Area Forecast Discussion
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000
FXUS63 KLOT 262211
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
411 PM CST WED NOV 26 2014

.SHORT TERM...
311 PM CST

THROUGH FRIDAY...

REST OF TODAY INTO THIS EVENING...

IN IMMEDIATE NEAR TERM...SNOW ASSOCIATED WITH CLIPPER IS LIKELY TO
REMAIN ALMOST COMPLETE SOUTHWEST OF CWA...BUT COULD BE CLOSE TO
FAR SOUTHWEST FOR A FEW HRS INTO EARLY EVENING WHERE MAINLY SLIGHT
POPS HAVE BEEN CARRIED.

TONIGHT THROUGH FRIDAY...

THE BIG STORY OVER THE NEXT FEW DAYS WILL BE A HUGE TEMPERATURE
SWING FROM ONE OF THE COLDEST THANKSGIVING DAYS ON RECORD TO HIGHS
POTENTIALLY WELL INTO THE 50S FOR MUCH OF THE AREA OVER THE
WEEKEND. HIGHLY AMPLIFIED PATTERN OVER THE CONUS TODAY...WITH A
150+ KT UPPER JET CARVING OUT CURRENT DEEP TROUGH OVER THE EASTERN
HALF. 12Z RAOB SAMPLED -17 C AT 850 MB AT INL TODAY AND THIS AIR
MASS WILL SURGE SOUTH TOWARD AREA FOR BRIEF BLAST OF ARCTIC AIR
THAT WILL ARRIVE LATE TONIGHT INTO THANKSGIVING MORNING. THERE
SHOULD BE ENOUGH LIFT AS SHEARED OUT VORT/TROUGH AXIS CROSSES THE
AREA TONIGHT FOR FLURRIES TO BE SQUEEZED OUT FOR MAINLY
NORTH/NORTHEAST CWA OVERNIGHT INTO VERY EARLY THURSDAY.

TEMPERATURES WILL LIKELY BE FALLING INTO MID TEENS-LOW 20S BY MID
THURSDAY MORNING...FOLLOWED BY ONLY MINOR RECOVERY INTO LOW
20S/AROUND 20 NORTHWEST TO UPPER 20S FAR SOUTHEAST. PARAMETERS FOR
LAKE EFFECT SNOW WILL BE QUITE FAVORABLE ON THURSDAY...BUT WEST-
NORTHWEST FLOW IS EXPECTED TO KEEP FOCUS TO THE EAST OF THE CWA.
HAVE ONLY LOW CHANCE POPS IN NORTHEAST PORTER COUNTY...BUT IT MAY
BE VERY CLOSE FOR THAT AREA BEING CLIPPED BY AT LEAST PERSISTENT
LIGHT LAKE SNOWS.

THERE SHOULD BE A PERIOD OF PARTLY CLOUDY SKIES THURSDAY EVENING
INTO THE FIRST PART OF THE NIGHT AS SFC HIGH CROSSES THE AREA.
THIS WOULD PROVIDE SEVERAL HOURS OF GOOD RADIATIONAL COOLING AND
POTENTIAL FOR UPPER SINGLE DIGITS TO LOW TEENS WEST AND NW OF
CHICAGO.

INCREASING MID/HIGH CLOUDS AND WAA THEN SHOULD RESULT IN RISING
TEMPS TOWARD DAYBREAK. ISENTROPIC ASCENT AND UPPER FORCING WILL
RESULT IN PRECIP BREAKING OUT MAINLY NORTH OF CWA ON
FRIDAY...THOUGH FAR NORTHEAST COULD BE CLIPPED WHERE I MAINTAINED
SLIGHT CHANCE POPS. CONTINUE TO SUSPECT THAT MODELS ARE TOO COLD
WITH TEMPS ON FRIDAY DUE TO TOO MUCH SNOW COVER...SO STAYED
SIMILAR TO PREVIOUS FORECAST WITH UPPER 30S-NEAR 40 FOR SOUTHEAST
2/3 OF CWA.

RC

&&

.LONG TERM...
311 PM CST

FRIDAY NIGHT THROUGH THURSDAY...

