AND INCREASE INTO
THE 10-12KT RANGE WITH SOME HIGHER GUSTS POSSIBLE THRU EARLY
AFTERNOON. SHOWERS ARE EXPECTED TO SPREAD INTO NORTHWEST IL BY
EARLY AFTERNOON AND THEN ACROSS THE REST OF THE AREA BY LATE
AFTERNOON AND EARLY EVENING. NO CHANGE TO TIMING WHICH LOOKS ON
TRACK BUT OVERALL COVERAGE AND INTENSITY REMAINS SOMEWHAT LOWER
AT THE CHICAGO AREA TERMINALS AND BACKED OFF TO VICINITY MENTION
FOR NOW. CIGS SHOULD REMAIN VFR UNTIL THE SHOWERS END AND THEN
LOWER TO MVFR THIS EVENING...EARLIER AT RFD. AS CLOUDS CLEAR FROM
WEST TO EAST LATE TONIGHT/EARLY FRIDAY MORNING...SOME FOG WILL BE
POSSIBLE. CMS

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

* HIGH FOR WIND DIRECTION...MEDIUM FOR SPEEDS AND POSSIBLE GUSTS.
* MEDIUM FOR SHRA LATE AFTERNOON/EARLY EVENING.
* MEDIUM FOR MVFR CIGS TONIGHT. CMS

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...

245 AM...FAIRLY ACTIVE PATTERN IS EXPECTED INTO EARLY NEXT WEEK.
HIGH PRESSURE EXTENDING FROM QUEBEC SOUTHWEST THROUGH THE CENTRAL
LAKES REGION WILL SPLIT TODAY...WITH THE HIGH WEAKENING AND MOVING
SOUTH INTO THE OHIO VALLEY TONIGHT. LOW PRESSURE OVER MANITOBA
WILL MOVE NORTH TODAY AS A WEAK COLD FRONT APPROACHES THE WESTERN
LAKES. THE GRADIENT WILL TIGHTEN SOME TODAY AHEAD OF THIS FRONT...
BUT THE FRONT IS EXPECTED TO DISSIPATE OVER THE WESTERN LAKES
TONIGHT. THUS WINDS MAY SHIFT WESTERLY FOR A TIME BUT WILL QUICKLY
GO BACK SOUTHWEST BY FRIDAY MORNING.

THE LOW LIFTING NORTH OVER MANITOBA WILL BE ABSORBED BY A STRONGER
LOW MOVING ACROSS CENTRAL CANADA TONIGHT AND FRIDAY. THIS LOW WILL
THEN MOVE ACROSS ONTARIO REACHING JAMES BAY SATURDAY AFTERNOON AS
IT DEEPENS. ANOTHER COLD FRONT TRAILING THIS LOW WILL MOVE ACROSS
LAKE MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY MORNING. AHEAD OF
THIS FRONT...SOUTHERLY WINDS WILL INCREASE AGAIN. BEHIND THE FRONT
WINDS WILL SHIFT NORTHWEST 20-25KTS AND MAY APPROACH 30 KTS FOR A
TIME SATURDAY AFTERNOON INTO SATURDAY EVENING.

A WEAK RIDGE WILL MOVE FROM THE PLAINS SATURDAY TO THE WESTERN
LAKES SUNDAY...WITH WINDS QUICKLY SHIFTING FROM WEST SUNDAY
MORNING TO SOUTH/SOUTHEAST SUNDAY EVENING. THE GRADIENT WILL THEN
TIGHTEN WITH INCREASING SOUTHERLY WINDS AS A LARGE AREA OF LOW
PRESSURE DEVELOPS OVER THE PLAINS SUNDAY INTO MONDAY. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 230527
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1227 AM CDT THU OCT 23 2014

.DISCUSSION...
310 PM CDT

SHORT TERM...THIS AFTERNOON THROUGH TONIGHT...FOR THE REMAINDER OF
THE AFTERNOON AND TONIGHT...MOSTLY CLEAR SKIES AND SLIGHTLY HIGHER
TEMPERATURES ARE MAKING FOR A TRANSITION DAY TODAY BEFORE A MORE
NOTABLE WARMING TREND EXPECTED FOR THE NEXT FEW DAYS. UNDER THE
CLEAR SKIES AND LIGHT WINDS...TEMPERATURES THIS AFTERNOON ARE
CLIMBING INTO THE LOW 50S NEAR LAKE MICHIGAN TO AROUND 60F WELL
INLAND.  A RIDGE OF HIGH PRESSURE MOVING ACROSS THE WESTERN GREAT
LAKES HAS SET UP LIGHT ONSHORE FLOW NEAR THE LAKE...PREVENTING THE
WARMER CONDITIONS NEAR THE LAKE.  FOR TONIGHT...UNDER CLEAR
SKIES...LIGHT WINDS AND WITH A RELATIVELY DRY AIRMASS IN
PLACE...TEMPERATURES WILL ONCE AGAIN HAVE AN OPPORTUNITY TO RADIATE
DOWN INTO THE MIDDLE TO UPPER 30S.  THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD REMAIN A BIT WARMER...WITH LOWS ONLY
IN THE LOWER 40S.  EVEN THOUGH THE AIRMASS IS EXPECTED TO BE
RELATIVELY DRY...DEWPOINTS SHOULD BE THE LOWER TO MIDDLE 30S...SO
TEMPERATURES WILL LIKELY RADIATE CLOSE TO THE DEWPOINTS.  DO NOT
ANTICIPATE WIDESPREAD DENSE FOG...BUT RATHER THERE COULD MORE LIKELY
BE SOME PATCHY...SHALLOW GROUND FOG IN LOW-LYING...SHELTERED...RURAL
LOCATIONS.

LONGER TERM...THURSDAY THROUGH WEDNESDAY...AS THE HIGH SLIDES OFF TO
THE EAST AND A SFC TROUGH AND ASSOCIATED COLD FRONT CROSS THE
CENTRAL PLAINS...A RETURN FLOW OF SLIGHTLY WARMER...MOISTER AIR WILL
SET UP.  WHILE THE NORTHERN PORTION OF THE SFC HIGH WILL PUSH WELL
EAST OF THE AREA...THE MIDWEST WILL REMAIN CUT OFF FROM THE RICHER
GULF MOISTURE AS A RIDGE AXIS EXTENDS SWWD THROUGH ERN TX.  THIS
COMBINATION WILL AFFECT BOTH MAX TEMP POTENTIAL FOR THE DAY AS WELL
AS PCPN POTENTIAL WITH THE PASSAGE OF THE COLD FRONT.  WHILE
INCREASING CLOUD COVER WILL SOMEWHAT TEMPER THE POTENTIAL MAX TEMPS
FOR THE DAY...HIGHS THURSDAY SHOULD RANGE FROM THE UPPER 50S TO
AROUND 60F.  AS FOR PCPN POTENTIAL...THERE SHOULD BE ADEQUATE SFC
FORCING WITH THE COLD FRONT AS WELL AS MID LEVEL FORCING FROM A NRN
STREAM SHORTWAVE TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY AND
WRN GREAT LAKES AS WELL AS SOME PHASING WITH A SRN STREAM SHORTWAVE
PASSING ACROSS THE MIDDLE MISSISSIPPI VALLEY.  EVEN THOUGH THE
SURFACE LAYER WILL BE SOMEWHAT CUT OFF FROM THE RICHEST LOW LEVEL
GULF MOISTURE...THE SRN STREAM SHORT WAVE WILL BRING SOME ENHANCED
MID LEVEL MOISTURE...SO THE OVERALL MOISTURE PROFILE WILL STILL BE
RELATIVELY MOIST WITH THE MODELS INDICATING PWATS OF AROUND 1 INCH
WITH THE FROPA.  SO...EXPECT THAT ENTIRE CWA SHOULD SEE WETTING
RAINFALL THROUGH THE DAY TOMORROW...POSSIBLY LINGERING INTO TOMORROW
EVENING OVER THE FAR ERN PORTIONS OF THE CWA...THE STEADILY
PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO
ARND A TENTH TO A QUARTER OF AN INCH WITH SOME OF THE HEAVIER
SHOWERS.  MODELS SOUNDINGS INDICATE LITTLE OR NO CAPE...SO THUNDER
SHOULD NOT BE AN ISSUE.

FOLLOWING THE PASSAGE OF THE FRONT...THE REAL WARMING TREND WILL
BEGIN IN EARNEST ON FRIDAY AS UPPER RIDGING BUILDS ACROSS THE
ROCKIES AND INTO THE WESTERN PLAINS...WHILE THE UPPER TROUGH AND
COLD FRONT MOVE TO THE EAST COAST.  BY FRIDAY...850MB TEMPS ARND 15C
WILL MOVE ACROSS THE AREA AND EXPECT THAT TEMPS SHOULD REACH INTO
THE MIDDLE TO UPPER 60S.  BY SATURDAY...THE THERMAL AXIS WILL SHIFT
TO THE SOUTH...ACROSS CNTRL/SRN IL/IN WHILE A DEEP UPPER LOW TRACKS
ACROSS THE UPPER GREAT LAKES.  THIS WILL LEAD TO MORE NWLY FLOW
ACROSS THE UPPER MIDWEST...AND POSSIBLY LIMITING WARMING ACROSS THE
NRN PORTIONS OF THE AREA...SO...WILL CARRY TEMPS IN THE LOWER TO
MIDDLE 60S NORTH OF THE I-80 CORRIDOR WITH TEMPS IN THE UPPER 60S
ACROSS THE SRN PORTIONS OF THE CWA.  WITH ENOUGH SUNSHINE...SOME 70F
MAX TEMPS ARE NOT OUT OF THE QUESTION FOR LOCATIONS SOUTH OF A
PONTIAC TO REMINGTON LINE.  THE RELATIVELY WARM AND DRY WEATHER WILL
PERSIST THROUGH THE WEEKEND AS THE UPPER RIDGE SLOWLY PROGRESSES
ACROSS THE CENTRAL CONUS.

THE NEXT SIGNIFICANT CHANCE FOR PCPN WILL NOT BE UNTIL EARLY NEXT
WEEK WHEN THE UPPER RIDGE BUILDS TO THE EAST COAST AND A STRONG
PACIFIC SHORTWAVE DROPS FROM THE PACIFIC NORTHWEST TO THE FOUR
CORNERS AREA BY MONDAY AFTERNOON.  THIS WILL SET UP STRONG SWLY FLOW
ALOFT...WITH A TRAIN OF SOUTHERN STREAM SHORTWAVE ENERGY...WHILE AN
OPEN GULF OF MEXICO EVOLVES AT THE SURFACE.  INCREASED LOW LEVEL
MOISTURE AND MID LEVEL SHORT WAVE ENERGY WILL BRING A CHANCE FOR
SHOWERS AND POSSIBLY SOME THUNDERSTORMS FOR MONDAY NIGHT AND INTO
TUESDAY.  THE UNSEASONABLY HIGH TEMPERATURES WILL COME TO AN END BY
EARLY NEXT WEEK AS ANOTHER COLD FRONT IS EXPECTED TO CROSS THE
REGION.  THE LATEST LONG RANGE GUIDANCE SUGGESTS THAT THIS FRONT
SHOULD PUSH THROUGH THE AREA BY TUESDAY NIGHT OR WEDNESDAY...
BRINGING MAX TEMPS BACK INTO THE 50S.

KREIN

&&

.AVIATION...

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

* SOUTHERLY WINDS 10-12 KTS MID MORNING THRU LATE AFTERNOON.
* CHANCE OF SHRA LATE AFTERNOON/EARLY EVENING.
* MVFR CIGS TONIGHT. CMS

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

A WEAK COLD FRONT/TROUGH WILL MOVE ACROSS THE AREA LATER THIS
AFTERNOON AND THIS EVENING...AS IT WEAKENS. LIGHT SOUTHEAST WINDS
WILL TURN MORE SOUTH/SOUTHWEST BY MID MORNING AND INCREASE INTO
THE 10-12KT RANGE WITH SOME HIGHER GUSTS POSSIBLE THRU EARLY
AFTERNOON. SHOWERS ARE EXPECTED TO SPREAD INTO NORTHWEST IL BY
EARLY AFTERNOON AND THEN ACROSS THE REST OF THE AREA BY LATE
AFTERNOON AND EARLY EVENING. NO CHANGE TO TIMING WHICH LOOKS ON
TRACK BUT OVERALL COVERAGE AND INTENSITY REMAINS SOMEWHAT LOWER
AT THE CHICAGO AREA TERMINALS AND BACKED OFF TO VICINITY MENTION
FOR NOW. CIGS SHOULD REMAIN VFR UNTIL THE SHOWERS END AND THEN
LOWER TO MVFR THIS EVENING...EARLIER AT RFD. AS CLOUDS CLEAR FROM
WEST TO EAST LATE TONIGHT/EARLY FRIDAY MORNING...SOME FOG WILL BE
POSSIBLE. CMS

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

* HIGH FOR WIND DIRECTION...MEDIUM FOR SPEEDS AND POSSIBLE GUSTS.
* MEDIUM FOR SHRA LATE AFTERNOON/EARLY EVENING.
* MEDIUM FOR MVFR CIGS TONIGHT. CMS

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 230301
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1001 PM CDT WED OCT 22 2014

.DISCUSSION...
310 PM CDT

SHORT TERM...THIS AFTERNOON THROUGH TONIGHT...FOR THE REMAINDER OF
THE AFTERNOON AND TONIGHT...MOSTLY CLEAR SKIES AND SLIGHTLY HIGHER
TEMPERATURES ARE MAKING FOR A TRANSITION DAY TODAY BEFORE A MORE
NOTABLE WARMING TREND EXPECTED FOR THE NEXT FEW DAYS. UNDER THE
CLEAR SKIES AND LIGHT WINDS...TEMPERATURES THIS AFTERNOON ARE
CLIMBING INTO THE LOW 50S NEAR LAKE MICHIGAN TO AROUND 60F WELL
INLAND.  A RIDGE OF HIGH PRESSURE MOVING ACROSS THE WESTERN GREAT
LAKES HAS SET UP LIGHT ONSHORE FLOW NEAR THE LAKE...PREVENTING THE
WARMER CONDITIONS NEAR THE LAKE.  FOR TONIGHT...UNDER CLEAR
SKIES...LIGHT WINDS AND WITH A RELATIVELY DRY AIRMASS IN
PLACE...TEMPERATURES WILL ONCE AGAIN HAVE AN OPPORTUNITY TO RADIATE
DOWN INTO THE MIDDLE TO UPPER 30S.  THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD REMAIN A BIT WARMER...WITH LOWS ONLY
IN THE LOWER 40S.  EVEN THOUGH THE AIRMASS IS EXPECTED TO BE
RELATIVELY DRY...DEWPOINTS SHOULD BE THE LOWER TO MIDDLE 30S...SO
TEMPERATURES WILL LIKELY RADIATE CLOSE TO THE DEWPOINTS.  DO NOT
ANTICIPATE WIDESPREAD DENSE FOG...BUT RATHER THERE COULD MORE LIKELY
BE SOME PATCHY...SHALLOW GROUND FOG IN LOW-LYING...SHELTERED...RURAL
LOCATIONS.

LONGER TERM...THURSDAY THROUGH WEDNESDAY...AS THE HIGH SLIDES OFF TO
THE EAST AND A SFC TROUGH AND ASSOCIATED COLD FRONT CROSS THE
CENTRAL PLAINS...A RETURN FLOW OF SLIGHTLY WARMER...MOISTER AIR WILL
SET UP.  WHILE THE NORTHERN PORTION OF THE SFC HIGH WILL PUSH WELL
EAST OF THE AREA...THE MIDWEST WILL REMAIN CUT OFF FROM THE RICHER
GULF MOISTURE AS A RIDGE AXIS EXTENDS SWWD THROUGH ERN TX.  THIS
COMBINATION WILL AFFECT BOTH MAX TEMP POTENTIAL FOR THE DAY AS WELL
AS PCPN POTENTIAL WITH THE PASSAGE OF THE COLD FRONT.  WHILE
INCREASING CLOUD COVER WILL SOMEWHAT TEMPER THE POTENTIAL MAX TEMPS
FOR THE DAY...HIGHS THURSDAY SHOULD RANGE FROM THE UPPER 50S TO
AROUND 60F.  AS FOR PCPN POTENTIAL...THERE SHOULD BE ADEQUATE SFC
FORCING WITH THE COLD FRONT AS WELL AS MID LEVEL FORCING FROM A NRN
STREAM SHORTWAVE TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY AND
WRN GREAT LAKES AS WELL AS SOME PHASING WITH A SRN STREAM SHORTWAVE
PASSING ACROSS THE MIDDLE MISSISSIPPI VALLEY.  EVEN THOUGH THE
SURFACE LAYER WILL BE SOMEWHAT CUT OFF FROM THE RICHEST LOW LEVEL
GULF MOISTURE...THE SRN STREAM SHORT WAVE WILL BRING SOME ENHANCED
MID LEVEL MOISTURE...SO THE OVERALL MOISTURE PROFILE WILL STILL BE
RELATIVELY MOIST WITH THE MODELS INDICATING PWATS OF AROUND 1 INCH
WITH THE FROPA.  SO...EXPECT THAT ENTIRE CWA SHOULD SEE WETTING
RAINFALL THROUGH THE DAY TOMORROW...POSSIBLY LINGERING INTO TOMORROW
EVENING OVER THE FAR ERN PORTIONS OF THE CWA...THE STEADILY
PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO
ARND A TENTH TO A QUARTER OF AN INCH WITH SOME OF THE HEAVIER
SHOWERS.  MODELS SOUNDINGS INDICATE LITTLE OR NO CAPE...SO THUNDER
SHOULD NOT BE AN ISSUE.

