Damaging Winds in Wisconsin, September 12, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
335 AM CDT MON SEP 12 2005

.SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT

FORECAST FOCUS REMAINS ON TEMPERATURES AND RAIN CHANCES THROUGH THE
PERIOD.

AT 3 AM...SURFACE ANALYSIS HAD A COLD FRONT EXTENDING SOUTH FROM
MANITOBA THROUGH NORTHWEST CORNER OF MN...THROUGH CENTRAL SD...
EVENTUALLY HOOKING UP WITH A LOW OVER NORTHEAST CO. WATER VAPOR
IMAGERY SHOWING NICE SUBTROPICAL PLUME IN ADVANCE OF THE FRONTAL
BOUNDARY WITH SCATTERED CONVECTION STRETCHING ACROSS NEBRASKA THROUGH
NORTHERN MINNESOTA.

APPEARS 00Z 12SEP05 MODELS INITIALZIED FAIRLY WELL AND REMAIN IN
DECENT AGREEMENT THROUGH THE PERIOD.

FOR TODAY...LARGE UPPER LEVEL RIDGE BEGINS TO BUDGE EAST AS STRONG
SHORTWAVE TROUGH PUSHES EAST INTO THE NORTHERN PLAINS. WARM
AIR/MOISTURE ADVECTION WILL CONTINUE ACROSS THE AREA ADVANCE OF THE
SURFACE COLD FRONT MOVING SOUTHEAST ACROSS MINNESOTA. GFS AND NAM
PRODUCE CONVECTION AHEAD OF THE FRONT WITH THE AID OF A WEAK
EMBEDDED MID-LEVEL SHORTWAVE EJECTING NORTHEAST FROM THE CENTRAL
PLAINS INTO MINNESOTA. COLD FRONT CONTINUES TO SAG FURTHER SOUTHEAST
THROUGH THE AFTERNOON. THIS SHOULD FOCUS CONVECTION INTO THE
NORTHWEST PORTION OF THE FORECAST AREA. WILL NUDGE POPS UP BASED ON
THIS. WARM AIR ADVECTION WILL BE SOMEWHAT MITIGATED BY INCREASED
CLOUD COVER/PRECIPITATION. NONETHELESS...WITH WARM START THIS
MORNING...TEMPERATURES SHOULD HAVE NO PROBLEM REACHING INTO THE
MIDDLE AND UPPER 80S. NEXT ISSUE IS THE SEVERE THREAT. MLCAPE
INCREASES INTO THE 2000-2500J/KG RANGE ACROSS THE AREA AS THE 0-3KM
SHEAR VALUE INCREASE TO AROUND 30KT. APPEARS SEVERE THREAT WOULD BE
DAMAGING WINDS AND POSSIBLY SOME LARGE HAIL....MAINLY ACROSS THE
NORTHWEST.

THE COLD FRONT SAGS INTO NORTHWEST WISCONSIN TONIGHT. ANOTHER
EMBEDDED MID-LEVEL SHORTWAVE AND SURFACE LOW RIPPLES NORTHEAST ALONG
THE FRONTAL BOUNDARY. THIS PRODUCES A BETTER SLUG OF MOISTURE
TRANSPORT VIA STRENGTHENING LOW LEVEL JET INTO THE AREA. PRECIPTABLE WATER
VALUES INCREASE INTO THE 1.5 TO 2 INCH RANGE...SO SOME HEAVY RAIN
PRODUCING THUNDERTORMS POSSIBLE. THIS WOULD BE MAINLY ACROSS
NORTHWEST PORTION OF FORECAST AREA. WILL CONTINUE THE LIKLEY POPS
TONIGHT ACROSS THAT AREA BASED ON THIS. SEVERE THREAT WILL BE
DIMINISHED SOMEWHAT WITH INSTABILITIES DECREASING TO AROUND 1000J/KG.
0-3KM LAYER SHEAR STILL AROUND 35KT...SO DAMAGING WINDS MAY STILL BE
POSSIBLE WITH A FEW OF THE STORMS.

