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000
FXUS63 KLOT 252201
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
401 PM CST TUE NOV 25 2014

.SHORT TERM...
231 PM CST

TONIGHT THROUGH WEDNESDAY...
TEMPERATURE INVERSION HAS BEEN ABLE TO HOLD ONTO THE CLOUDS...WITH
A STUBBORN STRATUS LAYER. FORTUNATELY THIS WEDGE OF CLOUDS WAS
SLOWLY SLIDING EAST THIS AFTERNOON...WITH SOME CLEARING TAKING
PLACE ACROSS WESTERN IL AND STRETCHING FURTHER WEST. SFC RIDGE WAS
PUSHING EAST INTO SOUTHERN MO/NORTHERN AR...WHICH PLACED THE
FORECAST AREA IN THE WESTERLY FLOW AT THE SFC. THERE IS SOME
POTENTIAL THAT PATCHY FOG MAY DEVELOP TONIGHT...GIVEN THE SLOWLY
ERODING CLOUD COVER AND DEW POINTS NOT ABLE TO DRY THIS AFTN. THIS
CURRENTLY IS A LOW CONFIDENCE SCENARIO...BUT FELT IT WAS WORTH
MENTIONING. WITH SOME CLEARING LIKELY TO TAKE PLACE IN THE WESTERN
CWFA...TEMPS SHUD LIKELY BE ABLE TO RADIATE INTO THE LOW TEENS
THERE. ELSEWHERE OVERNIGHT LOWS WILL HOVER ARND 18-22.

SFC RIDGE FOR WED WILL STRETCH FROM THE WESTERN GULF NORTH INTO
LOWER MICHIGAN...AND LIKELY BE SLOW TO DEPART THE REGION. THIS HAS
BEEN IMPACTING THE PLACEMENT/MOISTURE WITHIN A WEAK SHORTWAVE DIVING
SOUTHEAST ACROSS THE UPPER MIDWEST FOR WED. GUIDANCE HAS CONTINUED
TO DEMONSTRATE LESS FAVORABLE SETUP FOR LGT SNOW AND ALSO TIMING FOR
LATER WED. HI-RES LOCAL SOLUTION EVEN SUGGESTS FLURRIES LATE WED
AFTN MAY BE THE EXTENT OF ANY PRECIP. WITH AT LEAST SOME
HIGH/MID-LVL CLOUDS...TEMPS MAY AGAIN BE A CHALLENGE. CURRENT
SOLUTIONS POINT TOWARDS HIGHS WARMING INTO THE LOW/MID 30S...BUT
COULD SEE TEMPS STRUGGLING TO WARM BEYOND THE LOW 30S.

WITH THE MID-LVL TROUGH AXIS PIVOTING EAST ACROSS THE FORECAST AREA
WED EVE AND SOME WEAK OMEGA INTO THE MOIST LAYER...SOME LIGHT SNOW
COULD PRODUCE A DUSTING WED EVE BUT THE CONFIDENCE WITH THIS
SCENARIO CONTINUES TO DIMINISH. A FRONTAL BOUNDARY WILL THEN SLIDE
EAST ACROSS THE REGION WED NGT...WITH ANOTHER RIDGE OF HIGH PRESSURE
SLOWLY BUILDING IN FROM THE UPPER MIDWEST.

BEACHLER

&&

.LONG TERM...
231 PM CST

THANKSGIVING THROUGH TUESDAY...
500MB TROUGH WILL BE DEPARTING THE REGION FOR THANKSGIVING...WITH
BROAD SFC RIDGE BUILDING IN FROM THE WEST DURING THE DAY. THIS SHUD
PROVIDE A GRADUAL EROSION TO THE CLOUD COVER. TEMPS WILL HOVER IN
THE MID/UPR 20S...BUT IF CLOUDS CAN ERODE EARLIER THEN TEMPS MAY BE
ABLE TO WARM A DEGREE OR TWO HIGHER.

MID-LVL FLOW BEGINS TO TRANSITION INTO A SEMI-ZONAL SETUP...WITH THE
POTENTIAL FOR ANOTHER LOW PRESSURE SYSTEM BRINGING A CHC FOR LGT
SNOW FRI. ENSEMBLES CONTINUE TO SUGGEST THAT SAT COULD WARM WELL
INTO THE 40S...PERHAPS TOUCHING 50 DEGREES IN THE SOUTHERN CWFA. FOR
THE SECOND HALF OF THE WEEKEND GUIDANCE DIFFERS ON TIMING OF A
FRONTAL BOUNDARY. IF A SLOWER SOLUTIONS OCCURS...SUN COULD ALSO BE A
MILD DAY WITH HIGHS IN THE MID/UPR 40S.

GUIDANCE HAS BEEN SUGGESTING A NARROW BAROCLINIC ZONE MAY DEVELOP
ALONG THE OHIO VALLEY EARLY NEXT WEEK...WHICH COULD KEEP SOME LGT
PRECIP IN THE SOUTHEAST FORECAST AREA.

BEACHLER

&&

.AVIATION...

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

* PERIOD OF MVFR BKN CIG AROUND 2000 FT INTO THIS EVENING.

RATZER

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

SATELLITE TRENDS INDICATE BKN MVFR AROUND 2000 FT AGL WILL WORK
BACK INTO ORD...AND ALREADY ARE ACROSS DPA/GYY/MDW. MOISTURE IS
SHALLOW AND TRAPPED BELOW INVERSION BASED AT AROUND 900 MB OR 2500
FT AGL. TRAILING EDGE OF STRATUS/STRAOCU ACROSS CENTRAL IL SHOULD
CONTINUE TO ADVANCE TO THE EAST-NORTHEAST AND ALLOW FOR SCATTERING
TO VFR LATER THIS EVENING.

RATZER

PREVIOUS DISCUSSION FROM 20Z...


MVFR CIGS IN 1500 TO 2200 FOOT RANGE OVER SOUTH AND SOUTHWEST CHI
METRO HAVE TRIED TO LIFT NORTH A BIT WITH WEST SOUTHWEST FLOW
ALOFT AND AT THE SURFACE. NORTHERN EDGE IS RAGGED SO COULD SEE MDW
SCATTER AT TIMES AND HAVE NOT INCLUDED MVFR IN ORD TAF BUT WILL
NEED TO MONITOR TRENDS. HI-RES GUIDANCE FAVORS MVFR CIGS THIS
EVENING WHILE REST OF GUIDANCE INDICATES DRIER AIR MOVING IN
ALOFT. OVERALL HAVE LOWER CONFIDENCE IN CIG FORECAST THROUGH THIS
EVENING...THOUGH OTHERWISE NO SIGNFICIANT AVIATION CONCERNS.

RC

FROM 18Z...

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC

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

* MEDIUM-HIGH IN MVFR CIG TRENDS THROUGH EARLY EVENING.

RATZER

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
147 PM CST

A HIGH PRESSURE RIDGE CONTINUES TO PUSH EAST CAUSING WINDS TO
DIMINISH ACROSS THE REGION. MEANWHILE A LOW CURRENTLY OVER THE
DAKOTAS REACHES THE MID MISSISSIPPI VALLEY TOMORROW MORNING. LIGHT
WINDS BECOME EAST OVER THE SOUTHERN HALF OF THE LAKE AND VARIABLE
OVER THE NORTHERN HALF TOMORROW AFTERNOON.  THE LOW WEAKENS AS IT
PASSES OVER CENTRAL IL TOMORROW AND HIGH PRESSURE THEN BUILDS OVER
THE PLAINS TOMORROW NIGHT.  NORTH TO NORTHWEST WINDS INCREASE TO 30
KT THURSDAY AS THE PRESSURE GRADIENT INCREASES BETWEEN THE HIGH OVER
THE PLAINS AND LARGE LOW MOVING UP THE EAST COAST.  WINDS DIMINISH
AS THE HIGH MOVES OVER THE LAKE THURSDAY NIGHT.  WINDS THEN BECOME
SOUTH BEHIND THE HIGH FRIDAY.  GUIDANCE DIFFERS ON HOW QUICKLY THE
NEXT LOW MOVES OVER LAKE SUPERIOR...BUT THE PRESSURE GRADIENT
INCREASES AHEAD OF THE LOW RESULTING IN SOUTH WINDS AROUND 30 KT
LATE THIS WEEK. HAVE THE WINDS FORECASTED TO COME UP FRIDAY
AFTERNOON...BUT THEY COULD COME UP AS LATE AS SATURDAY MORNING. 20
KT WINDS PERSIST THROUGH THE WEEKEND WITH SOUTHWEST WINDS BECOMING
NORTH SUNDAY AFTERNOON.  ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE
LAKE EARLY NEXT WEEK WITH STRONG SOUTH WINDS BEHIND IT.

JEE

&&

.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 252032
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
232 PM CST TUE NOV 25 2014

.SHORT TERM...
231 PM CST

TONIGHT THROUGH WEDNESDAY...
TEMPERATURE INVERSION HAS BEEN ABLE TO HOLD ONTO THE CLOUDS...WITH
A STUBBORN STRATUS LAYER. FORTUNATELY THIS WEDGE OF CLOUDS WAS
SLOWLY SLIDING EAST THIS AFTERNOON...WITH SOME CLEARING TAKING
PLACE ACROSS WESTERN IL AND STRETCHING FURTHER WEST. SFC RIDGE WAS
PUSHING EAST INTO SOUTHERN MO/NORTHERN AR...WHICH PLACED THE
FORECAST AREA IN THE WESTERLY FLOW AT THE SFC. THERE IS SOME
POTENTIAL THAT PATCHY FOG MAY DEVELOP TONIGHT...GIVEN THE SLOWLY
ERODING CLOUD COVER AND DEW POINTS NOT ABLE TO DRY THIS AFTN. THIS
CURRENTLY IS A LOW CONFIDENCE SCENARIO...BUT FELT IT WAS WORTH
MENTIONING. WITH SOME CLEARING LIKELY TO TAKE PLACE IN THE WESTERN
CWFA...TEMPS SHUD LIKELY BE ABLE TO RADIATE INTO THE LOW TEENS
THERE. ELSEWHERE OVERNIGHT LOWS WILL HOVER ARND 18-22.

SFC RIDGE FOR WED WILL STRETCH FROM THE WESTERN GULF NORTH INTO
LOWER MICHIGAN...AND LIKELY BE SLOW TO DEPART THE REGION. THIS HAS
BEEN IMPACTING THE PLACEMENT/MOISTURE WITHIN A WEAK SHORTWAVE DIVING
SOUTHEAST ACROSS THE UPPER MIDWEST FOR WED. GUIDANCE HAS CONTINUED
TO DEMONSTRATE LESS FAVORABLE SETUP FOR LGT SNOW AND ALSO TIMING FOR
LATER WED. HI-RES LOCAL SOLUTION EVEN SUGGESTS FLURRIES LATE WED
AFTN MAY BE THE EXTENT OF ANY PRECIP. WITH AT LEAST SOME
HIGH/MID-LVL CLOUDS...TEMPS MAY AGAIN BE A CHALLENGE. CURRENT
SOLUTIONS POINT TOWARDS HIGHS WARMING INTO THE LOW/MID 30S...BUT
COULD SEE TEMPS STRUGGLING TO WARM BEYOND THE LOW 30S.

WITH THE MID-LVL TROUGH AXIS PIVOTING EAST ACROSS THE FORECAST AREA
WED EVE AND SOME WEAK OMEGA INTO THE MOIST LAYER...SOME LIGHT SNOW
COULD PRODUCE A DUSTING WED EVE BUT THE CONFIDENCE WITH THIS
SCENARIO CONTINUES TO DIMINISH. A FRONTAL BOUNDARY WILL THEN SLIDE
EAST ACROSS THE REGION WED NGT...WITH ANOTHER RIDGE OF HIGH PRESSURE
SLOWLY BUILDING IN FROM THE UPPER MIDWEST.

BEACHLER

&&

.LONG TERM...
231 PM CST

THANKSGIVING THROUGH TUESDAY...
500MB TROUGH WILL BE DEPARTING THE REGION FOR THANKSGIVING...WITH
BROAD SFC RIDGE BUILDING IN FROM THE WEST DURING THE DAY. THIS SHUD
PROVIDE A GRADUAL EROSION TO THE CLOUD COVER. TEMPS WILL HOVER IN
THE MID/UPR 20S...BUT IF CLOUDS CAN ERODE EARLIER THEN TEMPS MAY BE
ABLE TO WARM A DEGREE OR TWO HIGHER.

MID-LVL FLOW BEGINS TO TRANSITION INTO A SEMI-ZONAL SETUP...WITH THE
POTENTIAL FOR ANOTHER LOW PRESSURE SYSTEM BRINGING A CHC FOR LGT
SNOW FRI. ENSEMBLES CONTINUE TO SUGGEST THAT SAT COULD WARM WELL
INTO THE 40S...PERHAPS TOUCHING 50 DEGREES IN THE SOUTHERN CWFA. FOR
THE SECOND HALF OF THE WEEKEND GUIDANCE DIFFERS ON TIMING OF A
FRONTAL BOUNDARY. IF A SLOWER SOLUTIONS OCCURS...SUN COULD ALSO BE A
MILD DAY WITH HIGHS IN THE MID/UPR 40S.

GUIDANCE HAS BEEN SUGGESTING A NARROW BAROCLINIC ZONE MAY DEVELOP
ALONG THE OHIO VALLEY EARLY NEXT WEEK...WHICH COULD KEEP SOME LGT
PRECIP IN THE SOUTHEAST FORECAST AREA.

BEACHLER

&&

.AVIATION...

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

* MID RANGE MVFR CIGS AT MDW AND POSSIBLY ORD INTO LATE AFTERNOON.

RC

//DISCUSSION...UPDATED 20Z...

MVFR CIGS IN 1500 TO 2200 FOOT RANGE OVER SOUTH AND SOUTHWEST CHI
METRO HAVE TRIED TO LIFT NORTH A BIT WITH WEST SOUTHWEST FLOW
ALOFT AND AT THE SURFACE. NORTHERN EDGE IS RAGGED SO COULD SEE MDW
SCATTER AT TIMES AND HAVE NOT INCLUDED MVFR IN ORD TAF BUT WILL
NEED TO MONITOR TRENDS. HI-RES GUIDANCE FAVORS MVFR CIGS THIS
EVENING WHILE REST OF GUIDANCE INDICATES DRIER AIR MOVING IN
ALOFT. OVERALL HAVE LOWER CONFIDENCE IN CIG FORECAST THROUGH THIS
EVENING...THOUGH OTHERWISE NO SIGNFICIANT AVIATION CONCERNS.

FROM 18Z...

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC

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

* LOW IN MVFR CIG TRENDS.

RC

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
147 PM CST

A HIGH PRESSURE RIDGE CONTINUES TO PUSH EAST CAUSING WINDS TO
DIMINISH ACROSS THE REGION. MEANWHILE A LOW CURRENTLY OVER THE
DAKOTAS REACHES THE MID MISSISSIPPI VALLEY TOMORROW MORNING. LIGHT
WINDS BECOME EAST OVER THE SOUTHERN HALF OF THE LAKE AND VARIABLE
OVER THE NORTHERN HALF TOMORROW AFTERNOON.  THE LOW WEAKENS AS IT
PASSES OVER CENTRAL IL TOMORROW AND HIGH PRESSURE THEN BUILDS OVER
THE PLAINS TOMORROW NIGHT.  NORTH TO NORTHWEST WINDS INCREASE TO 30
KT THURSDAY AS THE PRESSURE GRADIENT INCREASES BETWEEN THE HIGH OVER
THE PLAINS AND LARGE LOW MOVING UP THE EAST COAST.  WINDS DIMINISH
AS THE HIGH MOVES OVER THE LAKE THURSDAY NIGHT.  WINDS THEN BECOME
SOUTH BEHIND THE HIGH FRIDAY.  GUIDANCE DIFFERS ON HOW QUICKLY THE
NEXT LOW MOVES OVER LAKE SUPERIOR...BUT THE PRESSURE GRADIENT
INCREASES AHEAD OF THE LOW RESULTING IN SOUTH WINDS AROUND 30 KT
LATE THIS WEEK. HAVE THE WINDS FORECASTED TO COME UP FRIDAY
AFTERNOON...BUT THEY COULD COME UP AS LATE AS SATURDAY MORNING. 20
KT WINDS PERSIST THROUGH THE WEEKEND WITH SOUTHWEST WINDS BECOMING
NORTH SUNDAY AFTERNOON.  ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE
LAKE EARLY NEXT WEEK WITH STRONG SOUTH WINDS BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

&&

$$

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 252032
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
232 PM CST TUE NOV 25 2014

.SHORT TERM...
231 PM CST

TONIGHT THROUGH WEDNESDAY...
TEMPERATURE INVERSION HAS BEEN ABLE TO HOLD ONTO THE CLOUDS...WITH
A STUBBORN STRATUS LAYER. FORTUNATELY THIS WEDGE OF CLOUDS WAS
SLOWLY SLIDING EAST THIS AFTERNOON...WITH SOME CLEARING TAKING
PLACE ACROSS WESTERN IL AND STRETCHING FURTHER WEST. SFC RIDGE WAS
PUSHING EAST INTO SOUTHERN MO/NORTHERN AR...WHICH PLACED THE
FORECAST AREA IN THE WESTERLY FLOW AT THE SFC. THERE IS SOME
POTENTIAL THAT PATCHY FOG MAY DEVELOP TONIGHT...GIVEN THE SLOWLY
ERODING CLOUD COVER AND DEW POINTS NOT ABLE TO DRY THIS AFTN. THIS
CURRENTLY IS A LOW CONFIDENCE SCENARIO...BUT FELT IT WAS WORTH
MENTIONING. WITH SOME CLEARING LIKELY TO TAKE PLACE IN THE WESTERN
CWFA...TEMPS SHUD LIKELY BE ABLE TO RADIATE INTO THE LOW TEENS
THERE. ELSEWHERE OVERNIGHT LOWS WILL HOVER ARND 18-22.

SFC RIDGE FOR WED WILL STRETCH FROM THE WESTERN GULF NORTH INTO
LOWER MICHIGAN...AND LIKELY BE SLOW TO DEPART THE REGION. THIS HAS
BEEN IMPACTING THE PLACEMENT/MOISTURE WITHIN A WEAK SHORTWAVE DIVING
SOUTHEAST ACROSS THE UPPER MIDWEST FOR WED. GUIDANCE HAS CONTINUED
TO DEMONSTRATE LESS FAVORABLE SETUP FOR LGT SNOW AND ALSO TIMING FOR
LATER WED. HI-RES LOCAL SOLUTION EVEN SUGGESTS FLURRIES LATE WED
AFTN MAY BE THE EXTENT OF ANY PRECIP. WITH AT LEAST SOME
HIGH/MID-LVL CLOUDS...TEMPS MAY AGAIN BE A CHALLENGE. CURRENT
SOLUTIONS POINT TOWARDS HIGHS WARMING INTO THE LOW/MID 30S...BUT
COULD SEE TEMPS STRUGGLING TO WARM BEYOND THE LOW 30S.

WITH THE MID-LVL TROUGH AXIS PIVOTING EAST ACROSS THE FORECAST AREA
WED EVE AND SOME WEAK OMEGA INTO THE MOIST LAYER...SOME LIGHT SNOW
COULD PRODUCE A DUSTING WED EVE BUT THE CONFIDENCE WITH THIS
SCENARIO CONTINUES TO DIMINISH. A FRONTAL BOUNDARY WILL THEN SLIDE
EAST ACROSS THE REGION WED NGT...WITH ANOTHER RIDGE OF HIGH PRESSURE
SLOWLY BUILDING IN FROM THE UPPER MIDWEST.

BEACHLER

&&

.LONG TERM...
231 PM CST

THANKSGIVING THROUGH TUESDAY...
500MB TROUGH WILL BE DEPARTING THE REGION FOR THANKSGIVING...WITH
BROAD SFC RIDGE BUILDING IN FROM THE WEST DURING THE DAY. THIS SHUD
PROVIDE A GRADUAL EROSION TO THE CLOUD COVER. TEMPS WILL HOVER IN
THE MID/UPR 20S...BUT IF CLOUDS CAN ERODE EARLIER THEN TEMPS MAY BE
ABLE TO WARM A DEGREE OR TWO HIGHER.

MID-LVL FLOW BEGINS TO TRANSITION INTO A SEMI-ZONAL SETUP...WITH THE
POTENTIAL FOR ANOTHER LOW PRESSURE SYSTEM BRINGING A CHC FOR LGT
SNOW FRI. ENSEMBLES CONTINUE TO SUGGEST THAT SAT COULD WARM WELL
INTO THE 40S...PERHAPS TOUCHING 50 DEGREES IN THE SOUTHERN CWFA. FOR
THE SECOND HALF OF THE WEEKEND GUIDANCE DIFFERS ON TIMING OF A
FRONTAL BOUNDARY. IF A SLOWER SOLUTIONS OCCURS...SUN COULD ALSO BE A
MILD DAY WITH HIGHS IN THE MID/UPR 40S.

GUIDANCE HAS BEEN SUGGESTING A NARROW BAROCLINIC ZONE MAY DEVELOP
ALONG THE OHIO VALLEY EARLY NEXT WEEK...WHICH COULD KEEP SOME LGT
PRECIP IN THE SOUTHEAST FORECAST AREA.

BEACHLER

&&

.AVIATION...

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

* MID RANGE MVFR CIGS AT MDW AND POSSIBLY ORD INTO LATE AFTERNOON.

RC

//DISCUSSION...UPDATED 20Z...

MVFR CIGS IN 1500 TO 2200 FOOT RANGE OVER SOUTH AND SOUTHWEST CHI
METRO HAVE TRIED TO LIFT NORTH A BIT WITH WEST SOUTHWEST FLOW
ALOFT AND AT THE SURFACE. NORTHERN EDGE IS RAGGED SO COULD SEE MDW
SCATTER AT TIMES AND HAVE NOT INCLUDED MVFR IN ORD TAF BUT WILL
NEED TO MONITOR TRENDS. HI-RES GUIDANCE FAVORS MVFR CIGS THIS
EVENING WHILE REST OF GUIDANCE INDICATES DRIER AIR MOVING IN
ALOFT. OVERALL HAVE LOWER CONFIDENCE IN CIG FORECAST THROUGH THIS
EVENING...THOUGH OTHERWISE NO SIGNFICIANT AVIATION CONCERNS.

FROM 18Z...

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC

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

* LOW IN MVFR CIG TRENDS.

RC

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
147 PM CST

A HIGH PRESSURE RIDGE CONTINUES TO PUSH EAST CAUSING WINDS TO
DIMINISH ACROSS THE REGION. MEANWHILE A LOW CURRENTLY OVER THE
DAKOTAS REACHES THE MID MISSISSIPPI VALLEY TOMORROW MORNING. LIGHT
WINDS BECOME EAST OVER THE SOUTHERN HALF OF THE LAKE AND VARIABLE
OVER THE NORTHERN HALF TOMORROW AFTERNOON.  THE LOW WEAKENS AS IT
PASSES OVER CENTRAL IL TOMORROW AND HIGH PRESSURE THEN BUILDS OVER
THE PLAINS TOMORROW NIGHT.  NORTH TO NORTHWEST WINDS INCREASE TO 30
KT THURSDAY AS THE PRESSURE GRADIENT INCREASES BETWEEN THE HIGH OVER
THE PLAINS AND LARGE LOW MOVING UP THE EAST COAST.  WINDS DIMINISH
AS THE HIGH MOVES OVER THE LAKE THURSDAY NIGHT.  WINDS THEN BECOME
SOUTH BEHIND THE HIGH FRIDAY.  GUIDANCE DIFFERS ON HOW QUICKLY THE
NEXT LOW MOVES OVER LAKE SUPERIOR...BUT THE PRESSURE GRADIENT
INCREASES AHEAD OF THE LOW RESULTING IN SOUTH WINDS AROUND 30 KT
LATE THIS WEEK. HAVE THE WINDS FORECASTED TO COME UP FRIDAY
AFTERNOON...BUT THEY COULD COME UP AS LATE AS SATURDAY MORNING. 20
KT WINDS PERSIST THROUGH THE WEEKEND WITH SOUTHWEST WINDS BECOMING
NORTH SUNDAY AFTERNOON.  ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE
LAKE EARLY NEXT WEEK WITH STRONG SOUTH WINDS BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

&&

$$

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 252003
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
203 PM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* MID RANGE MVFR CIGS AT MDW AND POSSIBLY ORD INTO LATE AFTERNOON.

RC

//DISCUSSION...UPDATED 20Z...

MVFR CIGS IN 1500 TO 2200 FOOT RANGE OVER SOUTH AND SOUTHWEST CHI
METRO HAVE TRIED TO LIFT NORTH A BIT WITH WEST SOUTHWEST FLOW
ALOFT AND AT THE SURFACE. NORTHERN EDGE IS RAGGED SO COULD SEE MDW
SCATTER AT TIMES AND HAVE NOT INCLUDED MVFR IN ORD TAF BUT WILL
NEED TO MONITOR TRENDS. HI-RES GUIDANCE FAVORS MVFR CIGS THIS
EVENING WHILE REST OF GUIDANCE INDICATES DRIER AIR MOVING IN
ALOFT. OVERALL HAVE LOWER CONFIDENCE IN CIG FORECAST THROUGH THIS
EVENING...THOUGH OTHERWISE NO SIGNFICIANT AVIATION CONCERNS.

FROM 18Z...

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC

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

* LOW IN MVFR CIG TRENDS.

RC

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
147 PM CST

A HIGH PRESSURE RIDGE CONTINUES TO PUSH EAST CAUSING WINDS TO
DIMINISH ACROSS THE REGION. MEANWHILE A LOW CURRENTLY OVER THE
DAKOTAS REACHES THE MID MISSISSIPPI VALLEY TOMORROW MORNING. LIGHT
WINDS BECOME EAST OVER THE SOUTHERN HALF OF THE LAKE AND VARIABLE
OVER THE NORTHERN HALF TOMORROW AFTERNOON.  THE LOW WEAKENS AS IT
PASSES OVER CENTRAL IL TOMORROW AND HIGH PRESSURE THEN BUILDS OVER
THE PLAINS TOMORROW NIGHT.  NORTH TO NORTHWEST WINDS INCREASE TO 30
KT THURSDAY AS THE PRESSURE GRADIENT INCREASES BETWEEN THE HIGH OVER
THE PLAINS AND LARGE LOW MOVING UP THE EAST COAST.  WINDS DIMINISH
AS THE HIGH MOVES OVER THE LAKE THURSDAY NIGHT.  WINDS THEN BECOME
SOUTH BEHIND THE HIGH FRIDAY.  GUIDANCE DIFFERS ON HOW QUICKLY THE
NEXT LOW MOVES OVER LAKE SUPERIOR...BUT THE PRESSURE GRADIENT
INCREASES AHEAD OF THE LOW RESULTING IN SOUTH WINDS AROUND 30 KT
LATE THIS WEEK. HAVE THE WINDS FORECASTED TO COME UP FRIDAY
AFTERNOON...BUT THEY COULD COME UP AS LATE AS SATURDAY MORNING. 20
KT WINDS PERSIST THROUGH THE WEEKEND WITH SOUTHWEST WINDS BECOMING
NORTH SUNDAY AFTERNOON.  ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE
LAKE EARLY NEXT WEEK WITH STRONG SOUTH WINDS BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

&&

$$

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 252003
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
203 PM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* MID RANGE MVFR CIGS AT MDW AND POSSIBLY ORD INTO LATE AFTERNOON.

RC

//DISCUSSION...UPDATED 20Z...

MVFR CIGS IN 1500 TO 2200 FOOT RANGE OVER SOUTH AND SOUTHWEST CHI
METRO HAVE TRIED TO LIFT NORTH A BIT WITH WEST SOUTHWEST FLOW
ALOFT AND AT THE SURFACE. NORTHERN EDGE IS RAGGED SO COULD SEE MDW
SCATTER AT TIMES AND HAVE NOT INCLUDED MVFR IN ORD TAF BUT WILL
NEED TO MONITOR TRENDS. HI-RES GUIDANCE FAVORS MVFR CIGS THIS
EVENING WHILE REST OF GUIDANCE INDICATES DRIER AIR MOVING IN
ALOFT. OVERALL HAVE LOWER CONFIDENCE IN CIG FORECAST THROUGH THIS
EVENING...THOUGH OTHERWISE NO SIGNFICIANT AVIATION CONCERNS.

FROM 18Z...

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC

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

* LOW IN MVFR CIG TRENDS.

RC

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
147 PM CST

A HIGH PRESSURE RIDGE CONTINUES TO PUSH EAST CAUSING WINDS TO
DIMINISH ACROSS THE REGION. MEANWHILE A LOW CURRENTLY OVER THE
DAKOTAS REACHES THE MID MISSISSIPPI VALLEY TOMORROW MORNING. LIGHT
WINDS BECOME EAST OVER THE SOUTHERN HALF OF THE LAKE AND VARIABLE
OVER THE NORTHERN HALF TOMORROW AFTERNOON.  THE LOW WEAKENS AS IT
PASSES OVER CENTRAL IL TOMORROW AND HIGH PRESSURE THEN BUILDS OVER
THE PLAINS TOMORROW NIGHT.  NORTH TO NORTHWEST WINDS INCREASE TO 30
KT THURSDAY AS THE PRESSURE GRADIENT INCREASES BETWEEN THE HIGH OVER
THE PLAINS AND LARGE LOW MOVING UP THE EAST COAST.  WINDS DIMINISH
AS THE HIGH MOVES OVER THE LAKE THURSDAY NIGHT.  WINDS THEN BECOME
SOUTH BEHIND THE HIGH FRIDAY.  GUIDANCE DIFFERS ON HOW QUICKLY THE
NEXT LOW MOVES OVER LAKE SUPERIOR...BUT THE PRESSURE GRADIENT
INCREASES AHEAD OF THE LOW RESULTING IN SOUTH WINDS AROUND 30 KT
LATE THIS WEEK. HAVE THE WINDS FORECASTED TO COME UP FRIDAY
AFTERNOON...BUT THEY COULD COME UP AS LATE AS SATURDAY MORNING. 20
KT WINDS PERSIST THROUGH THE WEEKEND WITH SOUTHWEST WINDS BECOMING
NORTH SUNDAY AFTERNOON.  ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE
LAKE EARLY NEXT WEEK WITH STRONG SOUTH WINDS BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

&&

$$

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 251947
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
147 PM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* NONE.

RC

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

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC

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

* HIGH IN ALL ELEMENTS.

RC

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
147 PM CST

A HIGH PRESSURE RIDGE CONTINUES TO PUSH EAST CAUSING WINDS TO
DIMINISH ACROSS THE REGION. MEANWHILE A LOW CURRENTLY OVER THE
DAKOTAS REACHES THE MID MISSISSIPPI VALLEY TOMORROW MORNING. LIGHT
WINDS BECOME EAST OVER THE SOUTHERN HALF OF THE LAKE AND VARIABLE
OVER THE NORTHERN HALF TOMORROW AFTERNOON.  THE LOW WEAKENS AS IT
PASSES OVER CENTRAL IL TOMORROW AND HIGH PRESSURE THEN BUILDS OVER
THE PLAINS TOMORROW NIGHT.  NORTH TO NORTHWEST WINDS INCREASE TO 30
KT THURSDAY AS THE PRESSURE GRADIENT INCREASES BETWEEN THE HIGH OVER
THE PLAINS AND LARGE LOW MOVING UP THE EAST COAST.  WINDS DIMINISH
AS THE HIGH MOVES OVER THE LAKE THURSDAY NIGHT.  WINDS THEN BECOME
SOUTH BEHIND THE HIGH FRIDAY.  GUIDANCE DIFFERS ON HOW QUICKLY THE
NEXT LOW MOVES OVER LAKE SUPERIOR...BUT THE PRESSURE GRADIENT
INCREASES AHEAD OF THE LOW RESULTING IN SOUTH WINDS AROUND 30 KT
LATE THIS WEEK. HAVE THE WINDS FORECASTED TO COME UP FRIDAY
AFTERNOON...BUT THEY COULD COME UP AS LATE AS SATURDAY MORNING. 20
KT WINDS PERSIST THROUGH THE WEEKEND WITH SOUTHWEST WINDS BECOMING
NORTH SUNDAY AFTERNOON.  ANOTHER HIGH PRESSURE SYSTEM MOVES OVER THE
LAKE EARLY NEXT WEEK WITH STRONG SOUTH WINDS BEHIND IT.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

&&

$$

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 251739
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1139 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* NONE.

RC

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

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC


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

* HIGH IN ALL ELEMENTS.

RC

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

&&

$$

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 251739
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1139 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* NONE.

RC

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

QUIET AVIATION WEATHER FOR NEXT 30 HOURS...AS SNOW ASSOCIATED WITH
WEAK LOW PRESSURE PASSING TO SOUTHWEST ON WEDNESDAY WILL REMAIN TO
THE SOUTHWEST OF THE TERMINALS. MID MVFR CIGS AT GYY SHOULD
SCATTER WITHIN NEXT HOUR OR SO AND MVFR OVER WISCONSIN EXPECTED TO
STAY TO THE NORTH THIS AFTERNOON...THOUGH COULD SEE FEW TO SCT
CLOUDS AT 020 FILL BACK IN A BIT. WIND SPEEDS WILL REMAIN
GENERALLY LIGHT THROUGHOUT THE TAF PERIOD...WITH DIRECTIONS
SHIFTING TO SOUTHERLY OVERNIGHT...SOUTHEAST WEDNESDAY MORNING AND
EAST-NORTHEAST BY MID TO LATE WEDNESDAY AFTERNOON.

RC


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

* HIGH IN ALL ELEMENTS.

RC

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

&&

$$

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 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
813 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* MVFR CEILINGS SCATTERING OUT THIS MORNING...THEN POSSIBLY
  RETURNING THIS AFTERNOON FOR A TIME.

KMD

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

MVFR CIGS ARE CLEARING IN NORTH CENTRAL ILLINOIS...SO EXPECT SOME
CLEARING THIS MORNING. LOWER MVFR STRATUS FROM 1000-2000 FT IS
MOVING SOUTHEAST THROUGH WISCONSIN...BUT GUIDANCE IS STILL MIXED
AS TO HOW INTACT IT WILL BE WHEN IT MOVES THROUGH NORTHEAST
ILLNOIS AND NW INDIANA. SEEMS AS THOUGH IT MAY TEMPORARILY GO
BROKEN. KEPT THE SCATTERED MENTION FOR NOW BUT MAY NEED TO GO
BROKEN IF IT KEEPS PROGRESSING.

KMD


PREVIOUS DISCUSSION FROM 12Z...

BETTER SNOW DEVELOPMENT CONTINUING TO DEPART TO THE EAST OF THE
TERMINALS EARLY THIS MORNING...WHILE SOME ADDITIONAL SCATTER
FLURRIES ARE APPROACHING AS ANOTHER MID LEVEL DISTURBANCE MOVES
ACROSS THE REGION. EXPECT THESE FLURRIES TO BE IN PLACE OVER THE
NEXT COUPLE OF HOURS BEFORE ALSO EXITING TO THE EAST...AS MVFR
CEILINGS REMAIN OVERHEAD. THESE MVFR CEILINGS STRETCH ACROSS MUCH
OF THE REGION THIS MORNING...BUT WITH SOME HOLES DEVELOPING NEAR
THE IOWA AND ILLINOIS BORDER. ALTHOUGH CONFIDENCE IS NOT TOO
HIGH...DID GO PESSIMISTIC WITH THE TAFS AND KEPT MVFR CEILINGS IN
PLACE THROUGH MID DAY. COULD SEE THIS HOLE FILLING BACK IN LATER
THIS MORNING...AND POSSIBLY HELPING TO KEEP THESE LOWER CEILINGS
IN PLACE A LITTLE LONGER INTO THE AFTERNOON. SHOULD OBSERVE AN
IMPROVING TREND INTO THE AFTERNOON BEFORE THESE CLOUDS SCATTER
ALTOGETHER...LEAVING ONLY HIGH LEVEL CLOUD COVER.

RODRIGUEZ

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

* HIGH WITH MVFR SCATTERING FOR A TIME...LOW ON WHETHER THEY
  RETURN AND FOR HOW LONG THIS AFTERNOON.

KMD

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 251413
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
813 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* MVFR CEILINGS SCATTERING OUT THIS MORNING...THEN POSSIBLY
  RETURNING THIS AFTERNOON FOR A TIME.

KMD

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

MVFR CIGS ARE CLEARING IN NORTH CENTRAL ILLINOIS...SO EXPECT SOME
CLEARING THIS MORNING. LOWER MVFR STRATUS FROM 1000-2000 FT IS
MOVING SOUTHEAST THROUGH WISCONSIN...BUT GUIDANCE IS STILL MIXED
AS TO HOW INTACT IT WILL BE WHEN IT MOVES THROUGH NORTHEAST
ILLNOIS AND NW INDIANA. SEEMS AS THOUGH IT MAY TEMPORARILY GO
BROKEN. KEPT THE SCATTERED MENTION FOR NOW BUT MAY NEED TO GO
BROKEN IF IT KEEPS PROGRESSING.

KMD


PREVIOUS DISCUSSION FROM 12Z...

BETTER SNOW DEVELOPMENT CONTINUING TO DEPART TO THE EAST OF THE
TERMINALS EARLY THIS MORNING...WHILE SOME ADDITIONAL SCATTER
FLURRIES ARE APPROACHING AS ANOTHER MID LEVEL DISTURBANCE MOVES
ACROSS THE REGION. EXPECT THESE FLURRIES TO BE IN PLACE OVER THE
NEXT COUPLE OF HOURS BEFORE ALSO EXITING TO THE EAST...AS MVFR
CEILINGS REMAIN OVERHEAD. THESE MVFR CEILINGS STRETCH ACROSS MUCH
OF THE REGION THIS MORNING...BUT WITH SOME HOLES DEVELOPING NEAR
THE IOWA AND ILLINOIS BORDER. ALTHOUGH CONFIDENCE IS NOT TOO
HIGH...DID GO PESSIMISTIC WITH THE TAFS AND KEPT MVFR CEILINGS IN
PLACE THROUGH MID DAY. COULD SEE THIS HOLE FILLING BACK IN LATER
THIS MORNING...AND POSSIBLY HELPING TO KEEP THESE LOWER CEILINGS
IN PLACE A LITTLE LONGER INTO THE AFTERNOON. SHOULD OBSERVE AN
IMPROVING TREND INTO THE AFTERNOON BEFORE THESE CLOUDS SCATTER
ALTOGETHER...LEAVING ONLY HIGH LEVEL CLOUD COVER.

