Severe Thunderstorm Warning 128, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
220 PM CDT WED JUN 24 1998

CONCERN IN FIRST PART OF FORECAST IS SEVERE WEATHER THREAT AND
FLASH FLOOD POTENTIAL TONIGHT.

AT 18Z A WARM FRONT APPEARS TO STRETCH ACROSS SOUTHERN MINNESOTA AND
INTO CENTRAL WISCONSIN. BOUNDARIES FROM EARLY MORNING CONVECTION HARD
TO FIND AT THIS POINT AND MIXING OF LOW LEVEL WINDS ACROSS IOWA
SUGGEST THESE BOUNDARIES MAY BE WASHED OUT. LATEST GOES-8 SOUNDER
DATA ALSO SHOWS CAPES OF 1500-3000 J/KG AND LIFTED INDICIES OF -5
TO -10 ACROSS MAINLY OUR WESTERN FORECAST ZONES. SOME ENHANCED
CUMULUS ACROSS NORTHWEST IOWA AND APPROACHING DBQ...OTHERWISE
FAIRLY QUIET AFTERNOON.

PLENTY OF FUEL FOR THE FIRE WITH VERY UNSTABLE ATMOSPHERE...FAVORABLE
WIND PROFILE AND SHEAR VALUES IN PLACE. PROBLEM WITH SEVERE WEATHER
THREAT IS WHERE EXACTLY STUFF WILL POP. CAP IS GROWING JUST SOUTHWEST
OF OUR FORECAST AREA WITH 18Z KDVN SOUNDING UP TO +11 DEG C AT 700 MB
UP FROM +9 AT 12Z. STRONG CIN ALSO FORECAST ACROSS MUCH OF IOWA SO
WOULD THINK CONVECTION WILL POP ON NORTHERN EDGE OF THIS CAP...MOST
LIKELY ACROSS NORTHEAST IOWA. EXACT LOCATION HARD TO PIN-POINT.

HAVE ALSO BEEN EXAMINING DATA TO TRY AND FIND SOMETHING TO INITIATE
CONVECTION. MODELS CONSISTENT IN BRINGING SHORT WAVE TROUGH OVER
NEBRASKA PANHANDLE INTO NORTHERN IOWA THIS EVENING. THIS SEEMS TO
LINE UP WELL WITH LATEST WATER VAPOR IMAGERY AND SHOULD PROVIDE
ENOUGH ADDED LIFT TO FIRE STORMS TONIGHT. RESPONSE FROM THIS SHORT
WAVE TROUGH SHOWING UP AS SLIGHT DEEPENING AT SURFACE OVER NEBRASKA.
BACKING OF WINDS AHEAD OF THIS SURFACE FEATURE MAY HELP CONVERGENCE
ACROSS NORTHERN IOWA AND WILL ONLY INCREASE THE AMOUNT OF SHEAR FOR
SUPERCELL OR TORNADO DEVELOPMENT.

ASSUMING THUNDERSTORMS FIRE...NEXT PROBLEM IS RAIN POTENTIAL. GRIDDED
DATA PAINTS HIGHEST K-INDICIES AND PRECIPITABLE WATERS APPROACHING 2
INCHES IN EAST-WEST CORRIDOR ALONG IOWA-MINNESOTA BORDER. THIS AREA
HAS ALSO RECEIVED A LOT OF RAIN PAST 6 DAYS WITH MOST FLASH FLOOD
GUIDANCE VALUES AT AN INCH OR LESS IN 3 HOURS. FLASH FLOOD WATCH MAY
BE NEEDED IN THIS AREA AS WELL.

COORD. W/GRB..MPX..DMX..DVN

SHEA

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
515 PM CDT WED JUN 24 1998

...STRONG THUNDERSTORMS OVER PARTS OF NORTHEAST IOWA AND SOUTHWEST
WISCONSIN...

DOPPLER RADAR INDICATED A NARROW BAND OF THUNDERSTORMS EXTENDING
FROM 20 MILES SOUTHWEST OF DECORAH NEAR CALMAR TO 50 MILES
SOUTH OF LA CROSSE NEAR PRAIRIE DU CHIEN. THE STORMS WERE MOVING
NORTHEAST AT 45 MPH. AT 455 PM AND 505 PM...VERY HEAVY RAIN AND PEA
TO MARBLE SIZE HAIL WAS REPORTED IN POSTVILLE IOWA AND NEAR PRAIRIE
DU CHIEN WISCONSIN RESPECTIVELY.

THESE STORMS ARE EXPECTED TO CONTINUE MOVING STEADILY NORTHEAST AND
PRODUCE HEAVY DOWNPOURS ALONG WITH SMALL HAIL...GUSTY WINDS AND
DANGEROUS LIGHTNING.

GO INDOORS IF A STORM AFFECTS YOUR LOCATION. REMEMBER...A FLASH
FLOOD WATCH IS IN EFFECT TONIGHT FOR ALL OF NORTHEAST IOWA AND
SOUTHWEST WISCONSIN. BE ALERT FOR THE POSSIBILITY OF FLOODING AND DO
NOT DRIVE ACROSS AREAS WHERE WATER COVERS THE ROAD.