FRONT CONTINUES TO BUDGE SOUTHEAST ACROSS THE AREA ON TUESDAY.
APPEARS THERE MAY BE A BETTER CHANCE OF SEVERE CONVECTION ON TUESDAY
DUE TO COOLING ALOFT AND STRENGTHENING WINDS ALOFT WITH APPROACH OF
UPPER LEVEL TROUGH. LIKELY POPS ARE ALREADY IN THE GRIDS...WILL
LEAVE AS IS.

FRONT AND PRECIPITATION PUSH EAST OF THE AREA BY WED 12Z. A RETURN
TO MORE SEASONABLY COOLER TEMPERATURES IS IN STORE ON WEDNESDAY IN
COLD AIR ADVECTION. HIGH PRESSURE SETTLES INTO THE AREA WEDNESDAY
NIGHT...PROVIDING QUIET AND COOL CONDITIONS.

.LONG TERM...THURSDAY THROUGH SUNDAY

00Z 12SEP05 GFS BRINGS A SIGNIFICANT SHORTWAVE/SURFACE LOW INTO THE
NORTHERN PLAINS BY THURSDAY. APPEARS TO BE ENOUGH ISENTROPIC LIFT IN
ADVANCE OF THE WAVE TO WARRANT A SMALL CHANCE OF SHRA/TS ACROSS THE
WEST. PATTERN BECOMES MORE ZONAL THROUGH THE REST OF THE PERIOD.
EMBEDDED SHORTWAVES WITHIN THIS FLOW MAY PRODUCE SOME PRECIPITATION
FROM TIME TO TIME. WILL LEAVE DRY FOR NOW AND LET THE DAY SHIFT
ASSESS FURTHER.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

DAS

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE LA CROSSE WI
1258 PM CDT MON SEP 12 2005

IAZ008>011-018-019-029-030-MNZ079-086>088-094>096-WIZ017-029-
032>034-041>044-053>055-061-131100-
ADAMS-ALLAMAKEE-BUFFALO-CHICKASAW-CLARK-CLAYTON-CRAWFORD-DODGE-
FAYETTE-FILLMORE-FLOYD-GRANT-HOUSTON-HOWARD-JACKSON-JUNEAU-
LA CROSSE-MITCHELL-MONROE-MOWER-OLMSTED-RICHLAND-TAYLOR-TREMPEALEAU-
VERNON-WABASHA-WINNESHIEK-WINONA-
1258 PM CDT MON SEP 12 2005

CORRECTED TYPOGRAPHICAL ERRORS

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PARTS OF NORTHEAST IOWA...
SOUTHEAST MINNESOTA...AND SOUTHWEST INTO CENTRAL WISCONSIN.

.DAY ONE...THIS AFTERNOON AND TONIGHT

ONE WAVE OF SHOWERS AND THUNDERSTORMS WILL LIFT NORTHEAST ACROSS
AREAS WEST OF SAINT CHARLES IOWA TO WINONA MINNESOTA AND OSSEO
WISCONSIN EARLY THIS AFTERNOON. INSTABILITY AND WINDS ALOFT ARE NOT
FAVORABLE FOR ANY OF THESE THUNDERSTORMS TO REACH SEVERE LIMITS.