RODRIGUEZ

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

* HIGH WITH MVFR SCATTERING FOR A TIME...LOW ON WHETHER THEY
  RETURN AND FOR HOW LONG THIS AFTERNOON.

KMD

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 251206
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
606 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* SCATTERED FLURRIES EARLY THIS MORNING.

* MVFR CEILINGS THROUGH MID DAY.

RODRIGUEZ

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

BETTER SNOW DEVELOPMENT CONTINUING TO DEPART TO THE EAST OF THE
TERMINALS EARLY THIS MORNING...WHILE SOME ADDITIONAL SCATTER
FLURRIES ARE APPROACHING AS ANOTHER MID LEVEL DISTURBANCE MOVES
ACROSS THE REGION. EXPECT THESE FLURRIES TO BE IN PLACE OVER THE
NEXT COUPLE OF HOURS BEFORE ALSO EXITING TO THE EAST...AS MVFR
CEILINGS REMAIN OVERHEAD. THESE MVFR CEILINGS STRETCH ACROSS MUCH
OF THE REGION THIS MORNING...BUT WITH SOME HOLES DEVELOPING NEAR
THE IOWA AND ILLINOIS BORDER. ALTHOUGH CONFIDENCE IS NOT TOO
HIGH...DID GO PESSIMISTIC WITH THE TAFS AND KEPT MVFR CEILINGS IN
PLACE THROUGH MID DAY. COULD SEE THIS HOLE FILLING BACK IN LATER
THIS MORNING...AND POSSIBLY HELPING TO KEEP THESE LOWER CEILINGS
IN PLACE A LITTLE LONGER INTO THE AFTERNOON. SHOULD OBSERVE AN
IMPROVING TREND INTO THE AFTERNOON BEFORE THESE CLOUDS SCATTER
ALTOGETHER...LEAVING ONLY HIGH LEVEL CLOUD COVER.

RODRIGUEZ


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

* MEDIUM CONFIDENCE WITH SCATTERED FLURRIES.

* HIGH CONFIDENCE WITH MVFR CEILINGS...MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 251206
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
606 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* SCATTERED FLURRIES EARLY THIS MORNING.

* MVFR CEILINGS THROUGH MID DAY.

RODRIGUEZ

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

BETTER SNOW DEVELOPMENT CONTINUING TO DEPART TO THE EAST OF THE
TERMINALS EARLY THIS MORNING...WHILE SOME ADDITIONAL SCATTER
FLURRIES ARE APPROACHING AS ANOTHER MID LEVEL DISTURBANCE MOVES
ACROSS THE REGION. EXPECT THESE FLURRIES TO BE IN PLACE OVER THE
NEXT COUPLE OF HOURS BEFORE ALSO EXITING TO THE EAST...AS MVFR
CEILINGS REMAIN OVERHEAD. THESE MVFR CEILINGS STRETCH ACROSS MUCH
OF THE REGION THIS MORNING...BUT WITH SOME HOLES DEVELOPING NEAR
THE IOWA AND ILLINOIS BORDER. ALTHOUGH CONFIDENCE IS NOT TOO
HIGH...DID GO PESSIMISTIC WITH THE TAFS AND KEPT MVFR CEILINGS IN
PLACE THROUGH MID DAY. COULD SEE THIS HOLE FILLING BACK IN LATER
THIS MORNING...AND POSSIBLY HELPING TO KEEP THESE LOWER CEILINGS
IN PLACE A LITTLE LONGER INTO THE AFTERNOON. SHOULD OBSERVE AN
IMPROVING TREND INTO THE AFTERNOON BEFORE THESE CLOUDS SCATTER
ALTOGETHER...LEAVING ONLY HIGH LEVEL CLOUD COVER.

RODRIGUEZ


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

* MEDIUM CONFIDENCE WITH SCATTERED FLURRIES.

* HIGH CONFIDENCE WITH MVFR CEILINGS...MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY NIGHT...SLIGHT CHANCE OF LIGHT SNOW.

THURSDAY...VFR.

FRIDAY...SLIGHT CHANCE OF LIGHT RAIN OR SNOW.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

RODRIGUEZ

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 251037
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
437 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* A BRIEF PERIOD OVER THE NEXT 1-2 HOURS OF HEAVIER SNOW WITH IFR
  VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* HIGH CONFIDENCE WITH STRONGER SNOW SHOWERS AND TIMING.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 251037
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
437 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* A BRIEF PERIOD OVER THE NEXT 1-2 HOURS OF HEAVIER SNOW WITH IFR
  VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* HIGH CONFIDENCE WITH STRONGER SNOW SHOWERS AND TIMING.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 251037
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
437 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* A BRIEF PERIOD OVER THE NEXT 1-2 HOURS OF HEAVIER SNOW WITH IFR
  VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* HIGH CONFIDENCE WITH STRONGER SNOW SHOWERS AND TIMING.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
436 AM CST

AS LOW PRESSURE OVER NORTHERN QUEBEC CONTINUES TO LIFT NORTH
TODAY...A TROUGH OF LOW PRESSURE AND FRONTAL BOUNDARY EXTENDING
FROM THIS LOW SOUTHWEST THROUGH THE CENTRAL GREAT LAKES WILL SHIFT
TO THE EASTERN GREAT LAKES AND SOUTHERN QUEBEC. WHILE THIS IS
OCCURRING...EXPECT THE ONGOING DIMINISHING TREND WITH THE
NORTHWEST AND WEST WINDS IN PLACE TO CONTINUE. WINDS ARE CURRENTLY
TO 30 KT ACROSS THE LAKE EARLY THIS MORNING BUT DO EXPECT THEM TO
DIMINISH TO 15 TO 25 KT THIS MORNING...AND THEN TO 10 TO 20 KT IN
THE AFTERNOON. BUILDING HIGH PRESSURE ACROSS THE REGION WILL
PROVIDE A PERIOD OF LIGHTER WINDS OVER THE LAKE TONIGHT INTO
WEDNESDAY AND PART OF WEDNESDAY NIGHT. DEPARTING LOW PRESSURE TO
THE SOUTH OF THE LAKE AND ANOTHER HIGH BUILDING ACROSS THE PLAINS
WILL HELP PROVIDE A TIGHTER PRESSURE GRADIENT OVER THE
LAKE...HELPING RETURN STRONGER WINDS BACK OVER THE LAKE THURSDAY
INTO THURSDAY NIGHT.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 250921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
321 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* A BRIEF PERIOD OVER THE NEXT 1-2 HOURS OF HEAVIER SNOW WITH IFR
  VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* HIGH CONFIDENCE WITH STRONGER SNOW SHOWERS AND TIMING.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 250921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
321 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* A BRIEF PERIOD OVER THE NEXT 1-2 HOURS OF HEAVIER SNOW WITH IFR
  VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* HIGH CONFIDENCE WITH STRONGER SNOW SHOWERS AND TIMING.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE GARY TO MICHIGAN CITY IN UNTIL 4 PM TUESDAY.

     SMALL CRAFT ADVISORY...LMZ743 UNTIL 10 AM TUESDAY.

&&

$$

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 250903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
303 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* POTENTIAL FOR A STRONGER SNOW SHOWER EARLY THIS FORECAST
  PERIOD...WITH POSSIBLE IFR VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* MEDIUM CONFIDENCE WITH ANY STRONGER SNOW SHOWERS EARLY.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.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 250903
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
303 AM CST TUE NOV 25 2014

.SHORT TERM...
303 AM CST

THROUGH WEDNESDAY...

PRIMARY FORECAST CHALLENGE TODAY IS CLOUD COVER. GUIDANCE IS ALL
FAIRLY AGGRESSIVE IS CLEARING THINGS OUT THIS AFTERNOON SAVE FOR THE
WRF-NAM. MODELS ARE OFTEN TOO QUICK TO CLEAR STRATUS OUT IN THE
WINTER...THOUGH IN THIS CASE IT IS A FAIRLY TRANSIENT PATTERN SO
STRATUS MAY BE A BIT QUICKER TO CLEAR THAN IS TYPICAL. MOS GUIDANCE
KEEPS SKIES FAIRLY CLOUDY AND HAVE MAINTAINED CLOUDINESS LONGER THAN
GUIDANCE SUGGESTS BUT DO PARTIALLY CLEAR SKIES OUT TONIGHT FOR A
TIME BEFORE CLOUDS ROLL BACK IN AHEAD OF THE NEXT SYSTEM.

SPEAKING OF THE NEXT SYSTEM...GUIDANCE CONTINUES TO TAKE THE CLIPPER
ON THE SOUTHERN ROUTE WITH ITS PRECIP LARGELY MISSING OUR CWA. HAVE
MAINTAINED SOME SLIGHT CHANCE POPS IN OUR SOUTHWESTERN MOST CWA
WEDNESDAY BUT OTHERWISE CONTINUED THE TREND FROM THE DAY SHIFT OF
LOWERING POPS...COMPLETELY REMOVING THEM FROM MUCH OF THE CWA.

IZZI

&&

.LONG TERM...
303 AM CST

WEDNESDAY NIGHT ONWARD...

IN THE LONGER TERM GUIDANCE IS STILL BRINGS IN A TRANSIENT BUT
MODERATELY POTENT SHOT OF COLD AIR THANKSGIVING DAY WHEN HIGHS
SHOULD ONCE AGAIN HOLD IN THE 20S. LARGE SCALE PATTERN WILL BEGIN TO
TRANSITION TO MORE OF A ZONAL FLOW BY FRIDAY WITH WARM AIR ADVECTION
BEGINNING AND POSSIBLY PRODUCING A BIT OF LIGHT PRECIP...BUT IF
ANYTHING DOES FALL AMOUNTS LOOK TO BE VERY LIGHT. BY SATURDAY STRONG
LOW PRESSURE IS PROGGED TO TRACK EAST INTO THE UPPER GREAT LAKES
ALLOWING FOR A BRISK BUT MILD SOUTHERLY FLOW TO DEVELOP OVER THE
AREA. FORECAST 850MB TEMPS WOULD SUPPORT HIGHS WELL INTO THE 50S AND
PERHAPS NEAR 60...THOUGH 925MB TEMPS ARE NOT QUITE AS MILD AND THAT
COULD PARTIALLY BE A RESULT OF A BIT MORE SNOW COVER. HAVE RAISED
HIGHS A BIT OVER THE BLENDED INITIALIZATION BUT THINKING CURRENT
FORECAST IS STILL TOO COOL...ESPECIALLY IN AREAS WITH LITTLE OR NO
SNOW COVER WHICH SHOULD BE A LARGE PORTION OF THE CWA BY SATURDAY.
COLD FRONT LOOKS TO MOVE THROUGH SAT NIGHT OR SUNDAY BRINGING COOLER
WEATHER FOR A COUPLE DAYS BUT IN THE TRANSIENT RATHER ZONAL FLOW GFS
AND ECMWF BOTH HINT AT ANOTHER HEALTHY WARM UP TOWARD MIDDLE OF NEXT
WEEK. PRECIP CHANCES THROUGH THE PERIOD LOOK LOW AND LARGELY
INCONSEQUENTIAL IF ANYTHING DOES FALL.

IZZI

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* POTENTIAL FOR A STRONGER SNOW SHOWER EARLY THIS FORECAST
  PERIOD...WITH POSSIBLE IFR VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ

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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* MEDIUM CONFIDENCE WITH ANY STRONGER SNOW SHOWERS EARLY.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.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 250558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1158 PM CST MON NOV 24 2014

.UPDATE...

830 PM CST

MINOR ADDITIONAL TWEAKS TO GOING FORECAST TONIGHT...MAINLY TO
REFINE POPS FOR ADDITIONAL SCATTERED SNOW SHOWERS/FLURRIES
OVERNIGHT AND TO LOWER TEMPS A BIT WITH PERSISTENT COLD ADVECTION.

REPORTS OF FREEZING DRIZZLE HAVE TAPERED OFF AT MID-EVENING AS
ANTICIPATED PER FORECAST SOUNDING TRENDS. A COMPARISON OF ILX/DVN
00Z RAOBS SHOWS THE MINOR DIFFERENCE IN LOW LEVEL SATURATION DEPTH
WITH THE TOP OF THE ILX MOIST LAYER JUST BELOW 700 HPA AND -14C
WHILE AT DVN IT IS AT 650 HPA AND -18C AND THUS MORE LIKELY TO
CONTAIN ICE AND PRODUCE SNOW. RAP SOUNDING AND IR SATELLITE
TRENDS INDICATE THAT FREEZING DRIZZLE SHOULD BE LESS OF AN ISSUE
FOR REMAINDER OF THE EVENING AS THE COLUMN CONTINUES TO COOL AND
MOISTURE DEEPENS AGAIN WITH APPROACH OF SHORT WAVE APPROACHING
FROM NORTHEAST IA. THIS WAVE IS EXPECTED TO CONTINUE TO PRODUCE
SCATTERED SNOW SHOWERS AS IT MOVES INTO THE CWA OVERNIGHT...THOUGH
HRRR/NAM BOTH INDICATE A DECREASE IN COVERAGE AFTER MIDNIGHT OVER
OUR NORTHERN CWA. THUS WHILE FLURRIES/SNOW SHOWERS WILL BE AROUND
THROUGH MUCH OF THE NIGHT...IT APPEARS THAT ANY LIGHT ADDITIONAL
MEASURABLE SNOW (JUST A COUPLE TENTHS PERHAPS) WILL BE LIMITED TO
NORTHERN PARTS OF NORTH CENTRAL IL. SNOW SHOWERS SHOULD TAPER OFF
TO JUST FLURRIES AFTER 07-09Z (2-4 AM CST) WITH PASSAGE OF
NORTHEAST IA VORT...BASED ON EXTRAPOLATION OF RADAR LOOP.

OTHERWISE...HAVE LOWERED MIN TEMPS JUST A BIT OVERNIGHT AS WE WERE
ALREADY WITHIN A COUPLE OF DEGREES OF FORECAST MINS OUT WEST.
BLENDED IN A BIT OF MAV/MET MOS GUIDANCE WHICH LOWERED MINS ABOUT
2 DEGREES IN MANY PLACES. WINDS CONTINUE TO GUST ABOVE 35 MPH IN A
FEW SPOTS...BUT WILL GRADUALLY DIMINISH OVERNIGHT AS GRADIENT
SLOWLY WEAKENS AND SURFACE PRESSURE RISE MAXIMA CONTINUES TO EXIT
TO OUR NORTHEAST.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* POTENTIAL FOR A STRONGER SNOW SHOWER EARLY THIS FORECAST
  PERIOD...WITH POSSIBLE IFR VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* MEDIUM CONFIDENCE WITH ANY STRONGER SNOW SHOWERS EARLY.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 250558
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1158 PM CST MON NOV 24 2014

.UPDATE...

830 PM CST

MINOR ADDITIONAL TWEAKS TO GOING FORECAST TONIGHT...MAINLY TO
REFINE POPS FOR ADDITIONAL SCATTERED SNOW SHOWERS/FLURRIES
OVERNIGHT AND TO LOWER TEMPS A BIT WITH PERSISTENT COLD ADVECTION.

REPORTS OF FREEZING DRIZZLE HAVE TAPERED OFF AT MID-EVENING AS
ANTICIPATED PER FORECAST SOUNDING TRENDS. A COMPARISON OF ILX/DVN
00Z RAOBS SHOWS THE MINOR DIFFERENCE IN LOW LEVEL SATURATION DEPTH
WITH THE TOP OF THE ILX MOIST LAYER JUST BELOW 700 HPA AND -14C
WHILE AT DVN IT IS AT 650 HPA AND -18C AND THUS MORE LIKELY TO
CONTAIN ICE AND PRODUCE SNOW. RAP SOUNDING AND IR SATELLITE
TRENDS INDICATE THAT FREEZING DRIZZLE SHOULD BE LESS OF AN ISSUE
FOR REMAINDER OF THE EVENING AS THE COLUMN CONTINUES TO COOL AND
MOISTURE DEEPENS AGAIN WITH APPROACH OF SHORT WAVE APPROACHING
FROM NORTHEAST IA. THIS WAVE IS EXPECTED TO CONTINUE TO PRODUCE
SCATTERED SNOW SHOWERS AS IT MOVES INTO THE CWA OVERNIGHT...THOUGH
HRRR/NAM BOTH INDICATE A DECREASE IN COVERAGE AFTER MIDNIGHT OVER
OUR NORTHERN CWA. THUS WHILE FLURRIES/SNOW SHOWERS WILL BE AROUND
THROUGH MUCH OF THE NIGHT...IT APPEARS THAT ANY LIGHT ADDITIONAL
MEASURABLE SNOW (JUST A COUPLE TENTHS PERHAPS) WILL BE LIMITED TO
NORTHERN PARTS OF NORTH CENTRAL IL. SNOW SHOWERS SHOULD TAPER OFF
TO JUST FLURRIES AFTER 07-09Z (2-4 AM CST) WITH PASSAGE OF
NORTHEAST IA VORT...BASED ON EXTRAPOLATION OF RADAR LOOP.

OTHERWISE...HAVE LOWERED MIN TEMPS JUST A BIT OVERNIGHT AS WE WERE
ALREADY WITHIN A COUPLE OF DEGREES OF FORECAST MINS OUT WEST.
BLENDED IN A BIT OF MAV/MET MOS GUIDANCE WHICH LOWERED MINS ABOUT
2 DEGREES IN MANY PLACES. WINDS CONTINUE TO GUST ABOVE 35 MPH IN A
FEW SPOTS...BUT WILL GRADUALLY DIMINISH OVERNIGHT AS GRADIENT
SLOWLY WEAKENS AND SURFACE PRESSURE RISE MAXIMA CONTINUES TO EXIT
TO OUR NORTHEAST.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* PERSISTENT SCATTERED LIGHT SNOW SHOWERS...BUT REMAINING VFR.

* POTENTIAL FOR A STRONGER SNOW SHOWER EARLY THIS FORECAST
  PERIOD...WITH POSSIBLE IFR VIS.

* MVFR CEILINGS THROUGH LATE MORNING.

RODRIGUEZ

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

LATEST RADAR IMAGERY SHOWING SNOW SHOWERS PERSISTING AROUND THE
TERMINALS THIS HOUR...BUT WITH NO REAL VIS RESTRICTION. THESE SNOW
SHOWERS AND VIS TRENDS WILL CONTINUE EARLY THIS MORNING BUT WITH
THE POSSIBILITY FOR A BRIER HEAVIER SNOW SHOWER EARLY...POSSIBLY
PROVIDING IFR VIS. HAVE MAINTAINED TEMPO GROUP WITH 2SM VIS BUT
DID PUSH IT BACK AN HOUR BASED ON LATEST TRENDS. ANY SNOW WILL
LIKELY COME TO AN END LATER THIS MORNING WHILE MVFR CEILINGS
SLOWLY LIFT TO VFR BY LATE MORNING...WITH VFR CEILINGS THEN
LINGERING INTO THE AFTERNOON. AS HIGH PRESSURE BUILDS ACROSS THE
REGION THIS AFTERNOON SHOULD SEE THESE CLOUDS SCATTER...WITH ONLY
HIGH LEVEL CLOUD THEN ANTICIPATED THROUGH THE REST OF THE FORECAST
PERIOD. THE STRONGER WESTERLY WINDS ARE CURRENTLY
DIMINISHING...WITH THIS TREND CONTINUING THROUGH THE REST OF THE
MORNING BUT WHILE STAYING WESTERLY.

RODRIGUEZ


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

* HIGH CONFIDENCE WITH SCATTERED LIGHT SNOW SHOWERS.

* MEDIUM CONFIDENCE WITH ANY STRONGER SNOW SHOWERS EARLY.

* HIGH CONFIDENCE WITH MVFR CEILINGS...LOW MEDIUM CONFIDENCE WITH
  DURATION.

RODRIGUEZ

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 250303
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 PM CST MON NOV 24 2014

.UPDATE...

830 PM CST

MINOR ADDITIONAL TWEAKS TO GOING FORECAST TONIGHT...MAINLY TO
REFINE POPS FOR ADDITIONAL SCATTERED SNOW SHOWERS/FLURRIES
OVERNIGHT AND TO LOWER TEMPS A BIT WITH PERSISTENT COLD ADVECTION.

REPORTS OF FREEZING DRIZZLE HAVE TAPERED OFF AT MID-EVENING AS
ANTICIPATED PER FORECAST SOUNDING TRENDS. A COMPARISON OF ILX/DVN
00Z RAOBS SHOWS THE MINOR DIFFERENCE IN LOW LEVEL SATURATION DEPTH
WITH THE TOP OF THE ILX MOIST LAYER JUST BELOW 700 HPA AND -14C
WHILE AT DVN IT IS AT 650 HPA AND -18C AND THUS MORE LIKELY TO
CONTAIN ICE AND PRODUCE SNOW. RAP SOUNDING AND IR SATELLITE
TRENDS INDICATE THAT FREEZING DRIZZLE SHOULD BE LESS OF AN ISSUE
FOR REMAINDER OF THE EVENING AS THE COLUMN CONTINUES TO COOL AND
MOISTURE DEEPENS AGAIN WITH APPROACH OF SHORT WAVE APPROACHING
FROM NORTHEAST IA. THIS WAVE IS EXPECTED TO CONTINUE TO PRODUCE
SCATTERED SNOW SHOWERS AS IT MOVES INTO THE CWA OVERNIGHT...THOUGH
HRRR/NAM BOTH INDICATE A DECREASE IN COVERAGE AFTER MIDNIGHT OVER
OUR NORTHERN CWA. THUS WHILE FLURRIES/SNOW SHOWERS WILL BE AROUND
THROUGH MUCH OF THE NIGHT...IT APPEARS THAT ANY LIGHT ADDITIONAL
MEASURABLE SNOW (JUST A COUPLE TENTHS PERHAPS) WILL BE LIMITED TO
NORTHERN PARTS OF NORTH CENTRAL IL. SNOW SHOWERS SHOULD TAPER OFF
TO JUST FLURRIES AFTER 07-09Z (2-4 AM CST) WITH PASSAGE OF
NORTHEAST IA VORT...BASED ON EXTRAPOLATION OF RADAR LOOP.

OTHERWISE...HAVE LOWERED MIN TEMPS JUST A BIT OVERNIGHT AS WE WERE
ALREADY WITHIN A COUPLE OF DEGREES OF FORECAST MINS OUT WEST.
BLENDED IN A BIT OF MAV/MET MOS GUIDANCE WHICH LOWERED MINS ABOUT
2 DEGREES IN MANY PLACES. WINDS CONTINUE TO GUST ABOVE 35 MPH IN A
FEW SPOTS...BUT WILL GRADUALLY DIMINISH OVERNIGHT AS GRADIENT
SLOWLY WEAKENS AND SURFACE PRESSURE RISE MAXIMA CONTINUES TO EXIT
TO OUR NORTHEAST.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* LINGERING LIGHT SNOW SHOWERS MAY REDUCE VSBY BRIEFLY THE NEXT
  FEW HOURS. ANOTHER ROUND OF LIGHT SNOW SHOWERS POSSIBLE AFTER
  MIDNIGHT BUT MAY DIMINISH AS IT ARRIVES. IFR VSBY POSSIBLE IF IT
  HOLDS TOGETHER.

* WEST-SOUTHWEST WINDS GUSTING TO AROUND 30 KT DIMINISH OVERNIGHT.

* MVFR CIGS PERSIST THROUGH TONIGHT AND MAY CONTINUE TOMORROW AS
  WELL.

MDB

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

SNOW SHOWER COVERAGE AND INTENSITY HAS DIMINISHED OVER THE LAST
HOUR BUT AM STILL WATCHING ANOTHER UPPER WAVE GENERATING BANDS OF
SNOW ACROSS NORTHEAST IOWA. WILL CONTINUE TO MENTION TEMPO IFR
VSBY MAINLY AFTER MIDNIGHT BUT THE SNOW SHOWERS MAY DIMINISH AS
THE APPROACH...THOUGH HAVE GOOD CONFIDENCE THEY WILL BE MAINTAINED
AS THEY REACH RFD. OTHERWISE WEST-SOUTHWEST WINDS ARE BEGINNING TO
EASE WITH FEW GUSTS OVER 30 KT. THIS DOWNWARD TREND WILL CONTINUE
INTO THE OVERNIGHT.

FROM 00Z...

A SERIES OF UPPER DISTURBANCES WILL CONTINUE TO DRIVE BANDS OF
SNOW SHOWERS INTO THE OVERNIGHT HOURS. MAY SEE A BIT OF A BREAK IN
THE COVERAGE LATE THIS EVENING BUT ANOTHER WAVE COMING ACROSS
NORTHEAST IOWA WILL LIKELY BRING AN INCREASE IN ACTIVITY AROUND
MIDNIGHT INTO THE OVERNIGHT. WILL INDICATE TEMPO IFR VSBY BASED ON
UPSTREAM TRENDS. ACCUMULATION WILL BE LIGHT WITH LESS THAN A HALF
INCH ADDITIONAL EXPECTED.

AM A LITTLE CONCERNED ABOUT SOME LIGHT FREEZING DRIZZLE THIS
EVENING AS WELL AS MOISTURE ALOFT DECREASES FOR A TIME. AREAS
SOUTH OF THE TERMINALS ARE STARTING TO REPORT THIS AND IT IS MORE
FAVORED TO THE SOUTH BUT IT IS POSSIBLE SOME COULD OCCUR AT THE
TERMINALS. POTENTIAL OF OCCURRENCE IS TOO LOW TO INCLUDE IN THE
TAF FOR NOW BUT WILL MONITOR.

WEST-SOUTHWEST WINDS WILL CONTINUE TO GUST TO AROUND 35 KT THROUGH
EARLY EVENING WITH SNOW SHOWERS HELPING THEM TO OCCUR. EXPECT
GUSTS TO STEADILY DECREASE LATER THIS EVENING INTO THE OVERNIGHT.
MVFR CIGS PERSIST AND SHOULD DO SO OVERNIGHT BUT MAY LIFT A FEW
HUNDRED FEET AT TIMES. LIGHTER WEST WINDS ARE EXPECTED TUESDAY
WITH MVFR STRATUS TO START THE MORNING. HAVE LOW CONFIDENCE IN HOW
LONG MVFR MAY PERSIST OR IF IT LIFTS TO VFR OR SCATTERS AT SOME
POINT DURING THE DAY. WILL LIKELY NEED TO ADJUST THIS WITH LATER
UPDATES.

MDB

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

* HIGH CONFIDENCE IN SOME LINGERING LIGHT SNOW SHOWERS. MEDIUM
  CONFIDENCE THAT COVERAGE WILL INCREASE AFTER MIDNIGHT.

* HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE IN MVFR CIGS PERSISTING TONIGHT WITH LOW
  CONFIDENCE IN HOW LONG THEY MAY LAST TUESDAY.

MDB

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 250303
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
903 PM CST MON NOV 24 2014

.UPDATE...

830 PM CST

MINOR ADDITIONAL TWEAKS TO GOING FORECAST TONIGHT...MAINLY TO
REFINE POPS FOR ADDITIONAL SCATTERED SNOW SHOWERS/FLURRIES
OVERNIGHT AND TO LOWER TEMPS A BIT WITH PERSISTENT COLD ADVECTION.

REPORTS OF FREEZING DRIZZLE HAVE TAPERED OFF AT MID-EVENING AS
ANTICIPATED PER FORECAST SOUNDING TRENDS. A COMPARISON OF ILX/DVN
00Z RAOBS SHOWS THE MINOR DIFFERENCE IN LOW LEVEL SATURATION DEPTH
WITH THE TOP OF THE ILX MOIST LAYER JUST BELOW 700 HPA AND -14C
WHILE AT DVN IT IS AT 650 HPA AND -18C AND THUS MORE LIKELY TO
CONTAIN ICE AND PRODUCE SNOW. RAP SOUNDING AND IR SATELLITE
TRENDS INDICATE THAT FREEZING DRIZZLE SHOULD BE LESS OF AN ISSUE
FOR REMAINDER OF THE EVENING AS THE COLUMN CONTINUES TO COOL AND
MOISTURE DEEPENS AGAIN WITH APPROACH OF SHORT WAVE APPROACHING
FROM NORTHEAST IA. THIS WAVE IS EXPECTED TO CONTINUE TO PRODUCE
SCATTERED SNOW SHOWERS AS IT MOVES INTO THE CWA OVERNIGHT...THOUGH
HRRR/NAM BOTH INDICATE A DECREASE IN COVERAGE AFTER MIDNIGHT OVER
OUR NORTHERN CWA. THUS WHILE FLURRIES/SNOW SHOWERS WILL BE AROUND
THROUGH MUCH OF THE NIGHT...IT APPEARS THAT ANY LIGHT ADDITIONAL
MEASURABLE SNOW (JUST A COUPLE TENTHS PERHAPS) WILL BE LIMITED TO
NORTHERN PARTS OF NORTH CENTRAL IL. SNOW SHOWERS SHOULD TAPER OFF
TO JUST FLURRIES AFTER 07-09Z (2-4 AM CST) WITH PASSAGE OF
NORTHEAST IA VORT...BASED ON EXTRAPOLATION OF RADAR LOOP.

OTHERWISE...HAVE LOWERED MIN TEMPS JUST A BIT OVERNIGHT AS WE WERE
ALREADY WITHIN A COUPLE OF DEGREES OF FORECAST MINS OUT WEST.
BLENDED IN A BIT OF MAV/MET MOS GUIDANCE WHICH LOWERED MINS ABOUT
2 DEGREES IN MANY PLACES. WINDS CONTINUE TO GUST ABOVE 35 MPH IN A
FEW SPOTS...BUT WILL GRADUALLY DIMINISH OVERNIGHT AS GRADIENT
SLOWLY WEAKENS AND SURFACE PRESSURE RISE MAXIMA CONTINUES TO EXIT
TO OUR NORTHEAST.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* LINGERING LIGHT SNOW SHOWERS MAY REDUCE VSBY BRIEFLY THE NEXT
  FEW HOURS. ANOTHER ROUND OF LIGHT SNOW SHOWERS POSSIBLE AFTER
  MIDNIGHT BUT MAY DIMINISH AS IT ARRIVES. IFR VSBY POSSIBLE IF IT
  HOLDS TOGETHER.

* WEST-SOUTHWEST WINDS GUSTING TO AROUND 30 KT DIMINISH OVERNIGHT.

* MVFR CIGS PERSIST THROUGH TONIGHT AND MAY CONTINUE TOMORROW AS
  WELL.

MDB

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

SNOW SHOWER COVERAGE AND INTENSITY HAS DIMINISHED OVER THE LAST
HOUR BUT AM STILL WATCHING ANOTHER UPPER WAVE GENERATING BANDS OF
SNOW ACROSS NORTHEAST IOWA. WILL CONTINUE TO MENTION TEMPO IFR
VSBY MAINLY AFTER MIDNIGHT BUT THE SNOW SHOWERS MAY DIMINISH AS
THE APPROACH...THOUGH HAVE GOOD CONFIDENCE THEY WILL BE MAINTAINED
AS THEY REACH RFD. OTHERWISE WEST-SOUTHWEST WINDS ARE BEGINNING TO
EASE WITH FEW GUSTS OVER 30 KT. THIS DOWNWARD TREND WILL CONTINUE
INTO THE OVERNIGHT.

FROM 00Z...

A SERIES OF UPPER DISTURBANCES WILL CONTINUE TO DRIVE BANDS OF
SNOW SHOWERS INTO THE OVERNIGHT HOURS. MAY SEE A BIT OF A BREAK IN
THE COVERAGE LATE THIS EVENING BUT ANOTHER WAVE COMING ACROSS
NORTHEAST IOWA WILL LIKELY BRING AN INCREASE IN ACTIVITY AROUND
MIDNIGHT INTO THE OVERNIGHT. WILL INDICATE TEMPO IFR VSBY BASED ON
UPSTREAM TRENDS. ACCUMULATION WILL BE LIGHT WITH LESS THAN A HALF
INCH ADDITIONAL EXPECTED.

AM A LITTLE CONCERNED ABOUT SOME LIGHT FREEZING DRIZZLE THIS
EVENING AS WELL AS MOISTURE ALOFT DECREASES FOR A TIME. AREAS
SOUTH OF THE TERMINALS ARE STARTING TO REPORT THIS AND IT IS MORE
FAVORED TO THE SOUTH BUT IT IS POSSIBLE SOME COULD OCCUR AT THE
TERMINALS. POTENTIAL OF OCCURRENCE IS TOO LOW TO INCLUDE IN THE
TAF FOR NOW BUT WILL MONITOR.

WEST-SOUTHWEST WINDS WILL CONTINUE TO GUST TO AROUND 35 KT THROUGH
EARLY EVENING WITH SNOW SHOWERS HELPING THEM TO OCCUR. EXPECT
GUSTS TO STEADILY DECREASE LATER THIS EVENING INTO THE OVERNIGHT.
MVFR CIGS PERSIST AND SHOULD DO SO OVERNIGHT BUT MAY LIFT A FEW
HUNDRED FEET AT TIMES. LIGHTER WEST WINDS ARE EXPECTED TUESDAY
WITH MVFR STRATUS TO START THE MORNING. HAVE LOW CONFIDENCE IN HOW
LONG MVFR MAY PERSIST OR IF IT LIFTS TO VFR OR SCATTERS AT SOME
POINT DURING THE DAY. WILL LIKELY NEED TO ADJUST THIS WITH LATER
UPDATES.

MDB

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

* HIGH CONFIDENCE IN SOME LINGERING LIGHT SNOW SHOWERS. MEDIUM
  CONFIDENCE THAT COVERAGE WILL INCREASE AFTER MIDNIGHT.

* HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE IN MVFR CIGS PERSISTING TONIGHT WITH LOW
  CONFIDENCE IN HOW LONG THEY MAY LAST TUESDAY.

MDB

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 250230
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
830 PM CST MON NOV 24 2014

.UPDATE...

830 PM CST

MINOR ADDITIONAL TWEAKS TO GOING FORECAST TONIGHT...MAINLY TO
REFINE POPS FOR ADDITIONAL SCATTERED SNOW SHOWERS/FLURRIES
OVERNIGHT AND TO LOWER TEMPS A BIT WITH PERSISTENT COLD ADVECTION.

REPORTS OF FREEZING DRIZZLE HAVE TAPERED OFF AT MID-EVENING AS
ANTICIPATED PER FORECAST SOUNDING TRENDS. A COMPARISON OF ILX/DVN
00Z RAOBS SHOWS THE MINOR DIFFERENCE IN LOW LEVEL SATURATION DEPTH
WITH THE TOP OF THE ILX MOIST LAYER JUST BELOW 700 HPA AND -14C
WHILE AT DVN IT IS AT 650 HPA AND -18C AND THUS MORE LIKELY TO
CONTAIN ICE AND PRODUCE SNOW. RAP SOUNDING AND IR SATELLITE
TRENDS INDICATE THAT FREEZING DRIZZLE SHOULD BE LESS OF AN ISSUE
FOR REMAINDER OF THE EVENING AS THE COLUMN CONTINUES TO COOL AND
MOISTURE DEEPENS AGAIN WITH APPROACH OF SHORT WAVE APPROACHING
FROM NORTHEAST IA. THIS WAVE IS EXPECTED TO CONTINUE TO PRODUCE
SCATTERED SNOW SHOWERS AS IT MOVES INTO THE CWA OVERNIGHT...THOUGH
HRRR/NAM BOTH INDICATE A DECREASE IN COVERAGE AFTER MIDNIGHT OVER
OUR NORTHERN CWA. THUS WHILE FLURRIES/SNOW SHOWERS WILL BE AROUND
THROUGH MUCH OF THE NIGHT...IT APPEARS THAT ANY LIGHT ADDITIONAL
MEASURABLE SNOW (JUST A COUPLE TENTHS PERHAPS) WILL BE LIMITED TO
NORTHERN PARTS OF NORTH CENTRAL IL. SNOW SHOWERS SHOULD TAPER OFF
TO JUST FLURRIES AFTER 07-09Z (2-4 AM CST) WITH PASSAGE OF
NORTHEAST IA VORT...BASED ON EXTRAPOLATION OF RADAR LOOP.

OTHERWISE...HAVE LOWERED MIN TEMPS JUST A BIT OVERNIGHT AS WE WERE
ALREADY WITHIN A COUPLE OF DEGREES OF FORECAST MINS OUT WEST.
BLENDED IN A BIT OF MAV/MET MOS GUIDANCE WHICH LOWERED MINS ABOUT
2 DEGREES IN MANY PLACES. WINDS CONTINUE TO GUST ABOVE 35 MPH IN A
FEW SPOTS...BUT WILL GRADUALLY DIMINISH OVERNIGHT AS GRADIENT
SLOWLY WEAKENS AND SURFACE PRESSURE RISE MAXIMA CONTINUES TO EXIT
TO OUR NORTHEAST.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* INTERMITTENT SNOW SHOWERS THROUGH THE OVERNIGHT WITH BRIEF IFR
  VSBY AT TIMES.

* LOW CHANCE FOR SOME PATCHY LIGHT FREEZING DRIZZLE INTO MID
  EVENING.

* WEST-SOUTHWEST WINDS GUSTING AROUND 35 KT THROUGH EARLY EVENING
  THEN GRADUALLY DIMINISH OVERNIGHT.

* MVFR CIGS PERSIST THROUGH TONIGHT AND MAY CONTINUE TOMORROW AS
  WELL.

MDB

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

A SERIES OF UPPER DISTURBANCES WILL CONTINUE TO DRIVE BANDS OF
SNOW SHOWERS INTO THE OVERNIGHT HOURS. MAY SEE A BIT OF A BREAK IN
THE COVERAGE LATE THIS EVENING BUT ANOTHER WAVE COMING ACROSS
NORTHEAST IOWA WILL LIKELY BRING AN INCREASE IN ACTIVITY AROUND
MIDNIGHT INTO THE OVERNIGHT. WILL INDICATE TEMPO IFR VSBY BASED ON
UPSTREAM TRENDS. ACCUMULATION WILL BE LIGHT WITH LESS THAN A HALF
INCH ADDITIONAL EXPECTED.