FOLLOWING THE PASSAGE OF THE FRONT...THE REAL WARMING TREND WILL
BEGIN IN EARNEST ON FRIDAY AS UPPER RIDGING BUILDS ACROSS THE
ROCKIES AND INTO THE WESTERN PLAINS...WHILE THE UPPER TROUGH AND
COLD FRONT MOVE TO THE EAST COAST.  BY FRIDAY...850MB TEMPS ARND 15C
WILL MOVE ACROSS THE AREA AND EXPECT THAT TEMPS SHOULD REACH INTO
THE MIDDLE TO UPPER 60S.  BY SATURDAY...THE THERMAL AXIS WILL SHIFT
TO THE SOUTH...ACROSS CNTRL/SRN IL/IN WHILE A DEEP UPPER LOW TRACKS
ACROSS THE UPPER GREAT LAKES.  THIS WILL LEAD TO MORE NWLY FLOW
ACROSS THE UPPER MIDWEST...AND POSSIBLY LIMITING WARMING ACROSS THE
NRN PORTIONS OF THE AREA...SO...WILL CARRY TEMPS IN THE LOWER TO
MIDDLE 60S NORTH OF THE I-80 CORRIDOR WITH TEMPS IN THE UPPER 60S
ACROSS THE SRN PORTIONS OF THE CWA.  WITH ENOUGH SUNSHINE...SOME 70F
MAX TEMPS ARE NOT OUT OF THE QUESTION FOR LOCATIONS SOUTH OF A
PONTIAC TO REMINGTON LINE.  THE RELATIVELY WARM AND DRY WEATHER WILL
PERSIST THROUGH THE WEEKEND AS THE UPPER RIDGE SLOWLY PROGRESSES
ACROSS THE CENTRAL CONUS.

THE NEXT SIGNIFICANT CHANCE FOR PCPN WILL NOT BE UNTIL EARLY NEXT
WEEK WHEN THE UPPER RIDGE BUILDS TO THE EAST COAST AND A STRONG
PACIFIC SHORTWAVE DROPS FROM THE PACIFIC NORTHWEST TO THE FOUR
CORNERS AREA BY MONDAY AFTERNOON.  THIS WILL SET UP STRONG SWLY FLOW
ALOFT...WITH A TRAIN OF SOUTHERN STREAM SHORTWAVE ENERGY...WHILE AN
OPEN GULF OF MEXICO EVOLVES AT THE SURFACE.  INCREASED LOW LEVEL
MOISTURE AND MID LEVEL SHORT WAVE ENERGY WILL BRING A CHANCE FOR
SHOWERS AND POSSIBLY SOME THUNDERSTORMS FOR MONDAY NIGHT AND INTO
TUESDAY.  THE UNSEASONABLY HIGH TEMPERATURES WILL COME TO AN END BY
EARLY NEXT WEEK AS ANOTHER COLD FRONT IS EXPECTED TO CROSS THE
REGION.  THE LATEST LONG RANGE GUIDANCE SUGGESTS THAT THIS FRONT
SHOULD PUSH THROUGH THE AREA BY TUESDAY NIGHT OR WEDNESDAY...
BRINGING MAX TEMPS BACK INTO THE 50S.

KREIN

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 030Z...

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL
  WITH AND AFTER -SHRA PASSES

KMD

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

QUIET CONDITIONS EXPECTED OVERNIGHT WITH LIGHT WINDS IN SLOWLY
INCREASING HIGH CLOUDS. WINDS INCREASE DURING THE DAY AHEAD OF
SLOW MOVING FRONTAL SYSTEM. SW WINDS INCREASE TO AROUND 10 KT
THROUGH THE DAY. THERE MAY BE  HIGHER SW WINDS AHEAD OF THE FRONT
IN THE 18Z-22Z TIME FRAME THAN THE CURRENT TAFS INDICATE...BUT THE
GRADIENT WILL BE WEAKENING DURING THIS TIME AHEAD OF RAIN/SHOWER
ACTIVITY. EXPECT A PERIOD OF MVFR AT SOME POINT WITH THE LIGHT
SHOWERS...WITH A BETTER CHANCE TOWARD THE TAIL END OF THE MAIN
RAINFALL ACTIVITY DURING THE EVENING HOURS. THERE MAY EVEN BE SOME
LINGERING DRIZZLE BEHIND THE SHOWERS AS LOW LEVEL SATURATION
INCREASES WHICH COULD LOWER CIGS/VSBYS AS WELL.

KMD

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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY/THURSDAY NIGHT.

KMD

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 222357
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
657 PM CDT WED OCT 22 2014

.DISCUSSION...
310 PM CDT

SHORT TERM...THIS AFTERNOON THROUGH TONIGHT...FOR THE REMAINDER OF
THE AFTERNOON AND TONIGHT...MOSTLY CLEAR SKIES AND SLIGHTLY HIGHER
TEMPERATURES ARE MAKING FOR A TRANSITION DAY TODAY BEFORE A MORE
NOTABLE WARMING TREND EXPECTED FOR THE NEXT FEW DAYS. UNDER THE
CLEAR SKIES AND LIGHT WINDS...TEMPERATURES THIS AFTERNOON ARE
CLIMBING INTO THE LOW 50S NEAR LAKE MICHIGAN TO AROUND 60F WELL
INLAND.  A RIDGE OF HIGH PRESSURE MOVING ACROSS THE WESTERN GREAT
LAKES HAS SET UP LIGHT ONSHORE FLOW NEAR THE LAKE...PREVENTING THE
WARMER CONDITIONS NEAR THE LAKE.  FOR TONIGHT...UNDER CLEAR
SKIES...LIGHT WINDS AND WITH A RELATIVELY DRY AIRMASS IN
PLACE...TEMPERATURES WILL ONCE AGAIN HAVE AN OPPORTUNITY TO RADIATE
DOWN INTO THE MIDDLE TO UPPER 30S.  THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD REMAIN A BIT WARMER...WITH LOWS ONLY
IN THE LOWER 40S.  EVEN THOUGH THE AIRMASS IS EXPECTED TO BE
RELATIVELY DRY...DEWPOINTS SHOULD BE THE LOWER TO MIDDLE 30S...SO
TEMPERATURES WILL LIKELY RADIATE CLOSE TO THE DEWPOINTS.  DO NOT
ANTICIPATE WIDESPREAD DENSE FOG...BUT RATHER THERE COULD MORE LIKELY
BE SOME PATCHY...SHALLOW GROUND FOG IN LOW-LYING...SHELTERED...RURAL
LOCATIONS.

LONGER TERM...THURSDAY THROUGH WEDNESDAY...AS THE HIGH SLIDES OFF TO
THE EAST AND A SFC TROUGH AND ASSOCIATED COLD FRONT CROSS THE
CENTRAL PLAINS...A RETURN FLOW OF SLIGHTLY WARMER...MOISTER AIR WILL
SET UP.  WHILE THE NORTHERN PORTION OF THE SFC HIGH WILL PUSH WELL
EAST OF THE AREA...THE MIDWEST WILL REMAIN CUT OFF FROM THE RICHER
GULF MOISTURE AS A RIDGE AXIS EXTENDS SWWD THROUGH ERN TX.  THIS
COMBINATION WILL AFFECT BOTH MAX TEMP POTENTIAL FOR THE DAY AS WELL
AS PCPN POTENTIAL WITH THE PASSAGE OF THE COLD FRONT.  WHILE
INCREASING CLOUD COVER WILL SOMEWHAT TEMPER THE POTENTIAL MAX TEMPS
FOR THE DAY...HIGHS THURSDAY SHOULD RANGE FROM THE UPPER 50S TO
AROUND 60F.  AS FOR PCPN POTENTIAL...THERE SHOULD BE ADEQUATE SFC
FORCING WITH THE COLD FRONT AS WELL AS MID LEVEL FORCING FROM A NRN
STREAM SHORTWAVE TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY AND
WRN GREAT LAKES AS WELL AS SOME PHASING WITH A SRN STREAM SHORTWAVE
PASSING ACROSS THE MIDDLE MISSISSIPPI VALLEY.  EVEN THOUGH THE
SURFACE LAYER WILL BE SOMEWHAT CUT OFF FROM THE RICHEST LOW LEVEL
GULF MOISTURE...THE SRN STREAM SHORT WAVE WILL BRING SOME ENHANCED
MID LEVEL MOISTURE...SO THE OVERALL MOISTURE PROFILE WILL STILL BE
RELATIVELY MOIST WITH THE MODELS INDICATING PWATS OF AROUND 1 INCH
WITH THE FROPA.  SO...EXPECT THAT ENTIRE CWA SHOULD SEE WETTING
RAINFALL THROUGH THE DAY TOMORROW...POSSIBLY LINGERING INTO TOMORROW
EVENING OVER THE FAR ERN PORTIONS OF THE CWA...THE STEADILY
PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO
ARND A TENTH TO A QUARTER OF AN INCH WITH SOME OF THE HEAVIER
SHOWERS.  MODELS SOUNDINGS INDICATE LITTLE OR NO CAPE...SO THUNDER
SHOULD NOT BE AN ISSUE.

FOLLOWING THE PASSAGE OF THE FRONT...THE REAL WARMING TREND WILL
BEGIN IN EARNEST ON FRIDAY AS UPPER RIDGING BUILDS ACROSS THE
ROCKIES AND INTO THE WESTERN PLAINS...WHILE THE UPPER TROUGH AND
COLD FRONT MOVE TO THE EAST COAST.  BY FRIDAY...850MB TEMPS ARND 15C
WILL MOVE ACROSS THE AREA AND EXPECT THAT TEMPS SHOULD REACH INTO
THE MIDDLE TO UPPER 60S.  BY SATURDAY...THE THERMAL AXIS WILL SHIFT
TO THE SOUTH...ACROSS CNTRL/SRN IL/IN WHILE A DEEP UPPER LOW TRACKS
ACROSS THE UPPER GREAT LAKES.  THIS WILL LEAD TO MORE NWLY FLOW
ACROSS THE UPPER MIDWEST...AND POSSIBLY LIMITING WARMING ACROSS THE
NRN PORTIONS OF THE AREA...SO...WILL CARRY TEMPS IN THE LOWER TO
MIDDLE 60S NORTH OF THE I-80 CORRIDOR WITH TEMPS IN THE UPPER 60S
ACROSS THE SRN PORTIONS OF THE CWA.  WITH ENOUGH SUNSHINE...SOME 70F
MAX TEMPS ARE NOT OUT OF THE QUESTION FOR LOCATIONS SOUTH OF A
PONTIAC TO REMINGTON LINE.  THE RELATIVELY WARM AND DRY WEATHER WILL
PERSIST THROUGH THE WEEKEND AS THE UPPER RIDGE SLOWLY PROGRESSES
ACROSS THE CENTRAL CONUS.

THE NEXT SIGNIFICANT CHANCE FOR PCPN WILL NOT BE UNTIL EARLY NEXT
WEEK WHEN THE UPPER RIDGE BUILDS TO THE EAST COAST AND A STRONG
PACIFIC SHORTWAVE DROPS FROM THE PACIFIC NORTHWEST TO THE FOUR
CORNERS AREA BY MONDAY AFTERNOON.  THIS WILL SET UP STRONG SWLY FLOW
ALOFT...WITH A TRAIN OF SOUTHERN STREAM SHORTWAVE ENERGY...WHILE AN
OPEN GULF OF MEXICO EVOLVES AT THE SURFACE.  INCREASED LOW LEVEL
MOISTURE AND MID LEVEL SHORT WAVE ENERGY WILL BRING A CHANCE FOR
SHOWERS AND POSSIBLY SOME THUNDERSTORMS FOR MONDAY NIGHT AND INTO
TUESDAY.  THE UNSEASONABLY HIGH TEMPERATURES WILL COME TO AN END BY
EARLY NEXT WEEK AS ANOTHER COLD FRONT IS EXPECTED TO CROSS THE
REGION.  THE LATEST LONG RANGE GUIDANCE SUGGESTS THAT THIS FRONT
SHOULD PUSH THROUGH THE AREA BY TUESDAY NIGHT OR WEDNESDAY...
BRINGING MAX TEMPS BACK INTO THE 50S.

KREIN

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL
  WITH AND AFTER -SHRA PASSES

KMD

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

QUIET CONDITIONS EXPECTED OVERNIGHT WITH LIGHT WINDS IN SLOWLY
INCREASING HIGH CLOUDS. WINDS INCREASE DURING THE DAY AHEAD OF
SLOW MOVING FRONTAL SYSTEM. SW WINDS INCREASE TO AROUND 10 KT
THROUGH THE DAY. THERE MAY BE  HIGHER SW WINDS AHEAD OF THE FRONT
IN THE 18Z-22Z TIME FRAME THAN THE CURRENT TAFS INDICATE...BUT THE
GRADIENT WILL BE WEAKENING DURING THIS TIME AHEAD OF RAIN/SHOWER
ACTIVITY. EXPECT A PERIOD OF MVFR AT SOME POINT WITH THE LIGHT
SHOWERS...WITH A BETTER CHANCE TOWARD THE TAIL END OF THE MAIN
RAINFALL ACTIVITY DURING THE EVENING HOURS. THERE MAY EVEN BE SOME
LINGERING DRIZZLE BEHIND THE SHOWERS AS LOW LEVEL SATURATION
INCREASES WHICH COULD LOWER CIGS/VSBYS AS WELL.

KMD


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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY/THURSDAY NIGHT.

KMD

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 222357
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
657 PM CDT WED OCT 22 2014

.DISCUSSION...
310 PM CDT

SHORT TERM...THIS AFTERNOON THROUGH TONIGHT...FOR THE REMAINDER OF
THE AFTERNOON AND TONIGHT...MOSTLY CLEAR SKIES AND SLIGHTLY HIGHER
TEMPERATURES ARE MAKING FOR A TRANSITION DAY TODAY BEFORE A MORE
NOTABLE WARMING TREND EXPECTED FOR THE NEXT FEW DAYS. UNDER THE
CLEAR SKIES AND LIGHT WINDS...TEMPERATURES THIS AFTERNOON ARE
CLIMBING INTO THE LOW 50S NEAR LAKE MICHIGAN TO AROUND 60F WELL
INLAND.  A RIDGE OF HIGH PRESSURE MOVING ACROSS THE WESTERN GREAT
LAKES HAS SET UP LIGHT ONSHORE FLOW NEAR THE LAKE...PREVENTING THE
WARMER CONDITIONS NEAR THE LAKE.  FOR TONIGHT...UNDER CLEAR
SKIES...LIGHT WINDS AND WITH A RELATIVELY DRY AIRMASS IN
PLACE...TEMPERATURES WILL ONCE AGAIN HAVE AN OPPORTUNITY TO RADIATE
DOWN INTO THE MIDDLE TO UPPER 30S.  THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD REMAIN A BIT WARMER...WITH LOWS ONLY
IN THE LOWER 40S.  EVEN THOUGH THE AIRMASS IS EXPECTED TO BE
RELATIVELY DRY...DEWPOINTS SHOULD BE THE LOWER TO MIDDLE 30S...SO
TEMPERATURES WILL LIKELY RADIATE CLOSE TO THE DEWPOINTS.  DO NOT
ANTICIPATE WIDESPREAD DENSE FOG...BUT RATHER THERE COULD MORE LIKELY
BE SOME PATCHY...SHALLOW GROUND FOG IN LOW-LYING...SHELTERED...RURAL
LOCATIONS.

LONGER TERM...THURSDAY THROUGH WEDNESDAY...AS THE HIGH SLIDES OFF TO
THE EAST AND A SFC TROUGH AND ASSOCIATED COLD FRONT CROSS THE
CENTRAL PLAINS...A RETURN FLOW OF SLIGHTLY WARMER...MOISTER AIR WILL
SET UP.  WHILE THE NORTHERN PORTION OF THE SFC HIGH WILL PUSH WELL
EAST OF THE AREA...THE MIDWEST WILL REMAIN CUT OFF FROM THE RICHER
GULF MOISTURE AS A RIDGE AXIS EXTENDS SWWD THROUGH ERN TX.  THIS
COMBINATION WILL AFFECT BOTH MAX TEMP POTENTIAL FOR THE DAY AS WELL
AS PCPN POTENTIAL WITH THE PASSAGE OF THE COLD FRONT.  WHILE
INCREASING CLOUD COVER WILL SOMEWHAT TEMPER THE POTENTIAL MAX TEMPS
FOR THE DAY...HIGHS THURSDAY SHOULD RANGE FROM THE UPPER 50S TO
AROUND 60F.  AS FOR PCPN POTENTIAL...THERE SHOULD BE ADEQUATE SFC
FORCING WITH THE COLD FRONT AS WELL AS MID LEVEL FORCING FROM A NRN
STREAM SHORTWAVE TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY AND
WRN GREAT LAKES AS WELL AS SOME PHASING WITH A SRN STREAM SHORTWAVE
PASSING ACROSS THE MIDDLE MISSISSIPPI VALLEY.  EVEN THOUGH THE
SURFACE LAYER WILL BE SOMEWHAT CUT OFF FROM THE RICHEST LOW LEVEL
GULF MOISTURE...THE SRN STREAM SHORT WAVE WILL BRING SOME ENHANCED
MID LEVEL MOISTURE...SO THE OVERALL MOISTURE PROFILE WILL STILL BE
RELATIVELY MOIST WITH THE MODELS INDICATING PWATS OF AROUND 1 INCH
WITH THE FROPA.  SO...EXPECT THAT ENTIRE CWA SHOULD SEE WETTING
RAINFALL THROUGH THE DAY TOMORROW...POSSIBLY LINGERING INTO TOMORROW
EVENING OVER THE FAR ERN PORTIONS OF THE CWA...THE STEADILY
PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO
ARND A TENTH TO A QUARTER OF AN INCH WITH SOME OF THE HEAVIER
SHOWERS.  MODELS SOUNDINGS INDICATE LITTLE OR NO CAPE...SO THUNDER
SHOULD NOT BE AN ISSUE.

