Flash Flood Warning 10, NWS St. Louis, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
650 PM CDT MON MAR 17 2008

.DISCUSSION...
HAVE NOT MADE MUCH CHANGES TO GOING FORECAST WHICH HANDLES
IMPENDING EXCESSIVE RAINFALL EVENT WELL AND DO NOT PLAN ANY
CHANGES TO GOING WATCHES.

BUSY DAY SO FAR TODAY AS WIDESPREAD SHRA/TSRA DEVELOPED ON THE NOSE
OF A BROAD LOW LEVEL JET LATE LAST NIGHT AND CONTINUED INTO MOST
OF TODAY. MODELS ARE IN GENERAL AGREEMENT WITH THE WAY THIS SYSTEM
WILL EVOLVE THE NEXT TWO DAYS. CWA WILL LIE UNDER SUSTAINED STRONG
VERTICAL ASCENT THROUGH TOMORROW CAUSED BY NORTHERN STREAM
SHORTWAVE TROUGH PASSING TO THE NORTH AND POSITION OF THE RIGHT
ENTRANCE REGION OF THE GREAT LAKES JET. FIRST AREA OF SHRA/TSRA
NOW OVER WRN AND NRN MO WILL CONTINUE INTO THE EVENING OVER THE
NRN PART OF THE CWA. 925-850MB MOISTURE CONVERGENCE AND THETA-E
ADVECTION WILL THEN FOCUS FARTHER SOUTHEAST OVER THE CNTRL AND
SERN PARTS OF THE CWA TONIGHT. THE LOW LEVEL JET WILL BEGIN TO
CROSS THE SURFACE COLD FRONT THAT WILL MOVE SLOWLY SEWD ACROSS THE
CWA TOMORROW. THIS WILL ACT TO FURTHER INCREASE LOW LEVEL
CONVERGENCE OVER THE SOUTHEASTERN HALF OF THE CWA TOMORROW AS 60KT
LOW LEVEL JET TRANSPORTS HIGHLY ANOMOLOUS AMOUNTS OF MOISTURE
NORTHWARD INTO AREA. PRECIPITABLE WATER VALUES ARE EXPECTED TO BE
IN EXCESS OF 1.5 INCHES MAKING ANY TSRA HIGHLY EFFICIENT RAINFALL
PRODUCERS.

MODELS ARE NOW SLOWER WITH EJECTING THE SOUTHERN STREAM TROUGH
NORTHEASTWARD ACROSS THE MIDWEST TUESDAY NIGHT INTO WEDNESDAY
MORNING. THIS WILL CONTINUE THE STRONG ASCENT ALONG WITH THE GREAT
LAKES JET STREAK. HAVE UPPED POPS INTO WEDNESDAY MORNING OVER THE
SOUTHERN PART OF THE CWA TO ACCOUNT FOR THE SLOWER MOVEMENT OF THE
LOW.

THE GFS/NAM/ECWMF/SREF ALL HAVE THE HEAVIEST RAINFALL AXIS ACROSS
SRN MO INTO SRN IL INCLUDING THE FAR SRN CWA WITH LESSER AMOUNTS
DOWN TO AROUND AN INCH OVER THE FAR NRN PART OF THE CWA. DO THINK
THAT THE GFSS TOTAL OF >9 INCHES OVER THE SRN THREE COUNTIES IS
MOST LIKELY TOO HIGH BECAUSE OF NOTICEABLE GRIDSCALE FEEDBACK...
BUT CERTAINLY THINK THAT 5-7 INCHES OF TOTAL RAINFALL IS POSSIBLE
OVER THE SRN COUNTIES BY WEDNESDAY BECAUSE EVEN THE SREF IS
SHOWING THIS.

TEMPERATURES ARE A BLEND OF GFS MOS AND SREF MEAN.

CONFIDENCE IN THE EXTENDED PART OF THE FORECAST (THURSDAY NIGHT INTO
NEXT MONDAY) IS LOWER TODAY AS OPERATIONAL MODELS AND THEIR
ENSEMBLES HAVE BEEN SHOWING INCREASING RUN-TO-RUN CONTINUITY
PROBLEMS.  HAVE KEPT SLGT CHC OF SHRA IN FOR FRIDAY AS BOTH MODELS
INDICATE A WEAK SHORTWAVE TROUGH MOVING ACROSS MO/IL IN ZONAL FLOW.
LAST NIGHTS RUNS OF THE GFS/ECWMF DIGS A LESS AMPLIFIED/MORE
PROGRESSIVE TROUGH LATE IN THE WEEKEND INTO THE MIDWEST COMPARED
TO YESTERDAYS RUNS WHICH WAS DEEPER AND FARTHER TO THE WEST. WILL
STILL GO WITH CHC OF SHRA SATURDAY NIGHT AND SUNDAY AS THE TROUGH
PASSES THROUGH. TEMPERATURES ARE BASED MAINLY ON PERSISTENCE AND
HPC GUIDANCE.