AM A LITTLE CONCERNED ABOUT SOME LIGHT FREEZING DRIZZLE THIS
EVENING AS WELL AS MOISTURE ALOFT DECREASES FOR A TIME. AREAS
SOUTH OF THE TERMINALS ARE STARTING TO REPORT THIS AND IT IS MORE
FAVORED TO THE SOUTH BUT IT IS POSSIBLE SOME COULD OCCUR AT THE
TERMINALS. POTENTIAL OF OCCURRENCE IS TOO LOW TO INCLUDE IN THE
TAF FOR NOW BUT WILL MONITOR.

WEST-SOUTHWEST WINDS WILL CONTINUE TO GUST TO AROUND 35 KT THROUGH
EARLY EVENING WITH SNOW SHOWERS HELPING THEM TO OCCUR. EXPECT
GUSTS TO STEADILY DECREASE LATER THIS EVENING INTO THE OVERNIGHT.
MVFR CIGS PERSIST AND SHOULD DO SO OVERNIGHT BUT MAY LIFT A FEW
HUNDRED FEET AT TIMES. LIGHTER WEST WINDS ARE EXPECTED TUESDAY
WITH MVFR STRATUS TO START THE MORNING. HAVE LOW CONFIDENCE IN HOW
LONG MVFR MAY PERSIST OR IF IT LIFTS TO VFR OR SCATTERS AT SOME
POINT DURING THE DAY. WILL LIKELY ENED TO ADJUST THIS WITH LATER
UPDATES.

MDB

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

* HIGH CONFIDENCE IN INTERMITTENT SNOW SHOWERS THROUGH AT LEAST EARLY
  TONIGHT. MEDIUM CONFIDENCE THAT BRIEF IFR VSBY WILL OCCUR AT
  TIMES.

* MEDIUM-HIGH CONIFDENCE THAT THREAT FOR -FZDZ IS LOW AND WOULD BE
  VERY LIGHT INTO MID EVENING IF IT DID OCCUR.

* HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE IN MVFR CIGS PERSISTING TONIGHT WITH LOW
  CONFIDENCE IN HOW LONG THEY MAY LAST TUESDAY.

MDB

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 250230
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
830 PM CST MON NOV 24 2014

.UPDATE...

830 PM CST

MINOR ADDITIONAL TWEAKS TO GOING FORECAST TONIGHT...MAINLY TO
REFINE POPS FOR ADDITIONAL SCATTERED SNOW SHOWERS/FLURRIES
OVERNIGHT AND TO LOWER TEMPS A BIT WITH PERSISTENT COLD ADVECTION.

REPORTS OF FREEZING DRIZZLE HAVE TAPERED OFF AT MID-EVENING AS
ANTICIPATED PER FORECAST SOUNDING TRENDS. A COMPARISON OF ILX/DVN
00Z RAOBS SHOWS THE MINOR DIFFERENCE IN LOW LEVEL SATURATION DEPTH
WITH THE TOP OF THE ILX MOIST LAYER JUST BELOW 700 HPA AND -14C
WHILE AT DVN IT IS AT 650 HPA AND -18C AND THUS MORE LIKELY TO
CONTAIN ICE AND PRODUCE SNOW. RAP SOUNDING AND IR SATELLITE
TRENDS INDICATE THAT FREEZING DRIZZLE SHOULD BE LESS OF AN ISSUE
FOR REMAINDER OF THE EVENING AS THE COLUMN CONTINUES TO COOL AND
MOISTURE DEEPENS AGAIN WITH APPROACH OF SHORT WAVE APPROACHING
FROM NORTHEAST IA. THIS WAVE IS EXPECTED TO CONTINUE TO PRODUCE
SCATTERED SNOW SHOWERS AS IT MOVES INTO THE CWA OVERNIGHT...THOUGH
HRRR/NAM BOTH INDICATE A DECREASE IN COVERAGE AFTER MIDNIGHT OVER
OUR NORTHERN CWA. THUS WHILE FLURRIES/SNOW SHOWERS WILL BE AROUND
THROUGH MUCH OF THE NIGHT...IT APPEARS THAT ANY LIGHT ADDITIONAL
MEASURABLE SNOW (JUST A COUPLE TENTHS PERHAPS) WILL BE LIMITED TO
NORTHERN PARTS OF NORTH CENTRAL IL. SNOW SHOWERS SHOULD TAPER OFF
TO JUST FLURRIES AFTER 07-09Z (2-4 AM CST) WITH PASSAGE OF
NORTHEAST IA VORT...BASED ON EXTRAPOLATION OF RADAR LOOP.

OTHERWISE...HAVE LOWERED MIN TEMPS JUST A BIT OVERNIGHT AS WE WERE
ALREADY WITHIN A COUPLE OF DEGREES OF FORECAST MINS OUT WEST.
BLENDED IN A BIT OF MAV/MET MOS GUIDANCE WHICH LOWERED MINS ABOUT
2 DEGREES IN MANY PLACES. WINDS CONTINUE TO GUST ABOVE 35 MPH IN A
FEW SPOTS...BUT WILL GRADUALLY DIMINISH OVERNIGHT AS GRADIENT
SLOWLY WEAKENS AND SURFACE PRESSURE RISE MAXIMA CONTINUES TO EXIT
TO OUR NORTHEAST.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* INTERMITTENT SNOW SHOWERS THROUGH THE OVERNIGHT WITH BRIEF IFR
  VSBY AT TIMES.

* LOW CHANCE FOR SOME PATCHY LIGHT FREEZING DRIZZLE INTO MID
  EVENING.

* WEST-SOUTHWEST WINDS GUSTING AROUND 35 KT THROUGH EARLY EVENING
  THEN GRADUALLY DIMINISH OVERNIGHT.

* MVFR CIGS PERSIST THROUGH TONIGHT AND MAY CONTINUE TOMORROW AS
  WELL.

MDB

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

A SERIES OF UPPER DISTURBANCES WILL CONTINUE TO DRIVE BANDS OF
SNOW SHOWERS INTO THE OVERNIGHT HOURS. MAY SEE A BIT OF A BREAK IN
THE COVERAGE LATE THIS EVENING BUT ANOTHER WAVE COMING ACROSS
NORTHEAST IOWA WILL LIKELY BRING AN INCREASE IN ACTIVITY AROUND
MIDNIGHT INTO THE OVERNIGHT. WILL INDICATE TEMPO IFR VSBY BASED ON
UPSTREAM TRENDS. ACCUMULATION WILL BE LIGHT WITH LESS THAN A HALF
INCH ADDITIONAL EXPECTED.

AM A LITTLE CONCERNED ABOUT SOME LIGHT FREEZING DRIZZLE THIS
EVENING AS WELL AS MOISTURE ALOFT DECREASES FOR A TIME. AREAS
SOUTH OF THE TERMINALS ARE STARTING TO REPORT THIS AND IT IS MORE
FAVORED TO THE SOUTH BUT IT IS POSSIBLE SOME COULD OCCUR AT THE
TERMINALS. POTENTIAL OF OCCURRENCE IS TOO LOW TO INCLUDE IN THE
TAF FOR NOW BUT WILL MONITOR.

WEST-SOUTHWEST WINDS WILL CONTINUE TO GUST TO AROUND 35 KT THROUGH
EARLY EVENING WITH SNOW SHOWERS HELPING THEM TO OCCUR. EXPECT
GUSTS TO STEADILY DECREASE LATER THIS EVENING INTO THE OVERNIGHT.
MVFR CIGS PERSIST AND SHOULD DO SO OVERNIGHT BUT MAY LIFT A FEW
HUNDRED FEET AT TIMES. LIGHTER WEST WINDS ARE EXPECTED TUESDAY
WITH MVFR STRATUS TO START THE MORNING. HAVE LOW CONFIDENCE IN HOW
LONG MVFR MAY PERSIST OR IF IT LIFTS TO VFR OR SCATTERS AT SOME
POINT DURING THE DAY. WILL LIKELY ENED TO ADJUST THIS WITH LATER
UPDATES.

MDB

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

* HIGH CONFIDENCE IN INTERMITTENT SNOW SHOWERS THROUGH AT LEAST EARLY
  TONIGHT. MEDIUM CONFIDENCE THAT BRIEF IFR VSBY WILL OCCUR AT
  TIMES.

* MEDIUM-HIGH CONIFDENCE THAT THREAT FOR -FZDZ IS LOW AND WOULD BE
  VERY LIGHT INTO MID EVENING IF IT DID OCCUR.

* HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE IN MVFR CIGS PERSISTING TONIGHT WITH LOW
  CONFIDENCE IN HOW LONG THEY MAY LAST TUESDAY.

MDB

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 250004
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
604 PM CST MON NOV 24 2014

.UPDATE...
550 PM CST

HAVE UPDATED FORECAST AND ISSUED SPECIAL WEATHER STATEMENT FOR
PATCHY FREEZING DRIZZLE/LIGHT FREEZING RAIN FOR AREAS SOUTH OF THE
INTERSTATE 80 CORRIDOR EARLY THIS EVENING. REPORTS FROM WFO ILX
INDICATE SEVERAL ACCIDENTS DUE TO LIGHT ICE ACCUMULATION ADJACENT
TO OUR SOUTHWEST COUNTIES.

INDEED...FORECAST SOUNDINGS FROM RAP/NAM RUNS INDICATE MID-LEVEL
DRYING WITH LOW LEVEL MOIST LAYER NOT COLD ENOUGH TO PRODUCE ICE
CRYSTALS AND SNOW FLAKE DEVELOPMENT DESPITE TEMP PROFILES BELOW
FREEZING. THIS MOST APPARENT ACROSS OUR SOUTHERN COUNTIES...THOUGH
SHOWS UP TO A LESSER EXTENT FARTHER NORTH AS WELL. LOOKS LIKE THE
BEST CHANCES FOR FREEZING DRIZZLE/LIGHT FREEZING RAIN WILL BE
ACROSS THE SOUTH...AND THROUGH ABOUT 02Z/8 PM CST BEFORE COLUMN
COOLS A BIT MORE AND DEEPER MOISTURE RETURNS WITH VORT APPROACHING
FROM NORTHEASTERN IA. BY THAT PRECIP SHOULD AGAIN REMAIN LARGELY
SNOW SHOWERS/FLURRIES.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* INTERMITTENT SNOW SHOWERS THROUGH THE OVERNIGHT WITH BRIEF IFR
  VSBY AT TIMES.

* LOW CHANCE FOR SOME PATCHY LIGHT FREEZING DRIZZLE INTO MID
  EVENING.

* WEST-SOUTHWEST WINDS GUSTING AROUND 35 KT THROUGH EARLY EVENING
  THEN GRADUALLY DIMINISH OVERNIGHT.

* MVFR CIGS PERSIST THROUGH TONIGHT AND MAY CONTINUE TOMORROW AS
  WELL.

MDB

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

A SERIES OF UPPER DISTURBANCES WILL CONTINUE TO DRIVE BANDS OF
SNOW SHOWERS INTO THE OVERNIGHT HOURS. MAY SEE A BIT OF A BREAK IN
THE COVERAGE LATE THIS EVENING BUT ANOTHER WAVE COMING ACROSS
NORTHEAST IOWA WILL LIKELY BRING AN INCREASE IN ACTIVITY AROUND
MIDNIGHT INTO THE OVERNIGHT. WILL INDICATE TEMPO IFR VSBY BASED ON
UPSTREAM TRENDS. ACCUMULATION WILL BE LIGHT WITH LESS THAN A HALF
INCH ADDITIONAL EXPECTED.

AM A LITTLE CONCERNED ABOUT SOME LIGHT FREEZING DRIZZLE THIS
EVENING AS WELL AS MOISTURE ALOFT DECREASES FOR A TIME. AREAS
SOUTH OF THE TERMINALS ARE STARTING TO REPORT THIS AND IT IS MORE
FAVORED TO THE SOUTH BUT IT IS POSSIBLE SOME COULD OCCUR AT THE
TERMINALS. POTENTIAL OF OCCURRENCE IS TOO LOW TO INCLUDE IN THE
TAF FOR NOW BUT WILL MONITOR.

WEST-SOUTHWEST WINDS WILL CONTINUE TO GUST TO AROUND 35 KT THROUGH
EARLY EVENING WITH SNOW SHOWERS HELPING THEM TO OCCUR. EXPECT
GUSTS TO STEADILY DECREASE LATER THIS EVENING INTO THE OVERNIGHT.
MVFR CIGS PERSIST AND SHOULD DO SO OVERNIGHT BUT MAY LIFT A FEW
HUNDRED FEET AT TIMES. LIGHTER WEST WINDS ARE EXPECTED TUESDAY
WITH MVFR STRATUS TO START THE MORNING. HAVE LOW CONFIDENCE IN HOW
LONG MVFR MAY PERSIST OR IF IT LIFTS TO VFR OR SCATTERS AT SOME
POINT DURING THE DAY. WILL LIKELY ENED TO ADJUST THIS WITH LATER
UPDATES.

MDB


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

* HIGH CONFIDENCE IN INTERMITTENT SNOW SHOWERS THROUGH AT LEAST EARLY
  TONIGHT. MEDIUM CONFIDENCE THAT BRIEF IFR VSBY WILL OCCUR AT
  TIMES.

* MEDIUM-HIGH CONIFDENCE THAT THREAT FOR -FZDZ IS LOW AND WOULD BE
  VERY LIGHT INTO MID EVENING IF IT DID OCCUR.

* HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE IN MVFR CIGS PERSISTING TONIGHT WITH LOW
  CONFIDENCE IN HOW LONG THEY MAY LAST TUESDAY.

MDB

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL 6 PM MONDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 250004
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
604 PM CST MON NOV 24 2014

.UPDATE...
550 PM CST

HAVE UPDATED FORECAST AND ISSUED SPECIAL WEATHER STATEMENT FOR
PATCHY FREEZING DRIZZLE/LIGHT FREEZING RAIN FOR AREAS SOUTH OF THE
INTERSTATE 80 CORRIDOR EARLY THIS EVENING. REPORTS FROM WFO ILX
INDICATE SEVERAL ACCIDENTS DUE TO LIGHT ICE ACCUMULATION ADJACENT
TO OUR SOUTHWEST COUNTIES.

INDEED...FORECAST SOUNDINGS FROM RAP/NAM RUNS INDICATE MID-LEVEL
DRYING WITH LOW LEVEL MOIST LAYER NOT COLD ENOUGH TO PRODUCE ICE
CRYSTALS AND SNOW FLAKE DEVELOPMENT DESPITE TEMP PROFILES BELOW
FREEZING. THIS MOST APPARENT ACROSS OUR SOUTHERN COUNTIES...THOUGH
SHOWS UP TO A LESSER EXTENT FARTHER NORTH AS WELL. LOOKS LIKE THE
BEST CHANCES FOR FREEZING DRIZZLE/LIGHT FREEZING RAIN WILL BE
ACROSS THE SOUTH...AND THROUGH ABOUT 02Z/8 PM CST BEFORE COLUMN
COOLS A BIT MORE AND DEEPER MOISTURE RETURNS WITH VORT APPROACHING
FROM NORTHEASTERN IA. BY THAT PRECIP SHOULD AGAIN REMAIN LARGELY
SNOW SHOWERS/FLURRIES.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* INTERMITTENT SNOW SHOWERS THROUGH THE OVERNIGHT WITH BRIEF IFR
  VSBY AT TIMES.

* LOW CHANCE FOR SOME PATCHY LIGHT FREEZING DRIZZLE INTO MID
  EVENING.

* WEST-SOUTHWEST WINDS GUSTING AROUND 35 KT THROUGH EARLY EVENING
  THEN GRADUALLY DIMINISH OVERNIGHT.

* MVFR CIGS PERSIST THROUGH TONIGHT AND MAY CONTINUE TOMORROW AS
  WELL.

MDB

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

A SERIES OF UPPER DISTURBANCES WILL CONTINUE TO DRIVE BANDS OF
SNOW SHOWERS INTO THE OVERNIGHT HOURS. MAY SEE A BIT OF A BREAK IN
THE COVERAGE LATE THIS EVENING BUT ANOTHER WAVE COMING ACROSS
NORTHEAST IOWA WILL LIKELY BRING AN INCREASE IN ACTIVITY AROUND
MIDNIGHT INTO THE OVERNIGHT. WILL INDICATE TEMPO IFR VSBY BASED ON
UPSTREAM TRENDS. ACCUMULATION WILL BE LIGHT WITH LESS THAN A HALF
INCH ADDITIONAL EXPECTED.

AM A LITTLE CONCERNED ABOUT SOME LIGHT FREEZING DRIZZLE THIS
EVENING AS WELL AS MOISTURE ALOFT DECREASES FOR A TIME. AREAS
SOUTH OF THE TERMINALS ARE STARTING TO REPORT THIS AND IT IS MORE
FAVORED TO THE SOUTH BUT IT IS POSSIBLE SOME COULD OCCUR AT THE
TERMINALS. POTENTIAL OF OCCURRENCE IS TOO LOW TO INCLUDE IN THE
TAF FOR NOW BUT WILL MONITOR.

WEST-SOUTHWEST WINDS WILL CONTINUE TO GUST TO AROUND 35 KT THROUGH
EARLY EVENING WITH SNOW SHOWERS HELPING THEM TO OCCUR. EXPECT
GUSTS TO STEADILY DECREASE LATER THIS EVENING INTO THE OVERNIGHT.
MVFR CIGS PERSIST AND SHOULD DO SO OVERNIGHT BUT MAY LIFT A FEW
HUNDRED FEET AT TIMES. LIGHTER WEST WINDS ARE EXPECTED TUESDAY
WITH MVFR STRATUS TO START THE MORNING. HAVE LOW CONFIDENCE IN HOW
LONG MVFR MAY PERSIST OR IF IT LIFTS TO VFR OR SCATTERS AT SOME
POINT DURING THE DAY. WILL LIKELY ENED TO ADJUST THIS WITH LATER
UPDATES.

MDB


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

* HIGH CONFIDENCE IN INTERMITTENT SNOW SHOWERS THROUGH AT LEAST EARLY
  TONIGHT. MEDIUM CONFIDENCE THAT BRIEF IFR VSBY WILL OCCUR AT
  TIMES.

* MEDIUM-HIGH CONIFDENCE THAT THREAT FOR -FZDZ IS LOW AND WOULD BE
  VERY LIGHT INTO MID EVENING IF IT DID OCCUR.

* HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE IN MVFR CIGS PERSISTING TONIGHT WITH LOW
  CONFIDENCE IN HOW LONG THEY MAY LAST TUESDAY.

MDB

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

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SOUTH WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

MDB

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL 6 PM MONDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242355
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
555 PM CST MON NOV 24 2014

.UPDATE...
550 PM CST

HAVE UPDATED FORECAST AND ISSUED SPECIAL WEATHER STATEMENT FOR
PATCHY FREEZING DRIZZLE/LIGHT FREEZING RAIN FOR AREAS SOUTH OF THE
INTERSTATE 80 CORRIDOR EARLY THIS EVENING. REPORTS FROM WFO ILX
INDICATE SEVERAL ACCIDENTS DUE TO LIGHT ICE ACCUMULATION ADJACENT
TO OUR SOUTHWEST COUNTIES.

INDEED...FORECAST SOUNDINGS FROM RAP/NAM RUNS INDICATE MID-LEVEL
DRYING WITH LOW LEVEL MOIST LAYER NOT COLD ENOUGH TO PRODUCE ICE
CRYSTALS AND SNOW FLAKE DEVELOPMENT DESPITE TEMP PROFILES BELOW
FREEZING. THIS MOST APPARENT ACROSS OUR SOUTHERN COUNTIES...THOUGH
SHOWS UP TO A LESSER EXTENT FARTHER NORTH AS WELL. LOOKS LIKE THE
BEST CHANCES FOR FREEZING DRIZZLE/LIGHT FREEZING RAIN WILL BE
ACROSS THE SOUTH...AND THROUGH ABOUT 02Z/8 PM CST BEFORE COLUMN
COOLS A BIT MORE AND DEEPER MOISTURE RETURNS WITH VORT APPROACHING
FROM NORTHEASTERN IA. BY THAT PRECIP SHOULD AGAIN REMAIN LARGELY
SNOW SHOWERS/FLURRIES.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* OCCASIONAL SNOW SHOWERS TAPERING TO FLURRIES EARLY EVENING WITH
  ADDITIONAL SNOW SHOWERS POSSIBLE OVERNIGHT.

* MAINLY VFR VSBY BUT INTERMITTENT SNOW SHOWERS MAY REDUCE VSBY TO
  2-4SM.

* MVFR CIGS THROUGH THE NIGHT.

* WEST-SOUTHWEST WINDS GUSTING TO AROUND 35 KT DIMINISHING TO
  25-30 KT EARLY THIS EVENING.

MDB

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

SNOW SHOWERS CONTINUE TO AFFECT THE TERMINALS BRINGING REDUCTION
IN VSBY TO IFR FOR BRIEF PERIODS. IT APPEARS THAT THEY WILL
CONTINUE FOR A FEW HOURS WITH A BREAK OCCURRING THIS EVENING
BEFORE ANOTHER WAVE OVER MINNESOTA ARRIVES TONIGHT BRINGING AT
LEAST SOME CHANCE FOR MORE LIGHT SNOW SHOWERS. WILL TRY TO BETTER
REFLECT THIS IN THE NEXT TAF UPDATE. OTHERWISE WIND GUSTS STILL
PUSHING 35+ KT BUT BECOMING LESS FREQUENT AND THIS GRADUAL DOWN
TREND WILL CONTINUE INTO THE EVENING.

MDB

FROM 18Z...

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN SNOW SHOWERS TAPERING TO FLURRIES INTO EARLY
  EVENING. MEDIUM CONFIDENCE IN SNOW SHOWER POTENTIAL OVERNIGHT.

* HIGH CONFIDENCE IN MAINLY VFR VSBY WITH INTERMITTENT IFR/MVFR IN
  SNOW SHOWERS.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH TONIGHT.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL 6 PM MONDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242355
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
555 PM CST MON NOV 24 2014

.UPDATE...
550 PM CST

HAVE UPDATED FORECAST AND ISSUED SPECIAL WEATHER STATEMENT FOR
PATCHY FREEZING DRIZZLE/LIGHT FREEZING RAIN FOR AREAS SOUTH OF THE
INTERSTATE 80 CORRIDOR EARLY THIS EVENING. REPORTS FROM WFO ILX
INDICATE SEVERAL ACCIDENTS DUE TO LIGHT ICE ACCUMULATION ADJACENT
TO OUR SOUTHWEST COUNTIES.

INDEED...FORECAST SOUNDINGS FROM RAP/NAM RUNS INDICATE MID-LEVEL
DRYING WITH LOW LEVEL MOIST LAYER NOT COLD ENOUGH TO PRODUCE ICE
CRYSTALS AND SNOW FLAKE DEVELOPMENT DESPITE TEMP PROFILES BELOW
FREEZING. THIS MOST APPARENT ACROSS OUR SOUTHERN COUNTIES...THOUGH
SHOWS UP TO A LESSER EXTENT FARTHER NORTH AS WELL. LOOKS LIKE THE
BEST CHANCES FOR FREEZING DRIZZLE/LIGHT FREEZING RAIN WILL BE
ACROSS THE SOUTH...AND THROUGH ABOUT 02Z/8 PM CST BEFORE COLUMN
COOLS A BIT MORE AND DEEPER MOISTURE RETURNS WITH VORT APPROACHING
FROM NORTHEASTERN IA. BY THAT PRECIP SHOULD AGAIN REMAIN LARGELY
SNOW SHOWERS/FLURRIES.

RATZER

&&

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* OCCASIONAL SNOW SHOWERS TAPERING TO FLURRIES EARLY EVENING WITH
  ADDITIONAL SNOW SHOWERS POSSIBLE OVERNIGHT.

* MAINLY VFR VSBY BUT INTERMITTENT SNOW SHOWERS MAY REDUCE VSBY TO
  2-4SM.

* MVFR CIGS THROUGH THE NIGHT.

* WEST-SOUTHWEST WINDS GUSTING TO AROUND 35 KT DIMINISHING TO
  25-30 KT EARLY THIS EVENING.

MDB

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

SNOW SHOWERS CONTINUE TO AFFECT THE TERMINALS BRINGING REDUCTION
IN VSBY TO IFR FOR BRIEF PERIODS. IT APPEARS THAT THEY WILL
CONTINUE FOR A FEW HOURS WITH A BREAK OCCURRING THIS EVENING
BEFORE ANOTHER WAVE OVER MINNESOTA ARRIVES TONIGHT BRINGING AT
LEAST SOME CHANCE FOR MORE LIGHT SNOW SHOWERS. WILL TRY TO BETTER
REFLECT THIS IN THE NEXT TAF UPDATE. OTHERWISE WIND GUSTS STILL
PUSHING 35+ KT BUT BECOMING LESS FREQUENT AND THIS GRADUAL DOWN
TREND WILL CONTINUE INTO THE EVENING.

MDB

FROM 18Z...

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN SNOW SHOWERS TAPERING TO FLURRIES INTO EARLY
  EVENING. MEDIUM CONFIDENCE IN SNOW SHOWER POTENTIAL OVERNIGHT.

* HIGH CONFIDENCE IN MAINLY VFR VSBY WITH INTERMITTENT IFR/MVFR IN
  SNOW SHOWERS.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH TONIGHT.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL 6 PM MONDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242214
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
414 PM CST MON NOV 24 2014

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* OCCASIONAL SNOW SHOWERS TAPERING TO FLURRIES EARLY EVENING WITH
  ADDITIONAL SNOW SHOWERS POSSIBLE OVERNIGHT.

* MAINLY VFR VSBY BUT INTERMITTENT SNOW SHOWERS MAY REDUCE VSBY TO
  2-4SM.

* MVFR CIGS THROUGH THE NIGHT.

* WEST-SOUTHWEST WINDS GUSTING TO AROUND 35 KT DIMINISHING TO
  25-30 KT EARLY THIS EVENING.

MDB

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

SNOW SHOWERS CONTINUE TO AFFECT THE TERMINALS BRINGING REDUCTION
IN VSBY TO IFR FOR BRIEF PERIODS. IT APPEARS THAT THEY WILL
CONTINUE FOR A FEW HOURS WITH A BREAK OCCURRING THIS EVENING
BEFORE ANOTHER WAVE OVER MINNESOTA ARRIVES TONIGHT BRINGING AT
LEAST SOME CHANCE FOR MORE LIGHT SNOW SHOWERS. WILL TRY TO BETTER
REFLECT THIS IN THE NEXT TAF UPDATE. OTHERWISE WIND GUSTS STILL
PUSHING 35+ KT BUT BECOMING LESS FREQUENT AND THIS GRADUAL DOWN
TREND WILL CONTINUE INTO THE EVENING.

MDB

FROM 18Z...

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN SNOW SHOWERS TAPERING TO FLURRIES INTO EARLY
  EVENING. MEDIUM CONFIDENCE IN SNOW SHOWER POTENTIAL OVERNIGHT.

* HIGH CONFIDENCE IN MAINLY VFR VSBY WITH INTERMITTENT IFR/MVFR IN
  SNOW SHOWERS.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH TONIGHT.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL 6 PM MONDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242214
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
414 PM CST MON NOV 24 2014

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

A SECONDARY TROUGH AXIS WILL CROSS THE REGION WEDNESDAY NIGHT...BUT
OUTSIDE OF BULLISH CANADIAN MODEL...LITTLE SUPPORT FOR ANYTHING MORE
THAN SLIGHT POPS. BIG STORY IS GLANCING BLOW OF ARCTIC AIR SENDING
H85 TEMPS INTO THE LOW-MID MINUS TEENS CELSIUS ON THANKSGIVING
DAY...ONLY SUPPORTING HIGHS FROM THE MID 20S TO LOWER 30S...COLDEST
WHERE THERE WILL STILL BE SOME LEFTOVER SNOW COVER. LAKE EFFECT
FOCUS LOOKS TO BE EAST OF OUR NW IN COUNTIES...BUT WILL STILL NEED
TO MONITOR DUE TO FAVORABLE PARAMETERS.

UPPER LEVEL PATTERN CONTINUES TO LOOK TO QUICKLY SHIFT TO MORE ZONAL
ON LATEST GUIDANCE...SUPPORTING A RAPID MODERATING TREND. PRIOR TO
THAT...GUIDANCE DOES BREAK OUT SOME LIGHT WAA PRECIP ON FRIDAY AS AN
UPPER LEVEL WAVE MOVES OVER THE REGION. BETTER FORCING LOOKS TO BE
INTO SOUTHERN WI AT THIS TIME...BUT STILL A WAYS OUT. HAVE INDICATED
SLIGHT POPS FOR LIGHT SNOW...WITH A MIX OR TRANSITION TO RAIN BY
AFTERNOON FOR PARTS OF AREA AS BOUNDARY LAYER WARMS ABOVE FREEZING.
LOW PRESSURE OVER NORTHERN PLAINS LOOKS TO ADVECT IN A MUCH WARMER
AIR MASS ON SOUTHWEST FLOW ON SATURDAY. H85 TEMPS WARMING TO
POSSIBLY UPWARDS OF +10C COULD SPELL READINGS WELL INTO THE 50S (!)
FOR AT LEAST PORTIONS OF AREA IF TRENDS HOLD. DESPITE FLOW REMAINING
ZONAL...SIGNS THAT COLD AIR OVER CANADA AND FAR NORTHERN TIER COULD
TRY TO OOZE SOUTH LATER INTO THE WEEKEND INTO EARLY NEXT WEEK. THIS
WOULD SET UP A BAROCLINIC ZONE AND POSSIBLY LOW PRECIP CHANCES
RETURNING.

RC

&&

.AVIATION...

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

* OCCASIONAL SNOW SHOWERS TAPERING TO FLURRIES EARLY EVENING WITH
  ADDITIONAL SNOW SHOWERS POSSIBLE OVERNIGHT.

* MAINLY VFR VSBY BUT INTERMITTENT SNOW SHOWERS MAY REDUCE VSBY TO
  2-4SM.

* MVFR CIGS THROUGH THE NIGHT.

* WEST-SOUTHWEST WINDS GUSTING TO AROUND 35 KT DIMINISHING TO
  25-30 KT EARLY THIS EVENING.

MDB

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

SNOW SHOWERS CONTINUE TO AFFECT THE TERMINALS BRINGING REDUCTION
IN VSBY TO IFR FOR BRIEF PERIODS. IT APPEARS THAT THEY WILL
CONTINUE FOR A FEW HOURS WITH A BREAK OCCURRING THIS EVENING
BEFORE ANOTHER WAVE OVER MINNESOTA ARRIVES TONIGHT BRINGING AT
LEAST SOME CHANCE FOR MORE LIGHT SNOW SHOWERS. WILL TRY TO BETTER
REFLECT THIS IN THE NEXT TAF UPDATE. OTHERWISE WIND GUSTS STILL
PUSHING 35+ KT BUT BECOMING LESS FREQUENT AND THIS GRADUAL DOWN
TREND WILL CONTINUE INTO THE EVENING.

MDB

FROM 18Z...

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN SNOW SHOWERS TAPERING TO FLURRIES INTO EARLY
  EVENING. MEDIUM CONFIDENCE IN SNOW SHOWER POTENTIAL OVERNIGHT.

* HIGH CONFIDENCE IN MAINLY VFR VSBY WITH INTERMITTENT IFR/MVFR IN
  SNOW SHOWERS.

* HIGH CONFIDENCE IN MVFR CIGS THROUGH TONIGHT.

* HIGH CONFIDENCE IN WIND TRENDS.

MDB

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL 6 PM MONDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242102
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
302 PM CST MON NOV 24 2014

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

TO BE ISSUED SHORTLY.

RC

&&

.AVIATION...

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

* CIGS REMAINING LOW END MVFR.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN THE VSBYS STAYING AT OR ABOVE 3SM.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242102
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
302 PM CST MON NOV 24 2014

.SHORT TERM...
302 PM CST

THROUGH WEDNESDAY...

TONIGHT...

PRIMARY SNOW BAND/DEFORMATION AXIS HAS SHIFTED NORTH BUT
WILL STILL SEE OCCASIONAL SNOW SHOWERS MOVING INTO NORTHERN ILLINOIS
INTO THE EVENING RUSH. SOME OF THESE COULD DROP VISIBILITY DOWN
UNDER 1 MILE AT TIMES...ESPECIALLY AS WINDS CONTINUE TO GUST CLOSE
TO 45 MPH AT TIMES. GOING TO SHIFT END TIME OF ADVISORY FOR
NORTH/NW CWA TO 00Z...WITH THE WIDESPREAD ACCUMULATING SNOW
ALREADY HAVING ENDED. COULD SEE SOME LINGERING LIGHT
SNOW/FLURRIES LATE EVE/OVERNIGHT AS ADDITIONAL UPPER LEVEL ENERGY
TRAVERSES AREA IN CYCLONIC FLOW ALOFT. STRATUS DECK WILL
COUNTERACT LOW LEVEL CAA TO KEEP TEMP FALL IN CHECK TONIGHT...BUT
STILL ANTICIPATING LOW- MID 20S BY DAYBREAK TUESDAY.

TUESDAY/TUES NIGHT...

OTHER THAN POSSIBLY A FEW FLURRIES IN NORTHEAST
IL/NW IN IN THE AM AS SOME LIFT REMAINS OVER THE AREA...LAKE EFFECT
FOCUS WILL LIKELY BE TO OUR EAST WITH WESTERLY FLOW. QUESTION IS
DOES STRATUS ERODE DURING AFTERNOON INTO EVENING. AS IS
TYPICAL...WRF/NAM GUIDANCE IS MOST BULLISH ON LOW LEVEL
MOISTURE...WHILE REMAINDER OF GUIDANCE DOES ENABLE DRY AIR TO MOVE
IN LATE DAY INTO TUESDAY EVENING. CONFIDENCE IS NOT THE
HIGHEST...BUT HAVE TRENDED A BIT MORE OPTIMISTIC WITH CLOUD COVER.
WARM ADVECTION WILL RAMP UP ALOFT IN ADVANCE OF CLIPPER SYSTEM
TOMORROW NIGHT...BUT WITH A TRANSIENT SURFACE RIDGE OVER THE
AREA...CLEAR/PCLOUDY SKIES COULD ENABLE A MORE SIGNIFICANT
TEMPERATURE FALL FROM HIGHS IN THE UPPER 20S-LOW 30S. THIS IS
PARTICULARLY THE CASE FOR AREAS THAT PUT DOWN SNOW COVER TODAY. HAVE
ADJUSTED LOW TEMPS DOWN A FEW DEGREES...TO UPPER TEENS IN NORTHWEST
TO LOW-MID 20S ELSEWHERE.

WEDNESDAY...

DECIDED TREND ON GUIDANCE AND ENSEMBLES TODAY HAS BEEN TO TRACK
CLIPPER MAINLY SOUTH OF THE CWA...AND HAVE ADJUSTED POPS DOWNWARD
CHANCE SOUTHWEST CWA AND SLIGHT CHANCE ELSEWHERE. UPPER LEVEL ENERGY
ASSOCIATED WITH THIS SYSTEM WAS STILL OFF OF THE BRITISH COLUMBIA
COAST AT RAOB TIME. GIVEN TENDENCY FOR LARGE SHIFTS IN THE SHORT
TERM GUIDANCE WITH THE TRACK OF SUBTLE FEATURES SUCH AS
CLIPPERS...HAVE NOT GONE WITH A COMPLETELY DRY FORECAST YET.
HOWEVER...IF TRENDS CONTINUE...ONLY THE FAR SOUTHWEST CWA WOULD SEE
ANY SENSIBLE WX IMPACTS. TEMPS LOOK TO RISE INTO THE LOW-MID
30S...WITH A FEW DEGREES ABOVE THIS POSSIBLE IF CLIPPER TRACKS
COMPLETELY SOUTH OF THE CWA. THIS WILL BE IN ADVANCE OF NEXT SURGE
OF MODIFIED ARCTIC AIR FOR THANKSGIVING DAY.

RC

&&

.LONG TERM...

WEDNESDAY NIGHT THROUGH TUESDAY...

TO BE ISSUED SHORTLY.

RC

&&

.AVIATION...

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

* CIGS REMAINING LOW END MVFR.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN THE VSBYS STAYING AT OR ABOVE 3SM.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242036
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
236 PM CST MON NOV 24 2014

.UPDATE...
1109 AM CST

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* CIGS REMAINING LOW END MVFR.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN THE VSBYS STAYING AT OR ABOVE 3SM.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 242036
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
236 PM CST MON NOV 24 2014

.UPDATE...
1109 AM CST

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* CIGS REMAINING LOW END MVFR.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN THE VSBYS STAYING AT OR ABOVE 3SM.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
235 PM CST

LOW PRESSURE THAT MOVED OVER THE STRAITS THIS MORNING AND DRAGGED A
COLD FRONT ACROSS THE LAKE WILL HAVE LIFTED INTO THE JAMES BAY AREA
LATE THIS EVENING.  STRONG WEST GALES ACROSS THE SOUTH HALF OF THE
LAKE WILL PERSIST INTO THE OVERNIGHT HOURS...WITH GUSTY BUT WEAKER
NORTHWEST WINDS ACROSS THE NORTHERN HALF OF THE LAKE.  SNOW MOVES
OUT TONIGHT EXCEPT FOR LINGERING LAKE EFFECT ALONG THE MICHIGAN
SHORE.

WINDS REMAIN WESTERLY BUT RELAX DURING THE DAY TUESDAY AND THEN
RELAX FURTHER BY WEDNESDAY IN A WEAK AND DISORGANIZED PRESSURE
GRADIENT.  BY WEDNESDAY NIGHT INTO THURSDAY THE PATTERN BECOMES
BETTER ORGANIZED AGAIN AND WINDS PICK UP FROM THE WEST TO NORTH.
WEATHER REMAINS MOSTLY QUIET THIS WEEK AFTER TONIGHT ASIDE FROM A
BRIEF SHOT OF SNOW AGAIN LATE WEDNESDAY AND THE MICHIGAN SIDE LAKE
EFFECT.

LENNING

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
150 PM CST MON NOV 24 2014

.UPDATE...

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* CIGS REMAINING LOW END MVFR.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN THE VSBYS STAYING AT OR ABOVE 3SM.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241950
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
150 PM CST MON NOV 24 2014

.UPDATE...

