Severe Thunderstorm Warning 40, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
256 AM CDT MON MAY 14 2001

MAIN FORECAST PROBLEM WILL BE ASCERTAINING AMPLITUDE OF LOW LEVEL
FORCING/BOUNDARY LOCATION AND INTERACTION FOR CONVECTIVE
PRECIPITATION OVER THE NEXT FEW DAYS.

SUBJECTIVE ANALYSIS AT 05Z SHOWS LOWS PRESSURE ACROSS NORTHWEST
SOUTH DAKOTA.  A WARM FRONT EXTENDS FROM THE LOW...SOUTHEAST
THROUGH SOUTH DAKOTA-EXTREME NORTHEAST NEBRASKA-SOUTHWEST IOWA-NORTH-
CENTRAL MISSOURI.  DEWPOINTS IN THE VICINITY OF THIS BOUNDARY ARE IN
THE LOWER 60S.

REGIONAL RADARS SHOWING SHOWERS AND THUNDERSTORMS CONTINUING ON THE
ELEVATED SIDE OF THE BOUNDARY...MAINLY ALONG EASTERN IOWA AND WESTERN
ILLINOIS.  THIS IS IN THE AREA OF MAXIMUM LOW LEVEL THETA-E
ADVECTION.  ALSO AIDING IN THE CONVECTION IS SOME UPPER LEVEL FORCING
ASSOCIATED WITH THE JET NOTED ON WATER VAPOR AND IN THE PROFILER
DATA.

A SECOND AREA OF SHOWERS AND THUNDERSTORMS IS ALSO NOTED ACROSS
SOUTHERN ONTARIO...ENTERING NORTHERN MINNESOTA. THIS ACTIVITY
CONTINUES TO MOVE SOUTHEAST AND IS ALONG A WEAK SURFACE BOUNDARY AS
WELL.

IN THE SHORT TERM...EXPECT THE SURFACE FRONT TO GRADUALLY MOVE
NORTHEAST.  AS THIS OCCURS...MAIN LOW LEVEL FORCING MECHANISM
WILL CAUSE CONVECTION TO DEVELOP ACROSS THE FORECAST AREA THIS
MORNING.  ALSO...SECOND AREA OF CONVECTION MAY MAKE IT INTO THE
NORTHERN ZONES FROM NORTHERN MINNESOTA.  WILL CONTINUE MID-RANGE
PRECIPITATION CHANCES DESPITE LOW CONFIDENCE.

AS THE FRONT CONTINUES NORTHEAST...STRONG CAPPING INVERSION BEHIND
THIS FRONT WILL BRING SUNNY SKIES AND WARM TEMPERATURES INTO THE
FORECAST AREA THIS AFTERNOON.  BY EVENING...MOISTURE TRANSPORT
MAXIMUM DEVELOPS...CAUSING THUNDERSTORM DEVELOPMENT NORTH OF THE
FRONT. CORFIDI VECTORS SUGGESTS THIS CONVECTION WILL MOVE SOUTH...
DOWN INTO THE FORECAST AREA.  THIS WILL PUSH THE BOUNDARY BACK INTO
THE FORECAST AREA.

THIS BOUNDARY SHOULD REMAIN ACROSS THE FORECAST AREA TUESDAY.
MODIFIED FORECAST SOUNDINGS INDICATE MODERATE INSTABILITY WILL
LITTLE CONVECTIVE INHIBITION.  THINK THAT THUNDERSTORMS WILL FIRE
ALONG THIS BOUNDARY LATE IN THE DAY TUESDAY.

NEXT UPPER LEVEL DISTURBANCE WILL MOVE THROUGH THE UPPER MISSISSIPPI
RIVER VALLEY TUESDAY NIGHT.  SHOWERS AND THUNDERSTORMS SHOULD
ACCOMPANY THIS BOUNDARY...AS THERE IS ADEQUATE MOISTURE AND FORCING.

AS FAR AS THE SEVERITY OF THE STORMS...THIS MORNINGS THREAT SHOULD
BE HAIL...AS STORMS WILL BE QUITE ELEVATED.  THIS IS THE SAME FOR
TONIGHT AS WELL.  TUESDAY COULD BE A DIFFERENT STORY GIVEN THE
CAPPING INVERSION IS LESS.  COULD REALIZE SOME SHEAR ALONG THE
BOUNDARY...HOWEVER HAIL SHOULD BE THE MAIN THREAT.  WEAK
ENVIRONMENTAL FLOW SUGGESTS FLOODING MAY BE A PROBLEM SHOULD STORMS
DEVELOP.

CORDINATED WITH MKX.

.LSE...NONE.

KRC

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-032>034-
041>044-053>055-061-142000-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LA CROSSE WI
430 AM CDT MON MAY 14 2001

HAZARD - THUNDERSTORMS...POTENTIAL FOR HAIL AND HEAVY RAIN.

TIMING - FROM 5 AM TO 10 AM...FROM 11 PM TO 10 AM TUESDAY MORNING.

LOCATION - NORTHEAST IOWA...SOUTHEAST MINNESOTA...AND WEST AND
CENTRAL WISCONSIN.

DISCUSSION - SHOWERS AND THUNDERSTORMS HAVE DEVELOPED OVER EASTERN
IOWA EARLY THIS MORNING. THIS ACTIVITY WAS NORTH OF A WARM
FRONT...WHICH STRETCHED FROM NORTH DAKOTA TO EXTREME NORTHERN
MISSOURI EARLY THIS MORNING. THE STORMS WILL DEVELOP TO THE NORTH
AS THE MORNING WEARS ON...INTO PORTIONS OF NORTHEAST IOWA AND
SOUTHWEST WISCONSIN. CHANCES WILL BE SMALLER NORTH OF THERE. THE
STORMS WILL THEN MOVE EAST FOR THE REST OF THE MORNING...WEAKENING
AS THEY EXIT INTO EASTERN WISCONSIN BY NOON. SOME SMALL HAIL AND
HEAVY RAIN WILL BE POSSIBLE WITH THE STORMS THIS MORNING.

THE WARM FRONT WILL MOVE NORTH TODAY...EXTENDING ACROSS CENTRAL
MINNESOTA AND THROUGH CENTRAL WISCONSIN LATE TONIGHT. A SURGE OF
WARM AND MOIST AIR NORTH OF THE BOUNDARY WILL HELP DESTABILIZE THE
ATMOSPHERE AND PROVIDE FUEL FOR THUNDERSTORM DEVELOPMENT. SO...THE
FRONT WILL CONTINUE TO SERVE AS THE FOCUS FOR MORE THUNDERSTORM
DEVELOPMENT LATE TONIGHT. THE STORMS SHOULD DEVELOP SHORTLY BEFORE
MIDNIGHT OVER NORTHEAST MINNESOTA AND NORTHERN WISCONSIN...AND THEN
SLIDE TO THE SOUTHEAST. THERE IS THE POTENTIAL FOR LARGE HAIL WITH
SOME OF THESE STORMS...ALONG WITH HEAVY RAINS PRODUCING FLOODING
PROBLEMS.

SPOTTER INFORMATION - SPOTTER ACTIVATION WILL PROBABLY NOT BE NEEDED
THIS MORNING...BUT MAY BE NECESSARY LATER TONIGHT.

RIECK