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000
FXUS63 KLOT 312342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 PM CDT FRI OCT 31 2014

.UPDATE...
556 PM CDT

MINOR UPDATE TO NEAR TERM GRIDS IN PARTICULAR INCREASING POPS
OVER NORTHEAST ILLINOIS AND HEIGHTENING FROZEN PRECIP TYPE...AS
WELL AS EXTENDING THE HIGH WIND WARNING THROUGH THIS EVENING.

LATEST RADAR IMAGERY SHOWING UNORGANIZED BANDS OF LAKE EFFECT
PRECIP CONTINUING TO SPILL INTO PORTIONS OF NORTHEAST ILLINOIS AND
NORTHWEST INDIANA AT THIS HOUR. CURRENT OBSERVATIONAL DATA AS WELL
AS MANY SPOTTER/PUBLIC/SOCIAL MEDIA REPORTS DEPICTING A VARIETY OF
PRECIP TYPES CURRENTLY ONGOING RANGING FROM SNOW...SLEET...AND
RAIN. WHILE OVERALL COLUMN IS SUFFICIENTLY COLD ENOUGH FOR FROZEN
PRECIP...LATEST AMDAR AND SHORT TERM FORECAST SOUNDINGS STILL
SHOWING A HIGHLY VARIABLE THERMAL PROFILE WITHIN THE BOUNDARY
LAYER. WARMER LAKE AIR SPILLING INTO AREAS IMMEDIATELY NEAR THE
LAKE STILL HELPING FOR A RAIN SNOW MIX...WHILE AREAS INLAND
OBSERVING MORE OF A SNOW AND SLEET MIX. THESE VARYING PRECIP TYPES
ACROSS THOSE LOCATIONS WILL LIKELY CONTINUE OVER THE NEXT SEVERAL
HOURS...BEFORE BOUNDARY LAYER SUFFICIENTLY COOLS FOR ALL SNOW OVER
ALL LOCATIONS. THIS WILL OCCUR WHILE LOW LEVEL FLOW AND STRONGEST
OBSERVED CONVERGENCE OVER NORTHWEST INDIANA VEERS...WITH THE FOCUS
THEN SHIFTING MORE INTO ILLINOIS. ALTHOUGH DURING THIS
TIME...BETTER SYNOPTIC SUPPORT WILL EXIT...INVERSIONS WILL
LOWER...SATURATION FOR SNOW GROWTH DIMINISHES...AND CONVERGENCE
ALSO WEAKENS.

WINDS STILL RATHER STRONG AT THIS HOUR AND ALTHOUGH THEY WILL
DIMINISH IN THE NEAR TERM...STRONGEST WINDS SHOULD STILL REMAIN
NEAR HIGH WIND WARNING CRITERIA...ESPECIALLY FOR AREAS NEAR THE
LAKE. DID EXTEND THE CURRENT HIGH WIND WARNING TO 10 PM...BUT WILL
POSSIBLY OBSERVE A FURTHER DIMINISHING TREND PRIOR TO THIS HOUR.

RODRIGUEZ

&&

.SHORT TERM...
307 PM CDT

THROUGH TONIGHT...

NO CHANGES PLANNED WITH HEADLINES.

SEVERAL BANDS OF LAKE EFFECT SNOW HAVE DEVELOPED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON...WITH SOME OF THESE SNOW SHOWERS
IMPACTING PORTIONS OF THE NORTHEASTERN ILLINOIS SHORES.
HOWEVER...THE MOST SUBSTANTIAL AREA OF LAKE EFFECT RAIN AND SNOW HAS
BEEN OCCURRING ALONG THE SOUTHERN TIP OF LAKE MICHIGAN AND ACROSS THE
ADVISORY AREA OF NORTHWESTERN INDIANA. BASED ON NUMEROUS PHONE
CALLS ACROSS THIS AREA IT APPEARS AREAS NEAR THE LAKE ARE SLIGHTLY
WARMER...RESULTING IN A RAIN SNOW MIX. HOWEVER...AREAS ROUGHLY 20 TO
30 MILES INLAND (BASICALLY ALONG AND SOUTH OF A CROWN POINT TO
VALPARAISO INDIANA LINE) THE PRECIPITATION IS MAINLY IN THE FORM OF
SNOW. SEVERAL REPORTS OF ACCUMULATING SNOW HAVE BEEN RECEIVED SOUTH
OF THIS LINE...WITH LOW VISIBILITIES UNDER A MILE.

BASED ON CURRENT RADAR TRENDS AND SHORT RANGE HIRES GUIDANCE...IT
APPEARS THIS ACTIVITY WILL CONTINUE TO BE FOCUSED MAINLY ACROSS
NORTHWESTERN INDIANA FOR THE NEXT FEW HOURS...THROUGH LATE
AFTERNOON/EARLY THIS EVENING. HOWEVER...SOME OF THE LESS ORGANIZED LAKE
EFFECT SNOW SHOWERS WILL LIKELY IMPACT PORTIONS OF COOK AND LAKE
COUNTIES IN ILLINOIS AS WELL DURING THIS TIME. FINALLY...AS THE
SURFACE LOW SHIFTS SOUTHEAST OVER THE OHIO VALLEY INTO THIS EVENING
THE BOUNDARY LAYER FLOW WILL VEER AND WEAKEN A BIT. THIS SHOULD
ALLOW THE BETTER FOCUS FOR LAKE EFFECT SHOWERS TO SHIFT FARTHER WEST
ACROSS PORTIONS OF EASTERN ILLINOIS...INCLUDING THE CHICAGO METRO
AREA NEAR THE LAKE. WHILE THERE COULD BE A SHORT PERIOD OF SOME
MODERATE...OR EVEN BRIEFLY HEAVY SNOW SHOWERS INTO NORTHEASTERN
ILLINOIS INTO THIS EVENING...I HAVE CHOSEN NOT TO EXTEND THE WINTER
ADVISORIES FARTHER WEST INTO ILLINOIS. THIS IS MAINLY DUE TO THE
FACT THAT IT APPEARS THE THREAT FOR BETTER MORE ORGANIZED LAKE
EFFECT SNOW WILL BE OF SHORT DURATION...LIMITING OVERALL
ACCUMULATIONS. HEIGHT RISES AND WARMING TEMPERATURES IN THE MID
LEVELS SHOULD ALLOW INVERSION HEIGHTS TO DROP BELOW THE DENDRITIC
GROWTH ZONE BY LATER THIS EVENING/OVERNIGHT. THE MODELS HAVE BEEN
INSISTENT ON THIS FOR THE PAST FEW DAYS AND SEE NO REASON WHY THIS
WOULD NOT OCCUR AS THE UPPER RIDGE TO OUR WEST BEGINS TO BUILD
EASTWARD. THEREFORE...ANY LEFT OVER LAKE EFFECT SNOW SHOWERS WILL
LIKELY NOT BE EFFICIENT SNOWFALL PRODUCERS AND LIKELY BE LOOSELY
ORGANIZED...AND HENCE THE THREAT FOR ACCUMULATING SNOWFALL SHOULD
COME TO AN END BY LATER THIS EVENING.

THE WINDS WITH THIS SYSTEM HAVE BEEN IMPRESSIVE. KGYY HAS BEEN
EXPERIENCING GUSTS TO 58 KT FOR SEVERAL HOURS...WITH SIMILAR
MAGNITUDES NOTED ALONG THE LAKE SHORE. IT APPEARS THESE STRONG WINDS
WILL SLOWLY EASE TONIGHT AS THE SURFACE HIGH OVERSPREADS THE AREA ON
SATURDAY. THEREFORE...NO CHANGES ARE PLANNED WITH THE CURRENT WIND
ADVISORIES OR WARNINGS.

LAKE SHORE FLOODING CONTINUES TO BE AN ISSUE...ESPECIALLY IN
CHICAGO...WHERE WAVES HAVE BEEN GETTING WATER ONTO LAKE SHORE DRIVE.
WE CONSIDERED TO UPGRADE TO A LAKE SHORE FLOOD WARNING...BUT DECIDED
TO JUST BEEF UP THE WORDING IN THE CURRENT ADVISORY AS A WARNING
WOULD NOT DUE MUCH GOOD AT THIS STAGE OF THE GAME.

KJB

&&

.LONG TERM...
307 PM CDT

TOMORROW THROUGH THURSDAY...

SATURDAY AND SUNDAY...
THE UPPER LEVEL TROUGH PUSHES EAST ALLOWING A LARGE UPPER LEVEL
RIDGE TO MOVE OVERHEAD THROUGH THE WEEKEND. THE CORRESPONDING
SURFACE HIGH MOVES OVER THE REGION TOMORROW EVENING.

GUIDANCE CONTINUES TO FEATURE A NARROW CONVERGENCE BAND ALONG THE
SOUTHWEST END OF LAKE MICHIGAN EARLY SATURDAY MORNING.  KEPT A
SLIGHT CHANCE OF PRECIP IN FOR FAR NORTHEAST IL WITH THE BAND
DISSIPATING BY LATE MORNING/EARLY AFTERNOON AS FORCING AND MOISTURE
WEAKEN. NOT EXPECTING ANY ADDITIONAL SIGNIFICANT ACCUMULATION AND
THE PRECIP TYPE WILL BE A SNOW/RAIN MIX AS TEMPERATURES WILL BE
ABOVE FREEZING OVER THE LAKE.  HAVE MEDIUM CONFIDENCE IN THE BAND
PERSISTING UNTIL MORNING...MEDIUM HIGH CONFIDENCE IN THE BAND MAINLY
IMPACTING THE IL SIDE OF THE LAKE...AND HIGH CONFIDENCE IN LITTLE TO
NO ADDITIONAL ACCUMULATION.

WINDS DECREASE SATURDAY AS THE HIGH MOVES OVERHEAD.  WARMER AIR
BEGINS TO MOVE IN AS WELL WITH HIGHS IN THE LOW 40S TOMORROW. WINDS
TURN SOUTH BEHIND THE HIGH SUNDAY AND USHER IN EVEN WARMER AIR WITH
HIGHS IN THE UPPER 40S TO AROUND 50. SATURDAY AFTERNOON THROUGH
SUNDAY NIGHT WILL BE DRY.

MONDAY THROUGH THURSDAY...
THE RIDGE AXIS MOVES OVERHEAD MONDAY AS THE SURFACE LOW SLIDES OVER
THE SE U.S. THE WARM-UP CONTINUES WITH HIGHS IN THE UPPER 50S TO
AROUND 60 MONDAY...AND MID 50S EXPECTED THROUGH MID WEEK. OVERNIGHT
LOWS VARY FROM THE MID 40S MONDAY NIGHT TO THE MID TO LOWER 30S
THURSDAY NIGHT.

A SURFACE LOW MOVES INTO ONTARIO TUESDAY...AND IT DRAGS A COLD FRONT
ACROSS THE REGION TUESDAY. EXPECTING WIDESPREAD SHOWERS TUESDAY
MORNING WITH RAIN ENDING FROM WEST TO EAST AS THE FRONT SLIDES EAST
TUESDAY EVENING/NIGHT.  GUIDANCE DIFFERS ON HOW MUCH PRECIP WILL
FALL...BUT ITS LOOKING LIKE A GOOD WETTING RAIN IS EXPECTED.

A WEAKER LOW PASSES JUST TO OUR NORTH MID WEEK AND HAVE MEDIUM-LOW
CONFIDENCE IN PRECIP MAKING IT INTO NORTHERN IL WEDNESDAY. THINKING
PRECIP WILL REMAIN CLOSELY TIED TO THE LOW WHICH RIGHT NOW WILL BE
OVER SOUTHERN WI. IF THE LOW/S TRACK WERE TO DIP A BIT MORE
SOUTH...THERE WOULD BE A BETTER CHANCE FOR PRECIP ACROSS FAR
NORTHERN IL.

WINDS TURN NORTHWEST BEHIND THE LOW AND ANOTHER LAKE EFFECT PRECIP
SITUATION IS POSSIBLE FOR NW INDIANA WEDNESDAY NIGHT. ONLY HAVE RAIN
FOR NOW AS TEMPS WILL BE ABOVE FREEZING.  WINDS REMAIN OFF OF THE
LAKE THROUGH THURSDAY NIGHT AS ANOTHER HIGH PRESSURE SYSTEM
APPROACHES FROM THE WEST.

JEE

&&

.AVIATION...

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

* NORTH WINDS GUSTING AROUND 30 KT AT 00Z...SLOWLY DIMINISHING
  THIS EVENING.

* LAKE EFFECT SNOW SHOWERS AFFECTING MDW...AND EXPECTED TO DRIFT
  WEST ACROSS ORD LATER THIS EVENING. MVFR CIGS/BRIEF IFR VIS IN
  -SHSN ESPECIALLY AT MDW. SNOW SHOWERS CONTINUE OVERNIGHT BUT
  WEAKEN AFTER MIDNIGHT.

* MVFR CIGS LINGER SATURDAY...THOUGH RISE WITH TIME AND SCATTER
  LATE.

RATZER

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

VERY GUSTY NORTH WINDS CONTINUE TO SLOWLY DIMINISH EARLY THIS
EVENING AS REGION OF TIGHT SURFACE PRESSURE GRADIENT AND STRONG
PRESSURE RISES AHEAD OF HIGH PRESSURE MOVE SOUTHEAST OF THE
TERMINALS. GUST SHOULD DECREASE BELOW 30 KT 00-02Z FOR CHICAGO
TERMINALS WITH THE EXCEPTION OF GYY...WHERE WIND RIGHT OFF LAKE
MICHIGAN WILL PRODUCE SLOWLY DIMINISHING GUSTS OF 40+ KTS. WINDS
CONTINUE TO SHIFT SLOWLY TO THE NORTH-NORTHEAST SATURDAY MORNING
WITH SPEEDS AND GUSTS CONTINUING TO STEADILY DIMINISH DURING THE
DAY.

LAKE EFFECT RAIN/SNOW SHOWERS OCCURRING IN MULTI-CELLULAR NORTH-
SOUTH BAND ACROSS THE LAKE WERE AFFECTING GYY AND MDW AT TAF
ISSUANCE...THOUGH WITH GRADUAL NORTH-NORTHEASTWARD SHIFT OF
BOUNDARY LAYER FLOW SNOW SHOWERS WILL LIKELY SPREAD WEST INTO ORD
BY MID EVENING. WITHIN AREA OF SNOW SHOWERS...MVFR CIGS AND
OCCASIONAL IFR VISIBILITIES CAN BE EXPECTED...WITH A GRADUAL
DECREASE IN INTENSITY AFTER MIDNIGHT AS HIGH PRESSURE BUILDS
TOWARD THE REGION AND INVERSION LEVELS LOWER. NORTH-NORTHEAST
WINDS WILL LIKELY MAINTAIN MID-HIGH RANGE MVFR CIGS INTO
SATURDAY...THOUGH WITH RISING BASES AND EVENTUAL SCATTERING LATER
IN THE DAY.

RATZER


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

* HIGH CONFIDENCE IN WIND TRENDS.

* MEDIUM CONFIDENCE IN -SHSN TRENDS...AND CIG/VIS IMPACTS.

* MEDIUM CONFIDENCE IN MVFR CIG DURATION SATURDAY.

RATZER

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

SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.

MONDAY...DRY/VFR DURING THE DAY. SHRA LIKELY MONDAY NIGHT. GUSTY
SOUTHWEST WINDS 15-20 KT.

TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.

WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

THURSDAY...DRY/VFR. WEST-NORTHWEST WINDS.

RATZER

&&

.MARINE...
212 PM CDT

STORM FORCE WINDS WILL SLOWLY EASE TO GALES TONIGHT. NO CHANGES
PLANNED TO CURRENT HEADLINES.

FOR THE NEARSHORE ZONES...WILL NEED A PROLONGED SMALL CRAFT ADVISORY
THROUGH AT LEAST SATURDAY AS VERY LARGE WAVES SUBSIDE.  MAY FLIRT
WITH SMALL CRAFT ADVISORY CRITERIA WINDS AND WAVES SUNDAY AND
MONDAY. HAVE MEDIUM CONFIDENCE AS CONDITIONS MAY BE MARGINAL.

NORTH TO NORTHEAST WINDS TO 30 KT SLOWLY DIMINISH SATURDAY AND WINDS
TURN SOUTHWEST BEHIND A HIGH PRESSURE SYSTEM SUNDAY MORNING.  SOUTH
TO SOUTHWEST WINDS INCREASE TO 30 KT SUNDAY AFTERNOON AS THE
GRADIENT TIGHTENS BETWEEN THE DEPARTING HIGH AND AN APPROACHING
LOW.  SOUTH TO SOUTHWEST WINDS FINALLY DIMINISH TO UNDER 30 KT
MONDAY NIGHT...AND THEN WINDS TURN WEST 10-20 KT BEHIND THE LOWS
COLD FRONT TUESDAY. WEST WINDS INCREASE TO 20-25 KT AND BECOME
NORTHWEST WEDNESDAY NIGHT...AND MAY SEE 30 KT WINDS OVER THE
NORTHERN HALF OF THE LAKE THURSDAY.  WINDS DIMINISH THURSDAY NIGHT
AS HIGH PRESSURE MOVES OVER THE AREA.

KJB/JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 10 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 4 AM
     SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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000
FXUS63 KLOT 312302 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
602 PM CDT FRI OCT 31 2014

.UPDATE...
556 PM CDT

MINOR UPDATE TO NEAR TERM GRIDS IN PARTICULAR INCREASING POPS
OVER NORTHEAST ILLINOIS AND HEIGHTENING FROZEN PRECIP TYPE...AS
WELL AS EXTENDING THE HIGH WIND WARNING THROUGH THIS EVENING.

LATEST RADAR IMAGERY SHOWING UNORGANIZED BANDS OF LAKE EFFECT
PRECIP CONTINUING TO SPILL INTO PORTIONS OF NORTHEAST ILLINOIS AND
NORTHWEST INDIANA AT THIS HOUR. CURRENT OBSERVATIONAL DATA AS WELL
AS MANY SPOTTER/PUBLIC/SOCIAL MEDIA REPORTS DEPICTING A VARIETY OF
PRECIP TYPES CURRENTLY ONGOING RANGING FROM SNOW...SLEET...AND
RAIN. WHILE OVERALL COLUMN IS SUFFICIENTLY COLD ENOUGH FOR FROZEN
PRECIP...LATEST AMDAR AND SHORT TERM FORECAST SOUNDINGS STILL
SHOWING A HIGHLY VARIABLE THERMAL PROFILE WITHIN THE BOUNDARY
LAYER. WARMER LAKE AIR SPILLING INTO AREAS IMMEDIATELY NEAR THE
LAKE STILL HELPING FOR A RAIN SNOW MIX...WHILE AREAS INLAND
OBSERVING MORE OF A SNOW AND SLEET MIX. THESE VARYING PRECIP TYPES
ACROSS THOSE LOCATIONS WILL LIKELY CONTINUE OVER THE NEXT SEVERAL
HOURS...BEFORE BOUNDARY LAYER SUFFICIENTLY COOLS FOR ALL SNOW OVER
ALL LOCATIONS. THIS WILL OCCUR WHILE LOW LEVEL FLOW AND STRONGEST
OBSERVED CONVERGENCE OVER NORTHWEST INDIANA VEERS...WITH THE FOCUS
THEN SHIFTING MORE INTO ILLINOIS. ALTHOUGH DURING THIS
TIME...BETTER SYNOPTIC SUPPORT WILL EXIT...INVERSIONS WILL
LOWER...SATURATION FOR SNOW GROWTH DIMINISHES...AND CONVERGENCE
ALSO WEAKENS.

WINDS STILL RATHER STRONG AT THIS HOUR AND ALTHOUGH THEY WILL
DIMINISH IN THE NEAR TERM...STRONGEST WINDS SHOULD STILL REMAIN
NEAR HIGH WIND WARNING CRITERIA...ESPECIALLY FOR AREAS NEAR THE
LAKE. DID EXTEND THE CURRENT HIGH WIND WARNING TO 10 PM...BUT WILL
POSSIBLY OBSERVE A FURTHER DIMINISHING TREND PRIOR TO THIS HOUR.

RODRIGUEZ

&&

.SHORT TERM...
307 PM CDT

THROUGH TONIGHT...

NO CHANGES PLANNED WITH HEADLINES.

SEVERAL BANDS OF LAKE EFFECT SNOW HAVE DEVELOPED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON...WITH SOME OF THESE SNOW SHOWERS
IMPACTING PORTIONS OF THE NORTHEASTERN ILLINOIS SHORES.
HOWEVER...THE MOST SUBSTANTIAL AREA OF LAKE EFFECT RAIN AND SNOW HAS
BEEN OCCURRING ALONG THE SOUTHERN TIP OF LAKE MICHIGAN AND ACROSS THE
ADVISORY AREA OF NORTHWESTERN INDIANA. BASED ON NUMEROUS PHONE
CALLS ACROSS THIS AREA IT APPEARS AREAS NEAR THE LAKE ARE SLIGHTLY
WARMER...RESULTING IN A RAIN SNOW MIX. HOWEVER...AREAS ROUGHLY 20 TO
30 MILES INLAND (BASICALLY ALONG AND SOUTH OF A CROWN POINT TO
VALPARAISO INDIANA LINE) THE PRECIPITATION IS MAINLY IN THE FORM OF
SNOW. SEVERAL REPORTS OF ACCUMULATING SNOW HAVE BEEN RECEIVED SOUTH
OF THIS LINE...WITH LOW VISIBILITIES UNDER A MILE.

BASED ON CURRENT RADAR TRENDS AND SHORT RANGE HIRES GUIDANCE...IT
APPEARS THIS ACTIVITY WILL CONTINUE TO BE FOCUSED MAINLY ACROSS
NORTHWESTERN INDIANA FOR THE NEXT FEW HOURS...THROUGH LATE
AFTERNOON/EARLY THIS EVENING. HOWEVER...SOME OF THE LESS ORGANIZED LAKE
EFFECT SNOW SHOWERS WILL LIKELY IMPACT PORTIONS OF COOK AND LAKE
COUNTIES IN ILLINOIS AS WELL DURING THIS TIME. FINALLY...AS THE
SURFACE LOW SHIFTS SOUTHEAST OVER THE OHIO VALLEY INTO THIS EVENING
THE BOUNDARY LAYER FLOW WILL VEER AND WEAKEN A BIT. THIS SHOULD
ALLOW THE BETTER FOCUS FOR LAKE EFFECT SHOWERS TO SHIFT FARTHER WEST
ACROSS PORTIONS OF EASTERN ILLINOIS...INCLUDING THE CHICAGO METRO
AREA NEAR THE LAKE. WHILE THERE COULD BE A SHORT PERIOD OF SOME
MODERATE...OR EVEN BRIEFLY HEAVY SNOW SHOWERS INTO NORTHEASTERN
ILLINOIS INTO THIS EVENING...I HAVE CHOSEN NOT TO EXTEND THE WINTER
ADVISORIES FARTHER WEST INTO ILLINOIS. THIS IS MAINLY DUE TO THE
FACT THAT IT APPEARS THE THREAT FOR BETTER MORE ORGANIZED LAKE
EFFECT SNOW WILL BE OF SHORT DURATION...LIMITING OVERALL
ACCUMULATIONS. HEIGHT RISES AND WARMING TEMPERATURES IN THE MID
LEVELS SHOULD ALLOW INVERSION HEIGHTS TO DROP BELOW THE DENDRITIC
GROWTH ZONE BY LATER THIS EVENING/OVERNIGHT. THE MODELS HAVE BEEN
INSISTENT ON THIS FOR THE PAST FEW DAYS AND SEE NO REASON WHY THIS
WOULD NOT OCCUR AS THE UPPER RIDGE TO OUR WEST BEGINS TO BUILD
EASTWARD. THEREFORE...ANY LEFT OVER LAKE EFFECT SNOW SHOWERS WILL
LIKELY NOT BE EFFICIENT SNOWFALL PRODUCERS AND LIKELY BE LOOSELY
ORGANIZED...AND HENCE THE THREAT FOR ACCUMULATING SNOWFALL SHOULD
COME TO AN END BY LATER THIS EVENING.

THE WINDS WITH THIS SYSTEM HAVE BEEN IMPRESSIVE. KGYY HAS BEEN
EXPERIENCING GUSTS TO 58 KT FOR SEVERAL HOURS...WITH SIMILAR
MAGNITUDES NOTED ALONG THE LAKE SHORE. IT APPEARS THESE STRONG WINDS
WILL SLOWLY EASE TONIGHT AS THE SURFACE HIGH OVERSPREADS THE AREA ON
SATURDAY. THEREFORE...NO CHANGES ARE PLANNED WITH THE CURRENT WIND
ADVISORIES OR WARNINGS.

LAKE SHORE FLOODING CONTINUES TO BE AN ISSUE...ESPECIALLY IN
CHICAGO...WHERE WAVES HAVE BEEN GETTING WATER ONTO LAKE SHORE DRIVE.
WE CONSIDERED TO UPGRADE TO A LAKE SHORE FLOOD WARNING...BUT DECIDED
TO JUST BEEF UP THE WORDING IN THE CURRENT ADVISORY AS A WARNING
WOULD NOT DUE MUCH GOOD AT THIS STAGE OF THE GAME.

KJB

&&

.LONG TERM...
307 PM CDT

TOMORROW THROUGH THURSDAY...

SATURDAY AND SUNDAY...
THE UPPER LEVEL TROUGH PUSHES EAST ALLOWING A LARGE UPPER LEVEL
RIDGE TO MOVE OVERHEAD THROUGH THE WEEKEND. THE CORRESPONDING
SURFACE HIGH MOVES OVER THE REGION TOMORROW EVENING.

GUIDANCE CONTINUES TO FEATURE A NARROW CONVERGENCE BAND ALONG THE
SOUTHWEST END OF LAKE MICHIGAN EARLY SATURDAY MORNING.  KEPT A
SLIGHT CHANCE OF PRECIP IN FOR FAR NORTHEAST IL WITH THE BAND
DISSIPATING BY LATE MORNING/EARLY AFTERNOON AS FORCING AND MOISTURE
WEAKEN. NOT EXPECTING ANY ADDITIONAL SIGNIFICANT ACCUMULATION AND
THE PRECIP TYPE WILL BE A SNOW/RAIN MIX AS TEMPERATURES WILL BE
ABOVE FREEZING OVER THE LAKE.  HAVE MEDIUM CONFIDENCE IN THE BAND
PERSISTING UNTIL MORNING...MEDIUM HIGH CONFIDENCE IN THE BAND MAINLY
IMPACTING THE IL SIDE OF THE LAKE...AND HIGH CONFIDENCE IN LITTLE TO
NO ADDITIONAL ACCUMULATION.

WINDS DECREASE SATURDAY AS THE HIGH MOVES OVERHEAD.  WARMER AIR
BEGINS TO MOVE IN AS WELL WITH HIGHS IN THE LOW 40S TOMORROW. WINDS
TURN SOUTH BEHIND THE HIGH SUNDAY AND USHER IN EVEN WARMER AIR WITH
HIGHS IN THE UPPER 40S TO AROUND 50. SATURDAY AFTERNOON THROUGH
SUNDAY NIGHT WILL BE DRY.

MONDAY THROUGH THURSDAY...
THE RIDGE AXIS MOVES OVERHEAD MONDAY AS THE SURFACE LOW SLIDES OVER
THE SE U.S. THE WARM-UP CONTINUES WITH HIGHS IN THE UPPER 50S TO
AROUND 60 MONDAY...AND MID 50S EXPECTED THROUGH MID WEEK. OVERNIGHT
LOWS VARY FROM THE MID 40S MONDAY NIGHT TO THE MID TO LOWER 30S
THURSDAY NIGHT.

A SURFACE LOW MOVES INTO ONTARIO TUESDAY...AND IT DRAGS A COLD FRONT
ACROSS THE REGION TUESDAY. EXPECTING WIDESPREAD SHOWERS TUESDAY
MORNING WITH RAIN ENDING FROM WEST TO EAST AS THE FRONT SLIDES EAST
TUESDAY EVENING/NIGHT.  GUIDANCE DIFFERS ON HOW MUCH PRECIP WILL
FALL...BUT ITS LOOKING LIKE A GOOD WETTING RAIN IS EXPECTED.

A WEAKER LOW PASSES JUST TO OUR NORTH MID WEEK AND HAVE MEDIUM-LOW
CONFIDENCE IN PRECIP MAKING IT INTO NORTHERN IL WEDNESDAY. THINKING
PRECIP WILL REMAIN CLOSELY TIED TO THE LOW WHICH RIGHT NOW WILL BE
OVER SOUTHERN WI. IF THE LOW/S TRACK WERE TO DIP A BIT MORE
SOUTH...THERE WOULD BE A BETTER CHANCE FOR PRECIP ACROSS FAR
NORTHERN IL.

WINDS TURN NORTHWEST BEHIND THE LOW AND ANOTHER LAKE EFFECT PRECIP
SITUATION IS POSSIBLE FOR NW INDIANA WEDNESDAY NIGHT. ONLY HAVE RAIN
FOR NOW AS TEMPS WILL BE ABOVE FREEZING.  WINDS REMAIN OFF OF THE
LAKE THROUGH THURSDAY NIGHT AS ANOTHER HIGH PRESSURE SYSTEM
APPROACHES FROM THE WEST.

JEE

&&

.AVIATION...

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

* VERY GUSTY NORTH WINDS WITH GUSTS IN EXCESS OF 30 KT INTO EARLY
  EVENING...01-02Z.

* LAKE EFFECT RAIN/SNOW SHOWERS AT MDW WITH OCCASIONAL IFR VIS AT
  MDW THIS AFTERNOON...DRIFTING WEST INTO ORD THIS EVENING.

* INTENSIFYING LAKE EFFECT SNOW SHOWERS PROBABLE OVER MDW LATER
  THIS EVE. SNOW SHOWERS PERSISTING POSSIBLY AS LONG AS EARLY
  SATURDAY MORNING. SNOW SHOWERS POSSIBLE AT ORD.

* CIGS TEMPORARY TO 1500-3000 FT AT MDW LATE THIS AFTERNOON. CIGS
  GRADUALLY LOWERING TO 1500-2500 FT AT BOTH AIRPORTS LATER
  TONIGHT.

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

VERY GUSTY NORTH-NORTHWEST WINDS WILL CONTINUE THROUGH THIS
AFTERNOON AS COLD AIR CONTINUES TO REPLENISH ITSELF. GUSTS OF 33
TO 40 KT...WITH EVEN SPORADICALLY HIGHER ARE HIGHLY LIKELY TO BE
COMMON THROUGH THE AFTERNOON. DURING THE AFTERNOON...DUE TO THE
ORIENTATION OF THE PRESSURE GRADIENT...THE WIND DIRECTION IS
EXPECTED TO SHIFT TO 360 DEGREES AT CHICAGOLAND TAF SITES. LAKE
EFFECT SNOW...MAYBE AT TIMES RAIN...WILL CONTINUE TO IMPACT GARY
THROUGHOUT THIS AFTERNOON AND TONIGHT. WITH SOME BANDING
POTENTIAL THIS EVE VISIBILITY COULD DROP QUITE LOW DURING THAT
PERIOD. THE SNOW BAND...OR AREA OF SHOWERS...WILL BEGIN TO INCH
BACK WESTWARD THIS EVE INTO OVERNIGHT. THE INTENSITY OF SNOW COULD
STILL BE FAIRLY IMPRESSIVE AT MDW LATER THIS EVE...ALTHOUGH A
DECENT AMOUNT OF UNCERTAINTY EXISTS THERE. AT LEAST LAKE-INDUCED
CLOUDS ARE LIKELY OVER NORTHEAST ILLINOIS SATURDAY MORNING
ALTHOUGH THERE COULD CONTINUE SOME SNOW SHOWERS TOO. AT THE SAME
TIME WINDS ARE FAVORED TO BE BETWEEN 360-020 DEGREES...SO IMPACTS
TO ORD OPERATIONS COULD CONTINUE THROUGH SATURDAY MORNING.

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

* HIGH IN WIND SPEEDS AND DIRECTION THROUGH 00Z. MEDIUM THEREAFTER.

* MEDIUM IN HOW FAR VISIBILITY WILL DROP IN SNOW SHOWERS LATE THIS
  AFTERNOON AND EARLY THIS EVE.

* MEDIUM IN SNOW SHOWERS IMPACTING MDW LATER TONIGHT AND LOW FOR
  ORD. LOW IN HOW FAR VISIBILITY WILL DROP AT EITHER AIRPORT.

* MEDIUM IN CIGS THROUGH TAF.

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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MTF

&&

.MARINE...
212 PM CDT

STORM FORCE WINDS WILL SLOWLY EASE TO GALES TONIGHT. NO CHANGES
PLANNED TO CURRENT HEADLINES.

FOR THE NEARSHORE ZONES...WILL NEED A PROLONGED SMALL CRAFT ADVISORY
THROUGH AT LEAST SATURDAY AS VERY LARGE WAVES SUBSIDE.  MAY FLIRT
WITH SMALL CRAFT ADVISORY CRITERIA WINDS AND WAVES SUNDAY AND
MONDAY. HAVE MEDIUM CONFIDENCE AS CONDITIONS MAY BE MARGINAL.

NORTH TO NORTHEAST WINDS TO 30 KT SLOWLY DIMINISH SATURDAY AND WINDS
TURN SOUTHWEST BEHIND A HIGH PRESSURE SYSTEM SUNDAY MORNING.  SOUTH
TO SOUTHWEST WINDS INCREASE TO 30 KT SUNDAY AFTERNOON AS THE
GRADIENT TIGHTENS BETWEEN THE DEPARTING HIGH AND AN APPROACHING
LOW.  SOUTH TO SOUTHWEST WINDS FINALLY DIMINISH TO UNDER 30 KT
MONDAY NIGHT...AND THEN WINDS TURN WEST 10-20 KT BEHIND THE LOWS
COLD FRONT TUESDAY. WEST WINDS INCREASE TO 20-25 KT AND BECOME
NORTHWEST WEDNESDAY NIGHT...AND MAY SEE 30 KT WINDS OVER THE
NORTHERN HALF OF THE LAKE THURSDAY.  WINDS DIMINISH THURSDAY NIGHT
AS HIGH PRESSURE MOVES OVER THE AREA.

KJB/JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 10 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 4 AM
     SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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 312302 AAA
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
602 PM CDT FRI OCT 31 2014

.UPDATE...
556 PM CDT

MINOR UPDATE TO NEAR TERM GRIDS IN PARTICULAR INCREASING POPS
OVER NORTHEAST ILLINOIS AND HEIGHTENING FROZEN PRECIP TYPE...AS
WELL AS EXTENDING THE HIGH WIND WARNING THROUGH THIS EVENING.

LATEST RADAR IMAGERY SHOWING UNORGANIZED BANDS OF LAKE EFFECT
PRECIP CONTINUING TO SPILL INTO PORTIONS OF NORTHEAST ILLINOIS AND
NORTHWEST INDIANA AT THIS HOUR. CURRENT OBSERVATIONAL DATA AS WELL
AS MANY SPOTTER/PUBLIC/SOCIAL MEDIA REPORTS DEPICTING A VARIETY OF
PRECIP TYPES CURRENTLY ONGOING RANGING FROM SNOW...SLEET...AND
RAIN. WHILE OVERALL COLUMN IS SUFFICIENTLY COLD ENOUGH FOR FROZEN
PRECIP...LATEST AMDAR AND SHORT TERM FORECAST SOUNDINGS STILL
SHOWING A HIGHLY VARIABLE THERMAL PROFILE WITHIN THE BOUNDARY
LAYER. WARMER LAKE AIR SPILLING INTO AREAS IMMEDIATELY NEAR THE
LAKE STILL HELPING FOR A RAIN SNOW MIX...WHILE AREAS INLAND
OBSERVING MORE OF A SNOW AND SLEET MIX. THESE VARYING PRECIP TYPES
ACROSS THOSE LOCATIONS WILL LIKELY CONTINUE OVER THE NEXT SEVERAL
HOURS...BEFORE BOUNDARY LAYER SUFFICIENTLY COOLS FOR ALL SNOW OVER
ALL LOCATIONS. THIS WILL OCCUR WHILE LOW LEVEL FLOW AND STRONGEST
OBSERVED CONVERGENCE OVER NORTHWEST INDIANA VEERS...WITH THE FOCUS
THEN SHIFTING MORE INTO ILLINOIS. ALTHOUGH DURING THIS
TIME...BETTER SYNOPTIC SUPPORT WILL EXIT...INVERSIONS WILL
LOWER...SATURATION FOR SNOW GROWTH DIMINISHES...AND CONVERGENCE
ALSO WEAKENS.

WINDS STILL RATHER STRONG AT THIS HOUR AND ALTHOUGH THEY WILL
DIMINISH IN THE NEAR TERM...STRONGEST WINDS SHOULD STILL REMAIN
NEAR HIGH WIND WARNING CRITERIA...ESPECIALLY FOR AREAS NEAR THE
LAKE. DID EXTEND THE CURRENT HIGH WIND WARNING TO 10 PM...BUT WILL
POSSIBLY OBSERVE A FURTHER DIMINISHING TREND PRIOR TO THIS HOUR.

RODRIGUEZ

&&

.SHORT TERM...
307 PM CDT

THROUGH TONIGHT...

NO CHANGES PLANNED WITH HEADLINES.

SEVERAL BANDS OF LAKE EFFECT SNOW HAVE DEVELOPED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON...WITH SOME OF THESE SNOW SHOWERS
IMPACTING PORTIONS OF THE NORTHEASTERN ILLINOIS SHORES.
HOWEVER...THE MOST SUBSTANTIAL AREA OF LAKE EFFECT RAIN AND SNOW HAS
BEEN OCCURRING ALONG THE SOUTHERN TIP OF LAKE MICHIGAN AND ACROSS THE
ADVISORY AREA OF NORTHWESTERN INDIANA. BASED ON NUMEROUS PHONE
CALLS ACROSS THIS AREA IT APPEARS AREAS NEAR THE LAKE ARE SLIGHTLY
WARMER...RESULTING IN A RAIN SNOW MIX. HOWEVER...AREAS ROUGHLY 20 TO
30 MILES INLAND (BASICALLY ALONG AND SOUTH OF A CROWN POINT TO
VALPARAISO INDIANA LINE) THE PRECIPITATION IS MAINLY IN THE FORM OF
SNOW. SEVERAL REPORTS OF ACCUMULATING SNOW HAVE BEEN RECEIVED SOUTH
OF THIS LINE...WITH LOW VISIBILITIES UNDER A MILE.

BASED ON CURRENT RADAR TRENDS AND SHORT RANGE HIRES GUIDANCE...IT
APPEARS THIS ACTIVITY WILL CONTINUE TO BE FOCUSED MAINLY ACROSS
NORTHWESTERN INDIANA FOR THE NEXT FEW HOURS...THROUGH LATE
AFTERNOON/EARLY THIS EVENING. HOWEVER...SOME OF THE LESS ORGANIZED LAKE
EFFECT SNOW SHOWERS WILL LIKELY IMPACT PORTIONS OF COOK AND LAKE
COUNTIES IN ILLINOIS AS WELL DURING THIS TIME. FINALLY...AS THE
SURFACE LOW SHIFTS SOUTHEAST OVER THE OHIO VALLEY INTO THIS EVENING
THE BOUNDARY LAYER FLOW WILL VEER AND WEAKEN A BIT. THIS SHOULD
ALLOW THE BETTER FOCUS FOR LAKE EFFECT SHOWERS TO SHIFT FARTHER WEST
ACROSS PORTIONS OF EASTERN ILLINOIS...INCLUDING THE CHICAGO METRO
AREA NEAR THE LAKE. WHILE THERE COULD BE A SHORT PERIOD OF SOME
MODERATE...OR EVEN BRIEFLY HEAVY SNOW SHOWERS INTO NORTHEASTERN
ILLINOIS INTO THIS EVENING...I HAVE CHOSEN NOT TO EXTEND THE WINTER
ADVISORIES FARTHER WEST INTO ILLINOIS. THIS IS MAINLY DUE TO THE
FACT THAT IT APPEARS THE THREAT FOR BETTER MORE ORGANIZED LAKE
EFFECT SNOW WILL BE OF SHORT DURATION...LIMITING OVERALL
ACCUMULATIONS. HEIGHT RISES AND WARMING TEMPERATURES IN THE MID
LEVELS SHOULD ALLOW INVERSION HEIGHTS TO DROP BELOW THE DENDRITIC
GROWTH ZONE BY LATER THIS EVENING/OVERNIGHT. THE MODELS HAVE BEEN
INSISTENT ON THIS FOR THE PAST FEW DAYS AND SEE NO REASON WHY THIS
WOULD NOT OCCUR AS THE UPPER RIDGE TO OUR WEST BEGINS TO BUILD
EASTWARD. THEREFORE...ANY LEFT OVER LAKE EFFECT SNOW SHOWERS WILL
LIKELY NOT BE EFFICIENT SNOWFALL PRODUCERS AND LIKELY BE LOOSELY
ORGANIZED...AND HENCE THE THREAT FOR ACCUMULATING SNOWFALL SHOULD
COME TO AN END BY LATER THIS EVENING.

THE WINDS WITH THIS SYSTEM HAVE BEEN IMPRESSIVE. KGYY HAS BEEN
EXPERIENCING GUSTS TO 58 KT FOR SEVERAL HOURS...WITH SIMILAR
MAGNITUDES NOTED ALONG THE LAKE SHORE. IT APPEARS THESE STRONG WINDS
WILL SLOWLY EASE TONIGHT AS THE SURFACE HIGH OVERSPREADS THE AREA ON
SATURDAY. THEREFORE...NO CHANGES ARE PLANNED WITH THE CURRENT WIND
ADVISORIES OR WARNINGS.

LAKE SHORE FLOODING CONTINUES TO BE AN ISSUE...ESPECIALLY IN
CHICAGO...WHERE WAVES HAVE BEEN GETTING WATER ONTO LAKE SHORE DRIVE.
WE CONSIDERED TO UPGRADE TO A LAKE SHORE FLOOD WARNING...BUT DECIDED
TO JUST BEEF UP THE WORDING IN THE CURRENT ADVISORY AS A WARNING
WOULD NOT DUE MUCH GOOD AT THIS STAGE OF THE GAME.

KJB

&&

.LONG TERM...
307 PM CDT

TOMORROW THROUGH THURSDAY...

SATURDAY AND SUNDAY...
THE UPPER LEVEL TROUGH PUSHES EAST ALLOWING A LARGE UPPER LEVEL
RIDGE TO MOVE OVERHEAD THROUGH THE WEEKEND. THE CORRESPONDING
SURFACE HIGH MOVES OVER THE REGION TOMORROW EVENING.

GUIDANCE CONTINUES TO FEATURE A NARROW CONVERGENCE BAND ALONG THE
SOUTHWEST END OF LAKE MICHIGAN EARLY SATURDAY MORNING.  KEPT A
SLIGHT CHANCE OF PRECIP IN FOR FAR NORTHEAST IL WITH THE BAND
DISSIPATING BY LATE MORNING/EARLY AFTERNOON AS FORCING AND MOISTURE
WEAKEN. NOT EXPECTING ANY ADDITIONAL SIGNIFICANT ACCUMULATION AND
THE PRECIP TYPE WILL BE A SNOW/RAIN MIX AS TEMPERATURES WILL BE
ABOVE FREEZING OVER THE LAKE.  HAVE MEDIUM CONFIDENCE IN THE BAND
PERSISTING UNTIL MORNING...MEDIUM HIGH CONFIDENCE IN THE BAND MAINLY
IMPACTING THE IL SIDE OF THE LAKE...AND HIGH CONFIDENCE IN LITTLE TO
NO ADDITIONAL ACCUMULATION.

WINDS DECREASE SATURDAY AS THE HIGH MOVES OVERHEAD.  WARMER AIR
BEGINS TO MOVE IN AS WELL WITH HIGHS IN THE LOW 40S TOMORROW. WINDS
TURN SOUTH BEHIND THE HIGH SUNDAY AND USHER IN EVEN WARMER AIR WITH
HIGHS IN THE UPPER 40S TO AROUND 50. SATURDAY AFTERNOON THROUGH
SUNDAY NIGHT WILL BE DRY.

MONDAY THROUGH THURSDAY...
THE RIDGE AXIS MOVES OVERHEAD MONDAY AS THE SURFACE LOW SLIDES OVER
THE SE U.S. THE WARM-UP CONTINUES WITH HIGHS IN THE UPPER 50S TO
AROUND 60 MONDAY...AND MID 50S EXPECTED THROUGH MID WEEK. OVERNIGHT
LOWS VARY FROM THE MID 40S MONDAY NIGHT TO THE MID TO LOWER 30S
THURSDAY NIGHT.

A SURFACE LOW MOVES INTO ONTARIO TUESDAY...AND IT DRAGS A COLD FRONT
ACROSS THE REGION TUESDAY. EXPECTING WIDESPREAD SHOWERS TUESDAY
MORNING WITH RAIN ENDING FROM WEST TO EAST AS THE FRONT SLIDES EAST
TUESDAY EVENING/NIGHT.  GUIDANCE DIFFERS ON HOW MUCH PRECIP WILL
FALL...BUT ITS LOOKING LIKE A GOOD WETTING RAIN IS EXPECTED.

A WEAKER LOW PASSES JUST TO OUR NORTH MID WEEK AND HAVE MEDIUM-LOW
CONFIDENCE IN PRECIP MAKING IT INTO NORTHERN IL WEDNESDAY. THINKING
PRECIP WILL REMAIN CLOSELY TIED TO THE LOW WHICH RIGHT NOW WILL BE
OVER SOUTHERN WI. IF THE LOW/S TRACK WERE TO DIP A BIT MORE
SOUTH...THERE WOULD BE A BETTER CHANCE FOR PRECIP ACROSS FAR
NORTHERN IL.

WINDS TURN NORTHWEST BEHIND THE LOW AND ANOTHER LAKE EFFECT PRECIP
SITUATION IS POSSIBLE FOR NW INDIANA WEDNESDAY NIGHT. ONLY HAVE RAIN
FOR NOW AS TEMPS WILL BE ABOVE FREEZING.  WINDS REMAIN OFF OF THE
LAKE THROUGH THURSDAY NIGHT AS ANOTHER HIGH PRESSURE SYSTEM
APPROACHES FROM THE WEST.

JEE

&&

.AVIATION...

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

* VERY GUSTY NORTH WINDS WITH GUSTS IN EXCESS OF 30 KT INTO EARLY
  EVENING...01-02Z.

* LAKE EFFECT RAIN/SNOW SHOWERS AT MDW WITH OCCASIONAL IFR VIS AT
  MDW THIS AFTERNOON...DRIFTING WEST INTO ORD THIS EVENING.

* INTENSIFYING LAKE EFFECT SNOW SHOWERS PROBABLE OVER MDW LATER
  THIS EVE. SNOW SHOWERS PERSISTING POSSIBLY AS LONG AS EARLY
  SATURDAY MORNING. SNOW SHOWERS POSSIBLE AT ORD.

* CIGS TEMPORARY TO 1500-3000 FT AT MDW LATE THIS AFTERNOON. CIGS
  GRADUALLY LOWERING TO 1500-2500 FT AT BOTH AIRPORTS LATER
  TONIGHT.

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

VERY GUSTY NORTH-NORTHWEST WINDS WILL CONTINUE THROUGH THIS
AFTERNOON AS COLD AIR CONTINUES TO REPLENISH ITSELF. GUSTS OF 33
TO 40 KT...WITH EVEN SPORADICALLY HIGHER ARE HIGHLY LIKELY TO BE
COMMON THROUGH THE AFTERNOON. DURING THE AFTERNOON...DUE TO THE
ORIENTATION OF THE PRESSURE GRADIENT...THE WIND DIRECTION IS
EXPECTED TO SHIFT TO 360 DEGREES AT CHICAGOLAND TAF SITES. LAKE
EFFECT SNOW...MAYBE AT TIMES RAIN...WILL CONTINUE TO IMPACT GARY
THROUGHOUT THIS AFTERNOON AND TONIGHT. WITH SOME BANDING
POTENTIAL THIS EVE VISIBILITY COULD DROP QUITE LOW DURING THAT
PERIOD. THE SNOW BAND...OR AREA OF SHOWERS...WILL BEGIN TO INCH
BACK WESTWARD THIS EVE INTO OVERNIGHT. THE INTENSITY OF SNOW COULD
STILL BE FAIRLY IMPRESSIVE AT MDW LATER THIS EVE...ALTHOUGH A
DECENT AMOUNT OF UNCERTAINTY EXISTS THERE. AT LEAST LAKE-INDUCED
CLOUDS ARE LIKELY OVER NORTHEAST ILLINOIS SATURDAY MORNING
ALTHOUGH THERE COULD CONTINUE SOME SNOW SHOWERS TOO. AT THE SAME
TIME WINDS ARE FAVORED TO BE BETWEEN 360-020 DEGREES...SO IMPACTS
TO ORD OPERATIONS COULD CONTINUE THROUGH SATURDAY MORNING.

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

* HIGH IN WIND SPEEDS AND DIRECTION THROUGH 00Z. MEDIUM THEREAFTER.

* MEDIUM IN HOW FAR VISIBILITY WILL DROP IN SNOW SHOWERS LATE THIS
  AFTERNOON AND EARLY THIS EVE.

* MEDIUM IN SNOW SHOWERS IMPACTING MDW LATER TONIGHT AND LOW FOR
  ORD. LOW IN HOW FAR VISIBILITY WILL DROP AT EITHER AIRPORT.

* MEDIUM IN CIGS THROUGH TAF.

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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MTF

&&

.MARINE...
212 PM CDT

STORM FORCE WINDS WILL SLOWLY EASE TO GALES TONIGHT. NO CHANGES
PLANNED TO CURRENT HEADLINES.

FOR THE NEARSHORE ZONES...WILL NEED A PROLONGED SMALL CRAFT ADVISORY
THROUGH AT LEAST SATURDAY AS VERY LARGE WAVES SUBSIDE.  MAY FLIRT
WITH SMALL CRAFT ADVISORY CRITERIA WINDS AND WAVES SUNDAY AND
MONDAY. HAVE MEDIUM CONFIDENCE AS CONDITIONS MAY BE MARGINAL.

NORTH TO NORTHEAST WINDS TO 30 KT SLOWLY DIMINISH SATURDAY AND WINDS
TURN SOUTHWEST BEHIND A HIGH PRESSURE SYSTEM SUNDAY MORNING.  SOUTH
TO SOUTHWEST WINDS INCREASE TO 30 KT SUNDAY AFTERNOON AS THE
GRADIENT TIGHTENS BETWEEN THE DEPARTING HIGH AND AN APPROACHING
LOW.  SOUTH TO SOUTHWEST WINDS FINALLY DIMINISH TO UNDER 30 KT
MONDAY NIGHT...AND THEN WINDS TURN WEST 10-20 KT BEHIND THE LOWS
COLD FRONT TUESDAY. WEST WINDS INCREASE TO 20-25 KT AND BECOME
NORTHWEST WEDNESDAY NIGHT...AND MAY SEE 30 KT WINDS OVER THE
NORTHERN HALF OF THE LAKE THURSDAY.  WINDS DIMINISH THURSDAY NIGHT
AS HIGH PRESSURE MOVES OVER THE AREA.

KJB/JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 10 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 4 AM
     SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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 312207
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
507 PM CDT FRI OCT 31 2014

.SHORT TERM...
307 PM CDT

THROUGH TONIGHT...

NO CHANGES PLANNED WITH HEADLINES.

SEVERAL BANDS OF LAKE EFFECT SNOW HAVE DEVELOPED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON...WITH SOME OF THESE SNOW SHOWERS
IMPACTING PORTIONS OF THE NORTHEASTERN ILLINOIS SHORES.
HOWEVER...THE MOST SUBSTANTIAL AREA OF LAKE EFFECT RAIN AND SNOW HAS
BEEN OCCURRING ALONG THE SOUTHERN TIP OF LAKE MICHIGAN AND ACROSS THE
ADVISORY AREA OF NORTHWESTERN INDIANA. BASED ON NUMEROUS PHONE
CALLS ACROSS THIS AREA IT APPEARS AREAS NEAR THE LAKE ARE SLIGHTLY
WARMER...RESULTING IN A RAIN SNOW MIX. HOWEVER...AREAS ROUGHLY 20 TO
30 MILES INLAND (BASICALLY ALONG AND SOUTH OF A CROWN POINT TO
VALPARAISO INDIANA LINE) THE PRECIPITATION IS MAINLY IN THE FORM OF
SNOW. SEVERAL REPORTS OF ACCUMULATING SNOW HAVE BEEN RECEIVED SOUTH
OF THIS LINE...WITH LOW VISIBILITIES UNDER A MILE.

BASED ON CURRENT RADAR TRENDS AND SHORT RANGE HIRES GUIDANCE...IT
APPEARS THIS ACTIVITY WILL CONTINUE TO BE FOCUSED MAINLY ACROSS
NORTHWESTERN INDIANA FOR THE NEXT FEW HOURS...THROUGH LATE
AFTERNOON/EARLY THIS EVENING. HOWEVER...SOME OF THE LESS ORGANIZED LAKE
EFFECT SNOW SHOWERS WILL LIKELY IMPACT PORTIONS OF COOK AND LAKE
COUNTIES IN ILLINOIS AS WELL DURING THIS TIME. FINALLY...AS THE
SURFACE LOW SHIFTS SOUTHEAST OVER THE OHIO VALLEY INTO THIS EVENING
THE BOUNDARY LAYER FLOW WILL VEER AND WEAKEN A BIT. THIS SHOULD
ALLOW THE BETTER FOCUS FOR LAKE EFFECT SHOWERS TO SHIFT FARTHER WEST
ACROSS PORTIONS OF EASTERN ILLINOIS...INCLUDING THE CHICAGO METRO
AREA NEAR THE LAKE. WHILE THERE COULD BE A SHORT PERIOD OF SOME
MODERATE...OR EVEN BRIEFLY HEAVY SNOW SHOWERS INTO NORTHEASTERN
ILLINOIS INTO THIS EVENING...I HAVE CHOSEN NOT TO EXTEND THE WINTER
ADVISORIES FARTHER WEST INTO ILLINOIS. THIS IS MAINLY DUE TO THE
FACT THAT IT APPEARS THE THREAT FOR BETTER MORE ORGANIZED LAKE
EFFECT SNOW WILL BE OF SHORT DURATION...LIMITING OVERALL
ACCUMULATIONS. HEIGHT RISES AND WARMING TEMPERATURES IN THE MID
LEVELS SHOULD ALLOW INVERSION HEIGHTS TO DROP BELOW THE DENDRITIC
GROWTH ZONE BY LATER THIS EVENING/OVERNIGHT. THE MODELS HAVE BEEN
INSISTENT ON THIS FOR THE PAST FEW DAYS AND SEE NO REASON WHY THIS
WOULD NOT OCCUR AS THE UPPER RIDGE TO OUR WEST BEGINS TO BUILD
EASTWARD. THEREFORE...ANY LEFT OVER LAKE EFFECT SNOW SHOWERS WILL
LIKELY NOT BE EFFICIENT SNOWFALL PRODUCERS AND LIKELY BE LOOSELY
ORGANIZED...AND HENCE THE THREAT FOR ACCUMULATING SNOWFALL SHOULD
COME TO AN END BY LATER THIS EVENING.

THE WINDS WITH THIS SYSTEM HAVE BEEN IMPRESSIVE. KGYY HAS BEEN
EXPERIENCING GUSTS TO 58 KT FOR SEVERAL HOURS...WITH SIMILAR
MAGNITUDES NOTED ALONG THE LAKE SHORE. IT APPEARS THESE STRONG WINDS
WILL SLOWLY EASE TONIGHT AS THE SURFACE HIGH OVERSPREADS THE AREA ON
SATURDAY. THEREFORE...NO CHANGES ARE PLANNED WITH THE CURRENT WIND
ADVISORIES OR WARNINGS.

LAKE SHORE FLOODING CONTINUES TO BE AN ISSUE...ESPECIALLY IN
CHICAGO...WHERE WAVES HAVE BEEN GETTING WATER ONTO LAKE SHORE DRIVE.
WE CONSIDERED TO UPGRADE TO A LAKE SHORE FLOOD WARNING...BUT DECIDED
TO JUST BEEF UP THE WORDING IN THE CURRENT ADVISORY AS A WARNING
WOULD NOT DUE MUCH GOOD AT THIS STAGE OF THE GAME.

KJB

&&

.LONG TERM...
307 PM CDT

TOMORROW THROUGH THURSDAY...

SATURDAY AND SUNDAY...
THE UPPER LEVEL TROUGH PUSHES EAST ALLOWING A LARGE UPPER LEVEL
RIDGE TO MOVE OVERHEAD THROUGH THE WEEKEND. THE CORRESPONDING
SURFACE HIGH MOVES OVER THE REGION TOMORROW EVENING.

GUIDANCE CONTINUES TO FEATURE A NARROW CONVERGENCE BAND ALONG THE
SOUTHWEST END OF LAKE MICHIGAN EARLY SATURDAY MORNING.  KEPT A
SLIGHT CHANCE OF PRECIP IN FOR FAR NORTHEAST IL WITH THE BAND
DISSIPATING BY LATE MORNING/EARLY AFTERNOON AS FORCING AND MOISTURE
WEAKEN. NOT EXPECTING ANY ADDITIONAL SIGNIFICANT ACCUMULATION AND
THE PRECIP TYPE WILL BE A SNOW/RAIN MIX AS TEMPERATURES WILL BE
ABOVE FREEZING OVER THE LAKE.  HAVE MEDIUM CONFIDENCE IN THE BAND
PERSISTING UNTIL MORNING...MEDIUM HIGH CONFIDENCE IN THE BAND MAINLY
IMPACTING THE IL SIDE OF THE LAKE...AND HIGH CONFIDENCE IN LITTLE TO
NO ADDITIONAL ACCUMULATION.

WINDS DECREASE SATURDAY AS THE HIGH MOVES OVERHEAD.  WARMER AIR
BEGINS TO MOVE IN AS WELL WITH HIGHS IN THE LOW 40S TOMORROW. WINDS
TURN SOUTH BEHIND THE HIGH SUNDAY AND USHER IN EVEN WARMER AIR WITH
HIGHS IN THE UPPER 40S TO AROUND 50. SATURDAY AFTERNOON THROUGH
SUNDAY NIGHT WILL BE DRY.

MONDAY THROUGH THURSDAY...
THE RIDGE AXIS MOVES OVERHEAD MONDAY AS THE SURFACE LOW SLIDES OVER
THE SE U.S. THE WARM-UP CONTINUES WITH HIGHS IN THE UPPER 50S TO
AROUND 60 MONDAY...AND MID 50S EXPECTED THROUGH MID WEEK. OVERNIGHT
LOWS VARY FROM THE MID 40S MONDAY NIGHT TO THE MID TO LOWER 30S
THURSDAY NIGHT.

A SURFACE LOW MOVES INTO ONTARIO TUESDAY...AND IT DRAGS A COLD FRONT
ACROSS THE REGION TUESDAY. EXPECTING WIDESPREAD SHOWERS TUESDAY
MORNING WITH RAIN ENDING FROM WEST TO EAST AS THE FRONT SLIDES EAST
TUESDAY EVENING/NIGHT.  GUIDANCE DIFFERS ON HOW MUCH PRECIP WILL
FALL...BUT ITS LOOKING LIKE A GOOD WETTING RAIN IS EXPECTED.

A WEAKER LOW PASSES JUST TO OUR NORTH MID WEEK AND HAVE MEDIUM-LOW
CONFIDENCE IN PRECIP MAKING IT INTO NORTHERN IL WEDNESDAY. THINKING
PRECIP WILL REMAIN CLOSELY TIED TO THE LOW WHICH RIGHT NOW WILL BE
OVER SOUTHERN WI. IF THE LOW/S TRACK WERE TO DIP A BIT MORE
SOUTH...THERE WOULD BE A BETTER CHANCE FOR PRECIP ACROSS FAR
NORTHERN IL.

WINDS TURN NORTHWEST BEHIND THE LOW AND ANOTHER LAKE EFFECT PRECIP
SITUATION IS POSSIBLE FOR NW INDIANA WEDNESDAY NIGHT. ONLY HAVE RAIN
FOR NOW AS TEMPS WILL BE ABOVE FREEZING.  WINDS REMAIN OFF OF THE
LAKE THROUGH THURSDAY NIGHT AS ANOTHER HIGH PRESSURE SYSTEM
APPROACHES FROM THE WEST.

JEE

&&

.AVIATION...

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

* VERY GUSTY NORTH WINDS WITH GUSTS IN EXCESS OF 30 KT INTO EARLY
  EVENING...01-02Z.


* LAKE EFFECT RAIN/SNOW SHOWERS AT MDW WITH OCCASIONAL IFR VIS AT
  MDW THIS AFTERNOON...DRIFTING WEST INTO ORD THIS EVENING.

* INTENSIFYING LAKE EFFECT SNOW SHOWERS PROBABLE OVER MDW LATER
  THIS EVE. SNOW SHOWERS PERSISTING POSSIBLY AS LONG AS EARLY
  SATURDAY MORNING. SNOW SHOWERS POSSIBLE AT ORD.

* CIGS TEMPORARY TO 1500-3000 FT AT MDW LATE THIS AFTERNOON. CIGS
  GRADUALLY LOWERING TO 1500-2500 FT AT BOTH AIRPORTS LATER
  TONIGHT.

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

VERY GUSTY NORTH-NORTHWEST WINDS WILL CONTINUE THROUGH THIS
AFTERNOON AS COLD AIR CONTINUES TO REPLENISH ITSELF. GUSTS OF 33
TO 40 KT...WITH EVEN SPORADICALLY HIGHER ARE HIGHLY LIKELY TO BE
COMMON THROUGH THE AFTERNOON. DURING THE AFTERNOON...DUE TO THE
ORIENTATION OF THE PRESSURE GRADIENT...THE WIND DIRECTION IS
EXPECTED TO SHIFT TO 360 DEGREES AT CHICAGOLAND TAF SITES. LAKE
EFFECT SNOW...MAYBE AT TIMES RAIN...WILL CONTINUE TO IMPACT GARY
THROUGHOUT THIS AFTERNOON AND TONIGHT. WITH SOME BANDING
POTENTIAL THIS EVE VISIBILITY COULD DROP QUITE LOW DURING THAT
PERIOD. THE SNOW BAND...OR AREA OF SHOWERS...WILL BEGIN TO INCH
BACK WESTWARD THIS EVE INTO OVERNIGHT. THE INTENSITY OF SNOW COULD
STILL BE FAIRLY IMPRESSIVE AT MDW LATER THIS EVE...ALTHOUGH A
DECENT AMOUNT OF UNCERTAINTY EXISTS THERE. AT LEAST LAKE-INDUCED
CLOUDS ARE LIKELY OVER NORTHEAST ILLINOIS SATURDAY MORNING
ALTHOUGH THERE COULD CONTINUE SOME SNOW SHOWERS TOO. AT THE SAME
TIME WINDS ARE FAVORED TO BE BETWEEN 360-020 DEGREES...SO IMPACTS
TO ORD OPERATIONS COULD CONTINUE THROUGH SATURDAY MORNING.

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

* HIGH IN WIND SPEEDS AND DIRECTION THROUGH 00Z. MEDIUM THEREAFTER.

* MEDIUM IN HOW FAR VISIBILITY WILL DROP IN SNOW SHOWERS LATE THIS
  AFTERNOON AND EARLY THIS EVE.

* MEDIUM IN SNOW SHOWERS IMPACTING MDW LATER TONIGHT AND LOW FOR
  ORD. LOW IN HOW FAR VISIBILITY WILL DROP AT EITHER AIRPORT.

* MEDIUM IN CIGS THROUGH TAF.

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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MTF

&&

.MARINE...
212 PM CDT

STORM FORCE WINDS WILL SLOWLY EASE TO GALES TONIGHT. NO CHANGES
PLANNED TO CURRENT HEADLINES.

FOR THE NEARSHORE ZONES...WILL NEED A PROLONGED SMALL CRAFT ADVISORY
THROUGH AT LEAST SATURDAY AS VERY LARGE WAVES SUBSIDE.  MAY FLIRT
WITH SMALL CRAFT ADVISORY CRITERIA WINDS AND WAVES SUNDAY AND
MONDAY. HAVE MEDIUM CONFIDENCE AS CONDITIONS MAY BE MARGINAL.

NORTH TO NORTHEAST WINDS TO 30 KT SLOWLY DIMINISH SATURDAY AND WINDS
TURN SOUTHWEST BEHIND A HIGH PRESSURE SYSTEM SUNDAY MORNING.  SOUTH
TO SOUTHWEST WINDS INCREASE TO 30 KT SUNDAY AFTERNOON AS THE
GRADIENT TIGHTENS BETWEEN THE DEPARTING HIGH AND AN APPROACHING
LOW.  SOUTH TO SOUTHWEST WINDS FINALLY DIMINISH TO UNDER 30 KT
MONDAY NIGHT...AND THEN WINDS TURN WEST 10-20 KT BEHIND THE LOWS
COLD FRONT TUESDAY. WEST WINDS INCREASE TO 20-25 KT AND BECOME
NORTHWEST WEDNESDAY NIGHT...AND MAY SEE 30 KT WINDS OVER THE
NORTHERN HALF OF THE LAKE THURSDAY.  WINDS DIMINISH THURSDAY NIGHT
AS HIGH PRESSURE MOVES OVER THE AREA.

KJB/JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 4 AM
     SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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 312008
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
308 PM CDT FRI OCT 31 2014

.SHORT TERM...
307 PM CDT

THROUGH TONIGHT...

NO CHANGES PLANNED WITH HEADLINES.

SEVERAL BANDS OF LAKE EFFECT SNOW HAVE DEVELOPED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON...WITH SOME OF THESE SNOW SHOWERS
IMPACTING PORTIONS OF THE NORTHEASTERN ILLINOIS SHORES.
HOWEVER...THE MOST SUBSTANTIAL AREA OF LAKE EFFECT RAIN AND SNOW HAS
BEEN OCCURRING ALONG THE SOUTHERN TIP OF LAKE MICHIGAN AND ACROSS THE
ADVISORY AREA OF NORTHWESTERN INDIANA. BASED ON NUMEROUS PHONE
CALLS ACROSS THIS AREA IT APPEARS AREAS NEAR THE LAKE ARE SLIGHTLY
WARMER...RESULTING IN A RAIN SNOW MIX. HOWEVER...AREAS ROUGHLY 20 TO
30 MILES INLAND (BASICALLY ALONG AND SOUTH OF A CROWN POINT TO
VALPARAISO INDIANA LINE) THE PRECIPITATION IS MAINLY IN THE FORM OF
SNOW. SEVERAL REPORTS OF ACCUMULATING SNOW HAVE BEEN RECEIVED SOUTH
OF THIS LINE...WITH LOW VISIBILITIES UNDER A MILE.

BASED ON CURRENT RADAR TRENDS AND SHORT RANGE HIRES GUIDANCE...IT
APPEARS THIS ACTIVITY WILL CONTINUE TO BE FOCUSED MAINLY ACROSS
NORTHWESTERN INDIANA FOR THE NEXT FEW HOURS...THROUGH LATE
AFTERNOON/EARLY THIS EVENING. HOWEVER...SOME OF THE LESS ORGANIZED LAKE
EFFECT SNOW SHOWERS WILL LIKELY IMPACT PORTIONS OF COOK AND LAKE
COUNTIES IN ILLINOIS AS WELL DURING THIS TIME. FINALLY...AS THE
SURFACE LOW SHIFTS SOUTHEAST OVER THE OHIO VALLEY INTO THIS EVENING
THE BOUNDARY LAYER FLOW WILL VEER AND WEAKEN A BIT. THIS SHOULD
ALLOW THE BETTER FOCUS FOR LAKE EFFECT SHOWERS TO SHIFT FARTHER WEST
ACROSS PORTIONS OF EASTERN ILLINOIS...INCLUDING THE CHICAGO METRO
AREA NEAR THE LAKE. WHILE THERE COULD BE A SHORT PERIOD OF SOME
MODERATE...OR EVEN BRIEFLY HEAVY SNOW SHOWERS INTO NORTHEASTERN
ILLINOIS INTO THIS EVENING...I HAVE CHOSEN NOT TO EXTEND THE WINTER
ADVISORIES FARTHER WEST INTO ILLINOIS. THIS IS MAINLY DUE TO THE
FACT THAT IT APPEARS THE THREAT FOR BETTER MORE ORGANIZED LAKE
EFFECT SNOW WILL BE OF SHORT DURATION...LIMITING OVERALL
ACCUMULATIONS. HEIGHT RISES AND WARMING TEMPERATURES IN THE MID
LEVELS SHOULD ALLOW INVERSION HEIGHTS TO DROP BELOW THE DENDRITIC
GROWTH ZONE BY LATER THIS EVENING/OVERNIGHT. THE MODELS HAVE BEEN
INSISTENT ON THIS FOR THE PAST FEW DAYS AND SEE NO REASON WHY THIS
WOULD NOT OCCUR AS THE UPPER RIDGE TO OUR WEST BEGINS TO BUILD
EASTWARD. THEREFORE...ANY LEFT OVER LAKE EFFECT SNOW SHOWERS WILL
LIKELY NOT BE EFFICIENT SNOWFALL PRODUCERS AND LIKELY BE LOOSELY
ORGANIZED...AND HENCE THE THREAT FOR ACCUMULATING SNOWFALL SHOULD
COME TO AN END BY LATER THIS EVENING.

THE WINDS WITH THIS SYSTEM HAVE BEEN IMPRESSIVE. KGYY HAS BEEN
EXPERIENCING GUSTS TO 58 KT FOR SEVERAL HOURS...WITH SIMILAR
MAGNITUDES NOTED ALONG THE LAKE SHORE. IT APPEARS THESE STRONG WINDS
WILL SLOWLY EASE TONIGHT AS THE SURFACE HIGH OVERSPREADS THE AREA ON
SATURDAY. THEREFORE...NO CHANGES ARE PLANNED WITH THE CURRENT WIND
ADVISORIES OR WARNINGS.

LAKE SHORE FLOODING CONTINUES TO BE AN ISSUE...ESPECIALLY IN
CHICAGO...WHERE WAVES HAVE BEEN GETTING WATER ONTO LAKE SHORE DRIVE.
WE CONSIDERED TO UPGRADE TO A LAKE SHORE FLOOD WARNING...BUT DECIDED
TO JUST BEEF UP THE WORDING IN THE CURRENT ADVISORY AS A WARNING
WOULD NOT DUE MUCH GOOD AT THIS STAGE OF THE GAME.

KJB

&&

.LONG TERM...
307 PM CDT

TOMORROW THROUGH THURSDAY...

SATURDAY AND SUNDAY...
THE UPPER LEVEL TROUGH PUSHES EAST ALLOWING A LARGE UPPER LEVEL
RIDGE TO MOVE OVERHEAD THROUGH THE WEEKEND. THE CORRESPONDING
SURFACE HIGH MOVES OVER THE REGION TOMORROW EVENING.