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* CIGS REMAINING LOW END MVFR.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER

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

* HIGH CONFIDENCE IN THE VSBYS STAYING AT OR ABOVE 3SM.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1207 PM CST MON NOV 24 2014

.UPDATE...1109 AM CST

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* PATCHY IFR CIGS SLOWLY LIFTING TO LOW END MVFR ARND 20Z.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES AFT 00Z.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER


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

* HIGH CONFIDENCE IN THE VSBYS IMPROVING ABOVE 1SM ARND 19Z.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1207 PM CST MON NOV 24 2014

.UPDATE...1109 AM CST

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* PATCHY IFR CIGS SLOWLY LIFTING TO LOW END MVFR ARND 20Z.

* MVFR VSBYS WITH LGT SNOW...LIFTING TO VFR AS SNOW BEGINS TO
  DIMINISH TO FLURRIES AFT 00Z.

* WEST WINDS 20-24KT WITH GUSTS 30-35KT.

BEACHLER

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

RAIN QUICKLY CHANGED OVER TO ALL SNOW LATE THIS MORNING...WITH A
FEW BANDS OF MODERATE SNOW REDUCING VSBYS TO 1/2SM TEMPORARILY AT
ORD/MDW/RFD. BASED ON RADAR TRENDS THE HEAVIEST PRECIP WAS QUICKLY
LIFTING NORTHEAST OF ORD/MDW...AND SHUD ALLOW VSBYS TO RETURN TO
ABOVE 1SM BY 19Z. CIGS WILL REMAIN ARND IFR CONDS...BUT SHUD
IMPROVE TO LOW END MVFR CONDS SHORTLY AFT THE HEAVIER SNOW ENDS.
THEN MVFR CIGS WILL LIKELY PERSIST THRU THIS EVE UNTIL MUCH DRIER
AIR ARRIVES AND CIGS BEGIN TO SCATTER OUT TO BKN DECK
OVERNIGHT/EARLY TUE. WINDS WILL CONTINUE TO BE GUSTY FROM THE
WEST. SUSTAINED WINDS HAVE REMAINED ARND 20-24KT WITH GUSTS
APPROACHING 34-38KT AT TIMES.

AS THE PRESSURE BEGINS TO INCREASE TONIGHT...WINDS WILL STEADILY
DIMINISH BUT REMAIN WESTERLY THROUGH THE OVERNIGHT HOURS. CURRENT
INDICATIONS ARE THAT SCATTERED FLURRIES WILL CONTINUE UNTIL ARND
MIDNIGHT.

BEACHLER


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

* HIGH CONFIDENCE IN THE VSBYS IMPROVING ABOVE 1SM ARND 19Z.

* MEDIUM CONFIDENCE IN TIMING OF CIGS LIFTING FROM LOW END MVFR TO
 VFR CONDS OVERNIGHT.

* HIGH CONFIDENCE IN THE STEADIER HEAVIER SNOW ENDING BEFORE
  20Z...WITH MEDIUM/HIGH CONFIDENCE IN THE ACCUMULATING SNOW
  ENDING BY 23Z.

* LOW CONFIDENCE IN PRECISE ENDING TIME OF LGT SNOW/FLURRIES ARND
  6Z.

* HIGH CONFIDENCE IN WIND DIR/SPEED/GUSTS FORECAST. MEDIUM/HIGH
  CONFIDENCE IN TIMING OF GUSTS ENDING.

BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241709
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1109 AM CST MON NOV 24 2014

.UPDATE...
1109 AM CST

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* WEST WINDS TO 10 KT WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT
  GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* SOME LIGHT ACCUMULATION POSSIBLE...ESPECIALLY AROUND MIDDAY.
  LIGHTER -SHSN CONTINUE INTO THE EVENING WITH SOME ADDITIONAL
  LIGHT ACCUMULATIONS.

* PATCHY IFR TRENDING TO MVFR CIGS.

KMD/BEACHLER

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

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE TSHORTLY WITH INITIAL
PRECIPITATION TYPE AS -RA. EXPECT CIGS TO REMAIN IFR BUT PROBABLY
LIFT SOME AS WEST WINDS BEGIN TO PICK UP WITH LOW PRESSURE MOVING
NORTHEASTWARD WITH -RASN MIX AROUND 15Z AT KRFD AND A FEW HOURS
LATER IN THE CHICAGO AREA...TURNING TO ALL -SN AROUND 18Z OR SO. THE
COLD AIR IS MAKING A GOOD RUN AT THE AREA SO SPED UP THE TIMING TO
TRANSITION TO -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH
AS THE TRANSITION FROM -RA TO -SN OCCURS...SO SOME UNCERTAINTY AS
TO HOW LONG THE MODERATE SNOW WILL LAST THE HIGHEST LIKELIHOOD
FOR ACCUMS IS WEST AND NORTH OF THE MAIN CHICAGO TERMINALS TOWARD
ROCKFORD...BUT SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE
EVERYWHERE..ESPECIALLY IN THE 17Z-20Z TIME FRAME BEFORE THE MAIN
BATCH OF PRECIPITATION SHIFTS NORTHWARD. EXPECT IFR IN THE FIRST
SHOT OF SNOW THEN A TRANSITION TO MVFR WITH LIGHTER SNOW THROUGH
THE AFTERNOON. DURING THIS SAME TIME WINDS WILL BE RAMPING UP WITH
GUSTS TO 30 KT LIKELY...AND POSSIBLY GUSTS TO 35 KT FOR A TIME.

AFTERWARDS...WINDS SLOWLY SUBSIDE...AND THEN A FEW SNOW SHOWERS BUT
MOST LIKELY POSSIBLY JUST FLURRIES OVERNIGHT OR EVEN DRY CONDITIONS
WITH MVFR AND BREEZY WEST WINDS.

KMD

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

* HIGH CONFIDENCE IN WIND SPEED/DIR/GUSTS.

* HIGH CONFIDENCE IN PRECIP TYPE BEING ALL SNOW BY 18Z.

* HIGH CONFIDENCE ON CIG TRENDS.

KMD/BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241709
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1109 AM CST MON NOV 24 2014

.UPDATE...
1109 AM CST

NO CHANGES TO GOING WINTER WEATHER ADVISORY. DUAL POL HAS SHOWN
PROGRESSION OF RAIN/SNOW LINE NICELY THIS MORNING AS COLD AIR HAS
WRAPPED IN FROM SOUTHWEST. HAVE OBSERVED SLUSHY ACCUMULATION ON
PAVEMENT HERE AT OFFICE AND ALSO RECEIVING SIMILAR REPORTS VIA
SPOTTERS AND SOCIAL MEDIA. AS SECONDARY DEFORMATION AXIS LIFTS
NORTH...CONDITIONS WILL LIKELY IMPROVE FOR SOUTHWEST CHI METRO TO
DOWNTOWN WITHIN NEXT ONE TO TWO HOURS. MEANWHILE...WORST OF
CONDITIONS WILL SETTLE INTO FAR NORTHERN IL...INCLUDING NORTH AND
NORTHWEST CHICAGO METRO AND ROCKFORD AREA. GIVEN VISIBILITY IN
HEAVIEST PORTION OF BAND DOWN AROUND 1/4 MILES AS OF 11AM...WIND
AND SNOW ACCUMS ON ROADWAY WILL RESULT IN HAZARDOUS TRAVEL AS
TEMPERATURES CONTINUE TO FALL TO AND BELOW FREEZING. IT APPEARS
SOME PORTIONS OF NORTHWEST/NORTH CENTRAL IL HAVE ALREADY RECEIVED
ONE INCH OR SO OF ACCUMULATION...SO STILL LOOKING AT ACCUMULATIONS
GENERALLY IN THE 2 TO 4 INCH RANGE IN THE ADVISORY AREA.

STRONG WESTERLY WINDS ARE AN ISSUE AREA WIDE...BUT PARTICULARLY IN
SOUTH/SOUTHEAST CWA WHERE MAX 3 HR PRESSURE RISES ~8MB ARE
FOCUSING. EXPECT WIND GUSTS TO 40 TO 45 MPH THROUGH EARLY TO MID
AFTERNOON. WILL HOLD OFF ON ISSUING AN ADVISORY...AS EXPECTING
ONLY SPORADIC GUSTS TO 45 MPH.

RC

&&

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* WEST WINDS TO 10 KT WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT
  GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* SOME LIGHT ACCUMULATION POSSIBLE...ESPECIALLY AROUND MIDDAY.
  LIGHTER -SHSN CONTINUE INTO THE EVENING WITH SOME ADDITIONAL
  LIGHT ACCUMULATIONS.

* PATCHY IFR TRENDING TO MVFR CIGS.

KMD/BEACHLER

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

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE TSHORTLY WITH INITIAL
PRECIPITATION TYPE AS -RA. EXPECT CIGS TO REMAIN IFR BUT PROBABLY
LIFT SOME AS WEST WINDS BEGIN TO PICK UP WITH LOW PRESSURE MOVING
NORTHEASTWARD WITH -RASN MIX AROUND 15Z AT KRFD AND A FEW HOURS
LATER IN THE CHICAGO AREA...TURNING TO ALL -SN AROUND 18Z OR SO. THE
COLD AIR IS MAKING A GOOD RUN AT THE AREA SO SPED UP THE TIMING TO
TRANSITION TO -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH
AS THE TRANSITION FROM -RA TO -SN OCCURS...SO SOME UNCERTAINTY AS
TO HOW LONG THE MODERATE SNOW WILL LAST THE HIGHEST LIKELIHOOD
FOR ACCUMS IS WEST AND NORTH OF THE MAIN CHICAGO TERMINALS TOWARD
ROCKFORD...BUT SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE
EVERYWHERE..ESPECIALLY IN THE 17Z-20Z TIME FRAME BEFORE THE MAIN
BATCH OF PRECIPITATION SHIFTS NORTHWARD. EXPECT IFR IN THE FIRST
SHOT OF SNOW THEN A TRANSITION TO MVFR WITH LIGHTER SNOW THROUGH
THE AFTERNOON. DURING THIS SAME TIME WINDS WILL BE RAMPING UP WITH
GUSTS TO 30 KT LIKELY...AND POSSIBLY GUSTS TO 35 KT FOR A TIME.

AFTERWARDS...WINDS SLOWLY SUBSIDE...AND THEN A FEW SNOW SHOWERS BUT
MOST LIKELY POSSIBLY JUST FLURRIES OVERNIGHT OR EVEN DRY CONDITIONS
WITH MVFR AND BREEZY WEST WINDS.

KMD

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

* HIGH CONFIDENCE IN WIND SPEED/DIR/GUSTS.

* HIGH CONFIDENCE IN PRECIP TYPE BEING ALL SNOW BY 18Z.

* HIGH CONFIDENCE ON CIG TRENDS.

KMD/BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 AM CST MON NOV 24 2014

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* WEST WINDS TO 10 KT WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT
  GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* SOME LIGHT ACCUMULATION POSSIBLE...ESPECIALLY AROUND MIDDAY.
  LIGHTER -SHSN CONTINUE INTO THE EVENING WITH SOME ADDITIONAL
  LIGHT ACCUMULATIONS.

* PATCHY IFR TRENDING TO MVFR CIGS.

KMD/BEACHLER

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

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE TSHORTLY WITH INITIAL
PRECIPITATION TYPE AS -RA. EXPECT CIGS TO REMAIN IFR BUT PROBABLY
LIFT SOME AS WEST WINDS BEGIN TO PICK UP WITH LOW PRESSURE MOVING
NORTHEASTWARD WITH -RASN MIX AROUND 15Z AT KRFD AND A FEW HOURS
LATER IN THE CHICAGO AREA...TURNING TO ALL -SN AROUND 18Z OR SO. THE
COLD AIR IS MAKING A GOOD RUN AT THE AREA SO SPED UP THE TIMING TO
TRANSITION TO -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH
AS THE TRANSITION FROM -RA TO -SN OCCURS...SO SOME UNCERTAINTY AS
TO HOW LONG THE MODERATE SNOW WILL LAST THE HIGHEST LIKELIHOOD
FOR ACCUMS IS WEST AND NORTH OF THE MAIN CHICAGO TERMINALS TOWARD
ROCKFORD...BUT SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE
EVERYWHERE..ESPECIALLY IN THE 17Z-20Z TIME FRAME BEFORE THE MAIN
BATCH OF PRECIPITATION SHIFTS NORTHWARD. EXPECT IFR IN THE FIRST
SHOT OF SNOW THEN A TRANSITION TO MVFR WITH LIGHTER SNOW THROUGH
THE AFTERNOON. DURING THIS SAME TIME WINDS WILL BE RAMPING UP WITH
GUSTS TO 30 KT LIKELY...AND POSSIBLY GUSTS TO 35 KT FOR A TIME.

AFTERWARDS...WINDS SLOWLY SUBSIDE...AND THEN A FEW SNOW SHOWERS BUT
MOST LIKELY POSSIBLY JUST FLURRIES OVERNIGHT OR EVEN DRY CONDITIONS
WITH MVFR AND BREEZY WEST WINDS.

KMD

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

* HIGH CONFIDENCE IN WIND SPEED/DIR/GUSTS.

* HIGH CONFIDENCE IN PRECIP TYPE BEING ALL SNOW BY 18Z.

* HIGH CONFIDENCE ON CIG TRENDS.

KMD/BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241608
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1008 AM CST MON NOV 24 2014

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* WEST WINDS TO 10 KT WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT
  GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* SOME LIGHT ACCUMULATION POSSIBLE...ESPECIALLY AROUND MIDDAY.
  LIGHTER -SHSN CONTINUE INTO THE EVENING WITH SOME ADDITIONAL
  LIGHT ACCUMULATIONS.

* PATCHY IFR TRENDING TO MVFR CIGS.

KMD/BEACHLER

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

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE TSHORTLY WITH INITIAL
PRECIPITATION TYPE AS -RA. EXPECT CIGS TO REMAIN IFR BUT PROBABLY
LIFT SOME AS WEST WINDS BEGIN TO PICK UP WITH LOW PRESSURE MOVING
NORTHEASTWARD WITH -RASN MIX AROUND 15Z AT KRFD AND A FEW HOURS
LATER IN THE CHICAGO AREA...TURNING TO ALL -SN AROUND 18Z OR SO. THE
COLD AIR IS MAKING A GOOD RUN AT THE AREA SO SPED UP THE TIMING TO
TRANSITION TO -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH
AS THE TRANSITION FROM -RA TO -SN OCCURS...SO SOME UNCERTAINTY AS
TO HOW LONG THE MODERATE SNOW WILL LAST THE HIGHEST LIKELIHOOD
FOR ACCUMS IS WEST AND NORTH OF THE MAIN CHICAGO TERMINALS TOWARD
ROCKFORD...BUT SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE
EVERYWHERE..ESPECIALLY IN THE 17Z-20Z TIME FRAME BEFORE THE MAIN
BATCH OF PRECIPITATION SHIFTS NORTHWARD. EXPECT IFR IN THE FIRST
SHOT OF SNOW THEN A TRANSITION TO MVFR WITH LIGHTER SNOW THROUGH
THE AFTERNOON. DURING THIS SAME TIME WINDS WILL BE RAMPING UP WITH
GUSTS TO 30 KT LIKELY...AND POSSIBLY GUSTS TO 35 KT FOR A TIME.

AFTERWARDS...WINDS SLOWLY SUBSIDE...AND THEN A FEW SNOW SHOWERS BUT
MOST LIKELY POSSIBLY JUST FLURRIES OVERNIGHT OR EVEN DRY CONDITIONS
WITH MVFR AND BREEZY WEST WINDS.

KMD

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

* HIGH CONFIDENCE IN WIND SPEED/DIR/GUSTS.

* HIGH CONFIDENCE IN PRECIP TYPE BEING ALL SNOW BY 18Z.

* HIGH CONFIDENCE ON CIG TRENDS.

KMD/BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241408
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
808 AM CST MON NOV 24 2014

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE COMING HOURS AND MAY LOWER TO 500 FT
  AT TIMES.

* STEADIER RAIN RETURNING JUST AFTER DAYBREAK.

* SOUTHWEST WINDS TO 10 KT SHIFT WEST THIS MORNING THEN SOUTHWEST
  WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE
  MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW LATE MORNING..SOME LIGHT ACCUMULATION
  POSSIBLE...ESPECIALLY AROUND MIDDAY. LIGHTER -SHSN CONTINUE INTO
  THE EVENING WITH SOME ADDITIONAL LIGHT ACCUMULATIONS.

* IFR CIGS LIFTING TO MVFR THIS AFTERNOON.

KMD/BEACHLER

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

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE TSHORTLY WITH INITIAL
PRECIPITATION TYPE AS -RA. EXPECT CIGS TO REMAIN IFR BUT PROBABLY
LIFT SOME AS WEST WINDS BEGIN TO PICK UP WITH LOW PRESSURE MOVING
NORTHEASTWARD WITH -RASN MIX AROUND 15Z AT KRFD AND A FEW HOURS
LATER IN THE CHICAGO AREA...TURNING TO ALL -SN AROUND 18Z OR SO. THE
COLD AIR IS MAKING A GOOD RUN AT THE AREA SO SPED UP THE TIMING TO
TRANSITION TO -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH
AS THE TRANSITION FROM -RA TO -SN OCCURS...SO SOME UNCERTAINTY AS
TO HOW LONG THE MODERATE SNOW WILL LAST THE HIGHEST LIKELIHOOD
FOR ACCUMS IS WEST AND NORTH OF THE MAIN CHICAGO TERMINALS TOWARD
ROCKFORD...BUT SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE
EVERYWHERE..ESPECIALLY IN THE 17Z-20Z TIME FRAME BEFORE THE MAIN
BATCH OF PRECIPITATION SHIFTS NORTHWARD. EXPECT IFR IN THE FIRST
SHOT OF SNOW THEN A TRANSITION TO MVFR WITH LIGHTER SNOW THROUGH
THE AFTERNOON. DURING THIS SAME TIME WINDS WILL BE RAMPING UP WITH
GUSTS TO 30 KT LIKELY...AND POSSIBLY GUSTS TO 35 KT FOR A TIME.

AFTERWARDS...WINDS SLOWLY SUBSIDE...AND THEN A FEW SNOW SHOWERS BUT
MOST LIKELY POSSIBLY JUST FLURRIES OVERNIGHT OR EVEN DRY CONDITIONS
WITH MVFR AND BREEZY WEST WINDS.

KMD

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

* HIGH IN IFR CONTINUING WITH SOME LOWERING IN MODERATE RAIN THIS
   MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY HOLDING AT MVFR THOUGH OCCASIONAL
  IFR MIXED IN. MVFR/IFR IN FIRST BATCH OF SNOW.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD/BEACHLER

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012 UNTIL MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM TUESDAY.

&&

$$

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 241142
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
542 AM CST MON NOV 24 2014

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE COMING HOURS AND MAY LOWER TO 500 FT
  AT TIMES.

* STEADIER RAIN RETURNING JUST AFTER DAYBREAK.

* SOUTHWEST WINDS TO 10 KT SHIFT WEST THIS MORNING THEN SOUTHWEST
  WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE
  MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW LATE MORNING..SOME LIGHT ACCUMULATION
  POSSIBLE...ESPECIALLY AROUND MIDDAY. LIGHTER -SHSN CONTINUE INTO
  THE EVENING WITH SOME ADDITIONAL LIGHT ACCUMULATIONS.

* IFR CIGS LIFTING TO MVFR THIS AFTERNOON.

KMD

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

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE TSHORTLY WITH INITIAL
PRECIPITATION TYPE AS -RA. EXPECT CIGS TO REMAIN IFR BUT PROBABLY
LIFT SOME AS WEST WINDS BEGIN TO PICK UP WITH LOW PRESSURE MOVING
NORTHEASTWARD WITH -RASN MIX AROUND 15Z AT KRFD AND A FEW HOURS
LATER IN THE CHICAGO AREA...TURNING TO ALL -SN AROUND 18Z OR SO. THE
COLD AIR IS MAKING A GOOD RUN AT THE AREA SO SPED UP THE TIMING TO
TRANSITION TO -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH
AS THE TRANSITION FROM -RA TO -SN OCCURS...SO SOME UNCERTAINTY AS
TO HOW LONG THE MODERATE SNOW WILL LAST THE HIGHEST LIKELIHOOD
FOR ACCUMS IS WEST AND NORTH OF THE MAIN CHICAGO TERMINALS TOWARD
ROCKFORD...BUT SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE
EVERYWHERE..ESPECIALLY IN THE 17Z-20Z TIME FRAME BEFORE THE MAIN
BATCH OF PRECIPITATION SHIFTS NORTHWARD. EXPECT IFR IN THE FIRST
SHOT OF SNOW THEN A TRANSITION TO MVFR WITH LIGHTER SNOW THROUGH
THE AFTERNOON. DURING THIS SAME TIME WINDS WILL BE RAMPING UP WITH
GUSTS TO 30 KT LIKELY...AND POSSIBLY GUSTS TO 35 KT FOR A TIME.

AFTERWARDS...WINDS SLOWLY SUBSIDE...AND THEN A FEW SNOW SHOWERS BUT
MOST LIKELY POSSIBLY JUST FLURRIES OVERNIGHT OR EVEN DRY CONDITIONS
WITH MVFR AND BREEZY WEST WINDS.

KMD


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

* HIGH IN IFR CONTINUING WITH SOME LOWERING IN MODERATE RAIN THIS
   MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY HOLDING AT MVFR THOUGH OCCASIONAL
  IFR MIXED IN. MVFR/IFR IN FIRST BATCH OF SNOW.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012...9 AM MONDAY TO MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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 241142
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
542 AM CST MON NOV 24 2014

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE COMING HOURS AND MAY LOWER TO 500 FT
  AT TIMES.

* STEADIER RAIN RETURNING JUST AFTER DAYBREAK.

* SOUTHWEST WINDS TO 10 KT SHIFT WEST THIS MORNING THEN SOUTHWEST
  WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE
  MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW LATE MORNING..SOME LIGHT ACCUMULATION
  POSSIBLE...ESPECIALLY AROUND MIDDAY. LIGHTER -SHSN CONTINUE INTO
  THE EVENING WITH SOME ADDITIONAL LIGHT ACCUMULATIONS.

* IFR CIGS LIFTING TO MVFR THIS AFTERNOON.

KMD

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

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE TSHORTLY WITH INITIAL
PRECIPITATION TYPE AS -RA. EXPECT CIGS TO REMAIN IFR BUT PROBABLY
LIFT SOME AS WEST WINDS BEGIN TO PICK UP WITH LOW PRESSURE MOVING
NORTHEASTWARD WITH -RASN MIX AROUND 15Z AT KRFD AND A FEW HOURS
LATER IN THE CHICAGO AREA...TURNING TO ALL -SN AROUND 18Z OR SO. THE
COLD AIR IS MAKING A GOOD RUN AT THE AREA SO SPED UP THE TIMING TO
TRANSITION TO -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH
AS THE TRANSITION FROM -RA TO -SN OCCURS...SO SOME UNCERTAINTY AS
TO HOW LONG THE MODERATE SNOW WILL LAST THE HIGHEST LIKELIHOOD
FOR ACCUMS IS WEST AND NORTH OF THE MAIN CHICAGO TERMINALS TOWARD
ROCKFORD...BUT SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE
EVERYWHERE..ESPECIALLY IN THE 17Z-20Z TIME FRAME BEFORE THE MAIN
BATCH OF PRECIPITATION SHIFTS NORTHWARD. EXPECT IFR IN THE FIRST
SHOT OF SNOW THEN A TRANSITION TO MVFR WITH LIGHTER SNOW THROUGH
THE AFTERNOON. DURING THIS SAME TIME WINDS WILL BE RAMPING UP WITH
GUSTS TO 30 KT LIKELY...AND POSSIBLY GUSTS TO 35 KT FOR A TIME.

AFTERWARDS...WINDS SLOWLY SUBSIDE...AND THEN A FEW SNOW SHOWERS BUT
MOST LIKELY POSSIBLY JUST FLURRIES OVERNIGHT OR EVEN DRY CONDITIONS
WITH MVFR AND BREEZY WEST WINDS.

KMD


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

* HIGH IN IFR CONTINUING WITH SOME LOWERING IN MODERATE RAIN THIS
   MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY HOLDING AT MVFR THOUGH OCCASIONAL
  IFR MIXED IN. MVFR/IFR IN FIRST BATCH OF SNOW.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY NIGHT...VFR.

WEDNESDAY...SCHC SNOW. OTHERWISE VFR. SOUTHEAST TO EAST WINDS.

THURSDAY...A FEW FLURRIES POSSIBLE...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST-SOUTHWEST WINDS.

SUNDAY...VFR. NORTH WINDS.

KMD

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012...9 AM MONDAY TO MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240913
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
313 AM CST MON NOV 24 2014

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 08Z...

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT
  AT TIMES.

* PERIODS OF LIGHT TO MODERATE RAIN OVERNIGHT...THEN STEADIER RAIN RETURNING
  AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT AT TIMES

* SOUTHWEST WINDS TO 10 KT SHIFT WEST MONDAY MORNING THEN SOUTHWEST
  WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE
  MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

//DISCUSSION...UPDATED 08Z...

VSBYS ARE TEMPORARILY RISING AHEAD OF THE NEXT BATCH OF RAIN BUT
EXPECT ADDITIONAL PERIODS OF IFR VSBYS AS THIS MOVES NORTHWARD.
OTHERWISE IFR CIGS CONTINUE THROUGH THE NIGHT...OCCASIONALLY
DROPPING TO 200-300 FEET ANYWHERE IT IS CURRENTLY NOT THAT LOW.

PREVIOUS DISCUSSION FROM 06Z...

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 08Z...

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT AT
  TIMES. LOW- MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012...9 AM MONDAY TO MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240913
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
313 AM CST MON NOV 24 2014

.SHORT TERM...
313 AM CST

THROUGH TONIGHT...

COMPLEX STORM SYSTEM WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH
TONIGHT WITH A TRANSITION FROM MILD AND RAINY TOWARD COLD AND
POTENTIALLY SNOWY LIKELY TO TAKE PLACE LATER THIS MORNING.

DEEPENING SURFACE LOW FROM CENTRAL LAKE MICHIGAN EAST INTO LOWER
MICHIGAN WILL CONTINUE TO LIFT NORTHEAST TODAY AND DEEPEN FURTHER.
COLD FRONT TRAILING THIS BROAD LOW IS CROSSING THE MISSISSIPPI RIVER
NOW AND WILL STEADILY MARCH EAST ACROSS OUR CWA THIS MORNING
RESULTING IN STEADILY FALLING TEMPERATURES FROM THE POINT OF FROPA
THROUGH TONIGHT.

THE PRIMARY DEFORMATION ZONE WITH THIS SYSTEM IS MOVING OUT OF THE
AREA AT THIS TIME...HOWEVER THERE ARE A COUPLE ADDITIONAL VORTICITY
MAXIMA UPSTREAM. THE FIRST WELL DEFINED VORT IS NEAR STL WITH A SLUG
OF RAIN AND EVEN A COUPLE OF ISOLATED THUNDERSTORMS. THIS VORT IS
PROGGED TO SHEAR ENE CENTRAL ILLINOIS INTO NORTHERN OHIO TODAY. A
SECOND VORT MAX IS LOCATED UPSTREAM OVER KANSAS AND PIVOTING AROUND
THE BASE OF THE TROUGH AND EVENTUALLY PHASE WITH THE SHEARING OUT
VORT OVER INDIANA AND OHIO THIS AFTERNOON. AS THIS PROCESS TAKES
PLACE...THE RAIN ASSOCIATED WITH VORT ONE WILL SPREAD NORTHEAST
ACROSS OUR CWA THIS MORNING. AS THE SECOND VORT BEGINS TO PHASE WITH
THE FIRST A ZONE OF MID-LEVEL FRONTOGENESIS WILL DEVELOP ACROSS THE
LOWER LAKES THIS AFTERNOON AND ALLOW PRECIP WITH FIRST VORT TO
MAINTAIN ITSELF AND EVEN DEVELOP UPSTREAM (WESTWARD) INTO FAR
NORTHERN ILLINOIS AND ESPECIALLY INTO SOUTHERN WISCONSIN.

GUIDANCE HAS ALL SHIFTED NORTHWARD WITH THIS PROCESS COMPARED WITH
EARLIER RUNS AND ITS DIFFICULT TO FIND ANY MODEL THAT STILL SUPPORTS
THE 3-5" FORECAST TOTALS WE HAVE GOING IN THE ADVISORY AREA. AM VERY
LEARY ABOUT OVER CORRECTING THINGS SO DID A LOT OF FUZZY MATH AND
FUDGING OF GRIDS TO MAINTAIN AMOUNTS IN THE 2-5" RANGE IN THE
ADVISORY AREA...THOUGH SUSPECT MAJORITY OF THE ADVISORY AREA WILL
END UP WITH TOTALS ON THE BOTTOM END OF THE RANGE. SOUTH OF THE
ADVISORY AREA STILL THINK THERE COULD BE A CHANGEOVER TO SNOW BEFORE
THE DEFORMATION AXIS SHIFTS NORTHWARD AND PRECIP TAPER OFF THIS
AFTERNOON. IF CHANGE OVER ISNT FAST ENOUGH THEN COULD END UP WITH
JUST A TRACE OF SNOW...THOUGH FASTER CHANGE OVER AND BRIEF HEAVIER
INTENSITY COULD SUPPORT AMOUNTS AROUND AN INCH. BEFORE THE ENTIRE
CHANNELED VORT MAX TRANSLATES NORTHEAST OUT OF THE AREA COULD SEE
WESTERN EXTENT OF THE AXIS PIVOT BACK SOUTHWARD A BIT THIS AFTERNOON
INTO OUR NORTHWEST CWA...AND THIS WOULD BE NECESSARY TO GET FORECAST
AMOUNTS.

STRONG WESTERLY WINDS DEVELOP THIS MORNING BEHIND THE COLD FRONT AND
WILL CONTINUE INTO THIS EVENING. THE WINDS WILL WHIP AROUND ANY
FALLING SNOW LEADING TO GREATER REDUCTIONS IN VSBY. IN ADDITION...AS
TEMPS CONTINUE TO FALL FARTHER BELOW FREEZING LATER THIS AFTERNOON
SOME OF THE SNOW ON THE GROUND COULD GET BLOWN AROUND AS SNOW LIKELY
BECOMES MORE POWDERY IN NATURE.

IZZI

&&

.LONG TERM...
313 AM CST

TUESDAY ONWARD...

EXPANSIVE STRATUS DECK LIKELY TO BECOME ESTABLISHED OVER THE AREA
TUESDAY AND WHILE LOW LEVEL FLOW WILL BEGIN TO TRANSITION TO
ANTICYCLONIC TUESDAY AFTERNOON AHEAD OF THE NEXT CLIPPER...NOT SURE
HOW MUCH CLEARING THERE WILL BE AS DRY AIR ADVECTION WILL BE WEAK
WITH DIMINISHING FLOW. IN ADDITION...SUBSIDENCE WILL FURTHER SHARPEN
THE INVERSION CLOUDS ARE TRAPPED BENEATH SO HAVE INCREASED SKY COVER
TUESDAY AND NO LONGER SHOW ANY SUBSTANTIAL CLEARING BEFORE THE MID
WEEK CLIPPER COMES ZIPPING DOWN. GIVEN THE ANTICIPATED CLOUD COVER
HAVE GONE WITH SMALLER DIURNAL TEMP SWINGS WITH CLOUDS PROBABLY
KEEPING TEMPS UP A SMIDGE OVER GUIDANCE AT NIGHT AND A BIT LOWER
DURING THE DAY.

SPEAKING OF THE MID WEEK CLIPPER...GUIDANCE REMAINS INCONSISTENT RUN
TO RUN AND MODEL TO MODEL. THERE HAS BEEN A DISTINCT SOUTHWARD SHIFT
IN GUIDANCE WITH THIS SYSTEM WHICH IF IT WERE TO PAN OUT WOULD PLACE
THE ACCUMULATING SNOW OVER MAINLY OUR SOUTHERN CWA AND POTENTIALLY
BYPASS NORTHERN CWA. THIS CLIPPER IS ORIGINATING AS A PIECE OF
ENERGY BREAKING OFF AN UPPER LOW NEAR THE NORTHERN ALEUTIANS AND
SEEING AS IT HADNT EVEN BROKEN OFF THE LOW AND BEEN WELL SAMPLED YET
AM NOT READY TO THROW MY EGGS IN THE MORE SOUTHERLY TRACK BASKET
JUST YET. BY 12Z WEDNESDAY THE GFS ENSEMBLES HAVE SURFACE LOW
POSITIONS RANGING FROM WESTERN WISCONSIN TO NORTHWEST ARKANSAS...SO
NEEDLESS TO SAY FURTHER CHANGES ARE LIKELY THE NEXT SEVERAL GUIDANCE
CYCLES WITH THIS SYSTEM AND IT IS TOO SOON TO WRITE OFF THE THREAT
OF LIGHT ACCUMULATING SNOW ANYWHERE IN OUR CWA.

ANOTHER INTERESTING TWIST IN THE LATEST MEDIUM RANGE GUIDANCE IS
LESS OF A COLD INTRUSION IN THE WAKE OF THIS CLIPPER FOLLOWED BY A
RAPID TRANSITION TO ZONAL FLOW BY FRIDAY AND INTO THE WEEKEND.
GFS...GEM...AND ECMWF ALL TRACK A SFC LOW OF VARYING STRENGTHS
ACROSS THE UPPER GREAT LAKES SATURDAY PLACING OUR AREA IN WHAT WOULD
BE A VERY MILD SOUTHERLY FLOW. THE 00Z ECMWF THERMAL FIELDS WOULD
SUPPORT HIGHS WELL INTO THE 50S BY SATURDAY...BUT OBVIOUSLY DIDN`T
MAKE THAT DRASTIC OF A CHANGE TO THE GOING FORECAST BUT IF MODELS
REMAIN CONSISTENT WITH THIS LATEST TREND THEN A MILD WEEKEND COULD
BE ON TAP FOR THE REGION.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 08Z...

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT
  AT TIMES.

* PERIODS OF LIGHT TO MODERATE RAIN OVERNIGHT...THEN STEADIER RAIN RETURNING
  AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT AT TIMES

* SOUTHWEST WINDS TO 10 KT SHIFT WEST MONDAY MORNING THEN SOUTHWEST
  WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE
  MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

//DISCUSSION...UPDATED 08Z...

VSBYS ARE TEMPORARILY RISING AHEAD OF THE NEXT BATCH OF RAIN BUT
EXPECT ADDITIONAL PERIODS OF IFR VSBYS AS THIS MOVES NORTHWARD.
OTHERWISE IFR CIGS CONTINUE THROUGH THE NIGHT...OCCASIONALLY
DROPPING TO 200-300 FEET ANYWHERE IT IS CURRENTLY NOT THAT LOW.

PREVIOUS DISCUSSION FROM 06Z...

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 08Z...

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT AT
  TIMES. LOW- MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-
     ILZ010-ILZ011-ILZ012...9 AM MONDAY TO MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
207 AM CST MON NOV 24 2014

.UPDATE...

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 08Z...

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT
  AT TIMES.

* PERIODS OF LIGHT TO MODERATE RAIN OVERNIGHT...THEN STEADIER RAIN RETURNING
  AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT AT TIMES

* SOUTHWEST WINDS TO 10 KT SHIFT WEST MONDAY MORNING THEN SOUTHWEST
  WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE
  MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

//DISCUSSION...UPDATED 08Z...

VSBYS ARE TEMPORARILY RISING AHEAD OF THE NEXT BATCH OF RAIN BUT
EXPECT ADDITIONAL PERIODS OF IFR VSBYS AS THIS MOVES NORTHWARD.
OTHERWISE IFR CIGS CONTINUE THROUGH THE NIGHT...OCCASIONALLY
DROPPING TO 200-300 FEET ANYWHERE IT IS CURRENTLY NOT THAT LOW.

PREVIOUS DISCUSSION FROM 06Z...

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 08Z...

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT AT
  TIMES. LOW- MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240807
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
207 AM CST MON NOV 24 2014

.UPDATE...

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 08Z...

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT
  AT TIMES.

* PERIODS OF LIGHT TO MODERATE RAIN OVERNIGHT...THEN STEADIER RAIN RETURNING
  AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT AT TIMES

* SOUTHWEST WINDS TO 10 KT SHIFT WEST MONDAY MORNING THEN SOUTHWEST
  WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE
  MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

//DISCUSSION...UPDATED 08Z...

VSBYS ARE TEMPORARILY RISING AHEAD OF THE NEXT BATCH OF RAIN BUT
EXPECT ADDITIONAL PERIODS OF IFR VSBYS AS THIS MOVES NORTHWARD.
OTHERWISE IFR CIGS CONTINUE THROUGH THE NIGHT...OCCASIONALLY
DROPPING TO 200-300 FEET ANYWHERE IT IS CURRENTLY NOT THAT LOW.

PREVIOUS DISCUSSION FROM 06Z...

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 08Z...

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT AT
  TIMES. LOW- MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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

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000
FXUS63 KLOT 240755
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
155 AM CST MON NOV 24 2014

.UPDATE...

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT.

* STEADY RAIN TURNS TO DRIZZLE OVERNIGHT WITH STEADIER RAIN
  RETURNING AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT WITH OCCASIONAL VSBY BELOW 3/4SM.
  HIGHER LIKELIHOOD FOR ORD THAN MDW.

* LIGHT/VARIABLE WINDS OVERNIGHT SHIFT WEST MONDAY MORNING THEN
  SOUTHWEST WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS
  POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

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

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD


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

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT. LOW-
  MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM...HIGHER
  CONFIDENCE FOR ORD.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD


&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240755
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
155 AM CST MON NOV 24 2014

.UPDATE...

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT.

* STEADY RAIN TURNS TO DRIZZLE OVERNIGHT WITH STEADIER RAIN
  RETURNING AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT WITH OCCASIONAL VSBY BELOW 3/4SM.
  HIGHER LIKELIHOOD FOR ORD THAN MDW.