FOLLOWING THE PASSAGE OF THE FRONT...THE REAL WARMING TREND WILL
BEGIN IN EARNEST ON FRIDAY AS UPPER RIDGING BUILDS ACROSS THE
ROCKIES AND INTO THE WESTERN PLAINS...WHILE THE UPPER TROUGH AND
COLD FRONT MOVE TO THE EAST COAST.  BY FRIDAY...850MB TEMPS ARND 15C
WILL MOVE ACROSS THE AREA AND EXPECT THAT TEMPS SHOULD REACH INTO
THE MIDDLE TO UPPER 60S.  BY SATURDAY...THE THERMAL AXIS WILL SHIFT
TO THE SOUTH...ACROSS CNTRL/SRN IL/IN WHILE A DEEP UPPER LOW TRACKS
ACROSS THE UPPER GREAT LAKES.  THIS WILL LEAD TO MORE NWLY FLOW
ACROSS THE UPPER MIDWEST...AND POSSIBLY LIMITING WARMING ACROSS THE
NRN PORTIONS OF THE AREA...SO...WILL CARRY TEMPS IN THE LOWER TO
MIDDLE 60S NORTH OF THE I-80 CORRIDOR WITH TEMPS IN THE UPPER 60S
ACROSS THE SRN PORTIONS OF THE CWA.  WITH ENOUGH SUNSHINE...SOME 70F
MAX TEMPS ARE NOT OUT OF THE QUESTION FOR LOCATIONS SOUTH OF A
PONTIAC TO REMINGTON LINE.  THE RELATIVELY WARM AND DRY WEATHER WILL
PERSIST THROUGH THE WEEKEND AS THE UPPER RIDGE SLOWLY PROGRESSES
ACROSS THE CENTRAL CONUS.

THE NEXT SIGNIFICANT CHANCE FOR PCPN WILL NOT BE UNTIL EARLY NEXT
WEEK WHEN THE UPPER RIDGE BUILDS TO THE EAST COAST AND A STRONG
PACIFIC SHORTWAVE DROPS FROM THE PACIFIC NORTHWEST TO THE FOUR
CORNERS AREA BY MONDAY AFTERNOON.  THIS WILL SET UP STRONG SWLY FLOW
ALOFT...WITH A TRAIN OF SOUTHERN STREAM SHORTWAVE ENERGY...WHILE AN
OPEN GULF OF MEXICO EVOLVES AT THE SURFACE.  INCREASED LOW LEVEL
MOISTURE AND MID LEVEL SHORT WAVE ENERGY WILL BRING A CHANCE FOR
SHOWERS AND POSSIBLY SOME THUNDERSTORMS FOR MONDAY NIGHT AND INTO
TUESDAY.  THE UNSEASONABLY HIGH TEMPERATURES WILL COME TO AN END BY
EARLY NEXT WEEK AS ANOTHER COLD FRONT IS EXPECTED TO CROSS THE
REGION.  THE LATEST LONG RANGE GUIDANCE SUGGESTS THAT THIS FRONT
SHOULD PUSH THROUGH THE AREA BY TUESDAY NIGHT OR WEDNESDAY...
BRINGING MAX TEMPS BACK INTO THE 50S.

KREIN

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL
  WITH AND AFTER -SHRA PASSES

KMD

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

QUIET CONDITIONS EXPECTED OVERNIGHT WITH LIGHT WINDS IN SLOWLY
INCREASING HIGH CLOUDS. WINDS INCREASE DURING THE DAY AHEAD OF
SLOW MOVING FRONTAL SYSTEM. SW WINDS INCREASE TO AROUND 10 KT
THROUGH THE DAY. THERE MAY BE  HIGHER SW WINDS AHEAD OF THE FRONT
IN THE 18Z-22Z TIME FRAME THAN THE CURRENT TAFS INDICATE...BUT THE
GRADIENT WILL BE WEAKENING DURING THIS TIME AHEAD OF RAIN/SHOWER
ACTIVITY. EXPECT A PERIOD OF MVFR AT SOME POINT WITH THE LIGHT
SHOWERS...WITH A BETTER CHANCE TOWARD THE TAIL END OF THE MAIN
RAINFALL ACTIVITY DURING THE EVENING HOURS. THERE MAY EVEN BE SOME
LINGERING DRIZZLE BEHIND THE SHOWERS AS LOW LEVEL SATURATION
INCREASES WHICH COULD LOWER CIGS/VSBYS AS WELL.

KMD


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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY/THURSDAY NIGHT.

KMD

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

* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

KMD

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 222010
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 PM CDT WED OCT 22 2014

.DISCUSSION...
310 PM CDT

SHORT TERM...THIS AFTERNOON THROUGH TONIGHT...FOR THE REMAINDER OF
THE AFTERNOON AND TONIGHT...MOSTLY CLEAR SKIES AND SLIGHTLY HIGHER
TEMPERATURES ARE MAKING FOR A TRANSITION DAY TODAY BEFORE A MORE
NOTABLE WARMING TREND EXPECTED FOR THE NEXT FEW DAYS. UNDER THE
CLEAR SKIES AND LIGHT WINDS...TEMPERATURES THIS AFTERNOON ARE
CLIMBING INTO THE LOW 50S NEAR LAKE MICHIGAN TO AROUND 60F WELL
INLAND.  A RIDGE OF HIGH PRESSURE MOVING ACROSS THE WESTERN GREAT
LAKES HAS SET UP LIGHT ONSHORE FLOW NEAR THE LAKE...PREVENTING THE
WARMER CONDITIONS NEAR THE LAKE.  FOR TONIGHT...UNDER CLEAR
SKIES...LIGHT WINDS AND WITH A RELATIVELY DRY AIRMASS IN
PLACE...TEMPERATURES WILL ONCE AGAIN HAVE AN OPPORTUNITY TO RADIATE
DOWN INTO THE MIDDLE TO UPPER 30S.  THE HIGHLY URBANIZED AREAS OF
THE CHICAGO METRO AREA SHOULD REMAIN A BIT WARMER...WITH LOWS ONLY
IN THE LOWER 40S.  EVEN THOUGH THE AIRMASS IS EXPECTED TO BE
RELATIVELY DRY...DEWPOINTS SHOULD BE THE LOWER TO MIDDLE 30S...SO
TEMPERATURES WILL LIKELY RADIATE CLOSE TO THE DEWPOINTS.  DO NOT
ANTICIPATE WIDESPREAD DENSE FOG...BUT RATHER THERE COULD MORE LIKELY
BE SOME PATCHY...SHALLOW GROUND FOG IN LOW-LYING...SHELTERED...RURAL
LOCATIONS.

LONGER TERM...THURSDAY THROUGH WEDNESDAY...AS THE HIGH SLIDES OFF TO
THE EAST AND A SFC TROUGH AND ASSOCIATED COLD FRONT CROSS THE
CENTRAL PLAINS...A RETURN FLOW OF SLIGHTLY WARMER...MOISTER AIR WILL
SET UP.  WHILE THE NORTHERN PORTION OF THE SFC HIGH WILL PUSH WELL
EAST OF THE AREA...THE MIDWEST WILL REMAIN CUT OFF FROM THE RICHER
GULF MOISTURE AS A RIDGE AXIS EXTENDS SWWD THROUGH ERN TX.  THIS
COMBINATION WILL AFFECT BOTH MAX TEMP POTENTIAL FOR THE DAY AS WELL
AS PCPN POTENTIAL WITH THE PASSAGE OF THE COLD FRONT.  WHILE
INCREASING CLOUD COVER WILL SOMEWHAT TEMPER THE POTENTIAL MAX TEMPS
FOR THE DAY...HIGHS THURSDAY SHOULD RANGE FROM THE UPPER 50S TO
AROUND 60F.  AS FOR PCPN POTENTIAL...THERE SHOULD BE ADEQUATE SFC
FORCING WITH THE COLD FRONT AS WELL AS MID LEVEL FORCING FROM A NRN
STREAM SHORTWAVE TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY AND
WRN GREAT LAKES AS WELL AS SOME PHASING WITH A SRN STREAM SHORTWAVE
PASSING ACROSS THE MIDDLE MISSISSIPPI VALLEY.  EVEN THOUGH THE
SURFACE LAYER WILL BE SOMEWHAT CUT OFF FROM THE RICHEST LOW LEVEL
GULF MOISTURE...THE SRN STREAM SHORT WAVE WILL BRING SOME ENHANCED
MID LEVEL MOISTURE...SO THE OVERALL MOISTURE PROFILE WILL STILL BE
RELATIVELY MOIST WITH THE MODELS INDICATING PWATS OF AROUND 1 INCH
WITH THE FROPA.  SO...EXPECT THAT ENTIRE CWA SHOULD SEE WETTING
RAINFALL THROUGH THE DAY TOMORROW...POSSIBLY LINGERING INTO TOMORROW
EVENING OVER THE FAR ERN PORTIONS OF THE CWA...THE STEADILY
PROGRESSIVE NATURE OF THE SYSTEM SHOULD LIMIT RAINFALL AMOUNTS TO
ARND A TENTH TO A QUARTER OF AN INCH WITH SOME OF THE HEAVIER
SHOWERS.  MODELS SOUNDINGS INDICATE LITTLE OR NO CAPE...SO THUNDER
SHOULD NOT BE AN ISSUE.

FOLLOWING THE PASSAGE OF THE FRONT...THE REAL WARMING TREND WILL
BEGIN IN EARNEST ON FRIDAY AS UPPER RIDGING BUILDS ACROSS THE
ROCKIES AND INTO THE WESTERN PLAINS...WHILE THE UPPER TROUGH AND
COLD FRONT MOVE TO THE EAST COAST.  BY FRIDAY...850MB TEMPS ARND 15C
WILL MOVE ACROSS THE AREA AND EXPECT THAT TEMPS SHOULD REACH INTO
THE MIDDLE TO UPPER 60S.  BY SATURDAY...THE THERMAL AXIS WILL SHIFT
TO THE SOUTH...ACROSS CNTRL/SRN IL/IN WHILE A DEEP UPPER LOW TRACKS
ACROSS THE UPPER GREAT LAKES.  THIS WILL LEAD TO MORE NWLY FLOW
ACROSS THE UPPER MIDWEST...AND POSSIBLY LIMITING WARMING ACROSS THE
NRN PORTIONS OF THE AREA...SO...WILL CARRY TEMPS IN THE LOWER TO
MIDDLE 60S NORTH OF THE I-80 CORRIDOR WITH TEMPS IN THE UPPER 60S
ACROSS THE SRN PORTIONS OF THE CWA.  WITH ENOUGH SUNSHINE...SOME 70F
MAX TEMPS ARE NOT OUT OF THE QUESTION FOR LOCATIONS SOUTH OF A
PONTIAC TO REMINGTON LINE.  THE RELATIVELY WARM AND DRY WEATHER WILL
PERSIST THROUGH THE WEEKEND AS THE UPPER RIDGE SLOWLY PROGRESSES
ACROSS THE CENTRAL CONUS.

THE NEXT SIGNIFICANT CHANCE FOR PCPN WILL NOT BE UNTIL EARLY NEXT
WEEK WHEN THE UPPER RIDGE BUILDS TO THE EAST COAST AND A STRONG
PACIFIC SHORTWAVE DROPS FROM THE PACIFIC NORTHWEST TO THE FOUR
CORNERS AREA BY MONDAY AFTERNOON.  THIS WILL SET UP STRONG SWLY FLOW
ALOFT...WITH A TRAIN OF SOUTHERN STREAM SHORTWAVE ENERGY...WHILE AN
OPEN GULF OF MEXICO EVOLVES AT THE SURFACE.  INCREASED LOW LEVEL
MOISTURE AND MID LEVEL SHORT WAVE ENERGY WILL BRING A CHANCE FOR
SHOWERS AND POSSIBLY SOME THUNDERSTORMS FOR MONDAY NIGHT AND INTO
TUESDAY.  THE UNSEASONABLY HIGH TEMPERATURES WILL COME TO AN END BY
EARLY NEXT WEEK AS ANOTHER COLD FRONT IS EXPECTED TO CROSS THE
REGION.  THE LATEST LONG RANGE GUIDANCE SUGGESTS THAT THIS FRONT
SHOULD PUSH THROUGH THE AREA BY TUESDAY NIGHT OR WEDNESDAY...
BRINGING MAX TEMPS BACK INTO THE 50S.

KREIN

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL.

JEE

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

QUIET HIGH PRESSURE IS OVERHEAD LEADING TO CONTINUED VFR
CONDITIONS OVERNIGHT. THE HIGH SHIFTS EAST TOMORROW AS A WEAK
SURFACE LOW OVER MANITOBA APPROACHES. THE MAIN LOW WILL REMAIN
OVER SOUTHERN CANADA AND WEAKEN AS IT MOVES INTO WESTERN ONTARIO.
AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOWS WARM FRONT
PASSES OVERHEAD TOMORROW AFTERNOON AND THIS WILL BE THE TRIGGER
FOR PRECIP. THE DISTURBANCE AND FRONT WILL BE WEAKENING AS THEY
MOVE OVERHEAD SO HAVE LIMITED CONFIDENCE IN HOW LONG THE BAND OF
PRECIP WILL HOLD TOGETHER. MODELS ARE ALSO SLOWING THE SYSTEM SO
THE ONSET OF PRECIP MAY BE LATER THAN CURRENTLY INDICATED.

AS SUCH ONLY HAVE PRECIP MENTIONED AT ORD. COULD SEE PRECIP
REACHING RFD ARND 18Z...BUT GIVEN THE SLOWING TREND...OPTED TO
KEEP -SHRA OUT OF THE RFD TAF FOR NOW.

GUIDANCE DIFFERS ON CIGS WITH THE PRECIP AS WELL...WITH ONE MODEL
INDICATING MFVR OR LOWER CIGS. GIVEN THE DIFFERENCES AND WEAKENING
TREND...WENT WITH LOW END VFR CIGS WITH A SCT LATER OF MVFR.

LASTLY...WINDS TURN SSW TOMORROW MORNING AND WILL BE ARND 10 KT.

JEE

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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 221955
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
255 PM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL.

JEE

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

QUIET HIGH PRESSURE IS OVERHEAD LEADING TO CONTINUED VFR
CONDITIONS OVERNIGHT. THE HIGH SHIFTS EAST TOMORROW AS A WEAK
SURFACE LOW OVER MANITOBA APPROACHES. THE MAIN LOW WILL REMAIN
OVER SOUTHERN CANADA AND WEAKEN AS IT MOVES INTO WESTERN ONTARIO.
AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOWS WARM FRONT
PASSES OVERHEAD TOMORROW AFTERNOON AND THIS WILL BE THE TRIGGER
FOR PRECIP. THE DISTURBANCE AND FRONT WILL BE WEAKENING AS THEY
MOVE OVERHEAD SO HAVE LIMITED CONFIDENCE IN HOW LONG THE BAND OF
PRECIP WILL HOLD TOGETHER. MODELS ARE ALSO SLOWING THE SYSTEM SO
THE ONSET OF PRECIP MAY BE LATER THAN CURRENTLY INDICATED.

AS SUCH ONLY HAVE PRECIP MENTIONED AT ORD. COULD SEE PRECIP
REACHING RFD ARND 18Z...BUT GIVEN THE SLOWING TREND...OPTED TO
KEEP -SHRA OUT OF THE RFD TAF FOR NOW.

GUIDANCE DIFFERS ON CIGS WITH THE PRECIP AS WELL...WITH ONE MODEL
INDICATING MFVR OR LOWER CIGS. GIVEN THE DIFFERENCES AND WEAKENING
TREND...WENT WITH LOW END VFR CIGS WITH A SCT LATER OF MVFR.

LASTLY...WINDS TURN SSW TOMORROW MORNING AND WILL BE ARND 10 KT.

JEE

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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 221859
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
159 PM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL.

JEE

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

QUIET HIGH PRESSURE IS OVERHEAD LEADING TO CONTINUED VFR
CONDITIONS OVERNIGHT. THE HIGH SHIFTS EAST TOMORROW AS A WEAK
SURFACE LOW OVER MANITOBA APPROACHES. THE MAIN LOW WILL REMAIN
OVER SOUTHERN CANADA AND WEAKEN AS IT MOVES INTO WESTERN ONTARIO.
AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOWS WARM FRONT
PASSES OVERHEAD TOMORROW AFTERNOON AND THIS WILL BE THE TRIGGER
FOR PRECIP. THE DISTURBANCE AND FRONT WILL BE WEAKENING AS THEY
MOVE OVERHEAD SO HAVE LIMITED CONFIDENCE IN HOW LONG THE BAND OF
PRECIP WILL HOLD TOGETHER. MODELS ARE ALSO SLOWING THE SYSTEM SO
THE ONSET OF PRECIP MAY BE LATER THAN CURRENTLY INDICATED.

AS SUCH ONLY HAVE PRECIP MENTIONED AT ORD. COULD SEE PRECIP
REACHING RFD ARND 18Z...BUT GIVEN THE SLOWING TREND...OPTED TO
KEEP -SHRA OUT OF THE RFD TAF FOR NOW.

GUIDANCE DIFFERS ON CIGS WITH THE PRECIP AS WELL...WITH ONE MODEL
INDICATING MFVR OR LOWER CIGS. GIVEN THE DIFFERENCES AND WEAKENING
TREND...WENT WITH LOW END VFR CIGS WITH A SCT LATER OF MVFR.

LASTLY...WINDS TURN SSW TOMORROW MORNING AND WILL BE ARND 10 KT.

JEE

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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...
158 PM CDT

THE WEATHER PATTERN ACROSS THE WESTERN GREAT LAKES REGION WILL
REMAIN FAIRLY PROGRESSIVE THROUGH THE WEEKEND AND INTO EARLY NEXT
WEEK...WITH SEVERAL FRONTAL PASSAGES ALTERNATING WITH WEAK HIGH
PRESSURE RIDGES.