GUIDANCE CONTINUES TO FEATURE A NARROW CONVERGENCE BAND ALONG THE
SOUTHWEST END OF LAKE MICHIGAN EARLY SATURDAY MORNING.  KEPT A
SLIGHT CHANCE OF PRECIP IN FOR FAR NORTHEAST IL WITH THE BAND
DISSIPATING BY LATE MORNING/EARLY AFTERNOON AS FORCING AND MOISTURE
WEAKEN. NOT EXPECTING ANY ADDITIONAL SIGNIFICANT ACCUMULATION AND
THE PRECIP TYPE WILL BE A SNOW/RAIN MIX AS TEMPERATURES WILL BE
ABOVE FREEZING OVER THE LAKE.  HAVE MEDIUM CONFIDENCE IN THE BAND
PERSISTING UNTIL MORNING...MEDIUM HIGH CONFIDENCE IN THE BAND MAINLY
IMPACTING THE IL SIDE OF THE LAKE...AND HIGH CONFIDENCE IN LITTLE TO
NO ADDITIONAL ACCUMULATION.

WINDS DECREASE SATURDAY AS THE HIGH MOVES OVERHEAD.  WARMER AIR
BEGINS TO MOVE IN AS WELL WITH HIGHS IN THE LOW 40S TOMORROW. WINDS
TURN SOUTH BEHIND THE HIGH SUNDAY AND USHER IN EVEN WARMER AIR WITH
HIGHS IN THE UPPER 40S TO AROUND 50. SATURDAY AFTERNOON THROUGH
SUNDAY NIGHT WILL BE DRY.

MONDAY THROUGH THURSDAY...
THE RIDGE AXIS MOVES OVERHEAD MONDAY AS THE SURFACE LOW SLIDES OVER
THE SE U.S. THE WARM-UP CONTINUES WITH HIGHS IN THE UPPER 50S TO
AROUND 60 MONDAY...AND MID 50S EXPECTED THROUGH MID WEEK. OVERNIGHT
LOWS VARY FROM THE MID 40S MONDAY NIGHT TO THE MID TO LOWER 30S
THURSDAY NIGHT.

A SURFACE LOW MOVES INTO ONTARIO TUESDAY...AND IT DRAGS A COLD FRONT
ACROSS THE REGION TUESDAY. EXPECTING WIDESPREAD SHOWERS TUESDAY
MORNING WITH RAIN ENDING FROM WEST TO EAST AS THE FRONT SLIDES EAST
TUESDAY EVENING/NIGHT.  GUIDANCE DIFFERS ON HOW MUCH PRECIP WILL
FALL...BUT ITS LOOKING LIKE A GOOD WETTING RAIN IS EXPECTED.

A WEAKER LOW PASSES JUST TO OUR NORTH MID WEEK AND HAVE MEDIUM-LOW
CONFIDENCE IN PRECIP MAKING IT INTO NORTHERN IL WEDNESDAY. THINKING
PRECIP WILL REMAIN CLOSELY TIED TO THE LOW WHICH RIGHT NOW WILL BE
OVER SOUTHERN WI. IF THE LOW/S TRACK WERE TO DIP A BIT MORE
SOUTH...THERE WOULD BE A BETTER CHANCE FOR PRECIP ACROSS FAR
NORTHERN IL.

WINDS TURN NORTHWEST BEHIND THE LOW AND ANOTHER LAKE EFFECT PRECIP
SITUATION IS POSSIBLE FOR NW INDIANA WEDNESDAY NIGHT. ONLY HAVE RAIN
FOR NOW AS TEMPS WILL BE ABOVE FREEZING.  WINDS REMAIN OFF OF THE
LAKE THROUGH THURSDAY NIGHT AS ANOTHER HIGH PRESSURE SYSTEM
APPROACHES FROM THE WEST.


JEE

&&

.AVIATION...

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

* VERY GUSTY NORTH-NORTHWEST WINDS GRADUALLY SHIFTING TO DUE NORTH
  BY LATE AFTERNOON. SPORADIC GUSTS IN EXCESS OF 40 KT THROUGH
  22Z.

* LIKELIHOOD FOR PERIODIC LAKE EFFECT RAIN/SNOW SHOWERS AT MDW
  THROUGH THE REST OF THE AFTERNOON AND EARLY EVE...POSSIBLE AT
  ORD.

* INTENSIFYING LAKE EFFECT SNOW SHOWERS PROBABLE OVER MDW LATER
  THIS EVE. SNOW SHOWERS PERSISTING POSSIBLY AS LONG AS EARLY
  SATURDAY MORNING. SNOW SHOWERS POSSIBLE AT ORD.

* CIGS TEMPORARY TO 1500-3000 FT AT MDW THIS AFTERNOON. CIGS
  GRADUALLY LOWERING TO 1500-2500 FT AT BOTH AIRPORTS LATER
  TONIGHT.


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

VERY GUSTY NORTH-NORTHWEST WINDS WILL CONTINUE THROUGH THIS
AFTERNOON AS COLD AIR CONTINUES TO REPLENISH ITSELF. GUSTS OF 33
TO 40 KT...WITH EVEN SPORADICALLY HIGHER ARE HIGHLY LIKELY TO BE
COMMON THROUGH THE AFTERNOON. DURING THE AFTERNOON...DUE TO THE
ORIENTATION OF THE PRESSURE GRADIENT...THE WIND DIRECTION IS
EXPECTED TO SHIFT TO 360 DEGREES AT CHICAGOLAND TAF SITES. LAKE
EFFECT SNOW...MAYBE AT TIMES RAIN...WILL CONTINUE TO IMPACT GARY
THROUGHOUT THIS AFTERNOON AND TONIGHT. WITH SOME BANDING
POTENTIAL THIS EVE VISIBILITY COULD DROP QUITE LOW DURING THAT
PERIOD. THE SNOW BAND...OR AREA OF SHOWERS...WILL BEGIN TO INCH
BACK WESTWARD THIS EVE INTO OVERNIGHT. THE INTENSITY OF SNOW COULD
STILL BE FAIRLY IMPRESSIVE AT MDW LATER THIS EVE...ALTHOUGH A
DECENT AMOUNT OF UNCERTAINTY EXISTS THERE. AT LEAST LAKE-INDUCED
CLOUDS ARE LIKELY OVER NORTHEAST ILLINOIS SATURDAY MORNING
ALTHOUGH THERE COULD CONTINUE SOME SNOW SHOWERS TOO. AT THE SAME
TIME WINDS ARE FAVORED TO BE BETWEEN 360-020 DEGREES...SO IMPACTS
TO ORD OPERATIONS COULD CONTINUE THROUGH SATURDAY MORNING.


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

* HIGH IN WIND SPEEDS AND DIRECTION THROUGH 00Z. MEDIUM THEREAFTER.

* MEDIUM IN HOW FAR VISIBILITY WILL DROP IN SNOW SHOWERS LATE THIS
  AFTERNOON AND EARLY THIS EVE.

* MEDIUM IN SNOW SHOWERS IMPACTING MDW LATER TONIGHT AND LOW FOR
  ORD. LOW IN HOW FAR VISIBILITY WILL DROP AT EITHER AIRPORT.

* MEDIUM IN CIGS THROUGH TAF.


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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MTF

&&

.MARINE...
212 PM CDT

STORM FORCE WINDS WILL SLOWLY EASE TO GALES TONIGHT. NO CHANGES
PLANNED TO CURRENT HEADLINES.

FOR THE NEARSHORE ZONES...WILL NEED A PROLONGED SMALL CRAFT ADVISORY
THROUGH AT LEAST SATURDAY AS VERY LARGE WAVES SUBSIDE.  MAY FLIRT
WITH SMALL CRAFT ADVISORY CRITERIA WINDS AND WAVES SUNDAY AND
MONDAY. HAVE MEDIUM CONFIDENCE AS CONDITIONS MAY BE MARGINAL.

NORTH TO NORTHEAST WINDS TO 30 KT SLOWLY DIMINISH SATURDAY AND WINDS
TURN SOUTHWEST BEHIND A HIGH PRESSURE SYSTEM SUNDAY MORNING.  SOUTH
TO SOUTHWEST WINDS INCREASE TO 30 KT SUNDAY AFTERNOON AS THE
GRADIENT TIGHTENS BETWEEN THE DEPARTING HIGH AND AN APPROACHING
LOW.  SOUTH TO SOUTHWEST WINDS FINALLY DIMINISH TO UNDER 30 KT
MONDAY NIGHT...AND THEN WINDS TURN WEST 10-20 KT BEHIND THE LOWS
COLD FRONT TUESDAY. WEST WINDS INCREASE TO 20-25 KT AND BECOME
NORTHWEST WEDNESDAY NIGHT...AND MAY SEE 30 KT WINDS OVER THE
NORTHERN HALF OF THE LAKE THURSDAY.  WINDS DIMINISH THURSDAY NIGHT
AS HIGH PRESSURE MOVES OVER THE AREA.

KJB/JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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 311804
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
104 PM CDT FRI OCT 31 2014

.MESOSCALE DISCUSSION...

WE ARE CURRENTLY WATCHING THE PROGRESS OF A SECONDARY INVERTED
SURFACE TROUGH...WHICH IS CURRENTLY RACING SOUTHWARD DOWN CENTRAL
LAKE MICHIGAN. OBSERVATIONS OVER AND NEAR THE LAKE INDICATE THE
PRESENCE OF GOOD CONVERGENCE ALONG THIS BOUNDARY. THE FIRST
MORNING VISIBLE SATELLITE IMAGES ALSO INDICATE CONVECTIVE
STRUCTURES DEVELOPING WITHIN THE BAND OF RAIN/SNOW SHOWERS
CURRENTLY SHIFTING SOUTHWARD JUST EAST OF MKE. OVERALL IT APPEARS
THIS AREA OF SNOWFALL WILL PIVOT SOUTHWARD ACROSS NORTHWESTERN
INDIANA WITHIN THE NEXT 2 HOURS (BY 1630Z). HOWEVER...I AM ALSO
CONCERNED THAT SOME OF THESE HEAVIER CONVECTIVE SNOW SHOWERS MAY
IMPACT PORTIONS OF NORTHEASTERN ILLINOIS...INCLUDING DOWNTOWN
CHICAGO THROUGH LATE MORNING. IN FACT...SOME OF THE LATEST RADAR
IMAGERY IS ALREADY INDICATING SOME BANDS OF PRECIP MOVING INTO
NORTHERN COOK COUNTY. IT APPEARS THE WINDS WILL BECOME MORE
NORTHERLY IN THE WAKE OF THIS SURFACE TROUGH...AND WIND SPEEDS
COULD ALSO INCREASE A BIT HIGHER THAN CURRENT WIND SPEEDS. WE WILL
CONTINUE TO WATCH OBSERVATION TRENDS...AND HANDLE THIS SNOWFALL
ACROSS THE CHICAGO AREA WITH GRAPHICAL NOWCASTS AT THIS TIME. IT
DOES APPEAR THIS INITIAL BURST OF SNOW WILL BE SOMEWHAT SHORT
LIVED ACROSS THE CHICAGO METRO AREA. WHILE SOME MINOR
ACCUMULATIONS ARE CERTAINLY POSSIBLE WITH THIS ACTIVITY...WE HAVE
NO IMMEDIATE PLANS TO EXPAND THE CURRENT WINTER WEATHER HEADLINES.

FOLLOWING THIS INITIAL BOUNDARY AND BURST OF SNOW...HI RES GUIDANCE
CONTINUES TO INDICATE THAT BANDS OF LAKE EFFECT RAIN/SNOW SHOWERS
WILL CONTINUE TO DEVELOP AND IMPACT MUCH OF THE AREAS CURRENTLY
UNDER THE WINTER HEADLINE ACROSS NORTHWESTERN INDIANA. HOWEVER...WE
WILL NEED TO WATCH FOR THE POTENTIAL OF THE LAKE EFFECT BANDS THIS
AFTERNOON TRYING TO WORK MORE WEST INTO EASTERN ILLINOIS. SOME
GUIDANCE DOES SUGGEST THAT THE LAKE EFFECT BANDS WILL EFFECT AREAS
NEAR...OR EVEN ALONG THE ILLINOIS...INDIANA STATE LINE....AND
POSSIBLY PARTS OF CHICAGO AS WELL. HOWEVER...GIVEN THE MODEL
DIFFERENCES...AND UNCERTAINTY STILL INHERENT IN WHERE ANY LAKE EFFECT
BAND...OR BANDS WILL SET UP...I WOULD LIKE TO WATCH THE EVOLUTION OF
CONDITIONS OVER THE LAKE BEFORE PUSHING SNOWFALL AMOUNTS...AND WINTER
HEADLINES FARTHER WEST.

NO BIG CHANGES ARE PLANNED FOR THE UPDATE. HOWEVER...I WILL LIKELY
ADD A MENTION OF LIGHT SNOW/FLURRIES FOR AREAS A BIT FARTHER INLAND
ACROSS NORTHEASTERN ILLINOIS BASED ON REPORTS OF LIGHT SNOW...AND
RADAR TRENDS.

KJB

&&

.SHORT TERM...
326 AM CDT

THROUGH SATURDAY...

ACTIVE WEATHER ON TAP THE NEXT 24 HOURS AS COMPACT AND DEEP UPPER
LOW DIVES SOUTH ACROSS THE REGION DRAGGING UNSEASONABLY COLD
AIR...BOTH AT THE SURFACE AND ALOFT...INTO THE REGION TODAY INTO
TONIGHT. EARLY THIS MORNING SURFACE ANALYSIS SHOWS A RATHER DIFFUSE
COLD FRONT MOVING ACROSS THE REGION WITH STRONG COLD ADVECTION
RESULTING IN A HEALTHY TEMP DROP PRIOR TO SUNRISE OVER NORTHERN CWA
AND SHORTLY AFTERWARD SOUTHEAST. STRONG NNW WINDS WILL ALSO ARRIVE
WITH THE COLD AIR AND CONTINUE INTO THIS EVENING RESULTING IN
TEMPERATURES LARGELY REMAINING FAIRLY STEADY THROUGH THE AFTERNOON.

COMPACT VORT AND REALLY THE HEART OF THE UPPER LOW SHOWS UP NICELY
OVER NORTHERN WISCONSIN EARLY THIS MORNING AND IS DIVING SSE TOWARD
THE AREA. THE COMBINATION OF ASCENT WITH THIS FEATURE AND STEEP
LAPSE RATES ARE RESULTING IN SCATTERED BUT FAIRLY VIGOROUS SNOW
SHOWERS OVER NORTHERN AND CENTRAL WISCONSIN AND WOULD FULLY
ANTICIPATE THESE TO MAINTAIN THEMSELVES AND MOVE ACROSS MAINLY THE
EASTERN CWA THIS MORNING. TEMPS WILL PROBABLY BE TOO WARM FOR MUCH
IF ANY ACCUMULATION...BUT SOME OF THE SNOW SHOWERS COULD BE BRIEFLY
VIGOROUS AND KNOCK VSBY DOWN TO BELOW 1SM. AS THE VORT CONTINUE
SOUTHEAST LOOK FOR THE NON-LAKE DRIVEN PRECIP TO END BY MID MORNING
NORTHERN CWA AND LATE MORNING SOUTHEAST CWA.

THE VORT WILL HERALD THE ARRIVAL OF THE COLDEST AIR ALOFT AND
RESULTANT STRONGEST INSTABILITY OVER THE LAKE AS H5 TEMPS DROP TO
-33C AND H7 TEMPS BELOW -15C. THERMODYNAMIC PROFILES OVER THE LAKE
BEHIND THIS VORT BECOME EXPLOSIVELY UNSTABLE THIS MORNING REMAIN SO
THROUGH THE DAY. LAKE EFFECT SHOULD GET GOING IN ERNEST BEHIND THIS
VORT AND CONTINUE TO SOME DEGREE INTO SATURDAY MORNING. FORECAST
LAKE INDUCED EQUILIBRIUM LEVELS TODAY APPROACH 20K FT...NEAR THE
-30C LEVEL...WHICH IS MORE THAN COLD ENOUGH TO SUPPORT LIGHTNING
GIVEN THE HIGH LIKELIHOOD OF MIXED PHASE HYDROMETEORS (SUPERCOOLED
DROPLETS AND ICE) IN THE CLOUDS WITHIN STRONG UPDRAFTS. NEAR SURFACE
TEMPS OVER THE LAKE AND WITHIN A FEW MILES OF THE LAKE SHORE MAY BE
WARM ENOUGH TO SUPPORT P-TYPE FLUCTUATING BETWEEN RAIN...RAIN/SNOW
MIX...AND ALL SNOW. LAKE EFFECT PRECIP FARTHER INLAND STANDS A MUCH
BETTER CHANCE OF REMAINING ALL OR MOSTLY SNOW.

ONE OF THE BIGGER UNCERTAINTIES FOR TODAY IS HOW ORGANIZED THE LAKE
EFFECT WILL BECOME AND WHETHER IT WILL BE MULTIPLE BANDS OR A SINGLE
INTENSE BAND. GIVEN THE VERY STRONG BOUNDARY LAYER WINDS AND LESS
THAN IDEAL TIME OF DAY AM CONCERNED THAT THE LAKE EFFECT PRECIP
COULD BE SOMEWHAT UNORGANIZED/SCATTERED IN NATURE WITH MULTIPLE
BANDS DURING THE DAY WHICH WILL BE THE TIME OF STRONG TO EXTREME
INSTABILITY. IF A MORE ORGANIZED DOMINANT SINGLE BAND DOES
FORM...THE STRONG FLOW AND INSTABILITY WELL INLAND WOULD SUPPORT
INTENSE PRECIP RATES MAKING IT WELL INLAND THIS AFTERNOON WHERE
P-TYPE WOULD LIKELY BE MOSTLY SNOW...POSSIBLY MODERATE TO HEAVY
SNOW. IF SNOW FALLS HEAVY ENOUGH THEN THE WARM GROUND TEMPS WOULD
BECOME MORE OF A MOOT POINT WITH RAPID ACCUMULATIONS OF HEAVY/WET
SNOW...ESPECIALLY ON GRASSY SURFACES WHERE ISOLATED LOCATIONS COULD
SEE A QUICK SEVERAL INCHES OF SNOW. THE MOST LIKELY SCENARIO WOULD
APPEAR TO BE SOMEWHAT LESS ORGANIZED BANDS OF SNOW SHOWERS RESULTING
IN ONLY MINOR ACCUMS ON GRASSY SURFACES IN SPOTS TODAY. THE WIND
WILL BE WHIPPING THE SNOW AROUND REGARDLESS SO UNDERNEATH ANY LAKE
EFFECT SNOW CONDITIONS WILL BE PRETTY MISERABLE EVEN THOUGH IT IS
UNLIKELY TO ACCUMULATE ON ROADS/SIDEWALKS TODAY. LAKE AND PORTER
COUNTY LOOK TO BE GROUND ZERO FOR THE LAKE EFFECT TODAY WITH THE
PRECIP LIKELY MAKING IT WELL INLAND TO JASPER AND NEWTON COUNTIES.
SOME HIGH RES GUIDANCE DOES CLIP SE COOK AND EASTERN WILL WITH LAKE
EFFECT PRECIP TODAY WHICH ISNT OUT OF THE QUESTION AND HAVE
MAINTAINED LOW POPS THERE.

THIS EVENING THE LOW LEVEL FLOW WILL GRADUALLY VEER AND SEND THE
LAKE EFFECT MORE INTO EASTERN COOK/EASTERN WILL/WESTERN LAKE IN (AND
EVEN POINTS SOUTH. BY THIS EVENING THE BOUNDARY LAYER FLOW WILL BE
WEAKENING AND THE TEMPS OUTSIDE OF THE LAKE INFLUENCED AREAS
DROPPING WHICH WOULD BOTH TEND TO FAVOR A TRANSITION TO A MORE
ORGANIZED DOMINANT SINGLE LAKE EFFECT BAND. MY BEST GUESS IS THAT
THE TIME WINDOW FOR THE HIGHEST PROBABILITY OF A DOMINANT LAKE
EFFECT BAND WITH POTENTIAL FOR HEAVY SNOW IS BETWEEN 23Z AND ABOUT
04Z. DURING THIS TIME PERIOD THE INSTABILITY (WHILE LESS THAN
EARLIER IN THE DAY) WILL STILL BE STRONG WITH INVERSION HEIGHTS
AROUND 10K FT AND LAKE-850 DELTA T VALUES >20C. DOES APPEARS A
PERIOD OF HEAVY SNOW COULD OCCUR IN EASTERN/SOUTHEASTERN COOK AND
EASTERN WILL COUNTIES EARLY THIS EVENING...BUT GIVEN THE LOW
CONFIDENCE OPTED NOT TO EXPAND THE WINTER WX HEADLINES AT THIS TIME
AND INSTEAD WILL ALLOW DAY SHIFT TO MONITOR MESOSCALE TRENDS. BY
LATER THIS EVENING INTO THE OVERNIGHT HOURS THE LAKE EFFECT
PARAMETERS WILL CONTINUE TO BECOME LESS FAVORABLE AND THE INTENSITY
OF THE LAKE EFFECT PRECIP SHOULD BEGIN TO WIND DOWN LATE TONIGHT AND
EVENTUALLY END SATURDAY. HAVE EXTENDED THE HIGHER POPS LATER IN TIME
AS LAKE EFFECT RARELY WINDS DOWN AS QUICKLY AS MODEL PROGGED
PARAMETERS SUGGEST IT WILL. WORTH NOTING THAT BY LATE EVENING AND
THROUGH SAT MORNING THE CONVECTIVE CLOUD TOP TEMPS DROP BELOW -12C
MEANING THE LIKELIHOOD OF CLOUDS CONTAINING ICE NUCLEI FOR SNOW WILL
BE LOW...SO DESPITE LOWER TEMPS IN THE BOUNDARY LAYER HAVE
TRANSITIONED P-TYPE BACK TO RAIN OR SNOW LATE TONIGHT AND SAT
MORNING.

FINALLY...HIGH WINDS WILL BE THE OTHER CONCERN TODAY. PLAN TO
MAINTAIN WIND ADVISORY AS IS THOUGH CONFIDENCE IN INLAND LOCATIONS
REACHING ADVISORY CRITERIA IS NOT THAT HIGH...BUT WITH GUSTS TO AT
LEAST 40 MPH A GOOD BET NOTHING WOULD BE GAINED FROM MAKING ANY
CHANGES TO THE HEADLINES. THE STORM WARNING FOR THE LAKE LOOKS
LIKELY TO VERIFY WITH 40 MPH SUSTAINED AND POSSIBLY GUSTS TO 58 MPH
LIKELY ALONG THE LAKE FRONT TODAY AND REALLY NOT COMFORTABLE NOT
HAVING A WARNING WITH THE POTENTIAL FOR DAMAGING WINDS ALONG THE
LAKE...SO AM GOING TO UPGRADE TO A HIGH WIND WARNING FOR LAKE SHORE
AREAS.

HEADLINES ARE AN ABSOLUTE MESS AND HEADACHE. WINTER WX ADVISORY
COVERS WIND AND SNOW...BUT IN ORDER TO GO WITH WARNING FOR WIND
ALONG THE LAKE FRONT IN INDIANA WOULD NEED TO UPGRADE TO A WINTER
STORM WARNING WHICH REALLY DOESNT SEEM TO BE THE BEST PRODUCT. AFTER
MUCH HEMMING AND HAWING AND INTERNAL COORDINATION HAVE OPTED TO
CHANGE THE WINTER WX ADV TO A LAKE EFFECT SNOW ADVISORY AND ISSUE A
WIND ADVISORY FOR JASPER AND NEWTON AND A HIGH WIND WARNING FOR LAKE
SHORE AREAS OF COOK...PORTER...AND LAKE IN. MAY NEED TO REPLACE THE
HIGH WIND WARNING WITH A WIND ADVISORY BY EARLY EVENING FOR

IZZI

&&

.LONG TERM...
325 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

MUCH...MUCH QUIETER SUNDAY AND MONDAY WITH MODERATING TEMPS. SLOW
MOVING FRONT COULD BRING A SOMEWHAT PROLONGED PERIOD OF RAIN/SHOWERS
MONDAY NIGHT THOUGH TUESDAY NIGHT. GENERALLY SEASONABLE TEMPS
EXPECTED THROUGH THE EXTENDED.

IZZI

&&

.AVIATION...

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

* VERY GUSTY NORTH-NORTHWEST WINDS GRADUALLY SHIFTING TO DUE NORTH
  BY MID-AFTERNOON. SPORADIC GUSTS IN EXCESS OF 40 KT THROUGH 22Z.

* PERIODS OF FLURRIES THIS AFTERNOON WITH THE POTENTIAL FOR SOME
  TEMPORARY SNOW SHOWERS NAMELY AT MDW.

* LAKE EFFECT SNOW SHOWERS PROBABLE OVER MDW LATER THIS EVE
  THROUGH EARLY SATURDAY MORNING AND ORD OVERNIGHT INTO EARLY
  SATURDAY MORNING.

* CIGS DROPPING TO 1500-3000 FT LATER THIS EVENING THROUGH EARLY
  SATURDAY MORNING.


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

VERY GUSTY NORTH-NORTHWEST WINDS WILL CONTINUE THROUGH THIS
AFTERNOON AS COLD AIR CONTINUES TO REPLENISH ITSELF. GUSTS OF 33
TO 40 KT...WITH EVEN SPORADICALLY HIGHER ARE HIGHLY LIKELY TO BE
COMMON THROUGH THE AFTERNOON. DURING THE AFTERNOON...DUE TO THE
ORIENTATION OF THE PRESSURE GRADIENT...THE WIND DIRECTION IS
EXPECTED TO SHIFT TO 360 DEGREES AT CHICAGOLAND TAF SITES. LAKE
EFFECT SNOW...MAYBE AT TIMES RAIN...WILL CONTINUE TO IMPACT GARY
THROUGHOUT THIS AFTERNOON AND TONIGHT. WITH SOME BANDING
POTENTIAL THIS EVE VISIBILITY COULD DROP QUITE LOW DURING THAT
PERIOD. THE SNOW BAND...OR AREA OF SHOWERS...WILL BEGIN TO INCH
BACK WESTWARD THIS EVE INTO OVERNIGHT. THE INTENSITY OF SNOW COULD
STILL BE FAIRLY IMPRESSIVE AT MDW LATER THIS EVE...ALTHOUGH A
DECENT AMOUNT OF UNCERTAINTY EXISTS THERE. AT LEAST LAKE-INDUCED
CLOUDS ARE LIKELY OVER NORTHEAST ILLINOIS SATURDAY MORNING
ALTHOUGH THERE COULD CONTINUE SOME SNOW SHOWERS TOO. AT THE SAME
TIME WINDS ARE FAVORED TO BE BETWEEN 360-020 DEGREES...SO IMPACTS
TO ORD OPERATIONS COULD CONTINUE THROUGH SATURDAY MORNING.


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

* HIGH IN WIND SPEEDS AND HIGH THAT DIRECTION WILL SHIFT TO 360
  DEGREES THIS AFTERNOON. MEDIUM NORTH-NORTHEAST ON SATURDAY
  MORNING.

* HIGH THAT ANY REDUCTION IN VISIBILITY IN SNOW PRIOR TO 02Z WOULD
  BE VERY BRIEF.

* MEDIUM IN SNOW SHOWERS IMPACTING MDW LATER TONIGHT AND LOW FOR
  ORD. LOW IN HOW LOW VISIBILITY WILL DROP AT EITHER AIRPORT.

* MEDIUM IN CIGS THROUGH TAF.


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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MTF

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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000
FXUS63 KLOT 311628
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1128 AM CDT FRI OCT 31 2014

.MESOSCALE DISCUSSION...

WE ARE CURRENTLY WATCHING THE PROGRESS OF A SECONDARY INVERTED
SURFACE TROUGH...WHICH IS CURRENTLY RACING SOUTHWARD DOWN CENTRAL
LAKE MICHIGAN. OBSERVATIONS OVER AND NEAR THE LAKE INDICATE THE
PRESENCE OF GOOD CONVERGENCE ALONG THIS BOUNDARY. THE FIRST
MORNING VISIBLE SATELLITE IMAGES ALSO INDICATE CONVECTIVE
STRUCTURES DEVELOPING WITHIN THE BAND OF RAIN/SNOW SHOWERS
CURRENTLY SHIFTING SOUTHWARD JUST EAST OF MKE. OVERALL IT APPEARS
THIS AREA OF SNOWFALL WILL PIVOT SOUTHWARD ACROSS NORTHWESTERN
INDIANA WITHIN THE NEXT 2 HOURS (BY 1630Z). HOWEVER...I AM ALSO
CONCERNED THAT SOME OF THESE HEAVIER CONVECTIVE SNOW SHOWERS MAY
IMPACT PORTIONS OF NORTHEASTERN ILLINOIS...INCLUDING DOWNTOWN
CHICAGO THROUGH LATE MORNING. IN FACT...SOME OF THE LATEST RADAR
IMAGERY IS ALREADY INDICATING SOME BANDS OF PRECIP MOVING INTO
NORTHERN COOK COUNTY. IT APPEARS THE WINDS WILL BECOME MORE
NORTHERLY IN THE WAKE OF THIS SURFACE TROUGH...AND WIND SPEEDS
COULD ALSO INCREASE A BIT HIGHER THAN CURRENT WIND SPEEDS. WE WILL
CONTINUE TO WATCH OBSERVATION TRENDS...AND HANDLE THIS SNOWFALL
ACROSS THE CHICAGO AREA WITH GRAPHICAL NOWCASTS AT THIS TIME. IT
DOES APPEAR THIS INITIAL BURST OF SNOW WILL BE SOMEWHAT SHORT
LIVED ACROSS THE CHICAGO METRO AREA. WHILE SOME MINOR
ACCUMULATIONS ARE CERTAINLY POSSIBLE WITH THIS ACTIVITY...WE HAVE
NO IMMEDIATE PLANS TO EXPAND THE CURRENT WINTER WEATHER HEADLINES.

FOLLOWING THIS INITIAL BOUNDARY AND BURST OF SNOW...HI RES GUIDANCE
CONTINUES TO INDICATE THAT BANDS OF LAKE EFFECT RAIN/SNOW SHOWERS
WILL CONTINUE TO DEVELOP AND IMPACT MUCH OF THE AREAS CURRENTLY
UNDER THE WINTER HEADLINE ACROSS NORTHWESTERN INDIANA. HOWEVER...WE
WILL NEED TO WATCH FOR THE POTENTIAL OF THE LAKE EFFECT BANDS THIS
AFTERNOON TRYING TO WORK MORE WEST INTO EASTERN ILLINOIS. SOME
GUIDANCE DOES SUGGEST THAT THE LAKE EFFECT BANDS WILL EFFECT AREAS
NEAR...OR EVEN ALONG THE ILLINOIS...INDIANA STATE LINE....AND
POSSIBLY PARTS OF CHICAGO AS WELL. HOWEVER...GIVEN THE MODEL
DIFFERENCES...AND UNCERTAINTY STILL INHERENT IN WHERE ANY LAKE EFFECT
BAND...OR BANDS WILL SET UP...I WOULD LIKE TO WATCH THE EVOLUTION OF
CONDITIONS OVER THE LAKE BEFORE PUSHING SNOWFALL AMOUNTS...AND WINTER
HEADLINES FARTHER WEST.

NO BIG CHANGES ARE PLANNED FOR THE UPDATE. HOWEVER...I WILL LIKELY
ADD A MENTION OF LIGHT SNOW/FLURRIES FOR AREAS A BIT FARTHER INLAND
ACROSS NORTHEASTERN ILLINOIS BASED ON REPORTS OF LIGHT SNOW...AND
RADAR TRENDS.

KJB

&&

PREVIOUS DISCUSSION...

.SHORT TERM...
326 AM CDT

THROUGH SATURDAY...

ACTIVE WEATHER ON TAP THE NEXT 24 HOURS AS COMPACT AND DEEP UPPER
LOW DIVES SOUTH ACROSS THE REGION DRAGGING UNSEASONABLY COLD
AIR...BOTH AT THE SURFACE AND ALOFT...INTO THE REGION TODAY INTO
TONIGHT. EARLY THIS MORNING SURFACE ANALYSIS SHOWS A RATHER DIFFUSE
COLD FRONT MOVING ACROSS THE REGION WITH STRONG COLD ADVECTION
RESULTING IN A HEALTHY TEMP DROP PRIOR TO SUNRISE OVER NORTHERN CWA
AND SHORTLY AFTERWARD SOUTHEAST. STRONG NNW WINDS WILL ALSO ARRIVE
WITH THE COLD AIR AND CONTINUE INTO THIS EVENING RESULTING IN
TEMPERATURES LARGELY REMAINING FAIRLY STEADY THROUGH THE AFTERNOON.

COMPACT VORT AND REALLY THE HEART OF THE UPPER LOW SHOWS UP NICELY
OVER NORTHERN WISCONSIN EARLY THIS MORNING AND IS DIVING SSE TOWARD
THE AREA. THE COMBINATION OF ASCENT WITH THIS FEATURE AND STEEP
LAPSE RATES ARE RESULTING IN SCATTERED BUT FAIRLY VIGOROUS SNOW
SHOWERS OVER NORTHERN AND CENTRAL WISCONSIN AND WOULD FULLY
ANTICIPATE THESE TO MAINTAIN THEMSELVES AND MOVE ACROSS MAINLY THE
EASTERN CWA THIS MORNING. TEMPS WILL PROBABLY BE TOO WARM FOR MUCH
IF ANY ACCUMULATION...BUT SOME OF THE SNOW SHOWERS COULD BE BRIEFLY
VIGOROUS AND KNOCK VSBY DOWN TO BELOW 1SM. AS THE VORT CONTINUE
SOUTHEAST LOOK FOR THE NON-LAKE DRIVEN PRECIP TO END BY MID MORNING
NORTHERN CWA AND LATE MORNING SOUTHEAST CWA.

THE VORT WILL HERALD THE ARRIVAL OF THE COLDEST AIR ALOFT AND
RESULTANT STRONGEST INSTABILITY OVER THE LAKE AS H5 TEMPS DROP TO
-33C AND H7 TEMPS BELOW -15C. THERMODYNAMIC PROFILES OVER THE LAKE
BEHIND THIS VORT BECOME EXPLOSIVELY UNSTABLE THIS MORNING REMAIN SO
THROUGH THE DAY. LAKE EFFECT SHOULD GET GOING IN ERNEST BEHIND THIS
VORT AND CONTINUE TO SOME DEGREE INTO SATURDAY MORNING. FORECAST
LAKE INDUCED EQUILIBRIUM LEVELS TODAY APPROACH 20K FT...NEAR THE
-30C LEVEL...WHICH IS MORE THAN COLD ENOUGH TO SUPPORT LIGHTNING
GIVEN THE HIGH LIKELIHOOD OF MIXED PHASE HYDROMETEORS (SUPERCOOLED
DROPLETS AND ICE) IN THE CLOUDS WITHIN STRONG UPDRAFTS. NEAR SURFACE
TEMPS OVER THE LAKE AND WITHIN A FEW MILES OF THE LAKE SHORE MAY BE
WARM ENOUGH TO SUPPORT P-TYPE FLUCTUATING BETWEEN RAIN...RAIN/SNOW
MIX...AND ALL SNOW. LAKE EFFECT PRECIP FARTHER INLAND STANDS A MUCH
BETTER CHANCE OF REMAINING ALL OR MOSTLY SNOW.

ONE OF THE BIGGER UNCERTAINTIES FOR TODAY IS HOW ORGANIZED THE LAKE
EFFECT WILL BECOME AND WHETHER IT WILL BE MULTIPLE BANDS OR A SINGLE
INTENSE BAND. GIVEN THE VERY STRONG BOUNDARY LAYER WINDS AND LESS
THAN IDEAL TIME OF DAY AM CONCERNED THAT THE LAKE EFFECT PRECIP
COULD BE SOMEWHAT UNORGANIZED/SCATTERED IN NATURE WITH MULTIPLE
BANDS DURING THE DAY WHICH WILL BE THE TIME OF STRONG TO EXTREME
INSTABILITY. IF A MORE ORGANIZED DOMINANT SINGLE BAND DOES
FORM...THE STRONG FLOW AND INSTABILITY WELL INLAND WOULD SUPPORT
INTENSE PRECIP RATES MAKING IT WELL INLAND THIS AFTERNOON WHERE
P-TYPE WOULD LIKELY BE MOSTLY SNOW...POSSIBLY MODERATE TO HEAVY
SNOW. IF SNOW FALLS HEAVY ENOUGH THEN THE WARM GROUND TEMPS WOULD
BECOME MORE OF A MOOT POINT WITH RAPID ACCUMULATIONS OF HEAVY/WET
SNOW...ESPECIALLY ON GRASSY SURFACES WHERE ISOLATED LOCATIONS COULD
SEE A QUICK SEVERAL INCHES OF SNOW. THE MOST LIKELY SCENARIO WOULD
APPEAR TO BE SOMEWHAT LESS ORGANIZED BANDS OF SNOW SHOWERS RESULTING
IN ONLY MINOR ACCUMS ON GRASSY SURFACES IN SPOTS TODAY. THE WIND
WILL BE WHIPPING THE SNOW AROUND REGARDLESS SO UNDERNEATH ANY LAKE
EFFECT SNOW CONDITIONS WILL BE PRETTY MISERABLE EVEN THOUGH IT IS
UNLIKELY TO ACCUMULATE ON ROADS/SIDEWALKS TODAY. LAKE AND PORTER
COUNTY LOOK TO BE GROUND ZERO FOR THE LAKE EFFECT TODAY WITH THE
PRECIP LIKELY MAKING IT WELL INLAND TO JASPER AND NEWTON COUNTIES.
SOME HIGH RES GUIDANCE DOES CLIP SE COOK AND EASTERN WILL WITH LAKE
EFFECT PRECIP TODAY WHICH ISNT OUT OF THE QUESTION AND HAVE
MAINTAINED LOW POPS THERE.

THIS EVENING THE LOW LEVEL FLOW WILL GRADUALLY VEER AND SEND THE
LAKE EFFECT MORE INTO EASTERN COOK/EASTERN WILL/WESTERN LAKE IN (AND
EVEN POINTS SOUTH. BY THIS EVENING THE BOUNDARY LAYER FLOW WILL BE
WEAKENING AND THE TEMPS OUTSIDE OF THE LAKE INFLUENCED AREAS
DROPPING WHICH WOULD BOTH TEND TO FAVOR A TRANSITION TO A MORE
ORGANIZED DOMINANT SINGLE LAKE EFFECT BAND. MY BEST GUESS IS THAT
THE TIME WINDOW FOR THE HIGHEST PROBABILITY OF A DOMINANT LAKE
EFFECT BAND WITH POTENTIAL FOR HEAVY SNOW IS BETWEEN 23Z AND ABOUT
04Z. DURING THIS TIME PERIOD THE INSTABILITY (WHILE LESS THAN
EARLIER IN THE DAY) WILL STILL BE STRONG WITH INVERSION HEIGHTS
AROUND 10K FT AND LAKE-850 DELTA T VALUES >20C. DOES APPEARS A
PERIOD OF HEAVY SNOW COULD OCCUR IN EASTERN/SOUTHEASTERN COOK AND
EASTERN WILL COUNTIES EARLY THIS EVENING...BUT GIVEN THE LOW
CONFIDENCE OPTED NOT TO EXPAND THE WINTER WX HEADLINES AT THIS TIME
AND INSTEAD WILL ALLOW DAY SHIFT TO MONITOR MESOSCALE TRENDS. BY
LATER THIS EVENING INTO THE OVERNIGHT HOURS THE LAKE EFFECT
PARAMETERS WILL CONTINUE TO BECOME LESS FAVORABLE AND THE INTENSITY
OF THE LAKE EFFECT PRECIP SHOULD BEGIN TO WIND DOWN LATE TONIGHT AND
EVENTUALLY END SATURDAY. HAVE EXTENDED THE HIGHER POPS LATER IN TIME
AS LAKE EFFECT RARELY WINDS DOWN AS QUICKLY AS MODEL PROGGED
PARAMETERS SUGGEST IT WILL. WORTH NOTING THAT BY LATE EVENING AND
THROUGH SAT MORNING THE CONVECTIVE CLOUD TOP TEMPS DROP BELOW -12C
MEANING THE LIKELIHOOD OF CLOUDS CONTAINING ICE NUCLEI FOR SNOW WILL
BE LOW...SO DESPITE LOWER TEMPS IN THE BOUNDARY LAYER HAVE
TRANSITIONED P-TYPE BACK TO RAIN OR SNOW LATE TONIGHT AND SAT
MORNING.

FINALLY...HIGH WINDS WILL BE THE OTHER CONCERN TODAY. PLAN TO
MAINTAIN WIND ADVISORY AS IS THOUGH CONFIDENCE IN INLAND LOCATIONS
REACHING ADVISORY CRITERIA IS NOT THAT HIGH...BUT WITH GUSTS TO AT
LEAST 40 MPH A GOOD BET NOTHING WOULD BE GAINED FROM MAKING ANY
CHANGES TO THE HEADLINES. THE STORM WARNING FOR THE LAKE LOOKS
LIKELY TO VERIFY WITH 40 MPH SUSTAINED AND POSSIBLY GUSTS TO 58 MPH
LIKELY ALONG THE LAKE FRONT TODAY AND REALLY NOT COMFORTABLE NOT
HAVING A WARNING WITH THE POTENTIAL FOR DAMAGING WINDS ALONG THE
LAKE...SO AM GOING TO UPGRADE TO A HIGH WIND WARNING FOR LAKE SHORE
AREAS.

HEADLINES ARE AN ABSOLUTE MESS AND HEADACHE. WINTER WX ADVISORY
COVERS WIND AND SNOW...BUT IN ORDER TO GO WITH WARNING FOR WIND
ALONG THE LAKE FRONT IN INDIANA WOULD NEED TO UPGRADE TO A WINTER
STORM WARNING WHICH REALLY DOESNT SEEM TO BE THE BEST PRODUCT. AFTER
MUCH HEMMING AND HAWING AND INTERNAL COORDINATION HAVE OPTED TO
CHANGE THE WINTER WX ADV TO A LAKE EFFECT SNOW ADVISORY AND ISSUE A
WIND ADVISORY FOR JASPER AND NEWTON AND A HIGH WIND WARNING FOR LAKE
SHORE AREAS OF COOK...PORTER...AND LAKE IN. MAY NEED TO REPLACE THE
HIGH WIND WARNING WITH A WIND ADVISORY BY EARLY EVENING FOR

IZZI

&&

.AVIATION...

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

* PERIODS OF FLURRIES THIS AFTERNOON WITH THE POTENTIAL FOR SOME
  TEMPORARY SNOW SHOWERS NAMELY AT MDW.

* VERY GUSTY NORTHWEST WINDS PROBABLE TO SHIFT DUE NORTH EARLY
  THIS AFTERNOON. SPORADIC GUSTS IN EXCESS OF 40 KT.

* CIGS POTENTIALLY DROPPING TO 2000-3000 FT AGAIN THIS AFTERNOON.

* LAKE EFFECT SNOW SHOWERS COULD FURTHER AFFECT MDW THIS EVE.

MTF/MDB

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

NORTH-NORTHWEST WINDS HAVE BEEN VERY STEADY AT 340-350 AT ORD AND
MDW. A SECONDARY COLD FRONT/TROUGH IS MOVING SOUTHWARD DOWN LAKE
MICHIGAN AND WISCONSIN AND THIS WILL TURN WINDS MORE DUE NORTH.
THIS IS SLIGHTLY LATER FOR DUE NORTH THAN PREVIOUS TAF. WIND SPEED
THINKING REMAINS THE SAME.

CONVECTIVE CLOUD TOPS ARE BEGINNING TO SHOW UP ACROSS THE CENTRAL
AND SOUTHERN PART OF THE LAKE SO IT IS POSSIBLE WE BEGIN TO SEE
SOME LIGHTNING AS WELL.

PREV DISCUSSION...UPDATED 12Z...

NORTHWEST WINDS HAVE BEEN STEADILY INCREASING EARLY THIS MORNING
AS STRONG HIGH PRESSURE APPROACHES FROM THE NORTHWEST. ONE UPPER
WAVE AND ASSOCIATED -SHRA IS DEPARTING WHILE ANOTHER IS APPROACHING
FROM THE NORTH. A PUSH OF COLDER AIR WITH THE NEXT WAVE IS
RESULTING IN A BAND OF SNOW SHOWERS WHICH HAS BEEN REDUCING VSBY
TO AROUND A MILE AT TIMES...AT LEAST BRIEFLY. EXPECT A 1-2 HR
WINDOW OF -SHSN AT THE TERMINALS OVER THE NEXT 2-3 HRS. VARIABLE
MVFR-VFR CIGS WILL CONTINUE THROUGH MUCH OF THE MORNING BEFORE
STEADIER VFR IS EXPECTED ACROSS THE ILLINOIS TERMINALS WITH
SCATTERING OF CLOUDS WEST.

WINDS WILL TURN TO THE NORTH WITH THE PASSAGE OF THE UPPER WAVE
THIS MORNING AND EXPECT TO SEE A SURGE IN GUSTS AT THAT TIME. 35
TO 40 KT GUSTS ARE EXPECTED BUT AM NOT HIGHLY CONFIDENT IN HOW
FREQUENTLY 40 KT MAY BE REACHED. IT APPEARS THAT MID MORNING MAY
BE ONE POTENTIALLY PRIME PERIOD BEHIND THE UPPER WAVE/PRECIP WITH
THE NEXT POTENTIALLY FAVORED TIME BEING MID AFTERNOON IF SKIES CAN
SCATTER. IT MAY BE THAT AN OCCASIONAL 40 KT GUST OCCURS AT ANY
POINT THROUGH THE DAY. WINDS WILL EASE THIS EVENING.

LAKE EFFECT PRECIPITATION IS EXPECTED TO DEVELOP MID TO LATE
MORNING AND FOCUS ACROSS NORTHWEST INDIANA WITH GYY POSSIBLY BEING
ON THE WESTERN FRINGE INITIALLY BUT LIKELY GETTING INTO THE PRIME
BANDING INTO THE AFTERNOON. GIVEN THEIR PROXIMITY TO THE FAIRLY
WARM LAKE A RAIN SNOW MIX IS FAVORED TURNING TO ALL SNOW IF VERY
INTENSE BANDING CAN OCCUR. THUNDER IS ALSO POSSIBLE AND WOULD
ENHANCE THE ALL SNOW POTENTIAL. AS A RESULT IFR VSBY WILL LIKELY
OCCUR AT TIMES BUT THERE ARE FACTORS THAT MAY LIMIT THE
ORGANIZATION OF THE PRECIP. WINDS WILL LIKELY GUST 40-45 KT WITH
50 NOT OUT OF THE QUESTION TOWARD MIDDAY. LAKE EFFECT PRECIP WILL
LIKELY TURN TO ALL SNOW THIS EVENING AND SHIFT WESTWARD TOWARD THE
IL/IN STATE LINE AND POSSIBLY BEGIN TO IMPACT MDW WITH LIGHT
ACCUMULATIONS POSSIBLE...MAINLY ON THE GRASS. SEVERAL HOURS OF
SNOW MAY OCCUR AT OR NEAR MDW. ADJUSTMENTS TO THE FORECAST DETAILS
THIS EVENING AT MDW/GYY AND EVEN ORD ARE LIKELY.

MDB

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

* LOW ON IF IFR SNOW SHOWERS MAY IMPACT MDW THIS AFTERNOON.
  MEDIUM THAT THEY WILL STAY EAST OF ORD.

* HIGH IN NORTHWEST WINDS TURNING DUE NORTH BUT LOW IN EXACT
  TIMING. HIGH IN WIND SPEEDS AND THAT GUSTS WILL EXCEED 35 KT
  MUCH OF THIS AFTERNOON.

* HIGH THAT CIGS WILL REMAIN ABOVE 2000 FT.

* MEDIUM IN LAKE EFFECT SNOW SHOWER POTENTIAL TONIGHT AT MDW...LOW
  AT ORD.

MTF/MDB

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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MDB

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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
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000
FXUS63 KLOT 311505
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1005 AM CDT FRI OCT 31 2014

.MESOSCALE DISCUSSION...
1001 AM CDT

WE ARE CURRENTLY WATCHING THE PROGRESS OF A SECONDARY INVERTED
SURFACE TROUGH...WHICH IS CURRENTLY RACING SOUTHWARD DOWN CENTRAL
LAKE MICHIGAN. OBSERVATIONS OVER AND NEAR THE LAKE INDICATE THE
PRESENCE OF GOOD CONVERGENCE ALONG THIS BOUNDARY. THE FIRST
MORNING VISIBLE SATELLITE IMAGES ALSO INDICATE CONVECTIVE
STRUCTURES DEVELOPING WITHIN THE BAND OF RAIN/SNOW SHOWERS
CURRENTLY SHIFTING SOUTHWARD JUST EAST OF MKE. OVERALL IT APPEARS
THIS AREA OF SNOWFALL WILL PIVOT SOUTHWARD ACROSS NORTHWESTERN
INDIANA WITHIN THE NEXT 2 HOURS (BY 1630Z). HOWEVER...I AM ALSO
CONCERNED THAT SOME OF THESE HEAVIER CONVECTIVE SNOW SHOWERS MAY
IMPACT PORTIONS OF NORTHEASTERN ILLINOIS...INCLUDING DOWNTOWN
CHICAGO THROUGH LATE MORNING. IN FACT...SOME OF THE LATEST RADAR
IMAGERY IS ALREADY INDICATING SOME BANDS OF PRECIP MOVING INTO
NORTHERN COOK COUNTY. IT APPEARS THE WINDS WILL BECOME MORE
NORTHERLY IN THE WAKE OF THIS SURFACE TROUGH...AND WIND SPEEDS
COULD ALSO INCREASE A BIT HIGHER THAN CURRENT WIND SPEEDS. WE WILL
CONTINUE TO WATCH OBSERVATION TRENDS...AND HANDLE THIS SNOWFALL
ACROSS THE CHICAGO AREA WITH GRAPHICAL NOWCASTS AT THIS TIME. IT
DOES APPEAR THIS INITIAL BURST OF SNOW WILL BE SOMEWHAT SHORT
LIVED ACROSS THE CHICAGO METRO AREA. WHILE SOME MINOR
ACCUMULATIONS ARE CERTAINLY POSSIBLE WITH THIS ACTIVITY...WE HAVE
NO IMMEDIATE PLANS TO EXPAND THE CURRENT WINTER WEATHER HEADLINES.

FOLLOWING THIS INITIAL BOUNDARY AND BURST OF SNOW...HI RES GUIDANCE
CONTINUES TO INDICATE THAT BANDS OF LAKE EFFECT RAIN/SNOW SHOWERS
WILL CONTINUE TO DEVELOP AND IMPACT MUCH OF THE AREAS CURRENTLY
UNDER THE WINTER HEADLINE ACROSS NORTHWESTERN INDIANA. HOWEVER...WE
WILL NEED TO WATCH FOR THE POTENTIAL OF THE LAKE EFFECT BANDS THIS
AFTERNOON TRYING TO WORK MORE WEST INTO EASTERN ILLINOIS. SOME
GUIDANCE DOES SUGGEST THAT THE LAKE EFFECT BANDS WILL EFFECT AREAS
NEAR...OR EVEN ALONG THE ILLINOIS...INDIANA STATE LINE....AND
POSSIBLY PARTS OF CHICAGO AS WELL. HOWEVER...GIVEN THE MODEL
DIFFERENCES...AND UNCERTAINTY STILL INHERENT IN WHERE ANY LAKE EFFECT
BAND...OR BANDS WILL SET UP...I WOULD LIKE TO WATCH THE EVOLUTION OF
CONDITIONS OVER THE LAKE BEFORE PUSHING SNOWFALL AMOUNTS...AND WINTER
HEADLINES FARTHER WEST.

NO BIG CHANGES ARE PLANNED FOR THE UPDATE. HOWEVER...I WILL LIKELY
ADD A MENTION OF LIGHT SNOW/FLURRIES FOR AREAS A BIT FARTHER INLAND
ACROSS NORTHEASTERN ILLINOIS BASED ON REPORTS OF LIGHT SNOW...AND
RADAR TRENDS.

KJB

&&

.AVIATION...

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

* OFF AND ON FLURRIES LATE THIS MORNING AND AFTERNOON WITH THE
  POSSIBILITY OF SOME TEMPORARY SNOW SHOWERS NAMELY AT MDW.

* NORTHWEST WINDS SHIFTING NORTH TOWARD 16Z-17Z WITH GUSTS OF 35
  TO 40 KT. GUST SPEEDS WILL BE ERRATIC AND 40 KT GUSTS SHOULD BE
  SPORADIC.

* PERIODIC MVFR CIGS THROUGH THE MORNING AND POSSIBLY INTO THE
  AFTERNOON...ALTHOUGH SHOULD REMAIN ABOVE 2000 FT.

* LAKE EFFECT SNOW SHOWERS COULD AFFECT MDW FROM EARLY EVENING
  ONWARD.

MTF/MDB

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

NORTH-NORTHWEST WINDS HAVE BEEN VERY STEADY AT 340-350 AT ORD AND
MDW. A SECONDARY COLD FRONT/TROUGH IS MOVING SOUTHWARD DOWN LAKE
MICHIGAN AND WISCONSIN AND THIS WILL TURN WINDS MORE DUE NORTH.
THIS IS SLIGHTLY LATER FOR DUE NORTH THAN PREVIOUS TAF. WIND SPEED
THINKING REMAINS THE SAME.

CONVECTIVE CLOUD TOPS ARE BEGINNING TO SHOW UP ACROSS THE CENTRAL
AND SOUTHERN PART OF THE LAKE SO IT IS POSSIBLE WE BEGIN TO SEE
SOME LIGHTNING AS WELL.

PREV DISCUSSION...UPDATED 12Z...

NORTHWEST WINDS HAVE BEEN STEADILY INCREASING EARLY THIS MORNING
AS STRONG HIGH PRESSURE APPROACHES FROM THE NORTHWEST. ONE UPPER
WAVE AND ASSOCIATED -SHRA IS DEPARTING WHILE ANOTHER IS APPROACHING
FROM THE NORTH. A PUSH OF COLDER AIR WITH THE NEXT WAVE IS
RESULTING IN A BAND OF SNOW SHOWERS WHICH HAS BEEN REDUCING VSBY
TO AROUND A MILE AT TIMES...AT LEAST BRIEFLY. EXPECT A 1-2 HR
WINDOW OF -SHSN AT THE TERMINALS OVER THE NEXT 2-3 HRS. VARIABLE
MVFR-VFR CIGS WILL CONTINUE THROUGH MUCH OF THE MORNING BEFORE
STEADIER VFR IS EXPECTED ACROSS THE ILLINOIS TERMINALS WITH
SCATTERING OF CLOUDS WEST.

WINDS WILL TURN TO THE NORTH WITH THE PASSAGE OF THE UPPER WAVE
THIS MORNING AND EXPECT TO SEE A SURGE IN GUSTS AT THAT TIME. 35
TO 40 KT GUSTS ARE EXPECTED BUT AM NOT HIGHLY CONFIDENT IN HOW
FREQUENTLY 40 KT MAY BE REACHED. IT APPEARS THAT MID MORNING MAY
BE ONE POTENTIALLY PRIME PERIOD BEHIND THE UPPER WAVE/PRECIP WITH
THE NEXT POTENTIALLY FAVORED TIME BEING MID AFTERNOON IF SKIES CAN
SCATTER. IT MAY BE THAT AN OCCASIONAL 40 KT GUST OCCURS AT ANY
POINT THROUGH THE DAY. WINDS WILL EASE THIS EVENING.

LAKE EFFECT PRECIPITATION IS EXPECTED TO DEVELOP MID TO LATE
MORNING AND FOCUS ACROSS NORTHWEST INDIANA WITH GYY POSSIBLY BEING
ON THE WESTERN FRINGE INITIALLY BUT LIKELY GETTING INTO THE PRIME
BANDING INTO THE AFTERNOON. GIVEN THEIR PROXIMITY TO THE FAIRLY
WARM LAKE A RAIN SNOW MIX IS FAVORED TURNING TO ALL SNOW IF VERY
INTENSE BANDING CAN OCCUR. THUNDER IS ALSO POSSIBLE AND WOULD
ENHANCE THE ALL SNOW POTENTIAL. AS A RESULT IFR VSBY WILL LIKELY
OCCUR AT TIMES BUT THERE ARE FACTORS THAT MAY LIMIT THE
ORGANIZATION OF THE PRECIP. WINDS WILL LIKELY GUST 40-45 KT WITH
50 NOT OUT OF THE QUESTION TOWARD MIDDAY. LAKE EFFECT PRECIP WILL
LIKELY TURN TO ALL SNOW THIS EVENING AND SHIFT WESTWARD TOWARD THE
IL/IN STATE LINE AND POSSIBLY BEGIN TO IMPACT MDW WITH LIGHT
ACCUMULATIONS POSSIBLE...MAINLY ON THE GRASS. SEVERAL HOURS OF
SNOW MAY OCCUR AT OR NEAR MDW. ADJUSTMENTS TO THE FORECAST DETAILS
THIS EVENING AT MDW/GYY AND EVEN ORD ARE LIKELY.

MDB

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

* LOW ON IF IFR SNOW SHOWERS MAY IMPACT MDW THIS AFTERNOON.
  MEDIUM THAT THEY WILL STAY EAST OF ORD.

* HIGH IN NORTHWEST WINDS TURNING DUE NORTH AND MEDIUM IN TIMING.
  HIGH IN WIND SPEEDS AND THAT ANY GUSTS TO 40 KT WILL BE
  TEMPORARY.

* MEDIUM IN MVFR CIGS. HIGH THAT THEY WILL REMAIN ABOVE 2000 FT
  AT ORD...MEDIUM AT MDW.

* MEDIUM IN LAKE EFFECT SNOW SHOWER POTENTIAL TONIGHT AT MDW...LOW
  AT ORD.

MTF/MDB

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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MDB

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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
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000
FXUS63 KLOT 311422
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
922 AM CDT FRI OCT 31 2014

.SHORT TERM...
326 AM CDT

THROUGH SATURDAY...

ACTIVE WEATHER ON TAP THE NEXT 24 HOURS AS COMPACT AND DEEP UPPER
LOW DIVES SOUTH ACROSS THE REGION DRAGGING UNSEASONABLY COLD
AIR...BOTH AT THE SURFACE AND ALOFT...INTO THE REGION TODAY INTO
TONIGHT. EARLY THIS MORNING SURFACE ANALYSIS SHOWS A RATHER DIFFUSE
COLD FRONT MOVING ACROSS THE REGION WITH STRONG COLD ADVECTION
RESULTING IN A HEALTHY TEMP DROP PRIOR TO SUNRISE OVER NORTHERN CWA
AND SHORTLY AFTERWARD SOUTHEAST. STRONG NNW WINDS WILL ALSO ARRIVE
WITH THE COLD AIR AND CONTINUE INTO THIS EVENING RESULTING IN
TEMPERATURES LARGELY REMAINING FAIRLY STEADY THROUGH THE AFTERNOON.

COMPACT VORT AND REALLY THE HEART OF THE UPPER LOW SHOWS UP NICELY
OVER NORTHERN WISCONSIN EARLY THIS MORNING AND IS DIVING SSE TOWARD
THE AREA. THE COMBINATION OF ASCENT WITH THIS FEATURE AND STEEP
LAPSE RATES ARE RESULTING IN SCATTERED BUT FAIRLY VIGOROUS SNOW
SHOWERS OVER NORTHERN AND CENTRAL WISCONSIN AND WOULD FULLY
ANTICIPATE THESE TO MAINTAIN THEMSELVES AND MOVE ACROSS MAINLY THE
EASTERN CWA THIS MORNING. TEMPS WILL PROBABLY BE TOO WARM FOR MUCH
IF ANY ACCUMULATION...BUT SOME OF THE SNOW SHOWERS COULD BE BRIEFLY
VIGOROUS AND KNOCK VSBY DOWN TO BELOW 1SM. AS THE VORT CONTINUE
SOUTHEAST LOOK FOR THE NON-LAKE DRIVEN PRECIP TO END BY MID MORNING
NORTHERN CWA AND LATE MORNING SOUTHEAST CWA.

THE VORT WILL HERALD THE ARRIVAL OF THE COLDEST AIR ALOFT AND
RESULTANT STRONGEST INSTABILITY OVER THE LAKE AS H5 TEMPS DROP TO
-33C AND H7 TEMPS BELOW -15C. THERMODYNAMIC PROFILES OVER THE LAKE
BEHIND THIS VORT BECOME EXPLOSIVELY UNSTABLE THIS MORNING REMAIN SO
THROUGH THE DAY. LAKE EFFECT SHOULD GET GOING IN ERNEST BEHIND THIS
VORT AND CONTINUE TO SOME DEGREE INTO SATURDAY MORNING. FORECAST
LAKE INDUCED EQUILIBRIUM LEVELS TODAY APPROACH 20K FT...NEAR THE
-30C LEVEL...WHICH IS MORE THAN COLD ENOUGH TO SUPPORT LIGHTNING
GIVEN THE HIGH LIKELIHOOD OF MIXED PHASE HYDROMETEORS (SUPERCOOLED
DROPLETS AND ICE) IN THE CLOUDS WITHIN STRONG UPDRAFTS. NEAR SURFACE
TEMPS OVER THE LAKE AND WITHIN A FEW MILES OF THE LAKE SHORE MAY BE
WARM ENOUGH TO SUPPORT P-TYPE FLUCTUATING BETWEEN RAIN...RAIN/SNOW
MIX...AND ALL SNOW. LAKE EFFECT PRECIP FARTHER INLAND STANDS A MUCH
BETTER CHANCE OF REMAINING ALL OR MOSTLY SNOW.

ONE OF THE BIGGER UNCERTAINTIES FOR TODAY IS HOW ORGANIZED THE LAKE
EFFECT WILL BECOME AND WHETHER IT WILL BE MULTIPLE BANDS OR A SINGLE
INTENSE BAND. GIVEN THE VERY STRONG BOUNDARY LAYER WINDS AND LESS
THAN IDEAL TIME OF DAY AM CONCERNED THAT THE LAKE EFFECT PRECIP
COULD BE SOMEWHAT UNORGANIZED/SCATTERED IN NATURE WITH MULTIPLE
BANDS DURING THE DAY WHICH WILL BE THE TIME OF STRONG TO EXTREME
INSTABILITY. IF A MORE ORGANIZED DOMINANT SINGLE BAND DOES
FORM...THE STRONG FLOW AND INSTABILITY WELL INLAND WOULD SUPPORT
INTENSE PRECIP RATES MAKING IT WELL INLAND THIS AFTERNOON WHERE
P-TYPE WOULD LIKELY BE MOSTLY SNOW...POSSIBLY MODERATE TO HEAVY
SNOW. IF SNOW FALLS HEAVY ENOUGH THEN THE WARM GROUND TEMPS WOULD
BECOME MORE OF A MOOT POINT WITH RAPID ACCUMULATIONS OF HEAVY/WET
SNOW...ESPECIALLY ON GRASSY SURFACES WHERE ISOLATED LOCATIONS COULD
SEE A QUICK SEVERAL INCHES OF SNOW. THE MOST LIKELY SCENARIO WOULD
APPEAR TO BE SOMEWHAT LESS ORGANIZED BANDS OF SNOW SHOWERS RESULTING
IN ONLY MINOR ACCUMS ON GRASSY SURFACES IN SPOTS TODAY. THE WIND
WILL BE WHIPPING THE SNOW AROUND REGARDLESS SO UNDERNEATH ANY LAKE
EFFECT SNOW CONDITIONS WILL BE PRETTY MISERABLE EVEN THOUGH IT IS
UNLIKELY TO ACCUMULATE ON ROADS/SIDEWALKS TODAY. LAKE AND PORTER
COUNTY LOOK TO BE GROUND ZERO FOR THE LAKE EFFECT TODAY WITH THE
PRECIP LIKELY MAKING IT WELL INLAND TO JASPER AND NEWTON COUNTIES.
SOME HIGH RES GUIDANCE DOES CLIP SE COOK AND EASTERN WILL WITH LAKE
EFFECT PRECIP TODAY WHICH ISNT OUT OF THE QUESTION AND HAVE
MAINTAINED LOW POPS THERE.

THIS EVENING THE LOW LEVEL FLOW WILL GRADUALLY VEER AND SEND THE
LAKE EFFECT MORE INTO EASTERN COOK/EASTERN WILL/WESTERN LAKE IN (AND
EVEN POINTS SOUTH. BY THIS EVENING THE BOUNDARY LAYER FLOW WILL BE
WEAKENING AND THE TEMPS OUTSIDE OF THE LAKE INFLUENCED AREAS
DROPPING WHICH WOULD BOTH TEND TO FAVOR A TRANSITION TO A MORE
ORGANIZED DOMINANT SINGLE LAKE EFFECT BAND. MY BEST GUESS IS THAT
THE TIME WINDOW FOR THE HIGHEST PROBABILITY OF A DOMINANT LAKE
EFFECT BAND WITH POTENTIAL FOR HEAVY SNOW IS BETWEEN 23Z AND ABOUT
04Z. DURING THIS TIME PERIOD THE INSTABILITY (WHILE LESS THAN
EARLIER IN THE DAY) WILL STILL BE STRONG WITH INVERSION HEIGHTS
AROUND 10K FT AND LAKE-850 DELTA T VALUES >20C. DOES APPEARS A
PERIOD OF HEAVY SNOW COULD OCCUR IN EASTERN/SOUTHEASTERN COOK AND
EASTERN WILL COUNTIES EARLY THIS EVENING...BUT GIVEN THE LOW
CONFIDENCE OPTED NOT TO EXPAND THE WINTER WX HEADLINES AT THIS TIME
AND INSTEAD WILL ALLOW DAY SHIFT TO MONITOR MESOSCALE TRENDS. BY
LATER THIS EVENING INTO THE OVERNIGHT HOURS THE LAKE EFFECT
PARAMETERS WILL CONTINUE TO BECOME LESS FAVORABLE AND THE INTENSITY
OF THE LAKE EFFECT PRECIP SHOULD BEGIN TO WIND DOWN LATE TONIGHT AND
EVENTUALLY END SATURDAY. HAVE EXTENDED THE HIGHER POPS LATER IN TIME
AS LAKE EFFECT RARELY WINDS DOWN AS QUICKLY AS MODEL PROGGED
PARAMETERS SUGGEST IT WILL. WORTH NOTING THAT BY LATE EVENING AND
THROUGH SAT MORNING THE CONVECTIVE CLOUD TOP TEMPS DROP BELOW -12C
MEANING THE LIKELIHOOD OF CLOUDS CONTAINING ICE NUCLEI FOR SNOW WILL
BE LOW...SO DESPITE LOWER TEMPS IN THE BOUNDARY LAYER HAVE
TRANSITIONED P-TYPE BACK TO RAIN OR SNOW LATE TONIGHT AND SAT
MORNING.

FINALLY...HIGH WINDS WILL BE THE OTHER CONCERN TODAY. PLAN TO
MAINTAIN WIND ADVISORY AS IS THOUGH CONFIDENCE IN INLAND LOCATIONS
REACHING ADVISORY CRITERIA IS NOT THAT HIGH...BUT WITH GUSTS TO AT
LEAST 40 MPH A GOOD BET NOTHING WOULD BE GAINED FROM MAKING ANY
CHANGES TO THE HEADLINES. THE STORM WARNING FOR THE LAKE LOOKS
LIKELY TO VERIFY WITH 40 MPH SUSTAINED AND POSSIBLY GUSTS TO 58 MPH
LIKELY ALONG THE LAKE FRONT TODAY AND REALLY NOT COMFORTABLE NOT
HAVING A WARNING WITH THE POTENTIAL FOR DAMAGING WINDS ALONG THE
LAKE...SO AM GOING TO UPGRADE TO A HIGH WIND WARNING FOR LAKE SHORE
AREAS.

HEADLINES ARE AN ABSOLUTE MESS AND HEADACHE. WINTER WX ADVISORY
COVERS WIND AND SNOW...BUT IN ORDER TO GO WITH WARNING FOR WIND
ALONG THE LAKE FRONT IN INDIANA WOULD NEED TO UPGRADE TO A WINTER
STORM WARNING WHICH REALLY DOESNT SEEM TO BE THE BEST PRODUCT. AFTER
MUCH HEMMING AND HAWING AND INTERNAL COORDINATION HAVE OPTED TO
CHANGE THE WINTER WX ADV TO A LAKE EFFECT SNOW ADVISORY AND ISSUE A
WIND ADVISORY FOR JASPER AND NEWTON AND A HIGH WIND WARNING FOR LAKE
SHORE AREAS OF COOK...PORTER...AND LAKE IN. MAY NEED TO REPLACE THE
HIGH WIND WARNING WITH A WIND ADVISORY BY EARLY EVENING FOR

IZZI

&&

.LONG TERM...
325 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

MUCH...MUCH QUIETER SUNDAY AND MONDAY WITH MODERATING TEMPS. SLOW
MOVING FRONT COULD BRING A SOMEWHAT PROLONGED PERIOD OF RAIN/SHOWERS
MONDAY NIGHT THOUGH TUESDAY NIGHT. GENERALLY SEASONABLE TEMPS
EXPECTED THROUGH THE EXTENDED.

IZZI

&&

.AVIATION...

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

* OFF AND ON FLURRIES LATE THIS MORNING AND AFTERNOON WITH THE
  POSSIBILITY OF SOME TEMPORARY SNOW SHOWERS NAMELY AT MDW.

* NORTHWEST WINDS SHIFTING NORTH TOWARD 16Z-17Z WITH GUSTS OF 35
  TO 40 KT. GUST SPEEDS WILL BE ERRATIC AND 40 KT GUSTS SHOULD BE
  SPORADIC.

* PERIODIC MVFR CIGS THROUGH THE MORNING AND POSSIBLY INTO THE
  AFTERNOON...ALTHOUGH SHOULD REMAIN ABOVE 2000 FT.

* LAKE EFFECT SNOW SHOWERS COULD AFFECT MDW FROM EARLY EVENING
  ONWARD.

MTF/MDB

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

NORTH-NORTHWEST WINDS HAVE BEEN VERY STEADY AT 340-350 AT ORD AND
MDW. A SECONDARY COLD FRONT/TROUGH IS MOVING SOUTHWARD DOWN LAKE
MICHIGAN AND WISCONSIN AND THIS WILL TURN WINDS MORE DUE NORTH.
THIS IS SLIGHTLY LATER FOR DUE NORTH THAN PREVIOUS TAF. WIND SPEED
THINKING REMAINS THE SAME.

CONVECTIVE CLOUD TOPS ARE BEGINNING TO SHOW UP ACROSS THE CENTRAL
AND SOUTHERN PART OF THE LAKE SO IT IS POSSIBLE WE BEGIN TO SEE
SOME LIGHTNING AS WELL.


PREV DISCUSSION...UPDATED 12Z...