AS FLOW  RAPIDLY TURNS ZONAL ON FRIDAY NIGHT...ANY MINOR COOLING
IN THE EVENING WILL LIKELY BE FOLLOWED BY RISING TEMPERATURES
OVERNIGHT. THIS WILL OCCUR AS VERY MILD AIR MASS RAPIDLY ADVECTS
INTO AREA...WITH BOTH ECMWF AND GFS SUGGESTING LOW-MID TEENS
CELSIUS AT 850 BY LATE DAY SATURDAY. LOCAL CLIMO SUGGESTS AT LEAST
LOW-MID 50S FOR HIGHS ON SATURDAY AND PROBABLY WARMER EVEN WITH
SOME CLOUD COVER. GUIDANCE CONTINUES TO SLOW FROPA ON SUNDAY...SO
EVEN WARMER TEMPS SATURDAY NIGHT WILL PROVIDE CHANCE FOR SOUTHERN
CWA ESPECIALLY TO NEAR 60 DEGREES FOR HIGHS ON SUNDAY! LIGHT
RAIN MAY BREAK OUT AS FRONT CROSSES THE AREA BUT FORCING IS
LIMITED. MODIFIED ARCTIC AIR WILL OOZE BACK IN ON SUNDAY
NIGHT...WITH CHILLY CONDITIONS MONDAY AND TUESDAY UNDER EXPANSIVE
HIGH PRESSURE. OPERATIONAL AND ENSEMBLE GUIDANCE VARIES LARGELY
BEYOND THIS...SO STAYED CLOSE TO A CONSENSUS BLEND...YIELDING
CLOSE TO AVERAGE TEMPERATURES. PRECIP CHANCES WILL DEPEND ON HOW
CLOSE BAROCLINIC ZONE CAN GET TO OUR AREA...WITH A SIGNIFICANT
TEMPERATURE GRADIENT PERSISTING ACROSS THE MIDWEST BUT EITHER
NEARBY OR SHUNTED WELL SOUTH.

RC

&&

.AVIATION...

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

* MVFR CEILINGS THROUGH THE PERIOD.

* EASTERLY WINDS THROUGH EARLY EVENING...BELOW 10 KT...THEN
  BACKING THROUGH NORTHERLY TO NORTHWESTERLY BY THURSDAY MORNING.

* CHANCE OF SCT SNOW SHOWERS/FLURRIES WITH FROPA LATE TONIGHT.

KREIN

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

A CLIPPER SYSTEM WILL CONTINUE SHIFTING SOUTHEASTWARD ACROSS
MISSOURI TODAY...AND THE TENNESSEE VALLEY TONIGHT. THIS TRACK WILL
FAVOR LIGHT SNOW REMAINING WELL WEST AND SOUTH OF MAIN TERMINALS
TODAY. HOWEVER...THE MVFR CIGS IN THE 1500 TO 2000 FOOT RANGE WILL
CONTINUE ACROSS THE AREA THROUGH MUCH OF THE PERIOD. ANOTHER WEAK
WEATHER DISTURBANCE IS EXPECTED TO MOVE OVER THE AREA LATER
TONIGHT INTO THURSDAY MORNING...AND THIS COULD PRODUCE A PERIOD OF
VERY LIGHT SNOW OR FLURRIES ACROSS THE TERMINALS INTO THURSDAY
MORNING. OTHERWISE...LIGHT EAST-SOUTHEASTERLY WINDS WILL GRADUALLY
BACK MORE NORTHEASTERLY LATER THIS AFTERNOON AND EVENING...THEN
NORTHWEST LATER TONIGHT INTO THURSDAY.

KJB

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

* MEDIUM-HIGH CONFIDENCE IN CIG TRENDS.

* HIGH CONFIDENCE IN WIND SPEED/DIRECTION.

* MEDIUM CONFIDENCE IN SCT SNOW SHOWERS/FLURRIES LATE TONIGHT.

KREIN

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

THURSDAY NIGHT...VFR.

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

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...VFR.

TUESDAY...CHANCE OF RAIN LATE.

RODRIGUEZ

&&

.MARINE...
335 PM CST

A STALLED WEST-EAST FRONTAL BOUNDARY STRETCHED ACROSS NORTHERN LAKE
MICHIGAN WILL GET A GOOD PUSH SOUTH TONIGHT AS COLDER AIR SURGES IN
BEHIND DEPARTING LOW PRESSURE OVER CENTRAL ILLINOIS.  HIGH PRESSURE
OVER THE SOUTHERN CANADIAN PRARIE PROVANCES WILL HELP DRIVE THE
COLDER AIR SOUTH. WINDS WILL INCREASE QUICKLY BEHIND THE FRONT EARLY
THURSDAY FROM NORTH TO SOUTH... WITH A BRIEF PERIOD OF GALE FORCE
GUSTS IS EXPECTED. HIGH PRESSURE RIDGING THEN QUICKLY BUILDS EAST
ACROSS THE LAKE THURSDAY NIGHT ALLOWING WINDS AND WAVES TO THEN
QUICKLY SUBSIDE.  WINDS AND WAVES THEN QUICKLY INCREASE AGAIN FRIDAY
AS THE PRESSURE GRAIDNET TIGHTENS BEHIND THE HIGH AND AHEAD OF
DEEPENNING LOW PRESSURE OPVER THE PLAINS.

THIS LOW PRESSUE AREA WILL MOVE TO THE U.P. OF MICHIGAN BY EARLY
SUNDAY.  A COLD FRONT ASSOCAITED WITH THIS LOW WILL MOVE EAST ACROSS
THE LAKE DURING THE DAY SUNDAY... WITH BRISK NORTHWEST FLOW
INTENSIFYING BEHIND THE FRONT INTO MONDAY.

ED F

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...6 AM THURSDAY TO
     MIDNIGHT FRIDAY.

     SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...9 AM THURSDAY TO 6
     PM THURSDAY.

&&

$$

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