A COLD FRONT FROM NORTHEAST MINNESOTA INTO EASTERN SOUTH DAKOTA WILL
CONTINUE TO MOVE SLOWLY SOUTHEAST THIS AFTERNOON AND TONIGHT. A
CONTINUED FLOW OF WARM...MOIST...AND UNSTABLE AIR INTO THE FRONT
WILL GENERATE THUNDERSTORMS ACROSS CENTRAL MINNESOTA INTO EASTERN
SOUTH DAKOTA AND NORTHWEST IOWA THIS AFTERNOON. INSTABILITY AND
WINDS ALOFT WILL CONTINUE TO INCREASE THIS AFTERNOON...ESPECIALLY
OVER EASTERN SOUTH DAKOTA...SOUTHWEST MINNESOTA AND NORTHWEST IOWA.
STRONG TO SEVERE THUNDERSTORMS ARE EXPECT DEVELOP IN THESE AREAS
DURING THE MID TO LATE AFTERNOON HOURS...THEN MOVE EAST OR NORTHEAST
DURING THE LATE AFTERNOON AND EVENING HOURS. DEPENDING ON THE TRACK
AND EVOLUTION OF WHAT SHOULD BE SEVERAL CLUSTERS OF THUNDERSTORMS...
THERE IS A SLIGHT RISK OF SEVERE STORMS ALONG AND NORTH OF A LINE
FROM CHARLES CITY IOWA TO LA CROSSE AND NEILLSVILLE WISCONSIN. THE
MAIN THREAT TIME APPEARS TO BE 6 PM TO MIDNIGHT THIS EVENING. THE
PRIMARY THREAT WILL BE LARGE HAIL...BUT DAMAGING WINDS ARE ALSO
POSSIBLE. IN ADDITION...THE VERY WARM AND MOIST AIRMASS OVER THE
AREA...ANY STRONGER STORMS WILL BE CAPABLE OF PRODUCING LOCALLY
HEAVY RAINFALL.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SHOWERS AND THUNDERSTORM CHANCES WILL CONTINUE ACROSS THE AREA
TUESDAY AND TUESDAY NIGHT AS THE COLD FRONT SLOWLY MAKES ITS WAY
ACROSS THE OUTLOOK AREA. AVAILABLE MOISTURE AND FAVORABLE WINDS
ALOFT POINT TO A SLIGHT RISK OF SEVERE STORMS DURING THIS
TIMEFRAME...SOUTH OF A CHARLES CITY IOWA TO LA CROSSE AND WISCONSIN
RAPIDS WISCONSIN LINE. INSTABILITY REMAINS IN QUESTION FOR TUESDAY
AFTERNOON AND EVENING...AS PERSISTENT SHOWERS THROUGH MUCH OF
TUESDAY MAY KEEP TEMPERATURES FROM WARMING MUCH AND INSTABILITY FROM
DEVELOPING. IF SOME SUNSHINE DOES BREAK THROUGH...ALLOWING FOR MORE
DESTABILIZATION...LARGE HAIL AND DAMAGING WINDS WOULD BE THE MAIN
SEVERE THREATS...BUT ISOLATED TORNADOES WOULD ALSO BE POSSIBLE RIGHT
NEAR THE COLD FRONT AS IT MOVES SOUTHEAST ACROSS THE AREA.

THE NEXT CHANCE FOR THUNDERSTORMS WILL COME THURSDAY AS ANOTHER WEAK
DISTURBANCE MOVES ACROSS SOUTHERN CANADA. THE BEST CHANCE FOR RAIN
WILL BE NORTH OF A LINE FROM AUSTIN AND WINONA MINNESOTA...TO
NEILLSVILLE WISCONSIN. IT DOES NOT APPEAR AT THIS TIME THAT ANY OF
THESE STORMS WILL BECOME SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY NEEDED THIS LATE THIS AFTERNOON AND THIS
EVENING...MAINLY BETWEEN 6 PM AND MIDNIGHT...OVER PARTS OF NORTHEAST
IOWA...SOUTHEAST MINNESOTA AND WESTERN WISCONSIN. SPOTTERS MAY BE
NEEDED AGAIN TUESDAY AFTERNOON AND EVENING OVER PARTS OF NORTHEAST
IOWA AND SOUTHWEST INTO CENTRAL WISCONSIN. SPOTTER GROUPS AND
EMERGENCY MANAGERS WILL WANT TO STAY TUNED TO THE LATEST WEATHER
INFORMATION AND FORECASTS RELATING TO THE SEVERE WEATHER POTENTIAL.

.EMERGENCY MANAGEMENT COORDINATION...

NO CALL IS SCHEDULED.

RRS