NORTHWEST WINDS HAVE BEEN STEADILY INCREASING EARLY THIS MORNING
AS STRONG HIGH PRESSURE APPROACHES FROM THE NORTHWEST. ONE UPPER
WAVE AND ASSOCIATED -SHRA IS DEPARTING WHILE ANOTHER IS APPROACHING
FROM THE NORTH. A PUSH OF COLDER AIR WITH THE NEXT WAVE IS
RESULTING IN A BAND OF SNOW SHOWERS WHICH HAS BEEN REDUCING VSBY
TO AROUND A MILE AT TIMES...AT LEAST BRIEFLY. EXPECT A 1-2 HR
WINDOW OF -SHSN AT THE TERMINALS OVER THE NEXT 2-3 HRS. VARIABLE
MVFR-VFR CIGS WILL CONTINUE THROUGH MUCH OF THE MORNING BEFORE
STEADIER VFR IS EXPECTED ACROSS THE ILLINOIS TERMINALS WITH
SCATTERING OF CLOUDS WEST.

WINDS WILL TURN TO THE NORTH WITH THE PASSAGE OF THE UPPER WAVE
THIS MORNING AND EXPECT TO SEE A SURGE IN GUSTS AT THAT TIME. 35
TO 40 KT GUSTS ARE EXPECTED BUT AM NOT HIGHLY CONFIDENT IN HOW
FREQUENTLY 40 KT MAY BE REACHED. IT APPEARS THAT MID MORNING MAY
BE ONE POTENTIALLY PRIME PERIOD BEHIND THE UPPER WAVE/PRECIP WITH
THE NEXT POTENTIALLY FAVORED TIME BEING MID AFTERNOON IF SKIES CAN
SCATTER. IT MAY BE THAT AN OCCASIONAL 40 KT GUST OCCURS AT ANY
POINT THROUGH THE DAY. WINDS WILL EASE THIS EVENING.

LAKE EFFECT PRECIPITATION IS EXPECTED TO DEVELOP MID TO LATE
MORNING AND FOCUS ACROSS NORTHWEST INDIANA WITH GYY POSSIBLY BEING
ON THE WESTERN FRINGE INITIALLY BUT LIKELY GETTING INTO THE PRIME
BANDING INTO THE AFTERNOON. GIVEN THEIR PROXIMITY TO THE FAIRLY
WARM LAKE A RAIN SNOW MIX IS FAVORED TURNING TO ALL SNOW IF VERY
INTENSE BANDING CAN OCCUR. THUNDER IS ALSO POSSIBLE AND WOULD
ENHANCE THE ALL SNOW POTENTIAL. AS A RESULT IFR VSBY WILL LIKELY
OCCUR AT TIMES BUT THERE ARE FACTORS THAT MAY LIMIT THE
ORGANIZATION OF THE PRECIP. WINDS WILL LIKELY GUST 40-45 KT WITH
50 NOT OUT OF THE QUESTION TOWARD MIDDAY. LAKE EFFECT PRECIP WILL
LIKELY TURN TO ALL SNOW THIS EVENING AND SHIFT WESTWARD TOWARD THE
IL/IN STATE LINE AND POSSIBLY BEGIN TO IMPACT MDW WITH LIGHT
ACCUMULATIONS POSSIBLE...MAINLY ON THE GRASS. SEVERAL HOURS OF
SNOW MAY OCCUR AT OR NEAR MDW. ADJUSTMENTS TO THE FORECAST DETAILS
THIS EVENING AT MDW/GYY AND EVEN ORD ARE LIKELY.

MDB

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

* LOW ON IF IFR SNOW SHOWERS MAY IMPACT MDW THIS AFTERNOON.
  MEDIUM THAT THEY WILL STAY EAST OF ORD.

* HIGH IN NORTHWEST WINDS TURNING DUE NORTH AND MEDIUM IN TIMING.
  HIGH IN WIND SPEEDS AND THAT ANY GUSTS TO 40 KT WILL BE
  TEMPORARY.

* MEDIUM IN MVFR CIGS. HIGH THAT THEY WILL REMAIN ABOVE 2000 FT
  AT ORD...MEDIUM AT MDW.

* MEDIUM IN LAKE EFFECT SNOW SHOWER POTENTIAL TONIGHT AT MDW...LOW
  AT ORD.

MTF/MDB


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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MDB

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014 UNTIL 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002 UNTIL 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011 UNTIL 10
     PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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000
FXUS63 KLOT 311150
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
650 AM CDT FRI OCT 31 2014

.SHORT TERM...
326 AM CDT

THROUGH SATURDAY...

ACTIVE WEATHER ON TAP THE NEXT 24 HOURS AS COMPACT AND DEEP UPPER
LOW DIVES SOUTH ACROSS THE REGION DRAGGING UNSEASONABLY COLD
AIR...BOTH AT THE SURFACE AND ALOFT...INTO THE REGION TODAY INTO
TONIGHT. EARLY THIS MORNING SURFACE ANALYSIS SHOWS A RATHER DIFFUSE
COLD FRONT MOVING ACROSS THE REGION WITH STRONG COLD ADVECTION
RESULTING IN A HEALTHY TEMP DROP PRIOR TO SUNRISE OVER NORTHERN CWA
AND SHORTLY AFTERWARD SOUTHEAST. STRONG NNW WINDS WILL ALSO ARRIVE
WITH THE COLD AIR AND CONTINUE INTO THIS EVENING RESULTING IN
TEMPERATURES LARGELY REMAINING FAIRLY STEADY THROUGH THE AFTERNOON.

COMPACT VORT AND REALLY THE HEART OF THE UPPER LOW SHOWS UP NICELY
OVER NORTHERN WISCONSIN EARLY THIS MORNING AND IS DIVING SSE TOWARD
THE AREA. THE COMBINATION OF ASCENT WITH THIS FEATURE AND STEEP
LAPSE RATES ARE RESULTING IN SCATTERED BUT FAIRLY VIGOROUS SNOW
SHOWERS OVER NORTHERN AND CENTRAL WISCONSIN AND WOULD FULLY
ANTICIPATE THESE TO MAINTAIN THEMSELVES AND MOVE ACROSS MAINLY THE
EASTERN CWA THIS MORNING. TEMPS WILL PROBABLY BE TOO WARM FOR MUCH
IF ANY ACCUMULATION...BUT SOME OF THE SNOW SHOWERS COULD BE BRIEFLY
VIGOROUS AND KNOCK VSBY DOWN TO BELOW 1SM. AS THE VORT CONTINUE
SOUTHEAST LOOK FOR THE NON-LAKE DRIVEN PRECIP TO END BY MID MORNING
NORTHERN CWA AND LATE MORNING SOUTHEAST CWA.

THE VORT WILL HERALD THE ARRIVAL OF THE COLDEST AIR ALOFT AND
RESULTANT STRONGEST INSTABILITY OVER THE LAKE AS H5 TEMPS DROP TO
-33C AND H7 TEMPS BELOW -15C. THERMODYNAMIC PROFILES OVER THE LAKE
BEHIND THIS VORT BECOME EXPLOSIVELY UNSTABLE THIS MORNING REMAIN SO
THROUGH THE DAY. LAKE EFFECT SHOULD GET GOING IN ERNEST BEHIND THIS
VORT AND CONTINUE TO SOME DEGREE INTO SATURDAY MORNING. FORECAST
LAKE INDUCED EQUILIBRIUM LEVELS TODAY APPROACH 20K FT...NEAR THE
-30C LEVEL...WHICH IS MORE THAN COLD ENOUGH TO SUPPORT LIGHTNING
GIVEN THE HIGH LIKELIHOOD OF MIXED PHASE HYDROMETEORS (SUPERCOOLED
DROPLETS AND ICE) IN THE CLOUDS WITHIN STRONG UPDRAFTS. NEAR SURFACE
TEMPS OVER THE LAKE AND WITHIN A FEW MILES OF THE LAKE SHORE MAY BE
WARM ENOUGH TO SUPPORT P-TYPE FLUCTUATING BETWEEN RAIN...RAIN/SNOW
MIX...AND ALL SNOW. LAKE EFFECT PRECIP FARTHER INLAND STANDS A MUCH
BETTER CHANCE OF REMAINING ALL OR MOSTLY SNOW.

ONE OF THE BIGGER UNCERTAINTIES FOR TODAY IS HOW ORGANIZED THE LAKE
EFFECT WILL BECOME AND WHETHER IT WILL BE MULTIPLE BANDS OR A SINGLE
INTENSE BAND. GIVEN THE VERY STRONG BOUNDARY LAYER WINDS AND LESS
THAN IDEAL TIME OF DAY AM CONCERNED THAT THE LAKE EFFECT PRECIP
COULD BE SOMEWHAT UNORGANIZED/SCATTERED IN NATURE WITH MULTIPLE
BANDS DURING THE DAY WHICH WILL BE THE TIME OF STRONG TO EXTREME
INSTABILITY. IF A MORE ORGANIZED DOMINANT SINGLE BAND DOES
FORM...THE STRONG FLOW AND INSTABILITY WELL INLAND WOULD SUPPORT
INTENSE PRECIP RATES MAKING IT WELL INLAND THIS AFTERNOON WHERE
P-TYPE WOULD LIKELY BE MOSTLY SNOW...POSSIBLY MODERATE TO HEAVY
SNOW. IF SNOW FALLS HEAVY ENOUGH THEN THE WARM GROUND TEMPS WOULD
BECOME MORE OF A MOOT POINT WITH RAPID ACCUMULATIONS OF HEAVY/WET
SNOW...ESPECIALLY ON GRASSY SURFACES WHERE ISOLATED LOCATIONS COULD
SEE A QUICK SEVERAL INCHES OF SNOW. THE MOST LIKELY SCENARIO WOULD
APPEAR TO BE SOMEWHAT LESS ORGANIZED BANDS OF SNOW SHOWERS RESULTING
IN ONLY MINOR ACCUMS ON GRASSY SURFACES IN SPOTS TODAY. THE WIND
WILL BE WHIPPING THE SNOW AROUND REGARDLESS SO UNDERNEATH ANY LAKE
EFFECT SNOW CONDITIONS WILL BE PRETTY MISERABLE EVEN THOUGH IT IS
UNLIKELY TO ACCUMULATE ON ROADS/SIDEWALKS TODAY. LAKE AND PORTER
COUNTY LOOK TO BE GROUND ZERO FOR THE LAKE EFFECT TODAY WITH THE
PRECIP LIKELY MAKING IT WELL INLAND TO JASPER AND NEWTON COUNTIES.
SOME HIGH RES GUIDANCE DOES CLIP SE COOK AND EASTERN WILL WITH LAKE
EFFECT PRECIP TODAY WHICH ISNT OUT OF THE QUESTION AND HAVE
MAINTAINED LOW POPS THERE.

THIS EVENING THE LOW LEVEL FLOW WILL GRADUALLY VEER AND SEND THE
LAKE EFFECT MORE INTO EASTERN COOK/EASTERN WILL/WESTERN LAKE IN (AND
EVEN POINTS SOUTH. BY THIS EVENING THE BOUNDARY LAYER FLOW WILL BE
WEAKENING AND THE TEMPS OUTSIDE OF THE LAKE INFLUENCED AREAS
DROPPING WHICH WOULD BOTH TEND TO FAVOR A TRANSITION TO A MORE
ORGANIZED DOMINANT SINGLE LAKE EFFECT BAND. MY BEST GUESS IS THAT
THE TIME WINDOW FOR THE HIGHEST PROBABILITY OF A DOMINANT LAKE
EFFECT BAND WITH POTENTIAL FOR HEAVY SNOW IS BETWEEN 23Z AND ABOUT
04Z. DURING THIS TIME PERIOD THE INSTABILITY (WHILE LESS THAN
EARLIER IN THE DAY) WILL STILL BE STRONG WITH INVERSION HEIGHTS
AROUND 10K FT AND LAKE-850 DELTA T VALUES >20C. DOES APPEARS A
PERIOD OF HEAVY SNOW COULD OCCUR IN EASTERN/SOUTHEASTERN COOK AND
EASTERN WILL COUNTIES EARLY THIS EVENING...BUT GIVEN THE LOW
CONFIDENCE OPTED NOT TO EXPAND THE WINTER WX HEADLINES AT THIS TIME
AND INSTEAD WILL ALLOW DAY SHIFT TO MONITOR MESOSCALE TRENDS. BY
LATER THIS EVENING INTO THE OVERNIGHT HOURS THE LAKE EFFECT
PARAMETERS WILL CONTINUE TO BECOME LESS FAVORABLE AND THE INTENSITY
OF THE LAKE EFFECT PRECIP SHOULD BEGIN TO WIND DOWN LATE TONIGHT AND
EVENTUALLY END SATURDAY. HAVE EXTENDED THE HIGHER POPS LATER IN TIME
AS LAKE EFFECT RARELY WINDS DOWN AS QUICKLY AS MODEL PROGGED
PARAMETERS SUGGEST IT WILL. WORTH NOTING THAT BY LATE EVENING AND
THROUGH SAT MORNING THE CONVECTIVE CLOUD TOP TEMPS DROP BELOW -12C
MEANING THE LIKELIHOOD OF CLOUDS CONTAINING ICE NUCLEI FOR SNOW WILL
BE LOW...SO DESPITE LOWER TEMPS IN THE BOUNDARY LAYER HAVE
TRANSITIONED P-TYPE BACK TO RAIN OR SNOW LATE TONIGHT AND SAT
MORNING.

FINALLY...HIGH WINDS WILL BE THE OTHER CONCERN TODAY. PLAN TO
MAINTAIN WIND ADVISORY AS IS THOUGH CONFIDENCE IN INLAND LOCATIONS
REACHING ADVISORY CRITERIA IS NOT THAT HIGH...BUT WITH GUSTS TO AT
LEAST 40 MPH A GOOD BET NOTHING WOULD BE GAINED FROM MAKING ANY
CHANGES TO THE HEADLINES. THE STORM WARNING FOR THE LAKE LOOKS
LIKELY TO VERIFY WITH 40 MPH SUSTAINED AND POSSIBLY GUSTS TO 58 MPH
LIKELY ALONG THE LAKE FRONT TODAY AND REALLY NOT COMFORTABLE NOT
HAVING A WARNING WITH THE POTENTIAL FOR DAMAGING WINDS ALONG THE
LAKE...SO AM GOING TO UPGRADE TO A HIGH WIND WARNING FOR LAKE SHORE
AREAS.

HEADLINES ARE AN ABSOLUTE MESS AND HEADACHE. WINTER WX ADVISORY
COVERS WIND AND SNOW...BUT IN ORDER TO GO WITH WARNING FOR WIND
ALONG THE LAKE FRONT IN INDIANA WOULD NEED TO UPGRADE TO A WINTER
STORM WARNING WHICH REALLY DOESNT SEEM TO BE THE BEST PRODUCT. AFTER
MUCH HEMMING AND HAWING AND INTERNAL COORDINATION HAVE OPTED TO
CHANGE THE WINTER WX ADV TO A LAKE EFFECT SNOW ADVISORY AND ISSUE A
WIND ADVISORY FOR JASPER AND NEWTON AND A HIGH WIND WARNING FOR LAKE
SHORE AREAS OF COOK...PORTER...AND LAKE IN. MAY NEED TO REPLACE THE
HIGH WIND WARNING WITH A WIND ADVISORY BY EARLY EVENING FOR

IZZI

&&

.LONG TERM...
325 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

MUCH...MUCH QUIETER SUNDAY AND MONDAY WITH MODERATING TEMPS. SLOW
MOVING FRONT COULD BRING A SOMEWHAT PROLONGED PERIOD OF RAIN/SHOWERS
MONDAY NIGHT THOUGH TUESDAY NIGHT. GENERALLY SEASONABLE TEMPS
EXPECTED THROUGH THE EXTENDED.

IZZI

&&

.AVIATION...

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

* 1-2 HR PERIOD OF -SHSN TIL ABOUT 14Z. BRIEF IFR VSBY AROUND 1SM.

* NORTHWEST WINDS SHIFTING NORTH TOWARD 15Z WITH GUSTS INCREASING
  TO 35-40 KT. GUST SPEEDS MAY BE VERY ERRATIC AND NOT CLEAR ON
  HOW FREQUENT 40 KT GUSTS COULD BE.

* PERIODIC MVFR CIGS THROUGH THE MORNING.

* LAKE EFFECT SNOW SHOWERS COULD AFFECT MDW FROM EARLY EVENING
  ONWARD.

MDB

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

NORTHWEST WINDS HAVE BEEN STEADILY INCREASING EARLY THIS MORNING
AS STRONG HIGH PRESSURE APPROACHES FROM THE NORTHWEST. ONE UPPER
WAVE AND ASSOCIATED -SHRA IS DEPARTING WHILE ANOTHER IS APPROACHING
FROM THE NORTH. A PUSH OF COLDER AIR WITH THE NEXT WAVE IS
RESULTING IN A BAND OF SNOW SHOWERS WHICH HAS BEEN REDUCING VSBY
TO AROUND A MILE AT TIMES...AT LEAST BRIEFLY. EXPECT A 1-2 HR
WINDOW OF -SHSN AT THE TERMINALS OVER THE NEXT 2-3 HRS. VARIABLE
MVFR-VFR CIGS WILL CONTINUE THROUGH MUCH OF THE MORNING BEFORE
STEADIER VFR IS EXPECTED ACROSS THE ILLINOIS TERMINALS WITH
SCATTERING OF CLOUDS WEST.

WINDS WILL TURN TO THE NORTH WITH THE PASSAGE OF THE UPPER WAVE
THIS MORNING AND EXPECT TO SEE A SURGE IN GUSTS AT THAT TIME. 35
TO 40 KT GUSTS ARE EXPECTED BUT AM NOT HIGHLY CONFIDENT IN HOW
FREQUENTLY 40 KT MAY BE REACHED. IT APPEARS THAT MID MORNING MAY
BE ONE POTENTIALLY PRIME PERIOD BEHIND THE UPPER WAVE/PRECIP WITH
THE NEXT POTENTIALLY FAVORED TIME BEING MID AFTERNOON IF SKIES CAN
SCATTER. IT MAY BE THAT AN OCCASIONAL 40 KT GUST OCCURS AT ANY
POINT THROUGH THE DAY. WINDS WILL EASE THIS EVENING.

LAKE EFFECT PRECIPITATION IS EXPECTED TO DEVELOP MID TO LATE
MORNING AND FOCUS ACROSS NORTHWEST INDIANA WITH GYY POSSIBLY BEING
ON THE WESTERN FRINGE INITIALLY BUT LIKELY GETTING INTO THE PRIME
BANDING INTO THE AFTERNOON. GIVEN THEIR PROXIMITY TO THE FAIRLY
WARM LAKE A RAIN SNOW MIX IS FAVORED TURNING TO ALL SNOW IF VERY
INTENSE BANDING CAN OCCUR. THUNDER IS ALSO POSSIBLE AND WOULD
ENHANCE THE ALL SNOW POTENTIAL. AS A RESULT IFR VSBY WILL LIKELY
OCCUR AT TIMES BUT THERE ARE FACTORS THAT MAY LIMIT THE
ORGANIZATION OF THE PRECIP. WINDS WILL LIKELY GUST 40-45 KT WITH
50 NOT OUT OF THE QUESTION TOWARD MIDDAY. LAKE EFFECT PRECIP WILL
LIKELY TURN TO ALL SNOW THIS EVENING AND SHIFT WESTWARD TOWARD THE
IL/IN STATE LINE AND POSSIBLY BEGIN TO IMPACT MDW WITH LIGHT
ACCUMULATIONS POSSIBLE...MAINLY ON THE GRASS. SEVERAL HOURS OF
SNOW MAY OCCUR AT OR NEAR MDW. ADJUSTMENTS TO THE FORECAST DETAILS
THIS EVENING AT MDW/GYY AND EVEN ORD ARE LIKELY.

MDB

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

* HIGH CONFIDENCE IN SNOW SHOWERS THIS MORNING...HIGH CONFIDENCE
  IN DURATION...MEDIUM-HIGH CONFIDENCE IN BRIEF IFR VSBY
  OCCURRING.

* HIGH CONFIDENCE IN NORTHWEST WINDS TURNING NORTH AND IN GUSTS
  REACHING 35-37 KT...MEDIUM CONFIDENCE THAT SOME 40 KT GUSTS WILL
  OCCUR BUT LOW CONFIDENCE IN FREQUENCY AND BEST TIMING.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC MVFR CIGS THROUGH THE
  MORNING.

* LOW CONFIDENCE IN LAKE EFFECT SNOW SHOWER POTENTIAL THIS EVENING
  AT ORD...MEDIUM CONFIDENCE AT MDW.

MDB

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

* SATURDAY NIGHT...DRY VFR. LIGHT/VARIABLE WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.
* THURSDAY...DRY/VFR. WEST WINDS.

MDB

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014...10 AM FRIDAY TO 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033 UNTIL 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002...10 AM FRIDAY TO 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019 UNTIL 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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000
FXUS63 KLOT 310922
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
422 AM CDT FRI OCT 31 2014

.SHORT TERM...
326 AM CDT

THROUGH SATURDAY...

ACTIVE WEATHER ON TAP THE NEXT 24 HOURS AS COMPACT AND DEEP UPPER
LOW DIVES SOUTH ACROSS THE REGION DRAGGING UNSEASONABLY COLD
AIR...BOTH AT THE SURFACE AND ALOFT...INTO THE REGION TODAY INTO
TONIGHT. EARLY THIS MORNING SURFACE ANALYSIS SHOWS A RATHER DIFFUSE
COLD FRONT MOVING ACROSS THE REGION WITH STRONG COLD ADVECTION
RESULTING IN A HEALTHY TEMP DROP PRIOR TO SUNRISE OVER NORTHERN CWA
AND SHORTLY AFTERWARD SOUTHEAST. STRONG NNW WINDS WILL ALSO ARRIVE
WITH THE COLD AIR AND CONTINUE INTO THIS EVENING RESULTING IN
TEMPERATURES LARGELY REMAINING FAIRLY STEADY THROUGH THE AFTERNOON.

COMPACT VORT AND REALLY THE HEART OF THE UPPER LOW SHOWS UP NICELY
OVER NORTHERN WISCONSIN EARLY THIS MORNING AND IS DIVING SSE TOWARD
THE AREA. THE COMBINATION OF ASCENT WITH THIS FEATURE AND STEEP
LAPSE RATES ARE RESULTING IN SCATTERED BUT FAIRLY VIGOROUS SNOW
SHOWERS OVER NORTHERN AND CENTRAL WISCONSIN AND WOULD FULLY
ANTICIPATE THESE TO MAINTAIN THEMSELVES AND MOVE ACROSS MAINLY THE
EASTERN CWA THIS MORNING. TEMPS WILL PROBABLY BE TOO WARM FOR MUCH
IF ANY ACCUMULATION...BUT SOME OF THE SNOW SHOWERS COULD BE BRIEFLY
VIGOROUS AND KNOCK VSBY DOWN TO BELOW 1SM. AS THE VORT CONTINUE
SOUTHEAST LOOK FOR THE NON-LAKE DRIVEN PRECIP TO END BY MID MORNING
NORTHERN CWA AND LATE MORNING SOUTHEAST CWA.

THE VORT WILL HERALD THE ARRIVAL OF THE COLDEST AIR ALOFT AND
RESULTANT STRONGEST INSTABILITY OVER THE LAKE AS H5 TEMPS DROP TO
-33C AND H7 TEMPS BELOW -15C. THERMODYNAMIC PROFILES OVER THE LAKE
BEHIND THIS VORT BECOME EXPLOSIVELY UNSTABLE THIS MORNING REMAIN SO
THROUGH THE DAY. LAKE EFFECT SHOULD GET GOING IN ERNEST BEHIND THIS
VORT AND CONTINUE TO SOME DEGREE INTO SATURDAY MORNING. FORECAST
LAKE INDUCED EQUILIBRIUM LEVELS TODAY APPROACH 20K FT...NEAR THE
-30C LEVEL...WHICH IS MORE THAN COLD ENOUGH TO SUPPORT LIGHTNING
GIVEN THE HIGH LIKELIHOOD OF MIXED PHASE HYDROMETEORS (SUPERCOOLED
DROPLETS AND ICE) IN THE CLOUDS WITHIN STRONG UPDRAFTS. NEAR SURFACE
TEMPS OVER THE LAKE AND WITHIN A FEW MILES OF THE LAKE SHORE MAY BE
WARM ENOUGH TO SUPPORT P-TYPE FLUCTUATING BETWEEN RAIN...RAIN/SNOW
MIX...AND ALL SNOW. LAKE EFFECT PRECIP FARTHER INLAND STANDS A MUCH
BETTER CHANCE OF REMAINING ALL OR MOSTLY SNOW.

ONE OF THE BIGGER UNCERTAINTIES FOR TODAY IS HOW ORGANIZED THE LAKE
EFFECT WILL BECOME AND WHETHER IT WILL BE MULTIPLE BANDS OR A SINGLE
INTENSE BAND. GIVEN THE VERY STRONG BOUNDARY LAYER WINDS AND LESS
THAN IDEAL TIME OF DAY AM CONCERNED THAT THE LAKE EFFECT PRECIP
COULD BE SOMEWHAT UNORGANIZED/SCATTERED IN NATURE WITH MULTIPLE
BANDS DURING THE DAY WHICH WILL BE THE TIME OF STRONG TO EXTREME
INSTABILITY. IF A MORE ORGANIZED DOMINANT SINGLE BAND DOES
FORM...THE STRONG FLOW AND INSTABILITY WELL INLAND WOULD SUPPORT
INTENSE PRECIP RATES MAKING IT WELL INLAND THIS AFTERNOON WHERE
P-TYPE WOULD LIKELY BE MOSTLY SNOW...POSSIBLY MODERATE TO HEAVY
SNOW. IF SNOW FALLS HEAVY ENOUGH THEN THE WARM GROUND TEMPS WOULD
BECOME MORE OF A MOOT POINT WITH RAPID ACCUMULATIONS OF HEAVY/WET
SNOW...ESPECIALLY ON GRASSY SURFACES WHERE ISOLATED LOCATIONS COULD
SEE A QUICK SEVERAL INCHES OF SNOW. THE MOST LIKELY SCENARIO WOULD
APPEAR TO BE SOMEWHAT LESS ORGANIZED BANDS OF SNOW SHOWERS RESULTING
IN ONLY MINOR ACCUMS ON GRASSY SURFACES IN SPOTS TODAY. THE WIND
WILL BE WHIPPING THE SNOW AROUND REGARDLESS SO UNDERNEATH ANY LAKE
EFFECT SNOW CONDITIONS WILL BE PRETTY MISERABLE EVEN THOUGH IT IS
UNLIKELY TO ACCUMULATE ON ROADS/SIDEWALKS TODAY. LAKE AND PORTER
COUNTY LOOK TO BE GROUND ZERO FOR THE LAKE EFFECT TODAY WITH THE
PRECIP LIKELY MAKING IT WELL INLAND TO JASPER AND NEWTON COUNTIES.
SOME HIGH RES GUIDANCE DOES CLIP SE COOK AND EASTERN WILL WITH LAKE
EFFECT PRECIP TODAY WHICH ISNT OUT OF THE QUESTION AND HAVE
MAINTAINED LOW POPS THERE.

THIS EVENING THE LOW LEVEL FLOW WILL GRADUALLY VEER AND SEND THE
LAKE EFFECT MORE INTO EASTERN COOK/EASTERN WILL/WESTERN LAKE IN (AND
EVEN POINTS SOUTH. BY THIS EVENING THE BOUNDARY LAYER FLOW WILL BE
WEAKENING AND THE TEMPS OUTSIDE OF THE LAKE INFLUENCED AREAS
DROPPING WHICH WOULD BOTH TEND TO FAVOR A TRANSITION TO A MORE
ORGANIZED DOMINANT SINGLE LAKE EFFECT BAND. MY BEST GUESS IS THAT
THE TIME WINDOW FOR THE HIGHEST PROBABILITY OF A DOMINANT LAKE
EFFECT BAND WITH POTENTIAL FOR HEAVY SNOW IS BETWEEN 23Z AND ABOUT
04Z. DURING THIS TIME PERIOD THE INSTABILITY (WHILE LESS THAN
EARLIER IN THE DAY) WILL STILL BE STRONG WITH INVERSION HEIGHTS
AROUND 10K FT AND LAKE-850 DELTA T VALUES >20C. DOES APPEARS A
PERIOD OF HEAVY SNOW COULD OCCUR IN EASTERN/SOUTHEASTERN COOK AND
EASTERN WILL COUNTIES EARLY THIS EVENING...BUT GIVEN THE LOW
CONFIDENCE OPTED NOT TO EXPAND THE WINTER WX HEADLINES AT THIS TIME
AND INSTEAD WILL ALLOW DAY SHIFT TO MONITOR MESOSCALE TRENDS. BY
LATER THIS EVENING INTO THE OVERNIGHT HOURS THE LAKE EFFECT
PARAMETERS WILL CONTINUE TO BECOME LESS FAVORABLE AND THE INTENSITY
OF THE LAKE EFFECT PRECIP SHOULD BEGIN TO WIND DOWN LATE TONIGHT AND
EVENTUALLY END SATURDAY. HAVE EXTENDED THE HIGHER POPS LATER IN TIME
AS LAKE EFFECT RARELY WINDS DOWN AS QUICKLY AS MODEL PROGGED
PARAMETERS SUGGEST IT WILL. WORTH NOTING THAT BY LATE EVENING AND
THROUGH SAT MORNING THE CONVECTIVE CLOUD TOP TEMPS DROP BELOW -12C
MEANING THE LIKELIHOOD OF CLOUDS CONTAINING ICE NUCLEI FOR SNOW WILL
BE LOW...SO DESPITE LOWER TEMPS IN THE BOUNDARY LAYER HAVE
TRANSITIONED P-TYPE BACK TO RAIN OR SNOW LATE TONIGHT AND SAT
MORNING.

FINALLY...HIGH WINDS WILL BE THE OTHER CONCERN TODAY. PLAN TO
MAINTAIN WIND ADVISORY AS IS THOUGH CONFIDENCE IN INLAND LOCATIONS
REACHING ADVISORY CRITERIA IS NOT THAT HIGH...BUT WITH GUSTS TO AT
LEAST 40 MPH A GOOD BET NOTHING WOULD BE GAINED FROM MAKING ANY
CHANGES TO THE HEADLINES. THE STORM WARNING FOR THE LAKE LOOKS
LIKELY TO VERIFY WITH 40 MPH SUSTAINED AND POSSIBLY GUSTS TO 58 MPH
LIKELY ALONG THE LAKE FRONT TODAY AND REALLY NOT COMFORTABLE NOT
HAVING A WARNING WITH THE POTENTIAL FOR DAMAGING WINDS ALONG THE
LAKE...SO AM GOING TO UPGRADE TO A HIGH WIND WARNING FOR LAKE SHORE
AREAS.

HEADLINES ARE AN ABSOLUTE MESS AND HEADACHE. WINTER WX ADVISORY
COVERS WIND AND SNOW...BUT IN ORDER TO GO WITH WARNING FOR WIND
ALONG THE LAKE FRONT IN INDIANA WOULD NEED TO UPGRADE TO A WINTER
STORM WARNING WHICH REALLY DOESNT SEEM TO BE THE BEST PRODUCT. AFTER
MUCH HEMMING AND HAWING AND INTERNAL COORDINATION HAVE OPTED TO
CHANGE THE WINTER WX ADV TO A LAKE EFFECT SNOW ADVISORY AND ISSUE A
WIND ADVISORY FOR JASPER AND NEWTON AND A HIGH WIND WARNING FOR LAKE
SHORE AREAS OF COOK...PORTER...AND LAKE IN. MAY NEED TO REPLACE THE
HIGH WIND WARNING WITH A WIND ADVISORY BY EARLY EVENING FOR

IZZI

&&

.LONG TERM...
325 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

MUCH...MUCH QUIETER SUNDAY AND MONDAY WITH MODERATING TEMPS. SLOW
MOVING FRONT COULD BRING A SOMEWHAT PROLONGED PERIOD OF RAIN/SHOWERS
MONDAY NIGHT THOUGH TUESDAY NIGHT. GENERALLY SEASONABLE TEMPS
EXPECTED THROUGH THE EXTENDED.

IZZI

&&

.AVIATION...

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

* FEW HOUR PERIOD OF SNOW SHOWERS AROUND/AFTER DAYBREAK. BRIEF IFR
  VSBY POSSIBLE.

* NORTHWEST WINDS SHIFTING NORTH AFTER DAYBREAK WITH GUSTS
  INCREASING TO 35-40 KT. NOT CLEAR ON FREQUENCY OF 40 KT GUSTS.

* PERIODIC MVFR CIGS THROUGH THE MORNING.

* LAKE EFFECT SNOW SHOWERS COULD AFFECT MDW FROM EARLY EVENING
  ONWARD.

MDB

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

WINDS HAVE SHIFTED NORTHWEST WITH GUST FREQUENCY/INTENSITY PICKING
UP. LIGHT RAIN SHOWERS CONTINUE TO MOVE SOUTHEAST ACROSS THE
TERMINALS WITH ONE UPPER WAVE. ANOTHER WAVE IS MOVING SOUTHWARD
ACROSS CENTRAL WISCONSIN AND GENERATING BANDS OF SNOW AS COLDER
AIR SPILLS IN. HAVE HIT SNOW SHOWER MENTION A LITTLE HARDER FOR A
FEW HOURS BETWEEN 12 AND 15Z OR SO. BRIEF IFR VSBY IS POSSIBLE
WITH A FEW SITES HAVING REPORTED ANYWHERE FROM 1/2 TO 3 SM
UPSTREAM. SUSPECT THAT MANY SITES HAVE BEEN TO 2-3SM OR LOWER BUT
DURATION WAS TOO BRIEF TO MAKE IT INTO THE TRANSMITTED OB. NOT
EXPECTING ANY ACCUMULATION WITH THESE SNOW SHOWERS BUT VSBY COULD
BE BRIEFLY REDUCED LOWER THAN WHAT THE TAFS CURRENTLY SHOW. GUST
MAGNITUDE/FREQUENCY REMAIN A CHALLENGE ESPECIALLY AT ORD/MDW GIVEN
POTENTIAL FOR CLOUD COVER TO LIMIT PEAK GUSTS.

FROM 06Z...

NUMEROUS FORECAST CONCERNS CONTINUE WITH LOW PRESSURE OVER LAKE
HURON TRACKING SOUTHEAST AND VERY STRONG HIGH PRESSURE OVER THE
NORTHERN PLAINS TRAILING IT. WINDS ARE BEGINNING TO TURN NORTHWEST
WITH A COLD FRONT ENTERING NORTHWEST ILLINOIS AT 06Z AND MOVING
SOUTHEAST. WINDS WILL INCREASE IN SPEED OVER THE NEXT SEVERAL
HOURS. A SERIES OF UPPER DISTURBANCES WILL CROSS THE AREA THROUGH
THE MORNING WITH THE FIRST NOW BRINGING RAIN SHOWERS TO THE
TERMINALS. THE NEXT WILL ARRIVE OVERNIGHT BRINGING INTERMITTENT
SHOWERS WITH A BETTER DEFINED WAVE CROSSING THE AREA AROUND/AFTER
DAYBREAK BRINGING SNOW SHOWERS AS MUCH COLDER AIR ARRIVES. AREAS
OF NORTHERN WISCONSIN ARE SEEING IFR SNOW THIS HOUR BUT THESE
HEAVIER BURSTS ARE EXPECTED TO TRACK TO THE EAST OF THE TERMINALS.
STILL CANNOT RULE OUT A BRIEF HEAVIER BURST OF NON-ACCUMULATING
SNOW AT ORD/MDW/GYY BUT WILL CONTINUE WITH MINIMAL VSBY
RESTRICTION. OTHERWISE EXPECT INTERMITTENT MVFR CIGS TO DEVELOP
WITH QUITE A BIT OF VARIABILITY BASED ON UPSTREAM CONDITIONS.

WINDS FURTHER INCREASE BEHIND THIS SNOW PRODUCING WAVE WITH GUSTS
OF 35-40 KT EXPECTED. IT IS UNCLEAR HOW FREQUENT THAT 40 KT GUSTS
WILL OCCUR BUT AM FAIRLY CONFIDENT THAT THEY WILL. AM THINKING
THAT THERE MAY BE TWO SEPARATE WINDOWS WHERE 40 KT WILL BE MOST
LIKELY...ONE BEING MID/LATE MORNING BEHIND THE SNOW PRODUCING WAVE
AND THE OTHER BEING MID AFTERNOON WHEN SKIES ARE MOST LIKELY TO
SCATTER. WITH OVERALL CONFIDENCE IN 40 KT FREQUENCY ON THE LOW
SIDE WILL CONTINUE WITH PREVIOUS DURATION FOR NOW BUT WILL ATTEMPT
TO REFINE WITH THE NEXT UPDATE IF POSSIBLE.

THE NEXT ISSUE WILL BE LAKE EFFECT PRECIPITATION. GYY LOOKS TO BE
IN LINE FOR LAKE EFFECT RAIN/SNOW AND POSSIBLY PERIODS OF ALL SNOW
FROM LATE MORNING INTO THE EVENING. THUNDER IS ALSO POSSIBLE AS
CONDITIONS BECOME QUITE UNSTABLE OVER THE LAKE. MAY NEED TO
INDICATE SUB 1SM VSBY IN MODERATE/HEAVY PRECIPITATION AS DETAILS
BECOME MORE CLEAR. GYY WILL ALSO LIKELY SEE THE STRONGEST WINDS
GIVEN THEIR PROXIMITY TO THE LAKE AND 45+ KT WILL BE POSSIBLE.

WINDS GRADUALLY EASE EARLY THIS EVENING AND LAKE EFFECT MAY BEGIN
TO TRANSITION WESTWARD INTO THE EARLY OVERNIGHT SO MDW AND
POSSIBLY ORD COULD BE IN LINE FOR SOME SNOW SHOWERS BUT CONDITIONS
WILL BECOME LESS FAVORABLE WITH TIME INTO SATURDAY MORNING. WILL
CONTINUE WITH SNOW SHOWER MENTION AT MDW THIS EVENING BUT LEAVE
ORD DRY FOR NOW.

MDB

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

* HIGH CONFIDENCE IN SOME SNOW SHOWERS THIS MORNING...MEDIUM
  CONFIDENCE IN DURATION...LOW CONFIDENCE IN IF BRIEF IFR VSBY
  WILL OCCUR.

* HIGH CONFIDENCE IN NORTHWEST WINDS TURNING NORTH AND IN GUSTS
  REACHING 35-37 KT...MEDIUM CONFIDENCE THAT SOME 40 KT GUSTS WILL
  OCCUR BUT LOW CONFIDENCE IN FREQUENCY AND BEST TIMING.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC MVFR CIGS THROUGH THE
  MORNING.

* LOW CONFIDENCE IN LAKE EFFECT SNOW SHOWER POTENTIAL THIS EVENING
  AT ORD...MEDIUM CONFIDENCE AT MDW.

MDB

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

* SATURDAY...DRY/VFR. NORTHEAST WINDS 10-15 KT.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...HIGH WIND WARNING...ILZ014...10 AM FRIDAY TO 6 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022-ILZ023-
     ILZ033...8 AM FRIDAY TO 7 PM FRIDAY.

IN...HIGH WIND WARNING...INZ001-INZ002...10 AM FRIDAY TO 6 PM FRIDAY.

     LAKE EFFECT SNOW ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...INZ010-INZ011-INZ019...8 AM FRIDAY TO 7 PM
     FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

&&

$$

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

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000
FXUS63 KLOT 310826
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
326 AM CDT FRI OCT 31 2014

.SHORT TERM...
326 AM CDT

THROUGH SATURDAY...

ACTIVE WEATHER ON TAP THE NEXT 24 HOURS AS COMPACT AND DEEP UPPER
LOW DIVES SOUTH ACROSS THE REGION DRAGGING UNSEASONABLY COLD
AIR...BOTH AT THE SURFACE AND ALOFT...INTO THE REGION TODAY INTO
TONIGHT. EARLY THIS MORNING SURFACE ANALYSIS SHOWS A RATHER DIFFUSE
COLD FRONT MOVING ACROSS THE REGION WITH STRONG COLD ADVECTION
RESULTING IN A HEALTHY TEMP DROP PRIOR TO SUNRISE OVER NORTHERN CWA
AND SHORTLY AFTERWARD SOUTHEAST. STRONG NNW WINDS WILL ALSO ARRIVE
WITH THE COLD AIR AND CONTINUE INTO THIS EVENING RESULTING IN
TEMPERATURES LARGELY REMAINING FAIRLY STEADY THROUGH THE AFTERNOON.

COMPACT VORT AND REALLY THE HEART OF THE UPPER LOW SHOWS UP NICELY
OVER NORTHERN WISCONSIN EARLY THIS MORNING AND IS DIVING SSE TOWARD
THE AREA. THE COMBINATION OF ASCENT WITH THIS FEATURE AND STEEP
LAPSE RATES ARE RESULTING IN SCATTERED BUT FAIRLY VIGOROUS SNOW
SHOWERS OVER NORTHERN AND CENTRAL WISCONSIN AND WOULD FULLY
ANTICIPATE THESE TO MAINTAIN THEMSELVES AND MOVE ACROSS MAINLY THE
EASTERN CWA THIS MORNING. TEMPS WILL PROBABLY BE TOO WARM FOR MUCH
IF ANY ACCUMULATION...BUT SOME OF THE SNOW SHOWERS COULD BE BRIEFLY
VIGOROUS AND KNOCK VSBY DOWN TO BELOW 1SM. AS THE VORT CONTINUE
SOUTHEAST LOOK FOR THE NON-LAKE DRIVEN PRECIP TO END BY MID MORNING
NORTHERN CWA AND LATE MORNING SOUTHEAST CWA.

THE VORT WILL HERALD THE ARRIVAL OF THE COLDEST AIR ALOFT AND
RESULTANT STRONGEST INSTABILITY OVER THE LAKE AS H5 TEMPS DROP TO
-33C AND H7 TEMPS BELOW -15C. THERMODYNAMIC PROFILES OVER THE LAKE
BEHIND THIS VORT BECOME EXPLOSIVELY UNSTABLE THIS MORNING REMAIN SO
THROUGH THE DAY. LAKE EFFECT SHOULD GET GOING IN ERNEST BEHIND THIS
VORT AND CONTINUE TO SOME DEGREE INTO SATURDAY MORNING. FORECAST
LAKE INDUCED EQUILIBRIUM LEVELS TODAY APPROACH 20K FT...NEAR THE
-30C LEVEL...WHICH IS MORE THAN COLD ENOUGH TO SUPPORT LIGHTNING
GIVEN THE HIGH LIKELIHOOD OF MIXED PHASE HYDROMETEORS (SUPERCOOLED
DROPLETS AND ICE) IN THE CLOUDS WITHIN STRONG UPDRAFTS. NEAR SURFACE
TEMPS OVER THE LAKE AND WITHIN A FEW MILES OF THE LAKE SHORE MAY BE
WARM ENOUGH TO SUPPORT P-TYPE FLUCTUATING BETWEEN RAIN...RAIN/SNOW
MIX...AND ALL SNOW. LAKE EFFECT PRECIP FARTHER INLAND STANDS A MUCH
BETTER CHANCE OF REMAINING ALL OR MOSTLY SNOW.

ONE OF THE BIGGER UNCERTAINTIES FOR TODAY IS HOW ORGANIZED THE LAKE
EFFECT WILL BECOME AND WHETHER IT WILL BE MULTIPLE BANDS OR A SINGLE
INTENSE BAND. GIVEN THE VERY STRONG BOUNDARY LAYER WINDS AND LESS
THAN IDEAL TIME OF DAY AM CONCERNED THAT THE LAKE EFFECT PRECIP
COULD BE SOMEWHAT UNORGANIZED/SCATTERED IN NATURE WITH MULTIPLE
BANDS DURING THE DAY WHICH WILL BE THE TIME OF STRONG TO EXTREME
INSTABILITY. IF A MORE ORGANIZED DOMINANT SINGLE BAND DOES
FORM...THE STRONG FLOW AND INSTABILITY WELL INLAND WOULD SUPPORT
INTENSE PRECIP RATES MAKING IT WELL INLAND THIS AFTERNOON WHERE
P-TYPE WOULD LIKELY BE MOSTLY SNOW...POSSIBLY MODERATE TO HEAVY
SNOW. IF SNOW FALLS HEAVY ENOUGH THEN THE WARM GROUND TEMPS WOULD
BECOME MORE OF A MOOT POINT WITH RAPID ACCUMULATIONS OF HEAVY/WET
SNOW...ESPECIALLY ON GRASSY SURFACES WHERE ISOLATED LOCATIONS COULD
SEE A QUICK SEVERAL INCHES OF SNOW. THE MOST LIKELY SCENARIO WOULD
APPEAR TO BE SOMEWHAT LESS ORGANIZED BANDS OF SNOW SHOWERS RESULTING
IN ONLY MINOR ACCUMS ON GRASSY SURFACES IN SPOTS TODAY. THE WIND
WILL BE WHIPPING THE SNOW AROUND REGARDLESS SO UNDERNEATH ANY LAKE
EFFECT SNOW CONDITIONS WILL BE PRETTY MISERABLE EVEN THOUGH IT IS
UNLIKELY TO ACCUMULATE ON ROADS/SIDEWALKS TODAY. LAKE AND PORTER
COUNTY LOOK TO BE GROUND ZERO FOR THE LAKE EFFECT TODAY WITH THE
PRECIP LIKELY MAKING IT WELL INLAND TO JASPER AND NEWTON COUNTIES.
SOME HIGH RES GUIDANCE DOES CLIP SE COOK AND EASTERN WILL WITH LAKE
EFFECT PRECIP TODAY WHICH ISNT OUT OF THE QUESTION AND HAVE
MAINTAINED LOW POPS THERE.

THIS EVENING THE LOW LEVEL FLOW WILL GRADUALLY VEER AND SEND THE
LAKE EFFECT MORE INTO EASTERN COOK/EASTERN WILL/WESTERN LAKE IN (AND
EVEN POINTS SOUTH. BY THIS EVENING THE BOUNDARY LAYER FLOW WILL BE
WEAKENING AND THE TEMPS OUTSIDE OF THE LAKE INFLUENCED AREAS
DROPPING WHICH WOULD BOTH TEND TO FAVOR A TRANSITION TO A MORE
ORGANIZED DOMINANT SINGLE LAKE EFFECT BAND. MY BEST GUESS IS THAT
THE TIME WINDOW FOR THE HIGHEST PROBABILITY OF A DOMINANT LAKE
EFFECT BAND WITH POTENTIAL FOR HEAVY SNOW IS BETWEEN 23Z AND ABOUT
04Z. DURING THIS TIME PERIOD THE INSTABILITY (WHILE LESS THAN
EARLIER IN THE DAY) WILL STILL BE STRONG WITH INVERSION HEIGHTS
AROUND 10K FT AND LAKE-850 DELTA T VALUES >20C. DOES APPEARS A
PERIOD OF HEAVY SNOW COULD OCCUR IN EASTERN/SOUTHEASTERN COOK AND
EASTERN WILL COUNTIES EARLY THIS EVENING...BUT GIVEN THE LOW
CONFIDENCE OPTED NOT TO EXPAND THE WINTER WX HEADLINES AT THIS TIME
AND INSTEAD WILL ALLOW DAY SHIFT TO MONITOR MESOSCALE TRENDS. BY
LATER THIS EVENING INTO THE OVERNIGHT HOURS THE LAKE EFFECT
PARAMETERS WILL CONTINUE TO BECOME LESS FAVORABLE AND THE INTENSITY
OF THE LAKE EFFECT PRECIP SHOULD BEGIN TO WIND DOWN LATE TONIGHT AND
EVENTUALLY END SATURDAY. HAVE EXTENDED THE HIGHER POPS LATER IN TIME
AS LAKE EFFECT RARELY WINDS DOWN AS QUICKLY AS MODEL PROGGED
PARAMETERS SUGGEST IT WILL. WORTH NOTING THAT BY LATE EVENING AND
THROUGH SAT MORNING THE CONVECTIVE CLOUD TOP TEMPS DROP BELOW -12C
MEANING THE LIKELIHOOD OF CLOUDS CONTAINING ICE NUCLEI FOR SNOW WILL
BE LOW...SO DESPITE LOWER TEMPS IN THE BOUNDARY LAYER HAVE
TRANSITIONED P-TYPE BACK TO RAIN OR SNOW LATE TONIGHT AND SAT
MORNING.

FINALLY...HIGH WINDS WILL BE THE OTHER CONCERN TODAY. PLAN TO
MAINTAIN WIND ADVISORY AS IS THOUGH CONFIDENCE IN INLAND LOCATIONS
REACHING ADVISORY CRITERIA IS NOT THAT HIGH...BUT WITH GUSTS TO AT
LEAST 40 MPH A GOOD BET NOTHING WOULD BE GAINED FROM MAKING ANY
CHANGES TO THE HEADLINES. THE STORM WARNING FOR THE LAKE LOOKS
LIKELY TO VERIFY WITH 40 MPH SUSTAINED AND POSSIBLY GUSTS TO 58 MPH
LIKELY ALONG THE LAKE FRONT TODAY AND REALLY NOT COMFORTABLE NOT
HAVING A WARNING WITH THE POTENTIAL FOR DAMAGING WINDS ALONG THE
LAKE...SO AM GOING TO UPGRADE TO A HIGH WIND WARNING FOR LAKE SHORE
AREAS.

HEADLINES ARE AN ABSOLUTE MESS AND HEADACHE. WINTER WX ADVISORY
COVERS WIND AND SNOW...BUT IN ORDER TO GO WITH WARNING FOR WIND
ALONG THE LAKE FRONT IN INDIANA WOULD NEED TO UPGRADE TO A WINTER
STORM WARNING WHICH REALLY DOESNT SEEM TO BE THE BEST PRODUCT. AFTER
MUCH HEMMING AND HAWING AND INTERNAL COORDINATION HAVE OPTED TO
CHANGE THE WINTER WX ADV TO A LAKE EFFECT SNOW ADVISORY AND ISSUE A
WIND ADVISORY FOR JASPER AND NEWTON AND A HIGH WIND WARNING FOR LAKE
SHORE AREAS OF COOK...PORTER...AND LAKE IN. MAY NEED TO REPLACE THE
HIGH WIND WARNING WITH A WIND ADVISORY BY EARLY EVENING FOR

IZZI

&&

.LONG TERM...
325 AM CDT

SATURDAY NIGHT THROUGH THURSDAY...

MUCH...MUCH QUIETER SUNDAY AND MONDAY WITH MODERATING TEMPS. SLOW
MOVING FRONT COULD BRING A SOMEWHAT PROLONGED PERIOD OF RAIN/SHOWERS
MONDAY NIGHT THOUGH TUESDAY NIGHT. GENERALLY SEASONABLE TEMPS
EXPECTED THROUGH THE EXTENDED.

IZZI

&&

.AVIATION...

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

* INTERMITTENT RAIN SHOWERS OVERNIGHT.

* FEW HOUR PERIOD OF SNOW SHOWERS AFTER DAYBREAK.

* NORTHWEST WINDS SHIFTING NORTH AFTER DAYBREAK WITH GUSTS
  INCREASING TO 35-40 KT. NOT CLEAR ON FREQUENCY OF 40 KT GUSTS.

* PERIODIC MVFR CIGS OVERNIGHT THROUGH THE MORNING.

* LAKE EFFECT SNOW SHOWERS COULD AFFECT MDW EARLY EVENING.

MDB

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

NUMEROUS FORECAST CONCERNS CONTINUE WITH LOW PRESSURE OVER LAKE
HURON TRACKING SOUTHEAST AND VERY STRONG HIGH PRESSURE OVER THE
NORTHERN PLAINS TRAILING IT. WINDS ARE BEGINNING TO TURN NORTHWEST
WITH A COLD FRONT ENTERING NORTHWEST ILLINOIS AT 06Z AND MOVING
SOUTHEAST. WINDS WILL INCREASE IN SPEED OVER THE NEXT SEVERAL
HOURS. A SERIES OF UPPER DISTURBANCES WILL CROSS THE AREA THROUGH
THE MORNING WITH THE FIRST NOW BRINGING RAIN SHOWERS TO THE
TERMINALS. THE NEXT WILL ARRIVE OVERNIGHT BRINGING INTERMITTENT
SHOWERS WITH A BETTER DEFINED WAVE CROSSING THE AREA AROUND/AFTER
DAYBREAK BRINGING SNOW SHOWERS AS MUCH COLDER AIR ARRIVES. AREAS
OF NORTHERN WISCONSIN ARE SEEING IFR SNOW THIS HOUR BUT THESE
HEAVIER BURSTS ARE EXPECTED TO TRACK TO THE EAST OF THE TERMINALS.
STILL CANNOT RULE OUT A BRIEF HEAVIER BURST OF NON-ACCUMULATING
SNOW AT ORD/MDW/GYY BUT WILL CONTINUE WITH MINIMAL VSBY
RESTRICTION. OTHERWISE EXPECT INTERMITTENT MVFR CIGS TO DEVELOP
WITH QUITE A BIT OF VARIABILITY BASED ON UPSTREAM CONDITIONS.

WINDS FURTHER INCREASE BEHIND THIS SNOW PRODUCING WAVE WITH GUSTS
OF 35-40 KT EXPECTED. IT IS UNCLEAR HOW FREQUENT THAT 40 KT GUSTS
WILL OCCUR BUT AM FAIRLY CONFIDENT THAT THEY WILL. AM THINKING
THAT THERE MAY BE TWO SEPARATE WINDOWS WHERE 40 KT WILL BE MOST
LIKELY...ONE BEING MID/LATE MORNING BEHIND THE SNOW PRODUCING WAVE
AND THE OTHER BEING MID AFTERNOON WHEN SKIES ARE MOST LIKELY TO
SCATTER. WITH OVERALL CONFIDENCE IN 40 KT FREQUENCY ON THE LOW
SIDE WILL CONTINUE WITH PREVIOUS DURATION FOR NOW BUT WILL ATTEMPT
TO REFINE WITH THE NEXT UPDATE IF POSSIBLE.

THE NEXT ISSUE WILL BE LAKE EFFECT PRECIPITATION. GYY LOOKS TO BE
IN LINE FOR LAKE EFFECT RAIN/SNOW AND POSSIBLY PERIODS OF ALL SNOW
FROM LATE MORNING INTO THE EVENING. THUNDER IS ALSO POSSIBLE AS
CONDITIONS BECOME QUITE UNSTABLE OVER THE LAKE. MAY NEED TO
INDICATE SUB 1SM VSBY IN MODERATE/HEAVY PRECIPITATION AS DETAILS
BECOME MORE CLEAR. GYY WILL ALSO LIKELY SEE THE STRONGEST WINDS
GIVEN THEIR PROXIMITY TO THE LAKE AND 45+ KT WILL BE POSSIBLE.

WINDS GRADUALLY EASE EARLY THIS EVENING AND LAKE EFFECT MAY BEGIN
TO TRANSITION WESTWARD INTO THE EARLY OVERNIGHT SO MDW AND
POSSIBLY ORD COULD BE IN LINE FOR SOME SNOW SHOWERS BUT CONDITIONS
WILL BECOME LESS FAVORABLE WITH TIME INTO SATURDAY MORNING. WILL
CONTINUE WITH SNOW SHOWER MENTION AT MDW THIS EVENING BUT LEAVE
ORD DRY FOR NOW.

MDB

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

* HIGH CONFIDENCE IN PRECIP TRENDS THROUGH THE MORNING.

* MEDIUM CONFIDENCE IN SOME SNOW SHOWERS THIS MORNING...LOW
  CONFIDENCE IN DURATION/INTENSITY.

* HIGH CONFIDENCE IN NORTHWEST WINDS TURNING NORTH AND IN GUSTS
  REACHING 35-37 KT...MEDIUM CONFIDENCE THAT SOME 40 KT GUSTS WILL
  OCCUR BUT LOW CONFIDENCE IN FREQUENCY AND BEST TIMING.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC MVFR CIGS OVERNIGHT THROUGH
  THE MORNING.

* LOW CONFIDENCE IN LAKE EFFECT SNOW SHOWER POTENTIAL THIS
  EVENING.

MDB

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

* SATURDAY...DRY/VFR. NORTHEAST WINDS 10-15 KT.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

     STORM WARNING...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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 310801
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
301 AM CDT FRI OCT 31 2014

.UPDATE...
921 PM

MID-EVENING UPDATE...

HAVE MADE SOME ADDITIONAL MINOR REFINEMENTS TO POPS FOR SHOWERS WITH
APPROACHING COLD FRONT TONIGHT. MORE IMPORTANTLY...HAVE BUMPED QPF
AND SNOWFALL AMOUNTS ASSOCIATED WITH LAKE EFFECT PRECIPITATION
EXPECTED FRIDAY AFTERNOON AND EVENING IN NORTHWEST INDIANA.

COLD FRONT CONTINUES TO DEVELOP SOUTHEASTWARD ACROSS IOWA...
MINNESOTA AND SOUTHWEST WISCONSIN THIS EVENING...AS COLD CANADIAN
HIGH PRESSURE EXPANDS SOUTHEAST TOWARD THE REGION. GUSTY WINDS STILL
REMAIN A FEW HOURS AWAY FOR THE LOCAL FORECAST AREA WITH
STRENGTHENING GUSTS MORE SHARPLY FALLING TEMPERATURES AFTER
MIDNIGHT. GENERALLY WEAK RADAR ECHOES NOTED ACROSS THE REGION AS
COLD ADVECTION AND LOW-LEVEL FRONTOGENESIS STRENGTHENS UPSTREAM OF
THE CWA. HIGH-RES GUIDANCE CONTINUES TO DEPICT DEVELOPMENT OF
SCATTERED LIGHT SHOWERS/SPRINKLES AFTER MIDNIGHT AS THE COLDER AIR
SPREADS IN...AND HAVE LARGELY BASED HOURLY POP TRENDS ALONG THESE
TRENDS.

ALL HEADLINES REMAIN UNCHANGED THROUGH THE PERIOD...WITH NO CHANGES
IN EXPECTATIONS OF THE VERY GUSTY WINDS...AND THE RESULTING LARGE
WAVES AND LAKESHORE FLOOD POTENTIAL ALONG LAKE MICHIGAN. BECOMING A
BIT MORE CONCERNED ABOUT POTENTIAL FOR SIGNIFICANT LAKE EFFECT SNOW
OVER NORTHWEST INDIANA FRIDAY AFTERNOON/EVENING...AND EVEN PORTIONS
OF THE IL LAKE SHORE AREAS FRIDAY NIGHT. REALLY IMPRESSIVE
THERMODYNAMIC SET-UP WITH COLD AIR OVER WARM LAKE WATERS AND STRONG
UNIDIRECTIONAL NORTHERLY FETCH OVER THE LAKE. ALLOWING FOR LAKE
SURFACE TEMPS IN THE LOW 50S F...LAKE-850 HPA DELTA T APPROACHES 20
DEG C DURING THE PERIOD AND YIELDS LAKE-INDUCED FORECAST CAPES UP TO
1200 J/KG AND INVERSION LEVELS ABOVE 15 KFT. THE ONLY POTENTIAL
LIMITING FACTOR...AND ITEM OF GREAT UNCERTAINTY...IS THE WARMTH OF
THE WATER/SURFACE WET BULB TEMPS SUPPLIED BY THE LONG FETCH OVER
WARM WATERS. GIVEN STRONG INSTABILITY...WITH GOOD LIKELIHOOD OF
THUNDER...THERMODYNAMIC INSTABILITY MAY WELL BE ABLE TO OVERCOME
WARM LOW LEVELS AND PRODUCE ACCUMULATING WET SNOWFALL. WITH MUCH
UNCERTAINTY REMAINING...HAVE INCREASED QPF/SNOWFALL AMOUNTS SLIGHTLY
ACROSS NORTHWEST INDIANA FRI AFTERNOON/NIGHT TO THE 1-3 INCH
RANGE...AND HAVE INDICATED THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS
IN THE ADVISORY WSW TEXT. IF COLUMN IS ABLE TO COOL SUFFICIENTLY FOR
LONG DURATION +SN/TSSN...COULD BE SEVERAL INCHES MORE IN SOME SPOTS.
IN ADDITION...THOUGH INSTABILITY WEAKENS LATER FRIDAY NIGHT AS WINDS
SHIFT NORTHEAST...EXPECT LESS INTENSE RAIN/SNOW OR ALL SNOW SHOWERS
TO IMPINGE UPON PARTS OF THE ILLINOIS SHORE AND STATELINE AREAS AS
WELL.

RATZER

&&

.SHORT TERM...
332 PM CDT...

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL
IMPULSE WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10
PM THIS EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL
ROUND OF SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE
NIGHT...IN CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE
VICINITY OF THE COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY
PROGRESSIVE AREA OF SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL
ILLINOIS DRYING OUT BY EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE
PROCESSES LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO
-20 LAYER TO RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN
COOK COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS
UNCERTAINTY ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT
BANDING. SOME HAVE HINTED IN A FARTHER WEST BAND...WHICH WOULD
IMPACT MORE OF THE CHICAGO AREA. HOWEVER...I THINK AT THIS POINT
AREAS IN NORTHWEST INDIANA WILL BE MORE FAVORED...WITH THE
LIKELIHOOD OF A NEARLY DUE NORTH BOUNDARY LAYER FLOW SETTING UP OVER
LAKE MICHIGAN. THIS WOULD TEND TO FAVOR BETTER BOUNDARY LAYER
CONVERGENCE ALONG THE SOUTHERN TIP OF LAKE MICHIGAN FRIDAY
AFTERNOON...WHICH SUGGESTS THAT PORTER AND LAKE INDIANA WILL BE MORE
IN LINE WITH THE POTENTIAL HEAVIER PRECIPITATION. DUE TO THE STRONG
WINDS...IT IS ALSO LIKELY THAT THIS LAKE EFFECT PRECIP COULD BE
DRIVEN WELL INLAND ACROSS NORTHWESTERN INDIANA...POSSIBLY IMPACTING
MUCH OF JASPER AND PORTER COUNTIES AS WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION
TO GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

KJB

&&

.LONG TERM...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* INTERMITTENT RAIN SHOWERS OVERNIGHT.

* FEW HOUR PERIOD OF SNOW SHOWERS AFTER DAYBREAK.

* NORTHWEST WINDS SHIFTING NORTH AFTER DAYBREAK WITH GUSTS
  INCREASING TO 35-40 KT. NOT CLEAR ON FREQUENCY OF 40 KT GUSTS.

* PERIODIC MVFR CIGS OVERNIGHT THROUGH THE MORNING.

* LAKE EFFECT SNOW SHOWERS COULD AFFECT MDW EARLY EVENING.

MDB

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

NUMEROUS FORECAST CONCERNS CONTINUE WITH LOW PRESSURE OVER LAKE
HURON TRACKING SOUTHEAST AND VERY STRONG HIGH PRESSURE OVER THE
NORTHERN PLAINS TRAILING IT. WINDS ARE BEGINNING TO TURN NORTHWEST
WITH A COLD FRONT ENTERING NORTHWEST ILLINOIS AT 06Z AND MOVING
SOUTHEAST. WINDS WILL INCREASE IN SPEED OVER THE NEXT SEVERAL
HOURS. A SERIES OF UPPER DISTURBANCES WILL CROSS THE AREA THROUGH
THE MORNING WITH THE FIRST NOW BRINGING RAIN SHOWERS TO THE
TERMINALS. THE NEXT WILL ARRIVE OVERNIGHT BRINGING INTERMITTENT
SHOWERS WITH A BETTER DEFINED WAVE CROSSING THE AREA AROUND/AFTER
DAYBREAK BRINGING SNOW SHOWERS AS MUCH COLDER AIR ARRIVES. AREAS
OF NORTHERN WISCONSIN ARE SEEING IFR SNOW THIS HOUR BUT THESE
HEAVIER BURSTS ARE EXPECTED TO TRACK TO THE EAST OF THE TERMINALS.
STILL CANNOT RULE OUT A BRIEF HEAVIER BURST OF NON-ACCUMULATING
SNOW AT ORD/MDW/GYY BUT WILL CONTINUE WITH MINIMAL VSBY
RESTRICTION. OTHERWISE EXPECT INTERMITTENT MVFR CIGS TO DEVELOP
WITH QUITE A BIT OF VARIABILITY BASED ON UPSTREAM CONDITIONS.

WINDS FURTHER INCREASE BEHIND THIS SNOW PRODUCING WAVE WITH GUSTS
OF 35-40 KT EXPECTED. IT IS UNCLEAR HOW FREQUENT THAT 40 KT GUSTS
WILL OCCUR BUT AM FAIRLY CONFIDENT THAT THEY WILL. AM THINKING
THAT THERE MAY BE TWO SEPARATE WINDOWS WHERE 40 KT WILL BE MOST
LIKELY...ONE BEING MID/LATE MORNING BEHIND THE SNOW PRODUCING WAVE
AND THE OTHER BEING MID AFTERNOON WHEN SKIES ARE MOST LIKELY TO
SCATTER. WITH OVERALL CONFIDENCE IN 40 KT FREQUENCY ON THE LOW
SIDE WILL CONTINUE WITH PREVIOUS DURATION FOR NOW BUT WILL ATTEMPT
TO REFINE WITH THE NEXT UPDATE IF POSSIBLE.

THE NEXT ISSUE WILL BE LAKE EFFECT PRECIPITATION. GYY LOOKS TO BE
IN LINE FOR LAKE EFFECT RAIN/SNOW AND POSSIBLY PERIODS OF ALL SNOW
FROM LATE MORNING INTO THE EVENING. THUNDER IS ALSO POSSIBLE AS
CONDITIONS BECOME QUITE UNSTABLE OVER THE LAKE. MAY NEED TO
INDICATE SUB 1SM VSBY IN MODERATE/HEAVY PRECIPITATION AS DETAILS
BECOME MORE CLEAR. GYY WILL ALSO LIKELY SEE THE STRONGEST WINDS
GIVEN THEIR PROXIMITY TO THE LAKE AND 45+ KT WILL BE POSSIBLE.

WINDS GRADUALLY EASE EARLY THIS EVENING AND LAKE EFFECT MAY BEGIN
TO TRANSITION WESTWARD INTO THE EARLY OVERNIGHT SO MDW AND
POSSIBLY ORD COULD BE IN LINE FOR SOME SNOW SHOWERS BUT CONDITIONS
WILL BECOME LESS FAVORABLE WITH TIME INTO SATURDAY MORNING. WILL
CONTINUE WITH SNOW SHOWER MENTION AT MDW THIS EVENING BUT LEAVE
ORD DRY FOR NOW.

MDB

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

* HIGH CONFIDENCE IN PRECIP TRENDS THROUGH THE MORNING.

* MEDIUM CONFIDENCE IN SOME SNOW SHOWERS THIS MORNING...LOW
  CONFIDENCE IN DURATION/INTENSITY.

* HIGH CONFIDENCE IN NORTHWEST WINDS TURNING NORTH AND IN GUSTS
  REACHING 35-37 KT...MEDIUM CONFIDENCE THAT SOME 40 KT GUSTS WILL
  OCCUR BUT LOW CONFIDENCE IN FREQUENCY AND BEST TIMING.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC MVFR CIGS OVERNIGHT THROUGH
  THE MORNING.

* LOW CONFIDENCE IN LAKE EFFECT SNOW SHOWER POTENTIAL THIS
  EVENING.

MDB

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

* SATURDAY...DRY/VFR. NORTHEAST WINDS 10-15 KT.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

&&

.MARINE...
256 AM CDT

A MAJOR WIND EVENT CONTINUES TO TAKE SHAPE FOR LAKE MICHIGAN EARLY
THIS MORNING. FAIRLY BROAD LOW PRESSURE OVER LAKE HURON WILL TRACK
SOUTHEAST TO LAKE ERIE BY MIDDAY THEN CONTINUE TO THE CAROLINA COAST
TONIGHT AND MERGE WITH DEVELOPING LOW PRESSURE. VERY STRONG HIGH
PRESSURE STRETCHED ACROSS THE NORTHERN PLAINS INTO CENTRAL CANADA IS
THE KEY TO THE RAPIDLY INCREASING WINDS THAT ARE NOW REACHING THE
NORTHERN PORTION OF THE LAKE. THE PRESSURE GRADIENT WILL QUICKLY
INCREASE ACROSS THE LAKE INTO MID MORNING AS A COLD FRONT SWEEPS
ACROSS ALLOWING MUCH COLDER AIR TO SPREAD DOWN THE LAKE. NORTH WINDS
WILL LIKELY INCREASE TO STORM FORCE AROUND 50 KT FOR MOST OF THE
LAKE WITH THE FAR NORTHERN SECTION HOLDING AT GALES...THOUGH A FEW
50 KT GUSTS COULD OCCUR THIS MORNING. MAY SEE SOME 55 KT GUSTS AT
TIMES ACROSS THE SOUTH HALF OF THE LAKE...ESPECIALLY LATE THIS
MORNING INTO MIDDAY. THIS RAPID INCREASE IN WINDS AND STRONG
MIXING OVER THE LAKE WILL ALLOW FOR A RAPID BUILDING OF WAVES
THROUGH THE MORNING TO AROUND 20 FEET BY EARLY/MID AFTERNOON
ACROSS THE CENTRAL AND SOUTHERN PART OF THE LAKE. WILL CONTINUE
WITH 18-23 FT PREVAILING WAVES IN THE FORECAST FOR THESE AREAS.
WINDS WILL BEGIN TO EASE THIS EVENING AND TREND A BIT
NORTHEASTERLY. SHOULD SEE WINDS FALL BELOW GALE FORCE OVERNIGHT
BUT WINDS WILL BE SLOW TO DIMINISH SIGNIFICANTLY THROUGH MIDDAY
SATURDAY SO WAVES WILL LIKELY BE SLOW TO FALL AS WELL. WILL LEAVE
EXISTING GALE AND STORM WARNINGS AS-IS.

THE HIGH WILL PASS OVER THE LAKE SATURDAY EVENING THROUGH SUNDAY
KEEPING WINDS LIGHT BUT SOUTH TO SOUTHWEST WINDS WILL INCREASE
THROUGH THE DAY SUNDAY AND MAY PUSH 30 KT LATE SUNDAY
AFTERNOON/EVENING AS LOW PRESSURE TRACKS NORTHEAST ACROSS THE
NORTHERN PLAINS. SOUTHWEST WINDS WILL REMAIN STRONG THROUGH MONDAY
NIGHT THEN LET UP NORTH AS LOW PRESSURE TRACKS FROM THE SOUTHERN
PLAINS ACROSS NORTHERN LAKE MICHIGAN...WHILE THE SOUTH SEES BREEZY
CONDITIONS CONTINUE. WINDS TURN WESTERLY LATER TUESDAY AND
DIMINISH AS HIGH PRESSURE RIDGING EXTENDS ACROSS THE AREA.

MDB

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 4 AM SATURDAY.