BRITT

&&

.AVIATION...
FOR THE 00Z TAFS...
MAIN AREA OF PCPN ATTM EXTENDS FROM CENTRAL IL THRU NE MO INTO
CENTRAL MO THEN SWWD INTO SW MO AND NE OK. PCPN IS EXPECTED TO
GRADUALLY SHIFT EWD INTO THE STL AREA EARLY THIS EVENING. BULK OF
THE PCPN OVER THE LAST 3H IN THE TAF SITES HAS BEEN ALL RAIN BUT
THUNDER THREAT SHOULD ENTER THE PICTURE LATER THIS EVENING. AMOUNT
AND COVERAGE OF THUNDERSTORMS HAVE INCREASED QUICKLY ACROSS NE OK
AND SW MO SINCE 22Z AND THIS TREND SHOULD PERSIST AND EXPAND NEWD AS
LOW LEVEL FORCING INCREASES TONIGHT. RAIN AND THUNDERSTORMS SHOULD
IMPACT THE KCOU AND STL AREA TAFS WITH PRIMARILY MVFR CIGS. CIGS
WILL DROP INTO THE IFR RANGE UPON THE COLD FRONTAL PASSAGE LATE
TONIGHT INTO EARLY TUESDAY MORNING.

GLASS

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...FLOOD WATCH THROUGH LATE TUESDAY NIGHT FOR CRAWFORD-FRANKLIN-
     GASCONADE-JEFFERSON-LINCOLN-OSAGE-ST. CHARLES-ST. LOUIS-ST.
     LOUIS CITY-WARREN-WASHINGTON.

     FLOOD WATCH FROM 1 AM CDT TUESDAY THROUGH WEDNESDAY MORNING FOR
     IRON-MADISON-REYNOLDS-ST. FRANCOIS-STE. GENEVIEVE.

     FLOOD WATCH THROUGH TUESDAY EVENING FOR AUDRAIN-BOONE-CALLAWAY-
     COLE-KNOX-LEWIS-MARION-MONITEAU-MONROE-MONTGOMERY-PIKE-
     RALLS-SHELBY.

IL...FLOOD WATCH THROUGH LATE TUESDAY NIGHT FOR BOND IL-CALHOUN IL-
     GREENE IL-JERSEY IL-MACOUPIN IL-MADISON IL-MONROE IL-
     MONTGOMERY IL-ST. CLAIR IL.

     FLOOD WATCH FROM 1 AM CDT TUESDAY THROUGH WEDNESDAY MORNING FOR
     CLINTON IL-FAYETTE IL-MARION IL-RANDOLPH IL-WASHINGTON IL.

     FLOOD WATCH THROUGH TUESDAY EVENING FOR ADAMS IL-BROWN IL-PIKE
     IL.

&&

WFO LSX

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
344 PM CDT MON MAR 17 2008

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-181200-
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-
344 PM CDT MON MAR 17 2008

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

.DAY ONE...TONIGHT

THUNDERSTORMS...PRODUCING HEAVY RAINFALL...WILL CONTINUE TO MOVE
ACROSS MUCH OF THE FORECAST AREA TONIGHT. FLOODING ON LOCAL
STREAMS...CREEKS AND RIVERS ARE LIKELY. LOW LYING AREAS AND LOW
WATER CROSSINGS MAY ALSO EXPERIENCE FLASH FLOODING. SEE FLOOD
WATCH AND WARNING PRODUCTS FOR SPECIFIC DETAILS ON THIS FLOODING
EVENT.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SEVERAL ROUNDS OF RAIN AND THUNDERSTORMS TUESDAY AND TUESDAY NIGHT
ARE EXPECTED TO BRING 2 TO 4 INCHES OF RAINFALL TO THE AREA.
LOCALLY HIGHER AMOUNTS UP TO 7 INCHES WILL BE POSSIBLE ALONG AND
SOUTH OF INTERSTATE 44 IN MISSOURI AND INTERSTATE 70 IN ILLINOIS.

THIS HEAVY RAINFALL WILL LIKELY CAUSE SERIOUS FLOODING ON LOCAL
STREAMS...CREEKS AND RIVERS. LOW LYING AREAS AND LOW WATER
CROSSINGS MAY ALSO EXPERIENCE FLASH FLOODING. SEE FLOOD WATCH AND
WARNING PRODUCTS FOR SPECIFIC DETAILS ON THIS FLOODING EVENT.

STRONG THUNDERSTORMS ARE POSSIBLE AGAIN ON TUESDAY OVER SOUTHEAST
MISSOURI AND SOUTHWEST ILLINOIS. SOME OF THE STORMS COULD PRODUCE
SMALL HAIL AND GUSTY WINDS.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS AND LAW ENFORCEMENT ARE ASKED TO RELAY HEAVY RAINFALL AND
FLOODING REPORTS TO THE NATIONAL WEATHER SERVICE IN ST. LOUIS.

&&

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

CVKING