HIGH PRESSURE WAS SITUATED OVER THE WESTERN LAKES THIS AFTERNOON...
BUT THE RIDGE WILL MOVE SLOWLY EAST TONIGHT WITH SOUTH WINDS
BECOMING STRONGER THURSDAY AS A TROUGH OF LOW PRESSURE MOVES INTO
THE UPPER MIDWEST. PRESSURE FALLS AHEAD OF THIS SYSTEM WILL LIKELY
LEAD TO SOUTH WINDS GUSTING TO 20-25 KT ESPECIALLY ACROSS THE
NORTHERN PART LAKE MICHIGAN THURSDAY AFTERNOON AND EVENING. THE COLD
FRONT ASSOCIATED WITH THIS TROUGH WILL WEAKEN AS IT MOVES THROUGH
THE REGION EARLY FRIDAY...WITH WINDS BACKING SOUTH AGAIN AHEAD OF
ANOTHER DISTURBANCE EMERGING FROM THE NORTHERN PLAINS. THIS NEXT
TROUGH AND COLD FRONT WILL PASS LATE FRIDAY NIGHT...WITH WINDS
VEERING TO THE WEST AND AGAIN GUSTING AS HIGH AS 30 KT INTO SATURDAY
AND SATURDAY NIGHT. A FEW GUSTS NEAR GALE FORCE MAY BE POSSIBLE
SATURDAY NIGHT AS COLDER AIR STEEPENS THE LOW LEVEL LAPSE RATES OVER
THE LAKE AND ALLOWS DEEPER MIXING OF THE HIGHER MOMENTUM AIR FROM
ABOVE. WINDS WILL THEN EASE SUNDAY AS ANOTHER WEAK HIGH PRESSURE
RIDGE MOVES ACROSS THE LAKE LATE IN THE DAY.

A DEEPER LOW PRESSURE SYSTEM IS FORECAST TO DEVELOP OVER THE PLAINS
AND LIFT NORTHEAST ACROSS THE UPPER MIDWEST SUNDAY NIGHT THROUGH
TUESDAY. SURFACE PRESSURE FALLS AND A RESULTING TIGHTENING OF THE
SURFACE PRESSURE GRADIENT WILL RESULT IN WINDS BACK TO THE
SOUTH-SOUTHEAST BY EARLY MONDAY...WITH SPEEDS INCREASING INTO THE
20-30 KT RANGE AGAIN.

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/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO







000
FXUS63 KLOT 221742
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1242 PM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL.

JEE

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

QUIET HIGH PRESSURE IS OVERHEAD LEADING TO CONTINUED VFR
CONDITIONS OVERNIGHT. THE HIGH SHIFTS EAST TOMORROW AS A WEAK
SURFACE LOW OVER MANITOBA APPROACHES. THE MAIN LOW WILL REMAIN
OVER SOUTHERN CANADA AND WEAKEN AS IT MOVES INTO WESTERN ONTARIO.
AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOWS WARM FRONT
PASSES OVERHEAD TOMORROW AFTERNOON AND THIS WILL BE THE TRIGGER
FOR PRECIP. THE DISTURBANCE AND FRONT WILL BE WEAKENING AS THEY
MOVE OVERHEAD SO HAVE LIMITED CONFIDENCE IN HOW LONG THE BAND OF
PRECIP WILL HOLD TOGETHER. MODELS ARE ALSO SLOWING THE SYSTEM SO
THE ONSET OF PRECIP MAY BE LATER THAN CURRENTLY INDICATED.

AS SUCH ONLY HAVE PRECIP MENTIONED AT ORD. COULD SEE PRECIP
REACHING RFD ARND 18Z...BUT GIVEN THE SLOWING TREND...OPTED TO
KEEP -SHRA OUT OF THE RFD TAF FOR NOW.

GUIDANCE DIFFERS ON CIGS WITH THE PRECIP AS WELL...WITH ONE MODEL
INDICATING MFVR OR LOWER CIGS. GIVEN THE DIFFERENCES AND WEAKENING
TREND...WENT WITH LOW END VFR CIGS WITH A SCT LATER OF MVFR.

LASTLY...WINDS TURN SSW TOMORROW MORNING AND WILL BE ARND 10 KT.

JEE


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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...

324 AM...A LARGE RIDGE OF HIGH PRESSURE EXTENDS FROM QUEBEC INTO
THE WESTERN LAKES. THIS RIDGE WILL MOVE EAST TODAY AND TONIGHT AND
SLOWLY WEAKEN. EASTERLY WINDS WILL CONTINUE TO DIMINISH THIS
MORNING BUT WAVE ACTION...ESPECIALLY ACROSS THE SOUTHWESTERN PART
OF THE LAKE WILL SLOWLY SUBSIDE THIS MORNING. WINDS WILL TURN BACK
SOUTHERLY TONIGHT AND INCREASE ON THURSDAY AS THE GRADIENT
TIGHTENS AHEAD OF AN APPROACHING COLD FRONT WHICH WILL THEN MOVE
ACROSS THE LAKE THURSDAY NIGHT AS IT DISSIPATES. THE FLOW WILL
TURN BACK SOUTHWESTERLY FRIDAY AHEAD OF ANOTHER COLD FRONT WHICH
WILL MOVE ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY MORNING.
WINDS BEHIND THIS FRONT WILL INCREASE TO 15-25 KTS WITH HIGHER
WINDS POSSIBLE OVER THE NORTHERN PART OF THE LAKE. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 221742
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1242 PM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* -SHRA EXPECTED LATE THURSDAY AFTERNOON AND MVFR CIGS ARE PSBL.

JEE

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

QUIET HIGH PRESSURE IS OVERHEAD LEADING TO CONTINUED VFR
CONDITIONS OVERNIGHT. THE HIGH SHIFTS EAST TOMORROW AS A WEAK
SURFACE LOW OVER MANITOBA APPROACHES. THE MAIN LOW WILL REMAIN
OVER SOUTHERN CANADA AND WEAKEN AS IT MOVES INTO WESTERN ONTARIO.
AN UPPER LEVEL DISTURBANCE ASSOCIATED WITH THE LOWS WARM FRONT
PASSES OVERHEAD TOMORROW AFTERNOON AND THIS WILL BE THE TRIGGER
FOR PRECIP. THE DISTURBANCE AND FRONT WILL BE WEAKENING AS THEY
MOVE OVERHEAD SO HAVE LIMITED CONFIDENCE IN HOW LONG THE BAND OF
PRECIP WILL HOLD TOGETHER. MODELS ARE ALSO SLOWING THE SYSTEM SO
THE ONSET OF PRECIP MAY BE LATER THAN CURRENTLY INDICATED.

AS SUCH ONLY HAVE PRECIP MENTIONED AT ORD. COULD SEE PRECIP
REACHING RFD ARND 18Z...BUT GIVEN THE SLOWING TREND...OPTED TO
KEEP -SHRA OUT OF THE RFD TAF FOR NOW.

GUIDANCE DIFFERS ON CIGS WITH THE PRECIP AS WELL...WITH ONE MODEL
INDICATING MFVR OR LOWER CIGS. GIVEN THE DIFFERENCES AND WEAKENING
TREND...WENT WITH LOW END VFR CIGS WITH A SCT LATER OF MVFR.

LASTLY...WINDS TURN SSW TOMORROW MORNING AND WILL BE ARND 10 KT.

JEE


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

* MEDIUM CONFIDENCE IN TIMING AND COVERAGE OF -SHRA THURSDAY.

* MEDIUM-LOW CONFIDENCE IN TIMING AND OCCURRENCE OF MVFR CIGS
  THURSDAY.

* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

JEE

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...

324 AM...A LARGE RIDGE OF HIGH PRESSURE EXTENDS FROM QUEBEC INTO
THE WESTERN LAKES. THIS RIDGE WILL MOVE EAST TODAY AND TONIGHT AND
SLOWLY WEAKEN. EASTERLY WINDS WILL CONTINUE TO DIMINISH THIS
MORNING BUT WAVE ACTION...ESPECIALLY ACROSS THE SOUTHWESTERN PART
OF THE LAKE WILL SLOWLY SUBSIDE THIS MORNING. WINDS WILL TURN BACK
SOUTHERLY TONIGHT AND INCREASE ON THURSDAY AS THE GRADIENT
TIGHTENS AHEAD OF AN APPROACHING COLD FRONT WHICH WILL THEN MOVE
ACROSS THE LAKE THURSDAY NIGHT AS IT DISSIPATES. THE FLOW WILL
TURN BACK SOUTHWESTERLY FRIDAY AHEAD OF ANOTHER COLD FRONT WHICH
WILL MOVE ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY MORNING.
WINDS BEHIND THIS FRONT WILL INCREASE TO 15-25 KTS WITH HIGHER
WINDS POSSIBLE OVER THE NORTHERN PART OF THE LAKE. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 221400
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
900 AM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* NONE.

JEE

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

3KFT CIGS CONTINUE TO SLOWLY DISSIPATE AS THEY SPREAD NORTH.
MAINTAINED CIGS FOR A FEW MORE HOURS AT ORD/MDW BUT SCATTERING
SHOULD CONTINUE OVER THE NEXT FEW HOURS.

NO CHANGE TO THE WINDS...STARTING CALM IN MANY LOCATIONS AND LIGHT
NORTHWESTERLY AT ORD/MDW. THESE SHOULD SHIFT TO THE EAST/SOUTHEAST
BY MID MORNING THEN TURN MORE EASTERLY THIS AFTERNOON WITH A
POSSIBLE LAKE BREEZE. PREVAILING SPEEDS SHOULD REMAIN BELOW 10KTS.
WINDS TURN LIGHT SOUTHEASTERLY THIS EVENING THEN SOUTHERLY
OVERNIGHT. CMS

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

JEE

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...

324 AM...A LARGE RIDGE OF HIGH PRESSURE EXTENDS FROM QUEBEC INTO
THE WESTERN LAKES. THIS RIDGE WILL MOVE EAST TODAY AND TONIGHT AND
SLOWLY WEAKEN. EASTERLY WINDS WILL CONTINUE TO DIMINISH THIS
MORNING BUT WAVE ACTION...ESPECIALLY ACROSS THE SOUTHWESTERN PART
OF THE LAKE WILL SLOWLY SUBSIDE THIS MORNING. WINDS WILL TURN BACK
SOUTHERLY TONIGHT AND INCREASE ON THURSDAY AS THE GRADIENT
TIGHTENS AHEAD OF AN APPROACHING COLD FRONT WHICH WILL THEN MOVE
ACROSS THE LAKE THURSDAY NIGHT AS IT DISSIPATES. THE FLOW WILL
TURN BACK SOUTHWESTERLY FRIDAY AHEAD OF ANOTHER COLD FRONT WHICH
WILL MOVE ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY MORNING.
WINDS BEHIND THIS FRONT WILL INCREASE TO 15-25 KTS WITH HIGHER
WINDS POSSIBLE OVER THE NORTHERN PART OF THE LAKE. CMS

&&

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

$$

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

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







000
FXUS63 KLOT 221139
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
639 AM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THIS MORNING.
* EAST WINDS MID MORNING THRU EARLY EVENING. CMS

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

3KFT CIGS CONTINUE TO SLOWLY DISSIPATE AS THEY SPREAD NORTH.
MAINTAINED CIGS FOR A FEW MORE HOURS AT ORD/MDW BUT SCATTERING
SHOULD CONTINUE OVER THE NEXT FEW HOURS.

NO CHANGE TO THE WINDS...STARTING CALM IN MANY LOCATIONS AND LIGHT
NORTHWESTERLY AT ORD/MDW. THESE SHOULD SHIFT TO THE EAST/SOUTHEAST
BY MID MORNING THEN TURN MORE EASTERLY THIS AFTERNOON WITH A
POSSIBLE LAKE BREEZE. PREVAILING SPEEDS SHOULD REMAIN BELOW 10KTS.
WINDS TURN LIGHT SOUTHEASTERLY THIS EVENING THEN SOUTHERLY
OVERNIGHT. CMS

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

* HIGH FOR MVFR CIGS THIS MORNING...MEDIUM FOR CLEARING TIMING.
* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY NIGHT...CHANCE OF SHRA. MVFR POSSIBLE.
* FRIDAY...DRY/VFR. SOUTHWEST WINDS.
* SATURDAY...DRY/VFR. GUSTY NORTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH/SOUTHEAST WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTH/SOUTHWEST WINDS.
* TUESDAY...CHANCE OF SHRA. STRONG/GUSTY WESTERLY WINDS.

&&

.MARINE...

324 AM...A LARGE RIDGE OF HIGH PRESSURE EXTENDS FROM QUEBEC INTO
THE WESTERN LAKES. THIS RIDGE WILL MOVE EAST TODAY AND TONIGHT AND
SLOWLY WEAKEN. EASTERLY WINDS WILL CONTINUE TO DIMINISH THIS
MORNING BUT WAVE ACTION...ESPECIALLY ACROSS THE SOUTHWESTERN PART
OF THE LAKE WILL SLOWLY SUBSIDE THIS MORNING. WINDS WILL TURN BACK
SOUTHERLY TONIGHT AND INCREASE ON THURSDAY AS THE GRADIENT
TIGHTENS AHEAD OF AN APPROACHING COLD FRONT WHICH WILL THEN MOVE
ACROSS THE LAKE THURSDAY NIGHT AS IT DISSIPATES. THE FLOW WILL
TURN BACK SOUTHWESTERLY FRIDAY AHEAD OF ANOTHER COLD FRONT WHICH
WILL MOVE ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY MORNING.
WINDS BEHIND THIS FRONT WILL INCREASE TO 15-25 KTS WITH HIGHER
WINDS POSSIBLE OVER THE NORTHERN PART OF THE LAKE. CMS

&&

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

&&

$$

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

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







000
FXUS63 KLOT 220910
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
410 AM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* MVFR CIGS EARLY THIS MORNING.
* EAST WINDS MID MORNING THRU EARLY EVENING. CMS

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

CIGS AROUND 3KFT CONTINUE ACROSS NORTHEAST IL AND CONFIDENCE AS TO
WHEN THESE WILL SCATTER AND DISSIPATE IS LOW AND TRENDS WILL NEED
TO BE MONITORED. OUTSIDE THIS AREA OF CLOUDS...LIGHT/CALM WINDS
WILL ALLOW SOME PATCHY FOG TO FORM. CMS

PREVIOUS 09Z DISCUSSION...

HIGH PRESSURE WILL MOVE SOUTHEAST ACROSS THE REGION TODAY. LIGHT
EAST/NORTHEAST WINDS WILL SHIFT SOUTHEAST LATER THIS MORNING...
THEN TURN BACK EAST/NORTHEAST THIS AFTERNOON WITH A POSSIBLE LAKE
BREEZE. PREVAILING SPEEDS WILL LIKELY REMAIN UNDER 10KTS.

HIGH MVFR CIGS AROUND 3KFT WILL SLOWLY SCATTER OUT AND DISSIPATE
EARLY THIS MORNING WITH SKC EXPECTED LATER TODAY WITH INCREASING
HIGH CLOUDS TONIGHT. CMS

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

* HIGH FOR MVFR CIGS EARLY THIS MORNING...LOW FOR CLEARING TIMING.
* HIGH FOR WIND THRU THE PERIOD. CMS

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

324 AM...A LARGE RIDGE OF HIGH PRESSURE EXTENDS FROM QUEBEC INTO
THE WESTERN LAKES. THIS RIDGE WILL MOVE EAST TODAY AND TONIGHT AND
SLOWLY WEAKEN. EASTERLY WINDS WILL CONTINUE TO DIMINISH THIS
MORNING BUT WAVE ACTION...ESPECIALLY ACROSS THE SOUTHWESTERN PART
OF THE LAKE WILL SLOWLY SUBSIDE THIS MORNING. WINDS WILL TURN BACK
SOUTHERLY TONIGHT AND INCREASE ON THURSDAY AS THE GRADIENT
TIGHTENS AHEAD OF AN APPROACHING COLD FRONT WHICH WILL THEN MOVE
ACROSS THE LAKE THURSDAY NIGHT AS IT DISSIPATES. THE FLOW WILL
TURN BACK SOUTHWESTERLY FRIDAY AHEAD OF ANOTHER COLD FRONT WHICH
WILL MOVE ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY MORNING.
WINDS BEHIND THIS FRONT WILL INCREASE TO 15-25 KTS WITH HIGHER
WINDS POSSIBLE OVER THE NORTHERN PART OF THE LAKE. CMS

&&

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

&&

$$

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

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







000
FXUS63 KLOT 220824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
324 AM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* MVFR CIGS EARLY THIS MORNING.
* EAST WINDS MID MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL MOVE SOUTHEAST ACROSS THE REGION TODAY. LIGHT
EAST/NORTHEAST WINDS WILL SHIFT SOUTHEAST LATER THIS MORNING...
THEN TURN BACK EAST/NORTHEAST THIS AFTERNOON WITH A POSSIBLE LAKE
BREEZE. PREVAILING SPEEDS WILL LIKELY REMAIN UNDER 10KTS.

HIGH MVFR CIGS AROUND 3KFT WILL SLOWLY SCATTER OUT AND DISSIPATE
EARLY THIS MORNING WITH SKC EXPECTED LATER TODAY WITH INCREASING
HIGH CLOUDS TONIGHT. CMS

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

* MEDIUM FOR MVFR CIGS EARLY THIS MORNING.
* HIGH FOR WIND THRU THE PERIOD. CMS

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

324 AM...A LARGE RIDGE OF HIGH PRESSURE EXTENDS FROM QUEBEC INTO
THE WESTERN LAKES. THIS RIDGE WILL MOVE EAST TODAY AND TONIGHT AND
SLOWLY WEAKEN. EASTERLY WINDS WILL CONTINUE TO DIMINISH THIS
MORNING BUT WAVE ACTION...ESPECIALLY ACROSS THE SOUTHWESTERN PART
OF THE LAKE WILL SLOWLY SUBSIDE THIS MORNING. WINDS WILL TURN BACK
SOUTHERLY TONIGHT AND INCREASE ON THURSDAY AS THE GRADIENT
TIGHTENS AHEAD OF AN APPROACHING COLD FRONT WHICH WILL THEN MOVE
ACROSS THE LAKE THURSDAY NIGHT AS IT DISSIPATES. THE FLOW WILL
TURN BACK SOUTHWESTERLY FRIDAY AHEAD OF ANOTHER COLD FRONT WHICH
WILL MOVE ACROSS THE LAKE FRIDAY NIGHT INTO SATURDAY MORNING.
WINDS BEHIND THIS FRONT WILL INCREASE TO 15-25 KTS WITH HIGHER
WINDS POSSIBLE OVER THE NORTHERN PART OF THE LAKE. CMS

&&

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

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 AM WEDNESDAY.