     STORM WARNING...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL 7 PM
     FRIDAY.

&&

$$

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000
FXUS63 KLOT 310613
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
113 AM CDT FRI OCT 31 2014

.UPDATE...
921 PM

MID-EVENING UPDATE...

HAVE MADE SOME ADDITIONAL MINOR REFINEMENTS TO POPS FOR SHOWERS WITH
APPROACHING COLD FRONT TONIGHT. MORE IMPORTANTLY...HAVE BUMPED QPF
AND SNOWFALL AMOUNTS ASSOCIATED WITH LAKE EFFECT PRECIPITATION
EXPECTED FRIDAY AFTERNOON AND EVENING IN NORTHWEST INDIANA.

COLD FRONT CONTINUES TO DEVELOP SOUTHEASTWARD ACROSS IOWA...
MINNESOTA AND SOUTHWEST WISCONSIN THIS EVENING...AS COLD CANADIAN
HIGH PRESSURE EXPANDS SOUTHEAST TOWARD THE REGION. GUSTY WINDS STILL
REMAIN A FEW HOURS AWAY FOR THE LOCAL FORECAST AREA WITH
STRENGTHENING GUSTS MORE SHARPLY FALLING TEMPERATURES AFTER
MIDNIGHT. GENERALLY WEAK RADAR ECHOES NOTED ACROSS THE REGION AS
COLD ADVECTION AND LOW-LEVEL FRONTOGENESIS STRENGTHENS UPSTREAM OF
THE CWA. HIGH-RES GUIDANCE CONTINUES TO DEPICT DEVELOPMENT OF
SCATTERED LIGHT SHOWERS/SPRINKLES AFTER MIDNIGHT AS THE COLDER AIR
SPREADS IN...AND HAVE LARGELY BASED HOURLY POP TRENDS ALONG THESE
TRENDS.

ALL HEADLINES REMAIN UNCHANGED THROUGH THE PERIOD...WITH NO CHANGES
IN EXPECTATIONS OF THE VERY GUSTY WINDS...AND THE RESULTING LARGE
WAVES AND LAKESHORE FLOOD POTENTIAL ALONG LAKE MICHIGAN. BECOMING A
BIT MORE CONCERNED ABOUT POTENTIAL FOR SIGNIFICANT LAKE EFFECT SNOW
OVER NORTHWEST INDIANA FRIDAY AFTERNOON/EVENING...AND EVEN PORTIONS
OF THE IL LAKE SHORE AREAS FRIDAY NIGHT. REALLY IMPRESSIVE
THERMODYNAMIC SET-UP WITH COLD AIR OVER WARM LAKE WATERS AND STRONG
UNIDIRECTIONAL NORTHERLY FETCH OVER THE LAKE. ALLOWING FOR LAKE
SURFACE TEMPS IN THE LOW 50S F...LAKE-850 HPA DELTA T APPROACHES 20
DEG C DURING THE PERIOD AND YIELDS LAKE-INDUCED FORECAST CAPES UP TO
1200 J/KG AND INVERSION LEVELS ABOVE 15 KFT. THE ONLY POTENTIAL
LIMITING FACTOR...AND ITEM OF GREAT UNCERTAINTY...IS THE WARMTH OF
THE WATER/SURFACE WET BULB TEMPS SUPPLIED BY THE LONG FETCH OVER
WARM WATERS. GIVEN STRONG INSTABILITY...WITH GOOD LIKELIHOOD OF
THUNDER...THERMODYNAMIC INSTABILITY MAY WELL BE ABLE TO OVERCOME
WARM LOW LEVELS AND PRODUCE ACCUMULATING WET SNOWFALL. WITH MUCH
UNCERTAINTY REMAINING...HAVE INCREASED QPF/SNOWFALL AMOUNTS SLIGHTLY
ACROSS NORTHWEST INDIANA FRI AFTERNOON/NIGHT TO THE 1-3 INCH
RANGE...AND HAVE INDICATED THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS
IN THE ADVISORY WSW TEXT. IF COLUMN IS ABLE TO COOL SUFFICIENTLY FOR
LONG DURATION +SN/TSSN...COULD BE SEVERAL INCHES MORE IN SOME SPOTS.
IN ADDITION...THOUGH INSTABILITY WEAKENS LATER FRIDAY NIGHT AS WINDS
SHIFT NORTHEAST...EXPECT LESS INTENSE RAIN/SNOW OR ALL SNOW SHOWERS
TO IMPINGE UPON PARTS OF THE ILLINOIS SHORE AND STATELINE AREAS AS
WELL.

RATZER

&&

.SHORT TERM...
332 PM CDT...

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL
IMPULSE WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10
PM THIS EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL
ROUND OF SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE
NIGHT...IN CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE
VICINITY OF THE COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY
PROGRESSIVE AREA OF SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL
ILLINOIS DRYING OUT BY EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE
PROCESSES LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO
-20 LAYER TO RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN
COOK COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS
UNCERTAINTY ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT
BANDING. SOME HAVE HINTED IN A FARTHER WEST BAND...WHICH WOULD
IMPACT MORE OF THE CHICAGO AREA. HOWEVER...I THINK AT THIS POINT
AREAS IN NORTHWEST INDIANA WILL BE MORE FAVORED...WITH THE
LIKELIHOOD OF A NEARLY DUE NORTH BOUNDARY LAYER FLOW SETTING UP OVER
LAKE MICHIGAN. THIS WOULD TEND TO FAVOR BETTER BOUNDARY LAYER
CONVERGENCE ALONG THE SOUTHERN TIP OF LAKE MICHIGAN FRIDAY
AFTERNOON...WHICH SUGGESTS THAT PORTER AND LAKE INDIANA WILL BE MORE
IN LINE WITH THE POTENTIAL HEAVIER PRECIPITATION. DUE TO THE STRONG
WINDS...IT IS ALSO LIKELY THAT THIS LAKE EFFECT PRECIP COULD BE
DRIVEN WELL INLAND ACROSS NORTHWESTERN INDIANA...POSSIBLY IMPACTING
MUCH OF JASPER AND PORTER COUNTIES AS WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION
TO GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

KJB

&&

.LONG TERM...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* INTERMITTENT RAIN SHOWERS OVERNIGHT.

* FEW HOUR PERIOD OF SNOW SHOWERS AFTER DAYBREAK.

* NORTHWEST WINDS SHIFTING NORTH AFTER DAYBREAK WITH GUSTS
  INCREASING TO 35-40 KT. NOT CLEAR ON FREQUENCY OF 40 KT GUSTS.

* PERIODIC MVFR CIGS OVERNIGHT THROUGH THE MORNING.

* LAKE EFFECT SNOW SHOWERS COULD AFFECT MDW EARLY EVENING.

MDB

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

NUMEROUS FORECAST CONCERNS CONTINUE WITH LOW PRESSURE OVER LAKE
HURON TRACKING SOUTHEAST AND VERY STRONG HIGH PRESSURE OVER THE
NORTHERN PLAINS TRAILING IT. WINDS ARE BEGINNING TO TURN NORTHWEST
WITH A COLD FRONT ENTERING NORTHWEST ILLINOIS AT 06Z AND MOVING
SOUTHEAST. WINDS WILL INCREASE IN SPEED OVER THE NEXT SEVERAL
HOURS. A SERIES OF UPPER DISTURBANCES WILL CROSS THE AREA THROUGH
THE MORNING WITH THE FIRST NOW BRINGING RAIN SHOWERS TO THE
TERMINALS. THE NEXT WILL ARRIVE OVERNIGHT BRINGING INTERMITTENT
SHOWERS WITH A BETTER DEFINED WAVE CROSSING THE AREA AROUND/AFTER
DAYBREAK BRINGING SNOW SHOWERS AS MUCH COLDER AIR ARRIVES. AREAS
OF NORTHERN WISCONSIN ARE SEEING IFR SNOW THIS HOUR BUT THESE
HEAVIER BURSTS ARE EXPECTED TO TRACK TO THE EAST OF THE TERMINALS.
STILL CANNOT RULE OUT A BRIEF HEAVIER BURST OF NON-ACCUMULATING
SNOW AT ORD/MDW/GYY BUT WILL CONTINUE WITH MINIMAL VSBY
RESTRICTION. OTHERWISE EXPECT INTERMITTENT MVFR CIGS TO DEVELOP
WITH QUITE A BIT OF VARIABILITY BASED ON UPSTREAM CONDITIONS.

WINDS FURTHER INCREASE BEHIND THIS SNOW PRODUCING WAVE WITH GUSTS
OF 35-40 KT EXPECTED. IT IS UNCLEAR HOW FREQUENT THAT 40 KT GUSTS
WILL OCCUR BUT AM FAIRLY CONFIDENT THAT THEY WILL. AM THINKING
THAT THERE MAY BE TWO SEPARATE WINDOWS WHERE 40 KT WILL BE MOST
LIKELY...ONE BEING MID/LATE MORNING BEHIND THE SNOW PRODUCING WAVE
AND THE OTHER BEING MID AFTERNOON WHEN SKIES ARE MOST LIKELY TO
SCATTER. WITH OVERALL CONFIDENCE IN 40 KT FREQUENCY ON THE LOW
SIDE WILL CONTINUE WITH PREVIOUS DURATION FOR NOW BUT WILL ATTEMPT
TO REFINE WITH THE NEXT UPDATE IF POSSIBLE.

THE NEXT ISSUE WILL BE LAKE EFFECT PRECIPITATION. GYY LOOKS TO BE
IN LINE FOR LAKE EFFECT RAIN/SNOW AND POSSIBLY PERIODS OF ALL SNOW
FROM LATE MORNING INTO THE EVENING. THUNDER IS ALSO POSSIBLE AS
CONDITIONS BECOME QUITE UNSTABLE OVER THE LAKE. MAY NEED TO
INDICATE SUB 1SM VSBY IN MODERATE/HEAVY PRECIPITATION AS DETAILS
BECOME MORE CLEAR. GYY WILL ALSO LIKELY SEE THE STRONGEST WINDS
GIVEN THEIR PROXIMITY TO THE LAKE AND 45+ KT WILL BE POSSIBLE.

WINDS GRADUALLY EASE EARLY THIS EVENING AND LAKE EFFECT MAY BEGIN
TO TRANSITION WESTWARD INTO THE EARLY OVERNIGHT SO MDW AND
POSSIBLY ORD COULD BE IN LINE FOR SOME SNOW SHOWERS BUT CONDITIONS
WILL BECOME LESS FAVORABLE WITH TIME INTO SATURDAY MORNING. WILL
CONTINUE WITH SNOW SHOWER MENTION AT MDW THIS EVENING BUT LEAVE
ORD DRY FOR NOW.

MDB


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

* HIGH CONFIDENCE IN PRECIP TRENDS THROUGH THE MORNING.

* MEDIUM CONFIDENCE IN SOME SNOW SHOWERS THIS MORNING...LOW
  CONFIDENCE IN DURATION/INTENSITY.

* HIGH CONFIDENCE IN NORTHWEST WINDS TURNING NORTH AND IN GUSTS
  REACHING 35-37 KT...MEDIUM CONFIDENCE THAT SOME 40 KT GUSTS WILL
  OCCUR BUT LOW CONFIDENCE IN FREQUENCY AND BEST TIMING.

* MEDIUM-HIGH CONFIDENCE IN PERIODIC MVFR CIGS OVERNIGHT THROUGH
  THE MORNING.

* LOW CONFIDENCE IN LAKE EFFECT SNOW SHOWER POTENTIAL THIS
  EVENING.

MDB

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

* SATURDAY...DRY/VFR. NORTHEAST WINDS 10-15 KT.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878 UNTIL 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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000
FXUS63 KLOT 310304
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1004 PM CDT THU OCT 30 2014

.UPDATE...
921 PM

MID-EVENING UPDATE...

HAVE MADE SOME ADDITIONAL MINOR REFINEMENTS TO POPS FOR SHOWERS WITH
APPROACHING COLD FRONT TONIGHT. MORE IMPORTANTLY...HAVE BUMPED QPF
AND SNOWFALL AMOUNTS ASSOCIATED WITH LAKE EFFECT PRECIPITATION
EXPECTED FRIDAY AFTERNOON AND EVENING IN NORTHWEST INDIANA.

COLD FRONT CONTINUES TO DEVELOP SOUTHEASTWARD ACROSS IOWA...
MINNESOTA AND SOUTHWEST WISCONSIN THIS EVENING...AS COLD CANADIAN
HIGH PRESSURE EXPANDS SOUTHEAST TOWARD THE REGION. GUSTY WINDS STILL
REMAIN A FEW HOURS AWAY FOR THE LOCAL FORECAST AREA WITH
STRENGTHENING GUSTS MORE SHARPLY FALLING TEMPERATURES AFTER
MIDNIGHT. GENERALLY WEAK RADAR ECHOES NOTED ACROSS THE REGION AS
COLD ADVECTION AND LOW-LEVEL FRONTOGENESIS STRENGTHENS UPSTREAM OF
THE CWA. HIGH-RES GUIDANCE CONTINUES TO DEPICT DEVELOPMENT OF
SCATTERED LIGHT SHOWERS/SPRINKLES AFTER MIDNIGHT AS THE COLDER AIR
SPREADS IN...AND HAVE LARGELY BASED HOURLY POP TRENDS ALONG THESE
TRENDS.

ALL HEADLINES REMAIN UNCHANGED THROUGH THE PERIOD...WITH NO CHANGES
IN EXPECTATIONS OF THE VERY GUSTY WINDS...AND THE RESULTING LARGE
WAVES AND LAKESHORE FLOOD POTENTIAL ALONG LAKE MICHIGAN. BECOMING A
BIT MORE CONCERNED ABOUT POTENTIAL FOR SIGNIFICANT LAKE EFFECT SNOW
OVER NORTHWEST INDIANA FRIDAY AFTERNOON/EVENING...AND EVEN PORTIONS
OF THE IL LAKE SHORE AREAS FRIDAY NIGHT. REALLY IMPRESSIVE
THERMODYNAMIC SET-UP WITH COLD AIR OVER WARM LAKE WATERS AND STRONG
UNIDIRECTIONAL NORTHERLY FETCH OVER THE LAKE. ALLOWING FOR LAKE
SURFACE TEMPS IN THE LOW 50S F...LAKE-850 HPA DELTA T APPROACHES 20
DEG C DURING THE PERIOD AND YIELDS LAKE-INDUCED FORECAST CAPES UP TO
1200 J/KG AND INVERSION LEVELS ABOVE 15 KFT. THE ONLY POTENTIAL
LIMITING FACTOR...AND ITEM OF GREAT UNCERTAINTY...IS THE WARMTH OF
THE WATER/SURFACE WET BULB TEMPS SUPPLIED BY THE LONG FETCH OVER
WARM WATERS. GIVEN STRONG INSTABILITY...WITH GOOD LIKELIHOOD OF
THUNDER...THERMODYNAMIC INSTABILITY MAY WELL BE ABLE TO OVERCOME
WARM LOW LEVELS AND PRODUCE ACCUMULATING WET SNOWFALL. WITH MUCH
UNCERTAINTY REMAINING...HAVE INCREASED QPF/SNOWFALL AMOUNTS SLIGHTLY
ACROSS NORTHWEST INDIANA FRI AFTERNOON/NIGHT TO THE 1-3 INCH
RANGE...AND HAVE INDICATED THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS
IN THE ADVISORY WSW TEXT. IF COLUMN IS ABLE TO COOL SUFFICIENTLY FOR
LONG DURATION +SN/TSSN...COULD BE SEVERAL INCHES MORE IN SOME SPOTS.
IN ADDITION...THOUGH INSTABILITY WEAKENS LATER FRIDAY NIGHT AS WINDS
SHIFT NORTHEAST...EXPECT LESS INTENSE RAIN/SNOW OR ALL SNOW SHOWERS
TO IMPINGE UPON PARTS OF THE ILLINOIS SHORE AND STATELINE AREAS AS
WELL.

RATZER

&&

.SHORT TERM...(TONIGHT THROUGH SATURDAY)
332 PM CDT...

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL
IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT
BY EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE
PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN
COOK COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS
UNCERTAINTY ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT
BANDING. SOME HAVE HINTED IN A FARTHER WEST BAND...WHICH WOULD
IMPACT MORE OF THE CHICAGO AREA. HOWEVER...I THINK AT THIS POINT
AREAS IN NORTHWEST INDIANA WILL BE MORE FAVORED...WITH THE
LIKELIHOOD OF A NEARLY DUE NORTH BOUNDARY LAYER FLOW SETTING UP OVER
LAKE MICHIGAN. THIS WOULD TEND TO FAVOR BETTER BOUNDARY LAYER
CONVERGENCE ALONG THE SOUTHERN TIP OF LAKE MICHIGAN FRIDAY
AFTERNOON...WHICH SUGGESTS THAT PORTER AND LAKE INDIANA WILL BE MORE
IN LINE WITH THE POTENTIAL HEAVIER PRECIPITATION. DUE TO THE STRONG
WINDS...IT IS ALSO LIKELY THAT THIS LAKE EFFECT PRECIP COULD BE
DRIVEN WELL INLAND ACROSS NORTHWESTERN INDIANA...POSSIBLY IMPACTING
MUCH OF JASPER AND PORTER COUNTIES AS WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION
TO GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

KJB

&&

.LONG TERM...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* RAIN SHOWERS OVERNIGHT.
* SNOW SHOWERS FRIDAY MORNING AND POSSIBLY LATE FRIDAY AFTERNOON.
* MVFR CIGS OVERNIGHT THRU FRIDAY MORNING.
* STRONG/GUSTY NORTHWEST WINDS OVERNIGHT.
* VERY STRONG/GUSTY NORTHERLY WINDS TO 40 KT FRIDAY. CMS

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

MULTIPLE FORECAST CONCERNS THIS PERIOD. LOW PRESSURE OVER THE
EASTERN U.P. WILL MOVE TO LAKE HURON BY MORNING. A TRAILING COLD
FRONT WILL MOVE ACROSS THE AREA LATE THIS EVENING INTO THE EARLY
MORNING HOURS...SHIFTING WESTERLY WINDS TO THE NORTHWEST WITH
SPEEDS SLOWLY INCREASING. AS COLDER AIR SPREADS ACROSS THE AREA
LATE THIS EVENING AND OVERNIGHT...RAIN SHOWERS ARE EXPECTED TO
DEVELOP...MOSTLY LIKELY RIGHT OVER THE TERMINALS. THERMAL PROFILES
SUGGEST PRECIP SHOULD REMAIN MAINLY RAIN THRU MUCH OF THE NIGHT
AND PERHAPS ONLY LAST A FEW HOURS THOUGH CONFIDENCE ON TIMING IS
LOW ENOUGH TO MAINTAIN VICINITY MENTION.

WINDS CONTINUE TO INCREASE FRIDAY MORNING AS COLDER AIR CONTINUES
TO POUR INTO THE REGION. AS WINDS SHIFT TO THE NORTH MID/LATE
MORNING...THERE WILL BE ANOTHER CHANCE FOR PRECIPITATION...BY THIS
TIME...THERMAL PROFILES ARE COLD ENOUGH FOR AT LEAST A MIX OF RAIN
AND SNOW BUT MAINTAINED SNOW SHOWERS FROM PREVIOUS FORECAST.
CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD ARE LOW...
INCLUDING DURATION AND INTENSITY. AS THIS TIME PERIOD APPROACHES
AND TRENDS EMERGE ON RADAR...A SHORT DURATION TEMPO FOR LOWER
CONDITIONS MAY BE NEEDED.

CIGS SHOULD REMAIN VFR THIS EVENING AND LOWER TO MVFR OVERNIGHT
WITH THE POTENTIAL FOR A SHORT PERIOD OF LOW MVFR POSSIBLE. ONCE
PRECIP ENDS IN THE MORNING...CIGS SHOULD LIFT TO EITHER HIGH MVFR
OR LOW VFR.

WINDS WILL STEADILY INCREASE FROM THE EARLY MORNING THRU THE LATE
MORNING AND TURN NORTHERLY. PREVAILING SPEEDS IN THE MID 20 KT
RANGE LOOK ON TRACK WITH PREVAILING GUSTS INTO THE MID/UPPER 30KT
RANGE WITH THE POTENTIAL FOR GUSTS TO 40KTS IN THE LATE MORNING
AND EARLY AFTERNOON. SPEEDS/GUSTS WILL SLOWLY DIMINISH LATE IN THE
AFTERNOON...ESPECIALLY AT RFD...BUT WINDY CONDITIONS WILL CONTINUE
INTO FRIDAY EVENING.

AS FOR GYY AND LAKE EFFECT...A BAND OF LAKE EFFECT RAIN AND SNOW
IS EXPECTED TO DEVELOP BY MID MORNING AND CONTINUE INTO FRIDAY
EVENING...AFFECTING NORTHWEST INDIANA FOR MUCH OF THE DAY. THIS
PRECIPITATION IS EXPECTED TO BE QUIET INTENSE WITH THUNDER LIKELY.
IF THIS INTENSE PRECIP IS SUFFICIENT ENOUGH TO COOL THE LOWER
LAYERS...THE PRECIP MAY SWITCH OVER TO ALL OR PREDOMINANTLY SNOW.
CONFIDENCE IN HOW LONG THIS MAY PERSIST IS LOW AND MAINTAINED A
RAIN/SNOW MIX AT GYY WITH A PERIOD OF REDUCED VIS/CIGS IN THE
EARLY/MID AFTERNOON. SPECIFICS ARE DIFFICULT FROM THIS DISTANCE
AND CHANGES TO THE GYY FORECAST SHOULD BE EXPECTED.

SOME OF THE GUIDANCE SHOWS THIS LAKE EFFECT PRECIPITATION MOVING
BACK WEST TOWARD ORD/MDW LATE FRIDAY AFTERNOON INTO FRIDAY
EVENING. CONFIDENCE REGARDING THIS TREND IS ALSO LOW. HOWEVER...
THE BAND WILL BE CLOSE ENOUGH TO MDW TO ADD MENTION LATE IN THE
AFTERNOON WITH THIS FORECAST. IF PRECIP IS SNOW AND DOES MAKE IT
TO ORD/MDW...IFR CIGS/VIS ARE CERTAINLY POSSIBLE. CMS

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

* HIGH FOR RAIN SHOWERS OVERNIGHT.
* MEDIUM FOR SNOW SHOWERS FRIDAY MORNING...LOW FOR DURATION/
  INTENSITY.
* LOW FOR SNOW SHOWERS LATE FRIDAY AFTERNOON.
* MEDIUM FOR MVFR CIGS OVERNIGHT/FRIDAY MORNING.
* HIGH FOR WIND SPEEDS/GUSTS/DIRECTION THRU THE PERIOD...MEDIUM
  FOR TIMING/CHANGES. CMS

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

* SATURDAY...DRY/VFR. NORTHEAST WINDS 10-15 KT.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563 UNTIL 10 PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 310221
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
921 PM CDT THU OCT 30 2014

.DISCUSSION...

MID-EVENING UPDATE...

HAVE MADE SOME ADDITIONAL MINOR REFINEMENTS TO POPS FOR SHOWERS WITH
APPROACHING COLD FRONT TONIGHT. MORE IMPORTANTLY...HAVE BUMPED QPF
AND SNOWFALL AMOUNTS ASSOCIATED WITH LAKE EFFECT PRECIPITATION
EXPECTED FRIDAY AFTERNOON AND EVENING IN NORTHWEST INDIANA.

COLD FRONT CONTINUES TO DEVELOP SOUTHEASTWARD ACROSS IOWA...
MINNESOTA AND SOUTHWEST WISCONSIN THIS EVENING...AS COLD CANADIAN
HIGH PRESSURE EXPANDS SOUTHEAST TOWARD THE REGION. GUSTY WINDS STILL
REMAIN A FEW HOURS AWAY FOR THE LOCAL FORECAST AREA WITH
STRENGTHENING GUSTS MORE SHARPLY FALLING TEMPERATURES AFTER
MIDNIGHT. GENERALLY WEAK RADAR ECHOES NOTED ACROSS THE REGION AS
COLD ADVECTION AND LOW-LEVEL FRONTOGENESIS STRENGTHENS UPSTREAM OF
THE CWA. HIGH-RES GUIDANCE CONTINUES TO DEPICT DEVELOPMENT OF
SCATTERED LIGHT SHOWERS/SPRINKLES AFTER MIDNIGHT AS THE COLDER AIR
SPREADS IN...AND HAVE LARGELY BASED HOURLY POP TRENDS ALONG THESE
TRENDS.

ALL HEADLINES REMAIN UNCHANGED THROUGH THE PERIOD...WITH NO CHANGES
IN EXPECTATIONS OF THE VERY GUSTY WINDS...AND THE RESULTING LARGE
WAVES AND LAKESHORE FLOOD POTENTIAL ALONG LAKE MICHIGAN. BECOMING A
BIT MORE CONCERNED ABOUT POTENTIAL FOR SIGNIFICANT LAKE EFFECT SNOW
OVER NORTHWEST INDIANA FRIDAY AFTERNOON/EVENING...AND EVEN PORTIONS
OF THE IL LAKE SHORE AREAS FRIDAY NIGHT. REALLY IMPRESSIVE
THERMODYNAMIC SET-UP WITH COLD AIR OVER WARM LAKE WATERS AND STRONG
UNIDIRECTIONAL NORTHERLY FETCH OVER THE LAKE. ALLOWING FOR LAKE
SURFACE TEMPS IN THE LOW 50S F...LAKE-850 HPA DELTA T APPROACHES 20
DEG C DURING THE PERIOD AND YIELDS LAKE-INDUCED FORECAST CAPES UP TO
1200 J/KG AND INVERSION LEVELS ABOVE 15 KFT. THE ONLY POTENTIAL
LIMITING FACTOR...AND ITEM OF GREAT UNCERTAINTY...IS THE WARMTH OF
THE WATER/SURFACE WET BULB TEMPS SUPPLIED BY THE LONG FETCH OVER
WARM WATERS. GIVEN STRONG INSTABILITY...WITH GOOD LIKELIHOOD OF
THUNDER...THERMODYNAMIC INSTABILITY MAY WELL BE ABLE TO OVERCOME
WARM LOW LEVELS AND PRODUCE ACCUMULATING WET SNOWFALL. WITH MUCH
UNCERTAINTY REMAINING...HAVE INCREASED QPF/SNOWFALL AMOUNTS SLIGHTLY
ACROSS NORTHWEST INDIANA FRI AFTERNOON/NIGHT TO THE 1-3 INCH
RANGE...AND HAVE INDICATED THE POTENTIAL FOR LOCALLY HIGHER AMOUNTS
IN THE ADVISORY WSW TEXT. IF COLUMN IS ABLE TO COOL SUFFICIENTLY FOR
LONG DURATION +SN/TSSN...COULD BE SEVERAL INCHES MORE IN SOME SPOTS.
IN ADDITION...THOUGH INSTABILITY WEAKENS LATER FRIDAY NIGHT AS WINDS
SHIFT NORTHEAST...EXPECT LESS INTENSE RAIN/SNOW OR ALL SNOW SHOWERS
TO IMPINGE UPON PARTS OF THE ILLINOIS SHORE AND STATELINE AREAS AS
WELL.

RATZER

PREVIOUS DISCUSSION FROM 332 PM CDT...

SHORT TERM...TONIGHT THROUGH SATURDAY...
THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL
IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT
BY EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE
PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN
COOK COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS
UNCERTAINTY ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT
BANDING. SOME HAVE HINTED IN A FARTHER WEST BAND...WHICH WOULD
IMPACT MORE OF THE CHICAGO AREA. HOWEVER...I THINK AT THIS POINT
AREAS IN NORTHWEST INDIANA WILL BE MORE FAVORED...WITH THE
LIKELIHOOD OF A NEARLY DUE NORTH BOUNDARY LAYER FLOW SETTING UP OVER
LAKE MICHIGAN. THIS WOULD TEND TO FAVOR BETTER BOUNDARY LAYER
CONVERGENCE ALONG THE SOUTHERN TIP OF LAKE MICHIGAN FRIDAY
AFTERNOON...WHICH SUGGESTS THAT PORTER AND LAKE INDIANA WILL BE MORE
IN LINE WITH THE POTENTIAL HEAVIER PRECIPITATION. DUE TO THE STRONG
WINDS...IT IS ALSO LIKELY THAT THIS LAKE EFFECT PRECIP COULD BE
DRIVEN WELL INLAND ACROSS NORTHWESTERN INDIANA...POSSIBLY IMPACTING
MUCH OF JASPER AND PORTER COUNTIES AS WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION
TO GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

LONG TERM...SUNDAY THROUGH WEDNESDAY...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* RAIN SHOWERS OVERNIGHT.
* SNOW SHOWERS FRIDAY MORNING AND POSSIBLY LATE FRIDAY AFTERNOON.
* MVFR CIGS OVERNIGHT THRU FRIDAY MORNING.
* STRONG/GUSTY NORTHWEST WINDS OVERNIGHT.
* VERY STRONG/GUSTY NORTHERLY WINDS TO 40 KT FRIDAY. CMS

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

MULTIPLE FORECAST CONCERNS THIS PERIOD. LOW PRESSURE OVER THE
EASTERN U.P. WILL MOVE TO LAKE HURON BY MORNING. A TRAILING COLD
FRONT WILL MOVE ACROSS THE AREA LATE THIS EVENING INTO THE EARLY
MORNING HOURS...SHIFTING WESTERLY WINDS TO THE NORTHWEST WITH
SPEEDS SLOWLY INCREASING. AS COLDER AIR SPREADS ACROSS THE AREA
LATE THIS EVENING AND OVERNIGHT...RAIN SHOWERS ARE EXPECTED TO
DEVELOP...MOSTLY LIKELY RIGHT OVER THE TERMINALS. THERMAL PROFILES
SUGGEST PRECIP SHOULD REMAIN MAINLY RAIN THRU MUCH OF THE NIGHT
AND PERHAPS ONLY LAST A FEW HOURS THOUGH CONFIDENCE ON TIMING IS
LOW ENOUGH TO MAINTAIN VICINITY MENTION.

WINDS CONTINUE TO INCREASE FRIDAY MORNING AS COLDER AIR CONTINUES
TO POUR INTO THE REGION. AS WINDS SHIFT TO THE NORTH MID/LATE
MORNING...THERE WILL BE ANOTHER CHANCE FOR PRECIPITATION...BY THIS
TIME...THERMAL PROFILES ARE COLD ENOUGH FOR AT LEAST A MIX OF RAIN
AND SNOW BUT MAINTAINED SNOW SHOWERS FROM PREVIOUS FORECAST.
CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD ARE LOW...
INCLUDING DURATION AND INTENSITY. AS THIS TIME PERIOD APPROACHES
AND TRENDS EMERGE ON RADAR...A SHORT DURATION TEMPO FOR LOWER
CONDITIONS MAY BE NEEDED.

CIGS SHOULD REMAIN VFR THIS EVENING AND LOWER TO MVFR OVERNIGHT
WITH THE POTENTIAL FOR A SHORT PERIOD OF LOW MVFR POSSIBLE. ONCE
PRECIP ENDS IN THE MORNING...CIGS SHOULD LIFT TO EITHER HIGH MVFR
OR LOW VFR.

WINDS WILL STEADILY INCREASE FROM THE EARLY MORNING THRU THE LATE
MORNING AND TURN NORTHERLY. PREVAILING SPEEDS IN THE MID 20 KT
RANGE LOOK ON TRACK WITH PREVAILING GUSTS INTO THE MID/UPPER 30KT
RANGE WITH THE POTENTIAL FOR GUSTS TO 40KTS IN THE LATE MORNING
AND EARLY AFTERNOON. SPEEDS/GUSTS WILL SLOWLY DIMINISH LATE IN THE
AFTERNOON...ESPECIALLY AT RFD...BUT WINDY CONDITIONS WILL CONTINUE
INTO FRIDAY EVENING.

AS FOR GYY AND LAKE EFFECT...A BAND OF LAKE EFFECT RAIN AND SNOW
IS EXPECTED TO DEVELOP BY MID MORNING AND CONTINUE INTO FRIDAY
EVENING...AFFECTING NORTHWEST INDIANA FOR MUCH OF THE DAY. THIS
PRECIPITATION IS EXPECTED TO BE QUIET INTENSE WITH THUNDER LIKELY.
IF THIS INTENSE PRECIP IS SUFFICIENT ENOUGH TO COOL THE LOWER
LAYERS...THE PRECIP MAY SWITCH OVER TO ALL OR PREDOMINANTLY SNOW.
CONFIDENCE IN HOW LONG THIS MAY PERSIST IS LOW AND MAINTAINED A
RAIN/SNOW MIX AT GYY WITH A PERIOD OF REDUCED VIS/CIGS IN THE
EARLY/MID AFTERNOON. SPECIFICS ARE DIFFICULT FROM THIS DISTANCE
AND CHANGES TO THE GYY FORECAST SHOULD BE EXPECTED.

SOME OF THE GUIDANCE SHOWS THIS LAKE EFFECT PRECIPITATION MOVING
BACK WEST TOWARD ORD/MDW LATE FRIDAY AFTERNOON INTO FRIDAY
EVENING. CONFIDENCE REGARDING THIS TREND IS ALSO LOW. HOWEVER...
THE BAND WILL BE CLOSE ENOUGH TO MDW TO ADD MENTION LATE IN THE
AFTERNOON WITH THIS FORECAST. IF PRECIP IS SNOW AND DOES MAKE IT
TO ORD/MDW...IFR CIGS/VIS ARE CERTAINLY POSSIBLE. CMS

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

* HIGH FOR RAIN SHOWERS OVERNIGHT.
* MEDIUM FOR SNOW SHOWERS FRIDAY MORNING...LOW FOR DURATION/
  INTENSITY.
* LOW FOR SNOW SHOWERS LATE FRIDAY AFTERNOON.
* MEDIUM FOR MVFR CIGS OVERNIGHT/FRIDAY MORNING.
* HIGH FOR WIND SPEEDS/GUSTS/DIRECTION THRU THE PERIOD...MEDIUM
  FOR TIMING/CHANGES. CMS

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

* SATURDAY...DRY/VFR. NORTHEAST WINDS 10-15 KT.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7
AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...
LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563...1 AM FRIDAY TO 10
     PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM
FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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

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










000
FXUS63 KLOT 310017
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
717 PM CDT THU OCT 30 2014

.DISCUSSION...

EARLY EVENING UPDATE...

MADE A FEW ADJUSTMENTS TO FORECAST TO INCREASE POPS ACROSS SOUTHERN
CWA WHERE WEST-EAST BAND OF MODERATE RAIN HAD DEVELOPED LATE IN THE
AFTERNOON...AND TO SLOW ARRIVAL OF POPS ACROSS THE NORTHERN COUNTIES
A BIT IN LINE WITH VARIOUS HIGH-RES NEAR TERM MODELS WITH APPROACH
OF COLD FRONT LATER THIS EVENING.

RAIN BAND ACROSS LIVINGSTON...FORD IROQUOIS AND BENTON COUNTIES
APPEARS TO BE ASSOCIATED WITH MID-LEVEL FRONTOGENETICAL FORCING WITH
INITIAL SHORT WAVE PROPAGATING SOUTHEAST ACROSS MO/IL INTO THE LOWER
OH AND TENNESSEE VALLEYS. THIS SHOULD SCOOT OFF TO THE SOUTHEAST
OVER THE NEXT COUPLE OF HOURS. FARTHER NORTHWEST...COLD FRONT WAS
DEVELOPING SOUTHEASTWARD ACROSS SOUTHEAST MINNESOTA AND
NORTHWEST/WESTERN WISCONSIN IN RESPONSE TO STRENGTHENING PRESSURE
RISES WITH STRONG HIGH BUILDING SOUTHEAST FROM CANADA. LITTLE IN
RADAR DETECTABLE PRECIP OCCURRING ACROSS THOSE AREAS AT THIS TIME
THUS HAVE SLOWED ARRIVAL AND SLIGHTLY LOWERED POPS FOR SHOWERS
ACROSS NORTHERN IL DURING THE EARLY EVENING HOURS...MORE ALONG THE
CONCENSUS OF THE RAP/HRRR/LOCAL ARW AND EVEN MANY OF THE SYNOPTIC
SCALE MODELS WHICH HOLD MEASURABLE PRECIP OFF LARGELY UNTIL MIDNIGHT
OR AFTER.

RATZER

PREVIOUS DISCUSSION FROM 332 PM CDT...

SHORT TERM...TONIGHT THROUGH SATURDAY...
THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL
IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT
BY EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE
PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN
COOK COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS
UNCERTAINTY ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT
BANDING. SOME HAVE HINTED IN A FARTHER WEST BAND...WHICH WOULD
IMPACT MORE OF THE CHICAGO AREA. HOWEVER...I THINK AT THIS POINT
AREAS IN NORTHWEST INDIANA WILL BE MORE FAVORED...WITH THE
LIKELIHOOD OF A NEARLY DUE NORTH BOUNDARY LAYER FLOW SETTING UP OVER
LAKE MICHIGAN. THIS WOULD TEND TO FAVOR BETTER BOUNDARY LAYER
CONVERGENCE ALONG THE SOUTHERN TIP OF LAKE MICHIGAN FRIDAY
AFTERNOON...WHICH SUGGESTS THAT PORTER AND LAKE INDIANA WILL BE MORE
IN LINE WITH THE POTENTIAL HEAVIER PRECIPITATION. DUE TO THE STRONG
WINDS...IT IS ALSO LIKELY THAT THIS LAKE EFFECT PRECIP COULD BE
DRIVEN WELL INLAND ACROSS NORTHWESTERN INDIANA...POSSIBLY IMPACTING
MUCH OF JASPER AND PORTER COUNTIES AS WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION
TO GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

LONG TERM...SUNDAY THROUGH WEDNESDAY...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* RAIN SHOWERS OVERNIGHT.
* SNOW SHOWERS FRIDAY MORNING AND POSSIBLY LATE FRIDAY AFTERNOON.
* MVFR CIGS OVERNIGHT THRU FRIDAY MORNING.
* STRONG/GUSTY NORTHWEST WINDS OVERNIGHT.
* VERY STRONG/GUSTY NORTHERLY WINDS TO 40 KT FRIDAY. CMS

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

MULTIPLE FORECAST CONCERNS THIS PERIOD. LOW PRESSURE OVER THE
EASTERN U.P. WILL MOVE TO LAKE HURON BY MORNING. A TRAILING COLD
FRONT WILL MOVE ACROSS THE AREA LATE THIS EVENING INTO THE EARLY
MORNING HOURS...SHIFTING WESTERLY WINDS TO THE NORTHWEST WITH
SPEEDS SLOWLY INCREASING. AS COLDER AIR SPREADS ACROSS THE AREA
LATE THIS EVENING AND OVERNIGHT...RAIN SHOWERS ARE EXPECTED TO
DEVELOP...MOSTLY LIKELY RIGHT OVER THE TERMINALS. THERMAL PROFILES
SUGGEST PRECIP SHOULD REMAIN MAINLY RAIN THRU MUCH OF THE NIGHT
AND PERHAPS ONLY LAST A FEW HOURS THOUGH CONFIDENCE ON TIMING IS
LOW ENOUGH TO MAINTAIN VICINITY MENTION.

WINDS CONTINUE TO INCREASE FRIDAY MORNING AS COLDER AIR CONTINUES
TO POUR INTO THE REGION. AS WINDS SHIFT TO THE NORTH MID/LATE
MORNING...THERE WILL BE ANOTHER CHANCE FOR PRECIPITATION...BY THIS
TIME...THERMAL PROFILES ARE COLD ENOUGH FOR AT LEAST A MIX OF RAIN
AND SNOW BUT MAINTAINED SNOW SHOWERS FROM PREVIOUS FORECAST.
CONFIDENCE REGARDING SPECIFICS DURING THIS TIME PERIOD ARE LOW...
INCLUDING DURATION AND INTENSITY. AS THIS TIME PERIOD APPROACHES
AND TRENDS EMERGE ON RADAR...A SHORT DURATION TEMPO FOR LOWER
CONDITIONS MAY BE NEEDED.

CIGS SHOULD REMAIN VFR THIS EVENING AND LOWER TO MVFR OVERNIGHT
WITH THE POTENTIAL FOR A SHORT PERIOD OF LOW MVFR POSSIBLE. ONCE
PRECIP ENDS IN THE MORNING...CIGS SHOULD LIFT TO EITHER HIGH MVFR
OR LOW VFR.

WINDS WILL STEADILY INCREASE FROM THE EARLY MORNING THRU THE LATE
MORNING AND TURN NORTHERLY. PREVAILING SPEEDS IN THE MID 20 KT
RANGE LOOK ON TRACK WITH PREVAILING GUSTS INTO THE MID/UPPER 30KT
RANGE WITH THE POTENTIAL FOR GUSTS TO 40KTS IN THE LATE MORNING
AND EARLY AFTERNOON. SPEEDS/GUSTS WILL SLOWLY DIMINISH LATE IN THE
AFTERNOON...ESPECIALLY AT RFD...BUT WINDY CONDITIONS WILL CONTINUE
INTO FRIDAY EVENING.

AS FOR GYY AND LAKE EFFECT...A BAND OF LAKE EFFECT RAIN AND SNOW
IS EXPECTED TO DEVELOP BY MID MORNING AND CONTINUE INTO FRIDAY
EVENING...AFFECTING NORTHWEST INDIANA FOR MUCH OF THE DAY. THIS
PRECIPITATION IS EXPECTED TO BE QUIET INTENSE WITH THUNDER LIKELY.
IF THIS INTENSE PRECIP IS SUFFICIENT ENOUGH TO COOL THE LOWER
LAYERS...THE PRECIP MAY SWITCH OVER TO ALL OR PREDOMINANTLY SNOW.
CONFIDENCE IN HOW LONG THIS MAY PERSIST IS LOW AND MAINTAINED A
RAIN/SNOW MIX AT GYY WITH A PERIOD OF REDUCED VIS/CIGS IN THE
EARLY/MID AFTERNOON. SPECIFICS ARE DIFFICULT FROM THIS DISTANCE
AND CHANGES TO THE GYY FORECAST SHOULD BE EXPECTED.

SOME OF THE GUIDANCE SHOWS THIS LAKE EFFECT PRECIPITATION MOVING
BACK WEST TOWARD ORD/MDW LATE FRIDAY AFTERNOON INTO FRIDAY
EVENING. CONFIDENCE REGARDING THIS TREND IS ALSO LOW. HOWEVER...
THE BAND WILL BE CLOSE ENOUGH TO MDW TO ADD MENTION LATE IN THE
AFTERNOON WITH THIS FORECAST. IF PRECIP IS SNOW AND DOES MAKE IT
TO ORD/MDW...IFR CIGS/VIS ARE CERTAINLY POSSIBLE. CMS

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

* HIGH FOR RAIN SHOWERS OVERNIGHT.
* MEDIUM FOR SNOW SHOWERS FRIDAY MORNING...LOW FOR DURATION/
  INTENSITY.
* LOW FOR SNOW SHOWERS LATE FRIDAY AFTERNOON.
* MEDIUM FOR MVFR CIGS OVERNIGHT/FRIDAY MORNING.
* HIGH FOR WIND SPEEDS/GUSTS/DIRECTION THRU THE PERIOD...MEDIUM
  FOR TIMING/CHANGES. CMS

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

* SATURDAY...DRY/VFR. NORTHEAST WINDS 10-15 KT.
* SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.
* MONDAY...SLIGHT CHANCE OF SHRA. GUSTY SOUTHWEST WINDS.
* TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.
* WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563...1 AM FRIDAY TO 10
     PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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000
FXUS63 KLOT 302322 CCA
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
620 PM CDT THU OCT 30 2014

.DISCUSSION...

EARLY EVENING UPDATE...

MADE A FEW ADJUSTMENTS TO FORECAST TO INCREASE POPS ACROSS SOUTHERN
CWA WHERE WEST-EAST BAND OF MODERATE RAIN HAD DEVELOPED LATE IN THE
AFTERNOON...AND TO SLOW ARRIVAL OF POPS ACROSS THE NORTHERN COUNTIES
A BIT IN LINE WITH VARIOUS HIGH-RES NEAR TERM MODELS WITH APPROACH
OF COLD FRONT LATER THIS EVENING.

RAIN BAND ACROSS LIVINGSTON...FORD IROQUOIS AND BENTON COUNTIES
APPEARS TO BE ASSOCIATED WITH MID-LEVEL FRONTOGENETICAL FORCING WITH
INITIAL SHORT WAVE PROPAGATING SOUTHEAST ACROSS MO/IL INTO THE LOWER
OH AND TENNESSEE VALLEYS. THIS SHOULD SCOOT OFF TO THE SOUTHEAST
OVER THE NEXT COUPLE OF HOURS. FARTHER NORTHWEST...COLD FRONT WAS
DEVELOPING SOUTHEASTWARD ACROSS SOUTHEAST MINNESOTA AND
NORTHWEST/WESTERN WISCONSIN IN RESPONSE TO STRENGTHENING PRESSURE
RISES WITH STRONG HIGH BUILDING SOUTHEAST FROM CANADA. LITTLE IN
RADAR DETECTABLE PRECIP OCCURRING ACROSS THOSE AREAS AT THIS TIME
THUS HAVE SLOWED ARRIVAL AND SLIGHTLY LOWERED POPS FOR SHOWERS
ACROSS NORTHERN IL DURING THE EARLY EVENING HOURS...MORE ALONG THE
CONCENSUS OF THE RAP/HRRR/LOCAL ARW AND EVEN MANY OF THE SYNOPTIC
SCALE MODELS WHICH HOLD MEASURABLE PRECIP OFF LARGELY UNTIL MIDNIGHT
OR AFTER.

RATZER

PREVIOUS DISCUSSION FROM 332 PM CDT...

SHORT TERM...TONIGHT THROUGH SATURDAY...
THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL
IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT
BY EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE
PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN
COOK COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS
UNCERTAINTY ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT
BANDING. SOME HAVE HINTED IN A FARTHER WEST BAND...WHICH WOULD
IMPACT MORE OF THE CHICAGO AREA. HOWEVER...I THINK AT THIS POINT
AREAS IN NORTHWEST INDIANA WILL BE MORE FAVORED...WITH THE
LIKELIHOOD OF A NEARLY DUE NORTH BOUNDARY LAYER FLOW SETTING UP OVER
LAKE MICHIGAN. THIS WOULD TEND TO FAVOR BETTER BOUNDARY LAYER
CONVERGENCE ALONG THE SOUTHERN TIP OF LAKE MICHIGAN FRIDAY
AFTERNOON...WHICH SUGGESTS THAT PORTER AND LAKE INDIANA WILL BE MORE
IN LINE WITH THE POTENTIAL HEAVIER PRECIPITATION. DUE TO THE STRONG
WINDS...IT IS ALSO LIKELY THAT THIS LAKE EFFECT PRECIP COULD BE
DRIVEN WELL INLAND ACROSS NORTHWESTERN INDIANA...POSSIBLY IMPACTING
MUCH OF JASPER AND PORTER COUNTIES AS WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION
TO GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

LONG TERM...SUNDAY THROUGH WEDNESDAY...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NO ISSUES IN THE NEAR TERM.

* SOUTHWEST WINDS SHIFTING TO THE NORTHWEST WITH FROPA
  TONIGHT...WITH GUSTS INCREASING THROUGH MIDDAY FRIDAY WHILE
  BECOMING MORE NORTHERLY.

* CHANCE OF -SHRA/-SHSN TONIGHT THROUGH EARLY FRIDAY MORNING.

* MVFR CEILINGS LATE TONIGHT INTO FRIDAY MORNING.

RODRIGUEZ/CMS

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

RELATIVELY QUIET CONDITIONS EARLY THIS AFTERNOON WILL CONTINUE THIS
AFTERNOON...WHILE SOUTHWEST WINDS PREVAIL AND MID/HIGH LEVEL CLOUD
COVER CONTINUE TO STREAM OVERHEAD. CONDITIONS WILL BEGIN
DETERIORATING TONIGHT AS SYSTEM/FRONT PUSH THROUGH THE REGION. THE
CURRENT SOUTHWEST WINDS WILL TURN WEST AND NORTHWEST TONIGHT WITH
WIND SPEED/GUSTS QUICKLY INCREASING. LOWERING CEILINGS TO MVFR WILL
ALSO OCCUR WITH THE ARRIVAL OF THIS WIND SHIFT...LIKELY PERSISTING
FOR MUCH OF FRIDAY MORNING. MOISTURE WILL ALSO BE SUFFICIENT FOR
RAIN SHOWERS TO INITIALLY BE POSSIBLE BUT WITH MUCH COLDER AIR
QUICKLY FILTERING IN...SNOW SHOWERS WILL THEN BE POSSIBLE. EXPECT
THESE RAIN/SNOW SHOWERS TO BE ON THE LIGHTER SIDE...WITH NO VIS
RESTRICTION EXPECTED AS WELL AS NO SNOW ACCUMULATION. THE WINDS WILL
CONTINUE TO SHIFT MORE NORTHERLY FRIDAY MORNING AND LIKELY REMAIN IN
THIS NORTH DIRECTION FOR MUCH OF FRIDAY. THIS ORIENTATION WILL
COINCIDE WITH VERY STRONG WINDS...WITH GUSTS ANTICIPATED TO BE
AROUND 40 KT. CONDITIONS SHOULD BE BACK TO VFR FOR THE REMAINDER OF
THE DAY/FORECAST PERIOD...BUT A TREND BACK TOWARDS DETERIORATING
CONDITIONS COULD BE POSSIBLE IF LAKE EFFECT PRECIP AND CLOUD COVER
MOVE TOWARDS THE TERMINALS FRIDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF WIND DIRECTION AND SPEED/GUSTS...MEDIUM HIGH
  CONFIDENCE OF EXACT TIMING OF FROPA.

* HIGH CONFIDENCE OF -SHRA/-SHSN...MEDIUM CONFIDENCE OF DURATION.

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

RODRIGUEZ/CMS

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7
AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...
LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563...1 AM FRIDAY TO 10
     PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM
FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 302320
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
506 PM CDT THU OCT 30 2014

.UPDATE...

EARLY EVENING UPDATE...

MADE A FEW ADJUSTMENTS TO FORECAST TO INCREASE POPS ACROSS SOUTHERN
CWA WHERE WEST-EAST BAND OF MODERATE RAIN HAD DEVELOPED LATE IN THE
AFTERNOON...AND TO SLOW ARRIVAL OF POPS ACROSS THE NORTHERN COUNTIES
A BIT IN LINE WITH VARIOUS HIGH-RES NEAR TERM MODELS WITH APPROACH
OF COLD FRONT LATER THIS EVENING.

RAIN BAND ACROSS LIVINGSTON...FORD IROQUOIS AND BENTON COUNTIES
APPEARS TO BE ASSOCIATED WITH MID-LEVEL FRONTOGENETICAL FORCING WITH
INITIAL SHORT WAVE PROPAGATING SOUTHEAST ACROSS MO/IL INTO THE LOWER
OH AND TENNESSEE VALLEYS. THIS SHOULD SCOOT OFF TO THE SOUTHEAST
OVER THE NEXT COUPLE OF HOURS. FARTHER NORTHWEST...COLD FRONT WAS
DEVELOPING SOUTHEASTWARD ACROSS SOUTHEAST MINNESOTA AND
NORTHWEST/WESTERN WISCONSIN IN RESPONSE TO STRENGTHENING PRESSURE
RISES WITH STRONG HIGH BUILDING SOUTHEAST FROM CANADA. LITTLE IN
RADAR DETECTABLE PRECIP OCCURRING ACROSS THOSE AREAS AT THIS TIME
THUS HAVE SLOWED ARRIVAL AND SLIGHTLY LOWERED POPS FOR SHOWERS
ACROSS NORTHERN IL DURING THE EARLY EVENING HOURS...MORE ALONG THE
CONCENSUS OF THE RAP/HRRR/LOCAL ARW AND EVEN MANY OF THE SYNOPTIC
SCALE MODELS WHICH HOLD MEASURABLE PRECIP OFF LARGELY UNTIL MIDNIGHT
OR AFTER.

RATZER

PREVIOUS DISCUSSION FROM 332 PM CDT...

SHORT TERM...TONIGHT THROUGH SATURDAY...
THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL
IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT
BY EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE
PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN
COOK COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS
UNCERTAINTY ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT
BANDING. SOME HAVE HINTED IN A FARTHER WEST BAND...WHICH WOULD
IMPACT MORE OF THE CHICAGO AREA. HOWEVER...I THINK AT THIS POINT
AREAS IN NORTHWEST INDIANA WILL BE MORE FAVORED...WITH THE
LIKELIHOOD OF A NEARLY DUE NORTH BOUNDARY LAYER FLOW SETTING UP OVER
LAKE MICHIGAN. THIS WOULD TEND TO FAVOR BETTER BOUNDARY LAYER
CONVERGENCE ALONG THE SOUTHERN TIP OF LAKE MICHIGAN FRIDAY
AFTERNOON...WHICH SUGGESTS THAT PORTER AND LAKE INDIANA WILL BE MORE
IN LINE WITH THE POTENTIAL HEAVIER PRECIPITATION. DUE TO THE STRONG
WINDS...IT IS ALSO LIKELY THAT THIS LAKE EFFECT PRECIP COULD BE
DRIVEN WELL INLAND ACROSS NORTHWESTERN INDIANA...POSSIBLY IMPACTING
MUCH OF JASPER AND PORTER COUNTIES AS WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION
TO GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

LONG TERM...SUNDAY THROUGH WEDNESDAY...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NO ISSUES IN THE NEAR TERM.

* SOUTHWEST WINDS SHIFTING TO THE NORTHWEST WITH FROPA
  TONIGHT...WITH GUSTS INCREASING THROUGH MIDDAY FRIDAY WHILE
  BECOMING MORE NORTHERLY.

* CHANCE OF -SHRA/-SHSN TONIGHT THROUGH EARLY FRIDAY MORNING.

* MVFR CEILINGS LATE TONIGHT INTO FRIDAY MORNING.

RODRIGUEZ/CMS

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

RELATIVELY QUIET CONDITIONS EARLY THIS AFTERNOON WILL CONTINUE THIS
AFTERNOON...WHILE SOUTHWEST WINDS PREVAIL AND MID/HIGH LEVEL CLOUD
COVER CONTINUE TO STREAM OVERHEAD. CONDITIONS WILL BEGIN
DETERIORATING TONIGHT AS SYSTEM/FRONT PUSH THROUGH THE REGION. THE
CURRENT SOUTHWEST WINDS WILL TURN WEST AND NORTHWEST TONIGHT WITH
WIND SPEED/GUSTS QUICKLY INCREASING. LOWERING CEILINGS TO MVFR WILL
ALSO OCCUR WITH THE ARRIVAL OF THIS WIND SHIFT...LIKELY PERSISTING
FOR MUCH OF FRIDAY MORNING. MOISTURE WILL ALSO BE SUFFICIENT FOR
RAIN SHOWERS TO INITIALLY BE POSSIBLE BUT WITH MUCH COLDER AIR
QUICKLY FILTERING IN...SNOW SHOWERS WILL THEN BE POSSIBLE. EXPECT
THESE RAIN/SNOW SHOWERS TO BE ON THE LIGHTER SIDE...WITH NO VIS
RESTRICTION EXPECTED AS WELL AS NO SNOW ACCUMULATION. THE WINDS WILL
CONTINUE TO SHIFT MORE NORTHERLY FRIDAY MORNING AND LIKELY REMAIN IN
THIS NORTH DIRECTION FOR MUCH OF FRIDAY. THIS ORIENTATION WILL
COINCIDE WITH VERY STRONG WINDS...WITH GUSTS ANTICIPATED TO BE
AROUND 40 KT. CONDITIONS SHOULD BE BACK TO VFR FOR THE REMAINDER OF
THE DAY/FORECAST PERIOD...BUT A TREND BACK TOWARDS DETERIORATING
CONDITIONS COULD BE POSSIBLE IF LAKE EFFECT PRECIP AND CLOUD COVER
MOVE TOWARDS THE TERMINALS FRIDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF WIND DIRECTION AND SPEED/GUSTS...MEDIUM HIGH
  CONFIDENCE OF EXACT TIMING OF FROPA.

* HIGH CONFIDENCE OF -SHRA/-SHSN...MEDIUM CONFIDENCE OF DURATION.

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

RODRIGUEZ/CMS

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7
AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...
LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563...1 AM FRIDAY TO 10
     PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM
FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 302206
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
506 PM CDT THU OCT 30 2014

.DISCUSSION...

SHORT TERM...TONIGHT THROUGH SATURDAY...
THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT BY
EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN COOK
COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS UNCERTAINTY
ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT BANDING. SOME HAVE
HINTED IN A FARTHER WEST BAND...WHICH WOULD IMPACT MORE OF THE
CHICAGO AREA. HOWEVER...I THINK AT THIS POINT AREAS IN NORTHWEST
INDIANA WILL BE MORE FAVORED...WITH THE LIKELIHOOD OF A NEARLY DUE
NORTH BOUNDARY LAYER FLOW SETTING UP OVER LAKE MICHIGAN. THIS WOULD
TEND TO FAVOR BETTER BOUNDARY LAYER CONVERGENCE ALONG THE SOUTHERN
TIP OF LAKE MICHIGAN FRIDAY AFTERNOON...WHICH SUGGESTS THAT PORTER
AND LAKE INDIANA WILL BE MORE IN LINE WITH THE POTENTIAL HEAVIER
PRECIPITATION. DUE TO THE STRONG WINDS...IT IS ALSO LIKELY THAT THIS
LAKE EFFECT PRECIP COULD BE DRIVEN WELL INLAND ACROSS NORTHWESTERN
INDIANA...POSSIBLY IMPACTING MUCH OF JASPER AND PORTER COUNTIES AS
WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION TO
GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

LONG TERM...SUNDAY THROUGH WEDNESDAY...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NO ISSUES IN THE NEAR TERM.

* SOUTHWEST WINDS SHIFTING TO THE NORTHWEST WITH FROPA
  TONIGHT...WITH GUSTS INCREASING THROUGH MIDDAY FRIDAY WHILE
  BECOMING MORE NORTHERLY.

* CHANCE OF -SHRA/-SHSN TONIGHT THROUGH EARLY FRIDAY MORNING.

* MVFR CEILINGS LATE TONIGHT INTO FRIDAY MORNING.

RODRIGUEZ/CMS

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

RELATIVELY QUIET CONDITIONS EARLY THIS AFTERNOON WILL CONTINUE THIS
AFTERNOON...WHILE SOUTHWEST WINDS PREVAIL AND MID/HIGH LEVEL CLOUD
COVER CONTINUE TO STREAM OVERHEAD. CONDITIONS WILL BEGIN
DETERIORATING TONIGHT AS SYSTEM/FRONT PUSH THROUGH THE REGION. THE
CURRENT SOUTHWEST WINDS WILL TURN WEST AND NORTHWEST TONIGHT WITH
WIND SPEED/GUSTS QUICKLY INCREASING. LOWERING CEILINGS TO MVFR WILL
ALSO OCCUR WITH THE ARRIVAL OF THIS WIND SHIFT...LIKELY PERSISTING
FOR MUCH OF FRIDAY MORNING. MOISTURE WILL ALSO BE SUFFICIENT FOR
RAIN SHOWERS TO INITIALLY BE POSSIBLE BUT WITH MUCH COLDER AIR
QUICKLY FILTERING IN...SNOW SHOWERS WILL THEN BE POSSIBLE. EXPECT
THESE RAIN/SNOW SHOWERS TO BE ON THE LIGHTER SIDE...WITH NO VIS
RESTRICTION EXPECTED AS WELL AS NO SNOW ACCUMULATION. THE WINDS WILL
CONTINUE TO SHIFT MORE NORTHERLY FRIDAY MORNING AND LIKELY REMAIN IN
THIS NORTH DIRECTION FOR MUCH OF FRIDAY. THIS ORIENTATION WILL
COINCIDE WITH VERY STRONG WINDS...WITH GUSTS ANTICIPATED TO BE
AROUND 40 KT. CONDITIONS SHOULD BE BACK TO VFR FOR THE REMAINDER OF
THE DAY/FORECAST PERIOD...BUT A TREND BACK TOWARDS DETERIORATING
CONDITIONS COULD BE POSSIBLE IF LAKE EFFECT PRECIP AND CLOUD COVER
MOVE TOWARDS THE TERMINALS FRIDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF WIND DIRECTION AND SPEED/GUSTS...MEDIUM HIGH
  CONFIDENCE OF EXACT TIMING OF FROPA.

* HIGH CONFIDENCE OF -SHRA/-SHSN...MEDIUM CONFIDENCE OF DURATION.

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

RODRIGUEZ/CMS

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563...1 AM FRIDAY TO 10
     PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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000
FXUS63 KLOT 302206
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
506 PM CDT THU OCT 30 2014

.DISCUSSION...

SHORT TERM...TONIGHT THROUGH SATURDAY...
THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT BY
EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN COOK
COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS UNCERTAINTY
ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT BANDING. SOME HAVE
HINTED IN A FARTHER WEST BAND...WHICH WOULD IMPACT MORE OF THE
CHICAGO AREA. HOWEVER...I THINK AT THIS POINT AREAS IN NORTHWEST
INDIANA WILL BE MORE FAVORED...WITH THE LIKELIHOOD OF A NEARLY DUE
NORTH BOUNDARY LAYER FLOW SETTING UP OVER LAKE MICHIGAN. THIS WOULD
TEND TO FAVOR BETTER BOUNDARY LAYER CONVERGENCE ALONG THE SOUTHERN
TIP OF LAKE MICHIGAN FRIDAY AFTERNOON...WHICH SUGGESTS THAT PORTER
AND LAKE INDIANA WILL BE MORE IN LINE WITH THE POTENTIAL HEAVIER
PRECIPITATION. DUE TO THE STRONG WINDS...IT IS ALSO LIKELY THAT THIS
LAKE EFFECT PRECIP COULD BE DRIVEN WELL INLAND ACROSS NORTHWESTERN
INDIANA...POSSIBLY IMPACTING MUCH OF JASPER AND PORTER COUNTIES AS
WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION TO
GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

LONG TERM...SUNDAY THROUGH WEDNESDAY...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NO ISSUES IN THE NEAR TERM.

* SOUTHWEST WINDS SHIFTING TO THE NORTHWEST WITH FROPA
  TONIGHT...WITH GUSTS INCREASING THROUGH MIDDAY FRIDAY WHILE
  BECOMING MORE NORTHERLY.

* CHANCE OF -SHRA/-SHSN TONIGHT THROUGH EARLY FRIDAY MORNING.

* MVFR CEILINGS LATE TONIGHT INTO FRIDAY MORNING.

RODRIGUEZ/CMS

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

RELATIVELY QUIET CONDITIONS EARLY THIS AFTERNOON WILL CONTINUE THIS
AFTERNOON...WHILE SOUTHWEST WINDS PREVAIL AND MID/HIGH LEVEL CLOUD
COVER CONTINUE TO STREAM OVERHEAD. CONDITIONS WILL BEGIN
DETERIORATING TONIGHT AS SYSTEM/FRONT PUSH THROUGH THE REGION. THE
CURRENT SOUTHWEST WINDS WILL TURN WEST AND NORTHWEST TONIGHT WITH
WIND SPEED/GUSTS QUICKLY INCREASING. LOWERING CEILINGS TO MVFR WILL
ALSO OCCUR WITH THE ARRIVAL OF THIS WIND SHIFT...LIKELY PERSISTING
FOR MUCH OF FRIDAY MORNING. MOISTURE WILL ALSO BE SUFFICIENT FOR
RAIN SHOWERS TO INITIALLY BE POSSIBLE BUT WITH MUCH COLDER AIR
QUICKLY FILTERING IN...SNOW SHOWERS WILL THEN BE POSSIBLE. EXPECT
THESE RAIN/SNOW SHOWERS TO BE ON THE LIGHTER SIDE...WITH NO VIS
RESTRICTION EXPECTED AS WELL AS NO SNOW ACCUMULATION. THE WINDS WILL
CONTINUE TO SHIFT MORE NORTHERLY FRIDAY MORNING AND LIKELY REMAIN IN
THIS NORTH DIRECTION FOR MUCH OF FRIDAY. THIS ORIENTATION WILL
COINCIDE WITH VERY STRONG WINDS...WITH GUSTS ANTICIPATED TO BE
AROUND 40 KT. CONDITIONS SHOULD BE BACK TO VFR FOR THE REMAINDER OF
THE DAY/FORECAST PERIOD...BUT A TREND BACK TOWARDS DETERIORATING
CONDITIONS COULD BE POSSIBLE IF LAKE EFFECT PRECIP AND CLOUD COVER
MOVE TOWARDS THE TERMINALS FRIDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF WIND DIRECTION AND SPEED/GUSTS...MEDIUM HIGH
  CONFIDENCE OF EXACT TIMING OF FROPA.

* HIGH CONFIDENCE OF -SHRA/-SHSN...MEDIUM CONFIDENCE OF DURATION.

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

RODRIGUEZ/CMS

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563...1 AM FRIDAY TO 10
     PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 302032
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
332 PM CDT THU OCT 30 2014


.DISCUSSION...

SHORT TERM...TONIGHT THROUGH SATURDAY...
THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO CENTER AROUND
THE STORM SYSTEM EXPECTED IMPACT THE REGION LATE TONIGHT THROUGH
FRIDAY NIGHT. STRONG WINDS...AND THE POTENTIAL FOR SOME PERIODS OF
HEAVY LAKE EFFECT SNOW ARE THE PRIMARY CONCERNS.

WE ARE ISSUING A WIND ADVISORY FOR MOST OF THE EASTERN HALF OF THE
AREA...WITH THE EXCEPTION OF LAKE...PORTER...JASPER AND NEWTON
COUNTIES IN INDIANA...WHERE A WINTER WEATHER ADVISORY IS BEING
ISSUED. SEE BELOW FOR MORE DETAILS.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON SHOWS A RATHER VIGOROUS
UPPER LEVEL IMPULSE NOW MOVING JUST EAST OF LAKE WINNIPEG AND OVER
FAR SOUTHWESTERN ONTARIO. THIS WAVE IS EXPECTED TO CONTINUE DIGGING
SOUTH-SOUTHEASTWARD TONIGHT ALONG THE EASTERN PERIPHERY OF AN UPPER
RIDGE...CURRENT CENTERED ACROSS THE INTER MOUNTAIN WEST. AS THIS
OCCURS...AN AREA OF SURFACE LOW PRESSURE WILL SHIFT SOUTHWARD ACROSS
LOWER MICHIGAN INTO FRIDAY MORNING. FARTHER NORTHWEST...A RATHER
STOUT 1036 MB HIGH IS ALSO EXPECTED TO RAPIDLY BUILD SOUTHEASTWARD
ACROSS THE DAKOTAS AND UPPER MIDWEST INTO FRIDAY. THIS STILL LOOKS
TO SET THE STAGE FOR STRONG NORTHERN WINDS ACROSS THE AREA DURING
THE DAY FRIDAY AS STRONG PRESSURE RISES AND STRONG COLD AIR
ADVECTION LEAD TO A QUICK RAMP UP OF NORTHERLY WINDS IN THE WAKE OF
A COLD FRONTAL PASSAGE LATE TONIGHT. MODEL SOUNDINGS ALL SUGGEST
MEAN MIXING LAYER WIND SPEEDS COULD TOP 40 KT ACROSS MAINLY THE
EASTERN HALF OF THE AREA INLAND FROM THE LAKE...MEANING WIND GUSTS
COULD EASILY REACH THIS MAGNITUDE IN MOST AREAS. HOWEVER...AREAS
DIRECTLY ADJACENT TO LAKE MICHIGAN IN NORTHEASTERN ILLINOIS AND
NORTHWESTERN INDIANA COULD EXPERIENCE EVEN STRONGER GUSTS UP AROUND
50 KT WITH THE STRONG NORTHERLY ONSHORE COMPONENT TO THE WINDS.
WINDS LOOK TO REMAIN INTO THE EVENING ON HALLOWEEN...THOUGH WIND
SPEEDS SHOULD GRADUALLY WEAKEN THROUGH THE NIGHT.

THE LAKE SHORE FLOOD ADVISORY WILL CONTINUE FOR AREAS NEAR THE LAKE
AS LARGE BATTERING WAVES IN EXCESS OF 20 FT APPEAR LIKELY...AND AS
THE PREVIOUS DISCUSSION MENTIONED...LAKE LEVELS ARE ABOUT 2 FT
HIGHER THAN PAST YEARS...WHICH COULD MAKE THE IMPACTS OF THESE WAVES
HIGHER THEN SIMILAR WAVE EVENTS IN THE PAST COUPLE OF YEARS.

DUE TO THE LIKELIHOOD OF THESE STRONG WINDS...WE HAVE ISSUED A WIND
ADVISORY FOR MUCH OF THE EASTERN HALF OF MY CWA. THIS
INCLUDES AREAS BASICALLY ALONG AND EAST OF A LINE FROM HARVARD
SOUTHWARD THROUGH KANKAKEE AND IROQUOIS COUNTIES. THE ONLY EXCEPTION
TO THIS WIND ADVISORY IS FOR LAKE COUNTY INDIANA...AS WELL AS
PORTER...JASPER AND NEWTON COUNTIES...WHERE A WINTER WEATHER
ADVISORY IS BEING ISSUED IN PLACE OF A WIND ADVISORY FOR THE
COMBINATION OF THESE STRONG WINDS AND ALSO THE INCREASING POTENTIAL
FOR SOME ACCUMULATING LAKE EFFECT SNOW ON FRIDAY INTO FRIDAY
EVENING.

PRECIPITATION WITH THE APPROACHING COLD FRONT AND UPPER LEVEL IMPULSE
WILL LIKELY BEGIN TO ENTER FAR NORTHERN ILLINOIS AFTER 10 PM THIS
EVENING...AND BE IN THE FORM OF RAIN SHOWERS. THIS INITIAL ROUND OF
SHOWERS SHOULD MOVE SOUTHWARD ACROSS THE AREA THROUGH THE NIGHT...IN
CLOSE PROXIMITY THE INCREASING FRONTOGENESIS IN THE VICINITY OF THE
COLD FRONTAL BOUNDARY. THIS SHOULD BE A FAIRLY PROGRESSIVE AREA OF
SHOWERS...WITH MOST AREAS ACROSS NORTH CENTRAL ILLINOIS DRYING OUT BY
EARLY FRIDAY MORNING.

THE SECOND STAGE OF PRECIPITATION WILL BE MORE OF A TRUE LAKE EFFECT
SETUP. A COLD AIRMASS FEATURING -7 DEGREE C TEMPERATURES AT 850 MB
WILL MOVE OVER THE LAKE...WHICH IS CURRENTLY REPORTING A 53F (11.7C)
DEGREE WATER TEMPERATURE AT THE SOUTH BUOY. THEREFORE...DELTA T`S
SHOULD END UP VERY FAVORABLE AROUND 19 DEGREES C. IN ADDITION...DEEP
LAKE INDUCED INSTABILITY IS STILL EXPECTED...WITH EQUILIBRIUM LEVELS
LIKELY TO REACH OR EVEN EXCEED 16,000 FT AGL. THEREFORE...THE THREAT
FOR THUNDER AND LIGHTNING HAS NOT CHANGED...WITH CONVECTIVE PROCESSES
LIKELY TO BE MORE THAN DEEP ENOUGH THROUGH THE -10 TO -20 LAYER TO
RESULT IN GOOD CHARGE SEPARATION.

