Tornado and Damaging Wind in Iowa, June 26, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
255 AM CDT WED JUN 26 2002

FRONTAL BOUNDARY AND CONVECTIVE POTENTIAL OVER THE SOUTHERN AREA THE
MAIN CONCERN OF THIS FORECAST.

SURFACE COLD FRONT WAS LOCATED ALONG KSTC-KFRM-KSUX LINE AT 07Z WITH
A WEAK GRADIENT AND PUSH OF PACIFIC AIR TO ITS WEST. CONVECTIVE
BOUNDARY EXTENDED FROM KMSP-KLSE FOR SEVERAL HOURS EARLIER CAUSING
REGENERATION OF TSRA+ AND 4-6 INCH RAINS OVER BUFFALO AND WABASHA
COUNTIES. THIS HAS NOW SHIFTED SOUTH AS EXPECTED WITH FRONT
AND UPPER LEVEL SHORTWAVE TROUGH APPROACHING FROM THE WEST.

VERY WARM 850 MB TEMPERATURES PER 00Z DATA. WATER VAPOR IMAGERY
SHOWING SHORTWAVE TROUGH MOVING SOUTHEAST ACROSS MN TO CONTINUE BIG
PICTURE OF FORECAST PACKAGE. MOST OF THE SOUTHERN FORECAST AREA IS
QUITE WARM YET WITH CAP STILL IN PLACE AND MIDDLE 70S.

FOCUS WAS ON THE FIRST 24 HOURS. THE COLD FRONT WILL MOVE TO ROUGHLY
A KDBQ-KMKE LINE BY MID-AFTERNOON PER 00Z ETA. THE SOUTHERN FORECAST
AREA WILL SEE TSRA DURING THE MORNING.  THEN...MAYBE A BREAK BUT
CAPES BUILDING NEAR THE FRONT LATER. SBCAPES OF 2500-3000J/KG
COULD BE RIGHT ON GRANT/CLAYTON COUNTY IN EARLY AFTERNOON.  SHEAR
IS AGAIN WEAK FOR SUPERCELLS /20-25KTS 0-6KM BULK SHEAR/ AND DEEP
WARM CLOUD DEPTH OF 9KFT YIELDS HEAVY RAIN AS THE MAIN THREAT. THREAT
WILL SHIFT SOUTH BY LATE AFTERNOON OUT OF FORECAST AREA. 06Z ETA RUN
AGREES WITH THIS AFTER A QUICK LOOK. ALTHOUGH DEWPOINTS WILL FALL...
THIS WILL HAPPEN SLOWLY WED SO MLCAPES OF OVER 1000 J/KG MAY BE FOUND
S OF KRST-KDLL LINE BY AFTERNOON. WITH LACK OF SURFACE
BOUNDARY/CONVERGENCE AND MEAN SUBSIDENCE...NO RAIN MENTION LOOKS
FINE.

ENTIRE FORECAST AREA THEN UNDER RIDGE BUILDING. HAVE BUMPED THE
HIGHS SLIGHTLY THE WED/THU BASED ON SLOWER PROGRESSION TO RIDGE WED
AND LACK OF COOLER AIR IN OBSERVED DATA.

.LSE...NONE.

BAUMGARDT