FXUS63 KLSX 080451
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1051 PM CST MON DEC 7 2009

.DISCUSSION...
/219 PM CST MON DEC 7 2009/

MAIN CONCERN CONTINUES TO BE WITH THE SIGNIFICANT WINTER STORM THAT 
WILL AFFECT THE AREA TOMORROW INTO WEDNESDAY.  GLOBAL MODELS ARE 
SHOWING GOOD AGREEMENT WITH THE STORM...SHOWING AN ALMOST IDENTICAL
PATH OF THE 850MB LOW FROM SRN KS THRU CNTRL MO INTO NERN IL ON
TUESDAY NIGHT. THIS KEEPS THE SRN EDGE OF THE HEAVIEST SNOW BAND
ACROSS THE NRN CWA. HAVE ENOUGH CONFIDENCE TO UPGRADE TO A WINTER
STORM WARNING FROM THE FAR NRN PART OF THE CWA...WITH A ONE COUNTY
WIDE ADVISORY JUST TO THE SOUTH.

AFTER A DRY EVENING...PRECIPITATION CHANCES WILL INCREASE OVER THE 
NWRN PART OF THE CWA OVERNIGHT AS LARGE SCALE ASCENT INCREASES AHEAD
OF THE SHORTWAVE TROUGH. CHANCES WILL ALSO INCREASE OVER THE FAR
SRN PART OF THE CWA AS LOW LEVEL MOISTURE CONVERGENCE RAMPS UP
AHEAD OF A BROAD 35KT LOW LEVEL JET. HAVE LIKELY OR CATEGORICAL
POPS ACROSS THE CWA AS AFOREMENTIONED FORCING SPREADS ACROSS THE
AREA AND CONTINUE THESE HIGH POPS THROUGH WEDNESDAY AS CLOSED LOW
RACES ACROSS THE AREA. BEST CHANCE TOMORROW NIGHT WILL BE OVER THE
NRN CWA WHERE MID LEVEL FRONTOGENESIS IN THE DEFORMATION ZONE WILL
BE THE STRONGEST...WITH LESSER CHANCES IN THE DRY SLOT TO THE
SOUTH OF THE LOW. SUBSIDENCE SETS IN VERY QUICKLY ON WEDNESDAY IN
THE WAKE OF THE LOW...THOUGH KEPT SCT -SHSN/FLURRIES GOING IN THE
LOW LEVEL CYCLONIC FLOW.

PRECIPIATION TYPE IS STILL IN QUESTION AS LOW LEVEL JET BRINGS QUITE 
A BIT OF WARM AIR INTO THE SYSTEM. MADE NO BIG CHANGES TO GOING
WEATHER TYPE...GOING WITH MAINLY SNOW IN THE FAR NW WHERE AMOUNTS
SHOULD CLIMB INTO THE 4-8 INCH RANGE WITH A RAPID TAPERING TO THE
SOUTHEAST OF THERE WHERE SLEET...RAIN OR EVEN SOME FREEZING RAIN
WILL TAKE AWAY FROM THE SNOW TOTALS. HAVE ONE INCH SNOW
ACCUMULATION NORTH OF A COU-PPQ LINE. THIS AGREES WELL WITH THE
MAJORITY OF ANALOGS ON THE SLU/CIPS WEBSITE.

KEPT THE SAME IDEA OF WINDY CONDITIONS SETTING IN LATE TUESDAY NIGHT 
AND WEDNESDAY NIGHT AS SFC LOW CONTINUES TO DEEPING.  KEPT BLOWING 
SNOW OVER WARNING AREA...AND MAY NEED TO CONSIDER A WIND ADVISORY 
OUTSIDE OF GOING HEADLINES.  WEDNESDAY LOOKS LIKE A RAW DAY AS WIND 
CHILLS RAPIDLY FALL.

NOT MUCH CONFIDENCE WITH THE FORECAST LATE THIS WEEK INTO EARLY NEXT 
WEEK AS MOST OF THE MODELS ARE NOT CONSISTENT WITH TIMING SHORTWAVE 
TROUGHS THROUGH QUASI-ZONAL FLOW.  HAVE KEPT JUST SLIGHT CHANCES FOR 
RAIN/SNOW GOING FRIDAY INTO SATURDAY AND AGAIN SUNDAY NIGHT AND 
MONDAY AS THERE IS NOT ENOUGH AGREEMENT TO INTRODUCE MENTIONABLE 
PRECIPITATION IN THE EXTENDED AT THIS POINT.  TEMPERATURES ARE A 
BLEND OF GOING TEMPS...HPC GUIDANCE AND THE GEFS MEAN MOS.

BRITT

&&

.AVIATION...
/1024 PM CST MON DEC 7 2009/

FOR THE 06Z TAFS...LOW LEVEL CLOUD COVER OF AROUND 1000 FT IN UIN
AND 1000-1500 FT IN COU SHOULD CONTINUE LATE TGT...WITH AROUND
2500 FT SCT-BKN IN STL/SUS.  AS LOW-MID LEVEL WAA INCREASES ACROSS
THE CWA THROUGH THE LATE NGT LGT SNOW SHOULD MOVE INTO UIN AROUND
12Z TUE OR SHORTLY AFTER...WITH A MIX OF MAINLY LGT SNOW AND SLEET
IN COU BEGINNING AROUND 14Z TUE...AND IN STL/SUS BY 15Z TUE. AS
THE LOW LEVELS CONTINUE TO WARM UP THROUGH THE DAY THE
PRECIPITATION TYPE WILL LIKELY CHANGE TO RAIN IN STL/SUS BY 18Z
TUE AND TO RAIN OR A MIX OF RAIN...SLEET AND SNOW IN COU. AT UIN
THE SNOW WILL CHANGE TO MAINLY SNOW AND SLEET BY 18Z TUE. THE
CLOUD CEILING WILL LOWER TO AROUND 800FT BY 14-15Z TUE AS THE
BNDRY LAYER SATURATES. NELY SFC WNDS WILL STRENGTHEN LATE TGT AND
THROUGH THE DAY ON TUE BACKING AROUND TO AN ELY DIRECTION ON TUE.
STL/SUS WILL GET DRY SLOTTED TUE EVNG SHUTTING OFF MUCH OF THE
PRECIPITATION...MAY BE SOME DRIZZLE. UIN MAY CHANGE BACK TO ALL
SNOW JUST BEFORE 06Z WED WITH THE BULK OF THE DEFORMATION TYPE
PRECIPITATION SETTING UP JUST N-NW OF UIN TUE EVNG WITH A SFC LOW
MOVING FROM W CNTRL MO TO NERN MO TUE EVNG.

GKS

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...WINTER STORM WARNING FROM 6 AM TUESDAY TO NOON CST WEDNESDAY FOR 
     KNOX-LEWIS-MARION-SHELBY.

     WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO NOON CST WEDNESDAY 
     FOR MONROE-RALLS.

IL...WINTER STORM WARNING FROM 6 AM TUESDAY TO NOON CST WEDNESDAY FOR 
     ADAMS IL.

     WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO NOON CST WEDNESDAY 
     FOR BROWN IL-PIKE IL.

&&

$$

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