* LIGHT/VARIABLE WINDS OVERNIGHT SHIFT WEST MONDAY MORNING THEN
  SOUTHWEST WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS
  POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

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

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD


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

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT. LOW-
  MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM...HIGHER
  CONFIDENCE FOR ORD.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...
154 AM CST

DEEPENING LOW PRESSURE IS PASSING OVER THE LAKE EARLY THIS MORNING
BRINGING A LULL IN WINDS AND WAVES. THE LOW WILL CONTINUE NORTHEAST
INTO SOUTHWEST QUEBEC LATER THIS AFTERNOON THEN REMAIN STEADY AS IT
PUSHES OFFSHORE OVER NOVA SCOTIA. A STRONG SOUTHWEST TO NORTHEAST
ORIENTED PRESSURE GRADIENT WILL REACH THE SOUTH TIP OF THE LAKE BY
15Z...THEN SPREAD OVER THE REMAINDER OF THE LAKE IN THE AFTERNOON.
GALES LOOK SOLID FOR THE SOUTH HALF OF THE THE LAKE...BUT DUE TO A
WEAKENING PRESSURE GRADIENT WITH TIME TODAY AND A MODEST HIGH
BUILDING INTO THE CANADIAN PRARIES AND UPPER MIDWEST...FEEL THAT
WINDS WILL LIKELY PEAK JUST UNDER GALES FOR THE NORTH HALF. A FEW
GALE FORCE GUSTS ARE POSSIBLE...ESPECIALLY LATE AFTERNOON/EARLY
EVENING.

WEAK HIGH PRESSSURE EXTENDING FROM THE NORTH TIP OF LAKE SUPERIOR TO
THE OHIO VALLEY PASSES OVER THE LAKE TUESDAY AFTERNOON. ANOTHER
WEAKENING LOW EMERGING FROM THE CANADIAN ROCKIES WILL PASS JUST
SOUTH OF THE TIP OF LAKE MICHIGAN WITH THE REMNANT INVERTED TROUGH
CLEARING THE LAKE BY THURSDAY MORNING. THIS WILL BE FOLLOWED BY WEAK
HIGH PRESSSURE FOR A FEW DAYS.

KMD


&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240533
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1133 PM CST SUN NOV 23 2014

.UPDATE...832 PM CST

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT.

* STEADY RAIN TURNS TO DRIZZLE OVERNIGHT WITH STEADIER RAIN
  RETURNING AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT WITH OCCASIONAL VSBY BELOW 3/4SM.
  HIGHER LIKELIHOOD FOR ORD THAN MDW.

* LIGHT/VARIABLE WINDS OVERNIGHT SHIFT WEST MONDAY MORNING THEN
  SOUTHWEST WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS
  POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

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

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD


KMD


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

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT. LOW-
  MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM...HIGHER
  CONFIDENCE FOR ORD.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240533
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1133 PM CST SUN NOV 23 2014

.UPDATE...832 PM CST

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT.

* STEADY RAIN TURNS TO DRIZZLE OVERNIGHT WITH STEADIER RAIN
  RETURNING AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT WITH OCCASIONAL VSBY BELOW 3/4SM.
  HIGHER LIKELIHOOD FOR ORD THAN MDW.

* LIGHT/VARIABLE WINDS OVERNIGHT SHIFT WEST MONDAY MORNING THEN
  SOUTHWEST WITH GUSTS TO 30 KT WITH A PERIOD OF 35 KT GUSTS
  POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

* IFR CIGS LIFTING TO MVFR LATE THIS AFTERNOON

KMD

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

BAND OF LIGHT/OCCASIONALLY MODERATE RAIN IS LIFTING NORTHWEST
THROUGH THE TERMINALS EARLY THIS MORNING WITH WIDEPREAD IFR CIGS
AND LARGELY IFR/LIFR VSBYS WITH A SMALL CORRIDOR IN THE SOUTHWEST
FROM KIIK TO KMDW SOUTHEASTWARD. EXPECT VSBYS TO DROP ACROSS THE
AREA AS THE FIRST ROUND OF RAIN DISSIPATES SOME AND LIGHTER WINDS
CONTINUE.

THE NEXT BATCH OF PRECIPIATION IS FORECAST TO MOVE THROUGH JUST
AFTER DAYBREAK WITH INITIAL PRECIPITATION TYPE AS -RA. EXPECT CIGS
TO REMAIN IFR BUT PROBABLY LIFT SOME AS WEST WINDS BEGIN TO PICK
UP WITH LOW PRESSURE MOVING NORTHEASTWARD WITH -RASN MIX AROUND
15Z AT KRFD AND A FEW HOURS LATER IN THE CHICAGO AREA...TURNING TO
ALL -SN. MOISTURE WIL BE DECREASING FROM SOUTH TO NORTH AS THE
TRANSITION FROM -RA TO -SN OCCURS. THE HIGHEST LIKELIHOOD FOR
ACCUMS IS WEST OF THE MAIN CHICAGO TERMINALS TOWARD ROCKFORD...BUT
SOME ACCUMS ARE CERTAINLY STILL PLAUSIBLE EVERYWHERE. LOOKS LIKE A
MIX OF SNOW SHOWERS OR POSSIBLY MORE FLURRIES OVERNIGHT WITH AN
IFR TRANSITION TO MVFR.

KMD


KMD


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

* HIGH IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT. LOW-
  MEDIUM CONFIDENCE IN POTENTIAL TO GO BELOW 1SM...HIGHER
  CONFIDENCE FOR ORD.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

* HIGH CONFIDENCE ON CIG TRENDS...LOW-MEDIUM ON WHEN IFR LIFTS TO
  MVFR AND HOW LONG MVFR LASTS.

KMD

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240313
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
913 PM CST SUN NOV 23 2014

.UPDATE...
832 PM CST

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT.

* STEADY RAIN TURNS TO DRIZZLE OVERNIGHT WITH STEADIER RAIN
  RETURNING AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT. WILL NEED TO MONITOR FOR SUB 1SM
  VSBY.

* SOUTHEAST WINDS TURNING SOUTHWEST OR EVEN LIGHT/VARIABLE LATE
  THIS EVENING.

* WINDS SHIFT WEST MONDAY MORNING THEN SOUTHWEST WITH GUSTS TO 30
  KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

MDB

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

RAIN CONTINUES TO MOVE ACROSS THE TERMINALS WITH BACK EDGE
MARCHING NORTHEAST ACROSS CENTRAL IL. SHOULD SEE FAIRLY STEADY
STATE CONDITIONS FOR A FEW HOURS BEFORE RAIN TRANSITIONS TO
DRIZZLE. WINDS WILL ALSO BE WEAKENING AND BECOMING MORE VARIABLE
FROM THE SOUTH AS LOW PRESSURE MOVES OVER THE AREA. THIS AND THE
DRIZZLE SUGGEST THAT VSBY WILL LOWER AND THIS IS WHAT IS OCCURRING
TO THE WEST SO HAVE LOWERED VSBY SLIGHTLY OVERNIGHT. AREAS OF
1/4-3/4SM ARE NOT OUT OF THE QUESTION SO FURTHER LOWERING MAY BE
NEEDED GOING TOWARD DAYBREAK. OTHERWISE HAVE ADJUSTED TIMING OF
RAIN/SNOW TO SNOW CHANGE OVER BASED ON LATEST TRENDS AND INCOMING
FORECAST GUIDANCE. AM STILL SEEING SUPPORT FOR DECREASING MID
LEVEL MOISTURE MIDDAY/EARLY AFTERNOON SUGGESTING LESS IN THE WAY
OF SNOW COVERAGE FOR A TIME BEFORE ADDITIONAL FORCING AND MOISTURE
PUSH IN LATER IN THE DAY OR EVEN TOWARDS MID EVENING. CONFIDENCE
IN PRECIP TRENDS DURING THE DAY IS STILL LOW BUT INCREASING.
FURTHER ADJUSTMENTS WILL LIKELY BE NEEDED WITH OVERNIGHT UPDATES.

FROM 00Z...

HAVE GOOD CONFIDENCE IN THE FORECAST THROUGH TONIGHT BUT LOWER
CONFIDENCE MONDAY...ESPECIALLY IN TERMS OF RAIN/SNOW TRENDS. LOW
PRESSURE TAKING SHAPE OVER SW MISSOURI THIS EVENING WILL QUICKLY
TRACK NORTHEAST ACROSS THE AREA EARLY TONIGHT. SOUTHEAST WINDS
WILL TURN SOUTHWEST AND PROBABLY DIMINISH IN SPEED AS THE LOW
PASSES SO LIGHT/VARIABLE CONDITIONS MAY OCCUR FOR A TIME
OVERNIGHT. RAIN CONTINUES TO STREAM NORTHWARD ACROSS THE TERMINALS
WITH RFD NEAR THE WESTERN EDGE. DRIER MID LEVEL AIR WILL WRAP IN
INTO THE OVERNIGHT SO A TRANSITION TO LIGHTER RAIN OR JUST DRIZZLE
IS EXPECTED. THIS WILL BE UNDERWAY AT RFD THIS EVENING. IFR CIGS
WILL LOWER SOMEWHAT WITH TIME WHILE VSBY IN THE RAIN VARIES
BETWEEN 2 AND 6SM. DRIZZLE TONIGHT WILL LIKELY ALLOW VSBY TO FALL
TO IFR AND MAY NEED TO CARRY SUB 1SM VSBY FOR A PERIOD.

A SHARP COLD FRONT WORKS ACROSS THE TERMINALS AFTER DAYBREAK
SHIFTING WINDS TO WEST AND ALLOWING THEM TO RAMP UP. GUSTS WILL
PUSH 30 KT BY MID/LATE MORNING WITH 35 KT OR SO POSSIBLE AT TIMES
INTO EARLY AFTERNOON. THE DIRECTION WILL LIKELY BECOME A LITTLE
MORE SOUTHWESTERLY INTO THE AFTERNOON AS WELL. ANOTHER PERIOD OF
PRECIP LOOKS LIKELY DURING THE MORNING INTO MIDDAY WHICH WILL
TRANSITION TO SNOW AS COLDER AIR ARRIVES. LATEST FORECAST GUIDANCE
IS SUGGESTING THAT HIGHER LEVEL MOISTURE WANES DURING THE
AFTERNOON LEADING TO LIGHTER PRECIP OR EVEN MORE DRIZZLE. GUIDANCE
HAS NOT BEEN TERRIBLY CONSISTENT ON DETAILS SO CONFIDENCE IS ON
THE LOW SIDE. EITHER WAY RFD LOOKS TO BE IN LINE FOR THE BEST
PRECIP CHANCES AND WILL CARRY A PERIOD OF MORE INTENSE SNOW DURING
THE LATE MORNING AS THE COLD AIR ARRIVES. ORD/MDW/DPA/GYY WILL SEE
A LATER TRANSITION TO ALL SNOW WITH COVERAGE AND INTENSITY IN
QUESTION. SURFACE AIR TEMPS WILL LIKELY REMAIN ABOVE FREEZING FOR
SEVERAL HOURS BEHIND THE FRONT SO SNOW MAY HAVE A TOUGH TIME
ACCUMULATING UNLESS IT FALLS AT A HIGH RATE...WHICH IS
POSSIBLE...ESPECIALLY AT RFD. OTHERWISE SLUSHY ACCUMULATION IS
POSSIBLE. A DRIER SNOW RATIO WILL DEVELOP INTO THE EVENING AS
TEMPS FALL FURTHER SO ACCUMULATION CHANCES WILL INCREASE AS WILL
THE LIKELIHOOD OF BLOWING SNOW. ANOTHER UPPER TROUGH IS FORECAST TO
MOVE ACROSS DURING THE LATE EVENING OR OVERNIGHT SO LIGHT SNOW
SHOULD OCCUR.

AGAIN...CONFIDENCE IN PRECIP DETAILS IS LOW FOR MONDAY SO BE SURE
TO MONITOR UPCOMING FORECASTS.

MDB

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

* HIGH CONFIDENCE IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT. LOW
  CONFIDENCE IN POTENTIAL TO GO BELOW 1SM.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

MDB

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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

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000
FXUS63 KLOT 240313
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
913 PM CST SUN NOV 23 2014

.UPDATE...
832 PM CST

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT.

* STEADY RAIN TURNS TO DRIZZLE OVERNIGHT WITH STEADIER RAIN
  RETURNING AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT. WILL NEED TO MONITOR FOR SUB 1SM
  VSBY.

* SOUTHEAST WINDS TURNING SOUTHWEST OR EVEN LIGHT/VARIABLE LATE
  THIS EVENING.

* WINDS SHIFT WEST MONDAY MORNING THEN SOUTHWEST WITH GUSTS TO 30
  KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

MDB

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

RAIN CONTINUES TO MOVE ACROSS THE TERMINALS WITH BACK EDGE
MARCHING NORTHEAST ACROSS CENTRAL IL. SHOULD SEE FAIRLY STEADY
STATE CONDITIONS FOR A FEW HOURS BEFORE RAIN TRANSITIONS TO
DRIZZLE. WINDS WILL ALSO BE WEAKENING AND BECOMING MORE VARIABLE
FROM THE SOUTH AS LOW PRESSURE MOVES OVER THE AREA. THIS AND THE
DRIZZLE SUGGEST THAT VSBY WILL LOWER AND THIS IS WHAT IS OCCURRING
TO THE WEST SO HAVE LOWERED VSBY SLIGHTLY OVERNIGHT. AREAS OF
1/4-3/4SM ARE NOT OUT OF THE QUESTION SO FURTHER LOWERING MAY BE
NEEDED GOING TOWARD DAYBREAK. OTHERWISE HAVE ADJUSTED TIMING OF
RAIN/SNOW TO SNOW CHANGE OVER BASED ON LATEST TRENDS AND INCOMING
FORECAST GUIDANCE. AM STILL SEEING SUPPORT FOR DECREASING MID
LEVEL MOISTURE MIDDAY/EARLY AFTERNOON SUGGESTING LESS IN THE WAY
OF SNOW COVERAGE FOR A TIME BEFORE ADDITIONAL FORCING AND MOISTURE
PUSH IN LATER IN THE DAY OR EVEN TOWARDS MID EVENING. CONFIDENCE
IN PRECIP TRENDS DURING THE DAY IS STILL LOW BUT INCREASING.
FURTHER ADJUSTMENTS WILL LIKELY BE NEEDED WITH OVERNIGHT UPDATES.

FROM 00Z...

HAVE GOOD CONFIDENCE IN THE FORECAST THROUGH TONIGHT BUT LOWER
CONFIDENCE MONDAY...ESPECIALLY IN TERMS OF RAIN/SNOW TRENDS. LOW
PRESSURE TAKING SHAPE OVER SW MISSOURI THIS EVENING WILL QUICKLY
TRACK NORTHEAST ACROSS THE AREA EARLY TONIGHT. SOUTHEAST WINDS
WILL TURN SOUTHWEST AND PROBABLY DIMINISH IN SPEED AS THE LOW
PASSES SO LIGHT/VARIABLE CONDITIONS MAY OCCUR FOR A TIME
OVERNIGHT. RAIN CONTINUES TO STREAM NORTHWARD ACROSS THE TERMINALS
WITH RFD NEAR THE WESTERN EDGE. DRIER MID LEVEL AIR WILL WRAP IN
INTO THE OVERNIGHT SO A TRANSITION TO LIGHTER RAIN OR JUST DRIZZLE
IS EXPECTED. THIS WILL BE UNDERWAY AT RFD THIS EVENING. IFR CIGS
WILL LOWER SOMEWHAT WITH TIME WHILE VSBY IN THE RAIN VARIES
BETWEEN 2 AND 6SM. DRIZZLE TONIGHT WILL LIKELY ALLOW VSBY TO FALL
TO IFR AND MAY NEED TO CARRY SUB 1SM VSBY FOR A PERIOD.

A SHARP COLD FRONT WORKS ACROSS THE TERMINALS AFTER DAYBREAK
SHIFTING WINDS TO WEST AND ALLOWING THEM TO RAMP UP. GUSTS WILL
PUSH 30 KT BY MID/LATE MORNING WITH 35 KT OR SO POSSIBLE AT TIMES
INTO EARLY AFTERNOON. THE DIRECTION WILL LIKELY BECOME A LITTLE
MORE SOUTHWESTERLY INTO THE AFTERNOON AS WELL. ANOTHER PERIOD OF
PRECIP LOOKS LIKELY DURING THE MORNING INTO MIDDAY WHICH WILL
TRANSITION TO SNOW AS COLDER AIR ARRIVES. LATEST FORECAST GUIDANCE
IS SUGGESTING THAT HIGHER LEVEL MOISTURE WANES DURING THE
AFTERNOON LEADING TO LIGHTER PRECIP OR EVEN MORE DRIZZLE. GUIDANCE
HAS NOT BEEN TERRIBLY CONSISTENT ON DETAILS SO CONFIDENCE IS ON
THE LOW SIDE. EITHER WAY RFD LOOKS TO BE IN LINE FOR THE BEST
PRECIP CHANCES AND WILL CARRY A PERIOD OF MORE INTENSE SNOW DURING
THE LATE MORNING AS THE COLD AIR ARRIVES. ORD/MDW/DPA/GYY WILL SEE
A LATER TRANSITION TO ALL SNOW WITH COVERAGE AND INTENSITY IN
QUESTION. SURFACE AIR TEMPS WILL LIKELY REMAIN ABOVE FREEZING FOR
SEVERAL HOURS BEHIND THE FRONT SO SNOW MAY HAVE A TOUGH TIME
ACCUMULATING UNLESS IT FALLS AT A HIGH RATE...WHICH IS
POSSIBLE...ESPECIALLY AT RFD. OTHERWISE SLUSHY ACCUMULATION IS
POSSIBLE. A DRIER SNOW RATIO WILL DEVELOP INTO THE EVENING AS
TEMPS FALL FURTHER SO ACCUMULATION CHANCES WILL INCREASE AS WILL
THE LIKELIHOOD OF BLOWING SNOW. ANOTHER UPPER TROUGH IS FORECAST TO
MOVE ACROSS DURING THE LATE EVENING OR OVERNIGHT SO LIGHT SNOW
SHOULD OCCUR.

AGAIN...CONFIDENCE IN PRECIP DETAILS IS LOW FOR MONDAY SO BE SURE
TO MONITOR UPCOMING FORECASTS.

MDB

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

* HIGH CONFIDENCE IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT. LOW
  CONFIDENCE IN POTENTIAL TO GO BELOW 1SM.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

MDB

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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WWW.TWITTER.COM/NWSCHICAGO
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000
FXUS63 KLOT 240313
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
913 PM CST SUN NOV 23 2014

.UPDATE...
832 PM CST

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS PERSIST THROUGH THE NIGHT AND MAY LOWER TO 300-400 FT.

* STEADY RAIN TURNS TO DRIZZLE OVERNIGHT WITH STEADIER RAIN
  RETURNING AFTER DAYBREAK/MID MORNING.

* IFR VSBY LIKELY OVERNIGHT. WILL NEED TO MONITOR FOR SUB 1SM
  VSBY.

* SOUTHEAST WINDS TURNING SOUTHWEST OR EVEN LIGHT/VARIABLE LATE
  THIS EVENING.

* WINDS SHIFT WEST MONDAY MORNING THEN SOUTHWEST WITH GUSTS TO 30
  KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY/EARLY AFTERNOON...SOME LIGHT
  ACCUMULATION POSSIBLE...ESPECIALLY LATER IN THE DAY.

MDB

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

RAIN CONTINUES TO MOVE ACROSS THE TERMINALS WITH BACK EDGE
MARCHING NORTHEAST ACROSS CENTRAL IL. SHOULD SEE FAIRLY STEADY
STATE CONDITIONS FOR A FEW HOURS BEFORE RAIN TRANSITIONS TO
DRIZZLE. WINDS WILL ALSO BE WEAKENING AND BECOMING MORE VARIABLE
FROM THE SOUTH AS LOW PRESSURE MOVES OVER THE AREA. THIS AND THE
DRIZZLE SUGGEST THAT VSBY WILL LOWER AND THIS IS WHAT IS OCCURRING
TO THE WEST SO HAVE LOWERED VSBY SLIGHTLY OVERNIGHT. AREAS OF
1/4-3/4SM ARE NOT OUT OF THE QUESTION SO FURTHER LOWERING MAY BE
NEEDED GOING TOWARD DAYBREAK. OTHERWISE HAVE ADJUSTED TIMING OF
RAIN/SNOW TO SNOW CHANGE OVER BASED ON LATEST TRENDS AND INCOMING
FORECAST GUIDANCE. AM STILL SEEING SUPPORT FOR DECREASING MID
LEVEL MOISTURE MIDDAY/EARLY AFTERNOON SUGGESTING LESS IN THE WAY
OF SNOW COVERAGE FOR A TIME BEFORE ADDITIONAL FORCING AND MOISTURE
PUSH IN LATER IN THE DAY OR EVEN TOWARDS MID EVENING. CONFIDENCE
IN PRECIP TRENDS DURING THE DAY IS STILL LOW BUT INCREASING.
FURTHER ADJUSTMENTS WILL LIKELY BE NEEDED WITH OVERNIGHT UPDATES.

FROM 00Z...

HAVE GOOD CONFIDENCE IN THE FORECAST THROUGH TONIGHT BUT LOWER
CONFIDENCE MONDAY...ESPECIALLY IN TERMS OF RAIN/SNOW TRENDS. LOW
PRESSURE TAKING SHAPE OVER SW MISSOURI THIS EVENING WILL QUICKLY
TRACK NORTHEAST ACROSS THE AREA EARLY TONIGHT. SOUTHEAST WINDS
WILL TURN SOUTHWEST AND PROBABLY DIMINISH IN SPEED AS THE LOW
PASSES SO LIGHT/VARIABLE CONDITIONS MAY OCCUR FOR A TIME
OVERNIGHT. RAIN CONTINUES TO STREAM NORTHWARD ACROSS THE TERMINALS
WITH RFD NEAR THE WESTERN EDGE. DRIER MID LEVEL AIR WILL WRAP IN
INTO THE OVERNIGHT SO A TRANSITION TO LIGHTER RAIN OR JUST DRIZZLE
IS EXPECTED. THIS WILL BE UNDERWAY AT RFD THIS EVENING. IFR CIGS
WILL LOWER SOMEWHAT WITH TIME WHILE VSBY IN THE RAIN VARIES
BETWEEN 2 AND 6SM. DRIZZLE TONIGHT WILL LIKELY ALLOW VSBY TO FALL
TO IFR AND MAY NEED TO CARRY SUB 1SM VSBY FOR A PERIOD.

A SHARP COLD FRONT WORKS ACROSS THE TERMINALS AFTER DAYBREAK
SHIFTING WINDS TO WEST AND ALLOWING THEM TO RAMP UP. GUSTS WILL
PUSH 30 KT BY MID/LATE MORNING WITH 35 KT OR SO POSSIBLE AT TIMES
INTO EARLY AFTERNOON. THE DIRECTION WILL LIKELY BECOME A LITTLE
MORE SOUTHWESTERLY INTO THE AFTERNOON AS WELL. ANOTHER PERIOD OF
PRECIP LOOKS LIKELY DURING THE MORNING INTO MIDDAY WHICH WILL
TRANSITION TO SNOW AS COLDER AIR ARRIVES. LATEST FORECAST GUIDANCE
IS SUGGESTING THAT HIGHER LEVEL MOISTURE WANES DURING THE
AFTERNOON LEADING TO LIGHTER PRECIP OR EVEN MORE DRIZZLE. GUIDANCE
HAS NOT BEEN TERRIBLY CONSISTENT ON DETAILS SO CONFIDENCE IS ON
THE LOW SIDE. EITHER WAY RFD LOOKS TO BE IN LINE FOR THE BEST
PRECIP CHANCES AND WILL CARRY A PERIOD OF MORE INTENSE SNOW DURING
THE LATE MORNING AS THE COLD AIR ARRIVES. ORD/MDW/DPA/GYY WILL SEE
A LATER TRANSITION TO ALL SNOW WITH COVERAGE AND INTENSITY IN
QUESTION. SURFACE AIR TEMPS WILL LIKELY REMAIN ABOVE FREEZING FOR
SEVERAL HOURS BEHIND THE FRONT SO SNOW MAY HAVE A TOUGH TIME
ACCUMULATING UNLESS IT FALLS AT A HIGH RATE...WHICH IS
POSSIBLE...ESPECIALLY AT RFD. OTHERWISE SLUSHY ACCUMULATION IS
POSSIBLE. A DRIER SNOW RATIO WILL DEVELOP INTO THE EVENING AS
TEMPS FALL FURTHER SO ACCUMULATION CHANCES WILL INCREASE AS WILL
THE LIKELIHOOD OF BLOWING SNOW. ANOTHER UPPER TROUGH IS FORECAST TO
MOVE ACROSS DURING THE LATE EVENING OR OVERNIGHT SO LIGHT SNOW
SHOULD OCCUR.

AGAIN...CONFIDENCE IN PRECIP DETAILS IS LOW FOR MONDAY SO BE SURE
TO MONITOR UPCOMING FORECASTS.

MDB

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

* HIGH CONFIDENCE IN IFR CONTINUING WITH SOME LOWERING OVERNIGHT.

* HIGH CONFIDENCE IN STEADIER RAIN DIMINISHING TO DRIZZLE
  OVERNIGHT WITH STEADIER RAIN RETURNING AFTER DAYBREAK/MID
  MORNING.

* MEDIUM-HIGH CONFIDENCE IN VSBY FALLING TO IFR OVERNIGHT. LOW
  CONFIDENCE IN POTENTIAL TO GO BELOW 1SM.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

MDB

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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000
FXUS63 KLOT 240246
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
846 PM CST SUN NOV 23 2014

.UPDATE...
832 PM CST

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILIY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* SLOWLY LOWERING IFR CIGS WITH RAIN THROUGH THE
  EVENING...VARIABLE 2-5SM VSBY. LESS INTENSE RAIN/DRIZZLE
  OVERNIGHT WITH BETTER CHANCE FOR IFR VSBY.

* SOUTHEAST WINDS TURNING SOUTHWEST OR EVEN LIGHT/VARIABLE LATE
  THIS EVENING.

* WINDS SHIFT WEST MONDAY MORNING THEN SOUTHWEST WITH GUSTS TO 30
  KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY...SOME LIGHT ACCUMULATION
  POSSIBLE...ESPECIALLY LATER IN THE DAY.

MDB

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

HAVE GOOD CONFIDENCE IN THE FORECAST THROUGH TONIGHT BUT LOWER
CONFIDENCE MONDAY...ESPECIALLY IN TERMS OF RAIN/SNOW TRENDS. LOW
PRESSURE TAKING SHAPE OVER SW MISSOURI THIS EVENING WILL QUICKLY
TRACK NORTHEAST ACROSS THE AREA EARLY TONIGHT. SOUTHEAST WINDS
WILL TURN SOUTHWEST AND PROBABLY DIMINISH IN SPEED AS THE LOW
PASSES SO LIGHT/VARIABLE CONDITIONS MAY OCCUR FOR A TIME
OVERNIGHT. RAIN CONTINUES TO STREAM NORTHWARD ACROSS THE TERMINALS
WITH RFD NEAR THE WESTERN EDGE. DRIER MID LEVEL AIR WILL WRAP IN
INTO THE OVERNIGHT SO A TRANSITION TO LIGHTER RAIN OR JUST DRIZZLE
IS EXPECTED. THIS WILL BE UNDERWAY AT RFD THIS EVENING. IFR CIGS
WILL LOWER SOMEWHAT WITH TIME WHILE VSBY IN THE RAIN VARIES
BETWEEN 2 AND 6SM. DRIZZLE TONIGHT WILL LIKELY ALLOW VSBY TO FALL
TO IFR AND MAY NEED TO CARRY SUB 1SM VSBY FOR A PERIOD.

A SHARP COLD FRONT WORKS ACROSS THE TERMINALS AFTER DAYBREAK
SHIFTING WINDS TO WEST AND ALLOWING THEM TO RAMP UP. GUSTS WILL
PUSH 30 KT BY MID/LATE MORNING WITH 35 KT OR SO POSSIBLE AT TIMES
INTO EARLY AFTERNOON. THE DIRECTION WILL LIKELY BECOME A LITTLE
MORE SOUTHWESTERLY INTO THE AFTERNOON AS WELL. ANOTHER PERIOD OF
PRECIP LOOKS LIKELY DURING THE MORNING INTO MIDDAY WHICH WILL
TRANSITION TO SNOW AS COLDER AIR ARRIVES. LATEST FORECAST GUIDANCE
IS SUGGESTING THAT HIGHER LEVEL MOISTURE WANES DURING THE
AFTERNOON LEADING TO LIGHTER PRECIP OR EVEN MORE DRIZZLE. GUIDANCE
HAS NOT BEEN TERRIBLY CONSISTENT ON DETAILS SO CONFIDENCE IS ON
THE LOW SIDE. EITHER WAY RFD LOOKS TO BE IN LINE FOR THE BEST
PRECIP CHANCES AND WILL CARRY A PERIOD OF MORE INTENSE SNOW DURING
THE LATE MORNING AS THE COLD AIR ARRIVES. ORD/MDW/DPA/GYY WILL SEE
A LATER TRANSITION TO ALL SNOW WITH COVERAGE AND INTENSITY IN
QUESTION. SURFACE AIR TEMPS WILL LIKELY REMAIN ABOVE FREEZING FOR
SEVERAL HOURS BEHIND THE FRONT SO SNOW MAY HAVE A TOUGH TIME
ACCUMULATING UNLESS IT FALLS AT A HIGH RATE...WHICH IS
POSSIBLE...ESPECIALLY AT RFD. OTHERWISE SLUSHY ACCUMULATION IS
POSSIBLE. A DRIER SNOW RATIO WILL DEVELOP INTO THE EVENING AS
TEMPS FALL FURTHER SO ACCUMULATION CHANCES WILL INCREASE AS WILL
THE LIKELIHOOD OF BLOWING SNOW. ANOTHER UPPER TROUGH IS FORECAST TO
MOVE ACROSS DURING THE LATE EVENING OR OVERNIGHT SO LIGHT SNOW
SHOULD OCCUR.

AGAIN...CONFIDENCE IN PRECIP DETAILS IS LOW FOR MONDAY SO BE SURE
TO MONITOR UPCOMING FORECASTS.

MDB

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

* HIGH CONFIDENCE IN IFR CIGS LOWERING SLIGHTLY THIS EVENING. HIGH
  CONFIDENCE RAIN/DRIZZLE TRENDS THROUGH THE NIGHT. MEDIUM
  CONFIDENCE IN IFR VSBY OVERNIGHT.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

MDB

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
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000
FXUS63 KLOT 240246
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
846 PM CST SUN NOV 23 2014

.UPDATE...
832 PM CST

FOR EVENING UPDATE...

ONLY MINOR ADJUSTMENTS MADE TO GOING FORECAST TONIGHT...PRIMARILIY
TO ADD AREAS OF FOG ALONG THE LAKE AND ACROSS PARTS OF NORTHERN
ILLINOIS OVERNIGHT.

COMPLEX UPPER PATTERN CONTINUES TO EVOLVE ACROSS THE REGION THIS
EVENING AS A SERIES OF MID-LEVEL SHORT WAVES ROTATE THROUGH THE
LARGER-SCALE UPPER TROUGH OVER THE CENTRAL AND EASTERN PARTS OF
NORTH AMERICA. AT THE SURFACE...AN AREA OF LOW PRESSURE WITH A
COUPLE OF INDIVIDUAL LOW CENTERS WAS OVER IL AT 02Z/8 PM CST...
WITH STRONG (6 MB/3 HRS) SURFACE PRESSURE FALLS ACROSS MUCH OF THE
MIDWEST AND SOUTHERN GREAT LAKES REGION. THE LATEST MODEL GUIDANCE
CONTINUES TO CONSOLIDATE A SURFACE LOW OVER FAR NORTHEAST IL OVER
THE NEXT SEVERAL HOURS...LIFTING IT NORTHEAST AND DEEPENING IT
OVERNIGHT AND EARLY MONDAY AS IT PULLS AWAY FROM THE AREA.

REGIONAL RADAR MOSAICS INDICATE A LARGE SHIELD OF RAIN ACROSS THE
EASTERN HALF OF ILLINOIS AND MUCH OF THE GREAT LAKES REGION
PRIMARILY ASSOCIATED WITH A STRONG SHORT WAVE LIFTING NORTHEAST
CROSS THE OHIO VALLEY. ANOTHER AREA OF RAIN AND EMBEDDED THUNDER
WS NOTED BACK ACROSS THE LOWER MISSOURI VALLEY WITH ANOTHER STRONG
WAVE. RAIN MAY TAPER OFF TO OCCASIONAL LIGHT RAIN OR DRIZZLE
ACROSS SOME AREAS WITH A BIT OF A BREAK BETWEEN THE SOLID RAIN
WITH THESE SYSTEMS...THOUGH A PERSISTENT DRIZZLE WILL LIKELY MAKE
IT SEEM LIKE ITS RAINING MOST OF THE TIME ANYWAYS. IN ADDITION TO
THE RAIN...HIGH DEWPOINT AIR WRAPPING NORTHWESTWARD AHEAD OF THE
SURFACE LOW WAS PRODUCING FOG ACROSS SOUTHERN LAKE MICHIGAN WHERE
LAKE WATER TEMPS WERE IN THE MID-40S...AND AFFECTING AREAS ALONG
THE ILLINOIS SHORE. WILL ALSO LIKELY SEE SOME PATCHES OF FOG WHERE
PRECIP DIMINISHES TO DRIZZLE OVERNIGHT...ESPECIALLY IN BAGGY
PRESSURE GRADIENT AND WEAKER WINDS IN VICINITY OF THE SURFACE LOW.

WEST WINDS WILL KICK IN EARLY MONDAY MORNING AS THE LOW PULLS
NORTH AND A COLD FRONT PUSHES EAST ACROSS THE AREA. THIS SHOULD
HELP PUSH SOME OF THE FOG OUT EARLY IN THE MORNING. COLDER AIR AND
WIND GUSTS TO 40 MPH BECOME AN ISSUE DURING THE DAY...ALONG WITH
PRECIPITATION CHANGE FROM LIQUID TO FROZEN AS THE COLUMN COOLS.
POTENTIAL FOR A PERIOD OF MODERATE/LOCALLY HEAVY WET SNOW EXISTS
OVER NORTH CENTRAL/PARTS OF NORTHEAST IL WHERE SOUTHERN PERIPHERY
OF DEFORMATION BAND PASSES. CONFIDENCE NOT SUPER HIGH WITH AMOUNTS
AT THIS POINT...THOUGH NO CHANGES TO WSW HEADLINES AT THIS TIME.

RATZER

&&

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* SLOWLY LOWERING IFR CIGS WITH RAIN THROUGH THE
  EVENING...VARIABLE 2-5SM VSBY. LESS INTENSE RAIN/DRIZZLE
  OVERNIGHT WITH BETTER CHANCE FOR IFR VSBY.

* SOUTHEAST WINDS TURNING SOUTHWEST OR EVEN LIGHT/VARIABLE LATE
  THIS EVENING.

* WINDS SHIFT WEST MONDAY MORNING THEN SOUTHWEST WITH GUSTS TO 30
  KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY...SOME LIGHT ACCUMULATION
  POSSIBLE...ESPECIALLY LATER IN THE DAY.

MDB

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

HAVE GOOD CONFIDENCE IN THE FORECAST THROUGH TONIGHT BUT LOWER
CONFIDENCE MONDAY...ESPECIALLY IN TERMS OF RAIN/SNOW TRENDS. LOW
PRESSURE TAKING SHAPE OVER SW MISSOURI THIS EVENING WILL QUICKLY
TRACK NORTHEAST ACROSS THE AREA EARLY TONIGHT. SOUTHEAST WINDS
WILL TURN SOUTHWEST AND PROBABLY DIMINISH IN SPEED AS THE LOW
PASSES SO LIGHT/VARIABLE CONDITIONS MAY OCCUR FOR A TIME
OVERNIGHT. RAIN CONTINUES TO STREAM NORTHWARD ACROSS THE TERMINALS
WITH RFD NEAR THE WESTERN EDGE. DRIER MID LEVEL AIR WILL WRAP IN
INTO THE OVERNIGHT SO A TRANSITION TO LIGHTER RAIN OR JUST DRIZZLE
IS EXPECTED. THIS WILL BE UNDERWAY AT RFD THIS EVENING. IFR CIGS
WILL LOWER SOMEWHAT WITH TIME WHILE VSBY IN THE RAIN VARIES
BETWEEN 2 AND 6SM. DRIZZLE TONIGHT WILL LIKELY ALLOW VSBY TO FALL
TO IFR AND MAY NEED TO CARRY SUB 1SM VSBY FOR A PERIOD.

A SHARP COLD FRONT WORKS ACROSS THE TERMINALS AFTER DAYBREAK
SHIFTING WINDS TO WEST AND ALLOWING THEM TO RAMP UP. GUSTS WILL
PUSH 30 KT BY MID/LATE MORNING WITH 35 KT OR SO POSSIBLE AT TIMES
INTO EARLY AFTERNOON. THE DIRECTION WILL LIKELY BECOME A LITTLE
MORE SOUTHWESTERLY INTO THE AFTERNOON AS WELL. ANOTHER PERIOD OF
PRECIP LOOKS LIKELY DURING THE MORNING INTO MIDDAY WHICH WILL
TRANSITION TO SNOW AS COLDER AIR ARRIVES. LATEST FORECAST GUIDANCE
IS SUGGESTING THAT HIGHER LEVEL MOISTURE WANES DURING THE
AFTERNOON LEADING TO LIGHTER PRECIP OR EVEN MORE DRIZZLE. GUIDANCE
HAS NOT BEEN TERRIBLY CONSISTENT ON DETAILS SO CONFIDENCE IS ON
THE LOW SIDE. EITHER WAY RFD LOOKS TO BE IN LINE FOR THE BEST
PRECIP CHANCES AND WILL CARRY A PERIOD OF MORE INTENSE SNOW DURING
THE LATE MORNING AS THE COLD AIR ARRIVES. ORD/MDW/DPA/GYY WILL SEE
A LATER TRANSITION TO ALL SNOW WITH COVERAGE AND INTENSITY IN
QUESTION. SURFACE AIR TEMPS WILL LIKELY REMAIN ABOVE FREEZING FOR
SEVERAL HOURS BEHIND THE FRONT SO SNOW MAY HAVE A TOUGH TIME
ACCUMULATING UNLESS IT FALLS AT A HIGH RATE...WHICH IS
POSSIBLE...ESPECIALLY AT RFD. OTHERWISE SLUSHY ACCUMULATION IS
POSSIBLE. A DRIER SNOW RATIO WILL DEVELOP INTO THE EVENING AS
TEMPS FALL FURTHER SO ACCUMULATION CHANCES WILL INCREASE AS WILL
THE LIKELIHOOD OF BLOWING SNOW. ANOTHER UPPER TROUGH IS FORECAST TO
MOVE ACROSS DURING THE LATE EVENING OR OVERNIGHT SO LIGHT SNOW
SHOULD OCCUR.

