Severe Thunderstorm Warning 145, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
255 PM CDT FRI AUG 15 1997

FORECAST CONCERNS TONIGHT...CHANCES OF THUNDERSTORMS AND POTENTIAL
OF SEVERE STORMS.

AT 19Z...THE WARM FRONT WAS LOCATED FROM NEAR THE MN/ND/SD BORDER TO
KMSP-N OF KGRB.  COLD FRONT WAS IN EXTREME EASTERN ND AND SD...WITH
CONVECTION YET TO FIRE ALONG IT.  LACK OF...OR LIMITED CUMULUS
DEVELOPMENT OVER...WEST AND SOUTHWEST OF THE THE FORECAST AREA EARLY
THIS AFTERNOON AN INDICATION THAT 850-700 MB WARM ADVECTION WAS GOING
INTO WARMING AND CAPPING.  MUCH OF THE AREA WAS UNDER RIGHT FRONT QUAD
OF UPPER JET THIS AFTERNOON AS WELL.

12Z MODELS REASONABLY SIMILAR WITH THE SYNOPTIC SCALE...BUT SHOWING
DIFFERENCES IN THE MESOSCALE. THE COLD FRONT IS STILL EXPECTED TO
TRIGGER SOME TSRA AS IT PUSHES EAST INTO THE MORE MOIST/UNSTABLE AIR
LATE TODAY AND THIS EVENING.  ANY CONVECTION ALONG THE FRONT APPEARS AS
THOUGH IT WILL AFFECT MAINLY THE NORTH HALF OF THE FORECAST AREA THIS
EVENING WHERE THE CAP IS WEAKER.

MODIFIED 12Z SOUNDINGS AND 16/00Z MODEL SOUNDINGS INDICATING 1500-2500
J/KG OF CONVECTIVE ENERGY OVER THE AREA LATE THIS AFTERNOON INTO THIS
EVENING.  QUESTION IS...HOW MUCH HAS THE SUBSIDENCE ALOFT DUE TO THE
RIGHT FRONT QUAD OF THE JET AND THE 850-700MB WARMING REDUCED THE
INSTABILITY.  AHEAD OF THE FRONT...DEWPOINTS HAVE CLIMBED INTO THE
MID-UPPER 60S WITH TEMPERATURES IN THE LOW 80S...INDICATING PLENTY OF
SURFACE BASED INSTABILITY.  STRONG SPEED SHEAR PRESENT...WITH LITTLE
DIRECTIONAL SHEAR. IF CONVECTION DOES FIRE ALONG THE COLD FRONT...WOULD
HAVE TO BELIEVE SEVERE TSRA ARE POSSIBLE.

LATE TONIGHT...NGM/ETA INDICATING A COMBINATION OF 850-700MB WARM
ADVECTION AND THE RIGHT REAR QUAD OF THE JET COME TOGETHER OVER THE
FORECAST AREA FOR FORCING OF DEEP UPWARD VERICAL MOTION.  NGM FURTHER
NORTH/STORNGER WITH THIS.  SURFACE FRONTAL BOUNDARY TO STALL ACROSS
THE FORECAST AREA TOWARD MORNING FOCUSING CONVERGENCE IN THE BOUNDARY
LAYER...FOR A CHANCE OF LATE NIGHT SHRA/TSRA ACROSS THE FORECAST AREA.

NGM-FWC/AVN-FAN TEMPERATURE GUIDANCE SIMILAR FOR TONIGHT AND LOOK GOOD.
AVN POPS IN THE LIKELY CATEGORY TONIGHT...FWC POPS IN THE CHANCE
CATEGORY.  PREFER NGM POPS INf THE CHANCE CATEGORY AT THIS TIME DUE TO
THE APPERENT STRENGTH/DEVELOPMENT OF THE CAPPING OVER THE AREA.

RRS

MNZ079-086>088-094>096-WIZ032-033-160455-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
750 PM CDT FRI AUG 15 1997

...STRONG THUNDERSTORMS NORTH OF ROCHESTER AND NORTHWEST OF LA
CROSSE...

AS OF 750 PM...DOPPLER RADAR SHOWED STRONG THUNDERSTORMS FROM 60
MILES NORTHWEST OF LA CROSSE TO 40 MILES NORTHWEST OF ROCHESTER AND
THESE STORMS WERE MOVING EAST AT 35 MPH. IN SOUTHEAST
MINNESOTA...AREAS NORTH OF ROCHESTER WILL BE AFFECTED BY THESE
STORMS. IN WEST CENTRAL WISCONSIN...AREAS FROM NELSON...ALMA
AND MONDOVI TO OSSEO AND STRUM CAN EXPECT THESE STORMS.

