Severe Thunderstorm Warning 28, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
130 PM CDT FRI MAY 15 1998

SURFACE ANALYSIS PLACES LOW PRESSURE ACROSS SOUTHEAST NEBRASKA WITH
MAIN SURFACE CONVERGENCE FROM THE EASTERN DAKOTAS SOUTH INTO THE LOW.
SHORTWAVE ACROSS EASTERN NEBRASKA IS FORECAST TO BECOME NEGATIVELY
TILTED AS IT MOVES TOWARDS THE UPPER MISSISSIPPI VALLEY THIS EVENING.

12Z ETA LOOKS TO HAVE A DECENT HANDLE ON THE CURRENT SITUATION AND HAVE
FOLLOWED.  QG FORCING IN THE 700 MB TO 500 MB LAYER WOULD SUGGEST THAT
WAVE DYNAMICS FROM THE VORTICITY CENTER BECOMES STRONGEST ACROSS THE ARX
CWFA LATE THIS AFTERNOON INTO THE EVENING HOURS.  THE WAVE SHOULD HELP
PUSH THE COLD FRONT CURRENTLY ACROSS THE EASTERN DAKOTAS TO NEAR THE
MISSISSIPPI RIVER BY MIDNIGHT.  THE ATMOSPHERE SHOULD BE JUICED GIVEN
SURFACE BASED CAPES OF 2000-3000 J/KG AND SURFACE DEWPOINTS IN THE
UPPER 60S TO AROUND 70.

0-3KM SHEAR PROFILES OF 30-40KTS WOULD SUGGEST SQUALL LINES ARE STILL
POSSIBLE...HOWEVER WOULDNT RULE OUT SUPERCELLS EITHER ESPECIALLY EARLY
ON SINCE SHEAR PROFILES STILL INCREASE SLIGHTLY OUT TO 6KM. THE BOTTOM
LINE IS THAT THE ATOMPSHERE REMAINS JUICED AND WITH THE MODERATE RISK
FROM SPC WILL KEEP SEVERE WEATHER A POSSIBILITY ESPECIALLY LATE THIS
AFTERNOON AND EVENING.

NGM GUIDANCE VALUES LOOK LIKE A GOOD PLACE TO START WITH TEMPERATURES.

KING

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-
032>034-041>044-053>055-061-160600-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LA CROSSE WI
1230 PM CDT FRI MAY 15 1998

...THERE IS A MODERATE RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING OVER ALL OF WEST AND SOUTHWEST WISCONSIN...NORTHEAST IOWA AND
SOUTHEAST MINNESOTA...

AN VIGOROUS UPPER LEVEL DISTURBANCE OVER EASTHERN NEBRASKA TRIGGERED
STRONG TO SEVERE THUNDERSTORMS ACROSS MUCH OF WESTERN IOWA THIS MORNING.
MANY OF THESE STORMS PRODUCED DAMAGING WINDS.  THE FIRST LINE OF STORMS
HAD WEAKENED AS IT MOVED NORTH DURING THE LATE MORNING...BUT MORE
STRONG TO SEVERE STORMS HAD ALREADY DEVLOPED IN SOUTHWEST IOWA.

THE DISTRUBANCE IS EXPECTED TO MOVE INTO CENTRAL MINNESOTA BY THIS
EVENING.  AS IT DOES...IT WILL TRIGGER MORE STRONG TO SEVERE STORMS
ACROSS MUCH OF THE UPPER MIDWEST THROUGH THIS EVENING.   ALTHOUGH THE
ENTIRE AREA IS UNDER A MODERATE RISK OF SEVERE STORMS...IT APPEARS THE
GREATER RISK IS WEST OF THE MISSISSIPPI RIVER CLOSER TO THE TRACK OF
THE UPPER DISTURBANCE.

A SEVERE THUNDERSTORM WATCH IS ALREADY IN EFFECT UNTIL 3 PM FOR AREAS
WEST OF ROUGHLY A RED WING MN TO MASON CITY IA LINE...ACROSS MOST OF
SOUTHERN MINNESOTA AND NORTHER IOWA.

SPOTTER ACTIVATION IS LIKELY LATER THIS AFTERNOON AND EVENING.
ACTIVATION BY MID AFTERNOON MAY BE NEEDED FOR SOUTHEAST MINNESOTA AND
NORTHEAST IOWA.  ACTIVATION IN WESTERN WISCONSIN IS NOT ANTICIPATED
UNTIL LATE AFTERNOON...AND INTO THE EARLY EVENING HOURS FOR CENTRAL
WISCONSIN.

RRS