IT LOOKS AS THOUGH THIS LAKE EFFECT BAND COULD BEGIN TO SET UP
ACROSS NORTHWESTERN INDIANA AND PERHAPS PORTIONS OF SOUTHEASTERN COOK
COUNTY BY LATE FRIDAY MORNING. HI RES GUIDANCE SUGGESTS UNCERTAINTY
ON THE EXACT AREAS THAT WILL GET THIS LAKE EFFECT BANDING. SOME HAVE
HINTED IN A FARTHER WEST BAND...WHICH WOULD IMPACT MORE OF THE
CHICAGO AREA. HOWEVER...I THINK AT THIS POINT AREAS IN NORTHWEST
INDIANA WILL BE MORE FAVORED...WITH THE LIKELIHOOD OF A NEARLY DUE
NORTH BOUNDARY LAYER FLOW SETTING UP OVER LAKE MICHIGAN. THIS WOULD
TEND TO FAVOR BETTER BOUNDARY LAYER CONVERGENCE ALONG THE SOUTHERN
TIP OF LAKE MICHIGAN FRIDAY AFTERNOON...WHICH SUGGESTS THAT PORTER
AND LAKE INDIANA WILL BE MORE IN LINE WITH THE POTENTIAL HEAVIER
PRECIPITATION. DUE TO THE STRONG WINDS...IT IS ALSO LIKELY THAT THIS
LAKE EFFECT PRECIP COULD BE DRIVEN WELL INLAND ACROSS NORTHWESTERN
INDIANA...POSSIBLY IMPACTING MUCH OF JASPER AND PORTER COUNTIES AS
WELL.

UNCERTAINTY IN PRECIPITATION TYPE IS STILL SOMEWHAT HIGH...AS
SOME WARMER AIR MOVING OFF THE LAKE SHOULD MAKE BOUNDARY LAYER
TEMPERATURES MARGINAL FOR SNOW TO REACH THE SURFACE. HOWEVER...WITH
THE AFOREMENTIONED CONVECTIVE INSTABILITY AND THE GOOD POTENTIAL FOR
SOME HEAVIER PRECIP RATES...IT IS VERY MUCH IN THE REALM OF
POSSIBILITIES THAT ENHANCED DYNAMIC COOLING COULD RESULT IN A COLD
ENOUGH BOUNDARY LAYER SUPPORTIVE OF HEAVY SNOW. IT APPEARS THAT
AREAS INLAND FROM THE IMMEDIATE LAKE SHORE WOULD HAVE THE BEST
POTENTIAL FOR SNOW...THOUGH EVEN AREAS ALONG THE LAKE COULD CHANGE
OVER/MIX WITH SNOW. OVERALL...WITH THE POTENTIAL FOR SOME HEAVIER
BANDS OF SNOW WITH SOME ACCUMULATIONS POSSIBLE (POSSIBLY A FEW
INCHES IN SOME AREAS) ALONG WITH THE VERY STRONG NORTHERLY
WINDS...WE HAVE CHOSEN TO ISSUE THE WINTER WEATHER ADVISORY FOR THE
4 NORTHWESTERN INDIANA COUNTIES. IF...HOWEVER...THE TRANSITION TO
SNOW DOES NOT PAN OUT AS CURRENT THINKING SUGGESTS...WINDS WOULD BE
THE MAIN HAZARD ON FRIDAY...AND THE WINTER WEATHER ADVISORY COULD
THEN BE REPLACED WITH A WIND ADVISORY. THEREFORE...IN SPITE OF THE
UNCERTAINTIES ON WHEN CHANGE OVERS TO SNOW WILL OCCUR AND HOW MUCH
SNOW WILL ACTUALLY FALL...WE FEEL AT THIS POINT...TO ERROR ON THE
SIDE OF CAUTION...AS THERE IS A POTENTIAL FOR SOME VERY HEAVY SNOW
IN ADDITION TO THE STRONG WINDS.

THE WINDS ARE EXPECTED TO GRADUALLY VEER MORE NORTHEASTERLY FRIDAY
NIGHT...AND THIS COULD ALLOW SOME OF THE LAKE EFFECT PRECIPITATION TO
GET INTO NORTHEASTERN ILLINOIS FOR A BRIEF PERIOD FRIDAY EVENING.
HOWEVER...MODEL GUIDANCE CONTINUES TO SUGGEST THAT INVERSION HEIGHTS
WILL CRASH IN A HURRY BY LATE FRIDAY EVENING AS HEIGHTS AND
TEMPERATURES BEGIN TO RISE ALOFT. THEREFORE...ANY SNOW SHOWERS THAT
GET INTO NORTHEASTERN ILLINOIS WOULD LIKELY BE LIGHT AND COME TO AN
END LATE FRIDAY NIGHT/EARLY SAT MORNING.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY

LONG TERM...SUNDAY THROUGH WEDNESDAY...

HIGH TEMPERATURES WILL MODERATE INTO EARLY NEXT WEEK AS THE
WESTERN CONUS UPPER RIDGE BUILDS EASTWARD OVER THE REGION. ANOTHER
COLD FRONT LOOKS TO TAKE AIM ON THE AREA AROUND NEXT
TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE OF SHOWERS.
OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING THE LATER
HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NO ISSUES IN THE NEAR TERM.

* SOUTHWEST WINDS SHIFTING TO THE NORTHWEST WITH FROPA
  TONIGHT...WITH GUSTS INCREASING THROUGH MIDDAY FRIDAY WHILE
  BECOMING MORE NORTHERLY.

* CHANCE OF -SHRA/-SHSN TONIGHT THROUGH EARLY FRIDAY MORNING.

* MVFR CEILINGS LATE TONIGHT INTO FRIDAY MORNING.

RODRIGUEZ

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

RELATIVELY QUIET CONDITIONS EARLY THIS AFTERNOON WILL CONTINUE THIS
AFTERNOON...WHILE SOUTHWEST WINDS PREVAIL AND MID/HIGH LEVEL CLOUD
COVER CONTINUE TO STREAM OVERHEAD. CONDITIONS WILL BEGIN
DETERIORATING TONIGHT AS SYSTEM/FRONT PUSH THROUGH THE REGION. THE
CURRENT SOUTHWEST WINDS WILL TURN WEST AND NORTHWEST TONIGHT WITH
WIND SPEED/GUSTS QUICKLY INCREASING. LOWERING CEILINGS TO MVFR WILL
ALSO OCCUR WITH THE ARRIVAL OF THIS WIND SHIFT...LIKELY PERSISTING
FOR MUCH OF FRIDAY MORNING. MOISTURE WILL ALSO BE SUFFICIENT FOR
RAIN SHOWERS TO INITIALLY BE POSSIBLE BUT WITH MUCH COLDER AIR
QUICKLY FILTERING IN...SNOW SHOWERS WILL THEN BE POSSIBLE. EXPECT
THESE RAIN/SNOW SHOWERS TO BE ON THE LIGHTER SIDE...WITH NO VIS
RESTRICTION EXPECTED AS WELL AS NO SNOW ACCUMULATION. THE WINDS WILL
CONTINUE TO SHIFT MORE NORTHERLY FRIDAY MORNING AND LIKELY REMAIN IN
THIS NORTH DIRECTION FOR MUCH OF FRIDAY. THIS ORIENTATION WILL
COINCIDE WITH VERY STRONG WINDS...WITH GUSTS ANTICIPATED TO BE
AROUND 40 KT. CONDITIONS SHOULD BE BACK TO VFR FOR THE REMAINDER OF
THE DAY/FORECAST PERIOD...BUT A TREND BACK TOWARDS DETERIORATING
CONDITIONS COULD BE POSSIBLE IF LAKE EFFECT PRECIP AND CLOUD COVER
MOVE TOWARDS THE TERMINALS FRIDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF WIND DIRECTION AND SPEED/GUSTS...MEDIUM HIGH
  CONFIDENCE OF EXACT TIMING OF FROPA.

* HIGH CONFIDENCE OF -SHRA/-SHSN...MEDIUM CONFIDENCE OF DURATION.

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

RODRIGUEZ

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WIND ADVISORY...ILZ014...7 AM FRIDAY TO 10 PM FRIDAY.

     LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WIND ADVISORY...ILZ005-ILZ006-ILZ012-ILZ013-ILZ020-ILZ022...7 AM
     FRIDAY TO 7 PM FRIDAY.

     WIND ADVISORY...ILZ023-ILZ033...10 AM FRIDAY TO 7 PM FRIDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

     WINTER WEATHER ADVISORY...INZ001-INZ002-INZ010-INZ011...10 AM
     FRIDAY TO 10 PM FRIDAY.

     WIND ADVISORY...INZ019...10 AM FRIDAY TO 7 PM FRIDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...7 PM FRIDAY TO
     4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...3 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ563...1 AM FRIDAY TO 10
     PM FRIDAY.

     GALE WARNING...LMZ740...4 AM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM FRIDAY
     TO 7 PM FRIDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 301951
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 PM CDT THU OCT 30 2014

.UPDATE...
1059 AM CDT

GOING FORECAST FOR THE REST OF TODAY LOOKS FAIRLY ON TRACK WITH
ONLY SMALL ADJUSTMENTS. THE EMPHASIS ON THE FORECAST CONTINUES TO
BE ON THE STRONG AUTUMN SYSTEM FRIDAY.

THE AREA FINDS ITSELF BETWEEN TWO SHORT WAVE DISTURBANCES LATE
THIS MORNING AND AS A RESULT A THINNING IN CLOUD COVER HAS BEEN
SEEN ACROSS NORTHEAST IL AND NORTHWEST IN. EXPECTING VARIABILITY
IN SKY TO OCCUR THE REST OF THE DAY THAT WILL PROBABLY AVERAGE OUT
TO MOSTLY CLOUDY. THIS BREAK HAS ALLOWED TEMPERATURES IN SOME
PLACES TO OUTPACE PREVIOUS FORECAST AND HAVE ADJUSTED HIGHS UP A
DEGREE TO TWO IN EASTERN AREAS. WEAKER LESS ORGANIZED FORCING
BETWEEN THE TWO WAVES SHOULD CONTINUE TO KEEP ANY RAIN LIGHT OR
EVEN JUST SPRINKLES...WITH THE BETTER CHANCE FOR A FEW HUNDREDTHS
OF AN INCH BEING SOUTH OF I-80 WITH THE SOUTHERN DISTURBANCE THIS
AFTERNOON.

LOOKING AHEAD TO FRIDAY...THE WINDY DAY AND EVENING CONTINUES ON
TRACK WITH THE HIGHEST WIND SPEEDS AND IMPACTS BEING NEAR THE
LAKE SHORE. THE SETUP FOR LAKE EFFECT SNOW IS CONTINUING TO BE
WEIGHED AND MODEL DIFFERENCES DO EXIST IN THE LOWEST THERMAL
PROFILES. WITH LIKELY MODEST TO TEMPORARY HEAVY PRECIPITATION
RATES GIVEN THE HIGH LAKE-INDUCED INSTABILITY...COULD CERTAINLY
REALIZE PRETTY LOW VISIBILITY IN PARTS OF NORTHWEST INDIANA AND
POSSIBLY ALONG THE COOK COUNTY SHORE AT TIMES FRIDAY IF SNOW CAN
BE THE DOMINANT PRECIPITATION TYPE.

MTF

&&

.SHORT TERM...
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* NO ISSUES IN THE NEAR TERM.

* SOUTHWEST WINDS SHIFTING TO THE NORTHWEST WITH FROPA
  TONIGHT...WITH GUSTS INCREASING THROUGH MIDDAY FRIDAY WHILE
  BECOMING MORE NORTHERLY.

* CHANCE OF -SHRA/-SHSN TONIGHT THROUGH EARLY FRIDAY MORNING.

* MVFR CEILINGS LATE TONIGHT INTO FRIDAY MORNING.

RODRIGUEZ

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

RELATIVELY QUIET CONDITIONS EARLY THIS AFTERNOON WILL CONTINUE THIS
AFTERNOON...WHILE SOUTHWEST WINDS PREVAIL AND MID/HIGH LEVEL CLOUD
COVER CONTINUE TO STREAM OVERHEAD. CONDITIONS WILL BEGIN
DETERIORATING TONIGHT AS SYSTEM/FRONT PUSH THROUGH THE REGION. THE
CURRENT SOUTHWEST WINDS WILL TURN WEST AND NORTHWEST TONIGHT WITH
WIND SPEED/GUSTS QUICKLY INCREASING. LOWERING CEILINGS TO MVFR WILL
ALSO OCCUR WITH THE ARRIVAL OF THIS WIND SHIFT...LIKELY PERSISTING
FOR MUCH OF FRIDAY MORNING. MOISTURE WILL ALSO BE SUFFICIENT FOR
RAIN SHOWERS TO INITIALLY BE POSSIBLE BUT WITH MUCH COLDER AIR
QUICKLY FILTERING IN...SNOW SHOWERS WILL THEN BE POSSIBLE. EXPECT
THESE RAIN/SNOW SHOWERS TO BE ON THE LIGHTER SIDE...WITH NO VIS
RESTRICTION EXPECTED AS WELL AS NO SNOW ACCUMULATION. THE WINDS WILL
CONTINUE TO SHIFT MORE NORTHERLY FRIDAY MORNING AND LIKELY REMAIN IN
THIS NORTH DIRECTION FOR MUCH OF FRIDAY. THIS ORIENTATION WILL
COINCIDE WITH VERY STRONG WINDS...WITH GUSTS ANTICIPATED TO BE
AROUND 40 KT. CONDITIONS SHOULD BE BACK TO VFR FOR THE REMAINDER OF
THE DAY/FORECAST PERIOD...BUT A TREND BACK TOWARDS DETERIORATING
CONDITIONS COULD BE POSSIBLE IF LAKE EFFECT PRECIP AND CLOUD COVER
MOVE TOWARDS THE TERMINALS FRIDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF WIND DIRECTION AND SPEED/GUSTS...MEDIUM HIGH
  CONFIDENCE OF EXACT TIMING OF FROPA.

* HIGH CONFIDENCE OF -SHRA/-SHSN...MEDIUM CONFIDENCE OF DURATION.

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

RODRIGUEZ

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
250 PM CDT

A VERY ACTIVE PERIOD OVER LAKE MICHIGAN BEGINNING LATER TONIGHT. THE
AREA WILL FIND ITSELF IN A FAVORABLE AND ANOMALOUS SYNOPTIC WEATHER
PATTERN FOR STRONG NORTHERLY WINDS...AND THIS WILL BE FURTHER AIDED
BY THE WARM WATERS/EXTREME INSTABILITY TO PRODUCE REGULAR HIGHER END
STORM FORCE GUSTS PERSISTING INTO FRIDAY. A STRONG COLD FRONT WILL
MOVE DOWN THE LAKE RAPIDLY FROM AROUND MIDNIGHT THROUGH 5 AM.
IMMEDIATELY BEHIND THIS A VERY TIGHT PRESSURE GRADIENT IN SYNC WITH
COLD AIR ADVECTION WILL PRODUCE A RAMP UP IN NORTHERLY WIND SPEEDS.
THE HIGHEST WIND SPEEDS OF STORM FORCE TO 50 AND POSSIBLY EVEN 55 KT
ARE EXPECTED LATE TONIGHT THROUGH MID FRIDAY AFTERNOON FOR THE
CENTRAL AND SOUTHERN PART OF THE LAKE...AND AFTER DAYBREAK THROUGH
THE DAY ON FRIDAY FOR THE NEARSHORE AREAS OF ILLINOIS AND INDIANA.
THE WAVE MAXIMUM OF OVER 20 FOOTERS IS EXPECTED TO DEVELOP OVER THE
CENTRAL PART OF THE LAKE EARLY FRIDAY MORNING AND EVOLVE SOUTHWARD
REACHING THE ILLINOIS AND INDIANA NEARSHORE FRIDAY AFTERNOON AND
EARLY EVENING. WAVES WILL BE VERY SLOW TO SUBSIDE THROUGH LATE
FRIDAY NIGHT AND EARLY SATURDAY. HIGH PRESSURE WILL MOVE QUICKLY
OVER THE LAKE SATURDAY NIGHT BEFORE SOUTHERLY FLOW RETURNS TO THE
LAKE.

MTF

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...
LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 301821
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
120 PM CDT THU OCT 30 2014

.UPDATE...
1059 AM CDT

GOING FORECAST FOR THE REST OF TODAY LOOKS FAIRLY ON TRACK WITH
ONLY SMALL ADJUSTMENTS. THE EMPHASIS ON THE FORECAST CONTINUES TO
BE ON THE STRONG AUTUMN SYSTEM FRIDAY.

THE AREA FINDS ITSELF BETWEEN TWO SHORT WAVE DISTURBANCES LATE
THIS MORNING AND AS A RESULT A THINNING IN CLOUD COVER HAS BEEN
SEEN ACROSS NORTHEAST IL AND NORTHWEST IN. EXPECTING VARIABILITY
IN SKY TO OCCUR THE REST OF THE DAY THAT WILL PROBABLY AVERAGE OUT
TO MOSTLY CLOUDY. THIS BREAK HAS ALLOWED TEMPERATURES IN SOME
PLACES TO OUTPACE PREVIOUS FORECAST AND HAVE ADJUSTED HIGHS UP A
DEGREE TO TWO IN EASTERN AREAS. WEAKER LESS ORGANIZED FORCING
BETWEEN THE TWO WAVES SHOULD CONTINUE TO KEEP ANY RAIN LIGHT OR
EVEN JUST SPRINKLES...WITH THE BETTER CHANCE FOR A FEW HUNDREDTHS
OF AN INCH BEING SOUTH OF I-80 WITH THE SOUTHERN DISTURBANCE THIS
AFTERNOON.

LOOKING AHEAD TO FRIDAY...THE WINDY DAY AND EVENING CONTINUES ON
TRACK WITH THE HIGHEST WIND SPEEDS AND IMPACTS BEING NEAR THE
LAKE SHORE. THE SETUP FOR LAKE EFFECT SNOW IS CONTINUING TO BE
WEIGHED AND MODEL DIFFERENCES DO EXIST IN THE LOWEST THERMAL
PROFILES. WITH LIKELY MODEST TO TEMPORARY HEAVY PRECIPITATION
RATES GIVEN THE HIGH LAKE-INDUCED INSTABILITY...COULD CERTAINLY
REALIZE PRETTY LOW VISIBILITY IN PARTS OF NORTHWEST INDIANA AND
POSSIBLY ALONG THE COOK COUNTY SHORE AT TIMES FRIDAY IF SNOW CAN
BE THE DOMINANT PRECIPITATION TYPE.

MTF

&&

.SHORT TERM...
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* NO ISSUES IN THE NEAR TERM.

* SOUTHWEST WINDS SHIFTING TO THE NORTHWEST WITH FROPA
  TONIGHT...WITH GUSTS INCREASING THROUGH MIDDAY FRIDAY WHILE
  BECOMING MORE NORTHERLY.

* CHANCE OF -SHRA/-SHSN TONIGHT THROUGH EARLY FRIDAY MORNING.

* MVFR CEILINGS LATE TONIGHT INTO FRIDAY MORNING.

RODRIGUEZ

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

RELATIVELY QUIET CONDITIONS EARLY THIS AFTERNOON WILL CONTINUE THIS
AFTERNOON...WHILE SOUTHWEST WINDS PREVAIL AND MID/HIGH LEVEL CLOUD
COVER CONTINUE TO STREAM OVERHEAD. CONDITIONS WILL BEGIN
DETERIORATING TONIGHT AS SYSTEM/FRONT PUSH THROUGH THE REGION. THE
CURRENT SOUTHWEST WINDS WILL TURN WEST AND NORTHWEST TONIGHT WITH
WIND SPEED/GUSTS QUICKLY INCREASING. LOWERING CEILINGS TO MVFR WILL
ALSO OCCUR WITH THE ARRIVAL OF THIS WIND SHIFT...LIKELY PERSISTING
FOR MUCH OF FRIDAY MORNING. MOISTURE WILL ALSO BE SUFFICIENT FOR
RAIN SHOWERS TO INITIALLY BE POSSIBLE BUT WITH MUCH COLDER AIR
QUICKLY FILTERING IN...SNOW SHOWERS WILL THEN BE POSSIBLE. EXPECT
THESE RAIN/SNOW SHOWERS TO BE ON THE LIGHTER SIDE...WITH NO VIS
RESTRICTION EXPECTED AS WELL AS NO SNOW ACCUMULATION. THE WINDS WILL
CONTINUE TO SHIFT MORE NORTHERLY FRIDAY MORNING AND LIKELY REMAIN IN
THIS NORTH DIRECTION FOR MUCH OF FRIDAY. THIS ORIENTATION WILL
COINCIDE WITH VERY STRONG WINDS...WITH GUSTS ANTICIPATED TO BE
AROUND 40 KT. CONDITIONS SHOULD BE BACK TO VFR FOR THE REMAINDER OF
THE DAY/FORECAST PERIOD...BUT A TREND BACK TOWARDS DETERIORATING
CONDITIONS COULD BE POSSIBLE IF LAKE EFFECT PRECIP AND CLOUD COVER
MOVE TOWARDS THE TERMINALS FRIDAY EVENING.

RODRIGUEZ

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

* HIGH CONFIDENCE OF VFR CONDITIONS IN THE NEAR TERM.

* HIGH CONFIDENCE OF WIND DIRECTION AND SPEED/GUSTS...MEDIUM HIGH
  CONFIDENCE OF EXACT TIMING OF FROPA.

* HIGH CONFIDENCE OF -SHRA/-SHSN...MEDIUM CONFIDENCE OF DURATION.

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

RODRIGUEZ

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...
LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 301604
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1104 AM CDT THU OCT 30 2014

.UPDATE...
1059 AM CDT

GOING FORECAST FOR THE REST OF TODAY LOOKS FAIRLY ON TRACK WITH
ONLY SMALL ADJUSTMENTS. THE EMPHASIS ON THE FORECAST CONTINUES TO
BE ON THE STRONG AUTUMN SYSTEM FRIDAY.

THE AREA FINDS ITSELF BETWEEN TWO SHORT WAVE DISTURBANCES LATE
THIS MORNING AND AS A RESULT A THINNING IN CLOUD COVER HAS BEEN
SEEN ACROSS NORTHEAST IL AND NORTHWEST IN. EXPECTING VARIABILITY
IN SKY TO OCCUR THE REST OF THE DAY THAT WILL PROBABLY AVERAGE OUT
TO MOSTLY CLOUDY. THIS BREAK HAS ALLOWED TEMPERATURES IN SOME
PLACES TO OUTPACE PREVIOUS FORECAST AND HAVE ADJUSTED HIGHS UP A
DEGREE TO TWO IN EASTERN AREAS. WEAKER LESS ORGANIZED FORCING
BETWEEN THE TWO WAVES SHOULD CONTINUE TO KEEP ANY RAIN LIGHT OR
EVEN JUST SPRINKLES...WITH THE BETTER CHANCE FOR A FEW HUNDREDTHS
OF AN INCH BEING SOUTH OF I-80 WITH THE SOUTHERN DISTURBANCE THIS
AFTERNOON.

LOOKING AHEAD TO FRIDAY...THE WINDY DAY AND EVENING CONTINUES ON
TRACK WITH THE HIGHEST WIND SPEEDS AND IMPACTS BEING NEAR THE
LAKE SHORE. THE SETUP FOR LAKE EFFECT SNOW IS CONTINUING TO BE
WEIGHED AND MODEL DIFFERENCES DO EXIST IN THE LOWEST THERMAL
PROFILES. WITH LIKELY MODEST TO TEMPORARY HEAVY PRECIPITATION
RATES GIVEN THE HIGH LAKE-INDUCED INSTABILITY...COULD CERTAINLY
REALIZE PRETTY LOW VISIBILITY IN PARTS OF NORTHWEST INDIANA AND
POSSIBLY ALONG THE COOK COUNTY SHORE AT TIMES FRIDAY IF SNOW CAN
BE THE DOMINANT PRECIPITATION TYPE.

MTF

&&

.SHORT TERM...
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

* CHANCE SHRA WITH THE PASSAGE OF THE COLD FRONT.

KREIN/RODRIGUEZ

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

CONDITIONS WILL BE QUIET AT THE TERMINALS THROUGH MUCH OF THE
PERIOD...BUT A STRONG COLD FRONT MOVING THROUGH THE REGION LATE
TONIGHT WILL BRING STRONG NORTH WINDS.

HOWEVER...THIS MORNING...A MID LEVEL IMPULSE CROSSING THE MIDDLE
MISSISSIPPI VALLEY IS BRINGING INCREASING MID AND HIGH CLOUDINESS.
LATEST RADAR IMAGERY SHOWS SOME SCT SHRA OVER IOWA AND MISSOURI
ASSOCIATED WITH THIS SYSTEM...BUT WITH A VERY DRY AIRMASS IN
PLACE...DO NOT EXPECT ANY PCPN AT THE TERMINALS.  WITH SFC HIGH
PRESSURE CENTERED OVER SRN IL/IN...WINDS WILL BE LIGHT AND
VARIABLE INITIALLY...BUT AS THE HIGH SLIDES OFF TO THE
SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE DAY AND
INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANGE IS EXPECTED LATE TONIGHT AS A STRONG COLD FRONT
PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS THAT
THE FRONT WILL PUSH THROUGH RFD BY EARLY EVENING...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS SHORTLY
THEREAFTER. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY. AS COLD ADVECTION AND STRONG PRESSURE RISES
DEVELOP BEHIND THE FROM...WINDS WILL STRENGTHEN WITH GUSTS UP TO
35-40 KT FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF
MOISTURE WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP
TO LOWER END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA
FOLLOWING THE FROPA FOR A BRIEF PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

* LOW CONFIDENCE IN TIMING AND COVERAGE OF PCPN WITH THE FROPA.

KREIN/RODRIGUEZ

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
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000
FXUS63 KLOT 301601
AFDLOT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1101 AM CDT THU OCT 30 2014

.UPDATE...
1059 AM CDT

GOING FORECAST FOR THE REST OF TODAY LOOKS FAIRLY ON TRACK WITH
ONLY SMALL ADJUSTMENTS. THE EMPHASIS ON THE FORECAST CONTINUES TO
BE ON THE STRONG AUTUMN SYSTEM FRIDAY.

THE AREA FINDS ITSELF BETWEEN TWO SHORT WAVE DISTURBANCES LATE
THIS MORNING AND AS A RESULT A THINNING IN CLOUD COVER HAS BEEN
SEEN ACROSS NORTHEAST IL AND NORTHWEST IN. EXPECTING VARIABILITY
IN SKY TO OCCUR THE REST OF THE DAY THAT WILL PROBABLY AVERAGE OUT
TO MOSTLY CLOUDY. THIS BREAK HAS ALLOWED TEMPERATURES IN SOME
PLACES TO OUTPACE PREVIOUS FORECAST AND HAVE ADJUSTED HIGHS UP A
DEGREE TO TWO IN EASTERN AREAS. WEAKER LESS ORGANIZED FORCING
BETWEEN THE TWO WAVES SHOULD CONTINUE TO KEEP ANY RAIN LIGHT OR
EVEN JUST SPRINKLES...WITH THE BETTER CHANCE FOR A FEW HUNDREDTHS
OF AN INCH BEING SOUTH OF I-80 WITH THE SOUTHERN DISTURBANCE THIS
AFTERNOON.

LOOKING AHEAD TO FRIDAY...THE WINDY DAY AND EVENING CONTINUES ON
TRACK WITH THE HIGHEST WIND SPEEDS AND IMPACTS BEING NEAR THE
LAKE SHORE. THE SETUP FOR LAKE EFFECT SNOW IS CONTINUING TO BE
WEIGHED AND MODEL DIFFERENCES DO EXIST IN THE LOWEST THERMAL
PROFILES. WITH LIKELY MODEST TO TEMPORARY HEAVY PRECIPITATION
RATES GIVEN THE HIGH LAKE-INDUCED INSTABILITY...COULD CERTAINLY
REALIZE PRETTY LOW VISIBILITY IN PARTS OF NORTHWEST INDIANA AND
POSSIBLY ALONG THE COOK COUNTY SHORE AT TIMES FRIDAY IF SNOW CAN
BE THE DOMINANT PRECIPITATION TYPE.

MTF

&&

.SHORT TERM...
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

* CHANCE SHRA WITH THE PASSAGE OF THE COLD FRONT.

KREIN/RODRIGUEZ

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

CONDITIONS WILL BE QUIET AT THE TERMINALS THROUGH MUCH OF THE
PERIOD...BUT A STRONG COLD FRONT MOVING THROUGH THE REGION LATE
TONIGHT WILL BRING STRONG NORTH WINDS.

HOWEVER...THIS MORNING...A MID LEVEL IMPULSE CROSSING THE MIDDLE
MISSISSIPPI VALLEY IS BRINGING INCREASING MID AND HIGH CLOUDINESS.
LATEST RADAR IMAGERY SHOWS SOME SCT SHRA OVER IOWA AND MISSOURI
ASSOCIATED WITH THIS SYSTEM...BUT WITH A VERY DRY AIRMASS IN
PLACE...DO NOT EXPECT ANY PCPN AT THE TERMINALS.  WITH SFC HIGH
PRESSURE CENTERED OVER SRN IL/IN...WINDS WILL BE LIGHT AND
VARIABLE INITIALLY...BUT AS THE HIGH SLIDES OFF TO THE
SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE DAY AND
INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANGE IS EXPECTED LATE TONIGHT AS A STRONG COLD FRONT
PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS THAT
THE FRONT WILL PUSH THROUGH RFD BY EARLY EVENING...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS SHORTLY
THEREAFTER. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY. AS COLD ADVECTION AND STRONG PRESSURE RISES
DEVELOP BEHIND THE FROM...WINDS WILL STRENGTHEN WITH GUSTS UP TO
35-40 KT FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF
MOISTURE WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP
TO LOWER END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA
FOLLOWING THE FROPA FOR A BRIEF PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

* LOW CONFIDENCE IN TIMING AND COVERAGE OF PCPN WITH THE FROPA.

KREIN/RODRIGUEZ

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 301416
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
916 AM CDT THU OCT 30 2014

.SHORT TERM...
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

* CHANCE SHRA WITH THE PASSAGE OF THE COLD FRONT.

KREIN/RODRIGUEZ

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

CONDITIONS WILL BE QUIET AT THE TERMINALS THROUGH MUCH OF THE
PERIOD...BUT A STRONG COLD FRONT MOVING THROUGH THE REGION LATE
TONIGHT WILL BRING STRONG NORTH WINDS.

HOWEVER...THIS MORNING...A MID LEVEL IMPULSE CROSSING THE MIDDLE
MISSISSIPPI VALLEY IS BRINGING INCREASING MID AND HIGH CLOUDINESS.
LATEST RADAR IMAGERY SHOWS SOME SCT SHRA OVER IOWA AND MISSOURI
ASSOCIATED WITH THIS SYSTEM...BUT WITH A VERY DRY AIRMASS IN
PLACE...DO NOT EXPECT ANY PCPN AT THE TERMINALS.  WITH SFC HIGH
PRESSURE CENTERED OVER SRN IL/IN...WINDS WILL BE LIGHT AND
VARIABLE INITIALLY...BUT AS THE HIGH SLIDES OFF TO THE
SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE DAY AND
INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANGE IS EXPECTED LATE TONIGHT AS A STRONG COLD FRONT
PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS THAT
THE FRONT WILL PUSH THROUGH RFD BY EARLY EVENING...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS SHORTLY
THEREAFTER. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY. AS COLD ADVECTION AND STRONG PRESSURE RISES
DEVELOP BEHIND THE FROM...WINDS WILL STRENGTHEN WITH GUSTS UP TO
35-40 KT FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF
MOISTURE WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP
TO LOWER END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA
FOLLOWING THE FROPA FOR A BRIEF PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

* LOW CONFIDENCE IN TIMING AND COVERAGE OF PCPN WITH THE FROPA.

KREIN/RODRIGUEZ

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 301132
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
632 AM CDT THU OCT 30 2014

.SHORT TERM...
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

* CHANCE SHRA WITH THE PASSAGE OF THE COLD FRONT.

KREIN

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

CONDITIONS WILL BE QUIET AT THE TERMINALS THROUGH MUCH OF THE
PERIOD...BUT A STRONG COLD FRONT MOVING THROUGH THE REGION LATE
TONIGHT WILL BRING STRONG NORTH WINDS.

HOWEVER...THIS MORNING...A MID LEVEL IMPULSE CROSSING THE MIDDLE
MISSISSIPPI VALLEY IS BRINGING INCREASING MID AND HIGH CLOUDINESS.
LATEST RADAR IMAGERY SHOWS SOME SCT SHRA OVER IOWA AND MISSOURI
ASSOCIATED WITH THIS SYSTEM...BUT WITH A VERY DRY AIRMASS IN
PLACE...DO NOT EXPECT ANY PCPN AT THE TERMINALS.  WITH SFC HIGH
PRESSURE CENTERED OVER SRN IL/IN...WINDS WILL BE LIGHT AND
VARIABLE INITIALLY...BUT AS THE HIGH SLIDES OFF TO THE
SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE DAY AND
INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANGE IS EXPECTED LATE TONIGHT AS A STRONG COLD FRONT
PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS THAT
THE FRONT WILL PUSH THROUGH RFD BY EARLY EVENING...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS SHORTLY
THEREAFTER. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY. AS COLD ADVECTION AND STRONG PRESSURE RISES
DEVELOP BEHIND THE FROM...WINDS WILL STRENGTHEN WITH GUSTS UP TO
35-40 KT FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF
MOISTURE WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP
TO LOWER END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA
FOLLOWING THE FROPA FOR A BRIEF PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

* LOW CONFIDENCE IN TIMING AND COVERAGE OF PCPN WITH THE FROPA.

KREIN

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

* FRIDAY NIGHT...STRONG NORTH WINDS GUSTING TO 30 KT. CHANCE OF
  SHRA OR SHSN.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS 10-15KT.

* SUNDAY...VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.

* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

* WEDNESDAY...VFR. WX NIL. SOUTHWEST WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 300857
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
357 AM CDT THU OCT 30 2014

.SHORT TERM...
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

* CHANCE SHRA WITH THE PASSAGE OF THE COLD FRONT.

KREIN

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

THE REMAINDER OF THE NIGHT AND THROUGH MUCH DAY THURSDAY...
CONDITIONS WILL BE QUIET AT THE TERMINALS. THE STRATOCU DECK HAS
PUSHED WELL TO THE EAST...LEAVING MOSTLY CLEAR SKIES TO START THE
PERIOD. LATEST SATELLITE IMAGERY SHOWS AN AREA OF MID AND HIGH
CLOUD CROSSING THE UPPER MISSISSIPPI VALLEY ASSOCIATED WITH A MID
LEVEL IMPULSE...WHICH WILL OVERSPREAD THE TERMINALS FOR THE
REMAINDER OF THE OVERNIGHT HOURS. WITH SFC HIGH PRESSURE CENTERED
OVER NRN IL...WINDS WILL BE LIGHT AND VARIABLE FOR THE REMAINDER
OF THE NIGHT AND INTO TOMORROW MORNING. AS THE HIGH SLIDES OFF TO
THE SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE
DAY AND INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANCE IS EXPECTED LATE TOMORROW NIGHT AS A STRONG COLD
FRONT PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS
THAT THE FRONT WILL PUSH THROUGH RFD BY ARND 04Z...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS BY
05-06Z. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY AND STRENGTHEN WITH GUSTS UP TO 30KT
FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF MOISTURE
WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP TO LOWER
END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA FOLLOWING THE
FROPA FOR A BRIEF PERIOD...BUT HAVE LOW CONFIDENCE IN THE TIMING
AND COVERAGE OF PCPN...SO WILL LEAVE ANY MENTION OF PCPN OUT OF
THE TAFS FOR NOW AND RE-EVALUATE WITH LATER UPDATES.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

* LOW CONFIDENCE IN TIMING AND COVERAGE OF PCPN WITH THE FROPA.

KREIN

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-
     LMZ876-LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 300846
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
346 AM CDT THU OCT 30 2014

.SHORT TERM...(THROUGH TONIGHT)
343 AM CDT

FOR THE REMAINDER OF THE NIGHT AND INTO THURSDAY MORNING...WEATHER
CONDITIONS WILL REMAIN QUIET ACROSS THE REGION UNTIL A STRONG COLD
FRONT SWEEPS THROUGH THE AREA LATE TONIGHT.

UNDER CLEAR SKIES AND WITH DEWPOINTS IN THE MIDDLE 20S TO LOWER
30S...TEMPERATURES ACROSS THE REGION HAVE BEEN DROPPING FAST
OVERNIGHT UNDER FAVORABLE RADIATIVE COOLING.  HOWEVER...A WEAK
SHORTWAVE DROPPING SEWD THROUGH THE NRN PLAINS AND ACROSS THE MIDDLE
AND UPPER MISSISSIPPI VALLEY WILL BRING INCREASING MID AND HIGH
LEVEL CLOUDINESS...THROUGH THE EARLY MORNING HOURS...TEMPERING THE
TEMPERATURE DROP OFF.  HOWEVER...OVERNIGHT LOW TEMPERATURES WILL
STILL  DROP INTO THE UPPER 20S TO LOWER 30S ACROSS THE AREA AWAY
FROM THE CHICAGO METRO AREA URBAN HEAT ISLAND...WHERE TEMPERATURES
WILL ONLY DROP INTO THE  UPPER 30S TO LOWER 40S.  AT THE
SURFACE...HIGH PRESSURE IS SLIDING SEWD ACROSS THE REGION...KEEPING
WINDS NEAR CALM.  AS THE HIGH SLIDES INTO THE OHIO VALLEY LATER
TODAY...WINDS WILL BECOME MORE WLY...BUT WITH A WEAK GRADIENT IN
PLACE...WINDS SHOULD REMAIN LIGHT THROUGH THE DAY AND INTO THE EARLY
EVENING.  WITH HEIGHT FALLS ASSOCIATED WITH THE PASSAGE OF THE
SHORTWAVE AND A GENERAL COLD ADVECTIVE PATTERN IN PLACE
ALOFT...ANTICIPATE ANOTHER CHILLY DAY WITH HIGHS ONLY IN THE LOWER
TO MIDDLE 50S.

A STRONG COLD FRONT IS EXPECTED TO DROP OUT OF THE NRN PLAINS AND
PUSH INTO NWRN IL BY AROUND MIDNIGHT AND THE QUICKLY PUSH SEWD
ACROSS THE REGION...BRINGING A QUICK WIND SHIFT TO NWLY.  STRONG
COLD ADVECTION AND STRONG PRESSURE RISES OF 6MB/6HR WILL BRING
STRONG...GUSTY WINDS. LATEST FORECAST SOUNDING SHOW WINDS ARND 30
MPH AT THE TOP OF THE MIXED LAYER OVER LAND...WHICH WOULD
SUPPORT GUSTS NEAR 30 MPH AT THE SFC BY ARND DAYBREAK FRIDAY
MORNING.

KREIN

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

KREIN

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

THE REMAINDER OF THE NIGHT AND THROUGH MUCH DAY THURSDAY...
CONDITIONS WILL BE QUIET AT THE TERMINALS. THE STRATOCU DECK HAS
PUSHED WELL TO THE EAST...LEAVING MOSTLY CLEAR SKIES TO START THE
PERIOD. LATEST SATELLITE IMAGERY SHOWS AN AREA OF MID AND HIGH
CLOUD CROSSING THE UPPER MISSISSIPPI VALLEY ASSOCIATED WITH A MID
LEVEL IMPULSE...WHICH WILL OVERSPREAD THE TERMINALS FOR THE
REMAINDER OF THE OVERNIGHT HOURS. WITH SFC HIGH PRESSURE CENTERED
OVER NRN IL...WINDS WILL BE LIGHT AND VARIABLE FOR THE REMAINDER
OF THE NIGHT AND INTO TOMORROW MORNING. AS THE HIGH SLIDES OFF TO
THE SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE
DAY AND INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANCE IS EXPECTED LATE TOMORROW NIGHT AS A STRONG COLD
FRONT PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS
THAT THE FRONT WILL PUSH THROUGH RFD BY ARND 04Z...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS BY
05-06Z. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY AND STRENGTHEN WITH GUSTS UP TO 30KT
FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF MOISTURE
WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP TO LOWER
END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA FOLLOWING THE
FROPA FOR A BRIEF PERIOD...BUT HAVE LOW CONFIDENCE IN THE TIMING
AND COVERAGE OF PCPN...SO WILL LEAVE ANY MENTION OF PCPN OUT OF
THE TAFS FOR NOW AND RE-EVALUATE WITH LATER UPDATES.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

KREIN

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...4 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 300819
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
319 AM CDT THU OCT 30 2014

.SHORT TERM...

FORTHCOMING...

IZZI

&&

.LONG TERM...
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

KREIN

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

THE REMAINDER OF THE NIGHT AND THROUGH MUCH DAY THURSDAY...
CONDITIONS WILL BE QUIET AT THE TERMINALS. THE STRATOCU DECK HAS
PUSHED WELL TO THE EAST...LEAVING MOSTLY CLEAR SKIES TO START THE
PERIOD. LATEST SATELLITE IMAGERY SHOWS AN AREA OF MID AND HIGH
CLOUD CROSSING THE UPPER MISSISSIPPI VALLEY ASSOCIATED WITH A MID
LEVEL IMPULSE...WHICH WILL OVERSPREAD THE TERMINALS FOR THE
REMAINDER OF THE OVERNIGHT HOURS. WITH SFC HIGH PRESSURE CENTERED
OVER NRN IL...WINDS WILL BE LIGHT AND VARIABLE FOR THE REMAINDER
OF THE NIGHT AND INTO TOMORROW MORNING. AS THE HIGH SLIDES OFF TO
THE SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE
DAY AND INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANCE IS EXPECTED LATE TOMORROW NIGHT AS A STRONG COLD
FRONT PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS
THAT THE FRONT WILL PUSH THROUGH RFD BY ARND 04Z...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS BY
05-06Z. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY AND STRENGTHEN WITH GUSTS UP TO 30KT
FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF MOISTURE
WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP TO LOWER
END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA FOLLOWING THE
FROPA FOR A BRIEF PERIOD...BUT HAVE LOW CONFIDENCE IN THE TIMING
AND COVERAGE OF PCPN...SO WILL LEAVE ANY MENTION OF PCPN OUT OF
THE TAFS FOR NOW AND RE-EVALUATE WITH LATER UPDATES.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

KREIN

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
319 AM CDT

SHARP UPPER TROUGH WILL DIG INTO THE WESTERN GREAT LAKES REGION
TONIGHT AND RESULT IN SURFACE LOW DEVELOPING AND SLOWLY INTENSIFYING
TONIGHT INTO FRIDAY OVER THE EASTERN LAKES. MEANWHILE...UPSTREAM
HIGH PRESSURE OVER THE CANADIAN PRAIRIES WILL STRENGTHEN AS IT MOVES
SOUTHEAST INTO THE NORTHERN PLAINS TONIGHT INTO FRIDAY. THE RESULT
WILL BE A VERY TIGHT PRESSURE GRADIENT DEVELOPING OVER THE AREA
LATER TONIGHT INTO FRIDAY AND WHEN COMBINED WITH THE EXTREME
INSTABILITY LIKELY TO DEVELOP AS A RESULT OF THE VERY COLD AIR ALOFT
MOVING IN...AM EXPECTING A PERIOD OF HIGH END GALES TO LOW END STORM
FORCE WINDS OVER THE LAKE LATE TONIGHT THROUGH FRIDAY NIGHT. CURRENT
INDICATIONS ARE THAT THE LONGEST DURATION AND HIGHEST PROBABILITY OF
STORM FORCE WINDS WILL EXIST OVER SOUTHERN LAKE MICHIGAN AND HAVE
OPTED TO UPGRADE TO A STORM WARNING THERE FOR FRIDAY...INCLUDING THE
NORTHWEST INDIANA NEARSHORE WATERS UP TO NORTHERLY ISLAND IN THE
ILLINOIS NEARSHORE. THE NORTHERN PORTIONS OF THE ILLINOIS NEARSHORE
MAY END UP WITH A MORE OFFSHORE FETCH IN THE 350-360 RANGE LESSENING
THE THREAT OF STORM FORCE WINDS A BIT. NORTHERN PORTIONS OF THE LAKE
COULD SEE STORM FORCE GUSTS FOR A TIME FRIDAY MORNING BUT DURATION
LOOKS TO BE LESS AND CONFIDENCE LOWER...SO JUST HINTED AT THIS
THREAT IN THE GLF. FULL FETCH NORTH STORM FORCE WINDS SHOULD HAVE NO
PROBLEM KICKING WAVES UP TO AROUND OR JUST ABOVE 20 FT OVER SOUTHERN
PORTIONS OF THE LAKE FRIDAY AFTERNOON AND EVENING. WINDS SHOULD
SUBSIDE RATHER QUICKLY FRIDAY NIGHT INTO SATURDAY AS THE PATTERN
REMAINS PROGRESSIVE AND THE HIGH PRESSURE RESPONSIBLE FOR THE STORM
EVENT MOVES INTO THE WESTERN LAKES REGION ALLOWING WINDS AND
EVENTUALLY WAVES TO SUBSIDE SATURDAY. LATER SUNDAY INTO EARLY NEXT
WEEK 25-30KT SOUTHERLY WINDS COULD DEVELOP AS HIGH PUSHES OFF TO THE
EAST AND NEW LOW PRESSURE DEVELOPS OVER THE NORTHERN PLAINS.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740-LMZ741...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 300809
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
309 AM CDT THU OCT 30 2014

.SHORT TERM...(THROUGH TONIGHT)

FORTHCOMING...

IZZI

&&

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
308 AM CDT

STRONG UPPER TROUGH/CLOSED LOW WILL CONTINUE TO DIG SOUTH THROUGH
THE WESTERN LAKES REGION FRIDAY. STRONG COLD AIR ADVECTION AND
TIGHTENING PRESSURE GRADIENT BETWEEN DEVELOPING SFC LOW TO OUR EAST
AND STRENGTHENING SFC HIGH APPROACHING FROM THE NORTHWEST WILL
RESULT IN STRONG NORTHERLY WINDS FRIDAY...ESPECIALLY NEAR THE LAKE.
FORECAST SOUNDINGS SUPPORT GUSTS TO AROUND 40 MPH MOST AREAS
FRIDAY...THOUGH THE LESSER FRICTION AND STRONGER INSTABILITY AND
RESULTANT MIXING NEAR THE LAKE SHOULD SUPPORT WIND GUSTS OF 50+ MPH
NEAR THE LAKE...ESPECIALLY COOK COUNTY AND NW INDIANA SHORE. COULD
BE A MARGINAL HIGH WIND WARNING FOR LAKE SHORE AREAS WITH A SOLID
WIND ADVISORY EVENT LIKELY. GIVEN THE UNCERTAINTY OPTED TO HOLD OFF
ON HEADLINES FOR NOW AND WILL LET LATER SHIFTS DECIDE.

THE FULL FETCH STORM FORCE WINDS WILL RESULT IN 20FT+
WAVES...PARTICULARLY FOR COOK COUNTY INTO NW INDIANA GIVEN THE
350-360 WIND DIRECTION. LAKE LEVELS ARE NEARLY 2 FEET HIGHER THAN
LAST YEAR AND PREVIOUS YEARS...SO EVEN THOUGH WAVES WILL NOT BE
QUITE AS HIGH AS SANDY A FEW YEARS AGO...THE LAKE SHORE FLOODING
IMPACT COULD BE SIMILAR. HAVE GONE AHEAD AND ISSUED A LAKESHORE
FLOOD ADVISORY TO HIGHLIGHT THE LIKELY COASTAL INUNDATION IMPACT
FROM THE LARGE AND BATTERING WAVES.

COULD SEE SOME SHOWERS ALONG THE COLD FRONT TONIGHT...BUT FRONT
SHOULD CLEAR THE AREA BY FRIDAY MORNING WITH SYNOPTIC PRECIP THREAT
LARGELY ENDING. HOWEVER...VERY IMPRESSIVE LAKE EFFECT SET-UP LOOKS
TO DEVELOP FRIDAY INTO FRIDAY EVENING WITH VERY HIGH LAKE INDUCED
EQUILIBRIUM LEVELS UP TO AROUND 20KFT AND UP TO NEARLY -30C. GIVEN
THE LIKELY PRESENCE OF SUPER COOLED LIQUID IN THE CLOUDS AND HIGH
EQUILIBRIUM LEVELS IT SEEMS QUITE LIKELY THAT ISOLATED THUNDERSTORMS
WILL OCCUR IN ADDITION TO FAIRLY WIDESPREAD SHOWERS FRIDAY. THESE
EARLY SEASON LAKE EFFECT EVENTS ARE ALWAYS TRICKY WITH P-TYPE AS THE
VERY COLD AIR ALOFT...AROUND -8 TO -10C AT 850MB WOULD SOLIDLY
SUPPORT SNOW DESPITE WARM WATER TEMPS IN THE 50S STILL. HAVE GONE
WITH RAIN OR SNOW SHOWERS FOR NOW...BUT THINK THE FARTHER INLAND
AWAY FROM THE LAKE YOU GET THE BETTER CHANCE WILL BE FOR ALL SNOW
SHOWERS FRIDAY AFTERNOON AND EVENING INTO NW INDIANA. GIVEN THE
POTENTIAL FOR THUNDERSTORMS AND ADDED DYNAMIC COOLING AM CONCERNED
THAT SOME PORTIONS OF NW INDIANA...ESPECIALLY A BIT INLAND FROM THE
LAKE...COULD END UP WITH A SLUSHY COUPLE INCHES OF SNOW ACCUMULATION
ON GRASSY SURFACES BY FRIDAY EVENING...THOUGH CONFIDENCE IS TOO LOW
TO HIT THAT TOO HARD AT THIS TIME. LOW LEVEL FLOW SHOULD SLOWLY VEER
SO THAT THE FOCUS FOR LAKE EFFECT PRECIP SHOULD START IN PORTER
COUNTY EARLY FRIDAY AND GRADUALLY SHIFT WEST INTO LAKE COUNTY
INDIANA FRIDAY AFTERNOON AND POTENTIALLY INTO SOUTHEAST COOK COUNTY
FRIDAY EVENING BEFORE INVERSION HEIGHTS CRASH AND LAKE EFFECT WINDS
DOWN LATE FRIDAY NIGHT.

THE COMBINATION OF STRONG WINDS AND UNSEASONABLY COLD TEMPS WILL
SEND WIND CHILLS DROPPING INTO THE 20S DURING TRICK OR TREATING
HOURS FRIDAY EVENING...WITH EVEN LESS FAVORABLE TRICK OR TREATING
WEATHER IN NW INDIANA UNDER THE LAKE EFFECT RAIN/SNOW SHOWERS. AFTER
THE UNSEASONABLY COLD TEMPERATURES AND WIND CHILLS FRIDAY INTO
FRIDAY NIGHT...LOOK FOR QUIET CONDITIONS OVER THE WEEKEND WITH VERY
SLOWLY MODERATING TEMPERATURES. PROGRESSIVE PATTERN SHOULD RESULT IN
TRANSIENT RIDGE MOVING EAST OF THE AREA EARLY NEXT WEEK WITH NEXT
SYSTEM BRINGING THE POTENTIAL FOR SHOWERS MONDAY NIGHT INTO TUESDAY.
TEMPERATURES SHOULD BE CLOSER TO SEASONAL NORMAL NEXT WEEK RETURNING
TO WHAT WILL FEEL LIKE THE RATHER PLEASANT 50S FOLLOWING FRIDAY`S
FLIRTATION WITH WINTER-LIKE TEMPERATURES.

IZZI

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

KREIN

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

THE REMAINDER OF THE NIGHT AND THROUGH MUCH DAY THURSDAY...
CONDITIONS WILL BE QUIET AT THE TERMINALS. THE STRATOCU DECK HAS
PUSHED WELL TO THE EAST...LEAVING MOSTLY CLEAR SKIES TO START THE
PERIOD. LATEST SATELLITE IMAGERY SHOWS AN AREA OF MID AND HIGH
CLOUD CROSSING THE UPPER MISSISSIPPI VALLEY ASSOCIATED WITH A MID
LEVEL IMPULSE...WHICH WILL OVERSPREAD THE TERMINALS FOR THE
REMAINDER OF THE OVERNIGHT HOURS. WITH SFC HIGH PRESSURE CENTERED
OVER NRN IL...WINDS WILL BE LIGHT AND VARIABLE FOR THE REMAINDER
OF THE NIGHT AND INTO TOMORROW MORNING. AS THE HIGH SLIDES OFF TO
THE SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE
DAY AND INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANCE IS EXPECTED LATE TOMORROW NIGHT AS A STRONG COLD
FRONT PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS
THAT THE FRONT WILL PUSH THROUGH RFD BY ARND 04Z...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS BY
05-06Z. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY AND STRENGTHEN WITH GUSTS UP TO 30KT
FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF MOISTURE
WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP TO LOWER
END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA FOLLOWING THE
FROPA FOR A BRIEF PERIOD...BUT HAVE LOW CONFIDENCE IN THE TIMING
AND COVERAGE OF PCPN...SO WILL LEAVE ANY MENTION OF PCPN OUT OF
THE TAFS FOR NOW AND RE-EVALUATE WITH LATER UPDATES.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

KREIN

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014...11 AM FRIDAY TO 4 AM
     SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002...11 AM FRIDAY TO 4 AM
     SATURDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...7 PM FRIDAY TO 4 AM SATURDAY.

     STORM WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ742-LMZ743-
     LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-
     LMZ878...6 AM FRIDAY TO 7 PM FRIDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ740-LMZ741...6 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 300555
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1255 AM CDT THU OCT 30 2014

.DISCUSSION...
906 PM CDT

FOR EVENING UPDATE...

MINOR CHANGES TO GOING FORECAST TO LOWER MIN TEMPS A LITTLE OVER
NORTH CENTRAL IL...PARTICULARLY THE ROCK RIVER VALLEY...WHERE CLEAR
SKIES AND LIGHT WINDS IN VICINITY OF SFC RIDGE AXIS HAVE ALLOWED
STRONG RADIATIONAL COOLING AND A QUICK DROP IN TEMPS TO THE LOW-MID
30S. GIVEN PROXIMITY OF THE RIDGE AND CLEAR SKIES UNTIL EARLY
MORNING WHEN HIGH CLOUDS APPROACH FROM THE NORTHWEST...THINK A FEW
UPPER 20S LIKELY AT THE COOLER SPOTS IN THAT AREA.

OTHERWISE...MAINLY A FEW TWEAKS TO SKY COVER TO MATCH GOES 11-3.9
MICRON IMAGERY OF CLEARING ACROSS MUCH OF NORTHERN IL. NORTHWEST
INDIANA WILL BE A LITTLE SLOWER TO CLEAR BASED ON SATELLITE IMAGERY.
REMAINDER OF FORECAST LOOKS TO BE IN GOOD SHAPE WITH MOST ATTENTION
FOCUSED ON FRIDAYS IMPRESSIVE STORM SYSTEM.

RATZER

//PREV DISCUSSION...
330 PM CDT

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO BE WITH REGARDS
TO THE SIGNIFICANT STORM SYSTEM EXPECTED TO DEVELOP ACROSS THE GREAT
LAKES AND OHIO VALLEY FRIDAY. THIS SYSTEM PROMISES TO PRODUCE
STRONG WINDS FRIDAY...POSSIBLY IN EXCESS OF 50 MPH ACROSS PORTIONS
OF THE REGION. THERE IS ALSO A DECENT CHANCE FOR SOME RAIN AND
SNOW...ESPECIALLY ACROSS EASTERN SECTIONS OF THE REGION FRIDAY INTO
FRIDAY NIGHT.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON...ACROSS NORTH AMERICA...
INDICATES THE PRESENCE OF POTENT STORM SYSTEM DIGGING ACROSS THE
GULF OF ALASKA...WITH THE CENTER OF CIRCULATION NEAR 53N 150W. THIS
SYSTEM WILL PLAY A MAJOR ROLE OVER THE NEXT 24 TO 36 HOURS IN
AMPLIFYING THE UPPER LEVEL FLOW PATTERN ACROSS NORTH AMERICA. MOST
NOTABLE WILL BE THE SHARPENING AND AMPLIFICATION OF AN UPPER LEVEL
RIDGE ACROSS THE INTER MOUNTAIN WEST AND HIGH PLAINS BY LATE
THURSDAY. THIS PARTICULAR PATTERN WILL FAVOR FALLING HEIGHTS AND THE
DEVELOPMENT OF STRONG NORTH-NORTHWEST ALOFT ACROSS THE GREAT LAKES
AND OHIO VALLEY REGIONS. MODEL GUIDANCE CONTINUES TO SUGGEST THAT
THIS EVOLVING LARGE SCALE WEATHER PATTERN WILL ACT TO STEER A
SHORTWAVE DISTURBANCE...CURRENTLY ACROSS NORTHERN SASKATCHEWAN AND
MANITOBA...SOUTHWARD RIGHT ACROSS THE AREA BY FRIDAY MORNING.

THE MAIN THREAT FOR ACTIVE WEATHER WILL BEGIN THURSDAY NIGHT AND
LAST INTO FRIDAY NIGHT. AS THE AFOREMENTIONED DISTURBANCE ACROSS
NORTHERN CANADA DIGS SOUTHWARD OVER WISCONSIN BY THURSDAY NIGHT...IT
WILL INDUCE AN AREA OF SURFACE LOW PRESSURE ACROSS LOWER MICHIGAN.
THIS SURFACE LOW IS OVERALL EXPECTED TO REMAIN FAIRLY WEAK (IN TERMS
OF CENTRAL PRESSURE) AS IT PROGRESSES SOUTHEASTWARD OVER THE OHIO
VALLEY LATER FRIDAY. AN ASSOCIATED COLD FRONT WILL BE DRIVEN ACROSS
THE AREA INTO EARLY FRIDAY MORNING...WITH STRONG COLD AIR ADVECTION
AND STRONG NORTHERLY WINDS EXPECTED IN ITS WAKE. IN SPITE OF THE
FACT THAT THE SURFACE LOW WILL REMAIN WEAK...THE SURFACE PRESSURE
GRADIENT IS EXPECTED TO BE QUITE STRONG ACROSS THE WESTERN LAKES
REGION AND INTO NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
FRIDAY...THANKS TO A STRONG 1033 MB HIGH THAT WILL BE RAPIDLY
BUILDING EASTWARD ACROSS THE UPPER MIDWEST. OVERALL...THIS LOOKS TO
SET UP TO STRONG PRESSURE RISES...POSSIBLY IN EXCESS OF 6 MB/6HR
PERIOD...ESPECIALLY ACROSS LAKE MICHIGAN AND ADJACENT AREAS OF
NORTHEASTERN ILLINOIS AND NORTHWESTERN INDIANA. THIS COMBINED WITH
THE STRONG PUSH OF MUCH COLDER AIR...SHOULD DRIVE SOME VERY STRONG
WINDS. MODEL SOUNDINGS INDICATE MEAN LAYER FLOW IN EXCESS OF 45 KT
OVER SOUTHERN LAKE MICHIGAN...WITH AROUND 50 KT OF FLOW AT THE TOP
OF THE MIXING LAYER. IT APPEARS THAT THE STRONGEST WINDS WITH THIS
SYSTEM WILL BE DURING THE LATE MORNING AND AFTERNOON ON FRIDAY
FOLLOWING THE PASSAGE OF THE UPPER LEVEL VORT MAX. THE TRACK OF THIS
SYSTEM ALSO SUGGESTS THAT THE STRONGEST WINDS WILL ALSO BE OVER
APPROXIMATELY THE EASTERN HALF OF MY CWA...ROUGHLY FROM THE CHICAGO
METRO AREA AND POINTS EASTWARD. THESE AREAS COULD REACH WIND
ADVISORY CRITERIA WITH WIND GUSTS UP TO 50 MPH.

THE STRONG NORTHERLY WINDS COMING IN OFF THE LAKE COULD ALLOW WIND
GUSTS TO APPROACH 50KT FOR AREAS NEAR THE LAKE SHORE...ESPECIALLY IN
NORTHWESTERN INDIANA. VERY HIGH CRASHING WAVES IN EXCESS OF 18 FT
ALSO APPEAR LIKELY FOR THE INDIANA AND PORTIONS OF THE ILLINOIS
SHORELINES...WHICH COULD RESULT IN SOME LAKE SHORE FLOODING CONCERNS
FRIDAY.

IT APPEARS MUCH OF THE PRECIPITATION WITH THIS SYSTEM WILL BE
FAVORED ACROSS AREAS NEAR THE LAKE ON FRIDAY AND FRIDAY EVENING.
HOWEVER...AS THE MAIN UPPER IMPULSE MOVES OVER THE AREA THURSDAY
NIGHT INTO EARLY FRIDAY...IT COULD DRIVE A SHORT PERIOD OF SHOWERS
ACROSS MUCH OF THE AREA. HOWEVER...DRIER AIR AND LARGE SCALE FORCING
FOR DECENT SHOULD OVERSPREAD MOST INLAND AREAS ACROSS NORTHERN
ILLINOIS BY FRIDAY AFTERNOON...LIKELY ENDING THE THREAT OF PRECIP.
HOWEVER...AREAS NEAR THE LAKE IN FAR NORTHEASTERN ILLINOIS AND MY
NORTHWESTERN INDIANA COUNTIES WILL LIKELY CONTINUE TO EXPERIENCE
PRECIPITATION FRIDAY AFTERNOON AND INTO THE EVENING AS THERMODYNAMICS
OVER LAKE MICHIGAN WILL BECOME VERY FAVORABLE FOR LAKE EFFECT
PRECIPITATION THROUGH FRIDAY EVENING. LAKE INDUCED EQUILIBRIUM LEVELS
LOOK TO EXCEED 16,000 FEET WITH LAKE SURFACE TEMPERATURE TO 850 MB
TEMPERATURE DIFFERENCES OF 18-19 DEGREES C. THE OVERALL DEPTH OF
THIS LAKE INDUCED INSTABILITY COULD ALSO ALLOW FOR SOME CHARGE
SEPARATION SUPPORTING THUNDER AND LIGHTENING ACROSS SOUTHERN
PORTIONS OF THE LAKE AND POSSIBLY INTO NORTHWESTERN INDIANA FRIDAY.
SO I HAVE INCLUDED A MENTION OF SUCH IN THE FORECAST.

THE MAIN QUESTION WITH THIS EVENT REMAINS AS TO WHEN THE PRECIP TYPE
COULD MIX WITH OR CHANGE TO SNOW. IT APPEARS THAT WITH 850 MB
TEMPERATURES AROUND -8 DEGREES C...THAT A TRANSITION OVER TO LAKE
EFFECT SNOW SHOWERS APPEARS TO BE A DECENT BET BY LATE FRIDAY
AFTERNOON AND INTO THE EVENING. HOWEVER...DUE TO THE POTENTIAL FOR
CONVECTIVELY DRIVEN HEAVY SHOWERS OVER THE LAKE...DYNAMIC COOLING
COULD BECOME STRONG ENOUGH TO RESULT IN AN EARLY TRANSITION TO SNOW
OVER NORTHWESTERN INDIANA. WITH THIS IN MIND CONFIDENCE ON TIMING OF
ANY TRANSITION TO SNOW ON FRIDAY IS LOW...THOUGH THERE IS THE
POTENTIAL FOR SOME HEAVIER RAIN/SNOW SHOWERS WHICH COULD RESULT IN
SOME ACCUMULATIONS ACROSS PORTIONS OF NORTHWESTERN INDIAN IN SPITE
OF WARM GROUND TEMPS. THE STRONG WINDS COULD ALSO ALLOW THESE
SHOWERS TO GET WELL INLAND ACROSS NORTHWESTERN INDIANA. THE THREAT
OF SNOW SHOULD COME TO END OVERNIGHT FRIDAY AS INVERSION HEIGHTS
TANK IN RESPONSE TO BUILDING UPPER LEVEL HEIGHTS AND WARMING MID
LEVEL TEMPERATURES.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY...THEN MODERATING TEMPERATURES ARE EXPECTED
INTO EARLY NEXT WEEK AS THE WESTERN CONUS UPPER RIDGE BUILDS
EASTWARD OVER THE REGION. ANOTHER COLD FRONT LOOKS TO TAKE AIM ON
THE AREA AROUND NEXT TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE
OF SHOWERS. OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING
THE LATER HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* TIMING OF COLD FRONT PASSAGE WITH WIND SHIFT TO NWLY...GUSTS TO
  30KT AND CIGS LOWERING TO MVFR AND CHANCE SHRA.

KREIN

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

THE REMAINDER OF THE NIGHT AND THROUGH MUCH DAY THURSDAY...
CONDITIONS WILL BE QUIET AT THE TERMINALS. THE STRATOCU DECK HAS
PUSHED WELL TO THE EAST...LEAVING MOSTLY CLEAR SKIES TO START THE
PERIOD. LATEST SATELLITE IMAGERY SHOWS AN AREA OF MID AND HIGH
CLOUD CROSSING THE UPPER MISSISSIPPI VALLEY ASSOCIATED WITH A MID
LEVEL IMPULSE...WHICH WILL OVERSPREAD THE TERMINALS FOR THE
REMAINDER OF THE OVERNIGHT HOURS. WITH SFC HIGH PRESSURE CENTERED
OVER NRN IL...WINDS WILL BE LIGHT AND VARIABLE FOR THE REMAINDER
OF THE NIGHT AND INTO TOMORROW MORNING. AS THE HIGH SLIDES OFF TO
THE SOUTHEAST...WINDS SHOULD BECOME MORE SWLY-WLY THROUGH THE
DAY AND INTO THE EVENING...WITH SPEEDS REMAINING LESS THAN 10KT.

AN ABRUPT CHANCE IS EXPECTED LATE TOMORROW NIGHT AS A STRONG COLD
FRONT PUSHES SOUTH ACROSS THE AREA. THE LATEST GUIDANCE SUGGESTS
THAT THE FRONT WILL PUSH THROUGH RFD BY ARND 04Z...AND THEN
QUICKLY PUSHING SOUTH THROUGH THE CHICAGO AREA TERMINALS BY
05-06Z. THIS WILL BE A VERY SHARP BOUNDARY AND WINDS SHOULD
QUICKLY SHIFT TO NWLY AND STRENGTHEN WITH GUSTS UP TO 30KT
FOLLOWING THE FROPA. THERE WILL ALSO BE A SHALLOW BAND OF MOISTURE
WITH THE FRONT...AND EXPECT THAT CIGS SHOULD QUICKLY DROP TO LOWER
END MVFR LEVELS. THERE IS A CHANCE FOR SOME SHRA FOLLOWING THE
FROPA FOR A BRIEF PERIOD...BUT HAVE LOW CONFIDENCE IN THE TIMING
AND COVERAGE OF PCPN...SO WILL LEAVE ANY MENTION OF PCPN OUT OF
THE TAFS FOR NOW AND RE-EVALUATE WITH LATER UPDATES.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS UP TO THE TIMING OF THE
  COLD FRONT PASSAGE THURSDAY NIGHT.

* HIGH CONFIDENCE IN THE IMPACTS OF THE FROPA ON TERMINAL
  CONDITIONS...BUT MEDIUM CONFIDENCE ON THE EXACT TIMING.

KREIN

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...4 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 300307
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1007 PM CDT WED OCT 29 2014

.DISCUSSION...
906 PM CDT

FOR EVENING UPDATE...

MINOR CHANGES TO GOING FORECAST TO LOWER MIN TEMPS A LITTLE OVER
NORTH CENTRAL IL...PARTICULARLY THE ROCK RIVER VALLEY...WHERE CLEAR
SKIES AND LIGHT WINDS IN VICINITY OF SFC RIDGE AXIS HAVE ALLOWED
STRONG RADIATIONAL COOLING AND A QUICK DROP IN TEMPS TO THE LOW-MID
30S. GIVEN PROXIMITY OF THE RIDGE AND CLEAR SKIES UNTIL EARLY
MORNING WHEN HIGH CLOUDS APPROACH FROM THE NORTHWEST...THINK A FEW
UPPER 20S LIKELY AT THE COOLER SPOTS IN THAT AREA.

OTHERWISE...MAINLY A FEW TWEAKS TO SKY COVER TO MATCH GOES 11-3.9
MICRON IMAGERY OF CLEARING ACROSS MUCH OF NORTHERN IL. NORTHWEST
INDIANA WILL BE A LITTLE SLOWER TO CLEAR BASED ON SATELLITE IMAGERY.
REMAINDER OF FORECAST LOOKS TO BE IN GOOD SHAPE WITH MOST ATTENTION
FOCUSED ON FRIDAYS IMPRESSIVE STORM SYSTEM.

RATZER

//PREV DISCUSSION...
330 PM CDT

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO BE WITH REGARDS
TO THE SIGNIFICANT STORM SYSTEM EXPECTED TO DEVELOP ACROSS THE GREAT
LAKES AND OHIO VALLEY FRIDAY. THIS SYSTEM PROMISES TO PRODUCE
STRONG WINDS FRIDAY...POSSIBLY IN EXCESS OF 50 MPH ACROSS PORTIONS
OF THE REGION. THERE IS ALSO A DECENT CHANCE FOR SOME RAIN AND
SNOW...ESPECIALLY ACROSS EASTERN SECTIONS OF THE REGION FRIDAY INTO
FRIDAY NIGHT.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON...ACROSS NORTH AMERICA...
INDICATES THE PRESENCE OF POTENT STORM SYSTEM DIGGING ACROSS THE
GULF OF ALASKA...WITH THE CENTER OF CIRCULATION NEAR 53N 150W. THIS
SYSTEM WILL PLAY A MAJOR ROLE OVER THE NEXT 24 TO 36 HOURS IN
AMPLIFYING THE UPPER LEVEL FLOW PATTERN ACROSS NORTH AMERICA. MOST
NOTABLE WILL BE THE SHARPENING AND AMPLIFICATION OF AN UPPER LEVEL
RIDGE ACROSS THE INTER MOUNTAIN WEST AND HIGH PLAINS BY LATE
THURSDAY. THIS PARTICULAR PATTERN WILL FAVOR FALLING HEIGHTS AND THE
DEVELOPMENT OF STRONG NORTH-NORTHWEST ALOFT ACROSS THE GREAT LAKES
AND OHIO VALLEY REGIONS. MODEL GUIDANCE CONTINUES TO SUGGEST THAT
THIS EVOLVING LARGE SCALE WEATHER PATTERN WILL ACT TO STEER A
SHORTWAVE DISTURBANCE...CURRENTLY ACROSS NORTHERN SASKATCHEWAN AND
MANITOBA...SOUTHWARD RIGHT ACROSS THE AREA BY FRIDAY MORNING.

