Hail in Iowa, June 19, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
422 AM CDT WED JUN 19 2002

MAIN FORECASTS CONCERNS THIS MORNING DEALS WITH THE SEVERE
THUNDERSTORMS CURRENTLY LOCATED JUST WEST OF OUR NORTHEAST IOWA AND
SOUTHEAST MINNESOTA COUNTIES...WHERE THE MCS OVER NORTHWEST SOUTH
DAKOTA WILL END UP LATER ON THIS MORNING...AND THE THREAT OF MORE
SEVERE WEATHER TONIGHT.

OVERNIGHT...WE HAVE BEEN CAREFULLY MONITORING A LINE OF
THUNDERSTORMS THAT DEVELOPED OVER SOUTH CENTRAL MINNESOTA AND NORTH
CENTRAL IOWA. THIS LINE IS MOVING EAST AT ABOUT 30 MPH. THERE HAVE
BEEN A COUPLE OF WARNINGS WITH THIS LINE FROM TIME TO TIME. LOOKING
AT THE WATER VAPOR IMAGERY...A 40 KNOT 850 MB JET IS FEEDING THESE
THUNDERSTORMS FROM THE WEST. THE WET BULB ZERO HEIGHTS ARE RUNNING
AROUND 13,000 FEET THIS MORNING. AS A RESULT...NOT SEEING ANY SEVERE
SIZE HAIL UNTIL 50 DBZ CORE REACHES AT LEAST 39,000 FEET. THE
WIND THREAT WITH THESE THUNDERSTORMS IS RATHER LIMITED...BECAUSE THE
THUNDERSTORMS ARE SOMEWHAT ELEVATED AND THE STORM MOTION WITH THIS
LINE IS SOMEWHAT SLOW. WITH PRECIPITABLE WATER VALUES RUNNING AROUND
1.5 INCHES...THESE THUNDERSTORMS WILL QUITE EFFICIENT AT PRODUCING
VERY HEAVY RAIN. RAINFALL RATES WILL BE IN THE 1.5 TO 2.5 INCH RANGE
PER HOUR IN THE STRONGEST STORMS.

AFTER THIS LINE MOVES THROUGH...OUR ATTENTION WILL BE ON THE MCS
LOCATED OVER NORTHWEST SOUTH DAKOTA AND SOUTHEAST NORTH DAKOTA. THIS
MCS IS ASSOCIATED WITH THE LEFT ENTRANCE REGION OF A 500 MB JET.
850 MB MOISTURE TRANSPORT VECTORS SHOW THAT THIS SYSTEM WILL MOVE
EAST ALONG THE NORTH DAKOTA AND SOUTH DAKOTA LINE EARLY THIS
MORNING...AND THE CORFIDI VECTORS SUGGEST THAT THIS SYSTEM WILL MAKE
A TURN SOUTHWARD AS IT MOVES EAST INTO MINNESOTA. THIS TURN WILL
OCCUR AS THE COMPLEX ROUNDS THE THERMAL RIDGE. THE QUESTION IS WHERE
EXACTLY THIS WILL OCCUR IN MINNESOTA. LOOKING AT THE 06Z MESO
ETA...IT LOOKS LIKE THIS WILL OCCUR OVER EASTERN MINNESOTA AND
NORTHWEST WISCONSIN. IF THIS OCCURS AS FORECASTED...THIS COMPLEX
WOULD DROP EAST OF THE FORECAST AREA. HOWEVER...WE WILL HAVE TO
WATCH THIS COMPLEX CLOSELY TO MAKE SURE THAT THIS OCCURS.

THIS AFTERNOON...WARM AIR BETWEEN 700 MB AND 850 MB MOVES INTO MUCH
OF THE AREA. THIS WILL ACT AS A CAP PREVENTING ADDITIONAL
THUNDERSTORMS FROM POPPING UP THIS AFTERNOON. AS A RESULT...I WENT
DRY FOR THIS AFTERNOON. WITH PARTLY SUNNY SKIES...THIS WILL ALLOW
THE CAPES TO CLIMB TO 3000 J/KG AND LIFTED INDICES TO -7C BY THIS
EVENING. AS THE COLD FRONT MOVES INTO THIS RATHER UNSTABLE AIRMASS...
SCATTERED SUPER CELLS WILL LIKELY DEVELOP ALONG AND AHEAD OF THIS
FRONT. THESE THUNDERSTORMS WILL LIKELY EVOLVE INTO A LINE. AS A
RESULT...WIND WILL BE A THREAT TONIGHT. IN ADDITION...SOME OF
THUNDERSTORMS MAY PRODUCE SEVERE HAIL. THE SEVERE WEATHER THREAT AT
THIS TIME LOOKS LIKE IT WILL BE AFTER 10 PM.

.LSE...NONE.

BOYNE