&&

$$

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

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







000
FXUS63 KLOT 220811
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
311 AM CDT WED OCT 22 2014

.DISCUSSION...
310 AM CDT

TRANSITION AWAY FROM THE BELOW AVERAGE TEMPS OF LATE TO WARMER THAN
AVERAGE TEMPS BY THIS WEEKEND INTO EARLY NEXT WEEK STILL ON
TRACK...WITH A COUPLE SHOTS OF RAIN POSSIBLE.

ANY LINGERING LAKE CLOUDINESS IN NE IL EARLY THIS MORNING WILL FADE
WITH 100% SUNSHINE LOOKING LIKELY TODAY. TEMPERATURES SHOULD
MODERATE SEVERAL DEGREES OVER YESTERDAY MOST AREAS...THOUGH LAKE
ADJACENT AREAS OF NE IL WILL STILL FACE ONSHORE WINDS AND COOLER
TEMPS THAN THE REMAINDER OF THE CWA. MAINLY CLEAR SKIES AND LIGHT
WINDS SHOULD ALLOW FOR ANOTHER CHILLY NIGHT TONIGHT.

SKIES WILL CLOUD OVER THURSDAY LEAVING OUR PROSPECTS FOR SEEING THE
SOLAR ECLIPSE THURSDAY AFTERNOON DIM. SHARP UPPER TROUGH WILL
APPROACH FROM THE WEST THURSDAY AND DESPITE RELATIVE LACK OF
MOISTURE...FORCING LOOKS TO BE STRONG ENOUGH TO PROVIDE FOR A DECENT
SHOT OF SHOWERS SPREADING FROM WEST TO EAST THURSDAY AND ENDING
EASTERN CWA THURSDAY EVENING. SOUTHERN EXTENT OF THIS SHORTWAVE WILL
BE WEAKENING AS IT RUNS INTO THE NARROW RIDGE BEHIND THE LARGE
EASTERN CONUS UPPER LOW. THE ANTICIPATED GRADUAL WEAKENING OF THE
TROUGH IN OUR NECK OF THE WOODS IS REASONING FOR HIGHEST POPS WEST
AND LOWER POPS EAST...THOUGH GUIDANCE OFTEN WEAKENS THESE SYSTEMS
TOO QUICKLY AND HAVE GENERALLY GONE WITH HIGHER MOS POPS FOR THIS
SYSTEM.

WARM ADVECTION WILL RAMP UP BEHIND THIS SYSTEM AS UPPER RIDGING
BRIEFLY BUILDS INTO THE AREA FRIDAY ALLOWING FOR MODERATING TEMPS.
THE 00Z WRF-NAM DID HAVE A STRONGER TROUGH MOVING THROUGH ON FRIDAY
WITH SOME LIGHT QPF...BUT GIVEN THE GLOBAL MODELS ALL MUCH MORE
MUTED WITH THIS TROUGH WITH NO PRECIP HAVE BUMPED UP SKY COVER A BIT
AND POPS UP TO 10% BUT KEPT FORECAST DRY FOR NOW.

PATTERN WILL REMAIN QUITE AMPLIFIED THROUGH THE WEEKEND WITH DEEP
TROUGH TO OUR NE AND UPPER RIDGE BUILDING INTO THE CENTRAL CONUS.
GUIDANCE HAS TRENDED A BIT FARTHER WEST WITH THE NE CONUS UPPER
TROUGH THIS WEEKEND PLACING OUR CWA A BIT CLOSER TO THE COOLER AIR
MASS...BUT STILL EXPECT HIGHS TO MAKE IT INTO THE 60S. IT NOW
APPEARS THE GFS...ECMWF...AND GEM HAVE MONDAY AS OUR WARMEST DAY
WITH 850MB TEMPS PROGGED TO BE AROUND 1.5 STANDARD DEVIATIONS ABOVE
AVERAGE. GIVEN THE INCREASING SOUTHERLY WINDS THINK MOST OF THE CWA
STANDS A DECENT SHOT TO TAG 70F WITH ENSEMBLE MAX TEMPS AS WARM AS
THE MID TO UPPER 70S. COLD FRONT LOOKS TO END OUR BRIEF STINT OF
INDIAN SUMMER MONDAY NIGHT OR TUESDAY WITH SHOWERS AND POSSIBLY SOME
THUNDERSTORMS ACCOMPANYING THE FRONT.

IZZI

&&

.AVIATION...

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

* MVFR CIGS EARLY THIS MORNING.
* EAST WINDS MID MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL MOVE SOUTHEAST ACROSS THE REGION TODAY. LIGHT
EAST/NORTHEAST WINDS WILL SHIFT SOUTHEAST LATER THIS MORNING...
THEN TURN BACK EAST/NORTHEAST THIS AFTERNOON WITH A POSSIBLE LAKE
BREEZE. PREVAILING SPEEDS WILL LIKELY REMAIN UNDER 10KTS.

HIGH MVFR CIGS AROUND 3KFT WILL SLOWLY SCATTER OUT AND DISSIPATE
EARLY THIS MORNING WITH SKC EXPECTED LATER TODAY WITH INCREASING
HIGH CLOUDS TONIGHT. CMS

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

* MEDIUM FOR MVFR CIGS EARLY THIS MORNING.
* HIGH FOR WIND THRU THE PERIOD. CMS

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 AM WEDNESDAY.

&&

$$

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

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







000
FXUS63 KLOT 220532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 AM CDT WED OCT 22 2014

.DISCUSSION...
749 PM CDT

FOR AN EVENING UPDATE HAVE HELD ON TO FORECAST CLOUD COVER LONGER
TONIGHT...NAMELY FOR THE CENTRAL AND SOUTHERN PARTS OF THE
CHICAGO METRO AND SOUTH AND SOUTHWEST FROM THERE.

SURFACE RIDGING IS BUILDING SOUTHWARD THIS EVENING INTO NORTHERN
ILLINOIS AND WIND SPEEDS HAVE COME DOWN QUITE A BIT OUTSIDE OF THE
IMMEDIATE LAKE SHORE. SUBSIDENCE ALOFT IS CONTINUING AS WELL PER
WATER VAPOR AND DIAGNOSTIC MODEL SOUNDINGS...BUT CLOUDS HAVE
SLOWED THEIR RATE OF DIMINISHING...POSSIBLY DUE TO NO MORE CLOUD
TOP WARMING FROM THE SUN.

WHILE THE CLOUD LAYER IS VERY THIN IN DEPTH AS INDICATED BY
REGIONAL AMDAR DATA...FORESEE CLOUDS HANGING ON A WHILE LONGER
WITH NIGHTFALL. THE LOCAL 8KM ARW...AND RAP TO SOME DEGREE...INDICATE
LITTLE MOVEMENT IN THE MOST SOLID SATURATION ALONG AND EAST OF
INTERSTATE 55 THROUGH MIDNIGHT...AND THEN AS CLOUD-BEARING FLOW
TURNS EASTERLY THE MOISTURE ADVECTS WITH IT AND GRADUALLY THINS.
THIS WAS GENERALLY DEPICTED IN THE PREVIOUS FORECAST BUT JUST
HAVE SHIFTED BACK IN TIMING SEVERAL HOURS.

MADE SOME ADJUSTMENTS TO HOURLY TEMPERATURES TO BETTER FIT THIS
REASONING AND THAT DID LEAD TO AN INCREASE IN MIN TEMPS IN A FEW
PLACES...BUT OTHERWISE NO CHANGES MADE.

MTF

//PREV DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.

FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* MVFR CIGS EARLY THIS MORNING.
* EAST WINDS MID MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL MOVE SOUTHEAST ACROSS THE REGION TODAY. LIGHT
EAST/NORTHEAST WINDS WILL SHIFT SOUTHEAST LATER THIS MORNING...
THEN TURN BACK EAST/NORTHEAST THIS AFTERNOON WITH A POSSIBLE LAKE
BREEZE. PREVAILING SPEEDS WILL LIKELY REMAIN UNDER 10KTS.

HIGH MVFR CIGS AROUND 3KFT WILL SLOWLY SCATTER OUT AND DISSIPATE
EARLY THIS MORNING WITH SKC EXPECTED LATER TODAY WITH INCREASING
HIGH CLOUDS TONIGHT. CMS

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

* MEDIUM FOR MVFR CIGS EARLY THIS MORNING.
* HIGH FOR WIND THRU THE PERIOD. CMS

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 AM WEDNESDAY.

&&

$$

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

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







000
FXUS63 KLOT 220532
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1232 AM CDT WED OCT 22 2014

.DISCUSSION...
749 PM CDT

FOR AN EVENING UPDATE HAVE HELD ON TO FORECAST CLOUD COVER LONGER
TONIGHT...NAMELY FOR THE CENTRAL AND SOUTHERN PARTS OF THE
CHICAGO METRO AND SOUTH AND SOUTHWEST FROM THERE.

SURFACE RIDGING IS BUILDING SOUTHWARD THIS EVENING INTO NORTHERN
ILLINOIS AND WIND SPEEDS HAVE COME DOWN QUITE A BIT OUTSIDE OF THE
IMMEDIATE LAKE SHORE. SUBSIDENCE ALOFT IS CONTINUING AS WELL PER
WATER VAPOR AND DIAGNOSTIC MODEL SOUNDINGS...BUT CLOUDS HAVE
SLOWED THEIR RATE OF DIMINISHING...POSSIBLY DUE TO NO MORE CLOUD
TOP WARMING FROM THE SUN.

WHILE THE CLOUD LAYER IS VERY THIN IN DEPTH AS INDICATED BY
REGIONAL AMDAR DATA...FORESEE CLOUDS HANGING ON A WHILE LONGER
WITH NIGHTFALL. THE LOCAL 8KM ARW...AND RAP TO SOME DEGREE...INDICATE
LITTLE MOVEMENT IN THE MOST SOLID SATURATION ALONG AND EAST OF
INTERSTATE 55 THROUGH MIDNIGHT...AND THEN AS CLOUD-BEARING FLOW
TURNS EASTERLY THE MOISTURE ADVECTS WITH IT AND GRADUALLY THINS.
THIS WAS GENERALLY DEPICTED IN THE PREVIOUS FORECAST BUT JUST
HAVE SHIFTED BACK IN TIMING SEVERAL HOURS.

MADE SOME ADJUSTMENTS TO HOURLY TEMPERATURES TO BETTER FIT THIS
REASONING AND THAT DID LEAD TO AN INCREASE IN MIN TEMPS IN A FEW
PLACES...BUT OTHERWISE NO CHANGES MADE.

MTF

//PREV DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.

FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* MVFR CIGS EARLY THIS MORNING.
* EAST WINDS MID MORNING THRU EARLY EVENING. CMS

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

HIGH PRESSURE WILL MOVE SOUTHEAST ACROSS THE REGION TODAY. LIGHT
EAST/NORTHEAST WINDS WILL SHIFT SOUTHEAST LATER THIS MORNING...
THEN TURN BACK EAST/NORTHEAST THIS AFTERNOON WITH A POSSIBLE LAKE
BREEZE. PREVAILING SPEEDS WILL LIKELY REMAIN UNDER 10KTS.

HIGH MVFR CIGS AROUND 3KFT WILL SLOWLY SCATTER OUT AND DISSIPATE
EARLY THIS MORNING WITH SKC EXPECTED LATER TODAY WITH INCREASING
HIGH CLOUDS TONIGHT. CMS

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

* MEDIUM FOR MVFR CIGS EARLY THIS MORNING.
* HIGH FOR WIND THRU THE PERIOD. CMS

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 AM WEDNESDAY.

&&

$$

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

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







000
FXUS63 KLOT 220239
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
939 PM CDT TUE OCT 21 2014

.DISCUSSION...
749 PM CDT

FOR AN EVENING UPDATE HAVE HELD ON TO FORECAST CLOUD COVER LONGER
TONIGHT...NAMELY FOR THE CENTRAL AND SOUTHERN PARTS OF THE
CHICAGO METRO AND SOUTH AND SOUTHWEST FROM THERE.

SURFACE RIDGING IS BUILDING SOUTHWARD THIS EVENING INTO NORTHERN
ILLINOIS AND WIND SPEEDS HAVE COME DOWN QUITE A BIT OUTSIDE OF THE
IMMEDIATE LAKE SHORE. SUBSIDENCE ALOFT IS CONTINUING AS WELL PER
WATER VAPOR AND DIAGNOSTIC MODEL SOUNDINGS...BUT CLOUDS HAVE
SLOWED THEIR RATE OF DIMINISHING...POSSIBLY DUE TO NO MORE CLOUD
TOP WARMING FROM THE SUN.

WHILE THE CLOUD LAYER IS VERY THIN IN DEPTH AS INDICATED BY
REGIONAL AMDAR DATA...FORESEE CLOUDS HANGING ON A WHILE LONGER
WITH NIGHTFALL. THE LOCAL 8KM ARW...AND RAP TO SOME DEGREE...INDICATE
LITTLE MOVEMENT IN THE MOST SOLID SATURATION ALONG AND EAST OF
INTERSTATE 55 THROUGH MIDNIGHT...AND THEN AS CLOUD-BEARING FLOW
TURNS EASTERLY THE MOISTURE ADVECTS WITH IT AND GRADUALLY THINS.
THIS WAS GENERALLY DEPICTED IN THE PREVIOUS FORECAST BUT JUST
HAVE SHIFTED BACK IN TIMING SEVERAL HOURS.

MADE SOME ADJUSTMENTS TO HOURLY TEMPERATURES TO BETTER FIT THIS
REASONING AND THAT DID LEAD TO AN INCREASE IN MIN TEMPS IN A FEW
PLACES...BUT OTHERWISE NO CHANGES MADE.

MTF

//PREV DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.

FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* MVFR CIGS AROUND 2,800 FEET AGL HOLDING THROUGH LATER TONIGHT.

KJB

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

MVFR CIGS CONTINUE TO MOVE IN OFF THE LAKE EARLY THIS EVENING VIA A
NORTH-NORTHEASTERLY LOWER LEVEL WIND TRAJECTORY ASSOCIATED WITH A
SURFACE RIDGE OF HIGH PRESSURE BUILDING EASTWARD ACROSS THE UPPER
GREAT LAKES AND OVER EASTERN ONTARIO. IT APPEARS THESE LOW CLOUDS
WILL TRY TO GRADUALLY SCATTERED OUT OVER THE NEXT 2 TO 3 HOURS.
HOWEVER...SOME OF THESE CLOUDS COULD BE A LITTLE SLOWER TO SCATTER
OUT ACROSS THE EASTERN TERMINALS NEAR THE LAKE AS CONDITIONS LOOK
TO REMAIN FAVORABLE FOR SOME CLOUD COVER OVER SOUTHERN LAKE
MICHIGAN. THEREFORE...IT IS POSSIBLE THAT AS THE LOWER LEVEL WINDS
VEER MORE NORTHEASTERLY THIS EVENING...SOME CLOUDS WILL CONTINUE
TO STREAM OFF THE LAKE AND OVER NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA DURING THE EVENING HOURS. I WILL CONTINUE TO
WATCH TRENDS WITH THIS AS THE EXACT TIMING OF SCATTERING IS A BIT
LOWER THAN PREVIOUSLY THOUGHT. THE GOOD NEWS IS THAT CIG HEIGHTS
SHOULD GENERALLY REMAIN AT OR ABOVE 2500 FEET AGL...SO AVIATION
IMPACTS SHOULD BE MINIMAL.

OTHERWISE...THE REMAINDER OF THE PERIOD LOOKS TO BE MAINLY VFR WITH
LIGHT EASTERLY WINDS.

KJB

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

* LOW-MEDIUM WITH EXACT TIMING OF IMPROVING CEILINGS TONIGHT.

* HIGH WITH OTHER FORECAST ELEMENTS.

KJB

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 AM WEDNESDAY.

&&

$$

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

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







000
FXUS63 KLOT 220049 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
749 PM CDT TUE OCT 21 2014

.DISCUSSION...
749 PM CDT

FOR AN EVENING UPDATE HAVE HELD ON TO FORECAST CLOUD COVER LONGER
TONIGHT...NAMELY FOR THE CENTRAL AND SOUTHERN PARTS OF THE
CHICAGO METRO AND SOUTH AND SOUTHWEST FROM THERE.

SURFACE RIDGING IS BUILDING SOUTHWARD THIS EVENING INTO NORTHERN
ILLINOIS AND WIND SPEEDS HAVE COME DOWN QUITE A BIT OUTSIDE OF THE
IMMEDIATE LAKE SHORE. SUBSIDENCE ALOFT IS CONTINUING AS WELL PER
WATER VAPOR AND DIAGNOSTIC MODEL SOUNDINGS...BUT CLOUDS HAVE
SLOWED THEIR RATE OF DIMINISHING...POSSIBLY DUE TO NO MORE CLOUD
TOP WARMING FROM THE SUN.

WHILE THE CLOUD LAYER IS VERY THIN IN DEPTH AS INDICATED BY
REGIONAL AMDAR DATA...FORESEE CLOUDS HANGING ON A WHILE LONGER
WITH NIGHTFALL. THE LOCAL 8KM ARW...AND RAP TO SOME DEGREE...INDICATE
LITTLE MOVEMENT IN THE MOST SOLID SATURATION ALONG AND EAST OF
INTERSTATE 55 THROUGH MIDNIGHT...AND THEN AS CLOUD-BEARING FLOW
TURNS EASTERLY THE MOISTURE ADVECTS WITH IT AND GRADUALLY THINS.
THIS WAS GENERALLY DEPICTED IN THE PREVIOUS FORECAST BUT JUST
HAVE SHIFTED BACK IN TIMING SEVERAL HOURS.

MADE SOME ADJUSTMENTS TO HOURLY TEMPERATURES TO BETTER FIT THIS
REASONING AND THAT DID LEAD TO AN INCREASE IN MIN TEMPS IN A FEW
PLACES...BUT OTHERWISE NO CHANGES MADE.

MTF

&&

.PREV DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.

FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS GRADUALLY DROPPING BELOW 10 KT EARLY THIS
  EVENING.

* MVFR CEILINGS HOLDING ON POSSIBLY THROUGH MID EVENING.