THOMPSON

IAZ008>011-018-019-029-030-WIZ053>055-061-250100-

SPECIAL WEATHER STATEMENT...CORRECTED FOR UGC CODES
NATIONAL WEATHER SERVICE LA CROSSE WI
515 PM CDT WED JUN 24 1998

...STRONG THUNDERSTORMS OVER PARTS OF NORTHEAST IOWA AND SOUTHWEST
WISCONSIN...

DOPPLER RADAR INDICATED A NARROW BAND OF THUNDERSTORMS EXTENDING
FROM 20 MILES SOUTHWEST OF DECORAH NEAR CALMAR TO 50 MILES
SOUTH OF LA CROSSE NEAR PRAIRIE DU CHIEN. THE STORMS WERE MOVING
NORTHEAST AT 45 MPH. AT 455 PM AND 505 PM...VERY HEAVY RAIN AND PEA
TO MARBLE SIZE HAIL WAS REPORTED IN POSTVILLE IOWA AND NEAR PRAIRIE
DU CHIEN WISCONSIN RESPECTIVELY.

THESE STORMS ARE EXPECTED TO CONTINUE MOVING STEADILY NORTHEAST AND
PRODUCE HEAVY DOWNPOURS ALONG WITH SMALL HAIL...GUSTY WINDS AND
DANGEROUS LIGHTNING.

GO INDOORS IF A STORM AFFECTS YOUR LOCATION. REMEMBER...A FLASH
FLOOD WATCH IS IN EFFECT TONIGHT FOR ALL OF NORTHEAST IOWA AND
SOUTHWEST WISCONSIN. BE ALERT FOR THE POSSIBILITY OF FLOODING AND DO
NOT DRIVE ACROSS AREAS WHERE WATER COVERS THE ROAD.

THOMPSON

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
515 PM CDT WED JUN 24 1998

...STRONG THUNDERSTORMS OVER PARTS OF NORTHEAST IOWA AND SOUTHWEST
WISCONSIN...

DOPPLER RADAR INDICATED A NARROW BAND OF THUNDERSTORMS EXTENDING
FROM 20 MILES SOUTHWEST OF DECORAH NEAR CALMAR TO 50 MILES
SOUTH OF LA CROSSE NEAR PRAIRIE DU CHIEN. THE STORMS WERE MOVING
NORTHEAST AT 45 MPH. AT 455 PM AND 505 PM...VERY HEAVY RAIN AND PEA
TO MARBLE SIZE HAIL WAS REPORTED IN POSTVILLE IOWA AND NEAR PRAIRIE
DU CHIEN WISCONSIN RESPECTIVELY.

THESE STORMS ARE EXPECTED TO CONTINUE MOVING STEADILY NORTHEAST AND
PRODUCE HEAVY DOWNPOURS ALONG WITH SMALL HAIL...GUSTY WINDS AND
DANGEROUS LIGHTNING.

GO INDOORS IF A STORM AFFECTS YOUR LOCATION. REMEMBER...A FLASH
FLOOD WATCH IS IN EFFECT TONIGHT FOR ALL OF NORTHEAST IOWA AND
SOUTHWEST WISCONSIN. BE ALERT FOR THE POSSIBILITY OF FLOODING AND DO
NOT DRIVE ACROSS AREAS WHERE WATER COVERS THE ROAD.

THOMPSON

IAZ008>011-018-019-029-030-WIZ053>055-061-250100-

SPECIAL WEATHER STATEMENT...CORRECTED FOR UGC CODES
NATIONAL WEATHER SERVICE LA CROSSE WI
515 PM CDT WED JUN 24 1998

...STRONG THUNDERSTORMS OVER PARTS OF NORTHEAST IOWA AND SOUTHWEST
WISCONSIN...

DOPPLER RADAR INDICATED A NARROW BAND OF THUNDERSTORMS EXTENDING
FROM 20 MILES SOUTHWEST OF DECORAH NEAR CALMAR TO 50 MILES
SOUTH OF LA CROSSE NEAR PRAIRIE DU CHIEN. THE STORMS WERE MOVING
NORTHEAST AT 45 MPH. AT 455 PM AND 505 PM...VERY HEAVY RAIN AND PEA
TO MARBLE SIZE HAIL WAS REPORTED IN POSTVILLE IOWA AND NEAR PRAIRIE
DU CHIEN WISCONSIN RESPECTIVELY.

THESE STORMS ARE EXPECTED TO CONTINUE MOVING STEADILY NORTHEAST AND
PRODUCE HEAVY DOWNPOURS ALONG WITH SMALL HAIL...GUSTY WINDS AND
DANGEROUS LIGHTNING.

GO INDOORS IF A STORM AFFECTS YOUR LOCATION. REMEMBER...A FLASH
FLOOD WATCH IS IN EFFECT TONIGHT FOR ALL OF NORTHEAST IOWA AND
SOUTHWEST WISCONSIN. BE ALERT FOR THE POSSIBILITY OF FLOODING AND DO
NOT DRIVE ACROSS AREAS WHERE WATER COVERS THE ROAD.

THOMPSON