FXUS63 KLSX 011104
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
504 AM CST TUE DEC 1 2009

.DISCUSSION...
/403 AM CST TUE DEC 1 2009/

ABOVE NORMAL TEMPERATURES EXPECTED TDA WITH ONLY SOME CIRRUS CLOUDS 
TO LIMIT SOLAR INSOLATION AND SWLY LOW LEVEL WINDS.  INCREASING 
CLOUDINESS IS EXPECTED TGT AS TWO WEATHER SYSTEMS APPROACH THE
AREA. A SHRTWV TROF CURRENTLY OVER NWRN MT WILL BE MOVING SEWD
THRU THE NRN PLAINS...WHILE A MID-UPPER LEVEL LOW OVER MEXICO
WILL BE MOVING EWD THRU TX. THE NRN STREAM SHRTWV TROF WILL SEND A
CDFNT SEWD THRU THE CWA LATE TGT AND WED...WHILE THE SRN MID-
UPPER LEVEL LOW WILL MOVE NEWD THRU AR WED AFTN AND THRU WRN
PORTIONS OF KY TN WED EVNG. DISCOUNTED THE GFS MODEL AS IT
CONTINUES TO BE AN OUTLIER WITH THE UPPER/SFC LOW TOO FAR S-SE ON
WED...AND IT ALSO APPEARS TOO QUICK WITH THIS FEATURE WED AFTN AND
EVNG. PREFER THE NAM...ECMWF AND CANADIAN GEM MODELS SOLUTIONS
WHICH ARE FAIRLY SIMILAR WITH THE UPPER/SFC LOW TRACK...ALTHOUGH
THE GEM MODEL MAY BE KEEPING THE MID LEVEL LOW CLOSED OFF A
LITTLE TOO LONG WED AFTN INTO THE EVNG AND HENCE A LITTLE TOO
ROBUST ON THE DEFORMATION TYPE PRECIPITATION. MODELS CONTINUE TO
INDICATE STRONG UPPER LEVEL DIVERGENCE ACROSS THE CWA LATE WED
MRNG INTO THE EVNG WITH COUPLING OF THE NRN AND SRN STREAM ULJ
STREAKS. THE MODELS ALSO GENERATE MOST OF THE QPF WED AND WED EVNG
ACROSS THE SERN HALF OF THE CWA ON THE LEFT SIDE OF THE TRACK OF
THE MID LEVEL LOW...850 LOW AND SFC LOW. SFC TEMPERATURES SHOULD
FALL WED AFTN AS COLD AIR FILTERS INTO THE CWA FM NW TO SE BEHIND
THE SEWD ADVANCING CDFNT. THE MODEL FORECAST SOUNDINGS ARE A
LITTLE SLOWER IN CHANGING THE RAIN OVER TO SNOW COMPARED TO
YESTERDAYS MODEL FORECAST SOUNDINGS WHICH COULD LEAD TO SLIGHTLY
LESS SNOW ACCUMULATION THAN PREVIOUSLY THOUGHT...ALTHOUGH THERE
IS STILL PLENTY OF UNCERTAINTY WITH THE TRACK OF THE UPPER/SFC LOW
AND THE TEMPERATURE FORECAST WED AFTN AND EVNG. IT CURRENTLY
APPEARS THAT THE RAIN WILL CHANGE OVER TO SNOW IN STL AROUND
5 PM...IN FAM AROUND 7 PM...AND SLO AROUND 8 PM. THE SNOW SHOULD
LAST ABOUT THREE HOURS BEFORE TAPERING OFF TO FLURRIES. THE CHANCE
OF ACCUMULATING SNOW SHOULD END BY ABOUT MIDNIGHT WED NGT AS THE
STORM SYSTEM PULLS NE OF THE REGION. THE WARM GROUND AND ABOVE
FREEZING SFC TEMPERATURES SHOULD LIMIT ACCUMULATION...BUT SOME
AREAS FROM THE STL METRO AREA S AND E COULD POSSIBLY PICK UP 1-2
INCHES OF SNOW. A VERY COLD PERIOD IS EXPECTED THU AND FRI WITH A
LARGE MID-UPPER LEVEL LOW MOVING SLOWLY EWD THRU THE NRN PLAINS
AND GREAT LAKES REGION. THE 850 MB TEMPS WILL CONTINUE TO FALL
WITH THE -12 DEGREE C 850 MB ISOTHERM DROPPING SEWD TO STL BY 12Z
FRI. LOW LEVEL CLOUD COVER ALONG WITH INTERMITTIENT FLURRIES
SHOULD CONTINUE AT LEAST THRU THU AND POSSIBLY INTO FRI ESPECIALLY
OVER THE NRN AND NERN PORTION OF THE CWA.

GKS

&&

.AVIATION...
/458 AM CST TUE DEC 1 2009/

FOR THE 12Z TAFS...

VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD. CLEAR SKIES WILL
GRADUALLY GIVE WAY TO SOME HIGH CLOUDS LATER TODAY AND ESPECIALLY
TONIGHT. SOUTH SOUTHWEST SFC WINDS WILL BE THE RULE TODAY WITH
SOME GUSTS ACROSS PORTIONS OF CENTRAL AND NE MO WHERE PRESSURE
GRADIENT IS A BIT TIGHTER. WINDS DIMINISH TONIGHT WITH COLD
FRONTAL PASSAGE ON WEDNESDAY MORNING. 

GLASS

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&

$$

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