Severe Thunderstorm Warning 386, NWS St. Louis, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
400 PM CDT THU AUG 17 2000

20Z MSAS DATA INDICATES CDFNT ENTERING NRN SXNS OF FA...EXTDG FM
NERN MO (JUST E OF KIRK) SWWD THRU W CNTRL MO INTO SERN KS.  MDT-STG
LLVL CONV IND ALG/JUST AHD OF FNT WITH LI/S AOB -10 AND CAPES ARND
5000 J/KG.  BAND OF LLVL CONV FINALLY ENTERING RGN OF WK ENUF
SFC-BASED CAP TO BEGIN TO DVLP CU FIELDS ACRS CNTRL/NERN MO.  TSTM
DVLPMT XPCTD TO BE IMMINENT.  SUM POST-FNTL PCPN ALSO EXISTS OVR NRN
MO/SRN IA AS A RESULT OF MID LVL S/W.

FCST PROB FOR THE AFTN PACKAGE IS PCPN CHCS TNGT AND THEN TEMPS FRI
THRU SAT.

12Z MODELS IN GOOD AGRMT THRU 48HRS.  S/W OVR NRN MO/SRN IA WL MOV
EWD THRU CNTRL IL TNGT.  RDG AXIS OVR ERN ROCKIES WL SLIDE EWD INTO
PLNS BY SAT...PROMOTING A W TO NWLY UPR FLO THRU PD.  APPEARS A
CONVECTIVELY INDUCED VORT MX WL TRY TO UNDERCUT RDG ON SAT AND MOV
INTO NRN/WRN ZONES.  ON SFC FEATURES...CDFNT WL MOV THRU MOST OF FA
THIS EVNG...AND THEN THRU RMNDR SRN ZONES OVRNGT.  CANADIAN HI PRES
WL THEN DOMINATE RGN THRU FRI NGT...WITH A WRMFNT THEN SLIDING INTO
WRN MO ON SAT.

FOR TNGT...HAVE EVERY REASON TO BELIEVE BKN LN OF CONVECTION WL DVLP
SOON...ACRS CNTRL-NERN MO AND THIS LN WL TRACK W/ FNT THRU MOST OF
FA.  PWAT VALUES ARND 2 INCHES...MDT-STG LLVL CONV...AND HI INSTAB
AIRMASS SHD FAVOR THAT SCENARIO.  VORT MX WL KEEP POST-FNTL PCPN
GOING ACRS NRN ZONES THIS EVNG...THOUGH THEY MISS MUCH OF THE BKN LN
OF TSTMS THAT SHD DVLP SOON.  WENT MUCH ABV GUIDANCE POPS...BUT
TENDED TO FOLLOW GUIDANCE TEMPS.

FOR FRI...CANADIAN AIRMASS TO DOMINATE WX-SCENE...WITH VERY AUTUMN
LIKE SITN SETTING UP.  SHD SEE EXTENSIVE MVFR CIG DECK ACRS
CNTRL/NRN ZONES IN MRNG...AND WL BREAK UP SOMEWHAT FM S TO N DURG
AFTN.  N-NELY SFC WNDS AND CLDS SHD RESULT IN TEMPS ABT 20 DEG
COOLER THAN TDA...AND TENDED TO GO AOB GUIDANCE TEMPS.

FOR SAT...CONVECTION TO OUR W WL SPREAD HI CLD DECK OVR ERL IN PD.
MODELS ALL INDICATING TO ENUF MOISTURE RTRN IN WRN/NRN ZONES WITH
UPR LVL DYNAMICS TO WARRANT RAIN CHCS IN AFTN THESE AREAS.  OTRW...
ELY LLVL FLOW/CLDS WL KEEP TEMPS IN CHECK.

.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>075-084-085-099-181100-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
1155 AM CDT THU AUG 17 2000

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND
TONIGHT FOR THE ENTIRE AREA.  STORM SPOTTER GROUPS AND EMERGENCY
MANAGERS SHOULD MONITOR DEVELOPMENTS FOR POSSIBLE SKYWARN ACTIVATION.

A COLD FRONT AT MIDDAY EXTENDED FROM SOUTHEAST IOWA SOUTHWESTWARD
THROUGH NORTHWEST MISSOURI INTO SOUTHEAST KANSAS.  THIS FRONT WILL
MOVE TO THE SOUTHEAST THIS AFTERNOON AND TONIGHT...AND BY LATE THIS
AFTERNOON EXTEND FROM CENTRAL ILLINOIS THROUGH CENTRAL MISSOURI.  BY
AROUND MIDNIGHT...THIS FRONT WILL EXTEND FROM SOUTHERN ILLINOIS
THROUGH SOUTHEAST MISSOURI.  THE COLD FRONT WILL MOVE INTO A VERY
UNSTABLE AND MOIST AIRMASS...AND AS IT DOES SO WILL ACT AS A FOCUS
FOR THUNDERSTORM DEVELOPMENT BEGINNING EARLY THIS AFTERNOON ACROSS
THE QUINCY/HANNIBAL AREAS SOUTHWEST INTO MID MISSOURI BY MID AFTERNOON.

THUNDERSTORMS WILL MOVE TO THE EAST AT 25 TO 35 MPH.

THIS OUTLOOK COVERS THE COUNTY WARNING AREA OF THE NATIONAL WEATHER
SERVICE OFFICEC IN ST LOUIS.  AREAS INCLUDED ARE PORTIONS OF EASTERN
AND CENTRAL MISSOURI AND SOUTHWEST ILLINOIS.

TES