KJB

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

MVFR CIGS CONTINUE TO MOVE IN OFF THE LAKE EARLY THIS EVENING VIA A
NORTH-NORTHEASTERLY LOWER LEVEL WIND TRAJECTORY ASSOCIATED WITH A
SURFACE RIDGE OF HIGH PRESSURE BUILDING EASTWARD ACROSS THE UPPER
GREAT LAKES AND OVER EASTERN ONTARIO. IT APPEARS THESE LOW CLOUDS
WILL TRY TO GRADUALLY SCATTERED OUT OVER THE NEXT 2 TO 3 HOURS.
HOWEVER...SOME OF THESE CLOUDS COULD BE A LITTLE SLOWER TO SCATTER
OUT ACROSS THE EASTERN TERMINALS NEAR THE LAKE AS CONDITIONS LOOK
TO REMAIN FAVORABLE FOR SOME CLOUD COVER OVER SOUTHERN LAKE
MICHIGAN. THEREFORE...IT IS POSSIBLE THAT AS THE LOWER LEVEL WINDS
VEER MORE NORTHEASTERLY THIS EVENING...SOME CLOUDS WILL CONTINUE
TO STREAM OFF THE LAKE AND OVER NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA DURING THE EVENING HOURS. I WILL CONTINUE TO
WATCH TRENDS WITH THIS AS THE EXACT TIMING OF SCATTERING IS A BIT
LOWER THAN PREVIOUSLY THOUGHT. THE GOOD NEWS IS THAT CIG HEIGHTS
SHOULD GENERALLY REMAIN AT OR ABOVE 2500 FEET AGL...SO AVIATION
IMPACTS SHOULD BE MINIMAL.

OTHERWISE...THE REMAINDER OF THE PERIOD LOOKS TO BE MAINLY VFR WITH
LIGHT EASTERLY WINDS.

KJB

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

* MEDIUM-HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW-MEDIUM CONFIDENCE WITH EXACT TIMING OF IMPROVING CEILINGS
  THIS EVENING.

KJB

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

&&

$$

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

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








000
FXUS63 KLOT 212329
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
629 PM CDT TUE OCT 21 2014

.DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.

FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS GRADUALLY DROPPING BELOW 10 KT EARLY THIS
  EVENING.

* MVFR CEILINGS HOLDING ON POSSIBLY THROUGH MID EVENING.

KJB

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

MVFR CIGS CONTINUE TO MOVE IN OFF THE LAKE EARLY THIS EVENING VIA A
NORTH-NORTHEASTERLY LOWER LEVEL WIND TRAJECTORY ASSOCIATED WITH A
SURFACE RIDGE OF HIGH PRESSURE BUILDING EASTWARD ACROSS THE UPPER
GREAT LAKES AND OVER EASTERN ONTARIO. IT APPEARS THESE LOW CLOUDS
WILL TRY TO GRADUALLY SCATTERED OUT OVER THE NEXT 2 TO 3 HOURS.
HOWEVER...SOME OF THESE CLOUDS COULD BE A LITTLE SLOWER TO SCATTER
OUT ACROSS THE EASTERN TERMINALS NEAR THE LAKE AS CONDITIONS LOOK
TO REMAIN FAVORABLE FOR SOME CLOUD COVER OVER SOUTHERN LAKE
MICHIGAN. THEREFORE...IT IS POSSIBLE THAT AS THE LOWER LEVEL WINDS
VEER MORE NORTHEASTERLY THIS EVENING...SOME CLOUDS WILL CONTINUE
TO STREAM OFF THE LAKE AND OVER NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA DURING THE EVENING HOURS. I WILL CONTINUE TO
WATCH TRENDS WITH THIS AS THE EXACT TIMING OF SCATTERING IS A BIT
LOWER THAN PREVIOUSLY THOUGHT. THE GOOD NEWS IS THAT CIG HEIGHTS
SHOULD GENERALLY REMAIN AT OR ABOVE 2500 FEET AGL...SO AVIATION
IMPACTS SHOULD BE MINIMAL.

OTHERWISE...THE REMAINDER OF THE PERIOD LOOKS TO BE MAINLY VFR WITH
LIGHT EASTERLY WINDS.

KJB


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

* MEDIUM-HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* LOW-MEDIUM CONFIDENCE WITH EXACT TIMING OF IMPROVING CEILINGS
  THIS EVENING.

KJB

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

* THURSDAY...CHANCE OF AFTERNOON SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

KJB

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

&&

$$

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

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







000
FXUS63 KLOT 212155
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
455 PM CDT TUE OCT 21 2014

.DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.

FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KT THROUGH EARLY EVENING...THEN
  GRADUALLY ABATING.

* MVFR CEILINGS HOLDING ON THROUGH AROUND 01 TO 02 UTC.

RODRIGUEZ/KB

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

DESPITE HIGH PRESSURE BUILDING ACROSS THE REGION TODAY...CEILINGS
HAVE STILL DEVELOPED WHILE LAKE EFFECT CLOUD COVER CONTINUES TO
MOVE OVERHEAD. THESE BOTH WILL SCATTER/DIMINISH THROUGH THIS
EVENING AS THIS HIGH BUILDS ACROSS THE TERMINALS. BEFORE THIS
OCCURS...PERIODS OF HIGH END MVFR CEILINGS WILL STILL BE POSSIBLE.
THEN EXPECT DRY AND MOSTLY CLEAR SKIES THROUGH THE REST OF THE
FORECAST PERIOD. NORTHEAST WINDS/GUSTS WILL PREVAIL THIS AFTERNOON
BEFORE DIMINISHING LATER THIS EVENING...AND THEN REMAIN MORE
EASTERLY AND UNDER 10 KT EARLY WEDNESDAY MORNING THROUGH THE REST
OF THE FORECAST PERIOD.

RODRIGUEZ

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

* MEDIUM-HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* HIGH CONFIDENCE WITH MVFR CEILINGS THROUGH 01 TO 02 UTC.

RODRIGUEZ/KB

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

&&

$$

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

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







000
FXUS63 KLOT 212155
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
455 PM CDT TUE OCT 21 2014

.DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.

FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KT THROUGH EARLY EVENING...THEN
  GRADUALLY ABATING.

* MVFR CEILINGS HOLDING ON THROUGH AROUND 01 TO 02 UTC.

RODRIGUEZ/KB

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

DESPITE HIGH PRESSURE BUILDING ACROSS THE REGION TODAY...CEILINGS
HAVE STILL DEVELOPED WHILE LAKE EFFECT CLOUD COVER CONTINUES TO
MOVE OVERHEAD. THESE BOTH WILL SCATTER/DIMINISH THROUGH THIS
EVENING AS THIS HIGH BUILDS ACROSS THE TERMINALS. BEFORE THIS
OCCURS...PERIODS OF HIGH END MVFR CEILINGS WILL STILL BE POSSIBLE.
THEN EXPECT DRY AND MOSTLY CLEAR SKIES THROUGH THE REST OF THE
FORECAST PERIOD. NORTHEAST WINDS/GUSTS WILL PREVAIL THIS AFTERNOON
BEFORE DIMINISHING LATER THIS EVENING...AND THEN REMAIN MORE
EASTERLY AND UNDER 10 KT EARLY WEDNESDAY MORNING THROUGH THE REST
OF THE FORECAST PERIOD.

RODRIGUEZ

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

* MEDIUM-HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* HIGH CONFIDENCE WITH MVFR CEILINGS THROUGH 01 TO 02 UTC.

RODRIGUEZ/KB

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

&&

$$

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

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







000
FXUS63 KLOT 212010
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
310 PM CDT TUE OCT 21 2014

.DISCUSSION...
309 PM CDT

MAIN FORECAST CONCERNS FOCUS ON PRECIPITATION CHANCES AND TIMING
WITH A COUPLE OF SYSTEMS WHICH WILL AFFECT THE REGION THURSDAY AND
NEXT MONDAY. ALSO...IT APPEARS THAT SOME 70 DEGREE TEMPERATURES ARE
POSSIBLE FOR PARTS OF THE FORECAST AREA OVER THE WEEKEND AS WELL AS
ON MONDAY.

TONIGHT THROUGH WEDNESDAY NIGHT...

GOES WATER VAPOR IMAGERY DEPICTS A STRONG MID-LEVEL SHORT WAVE
TROUGH WHICH HAD DUG SOUTH ACROSS THE REGION TODAY IS NOW EXITING
THE AREA ACROSS THE OHIO VALLEY TO THE SOUTHEAST. SUBSIDENCE IN THE
WAKE OF THIS FEATURE WAS EVIDENT BOTH IN RISING SURFACE PRESSURE
ACROSS THE CWA...AND IN VISIBLE SATELLITE IMAGERY AS EXTENSIVE AREA
OF STRATOCU ACROSS THE REGION ERODES FROM THE NORTH ACROSS WI/MI AND
LAKE MICHIGAN. EARLIER LAKE-INDUCED SHOWERS HAVE WEAKENED AND FADED
AS EXPECTED DUE TO LOWERING SUBSIDENCE INVERSION AND ASSOCIATED
WARMING ALOFT. CLOUD COVER IS EXPECTED TO CONTINUE TO DECREASE IN
COVERAGE INTO THE EVENING HOURS...WITH PERHAPS JUST SOME PATCHY THIN
SHALLOW STRATOCU LINGERING OFF THE LAKE BY LATE EVENING. LOOKING AT
THE BIGGER PICTURE...HIGH-AMPLITUDE UPPER RIDGE ANALYZED OVER THE
CENTRAL PORTION OF THE NATION WILL MOVE ACROSS THE MISSISSIPPI
VALLEY AND WESTERN/NORTHERN GREAT LAKES REGION THROUGH WEDNESDAY
MORNING...MAINTAINING SUBSIDENCE WHICH SHOULD FURTHER ERODE
LINGERING CLOUDS AND ALLOW SURFACE HIGH PRESSURE RIDGE TO MOVE
ACROSS THE AREA TONIGHT AND WEDNESDAY. WITH CLEARING SKIES AND
DECREASING WINDS ASSOCIATED WITH THE SURFACE RIDGE AXIS TONIGHT...
TEMPS ARE EXPECTED TO DROP OFF INTO THE 30S IN MANY AREAS AWAY FROM
THE IMMEDIATE LAKE MICHIGAN SHORE AND CORE OF CHICAGO. LATE NIGHT
MINS IN THE MID 30S AWAY FROM THE METRO AREA WILL LIKELY ALLOW AREAS
OF FROST TO DEVELOP WHERE WINDS DECOUPLE BECOME LIGHT/VARIABLE.
UPPER AND LOW LEVEL HIGH PRESSURE RIDGES REMAIN OVER THE AREA
WEDNESDAY ALLOWING PLENTIFUL SUNSHINE...THOUGH WITH ONLY MODEST
WARMING DUE TO EASTERLY WIND COMPONENT OFF LAKE AND COOLER UPSTREAM
AIR MASS. A BLEND OF MOS GUIDANCE APPEARS REASONABLE BASED ON RAW
MODEL LOW LEVEL THERMAL FIELDS...WITH WEDNESDAY AFTERNOON MAXES
EXPECTED TO RANGE FROM THE LOW 50S ALONG THE LAKE TO THE UPPER 50S
ACROSS THE FAR WESTERN/SOUTHERN COUNTIES OF THE CWA. ATTENTION THEN
TURNS BACK TOWARD THE NORTHWEST WEDNESDAY NIGHT...AS A WELL-DEFINED
SHORT WAVE TROUGH TRACKS ACROSS THE SOUTHERN CANADIAN PRAIRIES AND
DAKOTAS BEFORE APPROACHING THE UPPER MISSISSIPPI VALLEY WEDNESDAY
EVENING. HEIGHT/PRESSURE FALLS ACROSS THE UPPER MIDWEST NUDGES THE
SURFACE RIDGE AWAY TO OUR EAST AND INDUCES INCREASING
SOUTH-SOUTHEAST WINDS AHEAD OF THE APPROACHING SURFACE TROUGH
OVERNIGHT. CLEAR-PARTLY CLOUDY CONDITIONS AND LIGHT WINDS WILL
LIKELY ALLOW FOR QUICK DECOUPLING OF BOUNDARY LAYER WINDS EARLY
WEDNESDAY EVENING WITH TEMPS DROPPING INTO THE 30S AGAIN IN OUTLYING
AREAS...THOUGH SOME INCREASE IN HIGH CLOUDS AND THE INCREASE IN
WINDS OVERNIGHT WILL LIKELY LIMIT FROST SOMEWHAT.

THURSDAY THROUGH FRIDAY...

THE UPPER MIDWEST SHORT WAVE CONTINUES TO MOVE EAST-SOUTHEAST INTO
THE GREAT LAKES REGION THURSDAY...WITH THE BEST ORGANIZED DEEP LIFT
GENERALLY NORTH OF THE WFO CHICAGO CWA. THE MID-LEVEL TROUGH AXIS
DOES SHIFT ACROSS THE AREA LATER IN THE DAY AND OVERNIGHT HOWEVER...
THOUGH WITH MOISTURE RETURN FROM THE GULF INITIALLY BLOCKED BY THE
SURFACE HIGH PRESSURE RIDGE WHICH EXTENDS SOUTHWEST ACROSS THE
ARKLATEX REGION FOR MUCH OF THE PERIOD. THUS MOISTURE RETURN IS NOT
OVERLY IMPRESSIVE WITH THIS SYSTEM...THOUGH A PERIOD OF SHOWERS DOES
LOOK FAIRLY LIKELY THURSDAY INTO THURSDAY NIGHT. PRECIP POTENTIAL
LOOKS TO INCREASE AHEAD OF THE MID-LEVEL TROUGH AS IT MOVES INTO
NORTH CENTRAL IL DURING THE MID-LATE MORNING HOURS AND SPREADING
INTO NORTHEAST IL DURING THE AFTERNOON. FORCING WEAKENS THURSDAY
EVENING AS THE TROUGH RUNS INTO THE WEAKENING UPPER RIDGE...WITH
PRECIP EXPECTED TO BECOME MORE SPOTTY THURSDAY NIGHT AS IT MOVES
ACROSS THE EASTERN HALF OF THE FORECAST AREA. MID-LEVEL TROUGH AND
WEAKENING SURFACE TROUGH/COLD FRONT OF PACIFIC ORIGIN PASS EAST OF
THE AREA FRIDAY MORNING...WITH WEAK HIGH PRESSURE BUILDING IN DURING
THE DAY. TEMPERATURES ACTUALLY WARM IN THE WAKE OF THIS SYSTEM AS
THE SURFACE RIDGE DRIFTS EAST DURING THE DAY AND WESTERLY FLOW ALOFT
AROUND REBUILDING UPPER RIDGE OVER THE PLAINS ALLOWS WARM ADVECTION
BY AFTERNOON. MODEL THERMAL PROGS INDICATE SOME LOW-MID 60S ACROSS
NORTHERN IL FRIDAY AFTERNOON.


FRIDAY NIGHT THROUGH TUESDAY...

LONGER RANGE MODEL GUIDANCE IN GOOD AGREEMENT IN SPREADING BROAD
UPPER RIDGE EASTWARD FROM THE PLAINS AND ACROSS THE MIDWEST AND
GREAT LAKES REGION THROUGH THE WEEKEND...WHILE DEEP UPPER TROUGH
MOVES INTO THE WESTERN CONUS. MODELS DEPICT STRONG SOUTHERLY FLOW
AND WARM ADVECTION DEVELOPING AS SURFACE LOW PRESSURE DEVELOPS AND
LIFTS NORTHEAST ACROSS THE PLAINS AND THE UPPER MIDWEST SUNDAY...
THOUGH AGAIN WITH LIMITED MOISTURE RETURN FOR THE MAGNITUDE OF THE
FLOW. THIS ALLOWS US TO WARM UP SIGNIFICANTLY HOWEVER...WITH HIGHS
LIKELY GETTING ABOVE 70 DEGREES SATURDAY AND SUNDAY ACROSS PORTIONS
OF THE CWA...AND OVER MOST OF IT MONDAY. SURFACE TROUGH/COLD FRONT
APPROACHES MONDAY WITH AN ATTENDANT CHANCE OF RAIN AND INCREASED
CLOUD COVER. A SECOND LOW IS DEPICTED LIFTING ACROSS THE AREA MONDAY
NIGHT-TUESDAY MAINTAINING RAIN THREAT...AND ALSO LEADING TO MUCH
COOLER WEATHER AGAIN TUESDAY BEHIND THE SYSTEM COLD FRONT.

RATZER

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KT AND GUSTY THROUGH EARLY EVENING.

* MVFR CEILINGS THROUGH AFTERNOON.

RODRIGUEZ

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

DESPITE HIGH PRESSURE BUILDING ACROSS THE REGION TODAY...CEILINGS
HAVE STILL DEVELOPED WHILE LAKE EFFECT CLOUD COVER CONTINUES TO
MOVE OVERHEAD. THESE BOTH WILL SCATTER/DIMINISH THROUGH THIS
EVENING AS THIS HIGH BUILDS ACROSS THE TERMINALS. BEFORE THIS
OCCURS...PERIODS OF HIGH END MVFR CEILINGS WILL STILL BE POSSIBLE.
THEN EXPECT DRY AND MOSTLY CLEAR SKIES THROUGH THE REST OF THE
FORECAST PERIOD. NORTHEAST WINDS/GUSTS WILL PREVAIL THIS AFTERNOON
BEFORE DIMINISHING LATER THIS EVENING...AND THEN REMAIN MORE
EASTERLY AND UNDER 10 KT EARLY WEDNESDAY MORNING THROUGH THE REST
OF THE FORECAST PERIOD.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* HIGH CONFIDENCE WITH MVFR CEILINGS...MEDIUM CONFIDENCE OF
  DURATION.

RODRIGUEZ

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

&&

$$

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

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








000
FXUS63 KLOT 212005
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
305 PM CDT TUE OCT 21 2014

.DISCUSSION...
218 AM CDT

BELOW AVERAGE TEMPERATURES THE NEXT COUPLE OF DAYS WILL GRADUALLY
GIVE WAY TO A BOUT OF INDIAN SUMMER OVER THE WEEKEND.