REMEMBER...A TORNADO WATCH IS IN EFFECT THIS EVENING FOR SOUTHEAST
MINNESOTA AND PORTIONS OF WEST CENTRAL WISCONSIN. DAM4AGING WINDS AND
LARGE HAIL ARE POSSIBLE IN THESE AREAS. GO INDOORS IF A STORM
SHOULD AFFECT YOUR LOCATION.

THOMPSON

MNZ079-086>088-094>096-WIZ032-033-160455-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
750 PM CDT FRI AUG 15 1997

...STRONG THUNDERSTORMS NORTH OF ROCHESTER AND NORTHWEST OF LA
CROSSE...

AS OF 750 PM...DOPPLER RADAR SHOWED STRONG THUNDERSTORMS FROM 60
MILES NORTHWEST OF LA CROSSE TO 40 MILES NORTHWEST OF ROCHESTER AND
THESE STORMS WERE MOVING EAST AT 35 MPH. IN SOUTHEAST
MINNESOTA...AREAS NORTH OF ROCHESTER WILL BE AFFECTED BY THESE
STORMS. IN WEST CENTRAL WISCONSIN...AREAS FROM NELSON...ALMA
AND MONDOVI TO OSSEO AND STRUM CAN EXPECT THESE STORMS.

REMEMBER...A TORNADO WATCH IS IN EFFECT THIS EVENING FOR SOUTHEAST
MINNESOTA AND PORTIONS OF WEST CENTRAL WISCONSIN. DAMAGING WINDS AND
LARGE HAIL ARE POSSIBLE IN THESE AREAS. GO INDOORS IF A STORM
SHOULD AFFECT YOUR LOCATION.

THOMPSON

MNZ079-086>088-WIZ032-033-160235-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
830 PM CDT FRI AUG 15 1997

...A TORNADO WATCH IS IN EFFECT UNTIL 2AM...

AT 830 PM...DOPPLER RADAR SHOWED A CLUSTER OF STRONG THUNDERSTORMS
FROM 20 MILES NORTHWEST OF ROCHESTER TO 20 MILES SOUTHWEST OF EAU
CLAIRE WISCONSIN. THESE STORMS WERE MOVING EAST AND WILL CONTINUE
TO BRING VERY HEAVY RAIN AND FREQUENT LIGHTNING TO COMMUNITIES
NORTH OF ROCHESTER AND BETWEEN EAU CLAIRE AND LA CROSSE IN
WESTERN WISCONSIN.

WIND GUSTS OF 30 MPH WERE REPORTED AROUND LAKE CITY AT 820 PM
BY TRAINED STORM SPOTTERS.

REMEMBER...A TORNADO WATCH IS IN EFFECT.  IF STORMS INTENSIFY...
THEY MAY PRODUCE SEVERE WEATHER INCLUDING LARGE HAIL OR
DAMAGING WIND. TORNADOES CAN AND OCCASIONALLY DO FORM IN
SEVERE THUNDERSTORMS.

REMAIN ALERT FOR THREATENING WEATHER THIS EVENING.

SHEA

MNZ079-086>088-WIZ032-033-160235-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
830 PM CDT FRI AUG 15 1997

...A TORNADO WATCH IS IN EFFECT UNTIL 2AM...

AT 830 PM...DOPPLER RADAR SHOWED A CLUSTER OF STRONG THUNDERSTORMS
FROM 20 MILES NORTHWEST OF ROCHESTER TO 20 MILES SOUTHWEST OF EAU
CLAIRE WISCONSIN. THESE STORMS WERE MOVING EAST AND WILL CONTINUE
TO BRING VERY HEAVY RAIN AND FREQUENT LIGHTNING TO COMMUNITIES
NORTH OF ROCHESTER AND BETWEEN EAU CLAIRE AND LA CROSSE IN
WESTERN WISCONSIN.

WIND GUSTS OF 30 MPH WERE REPORTED AROUND LAKE CITY AT 820 PM
BY TRAINED STORM SPOTTERS.

REMEMBER...A TORNADO WATCH IS IN EFFECT.  IF STORMS INTENSIFY...
THEY MAY PRODUCE SEVERE WEhATHER INCLUDING LARGE HAIL OR
DAMAGING WIND. TORNADOES CAN AND OCCASIONALLY DO FORM IN
SEVERE THUNDERSTORMS.

REMAIN ALERT FOR THREATENING WEATHER THIS EVENING.

SHEA