AGAIN...CONFIDENCE IN PRECIP DETAILS IS LOW FOR MONDAY SO BE SURE
TO MONITOR UPCOMING FORECASTS.

MDB

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

* HIGH CONFIDENCE IN IFR CIGS LOWERING SLIGHTLY THIS EVENING. HIGH
  CONFIDENCE RAIN/DRIZZLE TRENDS THROUGH THE NIGHT. MEDIUM
  CONFIDENCE IN IFR VSBY OVERNIGHT.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

MDB

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240022
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
622 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* SLOWLY LOWERING IFR CIGS WITH RAIN THROUGH THE
  EVENING...VARIABLE 2-5SM VSBY. LESS INTENSE RAIN/DRIZZLE
  OVERNIGHT WITH BETTER CHANCE FOR IFR VSBY.

* SOUTHEAST WINDS TURNING SOUTHWEST OR EVEN LIGHT/VARIABLE LATE
  THIS EVENING.

* WINDS SHIFT WEST MONDAY MORNING THEN SOUTHWEST WITH GUSTS TO 30
  KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY...SOME LIGHT ACCUMULATION
  POSSIBLE...ESPECIALLY LATER IN THE DAY.

MDB

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

HAVE GOOD CONFIDENCE IN THE FORECAST THROUGH TONIGHT BUT LOWER
CONFIDENCE MONDAY...ESPECIALLY IN TERMS OF RAIN/SNOW TRENDS. LOW
PRESSURE TAKING SHAPE OVER SW MISSOURI THIS EVENING WILL QUICKLY
TRACK NORTHEAST ACROSS THE AREA EARLY TONIGHT. SOUTHEAST WINDS
WILL TURN SOUTHWEST AND PROBABLY DIMINISH IN SPEED AS THE LOW
PASSES SO LIGHT/VARIABLE CONDITIONS MAY OCCUR FOR A TIME
OVERNIGHT. RAIN CONTINUES TO STREAM NORTHWARD ACROSS THE TERMINALS
WITH RFD NEAR THE WESTERN EDGE. DRIER MID LEVEL AIR WILL WRAP IN
INTO THE OVERNIGHT SO A TRANSITION TO LIGHTER RAIN OR JUST DRIZZLE
IS EXPECTED. THIS WILL BE UNDERWAY AT RFD THIS EVENING. IFR CIGS
WILL LOWER SOMEWHAT WITH TIME WHILE VSBY IN THE RAIN VARIES
BETWEEN 2 AND 6SM. DRIZZLE TONIGHT WILL LIKELY ALLOW VSBY TO FALL
TO IFR AND MAY NEED TO CARRY SUB 1SM VSBY FOR A PERIOD.

A SHARP COLD FRONT WORKS ACROSS THE TERMINALS AFTER DAYBREAK
SHIFTING WINDS TO WEST AND ALLOWING THEM TO RAMP UP. GUSTS WILL
PUSH 30 KT BY MID/LATE MORNING WITH 35 KT OR SO POSSIBLE AT TIMES
INTO EARLY AFTERNOON. THE DIRECTION WILL LIKELY BECOME A LITTLE
MORE SOUTHWESTERLY INTO THE AFTERNOON AS WELL. ANOTHER PERIOD OF
PRECIP LOOKS LIKELY DURING THE MORNING INTO MIDDAY WHICH WILL
TRANSITION TO SNOW AS COLDER AIR ARRIVES. LATEST FORECAST GUIDANCE
IS SUGGESTING THAT HIGHER LEVEL MOISTURE WANES DURING THE
AFTERNOON LEADING TO LIGHTER PRECIP OR EVEN MORE DRIZZLE. GUIDANCE
HAS NOT BEEN TERRIBLY CONSISTENT ON DETAILS SO CONFIDENCE IS ON
THE LOW SIDE. EITHER WAY RFD LOOKS TO BE IN LINE FOR THE BEST
PRECIP CHANCES AND WILL CARRY A PERIOD OF MORE INTENSE SNOW DURING
THE LATE MORNING AS THE COLD AIR ARRIVES. ORD/MDW/DPA/GYY WILL SEE
A LATER TRANSITION TO ALL SNOW WITH COVERAGE AND INTENSITY IN
QUESTION. SURFACE AIR TEMPS WILL LIKELY REMAIN ABOVE FREEZING FOR
SEVERAL HOURS BEHIND THE FRONT SO SNOW MAY HAVE A TOUGH TIME
ACCUMULATING UNLESS IT FALLS AT A HIGH RATE...WHICH IS
POSSIBLE...ESPECIALLY AT RFD. OTHERWISE SLUSHY ACCUMULATION IS
POSSIBLE. A DRIER SNOW RATIO WILL DEVELOP INTO THE EVENING AS
TEMPS FALL FURTHER SO ACCUMULATION CHANCES WILL INCREASE AS WILL
THE LIKELIHOOD OF BLOWING SNOW. ANOTHER UPPER TROUGH IS FORECAST TO
MOVE ACROSS DURING THE LATE EVENING OR OVERNIGHT SO LIGHT SNOW
SHOULD OCCUR.

AGAIN...CONFIDENCE IN PRECIP DETAILS IS LOW FOR MONDAY SO BE SURE
TO MONITOR UPCOMING FORECASTS.

MDB

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

* HIGH CONFIDENCE IN IFR CIGS LOWERING SLIGHTLY THIS EVENING. HIGH
  CONFIDENCE RAIN/DRIZZLE TRENDS THROUGH THE NIGHT. MEDIUM
  CONFIDENCE IN IFR VSBY OVERNIGHT.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

MDB

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 240022
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
622 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* SLOWLY LOWERING IFR CIGS WITH RAIN THROUGH THE
  EVENING...VARIABLE 2-5SM VSBY. LESS INTENSE RAIN/DRIZZLE
  OVERNIGHT WITH BETTER CHANCE FOR IFR VSBY.

* SOUTHEAST WINDS TURNING SOUTHWEST OR EVEN LIGHT/VARIABLE LATE
  THIS EVENING.

* WINDS SHIFT WEST MONDAY MORNING THEN SOUTHWEST WITH GUSTS TO 30
  KT WITH A PERIOD OF 35 KT GUSTS POSSIBLE MIDDAY/EARLY AFTERNOON.

* RAIN CHANGES TO SNOW MIDDAY...SOME LIGHT ACCUMULATION
  POSSIBLE...ESPECIALLY LATER IN THE DAY.

MDB

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

HAVE GOOD CONFIDENCE IN THE FORECAST THROUGH TONIGHT BUT LOWER
CONFIDENCE MONDAY...ESPECIALLY IN TERMS OF RAIN/SNOW TRENDS. LOW
PRESSURE TAKING SHAPE OVER SW MISSOURI THIS EVENING WILL QUICKLY
TRACK NORTHEAST ACROSS THE AREA EARLY TONIGHT. SOUTHEAST WINDS
WILL TURN SOUTHWEST AND PROBABLY DIMINISH IN SPEED AS THE LOW
PASSES SO LIGHT/VARIABLE CONDITIONS MAY OCCUR FOR A TIME
OVERNIGHT. RAIN CONTINUES TO STREAM NORTHWARD ACROSS THE TERMINALS
WITH RFD NEAR THE WESTERN EDGE. DRIER MID LEVEL AIR WILL WRAP IN
INTO THE OVERNIGHT SO A TRANSITION TO LIGHTER RAIN OR JUST DRIZZLE
IS EXPECTED. THIS WILL BE UNDERWAY AT RFD THIS EVENING. IFR CIGS
WILL LOWER SOMEWHAT WITH TIME WHILE VSBY IN THE RAIN VARIES
BETWEEN 2 AND 6SM. DRIZZLE TONIGHT WILL LIKELY ALLOW VSBY TO FALL
TO IFR AND MAY NEED TO CARRY SUB 1SM VSBY FOR A PERIOD.

A SHARP COLD FRONT WORKS ACROSS THE TERMINALS AFTER DAYBREAK
SHIFTING WINDS TO WEST AND ALLOWING THEM TO RAMP UP. GUSTS WILL
PUSH 30 KT BY MID/LATE MORNING WITH 35 KT OR SO POSSIBLE AT TIMES
INTO EARLY AFTERNOON. THE DIRECTION WILL LIKELY BECOME A LITTLE
MORE SOUTHWESTERLY INTO THE AFTERNOON AS WELL. ANOTHER PERIOD OF
PRECIP LOOKS LIKELY DURING THE MORNING INTO MIDDAY WHICH WILL
TRANSITION TO SNOW AS COLDER AIR ARRIVES. LATEST FORECAST GUIDANCE
IS SUGGESTING THAT HIGHER LEVEL MOISTURE WANES DURING THE
AFTERNOON LEADING TO LIGHTER PRECIP OR EVEN MORE DRIZZLE. GUIDANCE
HAS NOT BEEN TERRIBLY CONSISTENT ON DETAILS SO CONFIDENCE IS ON
THE LOW SIDE. EITHER WAY RFD LOOKS TO BE IN LINE FOR THE BEST
PRECIP CHANCES AND WILL CARRY A PERIOD OF MORE INTENSE SNOW DURING
THE LATE MORNING AS THE COLD AIR ARRIVES. ORD/MDW/DPA/GYY WILL SEE
A LATER TRANSITION TO ALL SNOW WITH COVERAGE AND INTENSITY IN
QUESTION. SURFACE AIR TEMPS WILL LIKELY REMAIN ABOVE FREEZING FOR
SEVERAL HOURS BEHIND THE FRONT SO SNOW MAY HAVE A TOUGH TIME
ACCUMULATING UNLESS IT FALLS AT A HIGH RATE...WHICH IS
POSSIBLE...ESPECIALLY AT RFD. OTHERWISE SLUSHY ACCUMULATION IS
POSSIBLE. A DRIER SNOW RATIO WILL DEVELOP INTO THE EVENING AS
TEMPS FALL FURTHER SO ACCUMULATION CHANCES WILL INCREASE AS WILL
THE LIKELIHOOD OF BLOWING SNOW. ANOTHER UPPER TROUGH IS FORECAST TO
MOVE ACROSS DURING THE LATE EVENING OR OVERNIGHT SO LIGHT SNOW
SHOULD OCCUR.

AGAIN...CONFIDENCE IN PRECIP DETAILS IS LOW FOR MONDAY SO BE SURE
TO MONITOR UPCOMING FORECASTS.

MDB

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

* HIGH CONFIDENCE IN IFR CIGS LOWERING SLIGHTLY THIS EVENING. HIGH
  CONFIDENCE RAIN/DRIZZLE TRENDS THROUGH THE NIGHT. MEDIUM
  CONFIDENCE IN IFR VSBY OVERNIGHT.

* HIGH CONFIDENCE IN WIND TRENDS TONIGHT BUT MEDIUM CONFIDENCE IN
  DIRECTION/SPEED DETAILS.

* HIGH CONFIDENCE IN WIND FORECAST MONDAY AND 30+ KT GUSTS. MEDIUM
  CONFIDENCE IN SPORADICALLY REACHING 35 KT OR SO.

* HIGH CONFIDENCE IN RAIN CHANGING TO SNOW BUT LOW CONFIDENCE IN
  HOW MUCH PRECIP COVERAGE THERE WILL BE THROUGH THE
  AFTERNOON/EVENING.

MDB

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

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
WEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW. SSW WINDS.

SATURDAY...VFR. WEST WINDS.

MDB

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232216
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
416 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* RAIN WITH IFR CIGS AND VARIABLE 2-4SM VSBY THROUGH THE EVENING.
  IFR LOWERS TOWARDS 500 FT EARLY EVENING. LIGHTER RAIN OR DRIZZLE
  AND IFR CIGS/VSBY PERSISTS THROUGH THE NIGHT.

* SOUTHEAST WINDS TURN LIGHT SOUTHWEST OR EVEN VARIABLE LATE THIS
  EVENING.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

MDB

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

NO MAJOR CHANGES IN FORECAST THINKING LATE THIS AFTERNOON WITH IFR
CIGS AND RAIN NOW SPREAD ACROSS THE TERMINALS. VSBY LOOKS TO
FLUCTUATE BETWEEN 2 AND 4SM WITH INTERMITTENT HIGHER VALUES AS
RAIN INTENSITY CHANGES. MOST INTENSE RAIN SHOULD FALL BETWEEN
ABOUT NOW AND MID EVENING. WIND TRENDS REMAIN ON TRACK BUT THERE
MAY BE A PERIOD OF LIGHT AND VARIABLE WINDS AS SURFACE LOW
PRESSURE PASSES NEARBY OR OVERHEAD EARLY TONIGHT.

MDB

FROM 18Z...

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

MDB

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232216
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
416 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* RAIN WITH IFR CIGS AND VARIABLE 2-4SM VSBY THROUGH THE EVENING.
  IFR LOWERS TOWARDS 500 FT EARLY EVENING. LIGHTER RAIN OR DRIZZLE
  AND IFR CIGS/VSBY PERSISTS THROUGH THE NIGHT.

* SOUTHEAST WINDS TURN LIGHT SOUTHWEST OR EVEN VARIABLE LATE THIS
  EVENING.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

MDB

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

NO MAJOR CHANGES IN FORECAST THINKING LATE THIS AFTERNOON WITH IFR
CIGS AND RAIN NOW SPREAD ACROSS THE TERMINALS. VSBY LOOKS TO
FLUCTUATE BETWEEN 2 AND 4SM WITH INTERMITTENT HIGHER VALUES AS
RAIN INTENSITY CHANGES. MOST INTENSE RAIN SHOULD FALL BETWEEN
ABOUT NOW AND MID EVENING. WIND TRENDS REMAIN ON TRACK BUT THERE
MAY BE A PERIOD OF LIGHT AND VARIABLE WINDS AS SURFACE LOW
PRESSURE PASSES NEARBY OR OVERHEAD EARLY TONIGHT.

MDB

FROM 18Z...

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

MDB

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232216
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
416 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* RAIN WITH IFR CIGS AND VARIABLE 2-4SM VSBY THROUGH THE EVENING.
  IFR LOWERS TOWARDS 500 FT EARLY EVENING. LIGHTER RAIN OR DRIZZLE
  AND IFR CIGS/VSBY PERSISTS THROUGH THE NIGHT.

* SOUTHEAST WINDS TURN LIGHT SOUTHWEST OR EVEN VARIABLE LATE THIS
  EVENING.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

MDB

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

NO MAJOR CHANGES IN FORECAST THINKING LATE THIS AFTERNOON WITH IFR
CIGS AND RAIN NOW SPREAD ACROSS THE TERMINALS. VSBY LOOKS TO
FLUCTUATE BETWEEN 2 AND 4SM WITH INTERMITTENT HIGHER VALUES AS
RAIN INTENSITY CHANGES. MOST INTENSE RAIN SHOULD FALL BETWEEN
ABOUT NOW AND MID EVENING. WIND TRENDS REMAIN ON TRACK BUT THERE
MAY BE A PERIOD OF LIGHT AND VARIABLE WINDS AS SURFACE LOW
PRESSURE PASSES NEARBY OR OVERHEAD EARLY TONIGHT.

MDB

FROM 18Z...

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

MDB

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232216
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
416 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* RAIN WITH IFR CIGS AND VARIABLE 2-4SM VSBY THROUGH THE EVENING.
  IFR LOWERS TOWARDS 500 FT EARLY EVENING. LIGHTER RAIN OR DRIZZLE
  AND IFR CIGS/VSBY PERSISTS THROUGH THE NIGHT.

* SOUTHEAST WINDS TURN LIGHT SOUTHWEST OR EVEN VARIABLE LATE THIS
  EVENING.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

MDB

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

NO MAJOR CHANGES IN FORECAST THINKING LATE THIS AFTERNOON WITH IFR
CIGS AND RAIN NOW SPREAD ACROSS THE TERMINALS. VSBY LOOKS TO
FLUCTUATE BETWEEN 2 AND 4SM WITH INTERMITTENT HIGHER VALUES AS
RAIN INTENSITY CHANGES. MOST INTENSE RAIN SHOULD FALL BETWEEN
ABOUT NOW AND MID EVENING. WIND TRENDS REMAIN ON TRACK BUT THERE
MAY BE A PERIOD OF LIGHT AND VARIABLE WINDS AS SURFACE LOW
PRESSURE PASSES NEARBY OR OVERHEAD EARLY TONIGHT.

MDB

FROM 18Z...

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

MDB

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232045
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
245 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232045
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
245 PM CST SUN NOV 23 2014

.SHORT TERM...
244 PM CST

UNSEASONABLY WARM/MOIST AIRMASS CONTINUES TO ADVECT NORTH ACROSS THE
REGION THIS AFTN...AND LOOKS TO CONTINUE THROUGH TONIGHT. THE MAIN
CONCERN FOR THE OVERNIGHT WILL BE ON RAINFALL TOTALS AND IF THIS
WILL POSE ANY HYDRO CONCERNS.

STRONG WARM AIR ADVECTION THIS AFTERNOON HAS ALLOWED SFC TEMPS TO
WARM INTO THE 50S ACROSS MUCH OF THE FORECAST AREA WITH DEW POINTS
APPROACHING THE UPPER 40S/ARND 50. THE AXIS OF THE HEAVIER RAINFALL
THIS AFTN HAS SHIFTED TO THE NORTHWEST AND STRETCHES FROM CENTRAL
WISC SOUTHWEST THROUGH FAR EASTERN IOWA. HAVE NUDGED TEMPS OVERNIGHT
UP A TAD...AND EXPECT TEMPS TO REMAIN NEARLY CONSISTENT UNTIL CLOSER
TO DAYBREAK MON WHEN THE FRONTAL BOUNDARY BEGINS TO APPROACH THE
NORTHWEST CWFA. GUIDANCE CONTINUES TO SUGGEST THE LOW DROPPING
SOUTHEAST ACROSS THE UPPER MIDWEST AND THE SECONDARY ONE LIFTING
NORTH FROM THE SOUTHWEST...WILL CONVERGE ACROSS SOUTHWEST LOWER
MICHIGAN JUST BEFORE DAYBREAK MON. THE COLD FRONT WILL BE NEARING
THE WESTERN CWFA ARND DAYBREAK...AND STEADILY SLIDE EAST THRU THE
MORNING. ASSOCIATED WILL BE A SHARP THERMAL TROUGH THAT WILL CAUSE
TEMPS TO STEADILY FALL THROUGHOUT THE MORNING/AFTN. SO THE DAY MAY
START MILD...BUT BY MIDDAY THAT WILL CERTAINLY NOT BE THE CASE WITH
TEMPS GENERALLY IN THE UPR 20S/LOW 30S. PRECIP WILL BE QUICKLY
TRANSITIONING OVER FROM RAIN TO SNOW.

AS THE SNOW BEGINS MIDDAY ACROSS THE NORTHWEST...GUIDANCE HAS BEEN
RELATIVELY CONSISTENT THAT AT ONSET RATIOS WILL HOVER ARND 8:1 TO
9:1...THEN AS THE COLDER AIR ADVECTS IN THOSE RATIOS SHUD STEADILY
CLIMB TO 14:1-17:1 BY LATE MON AFTN/EARLY EVE. COMPOUNDING THE SETUP
WILL BE STEADILY INCREASING PRESSURE GRADIENT THAT WILL CREATE GUSTY
WINDS NEARING 30-35MPH. THERE IS A NARROW WINDOW WHERE SNOWFALL
RATES COULD NEAR 1-2"/HR FOR A COUPLE HOURS...MAINLY BETWEEN 2-4PM
CST AND MAINLY WEST OF A LASALLE TO CRYSTAL LAKE LINE. HAVE BUMPED
SNOW TOTALS UP TO 2-4" AND COULD SEE IN PORTIONS OF WINNEBAGO COUNTY
3-5" CLOSER TO THE WISC STATELINE IN NORTHERN WINNEBAGO COUNTY.

ELSEWHERE SNOW WILL BEGIN TO ACCUMULATE...BUT EXPECTING MUCH LESS
WITH PERHAPS AN INCH IN CHICAGO AND LESSER TOTALS FURTHER SOUTH.
500MB TROUGH AXIS PIVOTS OVERHEAD MON EVE...AND WILL SLOWLY BRING AN
END TO THE ACCUMULATING SNOW. THE BETTER MOISTURE WILL QUICKLY PEEL
OFF TO THE NORTHEAST LATE MON NGT...HOWEVER ENOUGH OMEGA/MOISTURE TO
KEEP MENTION OF LGT SNOW SHOWERS MON NGT.

OVERNIGHT LOWS MON DIP FALL TO THE LOW 20S TO MID 20S IN THE
SOUTHEAST.

BEACHLER

&&

.LONG TERM...
244 PM CST

TUESDAY THROUGH WEDNESDAY...
LARGE MID-LVL TROUGH WILL BE IN PLACE TUE/WED WITH A WEAK SFC RIDGE
LIFTING NORTH AND BRINGING A GRADUAL EROSION TO THE CLOUDS TUE
NGT/WED. UNFORTUNATELY THIS MAY BE SHORT LIVED AS GUIDANCE SUGGESTS
A QUICK SHORTWAVE WILL DROP SOUTH FROM CENTRAL CANADA INTO THE
NORTHERN PLAINS EARLY WED...AND APPROACH THE FORECAST AREA MIDDAY
WED. THIS SYSTEM COULD BRING ANOTHER PERIOD OF LIGHT SNOW WITH SOME
MINOR ACCUMULATIONS.

TEMPS TUE WILL REMAIN IN THE 20S...HOWEVER WITH SOME THINNING IN THE
CLOUDS FOR WED TEMPS COULD REBOUND INTO THE LOW/MID 30S. BUT IT WILL
HINGE UPON THE ARRIVAL OF THE NEXT MID-LVL WAVE AND CLOUD COVER.

THURSDAY THROUGH SATURDAY...
ENSEMBLES IN THE LONGER TERM CONTINUES TO POINT TOWARDS A TROUGH
CARVED OUT ACROSS THE GREAT LAKES/TENN VALLEY FOR THE SECOND HALF OF
THE WEEK...AND THEN BEGINS TO FLATTEN FOR THE SECOND HALF OF THE
WEEKEND. AT THIS TIME GUIDANCE SUGGESTS DRY AIR AND A SFC RIDGE
OVERHEAD FOR THANKSGIVING DAY. TEMPS WILL GENERALLY BE IN THE 20S
FOR THE BULK OF THE EXTENDED.

BEACHLER

&&

.AVIATION...

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

* IFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER WEATHER ADVISORY...ILZ003-ILZ004-ILZ008-ILZ010-
     ILZ011...NOON MONDAY TO MIDNIGHT TUESDAY.

     WINTER WEATHER ADVISORY...ILZ005-ILZ006-ILZ012...3 PM MONDAY TO
     MIDNIGHT TUESDAY.

IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232037
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* IFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 232037
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
237 PM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* IFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...

237 PM...LOW PRESSURE OVER NORTHERN MINNESOTA WILL CONTINUE TO
WEAKEN AS IT REACHES WESTERN LAKE SUPERIOR THIS EVENING. LOW
PRESSURE OVER OKLAHOMA WILL MOVE NORTHEAST ACROSS THE LAKE TONIGHT
ABSORBING THE WEAKENING LOW OVER LAKE SUPERIOR. THE TRACK OF THIS
LOW HAS CONTINUED TO DRIFT A LITTLE FURTHER EAST WITH EACH RUN AND
THE LOW NOW PASSES EAST OF LAKE SUPERIOR...MOVING OVER EASTERN
ONTARIO MONDAY WITH A PRESSURE NEAR 28.8 INCHES. THIS WILL DELAY
THE ONSET OF GALES BY A FEW HOURS...UNTIL LATE MORNING ACROSS THE
SOUTHERN PART OF THE LAKE AND THEN TO LATE AFTERNOON ACROSS THE
NORTHERN PART. UPGRADED THE GALE WATCH TO A GALE WARNING FOR THE
SOUTH HALF BUT MAINTAINED THE WATCH ACROSS THE NORTHERN HALF.
GALES WILL DIMINISH BY DAYBREAK TUESDAY WITH WINDS STEADILY
DIMINISHING TUESDAY AS HIGH PRESSURE MOVES ACROSS THE SOUTHERN
LAKES AND OHIO VALLEY. ANOTHER LOW WILL MOVE ACROSS THE LAKES
REGION WEDNESDAY AFTERNOON INTO WEDNESDAY NIGHT. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...3 PM MONDAY TO 3 AM TUESDAY.

&&

$$

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 231956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
156 PM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* IFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 231956
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
156 PM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* IFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 231755
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1155 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* MVFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 231755
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1155 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* MVFR CIGS WITH INCREASING SHRA COVERAGE THROUGH THE AFTERNOON.

* MORE WIDESPREAD RAIN BEGINNING LATE AFTERNOON THROUGH THE
  EVENING. IFR CIGS/VIS LIKELY. LIGHTER RAIN OR DRIZZLE PERSISTING
  THROUGH THE NIGHT WITH IFR CONDITIONS CONTINUING.

* WINDS BACKING FROM SOUTH TO SOUTHEAST AND INCREASING TO 12-15 KT
  DURG THE AFTERNOON.

* WINDS VEERING SOUTHWEST TO WEST BY LATE TOMORROW MORNING AND
  INCREASING TO 20G30KT BY AROUND NOON WITH OCCASIONAL HIGHER
  GUSTS POSSIBLE.

* RAIN WILL TRANSITION TO SNOW DURG THE LATE MORNING TO EARLY
  AFTERNOON HOURS...WITH LIGHT SNOW CONTINUING THROUGH THE
  AFTERNOON.

KREIN

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

LATEST RADAR IMAGERY SHOWING AN AREA OF WIDESPREAD RAIN MOVING NWRN
ALG THE MISSISSIPPI RIVER AND OVER NWRN IL...WITH MORE SHOWERY
PCPN OVER NERN IL AND INTO NWRN IN. RFD WILL LIKELY SEE THE STEADY
RAIN INITIALLY...BUT BASED ON THE LATEST RADAR TRENDS...THE MORE
WIDESPREAD...STEADY RAIN SHOULD MOVE INTO THE CHICAGO AREA
TERMINALS THROUGH THE EARLY AFTERNOON HOURS. CIGS HAVE ALREADY
DROPPED TO MVFR AND ANTICIPATE THAT CIGS SHOULD CONTINUE TO LOWER
AS RAIN FALLS THROUGH THE STRATUS LAYER...SATURATING BASES
DOWNWARD AND ALLOWING CIGS TO DROP INTO IFR LEVELS THROUGH THE
AFTERNOON. AS THE STEADIER RAIN AND HIGHER DEWPOINTS CONTINUE TO
STREAM NEWD...VIS WILL BEGIN TO DROP S WELL...INITIALLY TO MVFR
LEVELS THROUGH THE EARLY AFTERNOON AND THEN TO IFR LEVELS BY LATE
AFTERNOON. IFR CONDITIONS SHOULD THEN PERSIST THROUGH THE EVENING
AND OVERNIGHT...AND POSSIBLE EVEN EXTEND THROUGH TOMORROW MORNING.

WINDS WILL START OUT SLY AT THE INITIAL TIME...BUT EXPECT
DIRECTION TO BECOME SELY BY LATE AFTERNOON AS A MID LEVEL IMPULSE
TRACKS NWD AND SFC LOW PRESSURE DEVELOPS OVER MISSOURI LATE
AFTERNOON INTO EARLY EVENING. THE LOW IS EXPECTED TO TRACK INTO
LOWER MICHIGAN BY MONDAY MORNING...CAUSING WINDS TO VEER TO SWLY
DURG THE MORNING HOURS. AN ASSOCIATED COLD FRONT SHOULD PASS
ACROSS THE REGION AS THE SFC LOW MOVES INTO LOWER MICHIGAN...AND
COLDER AIR WILL BEING TO FILTER ACROSS THE REGION THROUGH THE
MORNING AS WINDS CONTINUE TO VEER TO WLY BY EARLY AFTERNOON. THE
INFLUX OF COLDER AIR WILL CAUSE PCPN TO GRADUALLY SHIFT OVER TO A
RAIN/SNOW MIX BY LATE MORNING AND THEN CHANGE OVER TO ALL SNOW BY
ARND NOON. PCPN RATES WILL DECREASE FOLLOWING THE PASSAGE OF THE
COLD FRONT...BUT WINDS WILL QUICKLY INCREASE WITH GUSTS TO 30 KT
OR OR BY AROUND NOON AS WELL. THE COMBINATION OF LIGHT SNOW AND
STRONG WINDS WILL KEEP VIS RESTRICTED TO IFR LEVELS THROUGH MUCH
OF THE DAY TOMORROW.

KREIN

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

* MEDIUM TO HIGH CONFIDENCE IN CIG/VIS TRENDS...BUT LOWER
  CONFIDENCE IN THE EXACT TIMING OF THE TRANSITION FROM MVFR TO
  IFR.

* HIGH CONFIDENCE IN PCPN TRENDS...BUT MEDIUM CONFIDENCE IN THE
  TIMING OF THE TRANSITION FROM PREVAILING RAIN TO PREVAILING
  SNOW.

* HIGH CONFIDENCE IN WIND TRENDS...BUT HAVE SOME CONCERN FOR GUSTS
  HIGHER THAN 30-32KT TOMORROW AFTERNOON.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 231635
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1035 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* CIGS RETURNING TO MVFR OR EARLY AFTERNOON WITH AT LEAST VICINTY
  SHOWERS.

* ANOTHER ROUND OF STEADY RAIN BEGINNING LATE AFTERNOON AND
  CONTINUING THROUGH THE EVENING. IFR CIGS AND VSBYS EXPECTED.
  LIGHTER RAIN OR DRIZZLE OVERNIGHT WITH IFR CONDITIONS
  CONTINUING.

* WINDS BACKING SOUTHEAST AND INCREASING TO 12-15 KT THIS AFTERNOON.

* GUSTY SOUTHWEST TO WEST WINDS AT THE END OF THE CURRENT TAF PERIOD.

* TRANSITION FROM RAIN TO SNOW AT THE END OF THE ORD 30 HR TAF.

KREIN

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

CIGS ARE LIFTING TO VFR BRIEFLY EXCEPT IN THE FAR NORTHWEST NEAR
KRFD. NEXT BATCH OF SHOWERS WILL WORK NORTHWARD IN THE COMING
HOURS WITH A RETURN TO MVFR IN MOST LOCATIONS THROUGH THE MORNING.
AFTER A LULL IN ACTIVITY MIDDAY...MORE WIDESPREAD RAIN WITH
IFR/LIFR CIGS AND VSBYS WILL SPREAD OVER THE REGION BY MID
AFTERNOON AND CONTINUING THROUGH THE EARLY EVENING HOURS. WINDS
WILL SHIFT FROM SOUTHERLY TO SOUTHEASTERLY DURING THIS TIME FRAME
WHILE HOLDING AROUND 10 KT OR SO. EXPECT A SHIFT BACK TO
SOUTHERLY TONIGHT AND EVENTUALLY WESTERLY BY LATE TONIGHT/EARLY
MONDAY.

EXPECT A QUICK TRANSITION TO GUSTY COLD WESTERLY WINDS EARLY
MONDDAY WIH RAIN TRANSITIONING A MIX SOMETIME DURING THE MID-LATE
MORNING TIMEFRAME.

KMD

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

* HIGH ON CONDITIONS RETURNING TO MVFR...MEDIUM ON TIMING AND
  COVERAGE OF PCPN.

* HIGH ON A PERIOD OF RAIN LATE THIS AFTERNOON AND EVENING WITH
  IFR CONDITIONS. MEDIUM ON TIMING OF THE IFR ONSET.

* MEDIUM TO HIGH FOR WIND TRENDS BUT MEDIUM ON SPEEDS.

* HIGH THAT RAIN WILL TRANSITION TO AT LEAST A RAIN SNOW MIX
  SOMETIME MONDAY MORNING...MEDIUM ON TIMING.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 231416
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
816 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* CIGS RETURNING TO MVFR THIS MORNING WITH AT LEAST VICINTY
  SHOWERS.

* ANOTHER ROUND OF STEADY RAIN BEGINNING MID TO LATE AFTERNOON AND
  CONTINUING THROUGH THE EVENING. IFR CIGS AND VSBYS EXPECTED.
  LIGHTER RAIN OR DRIZZLE OVERNIGHT WITH IFR CONDITIONS
  CONTINUING.

* SOUTHEAST WINDS GREATER THAN 10 KT THIS AFTERNOON.

* GUSTY SOUTHWEST TO WEST WINDS AT THE END OF THE CURRENT TAF PERIOD.

* TRANSITION FROM RAIN TO SNOW AT THE END OF THE ORD 30 HR TAF.

KREIN

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

CIGS ARE LIFTING TO VFR BRIEFLY EXCEPT IN THE FAR NORTHWEST NEAR
KRFD. NEXT BATCH OF SHOWERS WILL WORK NORTHWARD IN THE COMING
HOURS WITH A RETURN TO MVFR IN MOST LOCATIONS THROUGH THE MORNING.
AFTER A LULL IN ACTIVITY MIDDAY...MORE WIDESPREAD RAIN WITH
IFR/LIFR CIGS AND VSBYS WILL SPREAD OVER THE REGION BY MID
AFTERNOON AND CONTINUING THROUGH THE EARLY EVENING HOURS. WINDS
WILL SHIFT FROM SOUTHERLY TO SOUTHEASTERLY DURING THIS TIME FRAME
WHILE HOLDING AROUND 10 KT OR SO. EXPECT A SHIFT BACK TO
SOUTHERLY TONIGHT AND EVENTUALLY WESTERLY BY LATE TONIGHT/EARLY
MONDAY.

EXPECT A QUICK TRANSITION TO GUSTY COLD WESTERLY WINDS EARLY
MONDDAY WIH RAIN TRANSITIONING A MIX SOMETIME DURING THE MID-LATE
MORNING TIMEFRAME.

KMD

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

* HIGH ON CONDITIONS RETURNING TO MVFR...MEDIUM ON TIMING AND IF
  ANY SHOWERS WILL OCCUR AT THE TERMINALS THIS MORNING.

* HIGH ON A PERIOD OF AT LEAST MODERATE RAIN THIS AFTERNOON AND
  EVENING WITH IFR/LIFR CONDITIONS. MEDIUM-HIGH ON TIMING AND MEDIUM
  FOR THE IFR ONSET.

* HIGH FOR WIND TRENDS BUT MEDIUM ON SPEEDS.

* HIGH THAT RAIN WILL TRANSITION TO AT LEAST A RAIN SNOW MIX
  SOMETIME MONDAY MORNING...MEDIUM ON TIMING.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 231416
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
816 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* CIGS RETURNING TO MVFR THIS MORNING WITH AT LEAST VICINTY
  SHOWERS.

* ANOTHER ROUND OF STEADY RAIN BEGINNING MID TO LATE AFTERNOON AND
  CONTINUING THROUGH THE EVENING. IFR CIGS AND VSBYS EXPECTED.
  LIGHTER RAIN OR DRIZZLE OVERNIGHT WITH IFR CONDITIONS
  CONTINUING.

* SOUTHEAST WINDS GREATER THAN 10 KT THIS AFTERNOON.

* GUSTY SOUTHWEST TO WEST WINDS AT THE END OF THE CURRENT TAF PERIOD.

* TRANSITION FROM RAIN TO SNOW AT THE END OF THE ORD 30 HR TAF.

KREIN

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

CIGS ARE LIFTING TO VFR BRIEFLY EXCEPT IN THE FAR NORTHWEST NEAR
KRFD. NEXT BATCH OF SHOWERS WILL WORK NORTHWARD IN THE COMING
HOURS WITH A RETURN TO MVFR IN MOST LOCATIONS THROUGH THE MORNING.
AFTER A LULL IN ACTIVITY MIDDAY...MORE WIDESPREAD RAIN WITH
IFR/LIFR CIGS AND VSBYS WILL SPREAD OVER THE REGION BY MID
AFTERNOON AND CONTINUING THROUGH THE EARLY EVENING HOURS. WINDS
WILL SHIFT FROM SOUTHERLY TO SOUTHEASTERLY DURING THIS TIME FRAME
WHILE HOLDING AROUND 10 KT OR SO. EXPECT A SHIFT BACK TO
SOUTHERLY TONIGHT AND EVENTUALLY WESTERLY BY LATE TONIGHT/EARLY
MONDAY.

EXPECT A QUICK TRANSITION TO GUSTY COLD WESTERLY WINDS EARLY
MONDDAY WIH RAIN TRANSITIONING A MIX SOMETIME DURING THE MID-LATE
MORNING TIMEFRAME.

KMD

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

* HIGH ON CONDITIONS RETURNING TO MVFR...MEDIUM ON TIMING AND IF
  ANY SHOWERS WILL OCCUR AT THE TERMINALS THIS MORNING.

* HIGH ON A PERIOD OF AT LEAST MODERATE RAIN THIS AFTERNOON AND
  EVENING WITH IFR/LIFR CONDITIONS. MEDIUM-HIGH ON TIMING AND MEDIUM
  FOR THE IFR ONSET.

* HIGH FOR WIND TRENDS BUT MEDIUM ON SPEEDS.

* HIGH THAT RAIN WILL TRANSITION TO AT LEAST A RAIN SNOW MIX
  SOMETIME MONDAY MORNING...MEDIUM ON TIMING.

KREIN

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 231145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
545 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* CIGS RETURNING TO MVFR THIS MORNING WITH AT LEAST VICINTY
  SHOWERS.

* ANOTHER ROUND OF STEADY RAIN BEGINNING MID TO LATE AFTERNOON AND
  CONTINUING THROUGH THE EVENING. IFR CIGS AND VSBYS EXPECTED.
  LIGHTER RAIN OR DRIZZLE OVERNIGHT WITH IFR CONDITIONS
  CONTINUING.

* SOUTHEAST WINDS GREATER THAN 10 KT THIS AFTERNOON.

* GUSTY SOUTHWEST TO WEST WINDS AT THE END OF THE CURRENT TAF PERIOD.

* TRANSITION FROM RAIN TO SNOW AT THE END OF THE ORD 30 HR TAF.

