Severe Thunderstorm Warning 131, NWS St. Louis, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
356 PM CDT MON JUN 7 1999

MAIN FCST PROBLEM: CHANCES FOR PRECIP.

SUMMERLIKE PATTERN MAKING THIS A COMPLEX FORECAST DURING THIS PERIOD.
ALL UPPER LVL FEATURES VERY WK...BUT WITH MOIST AND UNSTABLE AIR...
DAYTIME HEATING AND WK DISTRBCS IN THE UPPER FLOW...WILL LEAD TO
SOME CONVECTN AROUND THE CWFA. THE PROBLEM IS HOW TO HANDLE THESE
EVENTS BOTH SPACIALLY AND TEMPORALLY.

ALL MODEL INITIAL FIELDS IN AGREEMENT WITH MOST SYNOPTIC SCALE
FEATURES WITH THE EXECPTION OF VORT AND ASSOC MSTR PATTERN OVER OK
THIS AM. OF THE THREE...ETA INITIALIZED THE BEST...BUT NOT PERFECT.

RELATIVELY COOL 700MB TEMPS...COMPARED TO SUNDAY...ALG WITH HTG OF
MOIST UNSTABLE AIR MASS RESULTED IN ISOLD TSTMS AND SHWRS OVER SML
PTNS OF SCNTRL AND SWRN MO. BELIEVE THAT THIS CONVCTN WILL DIMINISH
AFTR SUNSET. THE EXCEPTN WILL BE OVER XTRM SERN KS AND XTRM SWRN MO
WHERE APPROACHING VORT CNTR FROM OK MAY ADD A BIT MORE SUPPORT FOR
CONTINUING TSTMS BEYOND SUNSET.

THIS MORNINGS UPPER AIR ANALYSIS HAD WELL DEFINED TROF AT 500MB WITH
MINUS 11 DEG COLD POOL. THIS LOW LOSSED DEFINITION BELOW 700MBS WITH
ONLY A WEAK SFC REFLECTION ALONG THE RED RIVER. LATEST WV IMAGERY
SHOWS VORT CNTR MOVING AT 225/25KTS...THIS WOULD PLACE VORT CNTR JUST
EAST OF MKC BY 12Z TUES. ETA TRENDS TOWARDS STRETCHING VORT CNTR THRU
24HRS AND IS A BIT SLOW. NGM MAINTAINS CONTINUITY WITH VORT CNTR OVER
24HRS...THIS LOOKS REASONABLE BUT IS TOO FAR TO THE WEST. NGM PLACES
VORT CNTR NR BIE BY 12Z TUES. AVN IS SIMILAR TO ETA. WILL GO WITH NGM
FOR THIS FCST PERIOD BUT WILL ADJUST VORT CNTR TO THE EAST.

THE ADJUSTED THE NGM FCST...WILL PLACE VORT CNTR OVER NWRN MO ARND
12Z TUES AND INTO ERN IA BY 00Z WED. THIS WOULD PLACE THE WRN MOST
COUNTIES WITH THE BEST CHC AND AREAL COVRGE OF TSTMS TONIGHT AND
TUESDAY...THE REASONS...DAYTIME HEATING OF UNSTABLE AIR MASS AND
POSSBL REDVLPMNT DURG NGT. THE CHANCES LESSEN SOMEWHAT TOWARDS THE
ERN MOST COUNTIES...WHERE INFLUENCE FROM VORT CNTR WILL BE LESS.

WILL HAVE TO INCLUDE A CHC FOR TSTMS FOR MOST OF THE CWFA ON TUES
WITH VARYING DEGREES IN PROBABILITIES...AS COLD POOL ASSOC WITH VORT
CNTR...WILL BRUSH MOST OF THE CWFA DURG TUES AND THAT WILL HELP IN
MAINTAINING INSTABILITY FOR SCT AFTN TSTMS.

WILL LEAVE MENTION OF PCPN OUT OF THE FCST FOR TUES NGT THRU WED NGT
AS THERE WILL BE NO UPPER SUPPORT. THE CHCS FOR PCPN FOR WED WILL BE
CLIMO FAVORED LATE AFTN AND EVE TSTMS.

FOR THE PERIODS BEYOND WED NGT...MRF BRINGS 500MB LOW THAT WAS OFF
THE WRN FL COAST...AND NUDGES THE LOW INTO THE SRN PLNS. THIS WOULD
LEAD TO A DEEP TROPICAL AIRMASS WITH CHCS FOR TSTMS FOR THU INTO SAT.

CCF
SGF BB 067/088 068/089 065 1223--
JLN BB 068/089 069/089 068 1233--
UNO BB 067/088 068/089 066 1222--
VIH BB 067/088 068/089 066 1222--

D.STEINMETZ