Severe Thunderstorm Warning 14, NWS St. Louis, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
445 AM CDT TUE MAY 18 2004

.DISCUSSION...
SLOW MOVING COLD FRONT STRETCHING FROM NORTH CENTRAL KANSAS THROUGH
EXTREME NORTHWESTERN MISSOURI INTO SOUTHERN IOWA.  IT SEEMS THAT THE
ON-GOING CONVECTION ALONG IT IS WHAT IS KEEPING IT DRIFTING
SOUTHWARD...THE ONLY THING KEEPING IT FROM REVERSING COURSE AND
HEADING BACK INTO THE NORTHERN PLAINS AS A WARM FRONT.  SPEAKING OF
THAT CONVECTION...IT LOOKS LIKE SOUTHEAST NEBRASKA AND NORTHWEST
MISSOURI IS GETTING DRENCHED THIS MORNING.  THE CONVECTION IS HAVING
A DIFFICULT TIME HEADING EASTWARD INTO NORTH CENTRAL AND NORTHEAST
MISSOURI WITH ANY KIND OF STRENGTH THOUGH DUE (I THINK) TO SOME
DRYING AT MID LEVELS AND A WEAK MID-LEVEL INVERSION.  THE INVERSION
IS ALREADY WASHING OUT ACCORDING TO THE MESOETA SOUNDINGS...AS IS
THE DRYING.  RADAR TRENDS OVER THE LAST HOUR SHOW THE EAST/WEST LINE
JUST SOUTH OF THE MO/IA BORDER FINALLY GETTING A MOVE ON EASTWARD
INTO NORTH CENTRAL MISSOURI.  ADDITIONALLY THERE SEEMS TO BE SOME
DEVELOPMENT JUST TO THE SOUTHEAST OF THE MAIN LINE...AS WELL AS A
FEW WEAK/TRANSIENT SHOWERS TRYING TO POP UP ACROSS NORTHERN PORTIONS
OF MY CWFA.  THIS IS ENCOURAGING FOR LIKELY POPS THIS MORNING IN
ABOUT THE NORTHERN 1/3 OF MY CWFA...AND FEEL THAT WITH DAYTIME
HEATING...LITTLE TO NO CAP ACROSS ABOUT THE NORTHERN 2/3 OF MY
CWFA...AND OUTFLOW BOUNDARIES GALORE FLOATING AROUND LATE THIS
MORNING AND THIS AFTERNOON...WE SHOULD SEE ADDITIONAL DEVELOPMENT SO
LIKELY POPS IN THE AFORE MENTIONED NORTHERN 2/3S OF MY AREA.  06Z
RUN OF THE MESOETA EVEN PULLS THE PRECIP AS FAR SOUTH AS REYNOLDS
COUNTY TODAY...AND THE SHORT TERM DAY SHIFT SHOULD MONITOR THIS AREA
CLOSELY TODAY IN CASE AN UPDATE IS REQUIRED...

WILL EXPECT TO SEE CONVECTION CONTINUING THIS EVENING AND OVERNIGHT
TONIGHT ESPECIALLY INVOF THE SURFACE BOUNDARY...WHICH BECOMES
INCREASINGLY DIFFICULT TO REALLY NAIL DOWN AS THE CONVECTION WORKS
THE ATMOSPHERE OVER.  WE SHOULD BE ON THE NOSE OF THE LOW LEVEL JET
AND BOTH THE ETA AND GFS SHOW A FAIR AMOUNT OF LOW LEVEL MOISTURE
CONVERGENCE AND FRONTAL SCALE FORCING OVER OUR AREA.  CONTINUED THE
LIKELY POPS GENERALLY ALONG AND NORTH OF THE MISSOURI RIVER BECAUSE
OF THIS.  WENT WITH MID TO HIGH CHANCE POPS FURTHER SOUTH.  I AM
SOMEWHAT CONCERNED THAT WELL SEE SOME HEAVY RAIN TONIGHT LIKE
NORTHWEST MISSOURI AND SOUTHEAST NEBRASKA IS HAVING RIGHT NOW.
FLASH FLOOD GUIDANCE IS IN THE 1.5 TO 3 INCH RANGE EVERYWHERE...AND
I AM NOT THAT CONFIDENT THAT WELL SEE THAT MUCH PROLONGED HEAVY
RAIN TONIGHT...SO HAVE NOT ISSUED ANY HEADLINES WITH THIS PACKAGE.
WILL MENTION SOME HEAVY RAIN IN THE HAZARDOUS WEATHER OUTLOOK AND
MAKE THE DAY SHIFT AWARE OF MY CONCERNS.