KMD

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

CIGS ARE LIFTING TO VFR BRIEFLY EXCEPT IN THE FAR NORTHWEST NEAR
KRFD. NEXT BATCH OF SHOWERS WILL WORK NORTHWARD IN THE COMING
HOURS WITH A RETURN TO MVFR IN MOST LOCATIONS THROUGH THE MORNING.
AFTER A LULL IN ACTIVITY MIDDAY...MORE WIDESPREAD RAIN WITH
IFR/LIFR CIGS AND VSBYS WILL SPREAD OVER THE REGION BY MID
AFTERNOON AND CONTINUING THROUGH THE EARLY EVENING HOURS. WINDS
WILL SHIFT FROM SOUTHERLY TO SOUTHEASTERLY DURING THIS TIME FRAME
WHILE HOLDING AROUND 10 KT OR SO. EXPECT A SHIFT BACK TO
SOUTHERLY TONIGHT AND EVENTUALLY WESTERLY BY LATE TONIGHT/EARLY
MONDAY.


EXPECT A QUICK TRANSITION TO GUSTY COLD WESTERLY WINDS EARLY
MONDDAY WIH RAIN TRANSITIONING A MIX SOMETIME DURING THE MID-LATE
MORNING TIMEFRAME.

KMD


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

* HIGH ON CONDITIONS RETURNING TO MVFR...MEDIUM ON TIMING AND IF
  ANY SHOWERS WILL OCCUR AT THE TERMINALS THIS MORNING.

* HIGH ON A PERIOD OF AT LEAST MODERATE RAIN THIS AFTERNOON AND
  EVENING WITH IFR/LIFR CONDITIONS. MEDIUM-HIGH ON TIMING AND MEDIUM
  FOR THE IFR ONSET.

* HIGH FOR WIND TRENDS BUT MEDIUM ON SPEEDS.

* HIGH THAT RAIN WILL TRANSITION TO AT LEAST A RAIN SNOW MIX
  SOMETIME MONDAY MORNING...MEDIUM ON TIMING.


KMD

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 231145
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
545 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* CIGS RETURNING TO MVFR THIS MORNING WITH AT LEAST VICINTY
  SHOWERS.

* ANOTHER ROUND OF STEADY RAIN BEGINNING MID TO LATE AFTERNOON AND
  CONTINUING THROUGH THE EVENING. IFR CIGS AND VSBYS EXPECTED.
  LIGHTER RAIN OR DRIZZLE OVERNIGHT WITH IFR CONDITIONS
  CONTINUING.

* SOUTHEAST WINDS GREATER THAN 10 KT THIS AFTERNOON.

* GUSTY SOUTHWEST TO WEST WINDS AT THE END OF THE CURRENT TAF PERIOD.

* TRANSITION FROM RAIN TO SNOW AT THE END OF THE ORD 30 HR TAF.

KMD

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

CIGS ARE LIFTING TO VFR BRIEFLY EXCEPT IN THE FAR NORTHWEST NEAR
KRFD. NEXT BATCH OF SHOWERS WILL WORK NORTHWARD IN THE COMING
HOURS WITH A RETURN TO MVFR IN MOST LOCATIONS THROUGH THE MORNING.
AFTER A LULL IN ACTIVITY MIDDAY...MORE WIDESPREAD RAIN WITH
IFR/LIFR CIGS AND VSBYS WILL SPREAD OVER THE REGION BY MID
AFTERNOON AND CONTINUING THROUGH THE EARLY EVENING HOURS. WINDS
WILL SHIFT FROM SOUTHERLY TO SOUTHEASTERLY DURING THIS TIME FRAME
WHILE HOLDING AROUND 10 KT OR SO. EXPECT A SHIFT BACK TO
SOUTHERLY TONIGHT AND EVENTUALLY WESTERLY BY LATE TONIGHT/EARLY
MONDAY.


EXPECT A QUICK TRANSITION TO GUSTY COLD WESTERLY WINDS EARLY
MONDDAY WIH RAIN TRANSITIONING A MIX SOMETIME DURING THE MID-LATE
MORNING TIMEFRAME.

KMD


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

* HIGH ON CONDITIONS RETURNING TO MVFR...MEDIUM ON TIMING AND IF
  ANY SHOWERS WILL OCCUR AT THE TERMINALS THIS MORNING.

* HIGH ON A PERIOD OF AT LEAST MODERATE RAIN THIS AFTERNOON AND
  EVENING WITH IFR/LIFR CONDITIONS. MEDIUM-HIGH ON TIMING AND MEDIUM
  FOR THE IFR ONSET.

* HIGH FOR WIND TRENDS BUT MEDIUM ON SPEEDS.

* HIGH THAT RAIN WILL TRANSITION TO AT LEAST A RAIN SNOW MIX
  SOMETIME MONDAY MORNING...MEDIUM ON TIMING.


KMD

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

MONDAY NIGHT...SNOW SHOWERS LIKELY. GUSTY BUT DIMINISHING WEST WINDS.

TUESDAY...MVFR CIGS POSSIBLE WITH A FEW FLURRIES IN THE MORNING.
NORTHWEST WINDS.

WEDNESDAY...CHANCE OF SNOW. MVFR/IFR PSBL. SSE WINDS TURNING WEST.

THURSDAY...SCHC SNOW...OTHERWISE VFR. BREEZY NORTHWEST WINDS.

FRIDAY...SCHC SNOW.

SATURDAY...VFR.

KMD

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
321 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE LATE SUNDAY
  MORNING AND LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE BRIEFLY THIS MORNING
  AND AGAIN BY MID AFTERNOON. STEADIEST RAIN BY EVENING.

* SOUTH WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN SOUTHEAST
  SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR FOR A FEW MORE HOURS WITH 40 KT WINDS AT
  2000 FT AGL.

KMD

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

QUITE A GRADIENT IN CONDITIONS ACROSS THE AREA EARLY THIS
MORNING...FROM LIFR CONDITIONS NEAR KRFD TO VFR FROM KMDW AND
AREAS SOUTH AND EAST. SLIGHTLY DRIER AIR IS MOVING IN FROM THE
SOUTH THAT WILL ALLOW CIGS TO IMPROVE SOME OVER THE COMING HOURS.
LOOKS LIKE ORD WILL LIFT HERE PRETTY SOON TO AT LEAST HIGHER MVFR
AND PROBABLY VFR FOR A TIME. EVEN EXPECT SOME IMPROVEMENT WEST
TOWARDS KRFD BACK TO AT LEAST MVFR FOR A TIME AS WELL.

PREV DISCUSSION FROM 06Z...

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD

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

* HIGH IN MVFR LIFTING TO VFR IN THE COMING HOURS. LOW- MEDIUM
  CONFIDENCE IN FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT
  IFR/LIFR WILL PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY
  MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL INCREASE FOR A SHORT TIME
  THIS MORNING THEN AGAIN ESPECIALLY LATER THIS AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230921
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
321 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE LATE SUNDAY
  MORNING AND LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE BRIEFLY THIS MORNING
  AND AGAIN BY MID AFTERNOON. STEADIEST RAIN BY EVENING.

* SOUTH WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN SOUTHEAST
  SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR FOR A FEW MORE HOURS WITH 40 KT WINDS AT
  2000 FT AGL.

KMD

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

QUITE A GRADIENT IN CONDITIONS ACROSS THE AREA EARLY THIS
MORNING...FROM LIFR CONDITIONS NEAR KRFD TO VFR FROM KMDW AND
AREAS SOUTH AND EAST. SLIGHTLY DRIER AIR IS MOVING IN FROM THE
SOUTH THAT WILL ALLOW CIGS TO IMPROVE SOME OVER THE COMING HOURS.
LOOKS LIKE ORD WILL LIFT HERE PRETTY SOON TO AT LEAST HIGHER MVFR
AND PROBABLY VFR FOR A TIME. EVEN EXPECT SOME IMPROVEMENT WEST
TOWARDS KRFD BACK TO AT LEAST MVFR FOR A TIME AS WELL.

PREV DISCUSSION FROM 06Z...

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD

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

* HIGH IN MVFR LIFTING TO VFR IN THE COMING HOURS. LOW- MEDIUM
  CONFIDENCE IN FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT
  IFR/LIFR WILL PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY
  MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL INCREASE FOR A SHORT TIME
  THIS MORNING THEN AGAIN ESPECIALLY LATER THIS AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
312 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE SUNDAY MORNING AND
  LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

KMD

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

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD

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

* HIGH IN MVFR PREVAILING THROUGH MIDDAY. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT IFR/LIFR WILL
  PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW THROUGH
  TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH THAT
  COVERAGE WILL INCREASE LATE SUNDAY MORNING AND ESPECIALLY LATE
  SUNDAY AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS POTENTIAL.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230912
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
312 AM CST SUN NOV 23 2014

.SHORT TERM...
312 AM CST

THROUGH TONIGHT

WHAT A DIFFERENCE 48 HOURS MAKES! BRISK SOUTHERLY WINDS ARE
TRANSPORTING AN UNSEASONABLY MILD AND MOIST AIR MASS INTO THE REGION
WITH OVERNIGHT TEMPS IN THE UPPER 40S/LOWER 50S. COMPLEX PATTERN
ALOFT WITH STRONG CLOSED MID LEVEL LOW TRACKING EASTWARD JUST NORTH
OF THE CANADIAN BORDER WHILE A POWERFUL PACIFIC JET NOSES INTO THE
SOUTHERN ROCKIES AT THE BASE OF A STRONG SOUTHERN STREAM SHORTWAVE.

IN THE NEAR TERM...MORE SUBTLE SHORTWAVE EVIDENT ON WATER VAPOR
IMAGERY OVER NE OK/SE KS TRACKING NORTHEASTWARD HAS RESULTED IN A
RECENT BLOSSOMING OF RAIN OVER NORTHERN MISSOURI. SHORT RANGE
GUIDANCE AGREES THAT AS THE SHORTWAVE CONTINUES NE THIS MORNING THAT
THIS AREA OF RAIN WILL DEVELOP EASTWARD WHILE MOVE NORTHEAST AND
SPREAD INTO MAINLY WESTERN AND NORTHERN PORTIONS OF OUR CWA. THIS
RAIN SHOULD LIFT NORTH THROUGH THE MORNING AND AS IT LOOKS NOW THERE
WILL BE A SEVERAL HOUR LONG BREAK IN THE RAIN OVER MUCH OF THE AREA
THIS AFTERNOON IN THE WAKE OF THIS SHORTWAVE AND PRIOR TO THE
HEAVIER AND MORE WIDESPREAD RAIN ASSOCIATED WITH THE STRENGTHENING
SOUTHERN STREAM SHORTWAVE SPREADS ACROSS THE CWA LATE THIS AFTERNOON
AND ESPECIALLY THIS EVENING. HIGH PWATS AND STRONG FORCING SHOULD
RESULT IN HEALTHY RAINFALL TOTALS AND PERIODIC MODERATE TO NEARLY
HEAVY RAIN WITHIN THE WARM CONVEYOR BELT THIS EVENING. STILL LOOKS
LIKELY THAT MOST OF THE AREA WILL PICK UP IN THE NEIGHBORHOOD OF AN
INCH OF RAIN THIS AFTERNOON INTO TONIGHT.

STEADY STREAM OF MID-UPPER 40 DEWPOINTS ADVECTING NORTH INTO THE
AREA SHOULD ALLOW TEMPS TO FALL VERY LITTLE EARLY THIS MORNING.
WHILE CLOUD COVER WILL BE EXTENSIVE TODAY...THE ANTICIPATE BREAK IN
THE PRECIP SHOULD BE ENOUGH TO ALLOW TEMPS TO INCH UP INTO THE
MID-UPPER 50S ACROSS THE MAJORITY OF THE CWA...ONE EXCEPTION
POTENTIALLY BEING FAR NORTHWEST WHERE RAIN COULD LINGER LONGER INTO
MIDDAY. TONGUE OF 50 DEGREE DEWPOINTS SHOULD POKE UP INTO THE AREA
TONIGHT AHEAD OF THE STRONG COLD FRONT AND ANTICIPATE TEMPS TONIGHT
TO HOLD IN THE 50S WITH THE RAIN THE MAJORITY OF THE NIGHT WITH LOWS
OCCURRING JUST PAST SUNRISE.

IZZI

&&

.LONG TERM...
312 AM CST

MONDAY ONWARD...

STILL SEEING SOME NON-TRIVIAL DIFFERENCES IN THE MODELS WITH RESPECT
TO THE DETAILS MONDAY...LIKELY DUE TO THEIR TENDENCY TO STRUGGLE
WITH PHASING SYSTEMS. ALL GUIDANCE SWEEPS A STRONG COLD FRONT ACROSS
THE AREA MONDAY MORNING WITH FALLING TEMPERATURES AND STRONG
WESTERLY WINDS LIKELY MONDAY INTO MONDAY EVENING. THE BIGGEST
DIFFERENCE IN THE SOLUTIONS FOR OUR AREA IS AN INCREASING LARGE CAMP
OF MODEL GUIDANCE IS SHOWING A FAIRLY STRONG NORTHERN STREAM
SHORTWAVE LAGGING BEHIND AND ENHANCING ASCENT IN THE DEFORMATION
ZONE ACROSS OUR CWA MONDAY AFTERNOON AND EVENING. BY THIS POINT
THERMAL PROFILES WOULD SUPPORT ALL SNOW. LATEST GFS/ECMWF/PARALLEL
13KM GFS ALL SHOWING AN ACCUMULATING SNOWFALL ACROSS OUR CWA MONDAY
AFTERNOON AND EVENING...ESPECIALLY NORTHERN 1/2 TO 2/3 OF THE AREA.
THE LACK OF RUN-TO-RUN CONSISTENCY AND KNOWN ISSUES GUIDANCE HAS
WITH PHASING SYSTEMS LEADS TO LOWER THAN AVERAGE CONFIDENCE BUT HAVE
BUMPED UP POPS TO LIKELY IN THIS TIME FRAME AND CARRIED A COUPLE
INCHES OF ACCUMULATION IN THE GRIDS FOR THIS TIME FRAME.

IF THE LATEST GFS/ECMWF QPF ENDS UP BEING IN THE BALL PARK OF WHAT
HAPPENS THEN WE COULD BE LOOKING AT A FAIRLY HIGH IMPACT EVENT WITH
SEVERAL INCHES OF ACCUMULATION POSSIBLE. IN ADDITION...VERY STRONG
WINDS WILL FURTHER RESULT IN A FURTHER DETERIORATION IN CONDITIONS.
FORECAST SOUNDINGS DON`T FAVOR HIGH SNOW:LIQUID RATIO SNOWFALL WITH
DEEP ISOTHERMAL LAYER WARMER THAN -10C...RATHER LARGER AGGREGATE
FLAKES WOULD BE FAVORED WITH A WETTER SNOW AND LOWER VSBYS. WILL
BEGIN TO ADVERTISE THIS THREAT IN THE HWO BUT FAR TOO EARLY TO
CONSIDER ANY HEADLINES AT THIS POINT.

YET ANOTHER SURGE OF ARCTIC AIR SPILLS INTO THE REGION TUESDAY IN
THE WAKE OF THIS SYSTEM. FAST ON ITS HEELS OF THIS SYSTEM LOOKS TO
BE A FAIRLY ENERGETIC CLIPPER DIVING INTO THE REGION WEDNESDAY. THE
00Z GFS HAS BACKED OFF ON THE INTENSITY OF THIS WAVE...WHILE THE
ECMWF HAS TRENDED STRONGER AND LOOKS MORE IN LINE WITH THE 84 HOUR
WRF-NAM. IN ADDITION...THE 13KM PARALLEL GFS IS MORE IN THE STRONGER
NAM/ECMWF CAMP SO FELT COMFORTABLE RAISING POPS ABOVE THE SUPERBLEND
INITIALIZATION AS POTENTIAL LOOKS TO BE GROWING FOR A HIGHER
PROBABILITY/LOWER QPF SNOW EVENT IN THE REGION WEDNESDAY. IT SHOULD
COME AS NO SURPRISE THAT MORE ARCTIC LOOKS TO SPILL INTO THE REGION
BEHIND THIS SYSTEM IN TIME FOR THE THANKSGIVING HOLIDAY WEEKEND.

IZZI

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE SUNDAY MORNING AND
  LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

KMD

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

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD

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

* HIGH IN MVFR PREVAILING THROUGH MIDDAY. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT IFR/LIFR WILL
  PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW THROUGH
  TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH THAT
  COVERAGE WILL INCREASE LATE SUNDAY MORNING AND ESPECIALLY LATE
  SUNDAY AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS POTENTIAL.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230853
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
253 AM CST SUN NOV 23 2014

.UPDATE...

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE SUNDAY MORNING AND
  LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

KMD

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

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD

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

* HIGH IN MVFR PREVAILING THROUGH MIDDAY. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT IFR/LIFR WILL
  PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW THROUGH
  TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH THAT
  COVERAGE WILL INCREASE LATE SUNDAY MORNING AND ESPECIALLY LATE
  SUNDAY AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS POTENTIAL.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230853
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
253 AM CST SUN NOV 23 2014

.UPDATE...

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE SUNDAY MORNING AND
  LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

KMD

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

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD

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

* HIGH IN MVFR PREVAILING THROUGH MIDDAY. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT IFR/LIFR WILL
  PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW THROUGH
  TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH THAT
  COVERAGE WILL INCREASE LATE SUNDAY MORNING AND ESPECIALLY LATE
  SUNDAY AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS POTENTIAL.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...
252 AM CST

LOW PRESSURE MOVING EAST FROM THE CANADIAN PRAIRIES EARLY THIS
MORNING WILL CONTINUE TO FILL AS IT TRACKS ALONG THE CANADIAN BORDER
TODAY AND REACHES LAKE SUPERIOR LATE THIS AFTERNOON. THIS LOW WILL
MERGE WITH LOW PRESSURE CURRENTLY EMERGING OUT OF THE SOUTHERN HIGH
PLAINS REGION. THE HIGH PLAINS LOW WILL ABSORB THE NORTHERN LOW OVER
LAKE MICHIGAN TONIGHT THEN CONTINUE TO DEEPEN AS IT TRACKS OVER/EAST
OF LAKE MICHIGAN MONDAY MORNING...THEN DEEPENS MORE MONDAY NIGHT AS
IT CONTINUES EAST OF JAMES BAY.  HAVE NOT MADE CHANGES TO THE
HEADLINES AT THIS MOMENT. CONFIDENCE ON GALES FOR THE SOUTHERN HALF
OF THE LAKE IS HIGH THOUGH STILL SOME ISSUES WITH TIMING. IT LOOKS
LIKE GALES BEGIN TO SPREAD OVER THE SOUTHERN TIP OF THE LAKE NEAR OR
SHORTLY AFTER DAYBREAK MONDAY.  CONFIDENCE FOR GALES ON THE NORTH
HALF OF THE LAKE IS A BIT LESS BUT STILL MEDIUM-HIGH GIVEN
DIFFERENCES IN HOW QUICKLY MODELS MOVE THE LOW OVER THE LAKE MONDAY
INTO MONDAY NIGHT. DEPENDING ON HOW QUICKLY THE LOW KICKS
NORTHEAST...THE GALE WATCH END TIME FOR THE FAR NORTHERN PORTION OF
THE LAKE MAY BE A BIT TOO SHORT. WEAK HIGH PRESSSURE PASSES OVER THE
LAKE TUESDAY. THIS WILL BE FOLLOWED ON WEDNESDAY ON A CLIPPER-TYPE
LOW COMING OUT OF THE DAKOTAS TUESDAY. THIS LOW PUSHES EAST OF THE
LAKE WEDNESDAY NIGHT AS STRONGER HIGH PRESSURE BUILDS IN TO THE
CENTER OF THE COUNTRY THURSDAY AND LINGERS FOR A FEW DAYS. KMD

&&

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

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 230602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1202 AM CST SUN NOV 23 2014

.UPDATE...631 PM CST

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE SUNDAY MORNING AND
  LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

KMD

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

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD


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

* HIGH IN MVFR PREVAILING THROUGH MIDDAY. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT IFR/LIFR WILL
  PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW THROUGH
  TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH THAT
  COVERAGE WILL INCREASE LATE SUNDAY MORNING AND ESPECIALLY LATE
  SUNDAY AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS POTENTIAL.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM SUNDAY TO 7 PM SUNDAY.

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 230602
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1202 AM CST SUN NOV 23 2014

.UPDATE...631 PM CST

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* MVFR CIGS THROUGH THIS MORNING. IFR POSSIBLE SUNDAY MORNING AND
  LIKELY BY LATE AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

KMD

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

CIGS CONTINUE TO DETERIORATE FROM WEST TO EAST EARLY THIS
MORNING...WITH LOWER MVFR CIGS KNOCKING AT THE DOOR CLOSER TO
KRFD...WHILE SOUTHEAST OF KIKK TO KGYY CIGS WILL CONTINUE VARY
WITH VFR DOMINATING AND OCCASIONAL MVFR THROUGH THE OVERNIGHT
HOURS. IFR CONDITIONS MAY SNEAK INTO OUR WESTERN AREAS OVERNIGHT
BUT NOT SEEING MUCH BELOW 1000 FT CIGS YET. LOW LEVEL WIND SHEAR
IS ALSO POSSIBLE FOR THE COMING HOURS.

HAVE NOT MADE MAJOR CHANGES TO THE CURRENT TAF THEME. EXPECT A
WAVE OF RAIN THIS MORNING BETWEEN 12Z AND 18Z FROM SOUTH TO
NORTH...WITH ACTIVITY MORE SCATTERED IN NATURE IN THE MAIN
CHICAGOLAND TERMINALS AND POINTS EAST...WHILE AREAS WEST HOLD A
BETTER CHANCE OF MODERATE RAIN AND IFR CONDITIONS. EXPECT MVFR TO
HOLD ELSEWHERE. THE MAIN FORCING FOR PRECIPITATION BEST COINCIDES
WITH DEEPER MOISTURE IN THE 22Z-6Z TIME FRAME WHERE CIGS AND
VISIBILITIES SHOULD EASILY FALL TO IFR/LIFR. WINDS WILL ALSO SHIFT TO A
SOUTHEASTERLY DIRECTION THROUGH THE AFTERNOON AND EARLY EVENING. AFTER
6Z WINDS WILL SHIFT MORE SOUTHERLY AND RAIN WILL EASE SOMEWHAT.
THAT SAID CIGS WILL GENERALLY REMAIN IN IFR/LIFR WITH A PERIOD OF
LIGHTER RAIN/DRIZZLE WITH AN ADDITIONAL PERIOD OF SHOWERS TOWARD
MONDAY MORNING.

KMD


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

* HIGH IN MVFR PREVAILING THROUGH MIDDAY. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON. HIGH THAT IFR/LIFR WILL
  PREVAIL FROM LATE AFTERNOON THROUGH EARLY MONDAY MORNING.

* MEDIUM-HIGH IN VFR VSBY OUTSIDE OF ANY SHOWERS OVERNIGHT/SUNDAY
  MORNING.

* HIGH THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW THROUGH
  TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH THAT
  COVERAGE WILL INCREASE LATE SUNDAY MORNING AND ESPECIALLY LATE
  SUNDAY AFTERNOON.

* HIGH IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM CONFIDENCE
  SUNDAY AFTERNOON/EVENING.

* MEDIUM IN LLWS POTENTIAL.

KMD

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
     LMZ745...4 AM SUNDAY TO 7 PM SUNDAY.

     GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230239
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
839 PM CST SAT NOV 22 2014

.UPDATE...
631 PM CST

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* VFR CIGS WITH INTERMITTENT MVFR LIKELY BECOMING STEADIER MVFR
  OVERNIGHT. IFR POSSIBLE SUNDAY MORNING AND LIKELY BY LATE
  AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH TONIGHT/SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

MDB

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

SHIFTING GEARS A BIT BASED ON LATEST CIG/VSBY TRENDS. VFR
CONTINUES TO PREVAIL...WITH THE EXCEPTION OF MVFR AT RFD...WITH
INTERMITTENT MVFR CLOUD BANDS SHOWING UP IN UPSTREAM OBS. EXPECT
THAT STEADIER MVFR WILL DEVELOP OVERNIGHT BUT THERE MAY CONTINUE
TO BE VFR BREAKS EVEN THROUGH THE MORNING. THUS HAVE TRENDED TO
IMPROVED CIGS IN THE TAF AMD. SEE LITTLE CHANCE FOR IFR TO DEVELOP
TONIGHT BUT IT REMAINS POSSIBLE THAT IT MAY ARRIVE LATER SUNDAY
MORNING...WITH IT LIKELY AT RFD...AS BUILDING IFR AREA TO THE WEST
WORKS EASTWARD. HAVE ALSO TRENDED VSBY UP WITH VFR AT ALL BUT RFD.
WITH LITTLE CHANGE IN AIRMASS...LITTLE COOLING...AND NO VSBY
RESTRICTION UPSTREAM OUTSIDE OF THAT ASSOCIATED WITH SHOWERS IT
WILL BE TOUGH TO FALL INTO MVFR WITHOUT RAIN CAUSING THE
REDUCTION. THE MAIN AREA OF RAIN IS ON A TRACK TO PASS SOUTH OF
THE TERMINALS BUT STILL EXPECT SOME INCREASED ACTIVITY TO THE
NORTH AS LOW LEVEL WINDS RAMP UP. GYY STILL HAS THE BEST POTENTIAL
FOR A PERIOD OF MORE FREQUENT SHOWERS OVERNIGHT.

FROM 00Z...

CIG/VSBY TRENDS THROUGH SUNDAY MORNING ARE THE INITIAL
CHALLENGE...FOLLOWED BY WIND TRENDS SUNDAY AFTERNOON AND TIMING/COVERAGE
OF RAIN THROUGH SUNDAY EVENING. THE AREA REMAINS BETWEEN HIGH
PRESSURE WELL TO THE EAST AND DEVELOPING LOW PRESSURE TO THE
SOUTHWEST ALLOWING A STEADY SOUTH-SOUTHWEST WIND TO CONTINUE. MVFR
CIGS HAVE ACTUALLY IMPROVED TO VFR SOUTH OF A LINE FROM UGN TO
KC75. UPSTREAM OBS SHOW A MIX OF VFR AND MVFR AND AM EXPECTING MVFR
TO RETURN BUT IT MAY TAKE LONGER THAN THE 00Z TAF REFLECTS. BEYOND
THAT HAVE TRENDED TOWARD BETTER CEILINGS THROUGH TOMORROW MORNING
BY CARRYING BKN VS OVC IFR CIGS FROM LATE TONIGHT ONWARD. AM
CONCERNED THAT IFR MAY EITHER BE BRIEF LATE TONIGHT OR NOT DEVELOP
AT ALL SO WILL NEED TO WATCH THIS CLOSELY. HAVE HIGHER CONFIDENCE
IN IFR DURING THE LATER AFTERNOON HOURS SUNDAY HOWEVER. HAVE THE
SAME CONCERN FOR VSBY AS WELL AND HAVE TRENDED UP THROUGH THE
EVENING. WITH NO REAL CHANGE IN AIRMASS AND LITTLE COOLING
EXPECTED NOR ANY LOSS OF CLOUD COVER...SIGNIFICANT VSBY REDUCTION
WILL BE DIFFICULT. 3-5SM VSBY MAY END UP PREVAILING SO MAY NEED TO
MAKE FURTHER ADJUSTMENTS OVERNIGHT.

IN TERMS OF SHOWERS...AN UPPER WAVE IS LIFTING NORTHEAST FROM
MISSOURI THIS EVENING AND WITH LOW LEVEL WINDS INCREASING INTO
TONIGHT COVERAGE MAY INCREASE TO THE NORTH OF THE CURRENT BAND.
STILL THINKING GYY WILL HAVE THE BEST CHANCE OVERALL BUT MDW MAY
BE SKIRTED IF MORE SOLID NORTHWARD DEVELOPMENT OCCURS. OTHERWISE
THE INCREASING LOW LEVEL WINDS MAY RESULT IN SPOTTY NEW
DEVELOPMENT ACROSS THE REST OF THE AREA SO OPTED FOR A VCSH
MENTION AT ALL BUT RFD...THOUGH THE CHANCE AT RFD IS NOT ZERO. LOW
PRESSURE WILL TAKE SHAPE TO THE SOUTHWEST TOMORROW AND MOVE
NORTHEAST BRINGING A BAND OF WIDESPREAD RAIN WITH IT. EXPECT THIS
TO MOVE INTO RFD DURING THE EARLY AFTERNOON AND POINTS EAST INTO
THE EVENING. AM EXPECTING THAT THERE WILL BE MORE SCATTERED
COVERAGE AHEAD OF IT FROM LATE MORNING ONWARD. CIGS/VSBY WILL FALL
AS THE MORE WIDESPREAD RAIN MOVES IN WITH LIFR POSSIBLE.

HAVE GOOD CONFIDENCE IN THE WIND FORECAST THROUGH THE MORNING
THROUGH GUSTS COULD BE A LITTLE HIGHER DURING THE DAY. THE TRACK
OF THE SURFACE LOW WILL DICTATE HOW WINDS EVOLVE INTO THE EVENING
AND AT THIS POINT FEEL THAT THE LOW WILL MOVE OVER NORTH-CENTRAL
ILLINOIS SUPPORTING A SHIFT TO SOUTHEAST WINDS DURING THE
AFTERNOON...THEN BACK SOUTH DURING THE EVENING. THERE MAY BE AN
OPPORTUNITY FOR MORE OF AN EAST COMPONENT SUNDAY AFTERNOON THAN
CURRENTLY INDICATED.

MDB

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

* HIGH CONFIDENCE IN VFR WITH INTERMITTENT MVFR. MEDIUM CONFIDENCE
  IN STEADIER MVFR DEVELOPING OVERNIGHT. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON.

* MEDIUM-HIGH CONFIDENCE IN VFR VSBY OUTSIDE OF ANY SHOWERS
  OVERNIGHT/SUNDAY MORNING.

* HIGH CONFIDENCE THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW
  THROUGH TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH
  CONFIDENCE THAT COVERAGE WILL INCREASE LATE SUNDAY MORNING AND
  ESPECIALLY LATE SUNDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM
  CONFIDENCE SUNDAY AFTERNOON/EVENING.

* MEDIUM CONFIDENCE IN LLWS POTENTIAL.

MDB

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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

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000
FXUS63 KLOT 230239
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
839 PM CST SAT NOV 22 2014

.UPDATE...
631 PM CST

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* VFR CIGS WITH INTERMITTENT MVFR LIKELY BECOMING STEADIER MVFR
  OVERNIGHT. IFR POSSIBLE SUNDAY MORNING AND LIKELY BY LATE
  AFTERNOON.

* VFR VSBY EXPECTED OUTSIDE OF ANY SHOWERS THROUGH TONIGHT/SUNDAY
  MORNING.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

MDB

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

SHIFTING GEARS A BIT BASED ON LATEST CIG/VSBY TRENDS. VFR
CONTINUES TO PREVAIL...WITH THE EXCEPTION OF MVFR AT RFD...WITH
INTERMITTENT MVFR CLOUD BANDS SHOWING UP IN UPSTREAM OBS. EXPECT
THAT STEADIER MVFR WILL DEVELOP OVERNIGHT BUT THERE MAY CONTINUE
TO BE VFR BREAKS EVEN THROUGH THE MORNING. THUS HAVE TRENDED TO
IMPROVED CIGS IN THE TAF AMD. SEE LITTLE CHANCE FOR IFR TO DEVELOP
TONIGHT BUT IT REMAINS POSSIBLE THAT IT MAY ARRIVE LATER SUNDAY
MORNING...WITH IT LIKELY AT RFD...AS BUILDING IFR AREA TO THE WEST
WORKS EASTWARD. HAVE ALSO TRENDED VSBY UP WITH VFR AT ALL BUT RFD.
WITH LITTLE CHANGE IN AIRMASS...LITTLE COOLING...AND NO VSBY
RESTRICTION UPSTREAM OUTSIDE OF THAT ASSOCIATED WITH SHOWERS IT
WILL BE TOUGH TO FALL INTO MVFR WITHOUT RAIN CAUSING THE
REDUCTION. THE MAIN AREA OF RAIN IS ON A TRACK TO PASS SOUTH OF
THE TERMINALS BUT STILL EXPECT SOME INCREASED ACTIVITY TO THE
NORTH AS LOW LEVEL WINDS RAMP UP. GYY STILL HAS THE BEST POTENTIAL
FOR A PERIOD OF MORE FREQUENT SHOWERS OVERNIGHT.

FROM 00Z...

CIG/VSBY TRENDS THROUGH SUNDAY MORNING ARE THE INITIAL
CHALLENGE...FOLLOWED BY WIND TRENDS SUNDAY AFTERNOON AND TIMING/COVERAGE
OF RAIN THROUGH SUNDAY EVENING. THE AREA REMAINS BETWEEN HIGH
PRESSURE WELL TO THE EAST AND DEVELOPING LOW PRESSURE TO THE
SOUTHWEST ALLOWING A STEADY SOUTH-SOUTHWEST WIND TO CONTINUE. MVFR
CIGS HAVE ACTUALLY IMPROVED TO VFR SOUTH OF A LINE FROM UGN TO
KC75. UPSTREAM OBS SHOW A MIX OF VFR AND MVFR AND AM EXPECTING MVFR
TO RETURN BUT IT MAY TAKE LONGER THAN THE 00Z TAF REFLECTS. BEYOND
THAT HAVE TRENDED TOWARD BETTER CEILINGS THROUGH TOMORROW MORNING
BY CARRYING BKN VS OVC IFR CIGS FROM LATE TONIGHT ONWARD. AM
CONCERNED THAT IFR MAY EITHER BE BRIEF LATE TONIGHT OR NOT DEVELOP
AT ALL SO WILL NEED TO WATCH THIS CLOSELY. HAVE HIGHER CONFIDENCE
IN IFR DURING THE LATER AFTERNOON HOURS SUNDAY HOWEVER. HAVE THE
SAME CONCERN FOR VSBY AS WELL AND HAVE TRENDED UP THROUGH THE
EVENING. WITH NO REAL CHANGE IN AIRMASS AND LITTLE COOLING
EXPECTED NOR ANY LOSS OF CLOUD COVER...SIGNIFICANT VSBY REDUCTION
WILL BE DIFFICULT. 3-5SM VSBY MAY END UP PREVAILING SO MAY NEED TO
MAKE FURTHER ADJUSTMENTS OVERNIGHT.

IN TERMS OF SHOWERS...AN UPPER WAVE IS LIFTING NORTHEAST FROM
MISSOURI THIS EVENING AND WITH LOW LEVEL WINDS INCREASING INTO
TONIGHT COVERAGE MAY INCREASE TO THE NORTH OF THE CURRENT BAND.
STILL THINKING GYY WILL HAVE THE BEST CHANCE OVERALL BUT MDW MAY
BE SKIRTED IF MORE SOLID NORTHWARD DEVELOPMENT OCCURS. OTHERWISE
THE INCREASING LOW LEVEL WINDS MAY RESULT IN SPOTTY NEW
DEVELOPMENT ACROSS THE REST OF THE AREA SO OPTED FOR A VCSH
MENTION AT ALL BUT RFD...THOUGH THE CHANCE AT RFD IS NOT ZERO. LOW
PRESSURE WILL TAKE SHAPE TO THE SOUTHWEST TOMORROW AND MOVE
NORTHEAST BRINGING A BAND OF WIDESPREAD RAIN WITH IT. EXPECT THIS
TO MOVE INTO RFD DURING THE EARLY AFTERNOON AND POINTS EAST INTO
THE EVENING. AM EXPECTING THAT THERE WILL BE MORE SCATTERED
COVERAGE AHEAD OF IT FROM LATE MORNING ONWARD. CIGS/VSBY WILL FALL
AS THE MORE WIDESPREAD RAIN MOVES IN WITH LIFR POSSIBLE.

HAVE GOOD CONFIDENCE IN THE WIND FORECAST THROUGH THE MORNING
THROUGH GUSTS COULD BE A LITTLE HIGHER DURING THE DAY. THE TRACK
OF THE SURFACE LOW WILL DICTATE HOW WINDS EVOLVE INTO THE EVENING
AND AT THIS POINT FEEL THAT THE LOW WILL MOVE OVER NORTH-CENTRAL
ILLINOIS SUPPORTING A SHIFT TO SOUTHEAST WINDS DURING THE
AFTERNOON...THEN BACK SOUTH DURING THE EVENING. THERE MAY BE AN
OPPORTUNITY FOR MORE OF AN EAST COMPONENT SUNDAY AFTERNOON THAN
CURRENTLY INDICATED.

MDB

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

* HIGH CONFIDENCE IN VFR WITH INTERMITTENT MVFR. MEDIUM CONFIDENCE
  IN STEADIER MVFR DEVELOPING OVERNIGHT. LOW-MEDIUM CONFIDENCE IN
  FALLING TO IFR BEFORE SUNDAY AFTERNOON.

* MEDIUM-HIGH CONFIDENCE IN VFR VSBY OUTSIDE OF ANY SHOWERS
  OVERNIGHT/SUNDAY MORNING.

* HIGH CONFIDENCE THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW
  THROUGH TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH
  CONFIDENCE THAT COVERAGE WILL INCREASE LATE SUNDAY MORNING AND
  ESPECIALLY LATE SUNDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM
  CONFIDENCE SUNDAY AFTERNOON/EVENING.

* MEDIUM CONFIDENCE IN LLWS POTENTIAL.

MDB

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 230041
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
641 PM CST SAT NOV 22 2014

.UPDATE...
631 PM CST

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* VFR CIGS FALLING TO MVFR THIS EVENING...POTENTIALLY IFR LATE
  TONIGHT. IFR POSSIBLE SUNDAY MORNING AND LIKELY BY LATE
  AFTERNOON.

