River Flood Warning 275, NWS St. Louis, MO

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
528 AM CST THU DEC 24 2009

.DISCUSSION...
/405 AM CST THU DEC 24 2009/

TODAY THROUGH FRIDAY...PRIMARY CONCERNS ARE HEAVY RAIN
TODAY...COMPLEX STORM SYSTEM TONIGHT AND FRIDAY...AND LINGERING SNOW
SHOWERS FRI NIGHT THROUGH SUN.

TODAY...REGIONAL RADAR MOSAIC DEPICTED A CONTINUOUS RAIN SHIELD FM
MO/AR BORDER THROUGH AR INTO LA. PW VALUES ARE FCST TO CONTINUE
INCRSG THROUGH TONIGHT...REACHING 0.9 TO 1 INCHES OVER MOST OF THE
CWA AND EVEN HIGHER OVER SERN COUNTIES. THESE VALUES ARE AT LEAST 2
STANDARD DEVIATIONS ABOVE DECEMBER CLIMATOLOGY...THUS STILL EXPECT
MODERATE TO HEAVY RAINFALL TODAY GIVEN AMPLE MOISTURE AND INCREASING
SYNOPTIC LIFT FM APCHG STORM SYSTEM. WILL CONTINUE WITH GOING FLOOD
WATCH.

TONIGHT...PRIMARY FCST PROBLEM IS EVOLUTION OF SRN PLAINS STORM
SYSTEM. WATER VAPOR IMAGERY SHOWED FOUR DISTINCT PV ANOMALIES OF
INTEREST. THE TWO STRONGEST FEATURES WERE THE DIGGING SHORTWAVE
OVER WRN TX AND THE NRN SHORTWAVE DROPPING FM SASKATCHEWAN INTO
MT/WY. THE OTHER FEATURES WERE LOCATED OVER IA/NE/SD AND ERN TX.
TWO STRONGEST FEATURES ARE EXPECTED TO INTERACT /FUJIWHARA EFFECT/
AND MERGE WHILE LIFTING NWD INTO THE LOWER MSVLY. MODELS CONTINUE
TO TREND EWD WITH TRACK OF SFC LOW...WHICH HAS SIGNIFICANT IMPACTS
ON LOCATION OF THE HEAVY SNOW BAND. GIVEN MODEL DIFFICULTY IN
CAPTURING SWD EXTENT OF DIGGING OVER THE LAST FEW DAYS...CONCERNED
THAT MODELS HAVE BEEN SLOW TO CATCH ON TO INTENSITY OF SRN
SHORTWAVE AND COULD STILL BE TOO FAR W WITH SFC LOW TRACK.
GENERALLY FOLLOWED A GEM/NAM BLEND SINCE THE NAM BEST CAPTURED THE
INFLUENCE OF THE WEAKER SHORTWAVES AND THE GEM HAS BEEN
CONSISTENTLY CATCHING ON TO THE FARTHER EWD TRACK. WITH THAT IN
MIND...HAVE STARTED TRENDING THE FCST TOWARDS A MORE ERN SOLUTION
THAT BRINGS 2-4 INCHES OF ACCUMULATING SNOW TO FAR WRN COUNTIES.
RAIN WILL CHANGE TO SNOW BEHIND THE COLD FRONT AFTER MIDNIGHT BUT
A PERIOD OF SLEET IS POSSIBLE AS THE COLD AIR QUICKLY UNDERCUTS
WARMER LAYERS ALOFT. TIGHT PRESSURE GRADIENT WILL CREATE STRONG
GUSTY WINDS TONIGHT THROUGH FRI NIGHT. DUE TO THE COMBINATION OF
SLEET...WIND...AND SNOW...HAVE ISSUED A WINTER STORM WATCH FOR
CENTRAL AND NORTHEAST MISSOURI COUNTIES.

KANOFSKY

FRIDAY NIGHT THROUGH SUNDAY...
SPOKES OF VORTICITY COUPLED WITH STEEP LAPSE RATES WILL BRING
SCATTERED SNOW SHOWERS/SQUALLS TO THE AREA AS THE NEARLY STACKED LOW
PRESSURE SYSTEM PINWHEELS ACROSS IOWA. HAVE INCREASED POPS AND QPF
AS MODEL CONSENSUS AND PAST EXPERIENCE TELLS ME THAT ALTHOUGH NOT
EVERYONE WILL SEE ACCUMULATING SNOW FROM THESE SNOWBANDS...THOSE
THAT DO WILL LIKELY HAVE A FEW INCHES TO CONTEND WITH. COUPLE THE
LIGHT SNOW ACCUMULATION WITH THE BRISK WIND AND WINTER ADVISORY TYPE
CONDITIONS MAY BE REALIZED AT TIMES THIS HOLIDAY WEEKEND.

