Hail in Illinois, September 20, 2001

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
240 PM CDT THU SEP 20 2001

MAIN CHALLENGE DEALS WITH CHC OF PCPN THIS EVENING.   MODELS LOOKED
TO HAVE INITIALIZED WELL AND ARE IN GENERAL AGREEMENT...THOUGH
PREFER THE SLIGHTLY SLOWER ETA/NGM FRONTAL MOVEMENT ACROSS MO/IL
TONIGHT. 18Z SFC CHART INDICATES FRONT EXTENDS FROM WRN IA BACK INTO
SWRN KS.  REGIONAL RADARS INDICATE AREA OF TSRA BECOMING BETTER
ORGANIZED OVR PARTS OF SERN IA/NERN MO MOVG ESEWD ALONG WARM FRONT.
THIS AREA SHOULD AFFECT NRN ZONES INTO EARLY EVENING.  ALSO EXPECT
ADDITIONAL TSRA DEVELOPMENT ALONG CDFNT AS INSTABILITY INCREASES
AHEAD OF DIGGING SHORTWAVE TROF OVR ERN DAKOTAS.  SVR THREAT SHOULD
INCREASE INTO THE EVENING AS 0-6KM MEAN SHEAR INCREASE TO 45 KTS.
TSRA ASSOCIATED WITH FRONT SHOULD MOVE INTO NERN AND CNTRL MO BY
LATER THIS EVENING.  WILL GO WITH CAT POPS IN NRN ZONES AND GO WITH
LIKELY POPS ALONG I-70 AND CHC POPS NEAR FAM.  WILL KEEP CHC POPS
FROM STL SWD AND EWD FOR TOMORROW MORNING.  WL GO WITH MORE CLOUDS
IN IL TOMORROW.  OTHERWISE...EXPECT DRY CONDITION THROUGH SAT NIGHT
AS DEEP LAYER DRY AIR AND SINKING MOTION COMES IN BEHIND TROF.

WILL GENERALLY FOLLOW MAV/FWC TEMP GUIDANCE.  SIGNIFICANT DIFFERENCE
ON HIGHS TOMORROW.  PLAN TO USE A COMPROMISE AS IT LINES UP WELL
WITH 850 MB TEMPS.

IN THE EXTENDED...SEEING SOME SIGNIFICANT DIFFERENCES IN THE UPR AIR
PATTERN BY LATE IN THE WEEKEND AND NEXT WEEK.  THE OPNL MRF TAKES
THE DIGGING TROF AND CUTS OFF AND UPR LOW OVER THE MIDWEST KEEPING
IT THERE THRU THE END OF THE FCST PD.  WHILE THE MRF ENSEMBLE MEAN
SHOWS A DEEP TROF...IT DOES NOT SHOW THE SAME DEEP UPR LOW.  THE
CANADIAN ENSEMBLE KEEPS THE TROF PROGRESSIVE.  WILL BACK OFF FROM
THE DEEPER...SLOWER MRF SOLUTION KEEPING THE CHC OF SHRA ON SUNDAY
ONLY WITH FRONTAL PASSAGE AND THEN GOING WARMER THAN GUIDANCE NEXT
WEEK.

.STL...NONE

BRITT

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-034>036
-041-042-047>052-059>065-072>075-084-085-099-210100-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE ST LOUIS MO
1140 AM CDT THU SEP 20 2001

THE SEVERE WEATHER THREAT:  THERE IS A SLIGHT RISK OF SEVERE
THUNDERSTORMS TO THE WEST OF A LINE FROM SPRINGFIELD ILLINOIS
TO ST. LOUIS TO ROLLA MISSOURI.  THIS INCLUDES THE CITIES OF
QUINCY...BOWLING GREEN...ST. CHARLES...COLUMBIA AND JEFFERSON
CITY.

FOR THE PERIOD:  LATE THIS AFTERNOON AND TONIGHT.

THE WEATHER OUTLOOK:  THUNDERSTORMS ARE EXPECTED TO DEVELOP NORTHWEST
MISSOURI THIS AFTERNOON AS A COLD FRONT MOVES THROUGH WARM AND
UNSTABLE AIR.  THESE STORMS ARE EXPECTED TO SPREAD INTO NORTHEAST
AND CENTRAL MISSOURI AS WELL AS WEST CENTRAL ILLINOIS BY THIS
EVENING.  A FEW OF THESE STORMS MAY BECOME SEVERE WITH THE PRIMARY
THREAT BEING LARGE HAIL AND DAMAGING WINDS.

BRITT