Severe Thunderstorm Warning 15, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
216 PM CDT WED APR 30 1997

FORECAST PROBLEMS TONIGHT: THUNDERSTORMS IN LOWER WI RIVER VALLEY...SNOW
POSSIBILITIES...AND WIND ADVISORIES.

EARLY AFTERNOON SURFACE ANALYSIS CONFIRMED 12Z ETA/NGM POSITION OF
POWERHOUSE LOW PRESSURE OVER SOUTHEAST IA. BAND OF RAIN WAS DEPICTED BY
AREAS 88D RADARS FROM THE LOW PRESSURE INTO NORTH CENTRAL WI IN ZONE OF
STRONG FRONTOGENETICAL FORCING. THUNDERSTORMS OVER EAST CENTRAL IA AND
NORTHWEST IL WERE BREAKING OUT IN ADVANCE OF MID LEVEL SHORT WAVE
BARRELLING THROUGH IA.  LATEST SURFACE RUC SUGGESTS THAT MORE UNSTABLE
AIR POISED AS FAR NORTH AS KDBQ...BUT QUICKLY STABALIZES IN SOUTHERN
WI. THEREFORE WOULD THINK THAT THUNDERSTORMS WOULD WEAKEN AS THEY MOVED
NORTHEAST...ALTHOUGH A FEW SMALL HAIL REPORTS AROUND KDBQ CAN NOT BE
RULED OUT THROUGH 22Z.

12Z ETA/NGM IN AGREEMENT OF TAKING THE SURFACE LOW TO SOUTH CENTRAL WI
THIS EVENING...THEN TO WESTERN LOWER MI LATE TONIGHT. STRONG
FRONTOGENTICAL FORCING SEEN SHIFTING INTO NORTHEAST WI BY
MIDNIGHT...THEN OUT OF THE PICTURE BY MORNING. FEEL THAT PRECIPITATION
WILL REMAIN IN CURRENT LARGE SWATH FROM NORTHEAST IA TO NORTH CENTRAL
WI THIS EVENING. Q-VECTOR CONVERGENCE FROM SHORT WAVE WILL ROTATE INTO
THE WISCONSIN RIVER VALLEY THIS EVENING CAUSING A BAND OF HEALTHY
THUNDERSTORMS FROM NEAR KDBQ-KMSN.

RAIN HAD CHANGED TO SNOW AS FAR SOUTH AS THE NORTHERN CHIPPEWA RIVER
VALLEY...ALONG THE ZERO TO TWO DEGREE 850 MB LINE AND WHERE BOUNDARY
LAYER TEMPERATURES WERE NEAR TWO TO THREE DEGREES. 12Z ETA HANDLED THIS
WELL AND SHIFTS THIS CRITICAL LINE SOUTH AND EAST ACROSS THE KARX
FORECAST AREA THIS EVENING. THEREFORE...RAIN SHOULD CHANGE TO SNOW IN
KMDZ REGION THIS EVENING WITH A SLUSHY ACCUMULATION POSSIBLE.
ELSEWHERE...PRECIPITATION SHOULD BE ON THE WANE AFTER MIDNIGHT BEFORE
THE COLDER AIR ARRIVES...SO NO ACCUMULATION...BUT PERHAPS SOME WET
FLAKES BEFORE IT ENDS.

850 MB WhINDS CRANK UP TO NEARLY 55 KNOTS THIS EVENING OVER THE AREA.
AFTER COORDINATION WITH KMPX/KGRB/KDMX/KMKX...WILL LIMIT A WIND
ADVISORY TO NORTHEAST IOWA AND THE LOWER WI RIVER VALLEY TONIGHT.

NGM MOS TEMPERATURES LOOK GOOD.

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IAZ008>011-018-019-029-030-WIZ054-055-061-302010-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
1106 AM CDT WED APR 30 1997

...A WIND ADVISORY CONTINUES FOR NORTHEAST IOWA AND EXTREME
SOUTHWEST WISCONSIN THIS AFTERNOON...

STRONG LOW PRESSURE OVER NORTHERN MISSOURI IS EXPECTED TO TRACK
INTO SOUTH CENTRAL WISCONSIN BY THIS EVENING. AS THE LOW PRESSURE
APPROACHES...A STRONG PRESSURE GRADIENT WILL EXIST OVER THE
ADVISORY AREA.  WIND GUSTS COULD APPROACH 50 MPH IN ISOLATED
LOCATIONS...BUT GENERALLY BE IN THE 20 TO 35 MPH RANGE. THE
STRONGEST WINDS WILL OCCUR LATE THIS AFTERNOON.

THOSE INTERESTED SHOULD STAY TUNED FOR UPDATES.

06

IAZ008>011-018-019-029-030-WIZ054-055-061-302010-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
1106 AM CDT WED APR 30 1997

...A WIND ADVISORY CONTINUES FOR NORTHEAST IOWA AND EXTREME
SOUTHWEST WISCONSIN THIS AFTERNOON...

STRONG LOW PRESSURE OVER NORTHERN MISSOURI IS EXPECTED TO TRACK
INTO SOUTH CENTRAL WISCONSIN BY THIS EVENING. AS THE LOW PRESSURE
APPROACHES...A STRONG PRESSURE GRADIENT WILL EXIST OVER THE
ADVISORY AREA.  WZIND GUSTS COULD APPROACH 50 MPH IN ISOLATED
LOCATIONS...BUT GENERALLY BE IN THE 20 TO 35 MPH RANGE. THE
STRONGEST WINDS WILL OCCUR LATE THIS AFTERNOON.

THOSE INTERESTED SHOULD STAY TUNED FOR UPDATES.

06