Severe Thunderstorm Warning 159, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
220 PM CDT MON SEP 11 2000

PRIMARY CONCERN...SEVERE WEATHER POTENTIAL INTO THIS EVENING.

SURFACE ANALYSIS INDICATED LOW PRESSURE IN SOUTHEAST MN...MOVING
ALONG FRONTAL BOUNDARY EXTENDING FROM NORTHWEST WI TO WESTERN IOWA.
AIR MASS VERY MOIST AND UNSTABLE AHEAD OF THE FRONT WITH MSAS
INDICATING LIFTED INDICES OF MINUS 8 AND GOOD LOW LEVEL MOISTURE
CONVERGENCE. SHORT WAVE SEEN IN WATER VAPOR IMAGERY ADVANCING ACROSS
THE NORTH DAKOTA/CANADIAN BORDER AS UPPER LEVEL TROUGH AMPLIFIES.

12Z MODELS INITIALIZED WELL AND AGREE THAT UPPER LEVEL TROUGH WILL
MOVE RAPIDLY TOWARD THE GREAT LAKES TONIGHT...SWEEPING THE ASSOCIATED
SURFACE COLD FRONT QUICKLY ACROSS THE FORECAST AREA THIS EVENING.
WITH RESPECT TO DETAILS...PREFER THE ETA MODEL OVERALL...ESPECIALLY
WITH DEPICTION OF QPF ASSOCIATED WITH STRONG CONVECTION THIS EVENING.

ALL PARAMETERS STILL POINT TO POTENTIAL FOR SEVERE WEATHER IN THE
FORECAST AREA LATE THIS AFTERNOON INTO THIS EVENING AS THE COLD FRONT
MOVES THROUGH. ATMOSPHERE QUITE UNSTABLE WITH CAPES OF 3000-4000
J/KG...K AND LIFTED INDICES OF 35 TO 40 AND MINUS 8 RESPECTIVELY.
IN ADDITION...STRONG UPPER LEVEL DIVERGENCE NOTED ASSOCIATED WITH 100
KNOT 300 MB JET ALONG THE U.S./CANADIAN BORDER PROVIDES LARGE SCALE
ASCENT TO FUEL DEEP CONVECTION.

DUE TO STEADY PACE OF COLD FRONT...STORMS EXPECTED TO MOVE ALONG
RATHER QUICKLY AND EXIT THE FORECAST AREA THIS EVENING. THIS SHOULD
PRECLUDE ANY POTENTIAL FOR FLASH FLOODING FOR OUR NORTH CENTRAL WI
ZONES WHERE 2 TO 4 INCHES OF RAIN FELL LAST NIGHT. THEREFORE...WILL
PLAN TO CANCEL FLASH FLOOD WATCH THAT WAS TO BE IN EFFECT THROUGH
THIS EVENING FOR THAT AREA.

WEATHER NIL NEXT SEVERAL DAYS...AS HIGH PRESSURE BUILDS IN WITH MUCH
COOLER AND DRIER AIR MASS. NEXT FRONTAL BOUNDARY EXPECTED TO MOVE
INTO THE AREA WEDNESDAY...BUT THIS SYSTEM SHOULD PASS THROUGH DRY AS
MOISTURE WILL BE LIMITED.

CURRENT FORECAST TEMPERATURES APPEAR TO BE ON TARGET BASED ON
FORECAST SOUNDINGS. THIS SUPPORTS LOWS IN THE MIDDLE 40S TO MIDDLE
50S...WHILE DAYTIME HIGHS REACH THE UPPER 60S TO MIDDLE 70S NEXT
COUPLE OF DAYS.

.LSE...NONE.

THOMPSON

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-032>034-
041>044-053>055-061-120230-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LA CROSSE WI
1135 AM CDT MON SEP 11 2000

...SEVERE THUNDERSTORMS POSSIBLE FOR THE AREA THIS AFTERNOON AND
EVENING...

STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE ACROSS THE AREA THIS
AFTERNOON AND INTO THE EVENING.  THE STORMS WILL LIKELY BEGIN AS
INDIVIDUAL SUPERCELL THUNDERSTORMS...WITH LARGE HAIL...DAMAGING WINDS
AND ISOLATED TORNADOES POSSIBLE.  TOWARD EVENING...THE STORMS WILL
EVOLVE INTO A SQUALL LINE WITH LARGE HAIL AND DAMAGING WINDS THE
PRIMARY THREATS.

SPOTTER ACTIVATION IS A GOOD BET THIS AFTERNOON AND EVENING...SO
EMERGENCY MANAGEMENT OFFICIALS AND SPOTTER GROUPS SHOULD MAKE
TENTATIVE PREPARATIONS NOW.

THE THUNDERSTORMS WHICH CROSSED THE AREA LAST NIGHT HAVE LEFT BEHIND
AN OUTFLOW BOUNDARY...WHICH REACHED FROM SOUTHERN WISCONSIN INTO
NORTHEAST IOWA AT MID-DAY.  IN ADDITION...A STRONG COLD FRONT AND
UPPER DISTURBANCE WILL MOVE TOWARD THE AREA THIS AFTERNOON.  THE
FRONT IS EXPECTED TO CROSS SOUTHEAST MINNESOTA BETWEEN 3 AND 6 PM...
NORTHEAST IOWA FROM 4 TO 7 PM...AND SOUTHWEST WISCONSIN BETWEEN 5
AND 9 PM.  VERY WARM AND HUMID AIR WILL BE IN PLACE AHEAD OF THE
FRONT...WITH COOLER AND DRIER AIR ARRIVING BEHIND. THIS CONTRAST IN
AIRMASSES...AND WITH A GOOD DEAL OF INSTABILITY AVAILABLE...SHOULD
PROVIDE AMPLE FUEL FOR STRONG TO SEVERE THUNDERSTORM DEVELOPMENT
ALONG AND AHEAD OF THE BOUNDARY.

WELVAERT

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LA CROSSE WI
1243 PM CDT MON SEP 11 2000

TIME(CDT)  .....CITY LOCATION.....STATE   ...EVENT/REMARKS...
           ....COUNTY LOCATION....

1008 PM    5 E FOUNTAIN CITY         WI   .75 INCH HAIL
09/10/00   BUFFALO                        REPORTED BY THE PUBLIC.

1010 PM    BELLINGER                 WI   WIND DAMAGE
09/10/00   TAYLOR                         REPORTED BY SHERIFF DEPT.

SHEA

N