THE MAIN THREAT FOR ACTIVE WEATHER WILL BEGIN THURSDAY NIGHT AND
LAST INTO FRIDAY NIGHT. AS THE AFOREMENTIONED DISTURBANCE ACROSS
NORTHERN CANADA DIGS SOUTHWARD OVER WISCONSIN BY THURSDAY NIGHT...IT
WILL INDUCE AN AREA OF SURFACE LOW PRESSURE ACROSS LOWER MICHIGAN.
THIS SURFACE LOW IS OVERALL EXPECTED TO REMAIN FAIRLY WEAK (IN TERMS
OF CENTRAL PRESSURE) AS IT PROGRESSES SOUTHEASTWARD OVER THE OHIO
VALLEY LATER FRIDAY. AN ASSOCIATED COLD FRONT WILL BE DRIVEN ACROSS
THE AREA INTO EARLY FRIDAY MORNING...WITH STRONG COLD AIR ADVECTION
AND STRONG NORTHERLY WINDS EXPECTED IN ITS WAKE. IN SPITE OF THE
FACT THAT THE SURFACE LOW WILL REMAIN WEAK...THE SURFACE PRESSURE
GRADIENT IS EXPECTED TO BE QUITE STRONG ACROSS THE WESTERN LAKES
REGION AND INTO NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
FRIDAY...THANKS TO A STRONG 1033 MB HIGH THAT WILL BE RAPIDLY
BUILDING EASTWARD ACROSS THE UPPER MIDWEST. OVERALL...THIS LOOKS TO
SET UP TO STRONG PRESSURE RISES...POSSIBLY IN EXCESS OF 6 MB/6HR
PERIOD...ESPECIALLY ACROSS LAKE MICHIGAN AND ADJACENT AREAS OF
NORTHEASTERN ILLINOIS AND NORTHWESTERN INDIANA. THIS COMBINED WITH
THE STRONG PUSH OF MUCH COLDER AIR...SHOULD DRIVE SOME VERY STRONG
WINDS. MODEL SOUNDINGS INDICATE MEAN LAYER FLOW IN EXCESS OF 45 KT
OVER SOUTHERN LAKE MICHIGAN...WITH AROUND 50 KT OF FLOW AT THE TOP
OF THE MIXING LAYER. IT APPEARS THAT THE STRONGEST WINDS WITH THIS
SYSTEM WILL BE DURING THE LATE MORNING AND AFTERNOON ON FRIDAY
FOLLOWING THE PASSAGE OF THE UPPER LEVEL VORT MAX. THE TRACK OF THIS
SYSTEM ALSO SUGGESTS THAT THE STRONGEST WINDS WILL ALSO BE OVER
APPROXIMATELY THE EASTERN HALF OF MY CWA...ROUGHLY FROM THE CHICAGO
METRO AREA AND POINTS EASTWARD. THESE AREAS COULD REACH WIND
ADVISORY CRITERIA WITH WIND GUSTS UP TO 50 MPH.

THE STRONG NORTHERLY WINDS COMING IN OFF THE LAKE COULD ALLOW WIND
GUSTS TO APPROACH 50KT FOR AREAS NEAR THE LAKE SHORE...ESPECIALLY IN
NORTHWESTERN INDIANA. VERY HIGH CRASHING WAVES IN EXCESS OF 18 FT
ALSO APPEAR LIKELY FOR THE INDIANA AND PORTIONS OF THE ILLINOIS
SHORELINES...WHICH COULD RESULT IN SOME LAKE SHORE FLOODING CONCERNS
FRIDAY.

IT APPEARS MUCH OF THE PRECIPITATION WITH THIS SYSTEM WILL BE
FAVORED ACROSS AREAS NEAR THE LAKE ON FRIDAY AND FRIDAY EVENING.
HOWEVER...AS THE MAIN UPPER IMPULSE MOVES OVER THE AREA THURSDAY
NIGHT INTO EARLY FRIDAY...IT COULD DRIVE A SHORT PERIOD OF SHOWERS
ACROSS MUCH OF THE AREA. HOWEVER...DRIER AIR AND LARGE SCALE FORCING
FOR DECENT SHOULD OVERSPREAD MOST INLAND AREAS ACROSS NORTHERN
ILLINOIS BY FRIDAY AFTERNOON...LIKELY ENDING THE THREAT OF PRECIP.
HOWEVER...AREAS NEAR THE LAKE IN FAR NORTHEASTERN ILLINOIS AND MY
NORTHWESTERN INDIANA COUNTIES WILL LIKELY CONTINUE TO EXPERIENCE
PRECIPITATION FRIDAY AFTERNOON AND INTO THE EVENING AS THERMODYNAMICS
OVER LAKE MICHIGAN WILL BECOME VERY FAVORABLE FOR LAKE EFFECT
PRECIPITATION THROUGH FRIDAY EVENING. LAKE INDUCED EQUILIBRIUM LEVELS
LOOK TO EXCEED 16,000 FEET WITH LAKE SURFACE TEMPERATURE TO 850 MB
TEMPERATURE DIFFERENCES OF 18-19 DEGREES C. THE OVERALL DEPTH OF
THIS LAKE INDUCED INSTABILITY COULD ALSO ALLOW FOR SOME CHARGE
SEPARATION SUPPORTING THUNDER AND LIGHTENING ACROSS SOUTHERN
PORTIONS OF THE LAKE AND POSSIBLY INTO NORTHWESTERN INDIANA FRIDAY.
SO I HAVE INCLUDED A MENTION OF SUCH IN THE FORECAST.

THE MAIN QUESTION WITH THIS EVENT REMAINS AS TO WHEN THE PRECIP TYPE
COULD MIX WITH OR CHANGE TO SNOW. IT APPEARS THAT WITH 850 MB
TEMPERATURES AROUND -8 DEGREES C...THAT A TRANSITION OVER TO LAKE
EFFECT SNOW SHOWERS APPEARS TO BE A DECENT BET BY LATE FRIDAY
AFTERNOON AND INTO THE EVENING. HOWEVER...DUE TO THE POTENTIAL FOR
CONVECTIVELY DRIVEN HEAVY SHOWERS OVER THE LAKE...DYNAMIC COOLING
COULD BECOME STRONG ENOUGH TO RESULT IN AN EARLY TRANSITION TO SNOW
OVER NORTHWESTERN INDIANA. WITH THIS IN MIND CONFIDENCE ON TIMING OF
ANY TRANSITION TO SNOW ON FRIDAY IS LOW...THOUGH THERE IS THE
POTENTIAL FOR SOME HEAVIER RAIN/SNOW SHOWERS WHICH COULD RESULT IN
SOME ACCUMULATIONS ACROSS PORTIONS OF NORTHWESTERN INDIAN IN SPITE
OF WARM GROUND TEMPS. THE STRONG WINDS COULD ALSO ALLOW THESE
SHOWERS TO GET WELL INLAND ACROSS NORTHWESTERN INDIANA. THE THREAT
OF SNOW SHOULD COME TO END OVERNIGHT FRIDAY AS INVERSION HEIGHTS
TANK IN RESPONSE TO BUILDING UPPER LEVEL HEIGHTS AND WARMING MID
LEVEL TEMPERATURES.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY...THEN MODERATING TEMPERATURES ARE EXPECTED
INTO EARLY NEXT WEEK AS THE WESTERN CONUS UPPER RIDGE BUILDS
EASTWARD OVER THE REGION. ANOTHER COLD FRONT LOOKS TO TAKE AIM ON
THE AREA AROUND NEXT TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE
OF SHOWERS. OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING
THE LATER HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NONE. CMS

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

BKN/OVC 4-5KFT CIGS WILL CONTINUE MOVING SOUTHEAST AND SCATTER OUT
THIS EVENING BUT WILL LIKELY TAKE A FEW MORE HOURS. ONCE THESE
CLOUDS SHIFT EAST...INCREASING HIGH CLOUDS OVERNIGHT TOWARD
MORNING WILL LOWER TO A MID DECK IN THE AFTERNOON AND THEN TO A
4-6KFT THURSDAY EVENING. A WEAK UPPER WAVE WILL MOVE ACROSS THE
REGION THURSDAY BRINGING A CHANCE OF SHOWERS THAT APPEAR TO STAY
JUST SOUTH OF THE TERMINALS...BUT SOME SPRINKLES OR AN ISOLATED
SHOWER IS POSSIBLE...ESPECIALLY BY THURSDAY EVENING.

WEST/NORTHWEST WINDS UNDER 10KTS WILL DIMINISH TO 5KT OR LESS THIS
EVENING AND TURN MORE SOUTHWEST OVERNIGHT...POSSIBLY BECOMING
LIGHT AND VARIABLE OR CALM IN SOME LOCATIONS. WINDS MAY TURN A BIT
MORE SOUTHERLY AFTER SUNRISE THEN SLOWLY TURN BACK WESTERLY BY
AFTERNOON AND NORTHWESTERLY THURSDAY EVENING...BUT SHOULD REMAIN
BELOW 10KT. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...4 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 300206
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
906 PM CDT WED OCT 29 2014

.DISCUSSION...
906 PM CDT

FOR EVENING UPDATE...

MINOR CHANGES TO GOING FORECAST TO LOWER MIN TEMPS A LITTLE OVER
NORTH CENTRAL IL...PARTICULARLY THE ROCK RIVER VALLEY...WHERE CLEAR
SKIES AND LIGHT WINDS IN VICINITY OF SFC RIDGE AXIS HAVE ALLOWED
STRONG RADIATIONAL COOLING AND A QUICK DROP IN TEMPS TO THE LOW-MID
30S. GIVEN PROXIMITY OF THE RIDGE AND CLEAR SKIES UNTIL EARLY
MORNING WHEN HIGH CLOUDS APPROACH FROM THE NORTHWEST...THINK A FEW
UPPER 20S LIKELY AT THE COOLER SPOTS IN THAT AREA.

OTHERWISE...MAINLY A FEW TWEAKS TO SKY COVER TO MATCH GOES 11-3.9
MICRON IMAGERY OF CLEARING ACROSS MUCH OF NORTHERN IL. NORTHWEST
INDIANA WILL BE A LITTLE SLOWER TO CLEAR BASED ON SATELLITE IMAGERY.
REMAINDER OF FORECAST LOOKS TO BE IN GOOD SHAPE WITH MOST ATTENTION
FOCUSED ON FRIDAYS IMPRESSIVE STORM SYSTEM.

RATZER

&&

.PREV DISCUSSION...
330 PM CDT

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO BE WITH REGARDS
TO THE SIGNIFICANT STORM SYSTEM EXPECTED TO DEVELOP ACROSS THE GREAT
LAKES AND OHIO VALLEY FRIDAY. THIS SYSTEM PROMISES TO PRODUCE
STRONG WINDS FRIDAY...POSSIBLY IN EXCESS OF 50 MPH ACROSS PORTIONS
OF THE REGION. THERE IS ALSO A DECENT CHANCE FOR SOME RAIN AND
SNOW...ESPECIALLY ACROSS EASTERN SECTIONS OF THE REGION FRIDAY INTO
FRIDAY NIGHT.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON...ACROSS NORTH AMERICA...
INDICATES THE PRESENCE OF POTENT STORM SYSTEM DIGGING ACROSS THE
GULF OF ALASKA...WITH THE CENTER OF CIRCULATION NEAR 53N 150W. THIS
SYSTEM WILL PLAY A MAJOR ROLE OVER THE NEXT 24 TO 36 HOURS IN
AMPLIFYING THE UPPER LEVEL FLOW PATTERN ACROSS NORTH AMERICA. MOST
NOTABLE WILL BE THE SHARPENING AND AMPLIFICATION OF AN UPPER LEVEL
RIDGE ACROSS THE INTER MOUNTAIN WEST AND HIGH PLAINS BY LATE
THURSDAY. THIS PARTICULAR PATTERN WILL FAVOR FALLING HEIGHTS AND THE
DEVELOPMENT OF STRONG NORTH-NORTHWEST ALOFT ACROSS THE GREAT LAKES
AND OHIO VALLEY REGIONS. MODEL GUIDANCE CONTINUES TO SUGGEST THAT
THIS EVOLVING LARGE SCALE WEATHER PATTERN WILL ACT TO STEER A
SHORTWAVE DISTURBANCE...CURRENTLY ACROSS NORTHERN SASKATCHEWAN AND
MANITOBA...SOUTHWARD RIGHT ACROSS THE AREA BY FRIDAY MORNING.

THE MAIN THREAT FOR ACTIVE WEATHER WILL BEGIN THURSDAY NIGHT AND
LAST INTO FRIDAY NIGHT. AS THE AFOREMENTIONED DISTURBANCE ACROSS
NORTHERN CANADA DIGS SOUTHWARD OVER WISCONSIN BY THURSDAY NIGHT...IT
WILL INDUCE AN AREA OF SURFACE LOW PRESSURE ACROSS LOWER MICHIGAN.
THIS SURFACE LOW IS OVERALL EXPECTED TO REMAIN FAIRLY WEAK (IN TERMS
OF CENTRAL PRESSURE) AS IT PROGRESSES SOUTHEASTWARD OVER THE OHIO
VALLEY LATER FRIDAY. AN ASSOCIATED COLD FRONT WILL BE DRIVEN ACROSS
THE AREA INTO EARLY FRIDAY MORNING...WITH STRONG COLD AIR ADVECTION
AND STRONG NORTHERLY WINDS EXPECTED IN ITS WAKE. IN SPITE OF THE
FACT THAT THE SURFACE LOW WILL REMAIN WEAK...THE SURFACE PRESSURE
GRADIENT IS EXPECTED TO BE QUITE STRONG ACROSS THE WESTERN LAKES
REGION AND INTO NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
FRIDAY...THANKS TO A STRONG 1033 MB HIGH THAT WILL BE RAPIDLY
BUILDING EASTWARD ACROSS THE UPPER MIDWEST. OVERALL...THIS LOOKS TO
SET UP TO STRONG PRESSURE RISES...POSSIBLY IN EXCESS OF 6 MB/6HR
PERIOD...ESPECIALLY ACROSS LAKE MICHIGAN AND ADJACENT AREAS OF
NORTHEASTERN ILLINOIS AND NORTHWESTERN INDIANA. THIS COMBINED WITH
THE STRONG PUSH OF MUCH COLDER AIR...SHOULD DRIVE SOME VERY STRONG
WINDS. MODEL SOUNDINGS INDICATE MEAN LAYER FLOW IN EXCESS OF 45 KT
OVER SOUTHERN LAKE MICHIGAN...WITH AROUND 50 KT OF FLOW AT THE TOP
OF THE MIXING LAYER. IT APPEARS THAT THE STRONGEST WINDS WITH THIS
SYSTEM WILL BE DURING THE LATE MORNING AND AFTERNOON ON FRIDAY
FOLLOWING THE PASSAGE OF THE UPPER LEVEL VORT MAX. THE TRACK OF THIS
SYSTEM ALSO SUGGESTS THAT THE STRONGEST WINDS WILL ALSO BE OVER
APPROXIMATELY THE EASTERN HALF OF MY CWA...ROUGHLY FROM THE CHICAGO
METRO AREA AND POINTS EASTWARD. THESE AREAS COULD REACH WIND
ADVISORY CRITERIA WITH WIND GUSTS UP TO 50 MPH.

THE STRONG NORTHERLY WINDS COMING IN OFF THE LAKE COULD ALLOW WIND
GUSTS TO APPROACH 50KT FOR AREAS NEAR THE LAKE SHORE...ESPECIALLY IN
NORTHWESTERN INDIANA. VERY HIGH CRASHING WAVES IN EXCESS OF 18 FT
ALSO APPEAR LIKELY FOR THE INDIANA AND PORTIONS OF THE ILLINOIS
SHORELINES...WHICH COULD RESULT IN SOME LAKE SHORE FLOODING CONCERNS
FRIDAY.

IT APPEARS MUCH OF THE PRECIPITATION WITH THIS SYSTEM WILL BE
FAVORED ACROSS AREAS NEAR THE LAKE ON FRIDAY AND FRIDAY EVENING.
HOWEVER...AS THE MAIN UPPER IMPULSE MOVES OVER THE AREA THURSDAY
NIGHT INTO EARLY FRIDAY...IT COULD DRIVE A SHORT PERIOD OF SHOWERS
ACROSS MUCH OF THE AREA. HOWEVER...DRIER AIR AND LARGE SCALE FORCING
FOR DECENT SHOULD OVERSPREAD MOST INLAND AREAS ACROSS NORTHERN
ILLINOIS BY FRIDAY AFTERNOON...LIKELY ENDING THE THREAT OF PRECIP.
HOWEVER...AREAS NEAR THE LAKE IN FAR NORTHEASTERN ILLINOIS AND MY
NORTHWESTERN INDIANA COUNTIES WILL LIKELY CONTINUE TO EXPERIENCE
PRECIPITATION FRIDAY AFTERNOON AND INTO THE EVENING AS THERMODYNAMICS
OVER LAKE MICHIGAN WILL BECOME VERY FAVORABLE FOR LAKE EFFECT
PRECIPITATION THROUGH FRIDAY EVENING. LAKE INDUCED EQUILIBRIUM LEVELS
LOOK TO EXCEED 16,000 FEET WITH LAKE SURFACE TEMPERATURE TO 850 MB
TEMPERATURE DIFFERENCES OF 18-19 DEGREES C. THE OVERALL DEPTH OF
THIS LAKE INDUCED INSTABILITY COULD ALSO ALLOW FOR SOME CHARGE
SEPARATION SUPPORTING THUNDER AND LIGHTENING ACROSS SOUTHERN
PORTIONS OF THE LAKE AND POSSIBLY INTO NORTHWESTERN INDIANA FRIDAY.
SO I HAVE INCLUDED A MENTION OF SUCH IN THE FORECAST.

THE MAIN QUESTION WITH THIS EVENT REMAINS AS TO WHEN THE PRECIP TYPE
COULD MIX WITH OR CHANGE TO SNOW. IT APPEARS THAT WITH 850 MB
TEMPERATURES AROUND -8 DEGREES C...THAT A TRANSITION OVER TO LAKE
EFFECT SNOW SHOWERS APPEARS TO BE A DECENT BET BY LATE FRIDAY
AFTERNOON AND INTO THE EVENING. HOWEVER...DUE TO THE POTENTIAL FOR
CONVECTIVELY DRIVEN HEAVY SHOWERS OVER THE LAKE...DYNAMIC COOLING
COULD BECOME STRONG ENOUGH TO RESULT IN AN EARLY TRANSITION TO SNOW
OVER NORTHWESTERN INDIANA. WITH THIS IN MIND CONFIDENCE ON TIMING OF
ANY TRANSITION TO SNOW ON FRIDAY IS LOW...THOUGH THERE IS THE
POTENTIAL FOR SOME HEAVIER RAIN/SNOW SHOWERS WHICH COULD RESULT IN
SOME ACCUMULATIONS ACROSS PORTIONS OF NORTHWESTERN INDIAN IN SPITE
OF WARM GROUND TEMPS. THE STRONG WINDS COULD ALSO ALLOW THESE
SHOWERS TO GET WELL INLAND ACROSS NORTHWESTERN INDIANA. THE THREAT
OF SNOW SHOULD COME TO END OVERNIGHT FRIDAY AS INVERSION HEIGHTS
TANK IN RESPONSE TO BUILDING UPPER LEVEL HEIGHTS AND WARMING MID
LEVEL TEMPERATURES.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY...THEN MODERATING TEMPERATURES ARE EXPECTED
INTO EARLY NEXT WEEK AS THE WESTERN CONUS UPPER RIDGE BUILDS
EASTWARD OVER THE REGION. ANOTHER COLD FRONT LOOKS TO TAKE AIM ON
THE AREA AROUND NEXT TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE
OF SHOWERS. OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING
THE LATER HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NONE. CMS

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

BKN/OVC 4-5KFT CIGS WILL CONTINUE MOVING SOUTHEAST AND SCATTER OUT
THIS EVENING BUT WILL LIKELY TAKE A FEW MORE HOURS. ONCE THESE
CLOUDS SHIFT EAST...INCREASING HIGH CLOUDS OVERNIGHT TOWARD
MORNING WILL LOWER TO A MID DECK IN THE AFTERNOON AND THEN TO A
4-6KFT THURSDAY EVENING. A WEAK UPPER WAVE WILL MOVE ACROSS THE
REGION THURSDAY BRINGING A CHANCE OF SHOWERS THAT APPEAR TO STAY
JUST SOUTH OF THE TERMINALS...BUT SOME SPRINKLES OR AN ISOLATED
SHOWER IS POSSIBLE...ESPECIALLY BY THURSDAY EVENING.

WEST/NORTHWEST WINDS UNDER 10KTS WILL DIMINISH TO 5KT OR LESS THIS
EVENING AND TURN MORE SOUTHWEST OVERNIGHT...POSSIBLY BECOMING
LIGHT AND VARIABLE OR CALM IN SOME LOCATIONS. WINDS MAY TURN A BIT
MORE SOUTHERLY AFTER SUNRISE THEN SLOWLY TURN BACK WESTERLY BY
AFTERNOON AND NORTHWESTERLY THURSDAY EVENING...BUT SHOULD REMAIN
BELOW 10KT. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...4 AM FRIDAY TO 4 AM SATURDAY.

&&

$$

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 292342
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
642 PM CDT WED OCT 29 2014

.DISCUSSION...
330 PM CDT

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO BE WITH REGARDS
TO THE SIGNIFICANT STORM SYSTEM EXPECTED TO DEVELOP ACROSS THE GREAT
LAKES AND OHIO VALLEY FRIDAY. THIS SYSTEM PROMISES TO PRODUCE
STRONG WINDS FRIDAY...POSSIBLY IN EXCESS OF 50 MPH ACROSS PORTIONS
OF THE REGION. THERE IS ALSO A DECENT CHANCE FOR SOME RAIN AND
SNOW...ESPECIALLY ACROSS EASTERN SECTIONS OF THE REGION FRIDAY INTO
FRIDAY NIGHT.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON...ACROSS NORTH AMERICA...
INDICATES THE PRESENCE OF POTENT STORM SYSTEM DIGGING ACROSS THE
GULF OF ALASKA...WITH THE CENTER OF CIRCULATION NEAR 53N 150W. THIS
SYSTEM WILL PLAY A MAJOR ROLE OVER THE NEXT 24 TO 36 HOURS IN
AMPLIFYING THE UPPER LEVEL FLOW PATTERN ACROSS NORTH AMERICA. MOST
NOTABLE WILL BE THE SHARPENING AND AMPLIFICATION OF AN UPPER LEVEL
RIDGE ACROSS THE INTER MOUNTAIN WEST AND HIGH PLAINS BY LATE
THURSDAY. THIS PARTICULAR PATTERN WILL FAVOR FALLING HEIGHTS AND THE
DEVELOPMENT OF STRONG NORTH-NORTHWEST ALOFT ACROSS THE GREAT LAKES
AND OHIO VALLEY REGIONS. MODEL GUIDANCE CONTINUES TO SUGGEST THAT
THIS EVOLVING LARGE SCALE WEATHER PATTERN WILL ACT TO STEER A
SHORTWAVE DISTURBANCE...CURRENTLY ACROSS NORTHERN SASKATCHEWAN AND
MANITOBA...SOUTHWARD RIGHT ACROSS THE AREA BY FRIDAY MORNING.

THE MAIN THREAT FOR ACTIVE WEATHER WILL BEGIN THURSDAY NIGHT AND
LAST INTO FRIDAY NIGHT. AS THE AFOREMENTIONED DISTURBANCE ACROSS
NORTHERN CANADA DIGS SOUTHWARD OVER WISCONSIN BY THURSDAY NIGHT...IT
WILL INDUCE AN AREA OF SURFACE LOW PRESSURE ACROSS LOWER MICHIGAN.
THIS SURFACE LOW IS OVERALL EXPECTED TO REMAIN FAIRLY WEAK (IN TERMS
OF CENTRAL PRESSURE) AS IT PROGRESSES SOUTHEASTWARD OVER THE OHIO
VALLEY LATER FRIDAY. AN ASSOCIATED COLD FRONT WILL BE DRIVEN ACROSS
THE AREA INTO EARLY FRIDAY MORNING...WITH STRONG COLD AIR ADVECTION
AND STRONG NORTHERLY WINDS EXPECTED IN ITS WAKE. IN SPITE OF THE
FACT THAT THE SURFACE LOW WILL REMAIN WEAK...THE SURFACE PRESSURE
GRADIENT IS EXPECTED TO BE QUITE STRONG ACROSS THE WESTERN LAKES
REGION AND INTO NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
FRIDAY...THANKS TO A STRONG 1033 MB HIGH THAT WILL BE RAPIDLY
BUILDING EASTWARD ACROSS THE UPPER MIDWEST. OVERALL...THIS LOOKS TO
SET UP TO STRONG PRESSURE RISES...POSSIBLY IN EXCESS OF 6 MB/6HR
PERIOD...ESPECIALLY ACROSS LAKE MICHIGAN AND ADJACENT AREAS OF
NORTHEASTERN ILLINOIS AND NORTHWESTERN INDIANA. THIS COMBINED WITH
THE STRONG PUSH OF MUCH COLDER AIR...SHOULD DRIVE SOME VERY STRONG
WINDS. MODEL SOUNDINGS INDICATE MEAN LAYER FLOW IN EXCESS OF 45 KT
OVER SOUTHERN LAKE MICHIGAN...WITH AROUND 50 KT OF FLOW AT THE TOP
OF THE MIXING LAYER. IT APPEARS THAT THE STRONGEST WINDS WITH THIS
SYSTEM WILL BE DURING THE LATE MORNING AND AFTERNOON ON FRIDAY
FOLLOWING THE PASSAGE OF THE UPPER LEVEL VORT MAX. THE TRACK OF THIS
SYSTEM ALSO SUGGESTS THAT THE STRONGEST WINDS WILL ALSO BE OVER
APPROXIMATELY THE EASTERN HALF OF MY CWA...ROUGHLY FROM THE CHICAGO
METRO AREA AND POINTS EASTWARD. THESE AREAS COULD REACH WIND
ADVISORY CRITERIA WITH WIND GUSTS UP TO 50 MPH.

THE STRONG NORTHERLY WINDS COMING IN OFF THE LAKE COULD ALLOW WIND
GUSTS TO APPROACH 50KT FOR AREAS NEAR THE LAKE SHORE...ESPECIALLY IN
NORTHWESTERN INDIANA. VERY HIGH CRASHING WAVES IN EXCESS OF 18 FT
ALSO APPEAR LIKELY FOR THE INDIANA AND PORTIONS OF THE ILLINOIS
SHORELINES...WHICH COULD RESULT IN SOME LAKE SHORE FLOODING CONCERNS
FRIDAY.

IT APPEARS MUCH OF THE PRECIPITATION WITH THIS SYSTEM WILL BE
FAVORED ACROSS AREAS NEAR THE LAKE ON FRIDAY AND FRIDAY EVENING.
HOWEVER...AS THE MAIN UPPER IMPULSE MOVES OVER THE AREA THURSDAY
NIGHT INTO EARLY FRIDAY...IT COULD DRIVE A SHORT PERIOD OF SHOWERS
ACROSS MUCH OF THE AREA. HOWEVER...DRIER AIR AND LARGE SCALE FORCING
FOR DECENT SHOULD OVERSPREAD MOST INLAND AREAS ACROSS NORTHERN
ILLINOIS BY FRIDAY AFTERNOON...LIKELY ENDING THE THREAT OF PRECIP.
HOWEVER...AREAS NEAR THE LAKE IN FAR NORTHEASTERN ILLINOIS AND MY
NORTHWESTERN INDIANA COUNTIES WILL LIKELY CONTINUE TO EXPERIENCE
PRECIPITATION FRIDAY AFTERNOON AND INTO THE EVENING AS THERMODYNAMICS
OVER LAKE MICHIGAN WILL BECOME VERY FAVORABLE FOR LAKE EFFECT
PRECIPITATION THROUGH FRIDAY EVENING. LAKE INDUCED EQUILIBRIUM LEVELS
LOOK TO EXCEED 16,000 FEET WITH LAKE SURFACE TEMPERATURE TO 850 MB
TEMPERATURE DIFFERENCES OF 18-19 DEGREES C. THE OVERALL DEPTH OF
THIS LAKE INDUCED INSTABILITY COULD ALSO ALLOW FOR SOME CHARGE
SEPARATION SUPPORTING THUNDER AND LIGHTENING ACROSS SOUTHERN
PORTIONS OF THE LAKE AND POSSIBLY INTO NORTHWESTERN INDIANA FRIDAY.
SO I HAVE INCLUDED A MENTION OF SUCH IN THE FORECAST.

THE MAIN QUESTION WITH THIS EVENT REMAINS AS TO WHEN THE PRECIP TYPE
COULD MIX WITH OR CHANGE TO SNOW. IT APPEARS THAT WITH 850 MB
TEMPERATURES AROUND -8 DEGREES C...THAT A TRANSITION OVER TO LAKE
EFFECT SNOW SHOWERS APPEARS TO BE A DECENT BET BY LATE FRIDAY
AFTERNOON AND INTO THE EVENING. HOWEVER...DUE TO THE POTENTIAL FOR
CONVECTIVELY DRIVEN HEAVY SHOWERS OVER THE LAKE...DYNAMIC COOLING
COULD BECOME STRONG ENOUGH TO RESULT IN AN EARLY TRANSITION TO SNOW
OVER NORTHWESTERN INDIANA. WITH THIS IN MIND CONFIDENCE ON TIMING OF
ANY TRANSITION TO SNOW ON FRIDAY IS LOW...THOUGH THERE IS THE
POTENTIAL FOR SOME HEAVIER RAIN/SNOW SHOWERS WHICH COULD RESULT IN
SOME ACCUMULATIONS ACROSS PORTIONS OF NORTHWESTERN INDIAN IN SPITE
OF WARM GROUND TEMPS. THE STRONG WINDS COULD ALSO ALLOW THESE
SHOWERS TO GET WELL INLAND ACROSS NORTHWESTERN INDIANA. THE THREAT
OF SNOW SHOULD COME TO END OVERNIGHT FRIDAY AS INVERSION HEIGHTS
TANK IN RESPONSE TO BUILDING UPPER LEVEL HEIGHTS AND WARMING MID
LEVEL TEMPERATURES.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY...THEN MODERATING TEMPERATURES ARE EXPECTED
INTO EARLY NEXT WEEK AS THE WESTERN CONUS UPPER RIDGE BUILDS
EASTWARD OVER THE REGION. ANOTHER COLD FRONT LOOKS TO TAKE AIM ON
THE AREA AROUND NEXT TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE
OF SHOWERS. OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING
THE LATER HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NONE. CMS

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

BKN/OVC 4-5KFT CIGS WILL CONTINUE MOVING SOUTHEAST AND SCATTER OUT
THIS EVENING BUT WILL LIKELY TAKE A FEW MORE HOURS. ONCE THESE
CLOUDS SHIFT EAST...INCREASING HIGH CLOUDS OVERNIGHT TOWARD
MORNING WILL LOWER TO A MID DECK IN THE AFTERNOON AND THEN TO A
4-6KFT THURSDAY EVENING. A WEAK UPPER WAVE WILL MOVE ACROSS THE
REGION THURSDAY BRINGING A CHANCE OF SHOWERS THAT APPEAR TO STAY
JUST SOUTH OF THE TERMINALS...BUT SOME SPRINKLES OR AN ISOLATED
SHOWER IS POSSIBLE...ESPECIALLY BY THURSDAY EVENING.

WEST/NORTHWEST WINDS UNDER 10KTS WILL DIMINISH TO 5KT OR LESS THIS
EVENING AND TURN MORE SOUTHWEST OVERNIGHT...POSSIBLY BECOMING
LIGHT AND VARIABLE OR CALM IN SOME LOCATIONS. WINDS MAY TURN A BIT
MORE SOUTHERLY AFTER SUNRISE THEN SLOWLY TURN BACK WESTERLY BY
AFTERNOON AND NORTHWESTERLY THURSDAY EVENING...BUT SHOULD REMAIN
BELOW 10KT. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* FRIDAY...STRONG NORTH WINDS GUSTING TO 35 KT. CHANCE OF SHRA OR
  SHSN.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...DRY/VFR. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTHERLY WINDS.
* TUESDAY...CHANCE OF SHRA. WESTERLY WINDS.

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

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

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...4 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 292204
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
504 PM CDT WED OCT 29 2014

.DISCUSSION...
330 PM CDT

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO BE WITH REGARDS
TO THE SIGNIFICANT STORM SYSTEM EXPECTED TO DEVELOP ACROSS THE GREAT
LAKES AND OHIO VALLEY FRIDAY. THIS SYSTEM PROMISES TO PRODUCE
STRONG WINDS FRIDAY...POSSIBLY IN EXCESS OF 50 MPH ACROSS PORTIONS
OF THE REGION. THERE IS ALSO A DECENT CHANCE FOR SOME RAIN AND
SNOW...ESPECIALLY ACROSS EASTERN SECTIONS OF THE REGION FRIDAY INTO
FRIDAY NIGHT.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON...ACROSS NORTH AMERICA...
INDICATES THE PRESENCE OF POTENT STORM SYSTEM DIGGING ACROSS THE
GULF OF ALASKA...WITH THE CENTER OF CIRCULATION NEAR 53N 150W. THIS
SYSTEM WILL PLAY A MAJOR ROLE OVER THE NEXT 24 TO 36 HOURS IN
AMPLIFYING THE UPPER LEVEL FLOW PATTERN ACROSS NORTH AMERICA. MOST
NOTABLE WILL BE THE SHARPENING AND AMPLIFICATION OF AN UPPER LEVEL
RIDGE ACROSS THE INTER MOUNTAIN WEST AND HIGH PLAINS BY LATE
THURSDAY. THIS PARTICULAR PATTERN WILL FAVOR FALLING HEIGHTS AND THE
DEVELOPMENT OF STRONG NORTH-NORTHWEST ALOFT ACROSS THE GREAT LAKES
AND OHIO VALLEY REGIONS. MODEL GUIDANCE CONTINUES TO SUGGEST THAT
THIS EVOLVING LARGE SCALE WEATHER PATTERN WILL ACT TO STEER A
SHORTWAVE DISTURBANCE...CURRENTLY ACROSS NORTHERN SASKATCHEWAN AND
MANITOBA...SOUTHWARD RIGHT ACROSS THE AREA BY FRIDAY MORNING.

THE MAIN THREAT FOR ACTIVE WEATHER WILL BEGIN THURSDAY NIGHT AND
LAST INTO FRIDAY NIGHT. AS THE AFOREMENTIONED DISTURBANCE ACROSS
NORTHERN CANADA DIGS SOUTHWARD OVER WISCONSIN BY THURSDAY NIGHT...IT
WILL INDUCE AN AREA OF SURFACE LOW PRESSURE ACROSS LOWER MICHIGAN.
THIS SURFACE LOW IS OVERALL EXPECTED TO REMAIN FAIRLY WEAK (IN TERMS
OF CENTRAL PRESSURE) AS IT PROGRESSES SOUTHEASTWARD OVER THE OHIO
VALLEY LATER FRIDAY. AN ASSOCIATED COLD FRONT WILL BE DRIVEN ACROSS
THE AREA INTO EARLY FRIDAY MORNING...WITH STRONG COLD AIR ADVECTION
AND STRONG NORTHERLY WINDS EXPECTED IN ITS WAKE. IN SPITE OF THE
FACT THAT THE SURFACE LOW WILL REMAIN WEAK...THE SURFACE PRESSURE
GRADIENT IS EXPECTED TO BE QUITE STRONG ACROSS THE WESTERN LAKES
REGION AND INTO NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
FRIDAY...THANKS TO A STRONG 1033 MB HIGH THAT WILL BE RAPIDLY
BUILDING EASTWARD ACROSS THE UPPER MIDWEST. OVERALL...THIS LOOKS TO
SET UP TO STRONG PRESSURE RISES...POSSIBLY IN EXCESS OF 6 MB/6HR
PERIOD...ESPECIALLY ACROSS LAKE MICHIGAN AND ADJACENT AREAS OF
NORTHEASTERN ILLINOIS AND NORTHWESTERN INDIANA. THIS COMBINED WITH
THE STRONG PUSH OF MUCH COLDER AIR...SHOULD DRIVE SOME VERY STRONG
WINDS. MODEL SOUNDINGS INDICATE MEAN LAYER FLOW IN EXCESS OF 45 KT
OVER SOUTHERN LAKE MICHIGAN...WITH AROUND 50 KT OF FLOW AT THE TOP
OF THE MIXING LAYER. IT APPEARS THAT THE STRONGEST WINDS WITH THIS
SYSTEM WILL BE DURING THE LATE MORNING AND AFTERNOON ON FRIDAY
FOLLOWING THE PASSAGE OF THE UPPER LEVEL VORT MAX. THE TRACK OF THIS
SYSTEM ALSO SUGGESTS THAT THE STRONGEST WINDS WILL ALSO BE OVER
APPROXIMATELY THE EASTERN HALF OF MY CWA...ROUGHLY FROM THE CHICAGO
METRO AREA AND POINTS EASTWARD. THESE AREAS COULD REACH WIND
ADVISORY CRITERIA WITH WIND GUSTS UP TO 50 MPH.

THE STRONG NORTHERLY WINDS COMING IN OFF THE LAKE COULD ALLOW WIND
GUSTS TO APPROACH 50KT FOR AREAS NEAR THE LAKE SHORE...ESPECIALLY IN
NORTHWESTERN INDIANA. VERY HIGH CRASHING WAVES IN EXCESS OF 18 FT
ALSO APPEAR LIKELY FOR THE INDIANA AND PORTIONS OF THE ILLINOIS
SHORELINES...WHICH COULD RESULT IN SOME LAKE SHORE FLOODING CONCERNS
FRIDAY.

IT APPEARS MUCH OF THE PRECIPITATION WITH THIS SYSTEM WILL BE
FAVORED ACROSS AREAS NEAR THE LAKE ON FRIDAY AND FRIDAY EVENING.
HOWEVER...AS THE MAIN UPPER IMPULSE MOVES OVER THE AREA THURSDAY
NIGHT INTO EARLY FRIDAY...IT COULD DRIVE A SHORT PERIOD OF SHOWERS
ACROSS MUCH OF THE AREA. HOWEVER...DRIER AIR AND LARGE SCALE FORCING
FOR DECENT SHOULD OVERSPREAD MOST INLAND AREAS ACROSS NORTHERN
ILLINOIS BY FRIDAY AFTERNOON...LIKELY ENDING THE THREAT OF PRECIP.
HOWEVER...AREAS NEAR THE LAKE IN FAR NORTHEASTERN ILLINOIS AND MY
NORTHWESTERN INDIANA COUNTIES WILL LIKELY CONTINUE TO EXPERIENCE
PRECIPITATION FRIDAY AFTERNOON AND INTO THE EVENING AS THERMODYNAMICS
OVER LAKE MICHIGAN WILL BECOME VERY FAVORABLE FOR LAKE EFFECT
PRECIPITATION THROUGH FRIDAY EVENING. LAKE INDUCED EQUILIBRIUM LEVELS
LOOK TO EXCEED 16,000 FEET WITH LAKE SURFACE TEMPERATURE TO 850 MB
TEMPERATURE DIFFERENCES OF 18-19 DEGREES C. THE OVERALL DEPTH OF
THIS LAKE INDUCED INSTABILITY COULD ALSO ALLOW FOR SOME CHARGE
SEPARATION SUPPORTING THUNDER AND LIGHTENING ACROSS SOUTHERN
PORTIONS OF THE LAKE AND POSSIBLY INTO NORTHWESTERN INDIANA FRIDAY.
SO I HAVE INCLUDED A MENTION OF SUCH IN THE FORECAST.

THE MAIN QUESTION WITH THIS EVENT REMAINS AS TO WHEN THE PRECIP TYPE
COULD MIX WITH OR CHANGE TO SNOW. IT APPEARS THAT WITH 850 MB
TEMPERATURES AROUND -8 DEGREES C...THAT A TRANSITION OVER TO LAKE
EFFECT SNOW SHOWERS APPEARS TO BE A DECENT BET BY LATE FRIDAY
AFTERNOON AND INTO THE EVENING. HOWEVER...DUE TO THE POTENTIAL FOR
CONVECTIVELY DRIVEN HEAVY SHOWERS OVER THE LAKE...DYNAMIC COOLING
COULD BECOME STRONG ENOUGH TO RESULT IN AN EARLY TRANSITION TO SNOW
OVER NORTHWESTERN INDIANA. WITH THIS IN MIND CONFIDENCE ON TIMING OF
ANY TRANSITION TO SNOW ON FRIDAY IS LOW...THOUGH THERE IS THE
POTENTIAL FOR SOME HEAVIER RAIN/SNOW SHOWERS WHICH COULD RESULT IN
SOME ACCUMULATIONS ACROSS PORTIONS OF NORTHWESTERN INDIAN IN SPITE
OF WARM GROUND TEMPS. THE STRONG WINDS COULD ALSO ALLOW THESE
SHOWERS TO GET WELL INLAND ACROSS NORTHWESTERN INDIANA. THE THREAT
OF SNOW SHOULD COME TO END OVERNIGHT FRIDAY AS INVERSION HEIGHTS
TANK IN RESPONSE TO BUILDING UPPER LEVEL HEIGHTS AND WARMING MID
LEVEL TEMPERATURES.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY...THEN MODERATING TEMPERATURES ARE EXPECTED
INTO EARLY NEXT WEEK AS THE WESTERN CONUS UPPER RIDGE BUILDS
EASTWARD OVER THE REGION. ANOTHER COLD FRONT LOOKS TO TAKE AIM ON
THE AREA AROUND NEXT TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE
OF SHOWERS. OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING
THE LATER HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NONE.

RATZER

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

OVERALL QUIET CONDITIONS FORECAST ACROSS THE TERMINALS THIS
FORECAST PERIOD...AS HIGH PRESSURE TO THE WEST MOVES OVERHEAD. VFR
CEILINGS STILL HOLDING IN PLACE EARLY THIS AFTERNOON BUT DO EXPECT
A SCATTERING TREND TO OCCUR LATE THIS AFTERNOON INTO THE EARLY
EVENING. AS THIS HIGH SHIFTS TOWARDS THE TERMINALS THIS
EVENING...WINDS WILL CONTINUE TO DIMINISH AND LIKELY BECOME CALM
FOR A PERIOD TONIGHT. WITH EXITING HIGH PRESSURE TO THE EAST ON
THURSDAY AND ANOTHER SYSTEM APPROACHING FROM THE
NORTHWEST...SOUTHWEST WINDS WILL PICK UP BY LATE MORNING. EXPECT
THE BULK OF ANY PRECIP ASSOCIATED WITH THIS SYSTEM TO REMAIN JUST
TO THE SOUTH OF THE TERMINALS...BUT WITH VFR CEILINGS RETURNING
LATER IN THE AFTERNOON.

RODRIGUEZ

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

RATZER

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

* THURSDAY NIGHT...SLIGHT CHANCE OF SHRA LATE. STRONG NWLY WINDS
  DEVELOPING LATE.

* FRIDAY...SLIGHT CHANCE OF SHRA EARLY SLIGHT CHANCE SHRA/SHSN MIX
  LATE. STRONG/GUSTY NORTH WINDS.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS.

* SUNDAY....VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

* TUESDAY...CHANCE OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

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

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...4 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 292031
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
331 PM CDT WED OCT 29 2014

.DISCUSSION...
330 PM CDT

THE MAIN FORECAST FOCUS THIS AFTERNOON CONTINUES TO BE WITH REGARDS
TO THE SIGNIFICANT STORM SYSTEM EXPECTED TO DEVELOP ACROSS THE GREAT
LAKES AND OHIO VALLEY FRIDAY. THIS SYSTEM PROMISES TO PRODUCE
STRONG WINDS FRIDAY...POSSIBLY IN EXCESS OF 50 MPH ACROSS PORTIONS
OF THE REGION. THERE IS ALSO A DECENT CHANCE FOR SOME RAIN AND
SNOW...ESPECIALLY ACROSS EASTERN SECTIONS OF THE REGION FRIDAY INTO
FRIDAY NIGHT.

WATER VAPOR IMAGERY EARLY THIS AFTERNOON...ACROSS NORTH AMERICA...
INDICATES THE PRESENCE OF POTENT STORM SYSTEM DIGGING ACROSS THE
GULF OF ALASKA...WITH THE CENTER OF CIRCULATION NEAR 53N 150W. THIS
SYSTEM WILL PLAY A MAJOR ROLE OVER THE NEXT 24 TO 36 HOURS IN
AMPLIFYING THE UPPER LEVEL FLOW PATTERN ACROSS NORTH AMERICA. MOST
NOTABLE WILL BE THE SHARPENING AND AMPLIFICATION OF AN UPPER LEVEL
RIDGE ACROSS THE INTER MOUNTAIN WEST AND HIGH PLAINS BY LATE
THURSDAY. THIS PARTICULAR PATTERN WILL FAVOR FALLING HEIGHTS AND THE
DEVELOPMENT OF STRONG NORTH-NORTHWEST ALOFT ACROSS THE GREAT LAKES
AND OHIO VALLEY REGIONS. MODEL GUIDANCE CONTINUES TO SUGGEST THAT
THIS EVOLVING LARGE SCALE WEATHER PATTERN WILL ACT TO STEER A
SHORTWAVE DISTURBANCE...CURRENTLY ACROSS NORTHERN SASKATCHEWAN AND
MANITOBA...SOUTHWARD RIGHT ACROSS THE AREA BY FRIDAY MORNING.

THE MAIN THREAT FOR ACTIVE WEATHER WILL BEGIN THURSDAY NIGHT AND
LAST INTO FRIDAY NIGHT. AS THE AFOREMENTIONED DISTURBANCE ACROSS
NORTHERN CANADA DIGS SOUTHWARD OVER WISCONSIN BY THURSDAY NIGHT...IT
WILL INDUCE AN AREA OF SURFACE LOW PRESSURE ACROSS LOWER MICHIGAN.
THIS SURFACE LOW IS OVERALL EXPECTED TO REMAIN FAIRLY WEAK (IN TERMS
OF CENTRAL PRESSURE) AS IT PROGRESSES SOUTHEASTWARD OVER THE OHIO
VALLEY LATER FRIDAY. AN ASSOCIATED COLD FRONT WILL BE DRIVEN ACROSS
THE AREA INTO EARLY FRIDAY MORNING...WITH STRONG COLD AIR ADVECTION
AND STRONG NORTHERLY WINDS EXPECTED IN ITS WAKE. IN SPITE OF THE
FACT THAT THE SURFACE LOW WILL REMAIN WEAK...THE SURFACE PRESSURE
GRADIENT IS EXPECTED TO BE QUITE STRONG ACROSS THE WESTERN LAKES
REGION AND INTO NORTHERN ILLINOIS/NORTHWESTERN INDIANA ON
FRIDAY...THANKS TO A STRONG 1033 MB HIGH THAT WILL BE RAPIDLY
BUILDING EASTWARD ACROSS THE UPPER MIDWEST. OVERALL...THIS LOOKS TO
SET UP TO STRONG PRESSURE RISES...POSSIBLY IN EXCESS OF 6 MB/6HR
PERIOD...ESPECIALLY ACROSS LAKE MICHIGAN AND ADJACENT AREAS OF
NORTHEASTERN ILLINOIS AND NORTHWESTERN INDIANA. THIS COMBINED WITH
THE STRONG PUSH OF MUCH COLDER AIR...SHOULD DRIVE SOME VERY STRONG
WINDS. MODEL SOUNDINGS INDICATE MEAN LAYER FLOW IN EXCESS OF 45 KT
OVER SOUTHERN LAKE MICHIGAN...WITH AROUND 50 KT OF FLOW AT THE TOP
OF THE MIXING LAYER. IT APPEARS THAT THE STRONGEST WINDS WITH THIS
SYSTEM WILL BE DURING THE LATE MORNING AND AFTERNOON ON FRIDAY
FOLLOWING THE PASSAGE OF THE UPPER LEVEL VORT MAX. THE TRACK OF THIS
SYSTEM ALSO SUGGESTS THAT THE STRONGEST WINDS WILL ALSO BE OVER
APPROXIMATELY THE EASTERN HALF OF MY CWA...ROUGHLY FROM THE CHICAGO
METRO AREA AND POINTS EASTWARD. THESE AREAS COULD REACH WIND
ADVISORY CRITERIA WITH WIND GUSTS UP TO 50 MPH.

THE STRONG NORTHERLY WINDS COMING IN OFF THE LAKE COULD ALLOW WIND
GUSTS TO APPROACH 50KT FOR AREAS NEAR THE LAKE SHORE...ESPECIALLY IN
NORTHWESTERN INDIANA. VERY HIGH CRASHING WAVES IN EXCESS OF 18 FT
ALSO APPEAR LIKELY FOR THE INDIANA AND PORTIONS OF THE ILLINOIS
SHORELINES...WHICH COULD RESULT IN SOME LAKE SHORE FLOODING CONCERNS
FRIDAY.

IT APPEARS MUCH OF THE PRECIPITATION WITH THIS SYSTEM WILL BE
FAVORED ACROSS AREAS NEAR THE LAKE ON FRIDAY AND FRIDAY EVENING.
HOWEVER...AS THE MAIN UPPER IMPULSE MOVES OVER THE AREA THURSDAY
NIGHT INTO EARLY FRIDAY...IT COULD DRIVE A SHORT PERIOD OF SHOWERS
ACROSS MUCH OF THE AREA. HOWEVER...DRIER AIR AND LARGE SCALE FORCING
FOR DECENT SHOULD OVERSPREAD MOST INLAND AREAS ACROSS NORTHERN
ILLINOIS BY FRIDAY AFTERNOON...LIKELY ENDING THE THREAT OF PRECIP.
HOWEVER...AREAS NEAR THE LAKE IN FAR NORTHEASTERN ILLINOIS AND MY
NORTHWESTERN INDIANA COUNTIES WILL LIKELY CONTINUE TO EXPERIENCE
PRECIPITATION FRIDAY AFTERNOON AND INTO THE EVENING AS THERMODYNAMICS
OVER LAKE MICHIGAN WILL BECOME VERY FAVORABLE FOR LAKE EFFECT
PRECIPITATION THROUGH FRIDAY EVENING. LAKE INDUCED EQUILIBRIUM LEVELS
LOOK TO EXCEED 16,000 FEET WITH LAKE SURFACE TEMPERATURE TO 850 MB
TEMPERATURE DIFFERENCES OF 18-19 DEGREES C. THE OVERALL DEPTH OF
THIS LAKE INDUCED INSTABILITY COULD ALSO ALLOW FOR SOME CHARGE
SEPARATION SUPPORTING THUNDER AND LIGHTENING ACROSS SOUTHERN
PORTIONS OF THE LAKE AND POSSIBLY INTO NORTHWESTERN INDIANA FRIDAY.
SO I HAVE INCLUDED A MENTION OF SUCH IN THE FORECAST.

THE MAIN QUESTION WITH THIS EVENT REMAINS AS TO WHEN THE PRECIP TYPE
COULD MIX WITH OR CHANGE TO SNOW. IT APPEARS THAT WITH 850 MB
TEMPERATURES AROUND -8 DEGREES C...THAT A TRANSITION OVER TO LAKE
EFFECT SNOW SHOWERS APPEARS TO BE A DECENT BET BY LATE FRIDAY
AFTERNOON AND INTO THE EVENING. HOWEVER...DUE TO THE POTENTIAL FOR
CONVECTIVELY DRIVEN HEAVY SHOWERS OVER THE LAKE...DYNAMIC COOLING
COULD BECOME STRONG ENOUGH TO RESULT IN AN EARLY TRANSITION TO SNOW
OVER NORTHWESTERN INDIANA. WITH THIS IN MIND CONFIDENCE ON TIMING OF
ANY TRANSITION TO SNOW ON FRIDAY IS LOW...THOUGH THERE IS THE
POTENTIAL FOR SOME HEAVIER RAIN/SNOW SHOWERS WHICH COULD RESULT IN
SOME ACCUMULATIONS ACROSS PORTIONS OF NORTHWESTERN INDIAN IN SPITE
OF WARM GROUND TEMPS. THE STRONG WINDS COULD ALSO ALLOW THESE
SHOWERS TO GET WELL INLAND ACROSS NORTHWESTERN INDIANA. THE THREAT
OF SNOW SHOULD COME TO END OVERNIGHT FRIDAY AS INVERSION HEIGHTS
TANK IN RESPONSE TO BUILDING UPPER LEVEL HEIGHTS AND WARMING MID
LEVEL TEMPERATURES.

HIGH TEMPERATURES AREA-WIDE LOOK TO REMAIN IN THE LOWER 40S AT BEST
ON FRIDAY AND SATURDAY...THEN MODERATING TEMPERATURES ARE EXPECTED
INTO EARLY NEXT WEEK AS THE WESTERN CONUS UPPER RIDGE BUILDS
EASTWARD OVER THE REGION. ANOTHER COLD FRONT LOOKS TO TAKE AIM ON
THE AREA AROUND NEXT TUESDAY...WHICH WILL RESULT IN OUR NEXT CHANCE
OF SHOWERS. OTHERWISE TEMPERATURES LOOK TO REMAIN NEAR NORMAL DURING
THE LATER HALF OF THE WEEK.

KJB

&&

.AVIATION...

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

* NONE.

RODRIGUEZ

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

OVERALL QUIET CONDITIONS FORECAST ACROSS THE TERMINALS THIS
FORECAST PERIOD...AS HIGH PRESSURE TO THE WEST MOVES OVERHEAD. VFR
CEILINGS STILL HOLDING IN PLACE EARLY THIS AFTERNOON BUT DO EXPECT
A SCATTERING TREND TO OCCUR LATE THIS AFTERNOON INTO THE EARLY
EVENING. AS THIS HIGH SHIFTS TOWARDS THE TERMINALS THIS
EVENING...WINDS WILL CONTINUE TO DIMINISH AND LIKELY BECOME CALM
FOR A PERIOD TONIGHT. WITH EXITING HIGH PRESSURE TO THE EAST ON
THURSDAY AND ANOTHER SYSTEM APPROACHING FROM THE
NORTHWEST...SOUTHWEST WINDS WILL PICK UP BY LATE MORNING. EXPECT
THE BULK OF ANY PRECIP ASSOCIATED WITH THIS SYSTEM TO REMAIN JUST
TO THE SOUTH OF THE TERMINALS...BUT WITH VFR CEILINGS RETURNING
LATER IN THE AFTERNOON.

RODRIGUEZ

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

RODRIGUEZ

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

* THURSDAY NIGHT...SLIGHT CHANCE OF SHRA LATE. STRONG NWLY WINDS
  DEVELOPING LATE.

* FRIDAY...SLIGHT CHANCE OF SHRA EARLY SLIGHT CHANCE SHRA/SHSN MIX
  LATE. STRONG/GUSTY NORTH WINDS.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS.

* SUNDAY....VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

* TUESDAY...CHANCE OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

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

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...4 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...1 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 291841
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
141 PM CDT WED OCT 29 2014

.DISCUSSION...
315 AM CDT

SHORT TERM...THROUGH WEDNESDAY NIGHT...FOR THE REMAINDER OF THE NIGHT
AND INTO TUESDAY MORNING...THE MAIN FORECAST ISSUE WILL BE
ASSOCIATED WITH WINDS AND CLOUD COVER,

LATEST SATELLITE IMAGERY SHOWS A STRATOCU DECK SPREADING ACROSS NRN
IL...ASSOCIATED WITH A SECONDARY SURGE OF COOLER AIR AROUND THE SWRN
PERIPHERY OF THE DEEP LOW PRESSURE CENTERED NEAR JAMES BAY.  CLEAR
SKIES PREVAILED OVER THE CWA THROUGH MUCH OF THE EVENING ALLOWING
WINDS TO DIMINISH AS RADIATIONAL COOLING ALLOWED A NOCTURNAL
INVERSION TO FORM...DECOUPLING THE LOWER LEVELS FROM STRONGER WINDS
ALOFT.  HOWEVER...AS THE WRAPAROUND CLOUD COVER OVERSPREADS THE
REGION...WINDS WILL PICK UP ONCE AGAIN...AND PER UPSTREAM OBS.
EXPECT THAT THE WEAKER WSWLY WINDS WILL VEER TO MORE WNWLY AND GUST
UP TO ARND 25KT.  THE STRONGER WINDS AND CLOUD COVER SHOULD ONLY
COVER LOCATIONS GENERALLY NORTH OF THE ILLINOIS AND KANKAKEE
RIVERS...PER LATEST MODEL RH GUIDANCE AND TIMING OF THE LEADING EDGE
OF THE CLOUD DECK...SO THE SRN PORTIONS OF THE CWA SHOULD REMAIN
UNDER MOSTLY CLEAR SKIES WITH LIGHTER WINDS.  TEMPERATURES TODAY
SHOULD BE EVEN LOWER THAN YESTERDAY AS THE REGION REMAINS UNDER NWLY
FLOW AT THE SFC AND ALOFT...WITH PERSISTENT COLD ADVECTION.  HIGHS
WEDNESDAY ARE EXPECTED TO ONLY REACH INTO THE UPPER 40S GENERALLY
NORTH OF THE I-88 CORRIDOR WITH LOWER 50S TO THE SOUTH.

HIGH PRESSURE BUILDING OUT OF THE NRN PLAINS IS EXPECTED TO SPREAD
ACROSS THE MISSISSIPPI VALLEY AND INTO THE WRN PORTIONS OF THE CWA
BY EARLY AFTERNOON AND THEN CONTINUE TO SPREAD EAST ACROSS THE
REMAINDER OF THE CWA THROUGH THE AFTERNOON AND INTO THE EVENING.
THIS SHOULD BRING DECREASING CLOUD COVER AS WELL AS DECREASING WINDS
WITH THE DECREASING PRESSURE GRADIENT.  BY EARLY THIS EVENING...
WINDS SHOULD BECM NEAR CALM. THE CLEARING SKIES AND CALM WINDS
SHOULD ALLOW FOR STRONG RADIATIONAL COOLING...AND WITH DEWPOINTS
EXPECTED TO BE IN THE LOWER 30S...TEMPERATURES SHOULD DROP INTO THE
LOWER 30S AS WELL.  EVEN THE CHICAGO URBAN HEAT ISLAND AREA WILL GET
QUITE CHILLY...WITH LOWS IN THE MIDDLE 30S.

KREIN

THURSDAY THROUGH FRIDAY...
WHILE THE WEEK BEGAN ON A VERY MILD NOTE...WITH TEMPERATURES WELL
INTO THE 70S MON...THE WEEK CLOSES OUT AS NEARLY THE INVERSE OF HOW
IT BEGAN. BROAD MID-LVL TROUGHING WILL CONTINUE ACROSS THE BULK OF
THE GREAT LAKES/OHIO VALLEY REGIONS THUR...WITH A SECONDARY
SHORTWAVE POISED TO SWEEP SOUTHEAST ACROSS THE UPPER
MIDWEST/NORTHERN PLAINS EARLY THUR. GUIDANCE HAS CONTINUED TO
SUGGEST WITH THIS FEATURE THAT A WEAK SFC FEATURE WILL DEVELOP NEAR
NORTHEAST KS...WITH WEAK ADVECTION AHEAD OF THIS SYSTEM SOME LGT
PRECIP MAY OVERSPREAD THE FORECAST AREA.

THE SFC LOW THEN DEEPENS ACROSS LOWER MICHIGAN LATE THUR NGT/EARLY
FRI...AS A POTENT CANADIAN HIGH PRESSURE BEGINS TO SLIDE SOUTH INTO
THE NORTHERN PLAINS. THE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS
QUICKLY FRI MORNING...AND WILL PRODUCE BREEZY CONDITIONS WITH GUSTS
UP TO 40 MPH POSSIBLE MIDDAY FRI. ACCOMPANYING THE STRONG CANADIAN
HIGH WILL BE MUCH COLDER AIR...AS TEMPS WILL LIKELY STRUGGLE TO WARM
BEYOND THE LOW TO MID 40S. GUIDANCE CONTINUES TO ADVERTISE A SLUG OF
850MB TEMPS DROPPING TO -6 TO -10 DEG C MIDDAY FRI/EARLY
AFTN...WHICH MAY BE STRONG ENOUGH TO KEEP TEMPS COOLER IN THE UPR
30S/LOW 40S FRI. THE COMBINATION OF GUSTY WINDS AND TEMPS IN THE LOW
40S...WILL LIKELY CREATE WIND CHILL VALUES AROUND 30-33 DEGREES FRI
AFTN. PRECIP AT THIS TIME SHUD REMAIN IN LIQUID FORM FRI...HOWEVER
AS COLDER AIR ADVECTS IN FROM THE NORTH/NORTHWEST FRI LATE
AFTN/EARLY EVE...WE SHOULD BEGIN TO SEE A MIX OF RAIN/SNOW. LAKE
EFFECT PRECIP LOOKS FAVORABLE AS WELL...HOWEVER GIVEN THE STRONG
WINDS AND REDUCED RESONANCE TIME...THE ONSET WILL LIKELY START
CELLULAR. THEN AS WINDS DIMINISH LATE FRI NGT A FEW BANDS MAY TRY TO
DEVELOP OVER NORTHWEST IND. TEMPS WILL COOL ENOUGH OVERNIGHT TO
CHANGE ALL PRECIP OVER TO SNOW...BUT NOT EXPECTING ANY ACCUMULATIONS
AT THIS TIME. TEMPS FRI NIGHT OVER LAND WILL LIKELY DIP INTO THE
MID/UPR 20S ACROSS THE WESTERN HALF OF THE LAKE WHERE SKIES SHUD
ERODE EARLIER FRI NGT. FURTHER EAST LAKE EFFECT CLOUDS WILL HELP TO
KEEP TEMPS SLIGHTLY WARMER.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
THE WEEKEND WILL START UNSEASONABLY COLD WITH A DEEP 500MB TROUGH
OVER THE EASTERN HALF OF THE CONUS...AND A HIGH AMPLITUDE RIDGE
STRETCHING NORTH THROUGH THE PLAINS INTO GREENLAND. BY THE SECOND
HALF OF THE WEEKEND THE TROUGH BEGINS TO WEAKEN. SFC RIDGE OVER THE
GREAT LAKES SAT WILL SHIFT EAST SUN. GUIDANCE HAS SLOWED THE
DEPARTURE OF THE SFC RIDGE SLIGHTLY...WHICH WILL RESULT IN HOW
QUICKLY THE SECONDARY TROUGH CAN PUSH INTO THE FOUR-CORNERS REGION.
CURRENT THINKING IS THAT A TROUGH WILL PUSH INTO THE SOUTHWEST CONUS
LATE SUN/EARLY MON...WITH A SFC LOW DEVELOPING EARLY NEXT WEEK
ACROSS THE ROCKIES. THIS WILL LIKELY SET THE STAGE FOR A SLOW
MODERATION IN TEMPS EARLY NEXT WEEK ALONG WITH PRECIP CHANCES
INCREASING MON.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NONE.

RODRIGUEZ

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

OVERALL QUIET CONDITIONS FORECAST ACROSS THE TERMINALS THIS
FORECAST PERIOD...AS HIGH PRESSURE TO THE WEST MOVES OVERHEAD. VFR
CEILINGS STILL HOLDING IN PLACE EARLY THIS AFTERNOON BUT DO EXPECT
A SCATTERING TREND TO OCCUR LATE THIS AFTERNOON INTO THE EARLY
EVENING. AS THIS HIGH SHIFTS TOWARDS THE TERMINALS THIS
EVENING...WINDS WILL CONTINUE TO DIMINISH AND LIKELY BECOME CALM
FOR A PERIOD TONIGHT. WITH EXITING HIGH PRESSURE TO THE EAST ON
THURSDAY AND ANOTHER SYSTEM APPROACHING FROM THE
NORTHWEST...SOUTHWEST WINDS WILL PICK UP BY LATE MORNING. EXPECT
THE BULK OF ANY PRECIP ASSOCIATED WITH THIS SYSTEM TO REMAIN JUST
TO THE SOUTH OF THE TERMINALS...BUT WITH VFR CEILINGS RETURNING
LATER IN THE AFTERNOON.

RODRIGUEZ

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

RODRIGUEZ

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

* THURSDAY NIGHT...SLIGHT CHANCE OF SHRA LATE. STRONG NWLY WINDS
  DEVELOPING LATE.

* FRIDAY...SLIGHT CHANCE OF SHRA EARLY SLIGHT CHANCE SHRA/SHSN MIX
  LATE. STRONG/GUSTY NORTH WINDS.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS.

* SUNDAY....VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

* TUESDAY...CHANCE OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
141 PM CDT

HIGH PRESSURE WILL MOVE ACROSS THE REGION TONIGHT RESULTING IN
EASING WINDS AND WAVES TONIGHT AND THURSDAY. SHARP UPPER TROUGH WILL
DIG INTO THE GREAT LAKES REGION THURSDAY NIGHT WITH SURFACE LOW
DEVELOPING OVER THE EASTERN GREAT LAKES. THE DEVELOPING LOW AND A
STRONG 1038MB HIGH OVER THE NORTHERN PLAINS WILL RESULT IN A
DRAMATIC INCREASE IN THE PRESSURE GRADIENT OVER THE LAKE LATE
THURSDAY NIGHT AND ESPECIALLY FRIDAY. IN ADDITION TO THE STRONG
GRADIENT...VERY COLD AIR MOVING OVER THE LAKE WILL PRODUCE STRONG TO
EXTREME INSTABILITY RESULTING IN DEEP AND EFFICIENT MIXING OF THE
HIGHER WINDS TO THE SURFACE. FORECAST SOUNDINGS SUGGEST THAT A
SEVERAL HOUR WINDOW OF STORM FORCE WINDS ARE POSSIBLE
FRIDAY...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE...HOWEVER ENOUGH
MODEL UNCERTAINTY EXISTS TO HOLD OFF ON A STORM WATCH OR WARNING AT
THIS TIME BUT WILL ADD A FEW STORM FORCE GUSTS TO GLF AND GRIDS.
WINDS WILL SUBSIDE SATURDAY AND THEN BACK WITH FAIRLY STRONG
SOUTHERLY WINDS DEVELOPING LATE SUNDAY AND CONTINUING THROUGH
TUESDAY.

IZZI

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 291759
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1259 PM CDT WED OCT 29 2014

.DISCUSSION...
315 AM CDT

SHORT TERM...THROUGH WEDNESDAY NIGHT...FOR THE REMAINDER OF THE NIGHT
AND INTO TUESDAY MORNING...THE MAIN FORECAST ISSUE WILL BE
ASSOCIATED WITH WINDS AND CLOUD COVER,

LATEST SATELLITE IMAGERY SHOWS A STRATOCU DECK SPREADING ACROSS NRN
IL...ASSOCIATED WITH A SECONDARY SURGE OF COOLER AIR AROUND THE SWRN
PERIPHERY OF THE DEEP LOW PRESSURE CENTERED NEAR JAMES BAY.  CLEAR
SKIES PREVAILED OVER THE CWA THROUGH MUCH OF THE EVENING ALLOWING
WINDS TO DIMINISH AS RADIATIONAL COOLING ALLOWED A NOCTURNAL
INVERSION TO FORM...DECOUPLING THE LOWER LEVELS FROM STRONGER WINDS
ALOFT.  HOWEVER...AS THE WRAPAROUND CLOUD COVER OVERSPREADS THE
REGION...WINDS WILL PICK UP ONCE AGAIN...AND PER UPSTREAM OBS.
EXPECT THAT THE WEAKER WSWLY WINDS WILL VEER TO MORE WNWLY AND GUST
UP TO ARND 25KT.  THE STRONGER WINDS AND CLOUD COVER SHOULD ONLY
COVER LOCATIONS GENERALLY NORTH OF THE ILLINOIS AND KANKAKEE
RIVERS...PER LATEST MODEL RH GUIDANCE AND TIMING OF THE LEADING EDGE
OF THE CLOUD DECK...SO THE SRN PORTIONS OF THE CWA SHOULD REMAIN
UNDER MOSTLY CLEAR SKIES WITH LIGHTER WINDS.  TEMPERATURES TODAY
SHOULD BE EVEN LOWER THAN YESTERDAY AS THE REGION REMAINS UNDER NWLY
FLOW AT THE SFC AND ALOFT...WITH PERSISTENT COLD ADVECTION.  HIGHS
WEDNESDAY ARE EXPECTED TO ONLY REACH INTO THE UPPER 40S GENERALLY
NORTH OF THE I-88 CORRIDOR WITH LOWER 50S TO THE SOUTH.

HIGH PRESSURE BUILDING OUT OF THE NRN PLAINS IS EXPECTED TO SPREAD
ACROSS THE MISSISSIPPI VALLEY AND INTO THE WRN PORTIONS OF THE CWA
BY EARLY AFTERNOON AND THEN CONTINUE TO SPREAD EAST ACROSS THE
REMAINDER OF THE CWA THROUGH THE AFTERNOON AND INTO THE EVENING.
THIS SHOULD BRING DECREASING CLOUD COVER AS WELL AS DECREASING WINDS
WITH THE DECREASING PRESSURE GRADIENT.  BY EARLY THIS EVENING...
WINDS SHOULD BECM NEAR CALM. THE CLEARING SKIES AND CALM WINDS
SHOULD ALLOW FOR STRONG RADIATIONAL COOLING...AND WITH DEWPOINTS
EXPECTED TO BE IN THE LOWER 30S...TEMPERATURES SHOULD DROP INTO THE
LOWER 30S AS WELL.  EVEN THE CHICAGO URBAN HEAT ISLAND AREA WILL GET
QUITE CHILLY...WITH LOWS IN THE MIDDLE 30S.

KREIN

THURSDAY THROUGH FRIDAY...
WHILE THE WEEK BEGAN ON A VERY MILD NOTE...WITH TEMPERATURES WELL
INTO THE 70S MON...THE WEEK CLOSES OUT AS NEARLY THE INVERSE OF HOW
IT BEGAN. BROAD MID-LVL TROUGHING WILL CONTINUE ACROSS THE BULK OF
THE GREAT LAKES/OHIO VALLEY REGIONS THUR...WITH A SECONDARY
SHORTWAVE POISED TO SWEEP SOUTHEAST ACROSS THE UPPER
MIDWEST/NORTHERN PLAINS EARLY THUR. GUIDANCE HAS CONTINUED TO
SUGGEST WITH THIS FEATURE THAT A WEAK SFC FEATURE WILL DEVELOP NEAR
NORTHEAST KS...WITH WEAK ADVECTION AHEAD OF THIS SYSTEM SOME LGT
PRECIP MAY OVERSPREAD THE FORECAST AREA.