* MVFR VSBY EXPECTED TONIGHT WITH IFR POSSIBLE.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

MDB

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

CIG/VSBY TRENDS THROUGH SUNDAY MORNING ARE THE INITIAL
CHALLENGE...FOLLOWED BY WIND TRENDS SUNDAY AFTERNOON AND TIMING/COVERAGE
OF RAIN THROUGH SUNDAY EVENING. THE AREA REMAINS BETWEEN HIGH
PRESSURE WELL TO THE EAST AND DEVELOPING LOW PRESSURE TO THE
SOUTHWEST ALLOWING A STEADY SOUTH-SOUTHWEST WIND TO CONTINUE. MVFR
CIGS HAVE ACTUALLY IMPROVED TO VFR SOUTH OF A LINE FROM UGN TO
KC75. UPSTREAM OBS SHOW A MIX OF VFR AND MVFR AND AM EXPECTING MVFR
TO RETURN BUT IT MAY TAKE LONGER THAN THE 00Z TAF REFLECTS. BEYOND
THAT HAVE TRENDED TOWARD BETTER CEILINGS THROUGH TOMORROW MORNING
BY CARRYING BKN VS OVC IFR CIGS FROM LATE TONIGHT ONWARD. AM
CONCERNED THAT IFR MAY EITHER BE BRIEF LATE TONIGHT OR NOT DEVELOP
AT ALL SO WILL NEED TO WATCH THIS CLOSELY. HAVE HIGHER CONFIDENCE
IN IFR DURING THE LATER AFTERNOON HOURS SUNDAY HOWEVER. HAVE THE
SAME CONCERN FOR VSBY AS WELL AND HAVE TRENDED UP THROUGH THE
EVENING. WITH NO REAL CHANGE IN AIRMASS AND LITTLE COOLING
EXPECTED NOR ANY LOSS OF CLOUD COVER...SIGNIFICANT VSBY REDUCTION
WILL BE DIFFICULT. 3-5SM VSBY MAY END UP PREVAILING SO MAY NEED TO
MAKE FURTHER ADJUSTMENTS OVERNIGHT.

IN TERMS OF SHOWERS...AN UPPER WAVE IS LIFTING NORTHEAST FROM
MISSOURI THIS EVENING AND WITH LOW LEVEL WINDS INCREASING INTO
TONIGHT COVERAGE MAY INCREASE TO THE NORTH OF THE CURRENT BAND.
STILL THINKING GYY WILL HAVE THE BEST CHANCE OVERALL BUT MDW MAY
BE SKIRTED IF MORE SOLID NORTHWARD DEVELOPMENT OCCURS. OTHERWISE
THE INCREASING LOW LEVEL WINDS MAY RESULT IN SPOTTY NEW
DEVELOPMENT ACROSS THE REST OF THE AREA SO OPTED FOR A VCSH
MENTION AT ALL BUT RFD...THOUGH THE CHANCE AT RFD IS NOT ZERO. LOW
PRESSURE WILL TAKE SHAPE TO THE SOUTHWEST TOMORROW AND MOVE
NORTHEAST BRINGING A BAND OF WIDESPREAD RAIN WITH IT. EXPECT THIS
TO MOVE INTO RFD DURING THE EARLY AFTERNOON AND POINTS EAST INTO
THE EVENING. AM EXPECTING THAT THERE WILL BE MORE SCATTERED
COVERAGE AHEAD OF IT FROM LATE MORNING ONWARD. CIGS/VSBY WILL FALL
AS THE MORE WIDESPREAD RAIN MOVES IN WITH LIFR POSSIBLE.

HAVE GOOD CONFIDENCE IN THE WIND FORECAST THROUGH THE MORNING
THROUGH GUSTS COULD BE A LITTLE HIGHER DURING THE DAY. THE TRACK
OF THE SURFACE LOW WILL DICTATE HOW WINDS EVOLVE INTO THE EVENING
AND AT THIS POINT FEEL THAT THE LOW WILL MOVE OVER NORTH-CENTRAL
ILLINOIS SUPPORTING A SHIFT TO SOUTHEAST WINDS DURING THE
AFTERNOON...THEN BACK SOUTH DURING THE EVENING. THERE MAY BE AN
OPPORTUNITY FOR MORE OF AN EAST COMPONENT SUNDAY AFTERNOON THAN
CURRENTLY INDICATED.

MDB

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

* HIGH CONFIDENCE IN VFR CIGS FALLING BACK TO MVFR. MEDIUM
  CONFIDENCE IN TIMING. LOW-MEDIUM CONFIDENCE IN FALLING TO IFR
  BEFORE SUNDAY AFTERNOON. IFR IS POSSIBLE LATE TONIGHT BUT MAY
  IMPROVE EARLY SUNDAY MORNING.

* MEDIUM-HIGH CONFIDENCE IN MVFR VSBY TONIGHT. LOW-MEDIUM
  CONFIDENCE IN TIMING.

* HIGH CONFIDENCE THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW
  THROUGH TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH
  CONFIDENCE THAT COVERAGE WILL INCREASE LATE SUNDAY MORNING AND
  ESPECIALLY LATE SUNDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM
  CONFIDENCE SUNDAY AFTERNOON/EVENING.

* MEDIUM CONFIDENCE IN LLWS POTENTIAL.

MDB

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 230041
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
641 PM CST SAT NOV 22 2014

.UPDATE...
631 PM CST

MADE ADJUSTMENTS TO THE POP FORECAST FOR TONIGHT AS RADAR IS
RATHER QUIET RIGHT NOW. THE WAVE AND ASSOCIATED RAIN SHOWERS OVER
SOUTHWESTERN AND CENTRAL IL LOOKS LIKE THEY WILL BE THE BEST CHANCE
FOR RAIN THROUGH TONIGHT. THEREFORE KEPT HIGHER POPS SOUTH OF
I-80. CEILING HEIGHTS KEEP RISING OVER NORTHERN IL WHICH LEADS TO
ME TO BELIEVE DRIER AIR WILL LIMIT RAINFALL. LEFT CHANCE POPS IN
ACROSS THE CWA LATE THIS EVENING AS I DO NOT HAVE ENOUGH
CONFIDENCE TO GO DRY. DEWPOINT DEPRESSIONS ARE IN THE SINGLE
DIGITS ACROSS THE BOARD SO STILL THINKING AREAS OF FOG WILL
PERSIST OVERNIGHT. NOT EXPECTING DENSE FOG AT THIS POINT IN TIME.
LOOKING TOWARD TOMORROW...TIMING OF PRECIP AND FOG LOOK GOOD SO
DID NOT MAKE ANY CHANGES.

ALSO ADJUSTED TEMPERATURES A BIT HIGHER TONIGHT AND STILL MAY NOT
HAVE GONE HIGH ENOUGH. WITH THE THICK CLOUD COVER AND SOUTHERLY
WINDS...NOT EXPECTING TEMPS TO DROP VERY MUCH OVERNIGHT.

JEE

&&

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* VFR CIGS FALLING TO MVFR THIS EVENING...POTENTIALLY IFR LATE
  TONIGHT. IFR POSSIBLE SUNDAY MORNING AND LIKELY BY LATE
  AFTERNOON.

* MVFR VSBY EXPECTED TONIGHT WITH IFR POSSIBLE.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

MDB

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

CIG/VSBY TRENDS THROUGH SUNDAY MORNING ARE THE INITIAL
CHALLENGE...FOLLOWED BY WIND TRENDS SUNDAY AFTERNOON AND TIMING/COVERAGE
OF RAIN THROUGH SUNDAY EVENING. THE AREA REMAINS BETWEEN HIGH
PRESSURE WELL TO THE EAST AND DEVELOPING LOW PRESSURE TO THE
SOUTHWEST ALLOWING A STEADY SOUTH-SOUTHWEST WIND TO CONTINUE. MVFR
CIGS HAVE ACTUALLY IMPROVED TO VFR SOUTH OF A LINE FROM UGN TO
KC75. UPSTREAM OBS SHOW A MIX OF VFR AND MVFR AND AM EXPECTING MVFR
TO RETURN BUT IT MAY TAKE LONGER THAN THE 00Z TAF REFLECTS. BEYOND
THAT HAVE TRENDED TOWARD BETTER CEILINGS THROUGH TOMORROW MORNING
BY CARRYING BKN VS OVC IFR CIGS FROM LATE TONIGHT ONWARD. AM
CONCERNED THAT IFR MAY EITHER BE BRIEF LATE TONIGHT OR NOT DEVELOP
AT ALL SO WILL NEED TO WATCH THIS CLOSELY. HAVE HIGHER CONFIDENCE
IN IFR DURING THE LATER AFTERNOON HOURS SUNDAY HOWEVER. HAVE THE
SAME CONCERN FOR VSBY AS WELL AND HAVE TRENDED UP THROUGH THE
EVENING. WITH NO REAL CHANGE IN AIRMASS AND LITTLE COOLING
EXPECTED NOR ANY LOSS OF CLOUD COVER...SIGNIFICANT VSBY REDUCTION
WILL BE DIFFICULT. 3-5SM VSBY MAY END UP PREVAILING SO MAY NEED TO
MAKE FURTHER ADJUSTMENTS OVERNIGHT.

IN TERMS OF SHOWERS...AN UPPER WAVE IS LIFTING NORTHEAST FROM
MISSOURI THIS EVENING AND WITH LOW LEVEL WINDS INCREASING INTO
TONIGHT COVERAGE MAY INCREASE TO THE NORTH OF THE CURRENT BAND.
STILL THINKING GYY WILL HAVE THE BEST CHANCE OVERALL BUT MDW MAY
BE SKIRTED IF MORE SOLID NORTHWARD DEVELOPMENT OCCURS. OTHERWISE
THE INCREASING LOW LEVEL WINDS MAY RESULT IN SPOTTY NEW
DEVELOPMENT ACROSS THE REST OF THE AREA SO OPTED FOR A VCSH
MENTION AT ALL BUT RFD...THOUGH THE CHANCE AT RFD IS NOT ZERO. LOW
PRESSURE WILL TAKE SHAPE TO THE SOUTHWEST TOMORROW AND MOVE
NORTHEAST BRINGING A BAND OF WIDESPREAD RAIN WITH IT. EXPECT THIS
TO MOVE INTO RFD DURING THE EARLY AFTERNOON AND POINTS EAST INTO
THE EVENING. AM EXPECTING THAT THERE WILL BE MORE SCATTERED
COVERAGE AHEAD OF IT FROM LATE MORNING ONWARD. CIGS/VSBY WILL FALL
AS THE MORE WIDESPREAD RAIN MOVES IN WITH LIFR POSSIBLE.

HAVE GOOD CONFIDENCE IN THE WIND FORECAST THROUGH THE MORNING
THROUGH GUSTS COULD BE A LITTLE HIGHER DURING THE DAY. THE TRACK
OF THE SURFACE LOW WILL DICTATE HOW WINDS EVOLVE INTO THE EVENING
AND AT THIS POINT FEEL THAT THE LOW WILL MOVE OVER NORTH-CENTRAL
ILLINOIS SUPPORTING A SHIFT TO SOUTHEAST WINDS DURING THE
AFTERNOON...THEN BACK SOUTH DURING THE EVENING. THERE MAY BE AN
OPPORTUNITY FOR MORE OF AN EAST COMPONENT SUNDAY AFTERNOON THAN
CURRENTLY INDICATED.

MDB

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

* HIGH CONFIDENCE IN VFR CIGS FALLING BACK TO MVFR. MEDIUM
  CONFIDENCE IN TIMING. LOW-MEDIUM CONFIDENCE IN FALLING TO IFR
  BEFORE SUNDAY AFTERNOON. IFR IS POSSIBLE LATE TONIGHT BUT MAY
  IMPROVE EARLY SUNDAY MORNING.

* MEDIUM-HIGH CONFIDENCE IN MVFR VSBY TONIGHT. LOW-MEDIUM
  CONFIDENCE IN TIMING.

* HIGH CONFIDENCE THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW
  THROUGH TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH
  CONFIDENCE THAT COVERAGE WILL INCREASE LATE SUNDAY MORNING AND
  ESPECIALLY LATE SUNDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM
  CONFIDENCE SUNDAY AFTERNOON/EVENING.

* MEDIUM CONFIDENCE IN LLWS POTENTIAL.

MDB

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 230011
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
611 PM CST SAT NOV 22 2014

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* VFR CIGS FALLING TO MVFR THIS EVENING...POTENTIALLY IFR LATE
  TONIGHT. IFR POSSIBLE SUNDAY MORNING AND LIKELY BY LATE
  AFTERNOON.

* MVFR VSBY EXPECTED TONIGHT WITH IFR POSSIBLE.

* ISOLATED-SCATTERED SHOWER CHANCES INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. BETTER
  CHANCES LATE SUNDAY MORNING THROUGH THE AFTERNOON. STEADIEST
  RAIN BY EVENING.

* SOUTH-SOUTHWEST WINDS BECOMING GUSTY SUNDAY MORNING. SHOULD TURN
  SOUTHEAST SUNDAY AFTERNOON THEN BACK SOUTH SUNDAY EVENING.

* LOW LEVEL WIND SHEAR POSSIBLE TONIGHT WITH 45 KT WINDS AT 2000
  FT AGL.

MDB

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

CIG/VSBY TRENDS THROUGH SUNDAY MORNING ARE THE INITIAL
CHALLENGE...FOLLOWED BY WIND TRENDS SUNDAY AFTERNOON AND TIMING/COVERAGE
OF RAIN THROUGH SUNDAY EVENING. THE AREA REMAINS BETWEEN HIGH
PRESSURE WELL TO THE EAST AND DEVELOPING LOW PRESSURE TO THE
SOUTHWEST ALLOWING A STEADY SOUTH-SOUTHWEST WIND TO CONTINUE. MVFR
CIGS HAVE ACTUALLY IMPROVED TO VFR SOUTH OF A LINE FROM UGN TO
KC75. UPSTREAM OBS SHOW A MIX OF VFR AND MVFR AND AM EXPECTING MVFR
TO RETURN BUT IT MAY TAKE LONGER THAN THE 00Z TAF REFLECTS. BEYOND
THAT HAVE TRENDED TOWARD BETTER CEILINGS THROUGH TOMORROW MORNING
BY CARRYING BKN VS OVC IFR CIGS FROM LATE TONIGHT ONWARD. AM
CONCERNED THAT IFR MAY EITHER BE BRIEF LATE TONIGHT OR NOT DEVELOP
AT ALL SO WILL NEED TO WATCH THIS CLOSELY. HAVE HIGHER CONFIDENCE
IN IFR DURING THE LATER AFTERNOON HOURS SUNDAY HOWEVER. HAVE THE
SAME CONCERN FOR VSBY AS WELL AND HAVE TRENDED UP THROUGH THE
EVENING. WITH NO REAL CHANGE IN AIRMASS AND LITTLE COOLING
EXPECTED NOR ANY LOSS OF CLOUD COVER...SIGNIFICANT VSBY REDUCTION
WILL BE DIFFICULT. 3-5SM VSBY MAY END UP PREVAILING SO MAY NEED TO
MAKE FURTHER ADJUSTMENTS OVERNIGHT.

IN TERMS OF SHOWERS...AN UPPER WAVE IS LIFTING NORTHEAST FROM
MISSOURI THIS EVENING AND WITH LOW LEVEL WINDS INCREASING INTO
TONIGHT COVERAGE MAY INCREASE TO THE NORTH OF THE CURRENT BAND.
STILL THINKING GYY WILL HAVE THE BEST CHANCE OVERALL BUT MDW MAY
BE SKIRTED IF MORE SOLID NORTHWARD DEVELOPMENT OCCURS. OTHERWISE
THE INCREASING LOW LEVEL WINDS MAY RESULT IN SPOTTY NEW
DEVELOPMENT ACROSS THE REST OF THE AREA SO OPTED FOR A VCSH
MENTION AT ALL BUT RFD...THOUGH THE CHANCE AT RFD IS NOT ZERO. LOW
PRESSURE WILL TAKE SHAPE TO THE SOUTHWEST TOMORROW AND MOVE
NORTHEAST BRINGING A BAND OF WIDESPREAD RAIN WITH IT. EXPECT THIS
TO MOVE INTO RFD DURING THE EARLY AFTERNOON AND POINTS EAST INTO
THE EVENING. AM EXPECTING THAT THERE WILL BE MORE SCATTERED
COVERAGE AHEAD OF IT FROM LATE MORNING ONWARD. CIGS/VSBY WILL FALL
AS THE MORE WIDESPREAD RAIN MOVES IN WITH LIFR POSSIBLE.

HAVE GOOD CONFIDENCE IN THE WIND FORECAST THROUGH THE MORNING
THROUGH GUSTS COULD BE A LITTLE HIGHER DURING THE DAY. THE TRACK
OF THE SURFACE LOW WILL DICTATE HOW WINDS EVOLVE INTO THE EVENING
AND AT THIS POINT FEEL THAT THE LOW WILL MOVE OVER NORTH-CENTRAL
ILLINOIS SUPPORTING A SHIFT TO SOUTHEAST WINDS DURING THE
AFTERNOON...THEN BACK SOUTH DURING THE EVENING. THERE MAY BE AN
OPPORTUNITY FOR MORE OF AN EAST COMPONENT SUNDAY AFTERNOON THAN
CURRENTLY INDICATED.

MDB


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

* HIGH CONFIDENCE IN VFR CIGS FALLING BACK TO MVFR. MEDIUM
  CONFIDENCE IN TIMING. LOW-MEDIUM CONFIDENCE IN FALLING TO IFR
  BEFORE SUNDAY AFTERNOON. IFR IS POSSIBLE LATE TONIGHT BUT MAY
  IMPROVE EARLY SUNDAY MORNING.

* MEDIUM-HIGH CONFIDENCE IN MVFR VSBY TONIGHT. LOW-MEDIUM
  CONFIDENCE IN TIMING.

* HIGH CONFIDENCE THAT COVERAGE OF SHOWERS WILL GENERALLY BE LOW
  THROUGH TONIGHT...WITH MOST ACTIVITY JUST TO THE SOUTH. HIGH
  CONFIDENCE THAT COVERAGE WILL INCREASE LATE SUNDAY MORNING AND
  ESPECIALLY LATE SUNDAY AFTERNOON.

* HIGH CONFIDENCE IN WIND TRENDS THROUGH SUNDAY MORNING. MEDIUM
  CONFIDENCE SUNDAY AFTERNOON/EVENING.

* MEDIUM CONFIDENCE IN LLWS POTENTIAL.

MDB

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

MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTH TO SOUTHWEST WINDS.
THURSDAY...SNOW SHOWERS AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. WEST TO SOUTHWEST WINDS.

MDB

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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 222216
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
416 PM CST SAT NOV 22 2014

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* MVFR CIGS AROUND 020 CONTINUING THROUGH THE EVENING...TRENDING
  TO IFR OVERNIGHT OR SUNDAY MORNING.

* VSBY EXPECTED TO FALL TO 2-4SM SOME TIME LATER THIS EVENING OR
  EARLY TONIGHT.

* SHOWER CHANCES INCREASE LATE TONIGHT WITH MORE WIDESPREAD
  COVERAGE LATER SUNDAY MORNING/MIDDAY.

* LOW LEVEL WIND SHEAR POSSIBLE OVERNIGHT WITH WINDS INCREASING TO
  45 KT AT 2000 FT AGL.

MDB

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

CIGS GENERALLY HOVERING AROUND 020 LATE THIS AFTERNOON WITH SOME
SCATTERING OF THE LOWEST DECK AT TIMES. EXPECT THAT MVFR CIGS WILL
PREVAIL WELL INTO THE EVENING WITH SOME UNCERTAINTY IN HOW QUICKLY
THINGS MAY FALL TO IFR. VSBY DOES LOOK TO GRADUALLY FALL THIS
EVENING...WITH RFD LIKELY HOLDING FAIRLY STEADY BEFORE FALLING
LATE THIS EVENING. A FEW SPOTTY SHOWERS HAD DEVELOPED BUT ARE
MOVING OUT OF THE AREA AND IT APPEARS THAT MAINLY DRY CONDITIONS
WILL CONTINUE UNTIL LATER THIS EVENING WHEN AN UPPER WAVE MOVES
NORTHEAST FROM MISSOURI AND BRINGS SHOWERS WITH IT. GYY LOOKS TO
HAVE THE BEST CHANCE OF OCCURRENCE BUT ACTIVITY MAY SPREAD
TOWARDS MDW TOWARD 8-10Z OR SO. OTHERWISE SCATTERED SHOWERS WILL
BECOME MORE LIKELY ACROSS THE REST OF THE AREA TOWARD DAYBREAK WITH
MORE WIDESPREAD COVERAGE WORKING NORTHWARD LATER SUNDAY MORNING.

MDB

FROM 18Z...

VERY MOIST AIR MASS CONTINUES TO FEED NORTHEAST ACROSS NORTHERN
IL/NORTHWEST IN AIRFIELDS THIS AFTERNOON. LITTLE IMPROVEMENT TO
THE CIGS IS EXPECTED...AS A RESULT HAVE HELD CIGS DOWN ARND LOW
END MVFR THIS AFTN AND WILL LIKELY TREND BACK TOWARDS IFR CONDS
OVERNIGHT. GENERALLY EXPECT CIGS ARND 500-900FT AGL THRU THE
OVERNIGHT HOURS. WIND DIR WILL NOT CHANGE MUCH THIS
AFTN/EVE/OVERNIGHT...MAINLY FROM THE SOUTH WITH SPEEDS ALSO NOT
CHANGING MUCH ARND 10-12KT. GIVEN HOW MOIST THE ATMOSPHERE
IS...PERIODIC ROUNDS OF DRIZZLE CAN BE EXPECTED THRU THIS
AFTN/EARLY EVE WILL A LULL LATE THIS EVE. WIND SHEAR IS ALSO
POISED TO DEVELOP THIS EVENING...WITH WINDS ARND 2KFT AGL FROM THE
SOUTHWEST INCREASING TO 40-45KT.

GUIDANCE HAS CONTINUED TO SUGGEST DEVELOPING RAIN SHOWERS AFT
MIDNIGHT/EARLY SUN...SO HAVE HELD ONTO THE MENTION OF LGT RAIN
EARLY SUN. THEN IT APPEARS THE BETER COVERAGE FOR PERHAPS MORE
STEADY RAIN WILL OCCUR LATE SUN MORNING...AND COULD PERSIST THRU
SUN AFTN.

BEACHLER

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

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE EVENING. LOW-MEDIUM
  CONFIDENCE IN TIMING OF LOWERING TO IFR.

* HIGH CONFIDENCE IN VSBY FALLING TO MVFR AND MEDIUM CONFIDENCE IN
  FALLING TO HIGHER END IFR. MEDIUM CONFIDENCE IN TIMING OF
  REDUCTIONS.

* HIGH CONFIDENCE THAT SHOWER CHANCES WILL INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. MEDIUM
  CONFIDENCE THAT MORE WIDESPREAD COVERAGE HOLDS OFF UNTIL LATER
  SUNDAY MORNING.

* MEDIUM CONFIDENCE IN LLWS OCCURRING.

MDB

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

SUNDAY NIGHT...RAIN AND IFR PROBABLE. SOUTHERLY WINDS.
MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTHWEST WINDS.
THURSDAY...FLURRIES AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. SOUTHWEST WINDS.

MTF

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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000
FXUS63 KLOT 222216
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
416 PM CST SAT NOV 22 2014

.SHORT TERM...
258 PM CST

FOR THE REMAINDER OF THIS AFTERNOON AND THROUGH TONIGHT...AN
INFLUX OF WARM...MOIST AIR WILL CONTINUE TO STREAM INTO THE UPPER
MIDWEST. LATEST SFC ANALYSIS SHOWS DEWPOINTS IN THE 50S OVER
MISSOURI WHILE DEWPOINTS ACROSS NRN IL. NWRN IN HAVE CLIMBED INTO
THE MIDDLE TO UPPER 40S. TEMPERATURES HAVE ALSO BEEN ON THE RISE
THROUGH THE DAY WITH TEMPERATURES AT OR IN EXCESS OF 50F AS FAR
NORTH AS MIDWAY AIRPORT AND AURORA AS OF 230PM CST. TEMPERATURES
ARE EXPECTED TO CONTINUE TO RISE INTO THE EARLY EVENING UNDER THE
PERSISTENT WARM...MOIST ADVECTION UNDER A STRONG SWLY LOW LEVEL
JET WITH 850MB WINDS UP TO 45KT...TEMPERATURES WILL LIKELY HOVER
AROUND THE 50 DEGREE MARK THROUGH THE NIGHT. ADDITIONAL LIGHT RAIN
OR DRIZZLE WILL PERSIST THROUGH THE EVENING AND OVERNIGHT...WITH
AREAS OF FOG POSSIBLE.

KREIN

&&

.LONG TERM...
258 PM CST

MORE SIGNIFICANT RAINFALL IS SETTING UP FOR SUNDAY AND INTO
SUNDAY NIGHT AS A STRONG SRN STREAM SHORTWAVE LIFTING OUT OF THE
SOUTH HIGH PLAINS PHASES WITH ANOTHER SHORTWAVE LIFTING FROM THE
SOUTHWEST GULF COAST REGION. THESE SYSTEM WILL RESULT IN A
DEEPENING SFC LOW OF 984MB NEAR ST LOUIS BY SUNDAY EVENING. THE
MODELS CONTINUE TO ADVERTISE PWAT VALUES AROUND 1.2 INCHES...WHICH
IS AT THE 99TH PERCENTILE FOR PWATS FOR THE REGION. THIS PHASING
OF THE TWO SRN STREAM SYSTEMS COMBINED WITH THE UNUSUALLY HIGH
PWAT AIRMASS WILL COMBINE TO FOCUS STEADY RAINFALL ACROSS THE
REGION THROUGH THE DAY ON SUNDAY AND INTO SUNDAY EVENING...WITH A
CORRIDOR OF THE HEAVIEST RAIN OVER THE NWRN PORTIONS OF THE
CWA...GENERALLY NORTH OF A LINE FROM PERU TO MCHENRY...WHERE
UPWARDS OF A HALF INCH PER 3 HOUR PERIOD IS POSSIBLE. LATER SUNDAY
NIGHT...THE PHASED SRN STREAM SYSTEM WILL BEGIN TO PHASE WITH A
NRN STREAM SHORTWAVE...WITH LOW PRESSURE RAPIDLY DEEPENING AS IT
LIFTS THROUGH THE UPPER GREAT LAKES. WHILE THE GUIDANCE IS
RELATIVELY CONSISTENT ON THE TRACK AND TIMING OF THE DEEPENING
LOW...THE GFS IS A MUCH STRONGER OUTLIER IN THE GUIDANCE
ENVELOPE...DEEPENING THE CENTRAL PRESSURE TO ARND 966MB BY MIDDAY
MONDAY...WHILE MUCH OF THE OTHER GUIDANCE ONLY DEEPENS THE LOW TO
ARND 980MB. WHILE THE GFS SOLUTION MAY BE TOO DEEP...LIKELY
DRAWING COLDER AIR INTO THE SYSTEM FASTER THAN THE OTHER
MODELS...OR TAPPING MORE NRN STREAM ENERGY...THERE WILL STILL
LIKELY BE A DEEP LOW DEVELOPING OVER THE UPPER GREAT LAKES SUNDAY
NIGHT INTO MONDAY...WHOSE CIRCULATION PATTERN WILL COVER A LARGE
EXPANSE FROM THE EAST-CENTRAL PLAINS TO NERN QUEBEC. A STRONG WLY-
NWLY GRADIENT WILL SET UP ON THE SWRN PERIPHERY OF THE
SYSTEM...LEADING TO STRONG...GUSTY WINDS ACROSS THE CWA FROM EARLY
MONDAY MORNING THROUGH LATE MONDAY EVENING. THE STRONGEST WINDS
SHOULD OCCUR FROM LATE MORNING THROUGH LATE EVENING...WITH
SUSTAINED WINDS OF 25-30 MPH AND PEAK GUSTS OF 35-40 MPH.
HOWEVER...IF THE SYSTEM EVOLVES A LITTLE DEEPER THAT THE CONSENSUS
GUIDANCE AND DEEPENS CLOSER TO THE OUTLIER GFS SOLUTION...WINDS
ACROSS THE AREA COULD REACH WIND ADVISORY LEVELS OF SUSTAINED
WINDS OF 30 MPH OR HIGHER OR GUSTS OF 45 MPH OR GREATER.

ALSO...AS THE SFC LOW BEGINS TO LIFT OUT TO THE NORTHEAST MONDAY
AFTERNOON...MUCH COOLER AIR WILL BEGIN TO FILTER ACROSS THE REGION.
AS THE PATTERN TRANSITIONS FROM ONE OF STRONG WARM ADVECTION SUNDAY
NIGHT TO STRONG COLD ADVECTION BY MONDAY MORNING...FOLLOWING THE
PASSAGE OF A STRONG ASSOCIATED COLD FRONT...LINGERING PCPN WILL
BEGIN TO TRANSITION FROM RAIN TO SNOW.  SINCE THE COLD AIR SHOULD
EXTEND THROUGH THE ENTIRE ATMOSPHERE...THERE SHOULD BE A MORE
STRAIGHTFORWARD TRANSITION FROM RAIN TO SNOW WITH LITTLE CHANCE FOR
ANY FREEZING RAIN OR SLEET.  THERE COLD BE SOME ISSUES WITH WATER
FLASH FREEZING ON ELEVATED SURFACES AS SUB-FREEZING AIR QUICKLY
FILTERS ACROSS THE REGION BY LATE MONDAY AFTERNOON.

THE STRONG COLD ADVECTION WILL PERSIST THROUGH THE NIGHT WITH
TEMPERATURES DROPPING TO THE LOWER TO MIDDLE 20S BY DAYBREAK TUESDAY
MORNING.  THE PERSISTENT COLD ADVECTION WILL ALLOW FOR LITTLE
DIURNAL WARMING WITH HIGHS ON TUESDAY EXPECTED TO BE IN THE UPPER
20S TO ARND 30F OVER THE FAR SERN PORTIONS OF THE CWA. THERE BE SOME
MODERATION TO TEMPERATURES ON WEDNESDAY AS WEAK SFC RIDGING CROSSES
THE AREA ALLOWING TEMPERATURES TO RISE INTO THE MIDDLE 30S.
WEDNESDAY SHOULD BE THE WARMEST OF THE EXTENDED PERIOD.  A SERIES OF
STRONG NORTHERN STREAM SHORTWAVES IS EXPECTED TO CARVE OUT A BROAD
LONGWAVE TROUGH OVER ERN CONUS FROM THE MISSISSIPPI VALLEY TO THE
EAST COAST.  THE UPPER LEVEL PATTERN SHOULD DECREASE IN AMPLITUDE
THROUGH THE EXTENDED PERIOD...BUT THE LOCAL AREA IS EXPECTED TO
REMAIN UNDER GENERAL NWLY FLOW ALOFT...KEEPING A PERSISTENT FETCH OF
COLD AIR ACROSS THE AREA. BY LATE NEXT WEEK...HIGH TEMPERATURES WILL
STRUGGLE INTO THE LOWER TO MIDDLE 20S...WHILE OVERNIGHT LOWS DROP
INTO THE LOWER TO MIDDLE TEENS...WITH THE POSSIBILITY OF THE NWRN
PORTIONS OF THE CWA...INCLUDING THE ROCKFORD AREA DROPPING INTO THE
SINGLE DIGITS FRIDAY AND SATURDAY MORNING.  THE SERIES OF SHORTWAVES
RIPPLING THROUGH THE NORTHWEST FLOW SHOULD BRING PERIODIC CHANCES
FOR SOME LIGHT SNOW...BUT CONFIDENCE IS LOW ON THE EXACT TIMING.
CONFIDENCE IS A LITTLE HIGHER THAT ANY SNOW THAT DOES OCCUR SHOULD
BE LIGHT AS THERE WILL BE LITTLE ENVIRONMENTAL MOISTURE OR SFC
FORCING.  ANY SNOW GENERATION WILL HAVE TO RELY ON MID-LEVEL FORCING
AND MEAGER MOISTURE CONTENT.

KREIN

&&

.AVIATION...

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

* MVFR CIGS AROUND 020 CONTINUING THROUGH THE EVENING...TRENDING
  TO IFR OVERNIGHT OR SUNDAY MORNING.

* VSBY EXPECTED TO FALL TO 2-4SM SOME TIME LATER THIS EVENING OR
  EARLY TONIGHT.

* SHOWER CHANCES INCREASE LATE TONIGHT WITH MORE WIDESPREAD
  COVERAGE LATER SUNDAY MORNING/MIDDAY.

* LOW LEVEL WIND SHEAR POSSIBLE OVERNIGHT WITH WINDS INCREASING TO
  45 KT AT 2000 FT AGL.

MDB

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

CIGS GENERALLY HOVERING AROUND 020 LATE THIS AFTERNOON WITH SOME
SCATTERING OF THE LOWEST DECK AT TIMES. EXPECT THAT MVFR CIGS WILL
PREVAIL WELL INTO THE EVENING WITH SOME UNCERTAINTY IN HOW QUICKLY
THINGS MAY FALL TO IFR. VSBY DOES LOOK TO GRADUALLY FALL THIS
EVENING...WITH RFD LIKELY HOLDING FAIRLY STEADY BEFORE FALLING
LATE THIS EVENING. A FEW SPOTTY SHOWERS HAD DEVELOPED BUT ARE
MOVING OUT OF THE AREA AND IT APPEARS THAT MAINLY DRY CONDITIONS
WILL CONTINUE UNTIL LATER THIS EVENING WHEN AN UPPER WAVE MOVES
NORTHEAST FROM MISSOURI AND BRINGS SHOWERS WITH IT. GYY LOOKS TO
HAVE THE BEST CHANCE OF OCCURRENCE BUT ACTIVITY MAY SPREAD
TOWARDS MDW TOWARD 8-10Z OR SO. OTHERWISE SCATTERED SHOWERS WILL
BECOME MORE LIKELY ACROSS THE REST OF THE AREA TOWARD DAYBREAK WITH
MORE WIDESPREAD COVERAGE WORKING NORTHWARD LATER SUNDAY MORNING.

MDB

FROM 18Z...

VERY MOIST AIR MASS CONTINUES TO FEED NORTHEAST ACROSS NORTHERN
IL/NORTHWEST IN AIRFIELDS THIS AFTERNOON. LITTLE IMPROVEMENT TO
THE CIGS IS EXPECTED...AS A RESULT HAVE HELD CIGS DOWN ARND LOW
END MVFR THIS AFTN AND WILL LIKELY TREND BACK TOWARDS IFR CONDS
OVERNIGHT. GENERALLY EXPECT CIGS ARND 500-900FT AGL THRU THE
OVERNIGHT HOURS. WIND DIR WILL NOT CHANGE MUCH THIS
AFTN/EVE/OVERNIGHT...MAINLY FROM THE SOUTH WITH SPEEDS ALSO NOT
CHANGING MUCH ARND 10-12KT. GIVEN HOW MOIST THE ATMOSPHERE
IS...PERIODIC ROUNDS OF DRIZZLE CAN BE EXPECTED THRU THIS
AFTN/EARLY EVE WILL A LULL LATE THIS EVE. WIND SHEAR IS ALSO
POISED TO DEVELOP THIS EVENING...WITH WINDS ARND 2KFT AGL FROM THE
SOUTHWEST INCREASING TO 40-45KT.

GUIDANCE HAS CONTINUED TO SUGGEST DEVELOPING RAIN SHOWERS AFT
MIDNIGHT/EARLY SUN...SO HAVE HELD ONTO THE MENTION OF LGT RAIN
EARLY SUN. THEN IT APPEARS THE BETER COVERAGE FOR PERHAPS MORE
STEADY RAIN WILL OCCUR LATE SUN MORNING...AND COULD PERSIST THRU
SUN AFTN.

BEACHLER

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

* HIGH CONFIDENCE IN MVFR CIGS THROUGH THE EVENING. LOW-MEDIUM
  CONFIDENCE IN TIMING OF LOWERING TO IFR.

* HIGH CONFIDENCE IN VSBY FALLING TO MVFR AND MEDIUM CONFIDENCE IN
  FALLING TO HIGHER END IFR. MEDIUM CONFIDENCE IN TIMING OF
  REDUCTIONS.

* HIGH CONFIDENCE THAT SHOWER CHANCES WILL INCREASE
  OVERNIGHT...ESPECIALLY JUST SOUTH OF THE TERMINALS. MEDIUM
  CONFIDENCE THAT MORE WIDESPREAD COVERAGE HOLDS OFF UNTIL LATER
  SUNDAY MORNING.

* MEDIUM CONFIDENCE IN LLWS OCCURRING.

MDB

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

SUNDAY NIGHT...RAIN AND IFR PROBABLE. SOUTHERLY WINDS.
MONDAY...CHANCE OF RAIN AND SNOW. STRONG WEST TO SOUTHWEST WINDS.
TUESDAY...MVFR CIGS POSSIBLE. WESTERLY WINDS.
WEDNESDAY...CHANCE OF SNOW AND MVFR. SOUTHWEST WINDS.
THURSDAY...FLURRIES AND MVFR POSSIBLE. NORTHWEST WINDS.
FRIDAY...VFR PROBABLE. SOUTHWEST WINDS.

MTF

&&

.MARINE...

231 PM...STRONG LOW PRESSURE WILL MOVE ALONG THE U.S. CANADIAN
BORDER TONIGHT AND BEGIN TO WEAKEN AS IT REACHES WESTERN LAKE
SUPERIOR SUNDAY AFTERNOON. ANOTHER LOW WILL DEVELOP OVER THE
SOUTHERN PLAINS TONIGHT AND MOVE NORTH TO SOUTHERN LAKE MICHIGAN
AS IT DEEPENS AND ABSORBS THE LOW OVER WESTERN LAKE SUPERIOR. THIS
LOW WILL THEN DEEPEN FURTHER AS IT REACHES EASTERN LAKE SUPERIOR
MONDAY MORNING. THERE STILL REMAINS SOME DIFFERENCES AMONG THE
MODELS REGARDING HOW STRONG THIS LOW WILL BECOME. THE DEEPEST OF
THE MODELS HAS A PRESSURE OF 28.5 INCHES MIDDAY MONDAY. CONFIDENCE
IS INCREASING FOR MID/HIGH END GALES SO WILL BE GOING WITH A GALE
WATCH FOR MONDAY AND MONDAY NIGHT. STORM FORCE GUSTS OR PREVAILING
WINDS ALSO REMAIN POSSIBLE. WINDS STEADILY DIMINISH TUESDAY AS
HIGH PRESSURE MOVES ACROSS THE SOUTHERN LAKES AND OHIO VALLEY.
ANOTHER LOW IS EXPECTED TO MOVE ACROSS THE LAKES REGION WEDNESDAY
INTO THURSDAY...BRINGING NORTHWEST WINDS TO 30KT ON THURSDAY. CMS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...6 AM MONDAY TO 3 AM TUESDAY.

     GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...NOON MONDAY TO 3 AM TUESDAY.

&&

$$

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