FXUS63 KLSX 301147
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
547 AM CST MON NOV 30 2009

.DISCUSSION...
/358 AM CST MON NOV 30 2009/

STUBBORN LOW LEVEL CLOUDINESS ACROSS THE CWA SHOULD FINALLY ADVECT
E OF THE CWA THIS MRNG WITH A SUNNY SKY THIS AFTN AS THE SFC RDG
OVER THE PLAINS BUILDS EWD INTO THE CWA. ALTHOUGH 850 MB TEMPS
WILL BE QUITE LOW ACROSS THE CWA...FROM -3 TO -1 DEGREES C AT 18Z
MON...FULL SUNSHINE THIS AFTN SHOULD SEND TEMPS TO AROUND SEASONAL
NORMALS. LITTLE CLOUDINESS SHOULD CONTINUE THROUGH TUE...MAYBE
SOME CIRRUS BY TUE AFTN. WENT ABOVE PERSISTENCE AND ALSO ABOVE MOS
GUIDANCE FOR MAX TEMPS ON TUE WITH RISING MID-UPR LEVEL HEIGHTS
AND SWLY LOW LEVEL WINDS. 850 MB TEMPS WILL CONTINUE TO RISE THRU
TUE...ALTHOUGH THEY WILL NOT GET AS WARM AS LAST SATURDAY.
INCREASING CLOUDINESS CAN BE EXPECTED TUE NGT AS TWO WEATHER
SYSTEMS APPROACH THE AREA. A MID-UPPER LEVEL LOW WILL BE MOVING
EWD THRU THE NRN PLAINS WHICH WILL SEND A CDFNT SEWD THRU THE CWA
LATE TUE NGT AND WED. AT THE SAME TIME THE MID-UPPER LEVEL LOW
CURRENTLY OVER MEXICO WILL BE MOVING EWD THRU TX AND EVENTUALLY
NEWD THRU AR WED AFTN AND THRU WRN PORTIONS OF KY TN WED NGT AS IT
GETS PICKED UP BY THE MID-UPR LEVEL TROF CENTERED OVER THE
NRN PLAINS. THE NAM MODEL HAS BEEN GENERATING SOME QPF ALONG AND
JUST BEHIND THE CDFNT DUE TO FRONTOGENETICAL FORCING ON WED...BUT
MORE SIGNIFICANT WILL BE THE PRECIPITATION SHIELD ASSOCIATED WITH
THE SRN MID-UPPER LEVEL LOW AND ASSOCIATED SFC LOW WHICH WILL BE
MOVING NEWD THRU AR AND WRN PORTIONS OF KY TN...ALTHOUGH THE
MODELS HAVE BEEN FORECASTING VARYING TRACKS OF THESE FEATURES.
DISCOUNTED THE GFS AS IT APPEARS TOO FAST WITH THE SFC/850 MB LOW
WED AFTN INTO EVNG. THE NAM...ECMWF AND CANADIAN GEM MODELS ARE
FAIRLY SIMILAR WITH THE UPPER/SFC LOW POSITION...TIMING AND THE
PRECIPITATION SHIELD WHICH MAINLY COVERS THE SRN PORTION OF THE
CWA WED MRNG AND THE SERN HALF OF THE CWA WED AFTN AND EVNG.
LATEST MODEL RUNS HAVE BEEN TRENDING TO A MORE NWLY TRACK WHICH
WILL GIVE THE SRN AND ERN PTN OF THE CWA MORE PCPN WED AND WED
NGT. WILL COLDER AIR FILTERING SEWD THRU THE CWA ON WED BEHIND THE
CDFNT THE TEMPERATURES WILL LIKELY FALL DURING THE AFTN HOURS ACROSS
MOST OF THE CWA. LOOKING AT MODEL FORECAST SOUNDINGS RAIN WILL
CHANGE OVER TO SNOW IN STL AREA BY LATE AFTN...IN FAM BY LATE AFTN
OR EARLY EVNG AND IN SLO WED EVNG. WITH WARM GROUND...SURFACE
TEMPS ABOVE FREEZING OVER THE SERN HALF OF THE CWA TIL LATE WED
NGT SNOW WILL HAVE TROUBLE ACCUMULATING UNLESS SNOWFALL RATES ARE
QUITE HIGH. A LOT OF UNCERTAINTY WITH THE TRACK OF THIS STORM
SYSTEM AND THE TIMING OF THE CHANGE OVER TO SNOW...BUT IT APREARS
THAT THERE MAY BE AT LEAST LIGHT ACCUMULATIONS FROM STL S AND
E...WITH BEST POTENTIAL FROM AROUND FAM TO SLO WED EVNG. THE SNOW
SHOULD TAPER OFF TO FLURRIES LATE WED NGT WITH CLOUDINESS AND
FLURRIES LINGERING INTO THU WITH THE LARGE AND DEEP MID-UPPER
LEVEL LOW CENTERED OVER THE NRN PLAINS AND GREAT LAKES REGION. THE
COLDEST TEMPS OF THIS FALL SEASON SO FAR ARE LIKELY ON THU AND
THU NGT WITH 850 MB TEMPS DROPPING TO -10 TO -12 DEGREES C BY 18Z
THU.

GKS

&&

.AVIATION...
/539 AM CST MON NOV 30 2009/

FOR THE 12Z TAFS...

LOW LEVEL CYCLONIC FLOW PERSISTS ACROSS THE AREA ATTM WITH OVC
CIGS AT 3-4 KFT GENERALLY PREVAILING...ALTHO SOME HOLES HAVE BEGUN
TO OPEN ACROSS NE MO. THE BACK EDGE OF CLOUDS APPEARS TO BE JUST
WEST OF A KIRK-KCOU LINE AND IS SHOWING A EASTWARD CLEARING TREND
IN SATELLITE IMAGERY. EXTRAPOLATION WOULD PLACE CLEARING LINE THRU
KUIN-KSTL AXIS AT 16-17Z ALTHO IT COULD OCCUR SOONER GIVEN THE
AFOREMENTIONED BREAKS. CLEAR SKIES EXPECTED TO DOMINATE THEREAFTER.
NWLY SFC WINDS WILL BE BACKING TO SWLY DURING THE AFTERNOON AS THE
PLAINS RIDGE SINKS TO THE SOUTH.

GLASS

&&

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

$$

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