WATER VAPOR IMAGERY SHOWS AN AMPLIFYING UPPER TROUGH OVER THE
EASTERN CONUS THIS MORNING WITH LAST EVENING`S UPPER AIR ANALYSIS
SHOWING A POCKET OF SUB-FREEZING 850MB TEMPS ADVECTING SOUTH INTO
THE WESTERN GREAT LAKES REGION. THE CHILLY AIR MOVING OVER THE
RELATIVELY MILDER LAKE WATER IS CURRENTLY RESULTING IN A MARGINAL
LAKE EFFECT SHOWER SET-UP WITH SCATTERED LIGHT SHOWERS OR SPRINKLES
SHOWING UP OVER SOUTHERN LM INTO NW IN. LOW LEVEL FLOW WILL VEER TO
MORE NORTHEASTERLY DIRECTION TODAY AND SEND SOME OF THE LAKE EFFECT
CLOUDINESS AND POTENTIALLY SPRINKLES/LIGHT SHOWERS INTO EXTREME NE
IL THIS MORNING. RELATIVELY LOW INVERSION HEIGHTS AND SOMEWHAT WEAK
INSTABILITY MAKE THE CHANCES OF MEASURABLE PRECIP LOW AND HAVE KEPT
POPS IN THE LOWER END OF THE CHANCE CATEGORY. CLOUDINESS SHOULD BE
MOST PREVALENT TODAY NEAR THE LAKE WITH BETTER INCREASINGLY SUNNY
SKIES WELL INLAND. CLOUD COVER SHOULD KEEP HIGHS STRUGGLING INTO THE
LOWER 50S IN NE IL WHILE MID OR EVEN UPPER 50S ARE POSSIBLE OUT
TOWARD MENDOTA AND FAR SOUTHWESTERN CWA WHERE MORE SUN CAN BE
EXPECTED.

LOW CONFIDENCE IN THE EXTENT OF LAKE CLOUDINESS TONIGHT...WHICH
WOULD PLAY A ROLE IN LOW TEMPS. MORE CLOUDS NEAR THE LAKE WOULD
RESULT IN LOWS A COUPLE DEGREES WARMER THAN CURRENTLY FORECAST AND
VICE VERSA IF MAINLY CLEAR. SUNNY SKIES ARE EXPECTED WEDNESDAY AS
TRANSIENT UPPER RIDGE BUILDS INTO THE AREA BETWEEN DEPARTING DEEP
UPPER TROUGH/LOW AND THE NEXT STRONG NORTHERN STREAM SHORTWAVE
SLATED TO ARRIVE IN OUR AREA LATER THURSDAY. NOT LOOKING FOR MUCH OF
A CHANCE OF SUBSTANTIAL WARMING WEDNESDAY WITH A STILL SOMEWHAT COOL
EASTERLY LOW LEVEL FLOW AND ONLY WEAK LOW LEVEL WARM AIR ADVECTION.

BY THURSDAY SHOWER CHANCES WILL BE ON THE INCREASE AS SHARP NORTHERN
STREAM TROUGH TRACKS SOUTHEAST INTO THE WESTERN LAKES. LACK OF
RETURN FLOW SHOULD RESULT IN LIMITED MOISTURE FOR THE SYSTEM...BUT
FAIRLY STRONG FORCING SHOULD ALLOW FOR A PERIOD OF SHOWERS ACROSS
THE CWA THURSDAY AFTERNOON OR EVENING. NOT MUCH COOLING BEHIND THIS
SYSTEM FRIDAY...THEN A FAST MOVING WEAK CANADIAN COLD FRONT SHOULD
BRING A BRIEF COOL DOWN SATURDAY BEFORE MORE SUBSTANTIAL WARM AIR
ADVECTION SUNDAY INTO MONDAY LIKELY SENDS TEMPERATURES NEAR IF NOT
INTO THE 70S ACROSS THE CWA. MEDIUM RANGE MODELS DO SHOW A
PROGRESSIVE LONG WAVE TROUGH MOVING ACROSS THE CONUS BY EARLY NEXT
WEEK WITH COLD FRONT LIKELY TO ARRIVE LATER MONDAY OR TUESDAY
BRINGING AN END TO OUR BRIEF BUT POTENTIALLY IMPRESSIVE WARM UP.

IZZI

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KT AND GUSTY THROUGH EARLY EVENING.

* MVFR CEILINGS THROUGH AFTERNOON.

RODRIGUEZ

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

DESPITE HIGH PRESSURE BUILDING ACROSS THE REGION TODAY...CEILINGS
HAVE STILL DEVELOPED WHILE LAKE EFFECT CLOUD COVER CONTINUES TO
MOVE OVERHEAD. THESE BOTH WILL SCATTER/DIMINISH THROUGH THIS
EVENING AS THIS HIGH BUILDS ACROSS THE TERMINALS. BEFORE THIS
OCCURS...PERIODS OF HIGH END MVFR CEILINGS WILL STILL BE POSSIBLE.
THEN EXPECT DRY AND MOSTLY CLEAR SKIES THROUGH THE REST OF THE
FORECAST PERIOD. NORTHEAST WINDS/GUSTS WILL PREVAIL THIS AFTERNOON
BEFORE DIMINISHING LATER THIS EVENING...AND THEN REMAIN MORE
EASTERLY AND UNDER 10 KT EARLY WEDNESDAY MORNING THROUGH THE REST
OF THE FORECAST PERIOD.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* HIGH CONFIDENCE WITH MVFR CEILINGS...MEDIUM CONFIDENCE OF
  DURATION.

RODRIGUEZ

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

&&

$$

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

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







000
FXUS63 KLOT 211914
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
214 PM CDT TUE OCT 21 2014

.DISCUSSION...
218 AM CDT

BELOW AVERAGE TEMPERATURES THE NEXT COUPLE OF DAYS WILL GRADUALLY
GIVE WAY TO A BOUT OF INDIAN SUMMER OVER THE WEEKEND.

WATER VAPOR IMAGERY SHOWS AN AMPLIFYING UPPER TROUGH OVER THE
EASTERN CONUS THIS MORNING WITH LAST EVENING`S UPPER AIR ANALYSIS
SHOWING A POCKET OF SUB-FREEZING 850MB TEMPS ADVECTING SOUTH INTO
THE WESTERN GREAT LAKES REGION. THE CHILLY AIR MOVING OVER THE
RELATIVELY MILDER LAKE WATER IS CURRENTLY RESULTING IN A MARGINAL
LAKE EFFECT SHOWER SET-UP WITH SCATTERED LIGHT SHOWERS OR SPRINKLES
SHOWING UP OVER SOUTHERN LM INTO NW IN. LOW LEVEL FLOW WILL VEER TO
MORE NORTHEASTERLY DIRECTION TODAY AND SEND SOME OF THE LAKE EFFECT
CLOUDINESS AND POTENTIALLY SPRINKLES/LIGHT SHOWERS INTO EXTREME NE
IL THIS MORNING. RELATIVELY LOW INVERSION HEIGHTS AND SOMEWHAT WEAK
INSTABILITY MAKE THE CHANCES OF MEASURABLE PRECIP LOW AND HAVE KEPT
POPS IN THE LOWER END OF THE CHANCE CATEGORY. CLOUDINESS SHOULD BE
MOST PREVALENT TODAY NEAR THE LAKE WITH BETTER INCREASINGLY SUNNY
SKIES WELL INLAND. CLOUD COVER SHOULD KEEP HIGHS STRUGGLING INTO THE
LOWER 50S IN NE IL WHILE MID OR EVEN UPPER 50S ARE POSSIBLE OUT
TOWARD MENDOTA AND FAR SOUTHWESTERN CWA WHERE MORE SUN CAN BE
EXPECTED.

LOW CONFIDENCE IN THE EXTENT OF LAKE CLOUDINESS TONIGHT...WHICH
WOULD PLAY A ROLE IN LOW TEMPS. MORE CLOUDS NEAR THE LAKE WOULD
RESULT IN LOWS A COUPLE DEGREES WARMER THAN CURRENTLY FORECAST AND
VICE VERSA IF MAINLY CLEAR. SUNNY SKIES ARE EXPECTED WEDNESDAY AS
TRANSIENT UPPER RIDGE BUILDS INTO THE AREA BETWEEN DEPARTING DEEP
UPPER TROUGH/LOW AND THE NEXT STRONG NORTHERN STREAM SHORTWAVE
SLATED TO ARRIVE IN OUR AREA LATER THURSDAY. NOT LOOKING FOR MUCH OF
A CHANCE OF SUBSTANTIAL WARMING WEDNESDAY WITH A STILL SOMEWHAT COOL
EASTERLY LOW LEVEL FLOW AND ONLY WEAK LOW LEVEL WARM AIR ADVECTION.

BY THURSDAY SHOWER CHANCES WILL BE ON THE INCREASE AS SHARP NORTHERN
STREAM TROUGH TRACKS SOUTHEAST INTO THE WESTERN LAKES. LACK OF
RETURN FLOW SHOULD RESULT IN LIMITED MOISTURE FOR THE SYSTEM...BUT
FAIRLY STRONG FORCING SHOULD ALLOW FOR A PERIOD OF SHOWERS ACROSS
THE CWA THURSDAY AFTERNOON OR EVENING. NOT MUCH COOLING BEHIND THIS
SYSTEM FRIDAY...THEN A FAST MOVING WEAK CANADIAN COLD FRONT SHOULD
BRING A BRIEF COOL DOWN SATURDAY BEFORE MORE SUBSTANTIAL WARM AIR
ADVECTION SUNDAY INTO MONDAY LIKELY SENDS TEMPERATURES NEAR IF NOT
INTO THE 70S ACROSS THE CWA. MEDIUM RANGE MODELS DO SHOW A
PROGRESSIVE LONG WAVE TROUGH MOVING ACROSS THE CONUS BY EARLY NEXT
WEEK WITH COLD FRONT LIKELY TO ARRIVE LATER MONDAY OR TUESDAY
BRINGING AN END TO OUR BRIEF BUT POTENTIALLY IMPRESSIVE WARM UP.

IZZI

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KT AND GUSTY THROUGH EARLY EVENING.

* MVFR CEILINGS POSSIBLE THROUGH AFTERNOON.

RODRIGUEZ

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

DESPITE HIGH PRESSURE BUILDING ACROSS THE REGION TODAY...CEILINGS
HAVE STILL DEVELOPED WHILE LAKE EFFECT CLOUD COVER CONTINUES TO
MOVE OVERHEAD. THESE BOTH WILL SCATTER/DIMINISH THROUGH THIS
EVENING AS THIS HIGH BUILDS ACROSS THE TERMINALS. BEFORE THIS
OCCURS...PERIODS OF HIGH END MVFR CEILINGS WILL STILL BE POSSIBLE.
THEN EXPECT DRY AND MOSTLY CLEAR SKIES THROUGH THE REST OF THE
FORECAST PERIOD. NORTHEAST WINDS/GUSTS WILL PREVAIL THIS AFTERNOON
BEFORE DIMINISHING LATER THIS EVENING...AND THEN REMAIN MORE
EASTERLY AND UNDER 10 KT EARLY WEDNESDAY MORNING THROUGH THE REST
OF THE FORECAST PERIOD.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH MVFR CEILINGS...MEDIUM CONFIDENCE OF
  DURATION.

RODRIGUEZ

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

215 PM...LOW PRESSURE OVER WESTERN NEW YORK WILL MERGE WITH ANOTHER
LOW OVER NEAR THE DELMARVA AREA TONIGHT...AND RAPIDLY DEEPEN
WEDNESDAY NIGHT AND THURSDAY JUST SOUTH OF CAPE COD. THIS LOW WILL
THEN TRACK NORTHEAST TO NOVA SCOTIA BY SATURDAY MORNING.
MEANWHILE...HIGH PRESSURE CENTERED OVER THE SOUTHERN TIP OF JAMES
BAY...WITH HIGH PRESSURE RIDGING EXTENDING THROUGH THE MIDDLE
MISSISSIPPI VALLEY...WILL SLOWLY BUILD EAST. THE BRISK
NORTHEASTERLY WINDS CURRENTLY OVER THE LAKE WILL DIMINISH AND
BECOME LIGHT AND VARIABLE LATE TONIGHT AND EARLY WEDNESDAY AS THE
RIDGE AXIS CROSSES THE LAKE. WHILE WINDS SHOULD DROP BELOW SMALL
CRAFT ADVISORY LEVELS DURG THE AFTERNOON AND EARLY THIS
EVENING...RESIDUAL WAVE ACTION WILL BE SLOWER TO DAMPEN AND STILL
EXPECT THAT WAVES WILL REMAIN...ABOVE SMALL CRAFT ADVISORY LEVELS
THROUGH MUCH OF THE NIGHT. AS THE RIDGE MOVES TO THE EAST OF THE
LAKE WEDNESDAY NIGHT...A TROUGH OF LOW PRESSURE WILL CROSS THE
CENTRAL PLAINS...REACHING THE UPPER MISSISSIPPI VALLEY BY THURSDAY
MORNING. THIS WILL SET UP A STRENGTHENING SOUTHERLY GRADIENT OVER
THE LAKE WITH WINDS INCREASING TO ARND 20-25KT THURSDAY AFTERNOON.
WINDS WILL REMAIN SOUTHERLY UNTIL AN ASSOCIATED WEAK COLD FRONT
PUSHES ACROSS THE LAKE THURSDAY NIGHT.

KREIN

&&

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

&&

$$

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

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







000
FXUS63 KLOT 211805
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
105 PM CDT TUE OCT 21 2014

.DISCUSSION...
218 AM CDT

BELOW AVERAGE TEMPERATURES THE NEXT COUPLE OF DAYS WILL GRADUALLY
GIVE WAY TO A BOUT OF INDIAN SUMMER OVER THE WEEKEND.

WATER VAPOR IMAGERY SHOWS AN AMPLIFYING UPPER TROUGH OVER THE
EASTERN CONUS THIS MORNING WITH LAST EVENING`S UPPER AIR ANALYSIS
SHOWING A POCKET OF SUB-FREEZING 850MB TEMPS ADVECTING SOUTH INTO
THE WESTERN GREAT LAKES REGION. THE CHILLY AIR MOVING OVER THE
RELATIVELY MILDER LAKE WATER IS CURRENTLY RESULTING IN A MARGINAL
LAKE EFFECT SHOWER SET-UP WITH SCATTERED LIGHT SHOWERS OR SPRINKLES
SHOWING UP OVER SOUTHERN LM INTO NW IN. LOW LEVEL FLOW WILL VEER TO
MORE NORTHEASTERLY DIRECTION TODAY AND SEND SOME OF THE LAKE EFFECT
CLOUDINESS AND POTENTIALLY SPRINKLES/LIGHT SHOWERS INTO EXTREME NE
IL THIS MORNING. RELATIVELY LOW INVERSION HEIGHTS AND SOMEWHAT WEAK
INSTABILITY MAKE THE CHANCES OF MEASURABLE PRECIP LOW AND HAVE KEPT
POPS IN THE LOWER END OF THE CHANCE CATEGORY. CLOUDINESS SHOULD BE
MOST PREVALENT TODAY NEAR THE LAKE WITH BETTER INCREASINGLY SUNNY
SKIES WELL INLAND. CLOUD COVER SHOULD KEEP HIGHS STRUGGLING INTO THE
LOWER 50S IN NE IL WHILE MID OR EVEN UPPER 50S ARE POSSIBLE OUT
TOWARD MENDOTA AND FAR SOUTHWESTERN CWA WHERE MORE SUN CAN BE
EXPECTED.

LOW CONFIDENCE IN THE EXTENT OF LAKE CLOUDINESS TONIGHT...WHICH
WOULD PLAY A ROLE IN LOW TEMPS. MORE CLOUDS NEAR THE LAKE WOULD
RESULT IN LOWS A COUPLE DEGREES WARMER THAN CURRENTLY FORECAST AND
VICE VERSA IF MAINLY CLEAR. SUNNY SKIES ARE EXPECTED WEDNESDAY AS
TRANSIENT UPPER RIDGE BUILDS INTO THE AREA BETWEEN DEPARTING DEEP
UPPER TROUGH/LOW AND THE NEXT STRONG NORTHERN STREAM SHORTWAVE
SLATED TO ARRIVE IN OUR AREA LATER THURSDAY. NOT LOOKING FOR MUCH OF
A CHANCE OF SUBSTANTIAL WARMING WEDNESDAY WITH A STILL SOMEWHAT COOL
EASTERLY LOW LEVEL FLOW AND ONLY WEAK LOW LEVEL WARM AIR ADVECTION.

BY THURSDAY SHOWER CHANCES WILL BE ON THE INCREASE AS SHARP NORTHERN
STREAM TROUGH TRACKS SOUTHEAST INTO THE WESTERN LAKES. LACK OF
RETURN FLOW SHOULD RESULT IN LIMITED MOISTURE FOR THE SYSTEM...BUT
FAIRLY STRONG FORCING SHOULD ALLOW FOR A PERIOD OF SHOWERS ACROSS
THE CWA THURSDAY AFTERNOON OR EVENING. NOT MUCH COOLING BEHIND THIS
SYSTEM FRIDAY...THEN A FAST MOVING WEAK CANADIAN COLD FRONT SHOULD
BRING A BRIEF COOL DOWN SATURDAY BEFORE MORE SUBSTANTIAL WARM AIR
ADVECTION SUNDAY INTO MONDAY LIKELY SENDS TEMPERATURES NEAR IF NOT
INTO THE 70S ACROSS THE CWA. MEDIUM RANGE MODELS DO SHOW A
PROGRESSIVE LONG WAVE TROUGH MOVING ACROSS THE CONUS BY EARLY NEXT
WEEK WITH COLD FRONT LIKELY TO ARRIVE LATER MONDAY OR TUESDAY
BRINGING AN END TO OUR BRIEF BUT POTENTIALLY IMPRESSIVE WARM UP.

IZZI

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KT AND GUSTY THROUGH EARLY EVENING.

* MVFR CEILINGS POSSIBLE THROUGH AFTERNOON.

