FXUS63 KLSX 232123
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
323 PM CST WED DEC 23 2009
.DISCUSSION...
/318 PM CST WED DEC 23 2009/
LOTS OF QUESTIONS WITH THIS FORECAST INCLUDES THE THREAT OF
FLOODING...ACCUMULATING SNOWFALL AND GUSTY WINDS. HAVE FOLLOWED
ALONG WITH A BLEND OF THE LATEST ECMWF/NAM GUIDANCE WHICH FALL IN
THE MIDDLE OF THE OTHER GUIDANCE. GFS SUFFERS FROM CONVECTIVE
FEEDBACK THE NEXT FEW DAYS WHICH IS REFLECTED IN IT'S QPF FIELDS.
IT ALSO HAS TROUBLE PHASING THE TWO UPPER LOWS BY FRIDAY NIGHT.
THE CANADIAN GEM IS ON THE EASTERN SIDE OF THE MODEL SUITE WITH THE
TRACK OF THE UPPER LOW...THOUGH NOT AS FAR EAST AS IT DID ON THE
00Z RUN.
REGARDING THE FLOODING POTENTIAL...SEVERAL LOCATIONS IN CENTRAL
MISSOURI AND SOUTH CENTRAL ILLINOIS HAVE ALREADY SEEN 1 TO 2 INCHES
OF RAINFALL. FLOOD WATCH HAS ALREADY BEEN EXPANDED TO INCLUDE THE
REMAINING CENTRAL MO COUNTIES AND WILL BE EXTENDED THROUGH TOMORROW
EVENING. ADDITONAL SHRA/TSRA HAVE DEVELOPED TO THE SOUTHWEST AND
WILL BE MOVING INTO THE REGION THIS EVENING. MODELS STILL SHOW
IMPRESSIVE FORCING AND UNSEASONABLY HIGH PWATS ADVECTING INTO THE
AREA THROUGH TOMORROW EVENING. ADDITIONAL RAINFALL IS EXPECTED TO
RANGE FROM 1.5-2" OVER CNTRL/NERN MO TO OVER 2.5" IN SERN MO/S CNTRL
ILLINOIS WHERE THE LOW LEVEL FORCING WILL BE MORE FOCUSED.
WINDS WILL CERTAINLY PICK UP IN THE WARM SECTOR TOMORROW...WITH
SUSTAINED WINDS IN THE 15 TO 30 MPH RANGE3 WITH SOME HIGHER
GUSTS. NOT QUITE ENOUGH TO REQUIRE AN ADVISORY SO WILL HIT THE
WORDING HARD IN THE HWO. COLD FRONT WILL MOVE ACROSS THE CWA FROM
WEST TO EAST ON THURSDAY EVENING AND PRESSURE GRADIENT BEHIND
FROPA WILL REMAIN TIGHT THROUGH FRIDAY NIGHT IN THE COLD AIR
ADVECTION.
WINTER WISE...RAIN WILL CHANGE TO SNOW FROM WEST TO EAST AS THE
FRONT PASSES THROUGH TOMORROW NIGHT. THE BEST MID LEVEL FORCING AND
850 MB LOW TRACK CONTINUE TO SUGGEST THAT THERE WILL BE A TIGHT
GRADIENT OF SNOWFALL OVER CENTRAL MO. LOOKS LIKE ADVISORY CRITERIA
SNOW WILL STAY JUST WEST OF THE CWA DURING THIS PERIOD. MAY STILL
SEE 1-2 INCHES TOMORROW NIGHT INTO FRIDAY ON THE EASTERN EDGE OF
THE DEFORMATION ZONE. STILL LOOKS LIKE A DECENT SET UP FOR SNOW
SHOWERS FRIDAY INTO SATURDAY TO THE NORTH OF I-70 CONSIDERING THE
STEEP LAPSE RATES IN THE LOW LEVELS IN ADDITION TO THE ABUDANT
MOISTURE AND CYCLONIC CURVATURE.