THE SFC LOW THEN DEEPENS ACROSS LOWER MICHIGAN LATE THUR NGT/EARLY
FRI...AS A POTENT CANADIAN HIGH PRESSURE BEGINS TO SLIDE SOUTH INTO
THE NORTHERN PLAINS. THE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS
QUICKLY FRI MORNING...AND WILL PRODUCE BREEZY CONDITIONS WITH GUSTS
UP TO 40 MPH POSSIBLE MIDDAY FRI. ACCOMPANYING THE STRONG CANADIAN
HIGH WILL BE MUCH COLDER AIR...AS TEMPS WILL LIKELY STRUGGLE TO WARM
BEYOND THE LOW TO MID 40S. GUIDANCE CONTINUES TO ADVERTISE A SLUG OF
850MB TEMPS DROPPING TO -6 TO -10 DEG C MIDDAY FRI/EARLY
AFTN...WHICH MAY BE STRONG ENOUGH TO KEEP TEMPS COOLER IN THE UPR
30S/LOW 40S FRI. THE COMBINATION OF GUSTY WINDS AND TEMPS IN THE LOW
40S...WILL LIKELY CREATE WIND CHILL VALUES AROUND 30-33 DEGREES FRI
AFTN. PRECIP AT THIS TIME SHUD REMAIN IN LIQUID FORM FRI...HOWEVER
AS COLDER AIR ADVECTS IN FROM THE NORTH/NORTHWEST FRI LATE
AFTN/EARLY EVE...WE SHOULD BEGIN TO SEE A MIX OF RAIN/SNOW. LAKE
EFFECT PRECIP LOOKS FAVORABLE AS WELL...HOWEVER GIVEN THE STRONG
WINDS AND REDUCED RESONANCE TIME...THE ONSET WILL LIKELY START
CELLULAR. THEN AS WINDS DIMINISH LATE FRI NGT A FEW BANDS MAY TRY TO
DEVELOP OVER NORTHWEST IND. TEMPS WILL COOL ENOUGH OVERNIGHT TO
CHANGE ALL PRECIP OVER TO SNOW...BUT NOT EXPECTING ANY ACCUMULATIONS
AT THIS TIME. TEMPS FRI NIGHT OVER LAND WILL LIKELY DIP INTO THE
MID/UPR 20S ACROSS THE WESTERN HALF OF THE LAKE WHERE SKIES SHUD
ERODE EARLIER FRI NGT. FURTHER EAST LAKE EFFECT CLOUDS WILL HELP TO
KEEP TEMPS SLIGHTLY WARMER.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
THE WEEKEND WILL START UNSEASONABLY COLD WITH A DEEP 500MB TROUGH
OVER THE EASTERN HALF OF THE CONUS...AND A HIGH AMPLITUDE RIDGE
STRETCHING NORTH THROUGH THE PLAINS INTO GREENLAND. BY THE SECOND
HALF OF THE WEEKEND THE TROUGH BEGINS TO WEAKEN. SFC RIDGE OVER THE
GREAT LAKES SAT WILL SHIFT EAST SUN. GUIDANCE HAS SLOWED THE
DEPARTURE OF THE SFC RIDGE SLIGHTLY...WHICH WILL RESULT IN HOW
QUICKLY THE SECONDARY TROUGH CAN PUSH INTO THE FOUR-CORNERS REGION.
CURRENT THINKING IS THAT A TROUGH WILL PUSH INTO THE SOUTHWEST CONUS
LATE SUN/EARLY MON...WITH A SFC LOW DEVELOPING EARLY NEXT WEEK
ACROSS THE ROCKIES. THIS WILL LIKELY SET THE STAGE FOR A SLOW
MODERATION IN TEMPS EARLY NEXT WEEK ALONG WITH PRECIP CHANCES
INCREASING MON.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NONE.

RODRIGUEZ

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

OVERALL QUIET CONDITIONS FORECAST ACROSS THE TERMINALS THIS
FORECAST PERIOD...AS HIGH PRESSURE TO THE WEST MOVES OVERHEAD. VFR
CEILINGS STILL HOLDING IN PLACE EARLY THIS AFTERNOON BUT DO EXPECT
A SCATTERING TREND TO OCCUR LATE THIS AFTERNOON INTO THE EARLY
EVENING. AS THIS HIGH SHIFTS TOWARDS THE TERMINALS THIS
EVENING...WINDS WILL CONTINUE TO DIMINISH AND LIKELY BECOME CALM
FOR A PERIOD TONIGHT. WITH EXITING HIGH PRESSURE TO THE EAST ON
THURSDAY AND ANOTHER SYSTEM APPROACHING FROM THE
NORTHWEST...SOUTHWEST WINDS WILL PICK UP BY LATE MORNING. EXPECT
THE BULK OF ANY PRECIP ASSOCIATED WITH THIS SYSTEM TO REMAIN JUST
TO THE SOUTH OF THE TERMINALS...BUT WITH VFR CEILINGS RETURNING
LATER IN THE AFTERNOON.

RODRIGUEZ


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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

RODRIGUEZ

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

* THURSDAY NIGHT...SLIGHT CHANCE OF SHRA LATE. STRONG NWLY WINDS
  DEVELOPING LATE.

* FRIDAY...SLIGHT CHANCE OF SHRA EARLY SLIGHT CHANCE SHRA/SHSN MIX
  LATE. STRONG/GUSTY NORTH WINDS.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS.

* SUNDAY....VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

* TUESDAY...CHANCE OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
230 AM CDT

DEEPENING LOW OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST AWAY
FROM THE GREAT LAKES...AS HIGH PRESSURE SLOWLY SLIDES SOUTHEAST FROM
THE NORTHERN PLAINS INTO THE MID-MISSOURI VALLEY. THIS HIGH PRESSURE
WILL DIMINISH WINDS ACROSS LAKE MICHIGAN TONIGHT/THUR MORNING. THEN
A WEAK LOW WILL DEVELOP ACROSS THE CENTRAL PLAINS EARLY THUR AND
QUICKLY SLIDE EAST TOWARDS LAKE MICHIGAN...BEFORE DEEPENING TO A
STRONGER LOW PRESSURE OVER LOWER MICHIGAN THUR NGT/EARLY FRI.

THEN THE TIME PERIOD OF GREATEST CONCERN WILL BE FRI WITH A VERY
POTENT CANADIAN HIGH PRESSURE REGION POISED TO SLIDE SOUTH INTO THE
NORTHERN PLAINS FRI MORNING. THE GRADIENT BETWEEN THE LOW/HIGH
CONTINUES TO BE SUPPORTIVE OF GENERATING GALES TO 40KT AND POSSIBLY
45KT AROUND 9Z FRI MORNING ACROSS THE NORTHERN HALF OF THE
LAKE...AND LIKELY DEVELOP FURTHER SOUTH AROUND DAYBREAK FRI OR
SHORTLY AFTER DAYBREAK FRI.

GUIDANCE HAS REMAINED CONSISTENT WITH HIGH CONFIDENCE IN NORTH GALES
40-45KTS DEVELOPING FRI...SO HAVE OPTED TO JUST JUMP TO A GALE
WARNING RATHER THAN A WATCH. THERE IS A SMALL WINDOW MIDDAY FRI
WHERE A FEW STORM FORCE GUSTS COULD OCCUR...BUT THIS IS A LOW
CONFIDENCE FOR ANY DURATION OF STORM FORCE WINDS. WITH THE NORTH
GALES...AND FOR A DECENT DURATION...IT IS POSSIBLE THAT WAVES COULD
BE SUBSTANTIAL ENOUGH TO PRODUCE THE NEED FOR BEACH HAZARDS ALONG
THE INDIANA SHORELINE FRI AS WELL.

HIGH PRESSURE WILL THEN BUILD ACROSS THE LAKE LATE FRI NGT AND
STEADILY DIMINISH THE WINDS. WINDS/WAVES WILL FURTHER DIMINISH
SAT/SUN AS HIGH PRESSURE REMAINS OVER THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 291613
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1113 AM CDT WED OCT 29 2014

.DISCUSSION...
315 AM CDT

SHORT TERM...THROUGH WEDNESDAY NIGHT...FOR THE REMAINDER OF THE NIGHT
AND INTO TUESDAY MORNING...THE MAIN FORECAST ISSUE WILL BE
ASSOCIATED WITH WINDS AND CLOUD COVER,

LATEST SATELLITE IMAGERY SHOWS A STRATOCU DECK SPREADING ACROSS NRN
IL...ASSOCIATED WITH A SECONDARY SURGE OF COOLER AIR AROUND THE SWRN
PERIPHERY OF THE DEEP LOW PRESSURE CENTERED NEAR JAMES BAY.  CLEAR
SKIES PREVAILED OVER THE CWA THROUGH MUCH OF THE EVENING ALLOWING
WINDS TO DIMINISH AS RADIATIONAL COOLING ALLOWED A NOCTURNAL
INVERSION TO FORM...DECOUPLING THE LOWER LEVELS FROM STRONGER WINDS
ALOFT.  HOWEVER...AS THE WRAPAROUND CLOUD COVER OVERSPREADS THE
REGION...WINDS WILL PICK UP ONCE AGAIN...AND PER UPSTREAM OBS.
EXPECT THAT THE WEAKER WSWLY WINDS WILL VEER TO MORE WNWLY AND GUST
UP TO ARND 25KT.  THE STRONGER WINDS AND CLOUD COVER SHOULD ONLY
COVER LOCATIONS GENERALLY NORTH OF THE ILLINOIS AND KANKAKEE
RIVERS...PER LATEST MODEL RH GUIDANCE AND TIMING OF THE LEADING EDGE
OF THE CLOUD DECK...SO THE SRN PORTIONS OF THE CWA SHOULD REMAIN
UNDER MOSTLY CLEAR SKIES WITH LIGHTER WINDS.  TEMPERATURES TODAY
SHOULD BE EVEN LOWER THAN YESTERDAY AS THE REGION REMAINS UNDER NWLY
FLOW AT THE SFC AND ALOFT...WITH PERSISTENT COLD ADVECTION.  HIGHS
WEDNESDAY ARE EXPECTED TO ONLY REACH INTO THE UPPER 40S GENERALLY
NORTH OF THE I-88 CORRIDOR WITH LOWER 50S TO THE SOUTH.

HIGH PRESSURE BUILDING OUT OF THE NRN PLAINS IS EXPECTED TO SPREAD
ACROSS THE MISSISSIPPI VALLEY AND INTO THE WRN PORTIONS OF THE CWA
BY EARLY AFTERNOON AND THEN CONTINUE TO SPREAD EAST ACROSS THE
REMAINDER OF THE CWA THROUGH THE AFTERNOON AND INTO THE EVENING.
THIS SHOULD BRING DECREASING CLOUD COVER AS WELL AS DECREASING WINDS
WITH THE DECREASING PRESSURE GRADIENT.  BY EARLY THIS EVENING...
WINDS SHOULD BECM NEAR CALM. THE CLEARING SKIES AND CALM WINDS
SHOULD ALLOW FOR STRONG RADIATIONAL COOLING...AND WITH DEWPOINTS
EXPECTED TO BE IN THE LOWER 30S...TEMPERATURES SHOULD DROP INTO THE
LOWER 30S AS WELL.  EVEN THE CHICAGO URBAN HEAT ISLAND AREA WILL GET
QUITE CHILLY...WITH LOWS IN THE MIDDLE 30S.

KREIN

THURSDAY THROUGH FRIDAY...
WHILE THE WEEK BEGAN ON A VERY MILD NOTE...WITH TEMPERATURES WELL
INTO THE 70S MON...THE WEEK CLOSES OUT AS NEARLY THE INVERSE OF HOW
IT BEGAN. BROAD MID-LVL TROUGHING WILL CONTINUE ACROSS THE BULK OF
THE GREAT LAKES/OHIO VALLEY REGIONS THUR...WITH A SECONDARY
SHORTWAVE POISED TO SWEEP SOUTHEAST ACROSS THE UPPER
MIDWEST/NORTHERN PLAINS EARLY THUR. GUIDANCE HAS CONTINUED TO
SUGGEST WITH THIS FEATURE THAT A WEAK SFC FEATURE WILL DEVELOP NEAR
NORTHEAST KS...WITH WEAK ADVECTION AHEAD OF THIS SYSTEM SOME LGT
PRECIP MAY OVERSPREAD THE FORECAST AREA.

THE SFC LOW THEN DEEPENS ACROSS LOWER MICHIGAN LATE THUR NGT/EARLY
FRI...AS A POTENT CANADIAN HIGH PRESSURE BEGINS TO SLIDE SOUTH INTO
THE NORTHERN PLAINS. THE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS
QUICKLY FRI MORNING...AND WILL PRODUCE BREEZY CONDITIONS WITH GUSTS
UP TO 40 MPH POSSIBLE MIDDAY FRI. ACCOMPANYING THE STRONG CANADIAN
HIGH WILL BE MUCH COLDER AIR...AS TEMPS WILL LIKELY STRUGGLE TO WARM
BEYOND THE LOW TO MID 40S. GUIDANCE CONTINUES TO ADVERTISE A SLUG OF
850MB TEMPS DROPPING TO -6 TO -10 DEG C MIDDAY FRI/EARLY
AFTN...WHICH MAY BE STRONG ENOUGH TO KEEP TEMPS COOLER IN THE UPR
30S/LOW 40S FRI. THE COMBINATION OF GUSTY WINDS AND TEMPS IN THE LOW
40S...WILL LIKELY CREATE WIND CHILL VALUES AROUND 30-33 DEGREES FRI
AFTN. PRECIP AT THIS TIME SHUD REMAIN IN LIQUID FORM FRI...HOWEVER
AS COLDER AIR ADVECTS IN FROM THE NORTH/NORTHWEST FRI LATE
AFTN/EARLY EVE...WE SHOULD BEGIN TO SEE A MIX OF RAIN/SNOW. LAKE
EFFECT PRECIP LOOKS FAVORABLE AS WELL...HOWEVER GIVEN THE STRONG
WINDS AND REDUCED RESONANCE TIME...THE ONSET WILL LIKELY START
CELLULAR. THEN AS WINDS DIMINISH LATE FRI NGT A FEW BANDS MAY TRY TO
DEVELOP OVER NORTHWEST IND. TEMPS WILL COOL ENOUGH OVERNIGHT TO
CHANGE ALL PRECIP OVER TO SNOW...BUT NOT EXPECTING ANY ACCUMULATIONS
AT THIS TIME. TEMPS FRI NIGHT OVER LAND WILL LIKELY DIP INTO THE
MID/UPR 20S ACROSS THE WESTERN HALF OF THE LAKE WHERE SKIES SHUD
ERODE EARLIER FRI NGT. FURTHER EAST LAKE EFFECT CLOUDS WILL HELP TO
KEEP TEMPS SLIGHTLY WARMER.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
THE WEEKEND WILL START UNSEASONABLY COLD WITH A DEEP 500MB TROUGH
OVER THE EASTERN HALF OF THE CONUS...AND A HIGH AMPLITUDE RIDGE
STRETCHING NORTH THROUGH THE PLAINS INTO GREENLAND. BY THE SECOND
HALF OF THE WEEKEND THE TROUGH BEGINS TO WEAKEN. SFC RIDGE OVER THE
GREAT LAKES SAT WILL SHIFT EAST SUN. GUIDANCE HAS SLOWED THE
DEPARTURE OF THE SFC RIDGE SLIGHTLY...WHICH WILL RESULT IN HOW
QUICKLY THE SECONDARY TROUGH CAN PUSH INTO THE FOUR-CORNERS REGION.
CURRENT THINKING IS THAT A TROUGH WILL PUSH INTO THE SOUTHWEST CONUS
LATE SUN/EARLY MON...WITH A SFC LOW DEVELOPING EARLY NEXT WEEK
ACROSS THE ROCKIES. THIS WILL LIKELY SET THE STAGE FOR A SLOW
MODERATION IN TEMPS EARLY NEXT WEEK ALONG WITH PRECIP CHANCES
INCREASING MON.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NONE.

RODRIGUEZ

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

AS THE DEEP LOW PRESSURE SYSTEM CONTINUES TO TRACK NEWD THROUGH
CANADA...A SECONDARY SURGE OF COOLER AIR AND A BKN-OVC STRATOCU
DECK HAS OVERSPREAD THE REGION. THE SECONDARY SURGE OF COOLER AIR
AND INCREASED COLD ADVECTION WILL BRING GUSTS TO ARND 25KT. HIGH
PRESSURE WILL BUILD ACROSS THE PLAINS AND SPREAD EAST OF THE
MISSISSIPPI RIVER THROUGH THE AFTERNOON...LEADING TO CLEARING
SKIES AND DIMINISHING WINDS. DURG THE EARLY EVENING HOURS...THE
HIGH WILL BE RIGHT ON TOP OF THE AREA...AND WINDS SHOULD BECOME
LGT/VRBL UNDER CLEAR SKIES... WHICH SHOULD THEN BE THE PREVAILING
CONDITION THROUGH THE REMAINDER OF THE FORECAST PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

RODRIGUEZ

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

* THURSDAY NIGHT...SLIGHT CHANCE OF SHRA LATE. STRONG NWLY WINDS
  DEVELOPING LATE.

* FRIDAY...SLIGHT CHANCE OF SHRA EARLY SLIGHT CHANCE SHRA/SHSN MIX
  LATE. STRONG/GUSTY NORTH WINDS.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS.

* SUNDAY....VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

* TUESDAY...CHANCE OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
230 AM CDT

DEEPENING LOW OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST AWAY
FROM THE GREAT LAKES...AS HIGH PRESSURE SLOWLY SLIDES SOUTHEAST FROM
THE NORTHERN PLAINS INTO THE MID-MISSOURI VALLEY. THIS HIGH PRESSURE
WILL DIMINISH WINDS ACROSS LAKE MICHIGAN TONIGHT/THUR MORNING. THEN
A WEAK LOW WILL DEVELOP ACROSS THE CENTRAL PLAINS EARLY THUR AND
QUICKLY SLIDE EAST TOWARDS LAKE MICHIGAN...BEFORE DEEPENING TO A
STRONGER LOW PRESSURE OVER LOWER MICHIGAN THUR NGT/EARLY FRI.

THEN THE TIME PERIOD OF GREATEST CONCERN WILL BE FRI WITH A VERY
POTENT CANADIAN HIGH PRESSURE REGION POISED TO SLIDE SOUTH INTO THE
NORTHERN PLAINS FRI MORNING. THE GRADIENT BETWEEN THE LOW/HIGH
CONTINUES TO BE SUPPORTIVE OF GENERATING GALES TO 40KT AND POSSIBLY
45KT AROUND 9Z FRI MORNING ACROSS THE NORTHERN HALF OF THE
LAKE...AND LIKELY DEVELOP FURTHER SOUTH AROUND DAYBREAK FRI OR
SHORTLY AFTER DAYBREAK FRI.

GUIDANCE HAS REMAINED CONSISTENT WITH HIGH CONFIDENCE IN NORTH GALES
40-45KTS DEVELOPING FRI...SO HAVE OPTED TO JUST JUMP TO A GALE
WARNING RATHER THAN A WATCH. THERE IS A SMALL WINDOW MIDDAY FRI
WHERE A FEW STORM FORCE GUSTS COULD OCCUR...BUT THIS IS A LOW
CONFIDENCE FOR ANY DURATION OF STORM FORCE WINDS. WITH THE NORTH
GALES...AND FOR A DECENT DURATION...IT IS POSSIBLE THAT WAVES COULD
BE SUBSTANTIAL ENOUGH TO PRODUCE THE NEED FOR BEACH HAZARDS ALONG
THE INDIANA SHORELINE FRI AS WELL.

HIGH PRESSURE WILL THEN BUILD ACROSS THE LAKE LATE FRI NGT AND
STEADILY DIMINISH THE WINDS. WINDS/WAVES WILL FURTHER DIMINISH
SAT/SUN AS HIGH PRESSURE REMAINS OVER THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 291411
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
911 AM CDT WED OCT 29 2014

.DISCUSSION...
315 AM CDT

SHORT TERM...THROUGH WEDNESDAY NIGHT...FOR THE REMAINDER OF THE NIGHT
AND INTO TUESDAY MORNING...THE MAIN FORECAST ISSUE WILL BE
ASSOCIATED WITH WINDS AND CLOUD COVER,

LATEST SATELLITE IMAGERY SHOWS A STRATOCU DECK SPREADING ACROSS NRN
IL...ASSOCIATED WITH A SECONDARY SURGE OF COOLER AIR AROUND THE SWRN
PERIPHERY OF THE DEEP LOW PRESSURE CENTERED NEAR JAMES BAY.  CLEAR
SKIES PREVAILED OVER THE CWA THROUGH MUCH OF THE EVENING ALLOWING
WINDS TO DIMINISH AS RADIATIONAL COOLING ALLOWED A NOCTURNAL
INVERSION TO FORM...DECOUPLING THE LOWER LEVELS FROM STRONGER WINDS
ALOFT.  HOWEVER...AS THE WRAPAROUND CLOUD COVER OVERSPREADS THE
REGION...WINDS WILL PICK UP ONCE AGAIN...AND PER UPSTREAM OBS.
EXPECT THAT THE WEAKER WSWLY WINDS WILL VEER TO MORE WNWLY AND GUST
UP TO ARND 25KT.  THE STRONGER WINDS AND CLOUD COVER SHOULD ONLY
COVER LOCATIONS GENERALLY NORTH OF THE ILLINOIS AND KANKAKEE
RIVERS...PER LATEST MODEL RH GUIDANCE AND TIMING OF THE LEADING EDGE
OF THE CLOUD DECK...SO THE SRN PORTIONS OF THE CWA SHOULD REMAIN
UNDER MOSTLY CLEAR SKIES WITH LIGHTER WINDS.  TEMPERATURES TODAY
SHOULD BE EVEN LOWER THAN YESTERDAY AS THE REGION REMAINS UNDER NWLY
FLOW AT THE SFC AND ALOFT...WITH PERSISTENT COLD ADVECTION.  HIGHS
WEDNESDAY ARE EXPECTED TO ONLY REACH INTO THE UPPER 40S GENERALLY
NORTH OF THE I-88 CORRIDOR WITH LOWER 50S TO THE SOUTH.

HIGH PRESSURE BUILDING OUT OF THE NRN PLAINS IS EXPECTED TO SPREAD
ACROSS THE MISSISSIPPI VALLEY AND INTO THE WRN PORTIONS OF THE CWA
BY EARLY AFTERNOON AND THEN CONTINUE TO SPREAD EAST ACROSS THE
REMAINDER OF THE CWA THROUGH THE AFTERNOON AND INTO THE EVENING.
THIS SHOULD BRING DECREASING CLOUD COVER AS WELL AS DECREASING WINDS
WITH THE DECREASING PRESSURE GRADIENT.  BY EARLY THIS EVENING...
WINDS SHOULD BECM NEAR CALM. THE CLEARING SKIES AND CALM WINDS
SHOULD ALLOW FOR STRONG RADIATIONAL COOLING...AND WITH DEWPOINTS
EXPECTED TO BE IN THE LOWER 30S...TEMPERATURES SHOULD DROP INTO THE
LOWER 30S AS WELL.  EVEN THE CHICAGO URBAN HEAT ISLAND AREA WILL GET
QUITE CHILLY...WITH LOWS IN THE MIDDLE 30S.

KREIN

THURSDAY THROUGH FRIDAY...
WHILE THE WEEK BEGAN ON A VERY MILD NOTE...WITH TEMPERATURES WELL
INTO THE 70S MON...THE WEEK CLOSES OUT AS NEARLY THE INVERSE OF HOW
IT BEGAN. BROAD MID-LVL TROUGHING WILL CONTINUE ACROSS THE BULK OF
THE GREAT LAKES/OHIO VALLEY REGIONS THUR...WITH A SECONDARY
SHORTWAVE POISED TO SWEEP SOUTHEAST ACROSS THE UPPER
MIDWEST/NORTHERN PLAINS EARLY THUR. GUIDANCE HAS CONTINUED TO
SUGGEST WITH THIS FEATURE THAT A WEAK SFC FEATURE WILL DEVELOP NEAR
NORTHEAST KS...WITH WEAK ADVECTION AHEAD OF THIS SYSTEM SOME LGT
PRECIP MAY OVERSPREAD THE FORECAST AREA.

THE SFC LOW THEN DEEPENS ACROSS LOWER MICHIGAN LATE THUR NGT/EARLY
FRI...AS A POTENT CANADIAN HIGH PRESSURE BEGINS TO SLIDE SOUTH INTO
THE NORTHERN PLAINS. THE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS
QUICKLY FRI MORNING...AND WILL PRODUCE BREEZY CONDITIONS WITH GUSTS
UP TO 40 MPH POSSIBLE MIDDAY FRI. ACCOMPANYING THE STRONG CANADIAN
HIGH WILL BE MUCH COLDER AIR...AS TEMPS WILL LIKELY STRUGGLE TO WARM
BEYOND THE LOW TO MID 40S. GUIDANCE CONTINUES TO ADVERTISE A SLUG OF
850MB TEMPS DROPPING TO -6 TO -10 DEG C MIDDAY FRI/EARLY
AFTN...WHICH MAY BE STRONG ENOUGH TO KEEP TEMPS COOLER IN THE UPR
30S/LOW 40S FRI. THE COMBINATION OF GUSTY WINDS AND TEMPS IN THE LOW
40S...WILL LIKELY CREATE WIND CHILL VALUES AROUND 30-33 DEGREES FRI
AFTN. PRECIP AT THIS TIME SHUD REMAIN IN LIQUID FORM FRI...HOWEVER
AS COLDER AIR ADVECTS IN FROM THE NORTH/NORTHWEST FRI LATE
AFTN/EARLY EVE...WE SHOULD BEGIN TO SEE A MIX OF RAIN/SNOW. LAKE
EFFECT PRECIP LOOKS FAVORABLE AS WELL...HOWEVER GIVEN THE STRONG
WINDS AND REDUCED RESONANCE TIME...THE ONSET WILL LIKELY START
CELLULAR. THEN AS WINDS DIMINISH LATE FRI NGT A FEW BANDS MAY TRY TO
DEVELOP OVER NORTHWEST IND. TEMPS WILL COOL ENOUGH OVERNIGHT TO
CHANGE ALL PRECIP OVER TO SNOW...BUT NOT EXPECTING ANY ACCUMULATIONS
AT THIS TIME. TEMPS FRI NIGHT OVER LAND WILL LIKELY DIP INTO THE
MID/UPR 20S ACROSS THE WESTERN HALF OF THE LAKE WHERE SKIES SHUD
ERODE EARLIER FRI NGT. FURTHER EAST LAKE EFFECT CLOUDS WILL HELP TO
KEEP TEMPS SLIGHTLY WARMER.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
THE WEEKEND WILL START UNSEASONABLY COLD WITH A DEEP 500MB TROUGH
OVER THE EASTERN HALF OF THE CONUS...AND A HIGH AMPLITUDE RIDGE
STRETCHING NORTH THROUGH THE PLAINS INTO GREENLAND. BY THE SECOND
HALF OF THE WEEKEND THE TROUGH BEGINS TO WEAKEN. SFC RIDGE OVER THE
GREAT LAKES SAT WILL SHIFT EAST SUN. GUIDANCE HAS SLOWED THE
DEPARTURE OF THE SFC RIDGE SLIGHTLY...WHICH WILL RESULT IN HOW
QUICKLY THE SECONDARY TROUGH CAN PUSH INTO THE FOUR-CORNERS REGION.
CURRENT THINKING IS THAT A TROUGH WILL PUSH INTO THE SOUTHWEST CONUS
LATE SUN/EARLY MON...WITH A SFC LOW DEVELOPING EARLY NEXT WEEK
ACROSS THE ROCKIES. THIS WILL LIKELY SET THE STAGE FOR A SLOW
MODERATION IN TEMPS EARLY NEXT WEEK ALONG WITH PRECIP CHANCES
INCREASING MON.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* NONE.

RODRIGUEZ

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

AS THE DEEP LOW PRESSURE SYSTEM CONTINUES TO TRACK NEWD THROUGH
CANADA...A SECONDARY SURGE OF COOLER AIR AND A BKN-OVC STRATOCU
DECK HAS OVERSPREAD THE REGION. THE SECONDARY SURGE OF COOLER AIR
AND INCREASED COLD ADVECTION WILL BRING GUSTS TO ARND 25KT. HIGH
PRESSURE WILL BUILD ACROSS THE PLAINS AND SPREAD EAST OF THE
MISSISSIPPI RIVER THROUGH THE AFTERNOON...LEADING TO CLEARING
SKIES AND DIMINISHING WINDS. DURG THE EARLY EVENING HOURS...THE
HIGH WILL BE RIGHT ON TOP OF THE AREA...AND WINDS SHOULD BECOME
LGT/VRBL UNDER CLEAR SKIES... WHICH SHOULD THEN BE THE PREVAILING
CONDITION THROUGH THE REMAINDER OF THE FORECAST PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

RODRIGUEZ

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

* THURSDAY NIGHT...SLIGHT CHANCE OF SHRA LATE. STRONG NWLY WINDS
  DEVELOPING LATE.

* FRIDAY...SLIGHT CHANCE OF SHRA EARLY SLIGHT CHANCE SHRA/SHSN MIX
  LATE. STRONG/GUSTY NORTH WINDS.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS.

* SUNDAY....VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

* TUESDAY...CHANCE OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
230 AM CDT

DEEPENING LOW OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST AWAY
FROM THE GREAT LAKES...AS HIGH PRESSURE SLOWLY SLIDES SOUTHEAST FROM
THE NORTHERN PLAINS INTO THE MID-MISSOURI VALLEY. THIS HIGH PRESSURE
WILL DIMINISH WINDS ACROSS LAKE MICHIGAN TONIGHT/THUR MORNING. THEN
A WEAK LOW WILL DEVELOP ACROSS THE CENTRAL PLAINS EARLY THUR AND
QUICKLY SLIDE EAST TOWARDS LAKE MICHIGAN...BEFORE DEEPENING TO A
STRONGER LOW PRESSURE OVER LOWER MICHIGAN THUR NGT/EARLY FRI.

THEN THE TIME PERIOD OF GREATEST CONCERN WILL BE FRI WITH A VERY
POTENT CANADIAN HIGH PRESSURE REGION POISED TO SLIDE SOUTH INTO THE
NORTHERN PLAINS FRI MORNING. THE GRADIENT BETWEEN THE LOW/HIGH
CONTINUES TO BE SUPPORTIVE OF GENERATING GALES TO 40KT AND POSSIBLY
45KT AROUND 9Z FRI MORNING ACROSS THE NORTHERN HALF OF THE
LAKE...AND LIKELY DEVELOP FURTHER SOUTH AROUND DAYBREAK FRI OR
SHORTLY AFTER DAYBREAK FRI.

GUIDANCE HAS REMAINED CONSISTENT WITH HIGH CONFIDENCE IN NORTH GALES
40-45KTS DEVELOPING FRI...SO HAVE OPTED TO JUST JUMP TO A GALE
WARNING RATHER THAN A WATCH. THERE IS A SMALL WINDOW MIDDAY FRI
WHERE A FEW STORM FORCE GUSTS COULD OCCUR...BUT THIS IS A LOW
CONFIDENCE FOR ANY DURATION OF STORM FORCE WINDS. WITH THE NORTH
GALES...AND FOR A DECENT DURATION...IT IS POSSIBLE THAT WAVES COULD
BE SUBSTANTIAL ENOUGH TO PRODUCE THE NEED FOR BEACH HAZARDS ALONG
THE INDIANA SHORELINE FRI AS WELL.

HIGH PRESSURE WILL THEN BUILD ACROSS THE LAKE LATE FRI NGT AND
STEADILY DIMINISH THE WINDS. WINDS/WAVES WILL FURTHER DIMINISH
SAT/SUN AS HIGH PRESSURE REMAINS OVER THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 10 AM
     WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 3 PM WEDNESDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 291137
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
637 AM CDT WED OCT 29 2014

.DISCUSSION...
315 AM CDT

SHORT TERM...THROUGH WEDNESDAY NIGHT...FOR THE REMAINDER OF THE NIGHT
AND INTO TUESDAY MORNING...THE MAIN FORECAST ISSUE WILL BE
ASSOCIATED WITH WINDS AND CLOUD COVER,

LATEST SATELLITE IMAGERY SHOWS A STRATOCU DECK SPREADING ACROSS NRN
IL...ASSOCIATED WITH A SECONDARY SURGE OF COOLER AIR AROUND THE SWRN
PERIPHERY OF THE DEEP LOW PRESSURE CENTERED NEAR JAMES BAY.  CLEAR
SKIES PREVAILED OVER THE CWA THROUGH MUCH OF THE EVENING ALLOWING
WINDS TO DIMINISH AS RADIATIONAL COOLING ALLOWED A NOCTURNAL
INVERSION TO FORM...DECOUPLING THE LOWER LEVELS FROM STRONGER WINDS
ALOFT.  HOWEVER...AS THE WRAPAROUND CLOUD COVER OVERSPREADS THE
REGION...WINDS WILL PICK UP ONCE AGAIN...AND PER UPSTREAM OBS.
EXPECT THAT THE WEAKER WSWLY WINDS WILL VEER TO MORE WNWLY AND GUST
UP TO ARND 25KT.  THE STRONGER WINDS AND CLOUD COVER SHOULD ONLY
COVER LOCATIONS GENERALLY NORTH OF THE ILLINOIS AND KANKAKEE
RIVERS...PER LATEST MODEL RH GUIDANCE AND TIMING OF THE LEADING EDGE
OF THE CLOUD DECK...SO THE SRN PORTIONS OF THE CWA SHOULD REMAIN
UNDER MOSTLY CLEAR SKIES WITH LIGHTER WINDS.  TEMPERATURES TODAY
SHOULD BE EVEN LOWER THAN YESTERDAY AS THE REGION REMAINS UNDER NWLY
FLOW AT THE SFC AND ALOFT...WITH PERSISTENT COLD ADVECTION.  HIGHS
WEDNESDAY ARE EXPECTED TO ONLY REACH INTO THE UPPER 40S GENERALLY
NORTH OF THE I-88 CORRIDOR WITH LOWER 50S TO THE SOUTH.

HIGH PRESSURE BUILDING OUT OF THE NRN PLAINS IS EXPECTED TO SPREAD
ACROSS THE MISSISSIPPI VALLEY AND INTO THE WRN PORTIONS OF THE CWA
BY EARLY AFTERNOON AND THEN CONTINUE TO SPREAD EAST ACROSS THE
REMAINDER OF THE CWA THROUGH THE AFTERNOON AND INTO THE EVENING.
THIS SHOULD BRING DECREASING CLOUD COVER AS WELL AS DECREASING WINDS
WITH THE DECREASING PRESSURE GRADIENT.  BY EARLY THIS EVENING...
WINDS SHOULD BECM NEAR CALM. THE CLEARING SKIES AND CALM WINDS
SHOULD ALLOW FOR STRONG RADIATIONAL COOLING...AND WITH DEWPOINTS
EXPECTED TO BE IN THE LOWER 30S...TEMPERATURES SHOULD DROP INTO THE
LOWER 30S AS WELL.  EVEN THE CHICAGO URBAN HEAT ISLAND AREA WILL GET
QUITE CHILLY...WITH LOWS IN THE MIDDLE 30S.

KREIN

THURSDAY THROUGH FRIDAY...
WHILE THE WEEK BEGAN ON A VERY MILD NOTE...WITH TEMPERATURES WELL
INTO THE 70S MON...THE WEEK CLOSES OUT AS NEARLY THE INVERSE OF HOW
IT BEGAN. BROAD MID-LVL TROUGHING WILL CONTINUE ACROSS THE BULK OF
THE GREAT LAKES/OHIO VALLEY REGIONS THUR...WITH A SECONDARY
SHORTWAVE POISED TO SWEEP SOUTHEAST ACROSS THE UPPER
MIDWEST/NORTHERN PLAINS EARLY THUR. GUIDANCE HAS CONTINUED TO
SUGGEST WITH THIS FEATURE THAT A WEAK SFC FEATURE WILL DEVELOP NEAR
NORTHEAST KS...WITH WEAK ADVECTION AHEAD OF THIS SYSTEM SOME LGT
PRECIP MAY OVERSPREAD THE FORECAST AREA.

THE SFC LOW THEN DEEPENS ACROSS LOWER MICHIGAN LATE THUR NGT/EARLY
FRI...AS A POTENT CANADIAN HIGH PRESSURE BEGINS TO SLIDE SOUTH INTO
THE NORTHERN PLAINS. THE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS
QUICKLY FRI MORNING...AND WILL PRODUCE BREEZY CONDITIONS WITH GUSTS
UP TO 40 MPH POSSIBLE MIDDAY FRI. ACCOMPANYING THE STRONG CANADIAN
HIGH WILL BE MUCH COLDER AIR...AS TEMPS WILL LIKELY STRUGGLE TO WARM
BEYOND THE LOW TO MID 40S. GUIDANCE CONTINUES TO ADVERTISE A SLUG OF
850MB TEMPS DROPPING TO -6 TO -10 DEG C MIDDAY FRI/EARLY
AFTN...WHICH MAY BE STRONG ENOUGH TO KEEP TEMPS COOLER IN THE UPR
30S/LOW 40S FRI. THE COMBINATION OF GUSTY WINDS AND TEMPS IN THE LOW
40S...WILL LIKELY CREATE WIND CHILL VALUES AROUND 30-33 DEGREES FRI
AFTN. PRECIP AT THIS TIME SHUD REMAIN IN LIQUID FORM FRI...HOWEVER
AS COLDER AIR ADVECTS IN FROM THE NORTH/NORTHWEST FRI LATE
AFTN/EARLY EVE...WE SHOULD BEGIN TO SEE A MIX OF RAIN/SNOW. LAKE
EFFECT PRECIP LOOKS FAVORABLE AS WELL...HOWEVER GIVEN THE STRONG
WINDS AND REDUCED RESONANCE TIME...THE ONSET WILL LIKELY START
CELLULAR. THEN AS WINDS DIMINISH LATE FRI NGT A FEW BANDS MAY TRY TO
DEVELOP OVER NORTHWEST IND. TEMPS WILL COOL ENOUGH OVERNIGHT TO
CHANGE ALL PRECIP OVER TO SNOW...BUT NOT EXPECTING ANY ACCUMULATIONS
AT THIS TIME. TEMPS FRI NIGHT OVER LAND WILL LIKELY DIP INTO THE
MID/UPR 20S ACROSS THE WESTERN HALF OF THE LAKE WHERE SKIES SHUD
ERODE EARLIER FRI NGT. FURTHER EAST LAKE EFFECT CLOUDS WILL HELP TO
KEEP TEMPS SLIGHTLY WARMER.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
THE WEEKEND WILL START UNSEASONABLY COLD WITH A DEEP 500MB TROUGH
OVER THE EASTERN HALF OF THE CONUS...AND A HIGH AMPLITUDE RIDGE
STRETCHING NORTH THROUGH THE PLAINS INTO GREENLAND. BY THE SECOND
HALF OF THE WEEKEND THE TROUGH BEGINS TO WEAKEN. SFC RIDGE OVER THE
GREAT LAKES SAT WILL SHIFT EAST SUN. GUIDANCE HAS SLOWED THE
DEPARTURE OF THE SFC RIDGE SLIGHTLY...WHICH WILL RESULT IN HOW
QUICKLY THE SECONDARY TROUGH CAN PUSH INTO THE FOUR-CORNERS REGION.
CURRENT THINKING IS THAT A TROUGH WILL PUSH INTO THE SOUTHWEST CONUS
LATE SUN/EARLY MON...WITH A SFC LOW DEVELOPING EARLY NEXT WEEK
ACROSS THE ROCKIES. THIS WILL LIKELY SET THE STAGE FOR A SLOW
MODERATION IN TEMPS EARLY NEXT WEEK ALONG WITH PRECIP CHANCES
INCREASING MON.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS THROUGH EARLY AFTERNOON.

KREIN

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

AS THE DEEP LOW PRESSURE SYSTEM CONTINUES TO TRACK NEWD THROUGH
CANADA...A SECONDARY SURGE OF COOLER AIR AND A BKN-OVC STRATOCU
DECK HAS OVERSPREAD THE REGION. THE SECONDARY SURGE OF COOLER AIR
AND INCREASED COLD ADVECTION WILL BRING GUSTS TO ARND 25KT. HIGH
PRESSURE WILL BUILD ACROSS THE PLAINS AND SPREAD EAST OF THE
MISSISSIPPI RIVER THROUGH THE AFTERNOON...LEADING TO CLEARING
SKIES AND DIMINISHING WINDS. DURG THE EARLY EVENING HOURS...THE
HIGH WILL BE RIGHT ON TOP OF THE AREA...AND WINDS SHOULD BECOME
LGT/VRBL UNDER CLEAR SKIES... WHICH SHOULD THEN BE THE PREVAILING
CONDITION THROUGH THE REMAINDER OF THE FORECAST PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

* THURSDAY NIGHT...SLIGHT CHANCE OF SHRA LATE. STRONG NWLY WINDS
  DEVELOPING LATE.

* FRIDAY...SLIGHT CHANCE OF SHRA EARLY SLIGHT CHANCE SHRA/SHSN MIX
  LATE. STRONG/GUSTY NORTH WINDS.

* SATURDAY...VFR. WX NIL. NORTHEAST WINDS.

* SUNDAY....VFR. WX NIL. SOUTH WINDS.

* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

* TUESDAY...CHANCE OF SHRA. SOUTHWEST WINDS.

KREIN

&&

.MARINE...
230 AM CDT

DEEPENING LOW OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST AWAY
FROM THE GREAT LAKES...AS HIGH PRESSURE SLOWLY SLIDES SOUTHEAST FROM
THE NORTHERN PLAINS INTO THE MID-MISSOURI VALLEY. THIS HIGH PRESSURE
WILL DIMINISH WINDS ACROSS LAKE MICHIGAN TONIGHT/THUR MORNING. THEN
A WEAK LOW WILL DEVELOP ACROSS THE CENTRAL PLAINS EARLY THUR AND
QUICKLY SLIDE EAST TOWARDS LAKE MICHIGAN...BEFORE DEEPENING TO A
STRONGER LOW PRESSURE OVER LOWER MICHIGAN THUR NGT/EARLY FRI.

THEN THE TIME PERIOD OF GREATEST CONCERN WILL BE FRI WITH A VERY
POTENT CANADIAN HIGH PRESSURE REGION POISED TO SLIDE SOUTH INTO THE
NORTHERN PLAINS FRI MORNING. THE GRADIENT BETWEEN THE LOW/HIGH
CONTINUES TO BE SUPPORTIVE OF GENERATING GALES TO 40KT AND POSSIBLY
45KT AROUND 9Z FRI MORNING ACROSS THE NORTHERN HALF OF THE
LAKE...AND LIKELY DEVELOP FURTHER SOUTH AROUND DAYBREAK FRI OR
SHORTLY AFTER DAYBREAK FRI.

GUIDANCE HAS REMAINED CONSISTENT WITH HIGH CONFIDENCE IN NORTH GALES
40-45KTS DEVELOPING FRI...SO HAVE OPTED TO JUST JUMP TO A GALE
WARNING RATHER THAN A WATCH. THERE IS A SMALL WINDOW MIDDAY FRI
WHERE A FEW STORM FORCE GUSTS COULD OCCUR...BUT THIS IS A LOW
CONFIDENCE FOR ANY DURATION OF STORM FORCE WINDS. WITH THE NORTH
GALES...AND FOR A DECENT DURATION...IT IS POSSIBLE THAT WAVES COULD
BE SUBSTANTIAL ENOUGH TO PRODUCE THE NEED FOR BEACH HAZARDS ALONG
THE INDIANA SHORELINE FRI AS WELL.

HIGH PRESSURE WILL THEN BUILD ACROSS THE LAKE LATE FRI NGT AND
STEADILY DIMINISH THE WINDS. WINDS/WAVES WILL FURTHER DIMINISH
SAT/SUN AS HIGH PRESSURE REMAINS OVER THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 290902
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
402 AM CDT WED OCT 29 2014

.DISCUSSION...
315 AM CDT

SHORT TERM...THROUGH WEDNESDAY NIGHT...FOR THE REMAINDER OF THE NIGHT
AND INTO TUESDAY MORNING...THE MAIN FORECAST ISSUE WILL BE
ASSOCIATED WITH WINDS AND CLOUD COVER,

LATEST SATELLITE IMAGERY SHOWS A STRATOCU DECK SPREADING ACROSS NRN
IL...ASSOCIATED WITH A SECONDARY SURGE OF COOLER AIR AROUND THE SWRN
PERIPHERY OF THE DEEP LOW PRESSURE CENTERED NEAR JAMES BAY.  CLEAR
SKIES PREVAILED OVER THE CWA THROUGH MUCH OF THE EVENING ALLOWING
WINDS TO DIMINISH AS RADIATIONAL COOLING ALLOWED A NOCTURNAL
INVERSION TO FORM...DECOUPLING THE LOWER LEVELS FROM STRONGER WINDS
ALOFT.  HOWEVER...AS THE WRAPAROUND CLOUD COVER OVERSPREADS THE
REGION...WINDS WILL PICK UP ONCE AGAIN...AND PER UPSTREAM OBS.
EXPECT THAT THE WEAKER WSWLY WINDS WILL VEER TO MORE WNWLY AND GUST
UP TO ARND 25KT.  THE STRONGER WINDS AND CLOUD COVER SHOULD ONLY
COVER LOCATIONS GENERALLY NORTH OF THE ILLINOIS AND KANKAKEE
RIVERS...PER LATEST MODEL RH GUIDANCE AND TIMING OF THE LEADING EDGE
OF THE CLOUD DECK...SO THE SRN PORTIONS OF THE CWA SHOULD REMAIN
UNDER MOSTLY CLEAR SKIES WITH LIGHTER WINDS.  TEMPERATURES TODAY
SHOULD BE EVEN LOWER THAN YESTERDAY AS THE REGION REMAINS UNDER NWLY
FLOW AT THE SFC AND ALOFT...WITH PERSISTENT COLD ADVECTION.  HIGHS
WEDNESDAY ARE EXPECTED TO ONLY REACH INTO THE UPPER 40S GENERALLY
NORTH OF THE I-88 CORRIDOR WITH LOWER 50S TO THE SOUTH.

HIGH PRESSURE BUILDING OUT OF THE NRN PLAINS IS EXPECTED TO SPREAD
ACROSS THE MISSISSIPPI VALLEY AND INTO THE WRN PORTIONS OF THE CWA
BY EARLY AFTERNOON AND THEN CONTINUE TO SPREAD EAST ACROSS THE
REMAINDER OF THE CWA THROUGH THE AFTERNOON AND INTO THE EVENING.
THIS SHOULD BRING DECREASING CLOUD COVER AS WELL AS DECREASING WINDS
WITH THE DECREASING PRESSURE GRADIENT.  BY EARLY THIS EVENING...
WINDS SHOULD BECM NEAR CALM. THE CLEARING SKIES AND CALM WINDS
SHOULD ALLOW FOR STRONG RADIATIONAL COOLING...AND WITH DEWPOINTS
EXPECTED TO BE IN THE LOWER 30S...TEMPERATURES SHOULD DROP INTO THE
LOWER 30S AS WELL.  EVEN THE CHICAGO URBAN HEAT ISLAND AREA WILL GET
QUITE CHILLY...WITH LOWS IN THE MIDDLE 30S.

KREIN

THURSDAY THROUGH FRIDAY...
WHILE THE WEEK BEGAN ON A VERY MILD NOTE...WITH TEMPERATURES WELL
INTO THE 70S MON...THE WEEK CLOSES OUT AS NEARLY THE INVERSE OF HOW
IT BEGAN. BROAD MID-LVL TROUGHING WILL CONTINUE ACROSS THE BULK OF
THE GREAT LAKES/OHIO VALLEY REGIONS THUR...WITH A SECONDARY
SHORTWAVE POISED TO SWEEP SOUTHEAST ACROSS THE UPPER
MIDWEST/NORTHERN PLAINS EARLY THUR. GUIDANCE HAS CONTINUED TO
SUGGEST WITH THIS FEATURE THAT A WEAK SFC FEATURE WILL DEVELOP NEAR
NORTHEAST KS...WITH WEAK ADVECTION AHEAD OF THIS SYSTEM SOME LGT
PRECIP MAY OVERSPREAD THE FORECAST AREA.

THE SFC LOW THEN DEEPENS ACROSS LOWER MICHIGAN LATE THUR NGT/EARLY
FRI...AS A POTENT CANADIAN HIGH PRESSURE BEGINS TO SLIDE SOUTH INTO
THE NORTHERN PLAINS. THE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS
QUICKLY FRI MORNING...AND WILL PRODUCE BREEZY CONDITIONS WITH GUSTS
UP TO 40 MPH POSSIBLE MIDDAY FRI. ACCOMPANYING THE STRONG CANADIAN
HIGH WILL BE MUCH COLDER AIR...AS TEMPS WILL LIKELY STRUGGLE TO WARM
BEYOND THE LOW TO MID 40S. GUIDANCE CONTINUES TO ADVERTISE A SLUG OF
850MB TEMPS DROPPING TO -6 TO -10 DEG C MIDDAY FRI/EARLY
AFTN...WHICH MAY BE STRONG ENOUGH TO KEEP TEMPS COOLER IN THE UPR
30S/LOW 40S FRI. THE COMBINATION OF GUSTY WINDS AND TEMPS IN THE LOW
40S...WILL LIKELY CREATE WIND CHILL VALUES AROUND 30-33 DEGREES FRI
AFTN. PRECIP AT THIS TIME SHUD REMAIN IN LIQUID FORM FRI...HOWEVER
AS COLDER AIR ADVECTS IN FROM THE NORTH/NORTHWEST FRI LATE
AFTN/EARLY EVE...WE SHOULD BEGIN TO SEE A MIX OF RAIN/SNOW. LAKE
EFFECT PRECIP LOOKS FAVORABLE AS WELL...HOWEVER GIVEN THE STRONG
WINDS AND REDUCED RESONANCE TIME...THE ONSET WILL LIKELY START
CELLULAR. THEN AS WINDS DIMINISH LATE FRI NGT A FEW BANDS MAY TRY TO
DEVELOP OVER NORTHWEST IND. TEMPS WILL COOL ENOUGH OVERNIGHT TO
CHANGE ALL PRECIP OVER TO SNOW...BUT NOT EXPECTING ANY ACCUMULATIONS
AT THIS TIME. TEMPS FRI NIGHT OVER LAND WILL LIKELY DIP INTO THE
MID/UPR 20S ACROSS THE WESTERN HALF OF THE LAKE WHERE SKIES SHUD
ERODE EARLIER FRI NGT. FURTHER EAST LAKE EFFECT CLOUDS WILL HELP TO
KEEP TEMPS SLIGHTLY WARMER.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
THE WEEKEND WILL START UNSEASONABLY COLD WITH A DEEP 500MB TROUGH
OVER THE EASTERN HALF OF THE CONUS...AND A HIGH AMPLITUDE RIDGE
STRETCHING NORTH THROUGH THE PLAINS INTO GREENLAND. BY THE SECOND
HALF OF THE WEEKEND THE TROUGH BEGINS TO WEAKEN. SFC RIDGE OVER THE
GREAT LAKES SAT WILL SHIFT EAST SUN. GUIDANCE HAS SLOWED THE
DEPARTURE OF THE SFC RIDGE SLIGHTLY...WHICH WILL RESULT IN HOW
QUICKLY THE SECONDARY TROUGH CAN PUSH INTO THE FOUR-CORNERS REGION.
CURRENT THINKING IS THAT A TROUGH WILL PUSH INTO THE SOUTHWEST CONUS
LATE SUN/EARLY MON...WITH A SFC LOW DEVELOPING EARLY NEXT WEEK
ACROSS THE ROCKIES. THIS WILL LIKELY SET THE STAGE FOR A SLOW
MODERATION IN TEMPS EARLY NEXT WEEK ALONG WITH PRECIP CHANCES
INCREASING MON.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS OVERNIGHT AND WEDNESDAY.

KREIN

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

AS THE DEEP LOW PRESSURE SYSTEM CONTINUES TO TRACK NEWD THROUGH
CANADA...A SECONDARY SURGE OF COOLER AIR AND A BKN-OVC STRATOCU
DECK IS PUSHING INTO NWRN IL. AHEAD OF THE STATOCU DECK...WINDS
HAVE BEEN ABLE TO WEAKEN AS THE LOWER LEVELS BECOME DECOUPLED FROM
STRONGER WINDS ALOFT...BUT UNDER THE CLOUD DECK...WINDS REMAIN
STRONGER AND GUSTY DUE TO THE LACK OF RADIATIONAL COOLING TO FORM
A NOCTURNAL INVERSION. SO...AS THE CLOUD DECK MOVES OVER THE
TERMINALS...EXPECT THAT WINDS WILL INCREASE AGAIN...WITH GUSTS TO
ARND 25KT FOR THE REMAINDER OF THE NIGHT AND INTO WEDNESDAY
MORNING. THROUGH THE DAY ON WEDNESDAY...HIGH PRESSURE WILL BUILD
ACROSS THE PLAINS AND SPREAD EAST OF THE MISSISSIPPI RIVER THROUGH
THE AFTERNOON...LEADING TO CLEARING SKIES AND DIMINISHING WINDS.
DURG THE EARLY EVENING HOURS...THE HIGH WILL BE RIGHT ON TOP OF
THE AREA...AND WINDS SHOULD BECOME LGT/VRBL UNDER CLEAR SKIES...
WHICH SHOULD THEN BE THE PREVAILING CONDITION THROUGH THE
REMAINDER OF THE FORECAST PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

* THURSDAY...SLIGHT CHANCE OF SHRA. LIGHT WEST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA. STRONG/GUSTY NORTH WINDS.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF SHRA. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

&&

.MARINE...
230 AM CDT

DEEPENING LOW OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST AWAY
FROM THE GREAT LAKES...AS HIGH PRESSURE SLOWLY SLIDES SOUTHEAST FROM
THE NORTHERN PLAINS INTO THE MID-MISSOURI VALLEY. THIS HIGH PRESSURE
WILL DIMINISH WINDS ACROSS LAKE MICHIGAN TONIGHT/THUR MORNING. THEN
A WEAK LOW WILL DEVELOP ACROSS THE CENTRAL PLAINS EARLY THUR AND
QUICKLY SLIDE EAST TOWARDS LAKE MICHIGAN...BEFORE DEEPENING TO A
STRONGER LOW PRESSURE OVER LOWER MICHIGAN THUR NGT/EARLY FRI.

THEN THE TIME PERIOD OF GREATEST CONCERN WILL BE FRI WITH A VERY
POTENT CANADIAN HIGH PRESSURE REGION POISED TO SLIDE SOUTH INTO THE
NORTHERN PLAINS FRI MORNING. THE GRADIENT BETWEEN THE LOW/HIGH
CONTINUES TO BE SUPPORTIVE OF GENERATING GALES TO 40KT AND POSSIBLY
45KT AROUND 9Z FRI MORNING ACROSS THE NORTHERN HALF OF THE
LAKE...AND LIKELY DEVELOP FURTHER SOUTH AROUND DAYBREAK FRI OR
SHORTLY AFTER DAYBREAK FRI.

GUIDANCE HAS REMAINED CONSISTENT WITH HIGH CONFIDENCE IN NORTH GALES
40-45KTS DEVELOPING FRI...SO HAVE OPTED TO JUST JUMP TO A GALE
WARNING RATHER THAN A WATCH. THERE IS A SMALL WINDOW MIDDAY FRI
WHERE A FEW STORM FORCE GUSTS COULD OCCUR...BUT THIS IS A LOW
CONFIDENCE FOR ANY DURATION OF STORM FORCE WINDS. WITH THE NORTH
GALES...AND FOR A DECENT DURATION...IT IS POSSIBLE THAT WAVES COULD
BE SUBSTANTIAL ENOUGH TO PRODUCE THE NEED FOR BEACH HAZARDS ALONG
THE INDIANA SHORELINE FRI AS WELL.

HIGH PRESSURE WILL THEN BUILD ACROSS THE LAKE LATE FRI NGT AND
STEADILY DIMINISH THE WINDS. WINDS/WAVES WILL FURTHER DIMINISH
SAT/SUN AS HIGH PRESSURE REMAINS OVER THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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
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000
FXUS63 KLOT 290817
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
317 AM CDT WED OCT 29 2014

.DISCUSSION...
315 AM CDT

SHORT TERM...THROUGH WEDNESDAY NIGHT...FOR THE REMAINDER OF THE NIGHT
AND INTO TUESDAY MORNING...THE MAIN FORECAST ISSUE WILL BE
ASSOCIATED WITH WINDS AND CLOUD COVER,

LATEST SATELLITE IMAGERY SHOWS A STRATOCU DECK SPREADING ACROSS NRN
IL...ASSOCIATED WITH A SECONDARY SURGE OF COOLER AIR AROUND THE SWRN
PERIPHERY OF THE DEEP LOW PRESSURE CENTERED NEAR JAMES BAY.  CLEAR
SKIES PREVAILED OVER THE CWA THROUGH MUCH OF THE EVENING ALLOWING
WINDS TO DIMINISH AS RADIATIONAL COOLING ALLOWED A NOCTURNAL
INVERSION TO FORM...DECOUPLING THE LOWER LEVELS FROM STRONGER WINDS
ALOFT.  HOWEVER...AS THE WRAPAROUND CLOUD COVER OVERSPREADS THE
REGION...WINDS WILL PICK UP ONCE AGAIN...AND PER UPSTREAM OBS.
EXPECT THAT THE WEAKER WSWLY WINDS WILL VEER TO MORE WNWLY AND GUST
UP TO ARND 25KT.  THE STRONGER WINDS AND CLOUD COVER SHOULD ONLY
COVER LOCATIONS GENERALLY NORTH OF THE ILLINOIS AND KANKAKEE
RIVERS...PER LATEST MODEL RH GUIDANCE AND TIMING OF THE LEADING EDGE
OF THE CLOUD DECK...SO THE SRN PORTIONS OF THE CWA SHOULD REMAIN
UNDER MOSTLY CLEAR SKIES WITH LIGHTER WINDS.  TEMPERATURES TODAY
SHOULD BE EVEN LOWER THAN YESTERDAY AS THE REGION REMAINS UNDER NWLY
FLOW AT THE SFC AND ALOFT...WITH PERSISTENT COLD ADVECTION.  HIGHS
WEDNESDAY ARE EXPECTED TO ONLY REACH INTO THE UPPER 40S GENERALLY
NORTH OF THE I-88 CORRIDOR WITH LOWER 50S TO THE SOUTH.

HIGH PRESSURE BUILDING OUT OF THE NRN PLAINS IS EXPECTED TO SPREAD
ACROSS THE MISSISSIPPI VALLEY AND INTO THE WRN PORTIONS OF THE CWA
BY EARLY AFTERNOON AND THEN CONTINUE TO SPREAD EAST ACROSS THE
REMAINDER OF THE CWA THROUGH THE AFTERNOON AND INTO THE EVENING.
THIS SHOULD BRING DECREASING CLOUD COVER AS WELL AS DECREASING WINDS
WITH THE DECREASING PRESSURE GRADIENT.  BY EARLY THIS EVENING...
WINDS SHOULD BECM NEAR CALM. THE CLEARING SKIES AND CALM WINDS
SHOULD ALLOW FOR STRONG RADIATIONAL COOLING...AND WITH DEWPOINTS
EXPECTED TO BE IN THE LOWER 30S...TEMPERATURES SHOULD DROP INTO THE
LOWER 30S AS WELL.  EVEN THE CHICAGO URBAN HEAT ISLAND AREA WILL GET
QUITE CHILLY...WITH LOWS IN THE MIDDLE 30S.

KREIN

THURSDAY THROUGH FRIDAY...
WHILE THE WEEK BEGAN ON A VERY MILD NOTE...WITH TEMPERATURES WELL
INTO THE 70S MON...THE WEEK CLOSES OUT AS NEARLY THE INVERSE OF HOW
IT BEGAN. BROAD MID-LVL TROUGHING WILL CONTINUE ACROSS THE BULK OF
THE GREAT LAKES/OHIO VALLEY REGIONS THUR...WITH A SECONDARY
SHORTWAVE POISED TO SWEEP SOUTHEAST ACROSS THE UPPER
MIDWEST/NORTHERN PLAINS EARLY THUR. GUIDANCE HAS CONTINUED TO
SUGGEST WITH THIS FEATURE THAT A WEAK SFC FEATURE WILL DEVELOP NEAR
NORTHEAST KS...WITH WEAK ADVECTION AHEAD OF THIS SYSTEM SOME LGT
PRECIP MAY OVERSPREAD THE FORECAST AREA.

THE SFC LOW THEN DEEPENS ACROSS LOWER MICHIGAN LATE THUR NGT/EARLY
FRI...AS A POTENT CANADIAN HIGH PRESSURE BEGINS TO SLIDE SOUTH INTO
THE NORTHERN PLAINS. THE GRADIENT BETWEEN THE TWO SYSTEMS TIGHTENS
QUICKLY FRI MORNING...AND WILL PRODUCE BREEZY CONDITIONS WITH GUSTS
UP TO 40 MPH POSSIBLE MIDDAY FRI. ACCOMPANYING THE STRONG CANADIAN
HIGH WILL BE MUCH COLDER AIR...AS TEMPS WILL LIKELY STRUGGLE TO WARM
BEYOND THE LOW TO MID 40S. GUIDANCE CONTINUES TO ADVERTISE A SLUG OF
850MB TEMPS DROPPING TO -6 TO -10 DEG C MIDDAY FRI/EARLY
AFTN...WHICH MAY BE STRONG ENOUGH TO KEEP TEMPS COOLER IN THE UPR
30S/LOW 40S FRI. THE COMBINATION OF GUSTY WINDS AND TEMPS IN THE LOW
40S...WILL LIKELY CREATE WIND CHILL VALUES AROUND 30-33 DEGREES FRI
AFTN. PRECIP AT THIS TIME SHUD REMAIN IN LIQUID FORM FRI...HOWEVER
AS COLDER AIR ADVECTS IN FROM THE NORTH/NORTHWEST FRI LATE
AFTN/EARLY EVE...WE SHOULD BEGIN TO SEE A MIX OF RAIN/SNOW. LAKE
EFFECT PRECIP LOOKS FAVORABLE AS WELL...HOWEVER GIVEN THE STRONG
WINDS AND REDUCED RESONANCE TIME...THE ONSET WILL LIKELY START
CELLULAR. THEN AS WINDS DIMINISH LATE FRI NGT A FEW BANDS MAY TRY TO
DEVELOP OVER NORTHWEST IND. TEMPS WILL COOL ENOUGH OVERNIGHT TO
CHANGE ALL PRECIP OVER TO SNOW...BUT NOT EXPECTING ANY ACCUMULATIONS
AT THIS TIME. TEMPS FRI NIGHT OVER LAND WILL LIKELY DIP INTO THE
MID/UPR 20S ACROSS THE WESTERN HALF OF THE LAKE WHERE SKIES SHUD
ERODE EARLIER FRI NGT. FURTHER EAST LAKE EFFECT CLOUDS WILL HELP TO
KEEP TEMPS SLIGHTLY WARMER.

CONFIDENCE...HIGH.

SATURDAY THROUGH EARLY NEXT WEEK...
THE WEEKEND WILL START UNSEASONABLY COLD WITH A DEEP 500MB TROUGH
OVER THE EASTERN HALF OF THE CONUS...AND A HIGH AMPLITUDE RIDGE
STRETCHING NORTH THROUGH THE PLAINS INTO GREENLAND. BY THE SECOND
HALF OF THE WEEKEND THE TROUGH BEGINS TO WEAKEN. SFC RIDGE OVER THE
GREAT LAKES SAT WILL SHIFT EAST SUN. GUIDANCE HAS SLOWED THE
DEPARTURE OF THE SFC RIDGE SLIGHTLY...WHICH WILL RESULT IN HOW
QUICKLY THE SECONDARY TROUGH CAN PUSH INTO THE FOUR-CORNERS REGION.
CURRENT THINKING IS THAT A TROUGH WILL PUSH INTO THE SOUTHWEST CONUS
LATE SUN/EARLY MON...WITH A SFC LOW DEVELOPING EARLY NEXT WEEK
ACROSS THE ROCKIES. THIS WILL LIKELY SET THE STAGE FOR A SLOW
MODERATION IN TEMPS EARLY NEXT WEEK ALONG WITH PRECIP CHANCES
INCREASING MON.

CONFIDENCE...HIGH.

BEACHLER

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS OVERNIGHT AND WEDNESDAY.

KREIN

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

AS THE DEEP LOW PRESSURE SYSTEM CONTINUES TO TRACK NEWD THROUGH
CANADA...A SECONDARY SURGE OF COOLER AIR AND A BKN-OVC STRATOCU
DECK IS PUSHING INTO NWRN IL. AHEAD OF THE STATOCU DECK...WINDS
HAVE BEEN ABLE TO WEAKEN AS THE LOWER LEVELS BECOME DECOUPLED FROM
STRONGER WINDS ALOFT...BUT UNDER THE CLOUD DECK...WINDS REMAIN
STRONGER AND GUSTY DUE TO THE LACK OF RADIATIONAL COOLING TO FORM
A NOCTURNAL INVERSION. SO...AS THE CLOUD DECK MOVES OVER THE
TERMINALS...EXPECT THAT WINDS WILL INCREASE AGAIN...WITH GUSTS TO
ARND 25KT FOR THE REMAINDER OF THE NIGHT AND INTO WEDNESDAY
MORNING. THROUGH THE DAY ON WEDNESDAY...HIGH PRESSURE WILL BUILD
ACROSS THE PLAINS AND SPREAD EAST OF THE MISSISSIPPI RIVER THROUGH
THE AFTERNOON...LEADING TO CLEARING SKIES AND DIMINISHING WINDS.
DURG THE EARLY EVENING HOURS...THE HIGH WILL BE RIGHT ON TOP OF
THE AREA...AND WINDS SHOULD BECOME LGT/VRBL UNDER CLEAR SKIES...
WHICH SHOULD THEN BE THE PREVAILING CONDITION THROUGH THE
REMAINDER OF THE FORECAST PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

* THURSDAY...SLIGHT CHANCE OF SHRA. LIGHT WEST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA. STRONG/GUSTY NORTH WINDS.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF SHRA. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

&&

.MARINE...
230 AM CDT

DEEPENING LOW OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST AWAY
FROM THE GREAT LAKES...AS HIGH PRESSURE SLOWLY SLIDES SOUTHEAST FROM
THE NORTHERN PLAINS INTO THE MID-MISSOURI VALLEY. THIS HIGH PRESSURE
WILL DIMINISH WINDS ACROSS LAKE MICHIGAN TONIGHT/THUR MORNING. THEN
A WEAK LOW WILL DEVELOP ACROSS THE CENTRAL PLAINS EARLY THUR AND
QUICKLY SLIDE EAST TOWARDS LAKE MICHIGAN...BEFORE DEEPENING TO A
STRONGER LOW PRESSURE OVER LOWER MICHIGAN THUR NGT/EARLY FRI.

THEN THE TIME PERIOD OF GREATEST CONCERN WILL BE FRI WITH A VERY
POTENT CANADIAN HIGH PRESSURE REGION POISED TO SLIDE SOUTH INTO THE
NORTHERN PLAINS FRI MORNING. THE GRADIENT BETWEEN THE LOW/HIGH
CONTINUES TO BE SUPPORTIVE OF GENERATING GALES TO 40KT AND POSSIBLY
45KT AROUND 9Z FRI MORNING ACROSS THE NORTHERN HALF OF THE
LAKE...AND LIKELY DEVELOP FURTHER SOUTH AROUND DAYBREAK FRI OR
SHORTLY AFTER DAYBREAK FRI.

GUIDANCE HAS REMAINED CONSISTENT WITH HIGH CONFIDENCE IN NORTH GALES
40-45KTS DEVELOPING FRI...SO HAVE OPTED TO JUST JUMP TO A GALE
WARNING RATHER THAN A WATCH. THERE IS A SMALL WINDOW MIDDAY FRI
WHERE A FEW STORM FORCE GUSTS COULD OCCUR...BUT THIS IS A LOW
CONFIDENCE FOR ANY DURATION OF STORM FORCE WINDS. WITH THE NORTH
GALES...AND FOR A DECENT DURATION...IT IS POSSIBLE THAT WAVES COULD
BE SUBSTANTIAL ENOUGH TO PRODUCE THE NEED FOR BEACH HAZARDS ALONG
THE INDIANA SHORELINE FRI AS WELL.

HIGH PRESSURE WILL THEN BUILD ACROSS THE LAKE LATE FRI NGT AND
STEADILY DIMINISH THE WINDS. WINDS/WAVES WILL FURTHER DIMINISH
SAT/SUN AS HIGH PRESSURE REMAINS OVER THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 290730
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
230 AM CDT WED OCT 29 2014

.DISCUSSION...
850 PM CDT

FOR EVENING UPDATE...

ONLY MINOR CHANGE MADE TO GOING FORECAST THIS EVENING WAS TO SLOW
THE CLEARING OF CLOUD COVER ACROSS THE FORECAST AREA OVERNIGHT.

SUB-995 MB SFC LOW LIFTING SLOWLY AWAY TO THE NORTHEAST ACROSS
ONTARIO THIS EVENING...WITH CYCLONIC WEST-NORTHWEST LOW LEVEL FLOW
IN ITS WAKE ACROSS THE UPPER MIDWEST. SOME DECREASE IN CLOUD COVER
HAS TEMPORARILY OCCURRED ACROSS PORTIONS OF NORTHERN IL EARLY THIS
EVENING...THOUGH GOES WATER VAPOR IMAGERY SHOWS ANOTHER STRONG VORT
DIGGING SOUTHEAST ACROSS THE UPPER MISSISSIPPI VALLEY...WITH A
FAIRLY SOLID AREA OF CLOUD COVER AND EVEN A FEW SPRINKLES NOTED OVER
PARTS OF SOUTHEAST MINNESOTA AND FAR WESTERN WISCONSIN. WITH
APPROACHING VORT AND EXTENSIVE UPSTREAM CLOUD COVER IN CONTINUED LOW
LEVEL COLD ADVECTION REGIME...WOULD EXPECT THAT CURRENT DEVELOPING
HOLES IN CLOUDS WOULD FILL IN AS THE NIGHT WEARS ON.

OTHERWISE...TEMP AND WIND TRENDS OF GOING FORECAST APPEAR REASONABLE
AND HAVE MADE NO OTHER SIGNIFICANT CHANGES EXCEPT FOR SKY COVER.

