000 
FXUS63 KLSX 230221
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
821 PM CST THU NOV 22 2007

.UPDATE...

UPDATED FORECAST TO KEEP IT CLOUDY ALL NIGHT GIVEN SPEED OF BACK
EDGE OF CLOUDS ACROSS IOWA. THIS WILL KEEP LOWS UP A FEW MORE
DEGREES ACROSS THE WEST. ALSO THREW IN SOME FLURRIES FOR THIS
EVENING AS LIGHT RADAR RETURNS HAVE BEEN VERIFIED BY SPOTTERS.

CVKING

&&

.DISCUSSION...
PERSISTENT STRATUS/STRATOCUMULUS DECK HAS KEPT TEMPERATURES DOWN 
THIS AFTERNOON...AND WITH COLD ADVECTION CONTINUING TONIGHT...IT 
LOOKS LIKE FORECAST TEMPS IN THE LOW TO MID 20S ACROSS MOST OF THE 
CWFA WILL BE SPOT ON.  CLOUDS SHOULD STICK IN MOST AREAS THROUGH 
06Z...THEN CLEAR OUT FROM THE NORTHWEST ACROSS THE AREA THROUGH 
12-15Z FRIDAY.  COOL AND QUIET WEATHER SHOULD CONTINUE INTO THE 
WEEKEND...WITH HIGHER CLOUDS STREAMING INTO THE AREA ON SATURDAY AS 
A SHORTWAVE AND ASSOCIATED MID/UPPER LEVEL MOISTURE TRAVERSES THE 
MIDWEST.

SUNDAY INTO MONDAY IS STILL LOOKING PRETTY INTERESTING AS A 500MB 
CUTOFF LOW EJECTS FROM THE SOUTHWESTERN US INTO THE SOUTHERN PLAINS 
AND THE MID-MISSISSIPPI VALLEY.  THE GFS AND ECMWF HAVE COME INTO 
PRETTY DECENT AGREEMENT WITH THE HANDLING OF THIS SYSTEM...SPREADING 
A LARGE AREA OF QPF OUT AHEAD OF THE SYSTEM ACROSS SOUTHERN MISSOURI 
ON SUNDAY NIGHT AND OUT ACROSS MUCH OF THE REST OF THE AREA ON 
MONDAY.  I HAVE INCREASED POPS A BIT FOR THOSE PERIODS SINCE THE 
MODELS HAVE COME INTO BETTER ALIGNMENT...BUT THE 22/00Z GFS ENSEMBLE 
RUN STILL HOLDS THE STORM BACK A BIT IN THE SOUTHERN PLAINS...SO I 
HAVENT INCREASED TO LIKELY POPS YET.  WOULD LIKE TO LET THE NAM 
CHEW ON THIS SYSTEM FOR A CYCLE OR TWO BEFORE RAISING POPS INTO 
LIKELY CATEGORY.  THERMAL PROFILES ARE INDICATING THAT THE 
PRECIPITATION SHOULD BE ALL RAIN ACROSS THE CWFA...POSSIBLY ENDING 
AS SNOW LATE MONDAY AFTERNOON OR EVENING.  BUT WERE PRETTY CLOSE TO 
THE LINE.  WOULDNT BE SURPRISED TO SEE SUBSEQUENT MODEL RUNS 
FLIP-FLOP THE PRECIPITATION TYPE BETWEEN RAIN AND SNOW A FEW TIMES 
BEFORE THE STORM HITS.  KEPT PRECIP TYPE ALL RAIN FOR THIS PACKAGE 
SINCE THATS WHAT THE DATA INDICATES.

AFTER THE STORM EXITS THE REGION ON MONDAY NIGHT...TUESDAY AND 
WEDNESDAY LOOK TO BE DOMINATED BY ANOTHER COOL HIGH PRESSURE 
SYSTEM.  THE NEXT POTENTIAL STORM SYSTEM FOR THE MID-MISSISSIPPI 
VALLEY COULD AFFECT THE AREA AS EARLY AS THURSDAY...BUT MIDRANGE 
MODELS ARE DIFFERING ONCE AGAIN ON TIMING AND STRENGTH WITH THIS 
SECOND SYSTEM SO HAVE LEFT FORECAST DRY FOR NOW.

CARNEY

&&

.AVIATION...
FOR THE 00Z TAFS...PERSISTANT STRATUS AND STRATOCUMULUS CLOUDS
WILL NOT LIKELY CLR OUT TIL LT TGT OR EARLY FRI MRNG. WILL FCST AN
OVC030 CEILING THIS EVNG TO SCT OUT ARND 06Z FRI IN COU AND ARND
09Z FRI IN UIN...STL AND SUS. LATEST GFS MDL TIME HGT SECTION OF
RH DEPICTS DCRSG RH VALUES AFTER ABOUT 09Z FRI. CEILING MAY VARY
BTWN 2000-4000 FT...WITH A BRIEF PERIOD OF LGT SNOW OR FLURRIES
REDUCING VSBYS TO 5SM -SN POSSIBLE BUT WILL LEAVE TAFS DRY FOR
NOW AS ANY LGT SNOW SHOULD BE QUITE ISOLATED. NWLY SFC WNDS WILL BCM LGT
LT TGT AND FRI MRNG AS SFC HI CNTRD OVR NWRN KS MOVES EWD ACRS MO.

GKS

&&

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

$$

WFO LSX