FXUS63 KLSX 120048
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
648 PM CST FRI DEC 11 2009

.UPDATE...
/625 PM CST FRI DEC 11 2009/

VFR CLOUD DECK OVER SW/S CNTRL MO CONTINUES EXPANDING NE AT A
DECENT CLIP. THIS MOISTURE IS BEING HANDLED VERY POORLY BY MOST OF
THE MODELS....ALTHOUGH THE LATEST RUC 850-700RH FIELD DOES SEEM TO
BE CATCHING ON. HAVE UPDATED SKY CONDITIONS FOR TONIGHT BASED ON
EXTRAPOLATION IN THE NEAR TERM...AND THEN WITH THE CLOUD TREND
SUGGESTED BY THE RUC THAT THESE CLOUDS MAY THIN A BIT DURING THE
PREDAWN HOURS. A DEEPER AND THICKER CLOUD COVER SHOULD THEN EXPAND N
DURING THE DAY SAT. DID NOT MAKE ANY CHANGES TO MIN TEMPS YET...AS
RATHER LIGHT WINDS AND LOW DEWPOINTS MAY ALLOW A PRETTY GOOD DROP
OFF IN TEMPS OVER S AREAS BEFORE THE CLOUDS ARRIVE...OR LATER
TONIGHT IF THE CLOUDS DO THIN.

TRUETT

&&

.DISCUSSION...
/413 PM CST FRI DEC 11 2009/

TONIGHT THROUGH SUN...1032MB SFC HIGH WAS CENTERED OVER THE TN 
VALLEY AT 21Z YIELDING SWLY WINDS ACROSS THE BISTATE REGION UNDER 
NEARLY ZONAL FLOW ALOFT. AS THE HIGH MOVES EWD...CONTINUED S TO SW 
WINDS WILL LEAD TO MODERATING TEMPERATURES OVER THE WEEKEND WITH THE 
WARMEST TEMPS EXPECTED ON SUN AS H85 TEMPS CLIMB TO 8-10 DEG C. NEXT 
SHORTWAVE TROF MOVES ACROSS THE BISTATE REGION ON SAT WITH SLY WINDS 
DRAWING WARMER AND MOISTER AIR NWD AHEAD OF ITS ARRIVAL. MAINTAINED 
SCHC-CHC POPS FOR SAT AFTN THROUGH SAT NIGHT BASED ON TIMING OF UL 
ASCENT.

MON THROUGH FRI...NEXT SYS TO AFFECT THE REGION ORGANIZES OVER THE 
PLAINS ON SUN NIGHT/MON WITH REASONABLE MODEL AGREEMENT ON THE SFC 
LOW TRACKING THROUGH NWRN MO ON MON. THIS SYS DRIVES A CDFNT THROUGH 
THE BISTATE REGION ON MON INTO MON NIGHT WITH MUCH COLDER AIR BEHIND 
THE FNT. CONTINUED SILENT SCHC POPS AS MOISTURE APPEARS LIMITED WITH 
THIS SYS. HIGH PRES SLIDES SEWD FM THE NRN PLAINS AND SETTLES OVERHEAD 
FOR TUE NIGHT. WITH GFS/EC/GEM NOW IN BETTER AGREEMENT ON SWD EXTENT 
OF COLD AIR...HAVE LOWERED TEMPS A FEW DEGREES ON MON NIGHT AND TUE 
TO TREND TOWARDS THE COLDER SOLN.

KANOFSKY

&&

.AVIATION...
/541 PM CST FRI DEC 11 2009/

FOR THE 00Z TAFS...SFC RDG CENTERED OVER NERN TN WITH RELATIVELY
LGT S-SELY SFC WNDS AT THE TAF SITES ON THE NWRN PERIPHERY OF THE
SFC RDG. SFC WNDS SHOULD PICK UP TO AROUND 10 KTS BY LATE MRNG ON
SAT. LOW-MID LEVEL CLOUDINESS...5000-6500 FT ADVECTING E-NEWD THRU
SWRN MO ATTM. MODELS DO NOT SEEM TO HAVE A GOOD HANDLE ON THIS
CLOUD COVER AND HENCE THERE IS UNCERTAINTY WITH HOW FAR N AND E THIS
CLOUD COVER WILL GET TGT. USING SATELLITE EXTRAPOLATION DID BRING
BKN060 CLOUDS INTO COU AT 04Z SAT...AND BKN070 INTO STL/SUS AT 07Z
SAT. MODELS DO BRING LOW LEVEL MOISTURE NEWD THRU THE TAF SITES ON
SAT SO WILL LOWER CEILINGS A TAD IN STL...SUS AND COU LATE SAT
MRNG AND INTRODUCE A VFR LOW LEVEL CEILING INTO UIN. DID NOT DROP
THE CEILING INTO THE MVFR CATAGORY UNTIL 21Z SAT IN COU AND 00Z
SUN IN STL. LIGHT RAIN SHOULD ALSO BE MOVING THROUGH THE CWA MAINLY
SAT EVNG WITH LOW-MID LEVEL WAA AHEAD OF AN APPROACHING SHRTWV
TROF. IT WILL TAKE THE BOUNDARY LAYER A LITTLE WHILE TO SATURATE
BUT THERE SHOULD AT LEAST BE PATCHY LIGHT RAIN ACROSS THE AREA SAT
EVNG. DID INCLUDE A PROB30 GROUP OF 6SM -RA IN STL FROM 00Z TO 06Z
SUN.

GKS

&&

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

$$

WFO LSX