RODRIGUEZ

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

DESPITE HIGH PRESSURE BUILDING ACROSS THE REGION TODAY...CEILINGS
HAVE STILL DEVELOPED WHILE LAKE EFFECT CLOUD COVER CONTINUES TO
MOVE OVERHEAD. THESE BOTH WILL SCATTER/DIMINISH THROUGH THIS
EVENING AS THIS HIGH BUILDS ACROSS THE TERMINALS. BEFORE THIS
OCCURS...PERIODS OF HIGH END MVFR CEILINGS WILL STILL BE POSSIBLE.
THEN EXPECT DRY AND MOSTLY CLEAR SKIES THROUGH THE REST OF THE
FORECAST PERIOD. NORTHEAST WINDS/GUSTS WILL PREVAIL THIS AFTERNOON
BEFORE DIMINISHING LATER THIS EVENING...AND THEN REMAIN MORE
EASTERLY AND UNDER 10 KT EARLY WEDNESDAY MORNING THROUGH THE REST
OF THE FORECAST PERIOD.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE WITH MVFR CEILINGS...MEDIUM CONFIDENCE OF
  DURATION.

RODRIGUEZ

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

258 AM...LOW PRESSURE NEAR LAKE ONTARIO WILL MOVE OFF THE MID
ATLANTIC COAST WEDNESDAY MORNING THEN DEEPEN AGAIN AS IT MOVES
NORTHEAST ALONG THE NEW ENGLAND COAST WEDNESDAY NIGHT THROUGH
THURSDAY NIGHT. HIGH PRESSURE OVER ONTARIO WILL STRENGTHEN AS IT
MOVES INTO QUEBEC TONIGHT AND WEDNESDAY...WITH A TRAILING WEAKER
RIDGE BUILDING ACROSS THE WESTERN LAKES TODAY AND CROSSING LAKE
MICHIGAN TONIGHT. NORTH WINDS ARE STILL EXPECTED TO INCREASE TO
30 KT WITH A TIGHT GRADIENT BETWEEN THE APPROACHING RIDGE AND THE
DEPARTING LOW BUT SPEEDS WILL PROBABLY DIMINISH A LITTLE FASTER
THAN PREVIOUSLY INDICATED LATE THIS AFTERNOON INTO THIS EVENING.
THE RIDGE WILL BECOME STATIONARY OVER THE EASTERN LAKES WEDNESDAY
NIGHT AND THURSDAY AS IT WEAKENS. CMS

&&

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

&&

$$

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

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







000
FXUS63 KLOT 211622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1122 AM CDT TUE OCT 21 2014

.DISCUSSION...
218 AM CDT

BELOW AVERAGE TEMPERATURES THE NEXT COUPLE OF DAYS WILL GRADUALLY
GIVE WAY TO A BOUT OF INDIAN SUMMER OVER THE WEEKEND.

WATER VAPOR IMAGERY SHOWS AN AMPLIFYING UPPER TROUGH OVER THE
EASTERN CONUS THIS MORNING WITH LAST EVENING`S UPPER AIR ANALYSIS
SHOWING A POCKET OF SUB-FREEZING 850MB TEMPS ADVECTING SOUTH INTO
THE WESTERN GREAT LAKES REGION. THE CHILLY AIR MOVING OVER THE
RELATIVELY MILDER LAKE WATER IS CURRENTLY RESULTING IN A MARGINAL
LAKE EFFECT SHOWER SET-UP WITH SCATTERED LIGHT SHOWERS OR SPRINKLES
SHOWING UP OVER SOUTHERN LM INTO NW IN. LOW LEVEL FLOW WILL VEER TO
MORE NORTHEASTERLY DIRECTION TODAY AND SEND SOME OF THE LAKE EFFECT
CLOUDINESS AND POTENTIALLY SPRINKLES/LIGHT SHOWERS INTO EXTREME NE
IL THIS MORNING. RELATIVELY LOW INVERSION HEIGHTS AND SOMEWHAT WEAK
INSTABILITY MAKE THE CHANCES OF MEASURABLE PRECIP LOW AND HAVE KEPT
POPS IN THE LOWER END OF THE CHANCE CATEGORY. CLOUDINESS SHOULD BE
MOST PREVALENT TODAY NEAR THE LAKE WITH BETTER INCREASINGLY SUNNY
SKIES WELL INLAND. CLOUD COVER SHOULD KEEP HIGHS STRUGGLING INTO THE
LOWER 50S IN NE IL WHILE MID OR EVEN UPPER 50S ARE POSSIBLE OUT
TOWARD MENDOTA AND FAR SOUTHWESTERN CWA WHERE MORE SUN CAN BE
EXPECTED.

LOW CONFIDENCE IN THE EXTENT OF LAKE CLOUDINESS TONIGHT...WHICH
WOULD PLAY A ROLE IN LOW TEMPS. MORE CLOUDS NEAR THE LAKE WOULD
RESULT IN LOWS A COUPLE DEGREES WARMER THAN CURRENTLY FORECAST AND
VICE VERSA IF MAINLY CLEAR. SUNNY SKIES ARE EXPECTED WEDNESDAY AS
TRANSIENT UPPER RIDGE BUILDS INTO THE AREA BETWEEN DEPARTING DEEP
UPPER TROUGH/LOW AND THE NEXT STRONG NORTHERN STREAM SHORTWAVE
SLATED TO ARRIVE IN OUR AREA LATER THURSDAY. NOT LOOKING FOR MUCH OF
A CHANCE OF SUBSTANTIAL WARMING WEDNESDAY WITH A STILL SOMEWHAT COOL
EASTERLY LOW LEVEL FLOW AND ONLY WEAK LOW LEVEL WARM AIR ADVECTION.

BY THURSDAY SHOWER CHANCES WILL BE ON THE INCREASE AS SHARP NORTHERN
STREAM TROUGH TRACKS SOUTHEAST INTO THE WESTERN LAKES. LACK OF
RETURN FLOW SHOULD RESULT IN LIMITED MOISTURE FOR THE SYSTEM...BUT
FAIRLY STRONG FORCING SHOULD ALLOW FOR A PERIOD OF SHOWERS ACROSS
THE CWA THURSDAY AFTERNOON OR EVENING. NOT MUCH COOLING BEHIND THIS
SYSTEM FRIDAY...THEN A FAST MOVING WEAK CANADIAN COLD FRONT SHOULD
BRING A BRIEF COOL DOWN SATURDAY BEFORE MORE SUBSTANTIAL WARM AIR
ADVECTION SUNDAY INTO MONDAY LIKELY SENDS TEMPERATURES NEAR IF NOT
INTO THE 70S ACROSS THE CWA. MEDIUM RANGE MODELS DO SHOW A
PROGRESSIVE LONG WAVE TROUGH MOVING ACROSS THE CONUS BY EARLY NEXT
WEEK WITH COLD FRONT LIKELY TO ARRIVE LATER MONDAY OR TUESDAY
BRINGING AN END TO OUR BRIEF BUT POTENTIALLY IMPRESSIVE WARM UP.

IZZI

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KTS AND GUSTY THRU LATE AFTERNOON.

* SLIGHT CHANCE FOR -SHRA THRU MID AFTERNOON.

* MVFR CEILINGS THRU AFTERNOON.

RODRIGUEZ

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

NO SIGNIFICANT CHANGES TO PREVIOUS FORECAST. NORTHERLY WINDS WILL
INCREASE TO 10-14KTS IN THE NEXT FEW HOURS AND TURN MORE TO THE
NORTHEAST THIS MORNING AND THIS AFTERNOON. GUSTS INTO THE 16-20KT
RANGE WILL ALSO DEVELOP MID MORNING AND CONTINUE INTO THE
AFTERNOON. WINDS WILL QUICKLY DIMINISH BY EARLY EVENING AND TURN
MORE EAST/NORTHEAST TONIGHT.

LAKE EFFECT RAIN SHOWERS CONTINUE TO MOVE SOUTH INTO NORTHWEST
INDIANA AND WILL AFFECT GYY AT TIMES THIS MORNING. AS THE WINDS
TURN MORE NORTHEAST...THESE SHOWERS MAY MOVE FAR ENOUGH INLAND TO
REACH ORD/MDW. HOWEVER...HAVE MAINTAINED A DRY FORECAST GIVEN THE
EXPECTED SHORT DURATION AND ISOLATED COVERAGE.

4-5KFT VFR CIGS WILL LOWER TO MVFR MID/LATE MORNING...WITH MVFR
CIGS ACROSS EASTERN WI AND SPREADING SOUTH. TIMING AND DURATION
WILL LIKELY NEED TO BE ADJUSTED WITH MORNING UPDATES. CMS

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

* HIGH CONFIDENCE FOR WIND SPEEDS/GUSTS/DIRECTIONS THRU THE
  PERIOD.

* MEDIUM CONFIDENCE FOR SHRA THRU MID AFTERNOON.

* HIGH CONFIDENCE FOR MVFR CEILINGS...MEDIUM CONFIDENCE OF
  DURATION.

RODRIGUEZ

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

258 AM...LOW PRESSURE NEAR LAKE ONTARIO WILL MOVE OFF THE MID
ATLANTIC COAST WEDNESDAY MORNING THEN DEEPEN AGAIN AS IT MOVES
NORTHEAST ALONG THE NEW ENGLAND COAST WEDNESDAY NIGHT THROUGH
THURSDAY NIGHT. HIGH PRESSURE OVER ONTARIO WILL STRENGTHEN AS IT
MOVES INTO QUEBEC TONIGHT AND WEDNESDAY...WITH A TRAILING WEAKER
RIDGE BUILDING ACROSS THE WESTERN LAKES TODAY AND CROSSING LAKE
MICHIGAN TONIGHT. NORTH WINDS ARE STILL EXPECTED TO INCREASE TO
30 KT WITH A TIGHT GRADIENT BETWEEN THE APPROACHING RIDGE AND THE
DEPARTING LOW BUT SPEEDS WILL PROBABLY DIMINISH A LITTLE FASTER
THAN PREVIOUSLY INDICATED LATE THIS AFTERNOON INTO THIS EVENING.
THE RIDGE WILL BECOME STATIONARY OVER THE EASTERN LAKES WEDNESDAY
NIGHT AND THURSDAY AS IT WEAKENS. CMS

&&

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

&&

$$

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

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







000
FXUS63 KLOT 211622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1122 AM CDT TUE OCT 21 2014

.DISCUSSION...
218 AM CDT

BELOW AVERAGE TEMPERATURES THE NEXT COUPLE OF DAYS WILL GRADUALLY
GIVE WAY TO A BOUT OF INDIAN SUMMER OVER THE WEEKEND.

WATER VAPOR IMAGERY SHOWS AN AMPLIFYING UPPER TROUGH OVER THE
EASTERN CONUS THIS MORNING WITH LAST EVENING`S UPPER AIR ANALYSIS
SHOWING A POCKET OF SUB-FREEZING 850MB TEMPS ADVECTING SOUTH INTO
THE WESTERN GREAT LAKES REGION. THE CHILLY AIR MOVING OVER THE
RELATIVELY MILDER LAKE WATER IS CURRENTLY RESULTING IN A MARGINAL
LAKE EFFECT SHOWER SET-UP WITH SCATTERED LIGHT SHOWERS OR SPRINKLES
SHOWING UP OVER SOUTHERN LM INTO NW IN. LOW LEVEL FLOW WILL VEER TO
MORE NORTHEASTERLY DIRECTION TODAY AND SEND SOME OF THE LAKE EFFECT
CLOUDINESS AND POTENTIALLY SPRINKLES/LIGHT SHOWERS INTO EXTREME NE
IL THIS MORNING. RELATIVELY LOW INVERSION HEIGHTS AND SOMEWHAT WEAK
INSTABILITY MAKE THE CHANCES OF MEASURABLE PRECIP LOW AND HAVE KEPT
POPS IN THE LOWER END OF THE CHANCE CATEGORY. CLOUDINESS SHOULD BE
MOST PREVALENT TODAY NEAR THE LAKE WITH BETTER INCREASINGLY SUNNY
SKIES WELL INLAND. CLOUD COVER SHOULD KEEP HIGHS STRUGGLING INTO THE
LOWER 50S IN NE IL WHILE MID OR EVEN UPPER 50S ARE POSSIBLE OUT
TOWARD MENDOTA AND FAR SOUTHWESTERN CWA WHERE MORE SUN CAN BE
EXPECTED.

LOW CONFIDENCE IN THE EXTENT OF LAKE CLOUDINESS TONIGHT...WHICH
WOULD PLAY A ROLE IN LOW TEMPS. MORE CLOUDS NEAR THE LAKE WOULD
RESULT IN LOWS A COUPLE DEGREES WARMER THAN CURRENTLY FORECAST AND
VICE VERSA IF MAINLY CLEAR. SUNNY SKIES ARE EXPECTED WEDNESDAY AS
TRANSIENT UPPER RIDGE BUILDS INTO THE AREA BETWEEN DEPARTING DEEP
UPPER TROUGH/LOW AND THE NEXT STRONG NORTHERN STREAM SHORTWAVE
SLATED TO ARRIVE IN OUR AREA LATER THURSDAY. NOT LOOKING FOR MUCH OF
A CHANCE OF SUBSTANTIAL WARMING WEDNESDAY WITH A STILL SOMEWHAT COOL
EASTERLY LOW LEVEL FLOW AND ONLY WEAK LOW LEVEL WARM AIR ADVECTION.

BY THURSDAY SHOWER CHANCES WILL BE ON THE INCREASE AS SHARP NORTHERN
STREAM TROUGH TRACKS SOUTHEAST INTO THE WESTERN LAKES. LACK OF
RETURN FLOW SHOULD RESULT IN LIMITED MOISTURE FOR THE SYSTEM...BUT
FAIRLY STRONG FORCING SHOULD ALLOW FOR A PERIOD OF SHOWERS ACROSS
THE CWA THURSDAY AFTERNOON OR EVENING. NOT MUCH COOLING BEHIND THIS
SYSTEM FRIDAY...THEN A FAST MOVING WEAK CANADIAN COLD FRONT SHOULD
BRING A BRIEF COOL DOWN SATURDAY BEFORE MORE SUBSTANTIAL WARM AIR
ADVECTION SUNDAY INTO MONDAY LIKELY SENDS TEMPERATURES NEAR IF NOT
INTO THE 70S ACROSS THE CWA. MEDIUM RANGE MODELS DO SHOW A
PROGRESSIVE LONG WAVE TROUGH MOVING ACROSS THE CONUS BY EARLY NEXT
WEEK WITH COLD FRONT LIKELY TO ARRIVE LATER MONDAY OR TUESDAY
BRINGING AN END TO OUR BRIEF BUT POTENTIALLY IMPRESSIVE WARM UP.

IZZI

&&

.AVIATION...

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

* NORTH/NORTHEAST WINDS 10-14 KTS AND GUSTY THRU LATE AFTERNOON.

* SLIGHT CHANCE FOR -SHRA THRU MID AFTERNOON.

* MVFR CEILINGS THRU AFTERNOON.

RODRIGUEZ

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

NO SIGNIFICANT CHANGES TO PREVIOUS FORECAST. NORTHERLY WINDS WILL
INCREASE TO 10-14KTS IN THE NEXT FEW HOURS AND TURN MORE TO THE
NORTHEAST THIS MORNING AND THIS AFTERNOON. GUSTS INTO THE 16-20KT
RANGE WILL ALSO DEVELOP MID MORNING AND CONTINUE INTO THE
AFTERNOON. WINDS WILL QUICKLY DIMINISH BY EARLY EVENING AND TURN
MORE EAST/NORTHEAST TONIGHT.

LAKE EFFECT RAIN SHOWERS CONTINUE TO MOVE SOUTH INTO NORTHWEST
INDIANA AND WILL AFFECT GYY AT TIMES THIS MORNING. AS THE WINDS
TURN MORE NORTHEAST...THESE SHOWERS MAY MOVE FAR ENOUGH INLAND TO
REACH ORD/MDW. HOWEVER...HAVE MAINTAINED A DRY FORECAST GIVEN THE
EXPECTED SHORT DURATION AND ISOLATED COVERAGE.

4-5KFT VFR CIGS WILL LOWER TO MVFR MID/LATE MORNING...WITH MVFR
CIGS ACROSS EASTERN WI AND SPREADING SOUTH. TIMING AND DURATION
WILL LIKELY NEED TO BE ADJUSTED WITH MORNING UPDATES. CMS

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

* HIGH CONFIDENCE FOR WIND SPEEDS/GUSTS/DIRECTIONS THRU THE
  PERIOD.

* MEDIUM CONFIDENCE FOR SHRA THRU MID AFTERNOON.

* HIGH CONFIDENCE FOR MVFR CEILINGS...MEDIUM CONFIDENCE OF
  DURATION.

RODRIGUEZ

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

* WEDNESDAY NIGHT...DRY/VFR.
* THURSDAY...CHANCE OF SHRA. SOUTH WINDS.
* FRIDAY AND SATURDAY...DRY/VFR. WEST/SOUTHWEST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.

&&

.MARINE...

258 AM...LOW PRESSURE NEAR LAKE ONTARIO WILL MOVE OFF THE MID
ATLANTIC COAST WEDNESDAY MORNING THEN DEEPEN AGAIN AS IT MOVES
NORTHEAST ALONG THE NEW ENGLAND COAST WEDNESDAY NIGHT THROUGH
THURSDAY NIGHT. HIGH PRESSURE OVER ONTARIO WILL STRENGTHEN AS IT
MOVES INTO QUEBEC TONIGHT AND WEDNESDAY...WITH A TRAILING WEAKER
RIDGE BUILDING ACROSS THE WESTERN LAKES TODAY AND CROSSING LAKE
MICHIGAN TONIGHT. NORTH WINDS ARE STILL EXPECTED TO INCREASE TO
30 KT WITH A TIGHT GRADIENT BETWEEN THE APPROACHING RIDGE AND THE
DEPARTING LOW BUT SPEEDS WILL PROBABLY DIMINISH A LITTLE FASTER
THAN PREVIOUSLY INDICATED LATE THIS AFTERNOON INTO THIS EVENING.
THE RIDGE WILL BECOME STATIONARY OVER THE EASTERN LAKES WEDNESDAY
NIGHT AND THURSDAY AS IT WEAKENS. CMS

&&

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

&&

$$

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

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






    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