Tornado Warning 31, NWS Springfield, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPRINGFIELD MO
419 PM CDT THU AUG 12 1999

FIRST PROBLEM IS IN THE SHORT TERM...WILL LET HEAT ADVISORY EXPIRE
AT 600 PM.  TEMPS THIS AFTN RANGED FROM 100 TO 106 ACROSS THE CWA.
THE AXIS OF HIGHEST SFC TEMPS XTNDD FROM AIZ/SGF/JLN AND WAS CAUSING
SCT CU AND SOME TCU TO DVLP SINCE 2130Z. THIS DVLPMT WAS ALG AND NR
THE AXIS OF HIGHEST TEMPS. LOOKS LIKE A 20 POP WILL NEED TO BE
INCLUDED THIS EVENING FOR THIS CONVECTN.

OTHERWISE...

CHC OF PCPN IN THIS FCST PERIOD COMPLICATED BY SVRL FACTORS THAT
COULD LEAD TO PCPN DVLPMT. NONE OF THESE FACTORS LOOK IDEAL AFT
LOOKING AT ANALYSIS AND MODEL DATA.

ANALYSIS OF 250 AND 500MB WINDS SHOWED A BROAD JET FROM SRN CA
THRU CO/WRN KS/ERN NE AND IA. MAIN 500MB TROF WAS OVER THE DAKOTAS
WITH TROF XTNDG INTO CO. SVRL MINOR WVS WERE WITHIN THE UPPER FLOW.
CLOSEST UPSTREAM SHRT WV XTNDD FROM SRN CO TO THE TX PNHDL. ETA
AND 12Z WV IMAGE SHOWED THIS FEATURE WELL. ETA WEAKENS THIS SHRT WV
BY 06Z TONIGHT BUT LATEST WV IMAGE INDICATED THAT SHRT WV HAS
WEAKENED MUCH MORE RAPIDLY THAN PROGD. THIS WEAKENING SYS WILL
PROBLY NOT HAVE MUCH INFLUENCE ON FUTURE TSTM DVLPMNT.

ALL MODELS DO AGREE ON STRENGTHENING THE DAKOTAS UPPER LVL TROF
DURG THE NEXT 24HRS. THIS WILL BE THE IMPETUS TO FINALLY DRIVE COLD
FRONT OVER KS INTO THE AREA.

WV IMAGE SHOWS GOOD CIRC CNTR/UPPR LVL LOW APPROACHING THE NRN CA
COAST. MAX WINDS...JUST TO THE SOUTH OF THIS CNTR...WAS BEGINNING TO
PULL THIS LOW EWD AND TWDS THE NRN CA COAST. ALL PROGS INDICATE
THIS LOW TO MOVE INLAND AND WILL FORCE RELATIVELY COLD UA TEMPS...
THAT WERE OVER THE PAC NW...INTO THE ROCKIES AND NRN/WRN HIGH PLNS
LATE TONIGHT. THIS INFUSION OF COLD UA TEMPS INTO THE WEST SIDE OF
DAKOTAS TROF WILL AMPLIFY THE TROF AND WILL FUNCTION TO KICK SFC COLD
FRONT THRU THE WRN CWA AFT 06Z TONIGHT AND THRU THE ERN CWA BY 18Z
FRI.

SFC BASED TSTMS SHOULD DVLP ALG COLD FRONT OVER CNTRL KS BEFORE
SUNSET THIS EVE...IF CAP CAN BE BROKEN...AND THIS IS POSSIBLE AS
700MB COLD FRONT IS CLOSE BY. THERE HAS BEEN A PERSISTENT MID-LEVEL
CLOUD FEATURE OVER CNTRL KS TODAY THAT COINCIDES WITH 700MB THERMAL
TROF. THIS BAND OF MSTR MAY HELP THE PSSBLTY OF ELEVATED CONVECTION
TONIGHT. COLD FNT ALG WITH PSSBL TSTMS...WILL BE PUSHED EWD INTO THE
WRN PTN OF THE CWA ON OR AFT 06Z. THE PROBLEM FOR TONIGHT IS THE
SURVIVABILITY OF THE STORMS BEYOND SUNSET.

WOULD EXPECT THAT BY 06Z...KS TSTMS...IF ANY...THAT DO FORM...WILL BE
WEAK TO THE POINT OF DISSIPATION. THE CHC FOR PCPN THEN DEPENDS ON
ELEVATED CONVECTION DVLPG OVERNIGHT...AND THAT DOES NOT LOOK THAT
PROMISING EITHER. NEVER THE LESS...ETA PROGS 850MB DWPTS TO POOL ALG
AND AHEAD OF COLD FRONT WITH WEAK WAA AT MID-LEVELS. THIS MAY LEAD TO
THE DVLPMNT OF ELEVATED CONVECTION FROM 06Z TO 12Z AS FRONT SWEEPS
ACROSS THE WRN HALF OF CWA. ETA ALSO PROGS DRY 700MB AIR INTO THE
AREA AS 700MB COLD FRONT APPROACHES...THIS COULD MAKE THINGS
INTERESTING IF TSTMS RE-DEVELOP...AS THE POTENTIAL WOULD EXIST FOR
SOME OF THE STORMS TO ENTRAIN DRY MID-LVL AIR...RESULTING IN SOME STG
WIND GUSTS. THE WHOLE NEGATIVE FACTOR IN PCPN OVRNGT AND FRI AM IS
WEST WINDS AT 850MBS AHEAD OF THE FRONT...THUS MINIMIZING CONVRGC.

WILL PUT IN LOW POPS IN ZONES OVRNGT AND OVER THE ERN ONE THIRD OF
ZONES BEFORE NOON FRI.

AFT FRONT MOVES THRU FRI...LOOK FOR MUCH COOLER TEMPS TO ARRIVE...
ESPECIALLY FRI NGT AND SAT AM. MAIN THRUST OF CAA WILL OCCUR
BEGINNING LATE FRI AFTN AND CONT FRI NGT AS SFC HIGH BUILDS INTO IA
AND KS. HEAT ADVISORY WILL NOT BE NEEDED FRI AS HI TEMPS WILL RANGE
FROM THE LOWER 90S OVER THE SRN HALF OF CWA TO THE MID 80S OVER THE
NRN PTN. LOOK FOR SOME CU TO FORM ON FRI WITH SCT TO BKN CVRG.

LOW TEMPS FRI NGT LOOK INTERESTING. FAN GUID HAS MID TO UPPER 50S
WHILE FWC HAS LOW TO MID 60S. FMR GUID HAS LOW 60S. THINK THAT FAN
GUID A BIT TOO COOL SO WILL GO CLOSE TO FWC FOR LOWS FRI NGT. WILL
ALSO STICK WITH FWC TEMPS FOR HIGHS ON FRI AND SAT.

WILL GO WITH HAVE TO GO A LITTLE HIGHER THAN FWC AND FAN POPS FOR
TNGT AND FRI.

CCF NUMBERS:
SGF BU 072/092 065/088 066 123300
JLN BU 073/090 066/089 067 123300
VIH BU 072/088 062/086 065 123300
UNO BU 072/092 065/088 066 123300

.SGF...NONE

D.STEINMETZ