124
FXUS63 KLSX 011040
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
440 AM CST FRI FEB 1 2008
DISCUSSION
..WINTER STORM WILL BE WINDING DOWN THIS MORNING
WELL IT TOOK AWHILE BUT WE FINALLY GOT THE HEAVY SNOW. THIS
SYSTEM WAS IN ITS INFANCY MUCH OF THE YESTERDAY AND INTO THE EARLY
EVENING...THEN DURING THE LATER HALF OF THE EVENING IT BEGAN TO
STRENGTHEN AND MATURE AND EVERYTHING CHANGE. A STOUT DEFORMATION ZONE
DEVELOPED RIGHT OVER ERN MO AND WRN IL THRU THE ST LOUIS AREA DURING
THE LATER HALF OF THE EVENING IN RESPONSE TO STRONG LARGE SCALE
ASCENT AND MID LEVEL FRONTOGENETIC FORCING ASSOCIATED WITH THE
CYCLONIC BRANCH OF THE WARM CONVEYOR BELT/TROWAL. IN THE PRESENCE
OF RELATIVELY STEEP MID LEVEL LAPSE RATES THIS FORCING LEAD TO
SOME IMPRESSIVE BANDING WITH HIGH SNOWFALL RATES AND EVEN SOME
THUNDER IN CENTRAL IL. THE COOLING CLOUD TOPS...RAPIDLY EXPANDING
AND FILLING ECHO...AND RADAR REFLECTIVIES WERE CLASSIC. BETWEEN
1145 PM AND 110 AM WE HAD 3.6 INCHES OF SNOW HERE IN WELDON SPRING
AT THE WFO...AND THIS WAS WITH FLAKES THAT WERE NEVER LARGER THAN
A DIME...BUT WERE AS DENSE AS YOU'LL SEE.
THE SYSTEM IS QUITE MATURE NOW AND IS PULLING EASTWARD INTO THE OH
VLY WITH THE MID LEVEL LOW CENTERED IN SOUTH CENTRAL IL. THERE
CONTINUES TO BE A NARROW BUT IMPRESSIVE NORTH-SOUTH BAND FROM
AROUND CARLINVILLE TO BELLEVILLE...WITH THE BACK EDGE OF THE SNOW
AROUND 50 MILES WEST OF ST LOUIS. THE ILLINOIS COUNTIES EAST OF
THE AFOREMENTIONED BAND WILL PROBABLY SEE ANOTHER 2-3+ INCHES...WITH
AROUND 1-1.5 OF THESE COMING AFTER 12Z. LITTLE ADDITIONAL ACCUMULATION
IS EXPECTED WEST OF THE MS RVR. I THINK STORM TOTALS OF 7-9 INCHES
WILL BE FAIRLY COMMON AMOUNTS FROM STL AREA NORTH AND EAST. THE
HEADLINES ACROSS CENTRAL AND NE MO AND WEST CENTRAL IL HAVE BEEN
DROPPED WITH THIS FCST ISSUANCE WHILE FROM ST LOUIS EASTWARD THEY
HAVE BEEN CONTINUED FOR THE ADDITIONAL ACCUMS AND SNOW BLOWING
SNOW IN THE WAKE OF THE SFC LOW. ALL SNOW SHOULD BE OVER BY
17-18Z.
IN THE WAKE OF THIS STORM SYSTEM A PATTERN CHANGE WILL TAKE PLACE
WHICH WILL BRING SWLY FLOW ALOFT AND A MODERATING TEMPERATURE
TREND. THE MODERATION OF TEMPERATURES WILL BE HAMPERED BY THE
FRESH SNOW COVER AND IN GENERAL I HAVE UNDERCUT THE GUIDANCE
NEARLY EVER PERIOD FROM ERN MO INTO IL. A WEAK FRONT WILL DROP INTO
THE AREA ON SATURDAY WITH LITTLE FANFARE AND THEN A NEW SYSTEM
ACCOMPANIED BY STRONG WAA AND MOISTURE WILL BRING A CHANCE OF
RAIN TO THE AREA FROM SUNDAY INTO THE FIRST PART OF NEXT WEEK. THE
00Z GFS IS TRYING TO DEVELOP SOME WINTRY PRECIPITATION TUES
AFTERNOON INTO TUESDAY NIGHT ACROSS PORTIONS OF THE AREA. THIS IS
IN RESPONSE TO A LOW IT DEVELOPS ALONG THE WRN PORTION OF THE
FRONT IN OK AND THEN DEEPENS AS IT MOVES NORTHEAST INTO THE OH
VLY. THIS SOLUTION IS AN OUTLIER ATTM COMPARED TO THE GFS ENSEMBLE
MEAN...CMC GEM...AND ECMWF AND THUS IS SUSPECT. I HAVE ADDED SOME
LOW POPS AT THIS POINT AND WE WILL CONTINUE TO WATCH TRENDS IN
LATER MODEL RUNS.
GLASS
AVIATION
FOR THE 12Z TAFS...BACK EDGE OF THE SNOW SHIELD ROTATING THRU THE
STL METRO AREA ATTM. THE SNOW SHOULD BE TAPERING OFF TO FLURRIES
IN STL AND SUS SHORTLY AFTER 12Z THIS MRNG AS THE MID LVL LOW
CURRENTLY OVR SRN IL AND ASSOCIATED SFC LOW OVR SWRN IN CONTS TO
MOVE NEWD. SFC WNDS WILL BACK ARND TO A W-NWLY DIRECTION AS THE
SFC LOW MOVES NEWD THRU THE OH VLY REGION LTR THIS MRNG. THE SFC
WND SHOULD WKN FRI AFTN AS THE SFC LOW PULLS WELL NE OF THE CWA
AND A WK SFC RDG MOVES EWD THRU THE CWA. THE CLOUD CEILING WILL
GRADUALLY RISE THRU THE LT MRNG HRS AND EVENTUALLY SCT OUT FM W
TO E DURING THE LT MRNG AND AFTN HRS. THE SFC WND WL BCM S-SELY
TGT AS THE SFC RDG MOVES E OF THE CWA WITH JUST SOME HI LVL CLOUDS
TGT.
GKS
LSX WATCHES/WARNINGS/ADVISORIES
MO...WINTER STORM WARNING UNTIL 9 AM CST THIS MORNING FOR JEFFERSON-
ST. CHARLES-ST. LOUIS-ST. LOUIS CITY.
IL...WINTER STORM WARNING UNTIL NOON CST TODAY FOR BOND IL-FAYETTE IL-
GREENE IL-MACOUPIN IL-MARION IL-MONTGOMERY IL.
WINTER STORM WARNING UNTIL 9 AM CST THIS MORNING FOR CALHOUN IL-
CLINTON IL-JERSEY IL-MADISON IL-MONROE IL-ST. CLAIR IL-
WASHINGTON IL.
WFO LSX
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