RATZER

//PREV DISCUSSION...
300 PM CDT

BELOW NORMAL TEMPS WILL CHARACTERIZE THE REST OF THE WEEK WITH AN
INFLUX OF MUCH COLDER AND WELL BELOW NORMAL AIR ARRIVING
FRIDAY/SATURDAY BEFORE THINGS MODERATE EARLY NEXT WEEK. THE CLOSED
UPPER LOW THAT HELPED PUSH A COLD FRONTAL BOUNDARY ACROSS THE REGION
THIS MORNING IS NOW CENTERED OVER LAKE SUPERIOR AND TRACKING
EASTWARD. RATHER LOW AMPLITUDE UPPER RIDGING IS MOVING EASTWARD
ACROSS THE WESTERN U.S. AND CANADIAN ROCKIES WITH A SERIES OF LARGER
SCALE TROUGHS OFF THE WEST COAST. OF NOTE IS A WAVE EMBEDDED WITHIN
THE FLOW OVER CENTRAL BRITISH COLUMBIA WHICH WILL CROSS THE AREA AND
SET THE STAGE FOR THE BIG COOL DOWN FRIDAY. AT THE SURFACE...BROAD
LOW PRESSURE IS OVER SOUTHERN ONTARIO WITH THE COLD FRONT THAT
PASSED THIS MORNING NOW WELL TO THE EAST.

TONIGHT THROUGH THURSDAY...QUIET WEATHER WILL PREVAIL THROUGH
WEDNESDAY NIGHT. COLD ADVECTION CONTINUES INTO THE AREA THIS
AFTERNOON AND WILL CONTINUE OVERNIGHT. THE PRESSURE GRADIENT WILL
SUPPORT A STEADY THOUGH NOT TERRIBLY STRONG WESTERLY WIND WHICH WILL
KEEP TEMPS FROM BOTTOMING OUT BUT DO EXPECT THEM TO FALL INTO THE
UPPER 30S TO AROUND 40. THE UPPER TROUGH WILL MOVE NORTHEAST INTO
NORTHERN QUEBEC BUT ANOTHER TROUGH AXIS IS EXPECTED TO AMPLIFY AND
SWING ACROSS THE AREA WEDNESDAY. THE BULK OF THE ASCENT AND DEEPER
MOISTURE ASSOCIATED WITH THIS WILL PASS NORTH OF THE AREA SO AM ONLY
EXPECTING SOME INCREASE IN CLOUD COVER ACROSS NORTHERN AREA AND THIS
MAY BE MINIMAL. THE TROUGH WILL INTRODUCE ANOTHER MODEST PUSH OF
COLDER MID LEVEL AIR SO HIGH TEMPERATURES WILL BE COLDER THAN TODAY
WITH READINGS FROM AROUND 50 NORTH TO THE MID 50S FAR SOUTH. WINDS
WILL TURN NORTHWESTERLY BUT BECOME FAIRLY LIGHT LATE IN THE DAY.
THIS WILL SET THE STAGE FOR COLDER TEMPS WEDNESDAY NIGHT WITH 30S
FOR ALL AREAS OUTSIDE THE IMMEDIATE DOWNTOWN AREA. THE WAVE OVER
BRITISH COLUMBIA TODAY WILL MAKE ITS WAY SOUTHEAST ACROSS THE
NORTHERN PLAINS AND ACROSS THE AREA THURSDAY. GUIDANCE CONTINUES TO
BE MIXED WITH REGARD TO PRECIP POTENTIAL THURSDAY BUT A FAIRLY DRY
ATMOSPHERE WILL BE IN PLACE SO DRY CONDITIONS COULD PREVAIL. WILL GO
AHEAD AND CARRY A SLIGHT CHANCE MENTION FOR MOST AREAS FOR NOW. THE
WAVE WILL BRING A PUSH OF WARMER MID LEVEL AIR AHEAD OF IT SO HIGHS
WILL MODERATE INTO THE LOW TO MID 50S.

FRIDAY AND SATURDAY...GUIDANCE CONTINUES TO BE RATHER CONSISTENT ON
A STRONG UPPER TROUGH DIGGING STRAIGHT SOUTH FROM NORTHERN CANADA
THURSDAY NIGHT AND FRIDAY. THIS WILL PUSH A RELATIVELY WEAK SURFACE
LOW SOUTHEAST ACROSS THE NORTHERN GREAT LAKES WHICH WILL BE
DEEPENING WITH TIME. A VERY STRONG CANADIAN HIGH BUILDS INTO THE
MID/UPPER MISSISSIPPI RIVER VALLEY AND UPPER GREAT LAKES BEHIND THE
LOW INTO FRIDAY NIGHT. H85 TEMPS ARE STILL FORECAST TO FALL TO
AROUND -8C WITH SOME GUIDANCE TRENDING A LITTLE COLDER. THIS WILL
RESULT IN MUCH COLDER SURFACE AIR SPREADING IN THROUGH THE DAY
FRIDAY WHICH IF TIMING HOLDS WILL LIKELY RESULT IN FALLING TEMPS
THROUGH THE DAY. WHILE IT IS STILL EARLY FOR SPECIFICS DO HAVE A
FEW CONCERNS THAT WILL BEAR WATCHING OVER THE NEXT FEW DAYS GIVEN
THE SYNOPTIC SET UP. FIRST IS PRECIP. THE BULK OF SYNOPTIC PRECIP
APPEARS TO REMAIN TO THE EAST OF THE AREA WITH THE UPPER LOW
CENTER REMAINING JUST TO THE EAST WITH THE DEFORMATION AXIS PRECIP
LOOKING SHORT LIVED...THOUGH ENOUGH COLD AIR COULD ARRIVE ALLOWING
FOR A MIX OF PRECIP TYPES. NEXT IS LAKE EFFECT POTENTIAL. IT WILL
CERTAINLY BE COLD ENOUGH FOR LAKE EFFECT PROCESSES WITH LAKE-H85
DELTA TS OF 18-19 C. ORGANIZATION OF BANDS LOOKS TO BE THE
CHALLENGE WITH WINDS STEADILY COMING AROUND FROM NORTHWEST TO
NORTH WITH SPEEDS POTENTIALLY BEING VERY STRONG THROUGH THE
UNSTABLE LAYER. IN ADDITION...WITH THE STRONG HIGH BUILDING IN
INVERSION HEIGHTS MAY QUICKLY FALL PUTTING AN END TO ANY
MEANINGFUL PRECIP...ESPECIALLY BY THE TIME A DUE NORTH FETCH
FAVORING STRONG CONVERGENCE OVER THE LAKE SETS UP FRIDAY
NIGHT/SATURDAY MORNING. LAKE PRECIP TYPE WILL ALSO BE A CONCERN
AND BE DEPENDENT ON LOW LEVEL TEMPS BUT IF PRECIP CAN OCCUR AFTER
DARK FRIDAY THEN IT COULD BE ALL FROZEN. GIVEN THE TIME RANGE AND
THE POTENTIAL LIMITING FACTORS WILL CARRY LOW CHANCE POPS FOR
AREAS NEAR THE LAKE FAVORED BY A NORTH TO NORTH-NORTHEAST WIND.
ANOTHER CONCERN WILL BE THE POTENTIAL FOR VERY STRONG WIND GUSTS
ALONG THE LAKESHORE...AS WELL AS LARGE WAVES IMPACTING THE
SHORELINE THANKS TO THE LONG FETCH OF NORTH WIND. AGAIN...TOO
EARLY TO PIN DOWN DETAILS BUT THE ABOVE CONCERNS ARE HIGHLIGHTED
GIVEN THE SYNOPTIC EXPECTATIONS. THINGS QUIET DOWN SATURDAY AS THE
HIGH MOVES IN LEAVING HIGHS ONLY IN THE 40S.

SUNDAY INTO EARLY NEXT WEEK...THE SURFACE HIGH SHIFTS EAST SUNDAY
WITH A SHARP UPPER RIDGE BUILDING IN FROM THE WEST BRINGING A PUSH
OF WARMER AIR. A LARGE TROUGH WILL BE OVER THE WEST AND GUIDANCE
CONTINUES TO SHOW THIS SPLITTING WITH A TROUGH TRACKING NORTHEAST
ACROSS THE NORTHERN HIGH PLAINS AND INTO MANITOBA INTO MONDAY. THIS
WILL PUSH THE UPPER RIDGE EAST BUT THE ATTENDANT SURFACE LOW WILL
BRING A COLD FRONT TO THE AREA SOME TIME MONDAY OR TUESDAY. WITH THE
PARENT LOW SO FAR TO THE NORTH THE FRONT MAY SLOW AND STALL NEAR THE
AREA. SUNDAY SHOULD SEE HIGHS MODERATE A BIT WITH HIGHS INTO THE 50S
MONDAY. PRECIP TIMING WILL BE DICTATED BY THE TIMING OF THE EXPECTED
FRONT.

MDB

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS OVERNIGHT AND WEDNESDAY.

KREIN

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

AS THE DEEP LOW PRESSURE SYSTEM CONTINUES TO TRACK NEWD THROUGH
CANADA...A SECONDARY SURGE OF COOLER AIR AND A BKN-OVC STRATOCU
DECK IS PUSHING INTO NWRN IL. AHEAD OF THE STATOCU DECK...WINDS
HAVE BEEN ABLE TO WEAKEN AS THE LOWER LEVELS BECOME DECOUPLED FROM
STRONGER WINDS ALOFT...BUT UNDER THE CLOUD DECK...WINDS REMAIN
STRONGER AND GUSTY DUE TO THE LACK OF RADIATIONAL COOLING TO FORM
A NOCTURNAL INVERSION. SO...AS THE CLOUD DECK MOVES OVER THE
TERMINALS...EXPECT THAT WINDS WILL INCREASE AGAIN...WITH GUSTS TO
ARND 25KT FOR THE REMAINDER OF THE NIGHT AND INTO WEDNESDAY
MORNING. THROUGH THE DAY ON WEDNESDAY...HIGH PRESSURE WILL BUILD
ACROSS THE PLAINS AND SPREAD EAST OF THE MISSISSIPPI RIVER THROUGH
THE AFTERNOON...LEADING TO CLEARING SKIES AND DIMINISHING WINDS.
DURG THE EARLY EVENING HOURS...THE HIGH WILL BE RIGHT ON TOP OF
THE AREA...AND WINDS SHOULD BECOME LGT/VRBL UNDER CLEAR SKIES...
WHICH SHOULD THEN BE THE PREVAILING CONDITION THROUGH THE
REMAINDER OF THE FORECAST PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

* THURSDAY...SLIGHT CHANCE OF SHRA. LIGHT WEST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA. STRONG/GUSTY NORTH WINDS.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF SHRA. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

&&

.MARINE...
230 AM CDT

DEEPENING LOW OVER JAMES BAY WILL CONTINUE TO LIFT NORTHEAST AWAY
FROM THE GREAT LAKES...AS HIGH PRESSURE SLOWLY SLIDES SOUTHEAST FROM
THE NORTHERN PLAINS INTO THE MID-MISSOURI VALLEY. THIS HIGH PRESSURE
WILL DIMINISH WINDS ACROSS LAKE MICHIGAN TONIGHT/THUR MORNING. THEN
A WEAK LOW WILL DEVELOP ACROSS THE CENTRAL PLAINS EARLY THUR AND
QUICKLY SLIDE EAST TOWARDS LAKE MICHIGAN...BEFORE DEEPENING TO A
STRONGER LOW PRESSURE OVER LOWER MICHIGAN THUR NGT/EARLY FRI.

THEN THE TIME PERIOD OF GREATEST CONCERN WILL BE FRI WITH A VERY
POTENT CANADIAN HIGH PRESSURE REGION POISED TO SLIDE SOUTH INTO THE
NORTHERN PLAINS FRI MORNING. THE GRADIENT BETWEEN THE LOW/HIGH
CONTINUES TO BE SUPPORTIVE OF GENERATING GALES TO 40KT AND POSSIBLY
45KT AROUND 9Z FRI MORNING ACROSS THE NORTHERN HALF OF THE
LAKE...AND LIKELY DEVELOP FURTHER SOUTH AROUND DAYBREAK FRI OR
SHORTLY AFTER DAYBREAK FRI.

GUIDANCE HAS REMAINED CONSISTENT WITH HIGH CONFIDENCE IN NORTH GALES
40-45KTS DEVELOPING FRI...SO HAVE OPTED TO JUST JUMP TO A GALE
WARNING RATHER THAN A WATCH. THERE IS A SMALL WINDOW MIDDAY FRI
WHERE A FEW STORM FORCE GUSTS COULD OCCUR...BUT THIS IS A LOW
CONFIDENCE FOR ANY DURATION OF STORM FORCE WINDS. WITH THE NORTH
GALES...AND FOR A DECENT DURATION...IT IS POSSIBLE THAT WAVES COULD
BE SUBSTANTIAL ENOUGH TO PRODUCE THE NEED FOR BEACH HAZARDS ALONG
THE INDIANA SHORELINE FRI AS WELL.

HIGH PRESSURE WILL THEN BUILD ACROSS THE LAKE LATE FRI NGT AND
STEADILY DIMINISH THE WINDS. WINDS/WAVES WILL FURTHER DIMINISH
SAT/SUN AS HIGH PRESSURE REMAINS OVER THE LAKE.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 AM WEDNESDAY.

     GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...7 AM FRIDAY TO 4 AM SATURDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...4 AM FRIDAY TO 10 PM FRIDAY.

&&

$$

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 290622
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
122 AM CDT WED OCT 29 2014

.DISCUSSION...
850 PM CDT

FOR EVENING UPDATE...

ONLY MINOR CHANGE MADE TO GOING FORECAST THIS EVENING WAS TO SLOW
THE CLEARING OF CLOUD COVER ACROSS THE FORECAST AREA OVERNIGHT.

SUB-995 MB SFC LOW LIFTING SLOWLY AWAY TO THE NORTHEAST ACROSS
ONTARIO THIS EVENING...WITH CYCLONIC WEST-NORTHWEST LOW LEVEL FLOW
IN ITS WAKE ACROSS THE UPPER MIDWEST. SOME DECREASE IN CLOUD COVER
HAS TEMPORARILY OCCURRED ACROSS PORTIONS OF NORTHERN IL EARLY THIS
EVENING...THOUGH GOES WATER VAPOR IMAGERY SHOWS ANOTHER STRONG VORT
DIGGING SOUTHEAST ACROSS THE UPPER MISSISSIPPI VALLEY...WITH A
FAIRLY SOLID AREA OF CLOUD COVER AND EVEN A FEW SPRINKLES NOTED OVER
PARTS OF SOUTHEAST MINNESOTA AND FAR WESTERN WISCONSIN. WITH
APPROACHING VORT AND EXTENSIVE UPSTREAM CLOUD COVER IN CONTINUED LOW
LEVEL COLD ADVECTION REGIME...WOULD EXPECT THAT CURRENT DEVELOPING
HOLES IN CLOUDS WOULD FILL IN AS THE NIGHT WEARS ON.

OTHERWISE...TEMP AND WIND TRENDS OF GOING FORECAST APPEAR REASONABLE
AND HAVE MADE NO OTHER SIGNIFICANT CHANGES EXCEPT FOR SKY COVER.

RATZER

//PREV DISCUSSION...
300 PM CDT

BELOW NORMAL TEMPS WILL CHARACTERIZE THE REST OF THE WEEK WITH AN
INFLUX OF MUCH COLDER AND WELL BELOW NORMAL AIR ARRIVING
FRIDAY/SATURDAY BEFORE THINGS MODERATE EARLY NEXT WEEK. THE CLOSED
UPPER LOW THAT HELPED PUSH A COLD FRONTAL BOUNDARY ACROSS THE REGION
THIS MORNING IS NOW CENTERED OVER LAKE SUPERIOR AND TRACKING
EASTWARD. RATHER LOW AMPLITUDE UPPER RIDGING IS MOVING EASTWARD
ACROSS THE WESTERN U.S. AND CANADIAN ROCKIES WITH A SERIES OF LARGER
SCALE TROUGHS OFF THE WEST COAST. OF NOTE IS A WAVE EMBEDDED WITHIN
THE FLOW OVER CENTRAL BRITISH COLUMBIA WHICH WILL CROSS THE AREA AND
SET THE STAGE FOR THE BIG COOL DOWN FRIDAY. AT THE SURFACE...BROAD
LOW PRESSURE IS OVER SOUTHERN ONTARIO WITH THE COLD FRONT THAT
PASSED THIS MORNING NOW WELL TO THE EAST.

TONIGHT THROUGH THURSDAY...QUIET WEATHER WILL PREVAIL THROUGH
WEDNESDAY NIGHT. COLD ADVECTION CONTINUES INTO THE AREA THIS
AFTERNOON AND WILL CONTINUE OVERNIGHT. THE PRESSURE GRADIENT WILL
SUPPORT A STEADY THOUGH NOT TERRIBLY STRONG WESTERLY WIND WHICH WILL
KEEP TEMPS FROM BOTTOMING OUT BUT DO EXPECT THEM TO FALL INTO THE
UPPER 30S TO AROUND 40. THE UPPER TROUGH WILL MOVE NORTHEAST INTO
NORTHERN QUEBEC BUT ANOTHER TROUGH AXIS IS EXPECTED TO AMPLIFY AND
SWING ACROSS THE AREA WEDNESDAY. THE BULK OF THE ASCENT AND DEEPER
MOISTURE ASSOCIATED WITH THIS WILL PASS NORTH OF THE AREA SO AM ONLY
EXPECTING SOME INCREASE IN CLOUD COVER ACROSS NORTHERN AREA AND THIS
MAY BE MINIMAL. THE TROUGH WILL INTRODUCE ANOTHER MODEST PUSH OF
COLDER MID LEVEL AIR SO HIGH TEMPERATURES WILL BE COLDER THAN TODAY
WITH READINGS FROM AROUND 50 NORTH TO THE MID 50S FAR SOUTH. WINDS
WILL TURN NORTHWESTERLY BUT BECOME FAIRLY LIGHT LATE IN THE DAY.
THIS WILL SET THE STAGE FOR COLDER TEMPS WEDNESDAY NIGHT WITH 30S
FOR ALL AREAS OUTSIDE THE IMMEDIATE DOWNTOWN AREA. THE WAVE OVER
BRITISH COLUMBIA TODAY WILL MAKE ITS WAY SOUTHEAST ACROSS THE
NORTHERN PLAINS AND ACROSS THE AREA THURSDAY. GUIDANCE CONTINUES TO
BE MIXED WITH REGARD TO PRECIP POTENTIAL THURSDAY BUT A FAIRLY DRY
ATMOSPHERE WILL BE IN PLACE SO DRY CONDITIONS COULD PREVAIL. WILL GO
AHEAD AND CARRY A SLIGHT CHANCE MENTION FOR MOST AREAS FOR NOW. THE
WAVE WILL BRING A PUSH OF WARMER MID LEVEL AIR AHEAD OF IT SO HIGHS
WILL MODERATE INTO THE LOW TO MID 50S.

FRIDAY AND SATURDAY...GUIDANCE CONTINUES TO BE RATHER CONSISTENT ON
A STRONG UPPER TROUGH DIGGING STRAIGHT SOUTH FROM NORTHERN CANADA
THURSDAY NIGHT AND FRIDAY. THIS WILL PUSH A RELATIVELY WEAK SURFACE
LOW SOUTHEAST ACROSS THE NORTHERN GREAT LAKES WHICH WILL BE
DEEPENING WITH TIME. A VERY STRONG CANADIAN HIGH BUILDS INTO THE
MID/UPPER MISSISSIPPI RIVER VALLEY AND UPPER GREAT LAKES BEHIND THE
LOW INTO FRIDAY NIGHT. H85 TEMPS ARE STILL FORECAST TO FALL TO
AROUND -8C WITH SOME GUIDANCE TRENDING A LITTLE COLDER. THIS WILL
RESULT IN MUCH COLDER SURFACE AIR SPREADING IN THROUGH THE DAY
FRIDAY WHICH IF TIMING HOLDS WILL LIKELY RESULT IN FALLING TEMPS
THROUGH THE DAY. WHILE IT IS STILL EARLY FOR SPECIFICS DO HAVE A
FEW CONCERNS THAT WILL BEAR WATCHING OVER THE NEXT FEW DAYS GIVEN
THE SYNOPTIC SET UP. FIRST IS PRECIP. THE BULK OF SYNOPTIC PRECIP
APPEARS TO REMAIN TO THE EAST OF THE AREA WITH THE UPPER LOW
CENTER REMAINING JUST TO THE EAST WITH THE DEFORMATION AXIS PRECIP
LOOKING SHORT LIVED...THOUGH ENOUGH COLD AIR COULD ARRIVE ALLOWING
FOR A MIX OF PRECIP TYPES. NEXT IS LAKE EFFECT POTENTIAL. IT WILL
CERTAINLY BE COLD ENOUGH FOR LAKE EFFECT PROCESSES WITH LAKE-H85
DELTA TS OF 18-19 C. ORGANIZATION OF BANDS LOOKS TO BE THE
CHALLENGE WITH WINDS STEADILY COMING AROUND FROM NORTHWEST TO
NORTH WITH SPEEDS POTENTIALLY BEING VERY STRONG THROUGH THE
UNSTABLE LAYER. IN ADDITION...WITH THE STRONG HIGH BUILDING IN
INVERSION HEIGHTS MAY QUICKLY FALL PUTTING AN END TO ANY
MEANINGFUL PRECIP...ESPECIALLY BY THE TIME A DUE NORTH FETCH
FAVORING STRONG CONVERGENCE OVER THE LAKE SETS UP FRIDAY
NIGHT/SATURDAY MORNING. LAKE PRECIP TYPE WILL ALSO BE A CONCERN
AND BE DEPENDENT ON LOW LEVEL TEMPS BUT IF PRECIP CAN OCCUR AFTER
DARK FRIDAY THEN IT COULD BE ALL FROZEN. GIVEN THE TIME RANGE AND
THE POTENTIAL LIMITING FACTORS WILL CARRY LOW CHANCE POPS FOR
AREAS NEAR THE LAKE FAVORED BY A NORTH TO NORTH-NORTHEAST WIND.
ANOTHER CONCERN WILL BE THE POTENTIAL FOR VERY STRONG WIND GUSTS
ALONG THE LAKESHORE...AS WELL AS LARGE WAVES IMPACTING THE
SHORELINE THANKS TO THE LONG FETCH OF NORTH WIND. AGAIN...TOO
EARLY TO PIN DOWN DETAILS BUT THE ABOVE CONCERNS ARE HIGHLIGHTED
GIVEN THE SYNOPTIC EXPECTATIONS. THINGS QUIET DOWN SATURDAY AS THE
HIGH MOVES IN LEAVING HIGHS ONLY IN THE 40S.

SUNDAY INTO EARLY NEXT WEEK...THE SURFACE HIGH SHIFTS EAST SUNDAY
WITH A SHARP UPPER RIDGE BUILDING IN FROM THE WEST BRINGING A PUSH
OF WARMER AIR. A LARGE TROUGH WILL BE OVER THE WEST AND GUIDANCE
CONTINUES TO SHOW THIS SPLITTING WITH A TROUGH TRACKING NORTHEAST
ACROSS THE NORTHERN HIGH PLAINS AND INTO MANITOBA INTO MONDAY. THIS
WILL PUSH THE UPPER RIDGE EAST BUT THE ATTENDANT SURFACE LOW WILL
BRING A COLD FRONT TO THE AREA SOME TIME MONDAY OR TUESDAY. WITH THE
PARENT LOW SO FAR TO THE NORTH THE FRONT MAY SLOW AND STALL NEAR THE
AREA. SUNDAY SHOULD SEE HIGHS MODERATE A BIT WITH HIGHS INTO THE 50S
MONDAY. PRECIP TIMING WILL BE DICTATED BY THE TIMING OF THE EXPECTED
FRONT.

MDB

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS OVERNIGHT AND WEDNESDAY.

KREIN

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

AS THE DEEP LOW PRESSURE SYSTEM CONTINUES TO TRACK NEWD THROUGH
CANADA...A SECONDARY SURGE OF COOLER AIR AND A BKN-OVC STRATOCU
DECK IS PUSHING INTO NWRN IL. AHEAD OF THE STATOCU DECK...WINDS
HAVE BEEN ABLE TO WEAKEN AS THE LOWER LEVELS BECOME DECOUPLED FROM
STRONGER WINDS ALOFT...BUT UNDER THE CLOUD DECK...WINDS REMAIN
STRONGER AND GUSTY DUE TO THE LACK OF RADIATIONAL COOLING TO FORM
A NOCTURNAL INVERSION. SO...AS THE CLOUD DECK MOVES OVER THE
TERMINALS...EXPECT THAT WINDS WILL INCREASE AGAIN...WITH GUSTS TO
ARND 25KT FOR THE REMAINDER OF THE NIGHT AND INTO WEDNESDAY
MORNING. THROUGH THE DAY ON WEDNESDAY...HIGH PRESSURE WILL BUILD
ACROSS THE PLAINS AND SPREAD EAST OF THE MISSISSIPPI RIVER THROUGH
THE AFTERNOON...LEADING TO CLEARING SKIES AND DIMINISHING WINDS.
DURG THE EARLY EVENING HOURS...THE HIGH WILL BE RIGHT ON TOP OF
THE AREA...AND WINDS SHOULD BECOME LGT/VRBL UNDER CLEAR SKIES...
WHICH SHOULD THEN BE THE PREVAILING CONDITION THROUGH THE
REMAINDER OF THE FORECAST PERIOD.

KREIN

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

* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS.

KREIN

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

* THURSDAY...SLIGHT CHANCE OF SHRA. LIGHT WEST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA. STRONG/GUSTY NORTH WINDS.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF SHRA. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

&&

.MARINE...
345 PM CDT

DEEPENING LOW PRESSURE CONTINUES TO MOVE NORTHEAST TOWARDS
SOUTHEAST ONTARIO THIS AFTERNOON...WHILE COLDER AIR FILTERS ACROSS
THE LAKE BEHIND THIS SYSTEM. DESPITE THIS LOW MOVING TOWARDS JAMES
BAY TONIGHT...DO EXPECT A FAIRLY TIGHT SURFACE PATTERN TO REMAIN
OVER THE LAKE. WINDS TO 30 KT WILL BE LIKELY ACROSS THE ENTIRE
LAKE TONIGHT...WITH GALE FORCE GUSTS REMAINING A POSSIBILITY AS
WELL. THERE DOES APPEAR TO BE A SMALL WINDOW LATER THIS AFTERNOON
INTO THE EVENING...CONSISTING OF A COUPLE OF HOURS...WHEN MORE
PREVAILING GALES MIGHT BE OBSERVED. THIS DURATION WILL ONCE AGAIN
BE SHORT...AND WITH GUSTS MORE LIKELY TO BE OBSERVED. SO HAVE NOT
ISSUED ANY GALE HEADLINE FOR THIS EVENING...BUT HAVE CONTINUED
GALE FORCE GUST MENTIONING IN THE GLF. WITH THE LOW FURTHER
DEPARTING TO THE NORTHEAST AND HIGH PRESSURE BUILDING NEAR THE
REGION ON WEDNESDAY...DO EXPECT DIMINISHING WINDS ACROSS THE LAKE.
THIS DIMINISHING TREND WILL LIKELY CONTINUE INTO THURSDAY...BEFORE
ATTENTION SHIFTS TOWARDS POSSIBLE STRONG WIND EVENT ON FRIDAY. LOW
PRESSURE WILL MOVE ACROSS THE GREAT LAKES REGION FRIDAY...WHILE
MUCH COLDER AIR AND STRONG HIGH PRESSURE BUILD IN BEHIND IT. THIS
WILL SET THE STAGE FOR POTENTIALLY VERY STRONG NORTHERLY WINDS
OVER THE ENTIRE LAKE. THIS SYSTEM WARRANTS CLOSE MONITORING AS
HIGH END GALES ARE APPEARING A DISTINCT POSSIBILITY...WITH THE
POTENTIAL FOR STORM FORCE WINDS ALSO THERE.

RODRIGUEZ

&&

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

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 10 AM
     WEDNESDAY.

&&

$$

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

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







000
FXUS63 KLOT 290311
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1011 PM CDT TUE OCT 28 2014

.DISCUSSION...
850 PM CDT

FOR EVENING UPDATE...

ONLY MINOR CHANGE MADE TO GOING FORECAST THIS EVENING WAS TO SLOW
THE CLEARING OF CLOUD COVER ACROSS THE FORECAST AREA OVERNIGHT.

SUB-995 MB SFC LOW LIFTING SLOWLY AWAY TO THE NORTHEAST ACROSS
ONTARIO THIS EVENING...WITH CYCLONIC WEST-NORTHWEST LOW LEVEL FLOW
IN ITS WAKE ACROSS THE UPPER MIDWEST. SOME DECREASE IN CLOUD COVER
HAS TEMPORARILY OCCURRED ACROSS PORTIONS OF NORTHERN IL EARLY THIS
EVENING...THOUGH GOES WATER VAPOR IMAGERY SHOWS ANOTHER STRONG VORT
DIGGING SOUTHEAST ACROSS THE UPPER MISSISSIPPI VALLEY...WITH A
FAIRLY SOLID AREA OF CLOUD COVER AND EVEN A FEW SPRINKLES NOTED OVER
PARTS OF SOUTHEAST MINNESOTA AND FAR WESTERN WISCONSIN. WITH
APPROACHING VORT AND EXTENSIVE UPSTREAM CLOUD COVER IN CONTINUED LOW
LEVEL COLD ADVECTION REGIME...WOULD EXPECT THAT CURRENT DEVELOPING
HOLES IN CLOUDS WOULD FILL IN AS THE NIGHT WEARS ON.

OTHERWISE...TEMP AND WIND TRENDS OF GOING FORECAST APPEAR REASONABLE
AND HAVE MADE NO OTHER SIGNIFICANT CHANGES EXCEPT FOR SKY COVER.

RATZER

//PREV DISCUSSION...
300 PM CDT

BELOW NORMAL TEMPS WILL CHARACTERIZE THE REST OF THE WEEK WITH AN
INFLUX OF MUCH COLDER AND WELL BELOW NORMAL AIR ARRIVING
FRIDAY/SATURDAY BEFORE THINGS MODERATE EARLY NEXT WEEK. THE CLOSED
UPPER LOW THAT HELPED PUSH A COLD FRONTAL BOUNDARY ACROSS THE REGION
THIS MORNING IS NOW CENTERED OVER LAKE SUPERIOR AND TRACKING
EASTWARD. RATHER LOW AMPLITUDE UPPER RIDGING IS MOVING EASTWARD
ACROSS THE WESTERN U.S. AND CANADIAN ROCKIES WITH A SERIES OF LARGER
SCALE TROUGHS OFF THE WEST COAST. OF NOTE IS A WAVE EMBEDDED WITHIN
THE FLOW OVER CENTRAL BRITISH COLUMBIA WHICH WILL CROSS THE AREA AND
SET THE STAGE FOR THE BIG COOL DOWN FRIDAY. AT THE SURFACE...BROAD
LOW PRESSURE IS OVER SOUTHERN ONTARIO WITH THE COLD FRONT THAT
PASSED THIS MORNING NOW WELL TO THE EAST.

TONIGHT THROUGH THURSDAY...QUIET WEATHER WILL PREVAIL THROUGH
WEDNESDAY NIGHT. COLD ADVECTION CONTINUES INTO THE AREA THIS
AFTERNOON AND WILL CONTINUE OVERNIGHT. THE PRESSURE GRADIENT WILL
SUPPORT A STEADY THOUGH NOT TERRIBLY STRONG WESTERLY WIND WHICH WILL
KEEP TEMPS FROM BOTTOMING OUT BUT DO EXPECT THEM TO FALL INTO THE
UPPER 30S TO AROUND 40. THE UPPER TROUGH WILL MOVE NORTHEAST INTO
NORTHERN QUEBEC BUT ANOTHER TROUGH AXIS IS EXPECTED TO AMPLIFY AND
SWING ACROSS THE AREA WEDNESDAY. THE BULK OF THE ASCENT AND DEEPER
MOISTURE ASSOCIATED WITH THIS WILL PASS NORTH OF THE AREA SO AM ONLY
EXPECTING SOME INCREASE IN CLOUD COVER ACROSS NORTHERN AREA AND THIS
MAY BE MINIMAL. THE TROUGH WILL INTRODUCE ANOTHER MODEST PUSH OF
COLDER MID LEVEL AIR SO HIGH TEMPERATURES WILL BE COLDER THAN TODAY
WITH READINGS FROM AROUND 50 NORTH TO THE MID 50S FAR SOUTH. WINDS
WILL TURN NORTHWESTERLY BUT BECOME FAIRLY LIGHT LATE IN THE DAY.
THIS WILL SET THE STAGE FOR COLDER TEMPS WEDNESDAY NIGHT WITH 30S
FOR ALL AREAS OUTSIDE THE IMMEDIATE DOWNTOWN AREA. THE WAVE OVER
BRITISH COLUMBIA TODAY WILL MAKE ITS WAY SOUTHEAST ACROSS THE
NORTHERN PLAINS AND ACROSS THE AREA THURSDAY. GUIDANCE CONTINUES TO
BE MIXED WITH REGARD TO PRECIP POTENTIAL THURSDAY BUT A FAIRLY DRY
ATMOSPHERE WILL BE IN PLACE SO DRY CONDITIONS COULD PREVAIL. WILL GO
AHEAD AND CARRY A SLIGHT CHANCE MENTION FOR MOST AREAS FOR NOW. THE
WAVE WILL BRING A PUSH OF WARMER MID LEVEL AIR AHEAD OF IT SO HIGHS
WILL MODERATE INTO THE LOW TO MID 50S.

FRIDAY AND SATURDAY...GUIDANCE CONTINUES TO BE RATHER CONSISTENT ON
A STRONG UPPER TROUGH DIGGING STRAIGHT SOUTH FROM NORTHERN CANADA
THURSDAY NIGHT AND FRIDAY. THIS WILL PUSH A RELATIVELY WEAK SURFACE
LOW SOUTHEAST ACROSS THE NORTHERN GREAT LAKES WHICH WILL BE
DEEPENING WITH TIME. A VERY STRONG CANADIAN HIGH BUILDS INTO THE
MID/UPPER MISSISSIPPI RIVER VALLEY AND UPPER GREAT LAKES BEHIND THE
LOW INTO FRIDAY NIGHT. H85 TEMPS ARE STILL FORECAST TO FALL TO
AROUND -8C WITH SOME GUIDANCE TRENDING A LITTLE COLDER. THIS WILL
RESULT IN MUCH COLDER SURFACE AIR SPREADING IN THROUGH THE DAY
FRIDAY WHICH IF TIMING HOLDS WILL LIKELY RESULT IN FALLING TEMPS
THROUGH THE DAY. WHILE IT IS STILL EARLY FOR SPECIFICS DO HAVE A
FEW CONCERNS THAT WILL BEAR WATCHING OVER THE NEXT FEW DAYS GIVEN
THE SYNOPTIC SET UP. FIRST IS PRECIP. THE BULK OF SYNOPTIC PRECIP
APPEARS TO REMAIN TO THE EAST OF THE AREA WITH THE UPPER LOW
CENTER REMAINING JUST TO THE EAST WITH THE DEFORMATION AXIS PRECIP
LOOKING SHORT LIVED...THOUGH ENOUGH COLD AIR COULD ARRIVE ALLOWING
FOR A MIX OF PRECIP TYPES. NEXT IS LAKE EFFECT POTENTIAL. IT WILL
CERTAINLY BE COLD ENOUGH FOR LAKE EFFECT PROCESSES WITH LAKE-H85
DELTA TS OF 18-19 C. ORGANIZATION OF BANDS LOOKS TO BE THE
CHALLENGE WITH WINDS STEADILY COMING AROUND FROM NORTHWEST TO
NORTH WITH SPEEDS POTENTIALLY BEING VERY STRONG THROUGH THE
UNSTABLE LAYER. IN ADDITION...WITH THE STRONG HIGH BUILDING IN
INVERSION HEIGHTS MAY QUICKLY FALL PUTTING AN END TO ANY
MEANINGFUL PRECIP...ESPECIALLY BY THE TIME A DUE NORTH FETCH
FAVORING STRONG CONVERGENCE OVER THE LAKE SETS UP FRIDAY
NIGHT/SATURDAY MORNING. LAKE PRECIP TYPE WILL ALSO BE A CONCERN
AND BE DEPENDENT ON LOW LEVEL TEMPS BUT IF PRECIP CAN OCCUR AFTER
DARK FRIDAY THEN IT COULD BE ALL FROZEN. GIVEN THE TIME RANGE AND
THE POTENTIAL LIMITING FACTORS WILL CARRY LOW CHANCE POPS FOR
AREAS NEAR THE LAKE FAVORED BY A NORTH TO NORTH-NORTHEAST WIND.
ANOTHER CONCERN WILL BE THE POTENTIAL FOR VERY STRONG WIND GUSTS
ALONG THE LAKESHORE...AS WELL AS LARGE WAVES IMPACTING THE
SHORELINE THANKS TO THE LONG FETCH OF NORTH WIND. AGAIN...TOO
EARLY TO PIN DOWN DETAILS BUT THE ABOVE CONCERNS ARE HIGHLIGHTED
GIVEN THE SYNOPTIC EXPECTATIONS. THINGS QUIET DOWN SATURDAY AS THE
HIGH MOVES IN LEAVING HIGHS ONLY IN THE 40S.

SUNDAY INTO EARLY NEXT WEEK...THE SURFACE HIGH SHIFTS EAST SUNDAY
WITH A SHARP UPPER RIDGE BUILDING IN FROM THE WEST BRINGING A PUSH
OF WARMER AIR. A LARGE TROUGH WILL BE OVER THE WEST AND GUIDANCE
CONTINUES TO SHOW THIS SPLITTING WITH A TROUGH TRACKING NORTHEAST
ACROSS THE NORTHERN HIGH PLAINS AND INTO MANITOBA INTO MONDAY. THIS
WILL PUSH THE UPPER RIDGE EAST BUT THE ATTENDANT SURFACE LOW WILL
BRING A COLD FRONT TO THE AREA SOME TIME MONDAY OR TUESDAY. WITH THE
PARENT LOW SO FAR TO THE NORTH THE FRONT MAY SLOW AND STALL NEAR THE
AREA. SUNDAY SHOULD SEE HIGHS MODERATE A BIT WITH HIGHS INTO THE 50S
MONDAY. PRECIP TIMING WILL BE DICTATED BY THE TIMING OF THE EXPECTED
FRONT.

MDB

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS WEDNESDAY. CMS

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

GUSTY WESTERLY WINDS WILL DIMINISH THIS EVENING AS THE GRADIENT
SLOWLY WEAKENS BETWEEN DEPARTING LOW PRESSURE ACROSS EASTERN
ONTARIO AND APPROACHING HIGH PRESSURE OVER THE PLAINS. SPEEDS MAY
DIP INTO 7-10KT RANGE OVERNIGHT BUT WILL INCREASE AGAIN WEDNESDAY
MORNING AS THE LOW LEVELS BEGIN TO MIX...WITH GUSTS INTO THE MID
TO UPPER TEEN KT RANGE. AS THE HIGH CONTINUES TO SPREAD SOUTHEAST
OVER THE OHIO VALLEY...GUSTS WILL DIMINISH IN THE AFTERNOON AND
THEN SPEEDS WILL RAPIDLY DIMINISH TO 5 KTS OR LESS WEDNESDAY
EVENING.

BKN/OVC 4-6KFT CIGS MAY LOWER INTO THE 3-4KFT RANGE LATER THIS
EVENING AND OVERNIGHT BUT WITH SOME HOLES SHOWING UP OVER SOUTHERN
WI...CONFIDENCE REGARDING HOW PREVAILING BKN CIGS REMAIN OVERNIGHT
IS LOW...BUT SHOULD REMAIN VFR. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY...SLIGHT CHANCE OF SHRA. LIGHT WEST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA. STRONG/GUSTY NORTH WINDS.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF SHRA. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

&&

.MARINE...
345 PM CDT

DEEPENING LOW PRESSURE CONTINUES TO MOVE NORTHEAST TOWARDS
SOUTHEAST ONTARIO THIS AFTERNOON...WHILE COLDER AIR FILTERS ACROSS
THE LAKE BEHIND THIS SYSTEM. DESPITE THIS LOW MOVING TOWARDS JAMES
BAY TONIGHT...DO EXPECT A FAIRLY TIGHT SURFACE PATTERN TO REMAIN
OVER THE LAKE. WINDS TO 30 KT WILL BE LIKELY ACROSS THE ENTIRE
LAKE TONIGHT...WITH GALE FORCE GUSTS REMAINING A POSSIBILITY AS
WELL. THERE DOES APPEAR TO BE A SMALL WINDOW LATER THIS AFTERNOON
INTO THE EVENING...CONSISTING OF A COUPLE OF HOURS...WHEN MORE
PREVAILING GALES MIGHT BE OBSERVED. THIS DURATION WILL ONCE AGAIN
BE SHORT...AND WITH GUSTS MORE LIKELY TO BE OBSERVED. SO HAVE NOT
ISSUED ANY GALE HEADLINE FOR THIS EVENING...BUT HAVE CONTINUED
GALE FORCE GUST MENTIONING IN THE GLF. WITH THE LOW FURTHER
DEPARTING TO THE NORTHEAST AND HIGH PRESSURE BUILDING NEAR THE
REGION ON WEDNESDAY...DO EXPECT DIMINISHING WINDS ACROSS THE LAKE.
THIS DIMINISHING TREND WILL LIKELY CONTINUE INTO THURSDAY...BEFORE
ATTENTION SHIFTS TOWARDS POSSIBLE STRONG WIND EVENT ON FRIDAY. LOW
PRESSURE WILL MOVE ACROSS THE GREAT LAKES REGION FRIDAY...WHILE
MUCH COLDER AIR AND STRONG HIGH PRESSURE BUILD IN BEHIND IT. THIS
WILL SET THE STAGE FOR POTENTIALLY VERY STRONG NORTHERLY WINDS
OVER THE ENTIRE LAKE. THIS SYSTEM WARRANTS CLOSE MONITORING AS
HIGH END GALES ARE APPEARING A DISTINCT POSSIBILITY...WITH THE
POTENTIAL FOR STORM FORCE WINDS ALSO THERE.

RODRIGUEZ

&&

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

     SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 10 AM
     WEDNESDAY.

&&

$$

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

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







000
FXUS63 KLOT 290151
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
851 PM CDT TUE OCT 28 2014

.DISCUSSION...
850 PM CDT

FOR EVENING UPDATE...

ONLY MINOR CHANGE MADE TO GOING FORECAST THIS EVENING WAS TO SLOW
THE CLEARING OF CLOUD COVER ACROSS THE FORECAST AREA OVERNIGHT.

SUB-995 MB SFC LOW LIFTING SLOWLY AWAY TO THE NORTHEAST ACROSS
ONTARIO THIS EVENING...WITH CYCLONIC WEST-NORTHWEST LOW LEVEL FLOW
IN ITS WAKE ACROSS THE UPPER MIDWEST. SOME DECREASE IN CLOUD COVER
HAS TEMPORARILY OCCURRED ACROSS PORTIONS OF NORTHERN IL EARLY THIS
EVENING...THOUGH GOES WATER VAPOR IMAGERY SHOWS ANOTHER STRONG VORT
DIGGING SOUTHEAST ACROSS THE UPPER MISSISSIPPI VALLEY...WITH A
FAIRLY SOLID AREA OF CLOUD COVER AND EVEN A FEW SPRINKLES NOTED OVER
PARTS OF SOUTHEAST MINNESOTA AND FAR WESTERN WISCONSIN. WITH
APPROACHING VORT AND EXTENSIVE UPSTREAM CLOUD COVER IN CONTINUED LOW
LEVEL COLD ADVECTION REGIME...WOULD EXPECT THAT CURRENT DEVELOPING
HOLES IN CLOUDS WOULD FILL IN AS THE NIGHT WEARS ON.

OTHERWISE...TEMP AND WIND TRENDS OF GOING FORECAST APPEAR REASONABLE
AND HAVE MADE NO OTHER SIGNIFICANT CHANGES EXCEPT FOR SKY COVER.

RATZER

&&

.PREV DISCUSSION...
300 PM CDT

BELOW NORMAL TEMPS WILL CHARACTERIZE THE REST OF THE WEEK WITH AN
INFLUX OF MUCH COLDER AND WELL BELOW NORMAL AIR ARRIVING
FRIDAY/SATURDAY BEFORE THINGS MODERATE EARLY NEXT WEEK. THE CLOSED
UPPER LOW THAT HELPED PUSH A COLD FRONTAL BOUNDARY ACROSS THE REGION
THIS MORNING IS NOW CENTERED OVER LAKE SUPERIOR AND TRACKING
EASTWARD. RATHER LOW AMPLITUDE UPPER RIDGING IS MOVING EASTWARD
ACROSS THE WESTERN U.S. AND CANADIAN ROCKIES WITH A SERIES OF LARGER
SCALE TROUGHS OFF THE WEST COAST. OF NOTE IS A WAVE EMBEDDED WITHIN
THE FLOW OVER CENTRAL BRITISH COLUMBIA WHICH WILL CROSS THE AREA AND
SET THE STAGE FOR THE BIG COOL DOWN FRIDAY. AT THE SURFACE...BROAD
LOW PRESSURE IS OVER SOUTHERN ONTARIO WITH THE COLD FRONT THAT
PASSED THIS MORNING NOW WELL TO THE EAST.

TONIGHT THROUGH THURSDAY...QUIET WEATHER WILL PREVAIL THROUGH
WEDNESDAY NIGHT. COLD ADVECTION CONTINUES INTO THE AREA THIS
AFTERNOON AND WILL CONTINUE OVERNIGHT. THE PRESSURE GRADIENT WILL
SUPPORT A STEADY THOUGH NOT TERRIBLY STRONG WESTERLY WIND WHICH WILL
KEEP TEMPS FROM BOTTOMING OUT BUT DO EXPECT THEM TO FALL INTO THE
UPPER 30S TO AROUND 40. THE UPPER TROUGH WILL MOVE NORTHEAST INTO
NORTHERN QUEBEC BUT ANOTHER TROUGH AXIS IS EXPECTED TO AMPLIFY AND
SWING ACROSS THE AREA WEDNESDAY. THE BULK OF THE ASCENT AND DEEPER
MOISTURE ASSOCIATED WITH THIS WILL PASS NORTH OF THE AREA SO AM ONLY
EXPECTING SOME INCREASE IN CLOUD COVER ACROSS NORTHERN AREA AND THIS
MAY BE MINIMAL. THE TROUGH WILL INTRODUCE ANOTHER MODEST PUSH OF
COLDER MID LEVEL AIR SO HIGH TEMPERATURES WILL BE COLDER THAN TODAY
WITH READINGS FROM AROUND 50 NORTH TO THE MID 50S FAR SOUTH. WINDS
WILL TURN NORTHWESTERLY BUT BECOME FAIRLY LIGHT LATE IN THE DAY.
THIS WILL SET THE STAGE FOR COLDER TEMPS WEDNESDAY NIGHT WITH 30S
FOR ALL AREAS OUTSIDE THE IMMEDIATE DOWNTOWN AREA. THE WAVE OVER
BRITISH COLUMBIA TODAY WILL MAKE ITS WAY SOUTHEAST ACROSS THE
NORTHERN PLAINS AND ACROSS THE AREA THURSDAY. GUIDANCE CONTINUES TO
BE MIXED WITH REGARD TO PRECIP POTENTIAL THURSDAY BUT A FAIRLY DRY
ATMOSPHERE WILL BE IN PLACE SO DRY CONDITIONS COULD PREVAIL. WILL GO
AHEAD AND CARRY A SLIGHT CHANCE MENTION FOR MOST AREAS FOR NOW. THE
WAVE WILL BRING A PUSH OF WARMER MID LEVEL AIR AHEAD OF IT SO HIGHS
WILL MODERATE INTO THE LOW TO MID 50S.

FRIDAY AND SATURDAY...GUIDANCE CONTINUES TO BE RATHER CONSISTENT ON
A STRONG UPPER TROUGH DIGGING STRAIGHT SOUTH FROM NORTHERN CANADA
THURSDAY NIGHT AND FRIDAY. THIS WILL PUSH A RELATIVELY WEAK SURFACE
LOW SOUTHEAST ACROSS THE NORTHERN GREAT LAKES WHICH WILL BE
DEEPENING WITH TIME. A VERY STRONG CANADIAN HIGH BUILDS INTO THE
MID/UPPER MISSISSIPPI RIVER VALLEY AND UPPER GREAT LAKES BEHIND THE
LOW INTO FRIDAY NIGHT. H85 TEMPS ARE STILL FORECAST TO FALL TO
AROUND -8C WITH SOME GUIDANCE TRENDING A LITTLE COLDER. THIS WILL
RESULT IN MUCH COLDER SURFACE AIR SPREADING IN THROUGH THE DAY
FRIDAY WHICH IF TIMING HOLDS WILL LIKELY RESULT IN FALLING TEMPS
THROUGH THE DAY. WHILE IT IS STILL EARLY FOR SPECIFICS DO HAVE A
FEW CONCERNS THAT WILL BEAR WATCHING OVER THE NEXT FEW DAYS GIVEN
THE SYNOPTIC SET UP. FIRST IS PRECIP. THE BULK OF SYNOPTIC PRECIP
APPEARS TO REMAIN TO THE EAST OF THE AREA WITH THE UPPER LOW
CENTER REMAINING JUST TO THE EAST WITH THE DEFORMATION AXIS PRECIP
LOOKING SHORT LIVED...THOUGH ENOUGH COLD AIR COULD ARRIVE ALLOWING
FOR A MIX OF PRECIP TYPES. NEXT IS LAKE EFFECT POTENTIAL. IT WILL
CERTAINLY BE COLD ENOUGH FOR LAKE EFFECT PROCESSES WITH LAKE-H85
DELTA TS OF 18-19 C. ORGANIZATION OF BANDS LOOKS TO BE THE
CHALLENGE WITH WINDS STEADILY COMING AROUND FROM NORTHWEST TO
NORTH WITH SPEEDS POTENTIALLY BEING VERY STRONG THROUGH THE
UNSTABLE LAYER. IN ADDITION...WITH THE STRONG HIGH BUILDING IN
INVERSION HEIGHTS MAY QUICKLY FALL PUTTING AN END TO ANY
MEANINGFUL PRECIP...ESPECIALLY BY THE TIME A DUE NORTH FETCH
FAVORING STRONG CONVERGENCE OVER THE LAKE SETS UP FRIDAY
NIGHT/SATURDAY MORNING. LAKE PRECIP TYPE WILL ALSO BE A CONCERN
AND BE DEPENDENT ON LOW LEVEL TEMPS BUT IF PRECIP CAN OCCUR AFTER
DARK FRIDAY THEN IT COULD BE ALL FROZEN. GIVEN THE TIME RANGE AND
THE POTENTIAL LIMITING FACTORS WILL CARRY LOW CHANCE POPS FOR
AREAS NEAR THE LAKE FAVORED BY A NORTH TO NORTH-NORTHEAST WIND.
ANOTHER CONCERN WILL BE THE POTENTIAL FOR VERY STRONG WIND GUSTS
ALONG THE LAKESHORE...AS WELL AS LARGE WAVES IMPACTING THE
SHORELINE THANKS TO THE LONG FETCH OF NORTH WIND. AGAIN...TOO
EARLY TO PIN DOWN DETAILS BUT THE ABOVE CONCERNS ARE HIGHLIGHTED
GIVEN THE SYNOPTIC EXPECTATIONS. THINGS QUIET DOWN SATURDAY AS THE
HIGH MOVES IN LEAVING HIGHS ONLY IN THE 40S.

SUNDAY INTO EARLY NEXT WEEK...THE SURFACE HIGH SHIFTS EAST SUNDAY
WITH A SHARP UPPER RIDGE BUILDING IN FROM THE WEST BRINGING A PUSH
OF WARMER AIR. A LARGE TROUGH WILL BE OVER THE WEST AND GUIDANCE
CONTINUES TO SHOW THIS SPLITTING WITH A TROUGH TRACKING NORTHEAST
ACROSS THE NORTHERN HIGH PLAINS AND INTO MANITOBA INTO MONDAY. THIS
WILL PUSH THE UPPER RIDGE EAST BUT THE ATTENDANT SURFACE LOW WILL
BRING A COLD FRONT TO THE AREA SOME TIME MONDAY OR TUESDAY. WITH THE
PARENT LOW SO FAR TO THE NORTH THE FRONT MAY SLOW AND STALL NEAR THE
AREA. SUNDAY SHOULD SEE HIGHS MODERATE A BIT WITH HIGHS INTO THE 50S
MONDAY. PRECIP TIMING WILL BE DICTATED BY THE TIMING OF THE EXPECTED
FRONT.

MDB

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS THIS EVENING AND AGAIN WEDNESDAY. CMS

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

GUSTY WESTERLY WINDS WILL DIMINISH THIS EVENING AS THE GRADIENT
SLOWLY WEAKENS BETWEEN DEPARTING LOW PRESSURE ACROSS EASTERN
ONTARIO AND APPROACHING HIGH PRESSURE OVER THE PLAINS. SPEEDS MAY
DIP INTO 7-10KT RANGE OVERNIGHT BUT WILL INCREASE AGAIN WEDNESDAY
MORNING AS THE LOW LEVELS BEGIN TO MIX...WITH GUSTS INTO THE MID
TO UPPER TEEN KT RANGE. AS THE HIGH CONTINUES TO SPREAD SOUTHEAST
OVER THE OHIO VALLEY...GUSTS WILL DIMINISH IN THE AFTERNOON AND
THEN SPEEDS WILL RAPIDLY DIMINISH TO 5 KTS OR LESS WEDNESDAY
EVENING.

BKN/OVC 4-6KFT CIGS MAY LOWER INTO THE 3-4KFT RANGE LATER THIS
EVENING AND OVERNIGHT BUT WITH SOME HOLES SHOWING UP OVER SOUTHERN
WI...CONFIDENCE REGARDING HOW PREVAILING BKN CIGS REMAIN OVERNIGHT
IS LOW...BUT SHOULD REMAIN VFR. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY...SLIGHT CHANCE OF SHRA. LIGHT WEST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA. STRONG/GUSTY NORTH WINDS.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF SHRA. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

&&

.MARINE...
345 PM CDT

DEEPENING LOW PRESSURE CONTINUES TO MOVE NORTHEAST TOWARDS
SOUTHEAST ONTARIO THIS AFTERNOON...WHILE COLDER AIR FILTERS ACROSS
THE LAKE BEHIND THIS SYSTEM. DESPITE THIS LOW MOVING TOWARDS JAMES
BAY TONIGHT...DO EXPECT A FAIRLY TIGHT SURFACE PATTERN TO REMAIN
OVER THE LAKE. WINDS TO 30 KT WILL BE LIKELY ACROSS THE ENTIRE
LAKE TONIGHT...WITH GALE FORCE GUSTS REMAINING A POSSIBILITY AS
WELL. THERE DOES APPEAR TO BE A SMALL WINDOW LATER THIS AFTERNOON
INTO THE EVENING...CONSISTING OF A COUPLE OF HOURS...WHEN MORE
PREVAILING GALES MIGHT BE OBSERVED. THIS DURATION WILL ONCE AGAIN
BE SHORT...AND WITH GUSTS MORE LIKELY TO BE OBSERVED. SO HAVE NOT
ISSUED ANY GALE HEADLINE FOR THIS EVENING...BUT HAVE CONTINUED
GALE FORCE GUST MENTIONING IN THE GLF. WITH THE LOW FURTHER
DEPARTING TO THE NORTHEAST AND HIGH PRESSURE BUILDING NEAR THE
REGION ON WEDNESDAY...DO EXPECT DIMINISHING WINDS ACROSS THE LAKE.
THIS DIMINISHING TREND WILL LIKELY CONTINUE INTO THURSDAY...BEFORE
ATTENTION SHIFTS TOWARDS POSSIBLE STRONG WIND EVENT ON FRIDAY. LOW
PRESSURE WILL MOVE ACROSS THE GREAT LAKES REGION FRIDAY...WHILE
MUCH COLDER AIR AND STRONG HIGH PRESSURE BUILD IN BEHIND IT. THIS
WILL SET THE STAGE FOR POTENTIALLY VERY STRONG NORTHERLY WINDS
OVER THE ENTIRE LAKE. THIS SYSTEM WARRANTS CLOSE MONITORING AS
HIGH END GALES ARE APPEARING A DISTINCT POSSIBILITY...WITH THE
POTENTIAL FOR STORM FORCE WINDS ALSO THERE.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 10 AM
     WEDNESDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 AM WEDNESDAY.

&&

$$

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

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








000
FXUS63 KLOT 290151
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
851 PM CDT TUE OCT 28 2014

.DISCUSSION...
850 PM CDT

FOR EVENING UPDATE...

ONLY MINOR CHANGE MADE TO GOING FORECAST THIS EVENING WAS TO SLOW
THE CLEARING OF CLOUD COVER ACROSS THE FORECAST AREA OVERNIGHT.

SUB-995 MB SFC LOW LIFTING SLOWLY AWAY TO THE NORTHEAST ACROSS
ONTARIO THIS EVENING...WITH CYCLONIC WEST-NORTHWEST LOW LEVEL FLOW
IN ITS WAKE ACROSS THE UPPER MIDWEST. SOME DECREASE IN CLOUD COVER
HAS TEMPORARILY OCCURRED ACROSS PORTIONS OF NORTHERN IL EARLY THIS
EVENING...THOUGH GOES WATER VAPOR IMAGERY SHOWS ANOTHER STRONG VORT
DIGGING SOUTHEAST ACROSS THE UPPER MISSISSIPPI VALLEY...WITH A
FAIRLY SOLID AREA OF CLOUD COVER AND EVEN A FEW SPRINKLES NOTED OVER
PARTS OF SOUTHEAST MINNESOTA AND FAR WESTERN WISCONSIN. WITH
APPROACHING VORT AND EXTENSIVE UPSTREAM CLOUD COVER IN CONTINUED LOW
LEVEL COLD ADVECTION REGIME...WOULD EXPECT THAT CURRENT DEVELOPING
HOLES IN CLOUDS WOULD FILL IN AS THE NIGHT WEARS ON.

OTHERWISE...TEMP AND WIND TRENDS OF GOING FORECAST APPEAR REASONABLE
AND HAVE MADE NO OTHER SIGNIFICANT CHANGES EXCEPT FOR SKY COVER.

RATZER

&&

.PREV DISCUSSION...
300 PM CDT

BELOW NORMAL TEMPS WILL CHARACTERIZE THE REST OF THE WEEK WITH AN
INFLUX OF MUCH COLDER AND WELL BELOW NORMAL AIR ARRIVING
FRIDAY/SATURDAY BEFORE THINGS MODERATE EARLY NEXT WEEK. THE CLOSED
UPPER LOW THAT HELPED PUSH A COLD FRONTAL BOUNDARY ACROSS THE REGION
THIS MORNING IS NOW CENTERED OVER LAKE SUPERIOR AND TRACKING
EASTWARD. RATHER LOW AMPLITUDE UPPER RIDGING IS MOVING EASTWARD
ACROSS THE WESTERN U.S. AND CANADIAN ROCKIES WITH A SERIES OF LARGER
SCALE TROUGHS OFF THE WEST COAST. OF NOTE IS A WAVE EMBEDDED WITHIN
THE FLOW OVER CENTRAL BRITISH COLUMBIA WHICH WILL CROSS THE AREA AND
SET THE STAGE FOR THE BIG COOL DOWN FRIDAY. AT THE SURFACE...BROAD
LOW PRESSURE IS OVER SOUTHERN ONTARIO WITH THE COLD FRONT THAT
PASSED THIS MORNING NOW WELL TO THE EAST.

TONIGHT THROUGH THURSDAY...QUIET WEATHER WILL PREVAIL THROUGH
WEDNESDAY NIGHT. COLD ADVECTION CONTINUES INTO THE AREA THIS
AFTERNOON AND WILL CONTINUE OVERNIGHT. THE PRESSURE GRADIENT WILL
SUPPORT A STEADY THOUGH NOT TERRIBLY STRONG WESTERLY WIND WHICH WILL
KEEP TEMPS FROM BOTTOMING OUT BUT DO EXPECT THEM TO FALL INTO THE
UPPER 30S TO AROUND 40. THE UPPER TROUGH WILL MOVE NORTHEAST INTO
NORTHERN QUEBEC BUT ANOTHER TROUGH AXIS IS EXPECTED TO AMPLIFY AND
SWING ACROSS THE AREA WEDNESDAY. THE BULK OF THE ASCENT AND DEEPER
MOISTURE ASSOCIATED WITH THIS WILL PASS NORTH OF THE AREA SO AM ONLY
EXPECTING SOME INCREASE IN CLOUD COVER ACROSS NORTHERN AREA AND THIS
MAY BE MINIMAL. THE TROUGH WILL INTRODUCE ANOTHER MODEST PUSH OF
COLDER MID LEVEL AIR SO HIGH TEMPERATURES WILL BE COLDER THAN TODAY
WITH READINGS FROM AROUND 50 NORTH TO THE MID 50S FAR SOUTH. WINDS
WILL TURN NORTHWESTERLY BUT BECOME FAIRLY LIGHT LATE IN THE DAY.
THIS WILL SET THE STAGE FOR COLDER TEMPS WEDNESDAY NIGHT WITH 30S
FOR ALL AREAS OUTSIDE THE IMMEDIATE DOWNTOWN AREA. THE WAVE OVER
BRITISH COLUMBIA TODAY WILL MAKE ITS WAY SOUTHEAST ACROSS THE
NORTHERN PLAINS AND ACROSS THE AREA THURSDAY. GUIDANCE CONTINUES TO
BE MIXED WITH REGARD TO PRECIP POTENTIAL THURSDAY BUT A FAIRLY DRY
ATMOSPHERE WILL BE IN PLACE SO DRY CONDITIONS COULD PREVAIL. WILL GO
AHEAD AND CARRY A SLIGHT CHANCE MENTION FOR MOST AREAS FOR NOW. THE
WAVE WILL BRING A PUSH OF WARMER MID LEVEL AIR AHEAD OF IT SO HIGHS
WILL MODERATE INTO THE LOW TO MID 50S.

FRIDAY AND SATURDAY...GUIDANCE CONTINUES TO BE RATHER CONSISTENT ON
A STRONG UPPER TROUGH DIGGING STRAIGHT SOUTH FROM NORTHERN CANADA
THURSDAY NIGHT AND FRIDAY. THIS WILL PUSH A RELATIVELY WEAK SURFACE
LOW SOUTHEAST ACROSS THE NORTHERN GREAT LAKES WHICH WILL BE
DEEPENING WITH TIME. A VERY STRONG CANADIAN HIGH BUILDS INTO THE
MID/UPPER MISSISSIPPI RIVER VALLEY AND UPPER GREAT LAKES BEHIND THE
LOW INTO FRIDAY NIGHT. H85 TEMPS ARE STILL FORECAST TO FALL TO
AROUND -8C WITH SOME GUIDANCE TRENDING A LITTLE COLDER. THIS WILL
RESULT IN MUCH COLDER SURFACE AIR SPREADING IN THROUGH THE DAY
FRIDAY WHICH IF TIMING HOLDS WILL LIKELY RESULT IN FALLING TEMPS
THROUGH THE DAY. WHILE IT IS STILL EARLY FOR SPECIFICS DO HAVE A
FEW CONCERNS THAT WILL BEAR WATCHING OVER THE NEXT FEW DAYS GIVEN
THE SYNOPTIC SET UP. FIRST IS PRECIP. THE BULK OF SYNOPTIC PRECIP
APPEARS TO REMAIN TO THE EAST OF THE AREA WITH THE UPPER LOW
CENTER REMAINING JUST TO THE EAST WITH THE DEFORMATION AXIS PRECIP
LOOKING SHORT LIVED...THOUGH ENOUGH COLD AIR COULD ARRIVE ALLOWING
FOR A MIX OF PRECIP TYPES. NEXT IS LAKE EFFECT POTENTIAL. IT WILL
CERTAINLY BE COLD ENOUGH FOR LAKE EFFECT PROCESSES WITH LAKE-H85
DELTA TS OF 18-19 C. ORGANIZATION OF BANDS LOOKS TO BE THE
CHALLENGE WITH WINDS STEADILY COMING AROUND FROM NORTHWEST TO
NORTH WITH SPEEDS POTENTIALLY BEING VERY STRONG THROUGH THE
UNSTABLE LAYER. IN ADDITION...WITH THE STRONG HIGH BUILDING IN
INVERSION HEIGHTS MAY QUICKLY FALL PUTTING AN END TO ANY
MEANINGFUL PRECIP...ESPECIALLY BY THE TIME A DUE NORTH FETCH
FAVORING STRONG CONVERGENCE OVER THE LAKE SETS UP FRIDAY
NIGHT/SATURDAY MORNING. LAKE PRECIP TYPE WILL ALSO BE A CONCERN
AND BE DEPENDENT ON LOW LEVEL TEMPS BUT IF PRECIP CAN OCCUR AFTER
DARK FRIDAY THEN IT COULD BE ALL FROZEN. GIVEN THE TIME RANGE AND
THE POTENTIAL LIMITING FACTORS WILL CARRY LOW CHANCE POPS FOR
AREAS NEAR THE LAKE FAVORED BY A NORTH TO NORTH-NORTHEAST WIND.
ANOTHER CONCERN WILL BE THE POTENTIAL FOR VERY STRONG WIND GUSTS
ALONG THE LAKESHORE...AS WELL AS LARGE WAVES IMPACTING THE
SHORELINE THANKS TO THE LONG FETCH OF NORTH WIND. AGAIN...TOO
EARLY TO PIN DOWN DETAILS BUT THE ABOVE CONCERNS ARE HIGHLIGHTED
GIVEN THE SYNOPTIC EXPECTATIONS. THINGS QUIET DOWN SATURDAY AS THE
HIGH MOVES IN LEAVING HIGHS ONLY IN THE 40S.

SUNDAY INTO EARLY NEXT WEEK...THE SURFACE HIGH SHIFTS EAST SUNDAY
WITH A SHARP UPPER RIDGE BUILDING IN FROM THE WEST BRINGING A PUSH
OF WARMER AIR. A LARGE TROUGH WILL BE OVER THE WEST AND GUIDANCE
CONTINUES TO SHOW THIS SPLITTING WITH A TROUGH TRACKING NORTHEAST
ACROSS THE NORTHERN HIGH PLAINS AND INTO MANITOBA INTO MONDAY. THIS
WILL PUSH THE UPPER RIDGE EAST BUT THE ATTENDANT SURFACE LOW WILL
BRING A COLD FRONT TO THE AREA SOME TIME MONDAY OR TUESDAY. WITH THE
PARENT LOW SO FAR TO THE NORTH THE FRONT MAY SLOW AND STALL NEAR THE
AREA. SUNDAY SHOULD SEE HIGHS MODERATE A BIT WITH HIGHS INTO THE 50S
MONDAY. PRECIP TIMING WILL BE DICTATED BY THE TIMING OF THE EXPECTED
FRONT.

MDB

&&

.AVIATION...

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

* GUSTY WESTERLY WINDS THIS EVENING AND AGAIN WEDNESDAY. CMS

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

GUSTY WESTERLY WINDS WILL DIMINISH THIS EVENING AS THE GRADIENT
SLOWLY WEAKENS BETWEEN DEPARTING LOW PRESSURE ACROSS EASTERN
ONTARIO AND APPROACHING HIGH PRESSURE OVER THE PLAINS. SPEEDS MAY
DIP INTO 7-10KT RANGE OVERNIGHT BUT WILL INCREASE AGAIN WEDNESDAY
MORNING AS THE LOW LEVELS BEGIN TO MIX...WITH GUSTS INTO THE MID
TO UPPER TEEN KT RANGE. AS THE HIGH CONTINUES TO SPREAD SOUTHEAST
OVER THE OHIO VALLEY...GUSTS WILL DIMINISH IN THE AFTERNOON AND
THEN SPEEDS WILL RAPIDLY DIMINISH TO 5 KTS OR LESS WEDNESDAY
EVENING.

BKN/OVC 4-6KFT CIGS MAY LOWER INTO THE 3-4KFT RANGE LATER THIS
EVENING AND OVERNIGHT BUT WITH SOME HOLES SHOWING UP OVER SOUTHERN
WI...CONFIDENCE REGARDING HOW PREVAILING BKN CIGS REMAIN OVERNIGHT
IS LOW...BUT SHOULD REMAIN VFR. CMS

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

* HIGH FOR WINDS THRU THE PERIOD. CMS

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

* THURSDAY...SLIGHT CHANCE OF SHRA. LIGHT WEST WINDS.
* FRIDAY...SLIGHT CHANCE OF SHRA. STRONG/GUSTY NORTH WINDS.
* SATURDAY...DRY/VFR. NORTHEAST WINDS.
* SUNDAY...SLIGHT CHANCE OF SHRA. SOUTH WINDS.
* MONDAY...CHANCE OF SHRA. GUSTY SOUTH WINDS.

&&

.MARINE...
345 PM CDT

DEEPENING LOW PRESSURE CONTINUES TO MOVE NORTHEAST TOWARDS
SOUTHEAST ONTARIO THIS AFTERNOON...WHILE COLDER AIR FILTERS ACROSS
THE LAKE BEHIND THIS SYSTEM. DESPITE THIS LOW MOVING TOWARDS JAMES
BAY TONIGHT...DO EXPECT A FAIRLY TIGHT SURFACE PATTERN TO REMAIN
OVER THE LAKE. WINDS TO 30 KT WILL BE LIKELY ACROSS THE ENTIRE
LAKE TONIGHT...WITH GALE FORCE GUSTS REMAINING A POSSIBILITY AS
WELL. THERE DOES APPEAR TO BE A SMALL WINDOW LATER THIS AFTERNOON
INTO THE EVENING...CONSISTING OF A COUPLE OF HOURS...WHEN MORE
PREVAILING GALES MIGHT BE OBSERVED. THIS DURATION WILL ONCE AGAIN
BE SHORT...AND WITH GUSTS MORE LIKELY TO BE OBSERVED. SO HAVE NOT
ISSUED ANY GALE HEADLINE FOR THIS EVENING...BUT HAVE CONTINUED
GALE FORCE GUST MENTIONING IN THE GLF. WITH THE LOW FURTHER
DEPARTING TO THE NORTHEAST AND HIGH PRESSURE BUILDING NEAR THE
REGION ON WEDNESDAY...DO EXPECT DIMINISHING WINDS ACROSS THE LAKE.
THIS DIMINISHING TREND WILL LIKELY CONTINUE INTO THURSDAY...BEFORE
ATTENTION SHIFTS TOWARDS POSSIBLE STRONG WIND EVENT ON FRIDAY. LOW
PRESSURE WILL MOVE ACROSS THE GREAT LAKES REGION FRIDAY...WHILE
MUCH COLDER AIR AND STRONG HIGH PRESSURE BUILD IN BEHIND IT. THIS
WILL SET THE STAGE FOR POTENTIALLY VERY STRONG NORTHERLY WINDS
OVER THE ENTIRE LAKE. THIS SYSTEM WARRANTS CLOSE MONITORING AS
HIGH END GALES ARE APPEARING A DISTINCT POSSIBILITY...WITH THE
POTENTIAL FOR STORM FORCE WINDS ALSO THERE.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...INDIANA NEARSHORE WATERS UNTIL 10 AM
     WEDNESDAY.

     SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 4 AM WEDNESDAY.

&&

$$

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