HAVEN'T CHANGED THE FORECAST MUCH EARLY NEXT WEEK AS I EXPECT THERE
STILL WILL BE LINGERING SNOW SHOWERS OR FLURRIES AS UPPER LOW
REMAINS IN RELATIVELY CLOSE PROXIMITY TO US THROUGH SUNDAY NIGHT
BEFORE IT LIFTS NEWD. RIDGING THEN BUILDS IN PROVIDING DRY WEATHER
FOR AT LEAST MONDAY AND TUESDAY. BOTH THE ECMWF/GEFS MEAN ARE
SHOWING ANOTHER TROUGH REACHING THE MIDWEST BY WEDNESDAY...BUT
LACK OF DECENT MODEL CONTINUITY AND BLOCKINESS OF THE UPPER
PATTERN OVER THE WEEKEND TELLS ME TO KEEP FORECAST DRY FOR NOW.
BRITT
&&
.AVIATION...
/1145 AM CST WED DEC 23 2009/
FOR THE 18Z TAFS...
KSTL/KSUS...VSBYS AND CIGS HAVE IMPROVED TO MVFR AT SURROUNDING
OB SITES...HAVE PREVAILED SUCH CONDITIONS THRU 3Z WITH TEMPO IFR
FOR THE NEAR-TERM. COMPLEX FCST AS ANOTHER SFC LOW WILL DEEPEN
ACRS ERN TX AND LIFT NWD THRU THE MID-MS VLY. PRESENTLY SFC BNDRY
IS DRAPED ACRS CENTRAL MO THRU SRN IL...JUST SOUTH OF KSUS/KSTL.
AS THE SECOND SFC LOW LIFTS NWD WILL FIND THE REGION IN THE WARM
SECTOR WITH INCREASING SLY WINDS GUSTING AT TIMES WITH PREVAILING
IFR CONDITIONS. WE SHALL SEE THE ADVECTION OF A VERY MOIST AND
SLIGHTLY UNSTABLE AIRMASS ACRS THE TAF LOCALES RESULTING IN HEAVY
RAINS AND SCATTERED TSRA. WITH AFORMENTIONED CONDITIONS HAVE GONE
VCTS FOR NOW AND DO NOT EXPECT LIFR.
KCOU...SFC FRONTAL BNDRY JUST SOUTH BEHIND WHICH MVFR CONDITIONS
EXIST. HAVE PREVAILED MVFR WITH TEMPO IN THE NEAR-TERM FOR IFR-
LIFR IN ASSOCIATED WITH THE PRESENT HEAVY RAIN BAND PER RADAR
RETURNS. EXPECT THIS PRECIP TO ADVECT EWD...WILL NEED TO MONITOR
PSBL CONVECTIVE WEATHER IMPACTS TO THE EAST. WITH SFC LOW LIFTING NWD
AS WITH KSTL/KSUS EXPECT HEAVY RAINS AND SCATTERED TSRA THRU FCST
AREA. HAVE FOLLOWED THRU WITH IFR CONDITIONS AND VCTS AFTER 3Z
IMPROVING SLIGHTLY INTO 13Z WITH INCREASING SLY WINDS.
KUIN...LIFR CONDITIONS TO PREVAIL OVER THE NEXT SEVERAL HOURS AS
FCST AREA IS WELL NORTH OF THE STATIONARY BNDRY TO THE SOUTH AND
ENCOMPASSED IN A MUCH COOLER AIR MASS. DO NOT EXPECT CONDITIONS TO
IMPROVE UNTIL THE SECONDARY LOW TRACKS NWD WITH ASSOCIATED WARM
SECTOR AND STRONG SLY WINDS BY 14Z.
SIPPRELL
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...FLOOD WATCH THROUGH THURSDAY EVENING FOR AUDRAIN-BOONE-CALLAWAY-
COLE-CRAWFORD-FRANKLIN-GASCONADE-IRON-JEFFERSON-KNOX-LEWIS-
LINCOLN-MADISON-MARION-MONITEAU-MONROE-MONTGOMERY-OSAGE-
PIKE-RALLS-REYNOLDS-SHELBY-ST. CHARLES-ST. FRANCOIS-ST.
LOUIS-ST. LOUIS CITY-STE. GENEVIEVE-WARREN-WASHINGTON.
IL...FLOOD WATCH THROUGH THURSDAY EVENING FOR ADAMS IL-BOND IL-BROWN
IL-CALHOUN IL-CLINTON IL-FAYETTE IL-GREENE IL-JERSEY IL-
MACOUPIN IL-MADISON IL-MARION IL-MONROE IL-MONTGOMERY IL-
PIKE IL-RANDOLPH IL-ST. CLAIR IL-WASHINGTON IL.
&&
$$
WFO LSX
