Severe Thunderstorm Warning 54, NWS St. Louis, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
345 AM CDT SUN MAY 4 2003

DYNAMICS AND INSTABILITY WL FORM DANGEROUS COMBO FOR EVENTS DURG THE
NXT 24HRS...WITH SOME RESULTS OF THAT ALREADY EVIDENT ON RADAR
MOSAIC.  DPNG S/W OVR NRN HI PLNS WL SLIDE A LTL EWD AND CUTOFF
UNDER L/W RDG TDA...AND THIS PTRN XPCTD TO PERSIST AT LEAST THRU MON
NGT...WHEN MDLS TRY TO WASH OUT UPR LO.  THIS PTRN WL GENERALLY
SIGNAL FOR UNSETTLED WX WITH ANY FNTL BDRYS HAVING TROUBLE MAKING
MUCH SWD PENETRATION GIVEN FAIRLY ZONAL/WSW MID-LVL FLOW REGIME.

REGIONAL RADARS SHOW COMPLEX AREAS OF PCPN...WITH BOWING MCS OVR
NEB...ANOTR DVLPG MCS NR KANSAS CITY...AND SEVERAL BANDS OF PCPN.
FIRST BAND OF PCPN WAS NOTHING MORE THAN WEEPING ACC--THIS IS NOW E
OF MS RVR...WITH EACH SUCCESSIVE BAND OF PCPN A LTL MORE POTENT THAN
THE LAST AS INSTABILITY BLDS AND MOIST LYR OF AMS DPNS.  NXT BAND OF
PCPN NOW MOVG THRU MO PRTNS OF FA AND EVEN STGR BAND OF TSTMS NOW
MOVG INTO WRN MO.  BANDED NW-SE STRUCTURE OF PCPN RESULT OF LOW-MID
LVL WAA/THTA-E ADVCTN.  THIS FORCING...SOME DISTANCE NE OF SFC
WRMFNT...WL CONT TO PRODUCE PCPN FOR MUCH OF THE DAY...ENDING FM SW
TO NE BTWN MIDDAY AND MID-AFTN.  MAIN SVR THREAT WITH THIS WL BE LRG
HAIL.

WRMFNT XPCTD TO EXTD FM NR STJ-N OF COU-JUST S OF STL-CGI BY
00Z/MON.  08Z SFC PLOT ALREADY SHOWS TEMPS IN 70S/DWPTS 65-70F
MASSING JUST S OF WRMFNT...AND SO THEREIN LIES THE POTNL FOR TEMPS
TO RPDLY SHOOT UP LATE THIS AFTN IF ENUF BREAKS IN CLDS CAN DVLP.
EVEN IF CLDS DO HOLD IN TIL NIGHTFALL...NOTICEABLE TEMP RISE WL
STILL ACCOMPANY WRM FROPA.  STG LLVL JET HELPING TO MAINTAIN MCS OVR
NEB WL SLIDE EWD TDA...AND WITH WRM FROPA...WL HELP TO MIX DOWN VERY
STG WNDS FOR LATE AFTN AND THRU EVNG HRS.

WITH WRM FROPA...ELEVATED EVENT WL END...WITH SFC-BASED EVENT XPCTD
TO START ACRS WRN MO THIS AFTN AND THEN SPREAD EWD.  FOR OUR AREA
THIS WL MEAN VERY LATE AFTN THRU MOST OF TNGT.  JUICY AMS (1.5
PWATS) WL COMBINE WITH VERY STEEP MID-LVL LAPSE RATES...APPCHG S/W
AND ITS ASSOC SPEED MAX WL CREATE POTNL FOR DANGEROUS STMS.

MOST OF ACTIVITY WL LEAVE BY MON...WITH UPR LO TO THE N HELPING TO
BRING AREA OF SUBSIDENCE ACRS RGN...BTWN CLDS/PCPN UNDERNEATH LO TO
THE N AND SCT PCPN ASSOC WITH OLD LLVL BDRY TO THE S...WHERE CHC
POPS WERE KEPT MON THRU TUE NGT.  THIS BDRY WL RESIST EFFORTS TO TRY
TO MOV IT...RMNG ACRS SERN MO THRU TUE NGT WHEN MDLS BRING ANOTR S/W
THRU.

.STL...NONE.
TES

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-051200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
700 AM CDT SUN MAY 4 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL AND EASTERN MISSOURI
AND WEST CENTRAL AND SOUTHWEST ILLINOIS.

.DAY ONE...TODAY AND TONIGHT

THERE IS A MODERATE RISK FOR SEVERE THUNDERSTORMS ACROSS THE ENTIRE
AREA.  AN AREA OF THUNDERSTORMS WILL FIRST AFFECT MUCH OF THE AREA
THROUGH EARLY THIS AFTERNOON...WITH LARGE HAIL BEING THE PRIMARY
SEVERE THREAT.

LATER THIS AFTERNOON AND CONTINUING THROUGH TONIGHT...CONDITIONS
APPEAR EVEN MORE FAVORABLE FOR THE DEVELOPMENT OF SEVERE
THUNDERSTORMS.  THE MAIN SEVERE THREATS WILL BE DAMAGING WINDS AND
LARGE HAIL...WITH THE POSSIBILITY OF TORNADOES AS WELL.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A LINGERING FRONTAL BOUNDARY WILL PROVIDE THE POTENTIAL FOR
THUNDERSTORM DEVELOPMENT ACROSS SOUTH CENTRAL ILLINOIS AND SOUTHEAST
MISSOURI ON MONDAY...WITH THE THUNDERSTORM CHANCES PERSISTING FOR
SOUTHEAST MISSOURI THROUGH TUESDAY AND WEDNESDAY.

THERE WILL BE THE CHANCE FOR YET MORE THUNDERSTORMS ON THURSDAY AND
FRIDAY ACROSS THE ENTIRE AREA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY AND TONIGHT.  SPOTTERS ARE
ENCOURAGED TO RELAY REPORTS OF SEVERE WEATHER PROMPTLY TO THE
NATIONAL WEATHER SERVICE.

&&

MORE INFORMATION MAY BE OBTAINED AT...
HTTP://WWW.CRH.NOAA.GOV/LSX (ALL LOWER CASE)

TES