Area Forecast Discussion
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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.

&&

$$

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