CVKING

&&

.AVIATION...
/526 AM CST THU DEC 24 2009/

FOR THE 12Z TAFS...
IFR CEILINGS TO CONTINUE AS STORM SYSTEM WRAPS UP OVER THE TOP OF
THE CWA. SHOWERS AND EVEN SOME RUMBLES OF THUNDER WILL SPREAD
NORTH TODAY AND CONTINUE INTO THIS EVENING. AS COLD AIR FILTERS
BEHIND THE LOW...THE RAIN WILL TURN TO SNOW AT KCOU AROUND
06Z...AND ST. LOUIS METRO TAFS AROUND 12Z. WIND TO GO FROM
EAST/SOUTHEAST TO WEST/NORTHWEST...WITH GUSTS GREATER THAN 25 KTS
POSSIBLE.

CVKING

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...FLOOD WATCH THROUGH THIS 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.

     WINTER STORM WATCH FROM LATE TONIGHT THROUGH FRIDAY AFTERNOON
     FOR AUDRAIN-BOONE-CALLAWAY-COLE-KNOX-LEWIS-MARION-MONITEAU-
     MONROE-OSAGE-RALLS-SHELBY.

IL...FLOOD WATCH THROUGH THIS 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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
432 AM CST THU DEC 24 2009

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-251200-
GREENE IL-MACOUPIN IL-MONTGOMERY IL-BOND IL-FAYETTE IL-CLINTON IL-
MARION IL-WASHINGTON IL-RANDOLPH IL-ADAMS IL-BROWN IL-PIKE IL-
CALHOUN IL-JERSEY IL-MADISON IL-ST. CLAIR IL-MONROE IL-KNOX-LEWIS-
SHELBY-MARION-MONROE-RALLS-PIKE-BOONE-AUDRAIN-MONITEAU-COLE-OSAGE-
CALLAWAY-MONTGOMERY-LINCOLN-GASCONADE-WARREN-ST. CHARLES-FRANKLIN-
ST. LOUIS-ST. LOUIS CITY-JEFFERSON-CRAWFORD-WASHINGTON-
ST. FRANCOIS-STE. GENEVIEVE-IRON-MADISON-REYNOLDS-
432 AM CST THU DEC 24 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EASTERN AND
CENTRAL MISSOURI AS WELL AS WEST CENTRAL AND SOUTHWEST ILLINOIS.

.DAY ONE...TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL BRING MODERATE TO HEAVY
RAINFALL TO PARTS OF MISSOURI AND ILLINOIS TODAY. ADDITIONAL
RAINFALL MAY CAUSE FLOODING AS IT FALLS ON GROUND THAT IS ALREADY
SATURATED OR STILL FROZEN. FOR MORE INFORMATION...PLEASE SEE THE
FLOOD WATCH.

A STRONG STORM SYSTEM WILL BRING 2 TO 4 INCHES OF SNOWFALL TO
PARTS OF CENTRAL AND NORTHEASTERN MISSOURI LATE TONIGHT AND EARLY
FRIDAY. A BRIEF PERIOD OF SLEET IS POSSIBLE AS THE RAIN CHANGES
OVER TO SNOW. THE SYSTEM WILL ALSO PRODUCE SUSTAINED WINDS OF
15 TO 25 MPH WITH GUSTS UP TO 35 MPH POSSIBLE ACROSS THE BISTATE
REGION.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

STRONG GUSTY WINDS WILL PERSIST THROUGH FRIDAY NIGHT BEFORE
DIMINISHING ON SATURDAY. SUSTAINED WINDS OF APPROXIMATELY 20 MPH
ARE EXPECTED WITH GUSTS UP TO 30 MPH POSSIBLE.

THERE IS A CHANCE OF SNOW SHOWERS ON FRIDAY AND SATURDAY. AN
ADDITIONAL 1 TO 2 INCHES OF SNOW IS POSSIBLE ACROSS PARTS OF
MISSOURI AND ILLINOIS.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE ASKED TO REPORT PRECIPITATION AMOUNTS AND ANY
FLOODING TO THE NATIONAL WEATHER SERVICE.

&&

FOR A GRAPHICAL VERSION OF THIS INFORMATION SEE OUR
WEBPAGE AT (LOWERCASE)... HTTP://WWW.WEATHER.GOV/LSX/?N=HWO1

KANOFSKY

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