DECREASING CHANCES FOR RAIN ON WEDNESDAY AS THE SURFACE BOUNDARY
FINALLY LIFTS NORTHWARD AND WE GET SOME WEAK ANTI-CYCLONIC FLOW
ALOFT.  COULD BE SOME RESIDUAL STORMS AROUND...ESPECIALLY IN THE
MORNING...BUT HAVE DECREASED POPS TO ONLY CHANCE CATEGORY BY
AFTERNOON.

GOOD SOUTHWEST FLOW ON THURSDAY BRINGS 850MB TEMPS IN AT +20C OR
BETTER...AND HAVE GIVEN OUR HIGHS A BOOST INTO THE UPPER 80S TO NEAR
90 TO ACCOUNT FOR THIS HEATING.

NO CHANGES TO DAYS 4-7 AT THIS TIME.

&&

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

CARNEY

EFFECTIVE 7 AM JUNE 8 2004...THE AWIPS PRODUCT IDENTIFIER FOR THIS
PRODUCT WILL CHANGE FROM AFDSTL TO AFDLSX.  THE WMO HEADER WILL
REMAIN UNCHANGED. PLEASE ENSURE THAT ANY NEEDED CHANGES ARE
COMPLETED BY JUNE 8 2004.

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
630 AM CDT TUE MAY 18 2004

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-191100-
ADAMS IL-AUDRAIN-BOND IL-BOONE-BROWN-CALHOUN IL-CALLAWAY-CLINTON IL-
COLE-CRAWFORD-FAYETTE IL-FRANKLIN-GASCONADE-GREENE IL-IRON-JEFFERSON-
JERSEY IL-KNOX-LEWIS-LINCOLN-MACOUPIN IL-MADISON-MADISON IL-MARION-
MARION IL-MONITEAU-MONROE-MONROE IL-MONTGOMERY-MONTGOMERY IL-OSAGE-
PIKE-PIKE IL-RALLS-RANDOLPH IL-REYNOLDS-SHELBY-ST CHARLES-
ST CLAIR IL-ST FRANCOIS-ST LOUIS-ST LOUIS CITY-STE GENEVIEVE-WARREN-
WASHINGTON-WASHINGTON IL-
630 AM CDT TUE MAY 18 2004

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

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY AND TONIGHT
ACROSS THE ENTIRE AREA.  ADDITIONALLY...LOCALLY HEAVY RAINFALL
WILL BE POSSIBLE WITH THESE STORMS.  A COLD FRONT WILL DRIFT OVER
THE AREA TODAY AS ONGOING CONVECTION PUSHES IT SOUTH OUT OF IOWA
INTO NORTHERN AND CENTRAL MISSOURI.  THIS COLD FRONT...ALONG WITH
PLENTIFUL MOISTURE IN THE LOWER ATMOSPHERE...WILL FUEL
THUNDERSTORMS TODAY AND TONIGHT.  THE PRIMARY THREAT FOR SEVERE
WEATHER WILL BE DAMAGING STRAIGHT LINE WINDS AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THUNDERSTORMS WILL CONTINUE OVER THE AREA ON WEDNESDAY...UNTIL THE
SURFACE FRONT FINALLY MOVES NORTH OF THE AREA WEDNESDAY EVENING.
THE THREAT FOR SEVERE THUNDERSTORMS APPEARS TO BE LIMITED TO
CENTRAL...AND EASTERN MISSOURI...AS WELL AS WEST CENTRAL AND
SOUTHWEST ILLINOIS WHERE THE FORCING FROM THE SURFACE FRONT WILL BE
STRONGEST.

THERE WILL BE A CHANCE FOR THUNDERSTORMS ON THURSDAY NIGHT IN NORTH
EAST MISSOURI AND WEST CENTRAL ILLINOIS.  THE CHANCE FOR
THUNDERSTORMS WILL EXPAND GRADUALLY SOUTHWARD FROM NORTHEAST
MISSOURI AND WEST CENTRAL ILLINOIS ON FRIDAY NIGHT AND SATURDAY...
INTO CENTRAL AND EASTERN MISSOURI AND SOUTHWEST ILLINOIS ON SUNDAY...
AND FINALLY ENCOMPASS THE THE ENTIRE AREA ON MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY AND TONIGHT.  IN THE EVENT
THAT HEAVY RAINFALL OCCURS...STORM SPOTTERS ARE ENCOURAGED TO CALL
IN RAINFALL TOTALS AS WELL.

CARNEY