Severe Thunderstorm Warning 40, NWS La Crosse, WI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
223 AM CDT MON MAY 18 1998

CONCERNS OF THE DAY ARE TEMPERATURES AND POSSIBLE LATE AFTERNOON
CONVECTION.

SUNDAY AFTERNOON HIGHS WERE IN THE LOWER 90S ACROSS THE MAJORITY OF THE
AREA...EXCEPT FOR MIDDLE 80S IN THE NORTHERN/CENTRAL WISCONSIN
COUNTIES. SURFACE ANALYSIS AT 06Z...HAD A LOW CENTER IN CENTRAL NORTH
DAKOTA WITH A DRY LINE EXTENDING TO THE SOUTH INTO NORTHWEST KANSAS...
AND A WARM FRONT EXTENDED WESTWARD INTO NORTHERN WISCONSIN.  IR2
SATELLITE IMAGERY CLEARLY SHOWS DRY LINE IN THE PLAINS STATES WITH THE
MOISTER AIR MOVING SLIGHTLY FURTHER NORTH AND WEST IN THE EARLY MORNING
HOURS. WATER VAPOR IMAGERY HAS SEVERAL WEAK CIRCULATIONS MOVING UP
AROUND THE WESTERN SIDE OF RIDGE OVER CENTRAL US.

ETA/NGM BOTH INDICATE A 2 TO 3 C RISE IN 850 MB TEMPERATURES OVER 24
HOUR PERIOD ENDING AT 00Z. ETA 2M DEWPOINT TEMPERATURES INDICATE THE
DRY LINE WILL NOT MAKE MUCH EASTWARD PROGRESS DURING THE DAY...BUT A
WEAK TROUGH MOVING OFF THE DRYLINE WILL APPROACH SOUTHEAST MINNESOTA/
NORTHEAST IOWA BY 00Z.  LOOKING AT MODEL FORECAST SOUNDINGS...THE ETA
MAY BE SLIGHTLY TOO MOIST AT THE SURFACE BUT THE NGM IS TOO DRY. BOTH
MODELS ARE GREATLY UNDERESTIMATING AFTERNOON HIGH TEMPERATURES BY 5 TO
10 DEGREES.  MODIFYING SOUNDINGS YIELD 4000 TO 6000 J/KG CAPE VALUES BY
00Z.  ETA DOES INDICATE CIN VALUES OF 50 TO 100 J/KG IN THE
REGION...BUT PROBABLY LOWER BASED ON EXPECTED WARMER TEMPERATURES. VERY
LITTLE WIND SHEAR IN THE SOUNDINGS FOR THE AFTERNOON.

NGM/AVN MOS GUIDANCE AND ETA 2M TEMPERATURES ARE ALL TOO LOW BASED ON
SUNDAY AFTERNOON HIGHS AND CONTINUED WEAK WARM AIR ADVECTION INTO THE
REGION.  EXPECT TEMPERATURES TO BE 5 TO 10 F WARMER THAN GUIDANCE
TEMPERATURES WHICH WILL BE IN RECORD RANGE FOR THE DATE IN WESTERN
WISCONSIN.  ATMOSPHERE WILL BE HIGHLY UNSTABLE BUT NO REAL DEFINABLE
TRIGGER MECHANISM. THE CAP WILL BE RELATIVELY SMALL BY LATE AFTERNOON
AND THE SURFACE TROUGH OR A WEAK SHORT WAVE MOVING OVER THE RIDGE MAY BE
ENOUGH TO TRIGGER CONVECTION. EVEN THOUGH WEAK SHEAR ENVIRONMENT... IF
STORMS DEVELOP...SUCCESSIVE STORMS MAY BE ABLE TO ORGANIZE ON OUTFLOW
BOUNDARIES GIVEN THE AMOUNT OF INSTABILITY.

NELSON

MNZ079-086-087-094-190245-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
912 PM CDT MON MAY 18 1998

...THUNDERSTORMS CONTINUE TO APPROACH SOUTHEAST MINNESOTA...

STRONG TO SEVERE THUNDERSTORMS ROLLING THROUGH THE TWIN CITIES
AREA CONTINUE TO BUILD TO THE SOUTHEAST TOWARD THE ROCHESTER AND
WABASHA AREA LATE THIS EVENING.

IT IS UNCERTAIN WHETHER THESE STORMS WILL HOLD TOGETHER...BUT
PEOPLE LIVING IN WABASHA...DODGE...MOWER AND OLMSTED COUNTIES
SHOULD MONITOR LATER WEATHER CONDITIONS FOR POSSIBLE WATCHES...
WARNINGS OR STATEMENTS.

A SEVERE THUNDERSTORM WATCH IS ALREADY IN EFFECT FOR DODGE AND
MOWER COUNTIES UNTIL 10PM.

IF YOU PLAN TO BE OUTDOORS THIS EVENING...CHECK THE LATEST WEATHER
INFORMATION AND KEEP AN EYE ON THE SKY.

SHEA

MNZ079-086-087-094-190245-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE LA CROSSE WI
912 PM CDT MON MAY 18 1998

...THUNDERSTORMS CONTINUE TO APPROACH SOUTHEAST MINNESOTA...

STRONG TO SEVERE THUNDERSTORMS ROLLING THROUGH THE TWIN CITIES
AREA CONTINUE TO BUILD TO THE SOUTHEAST TOWARD THE ROCHESTER AND
WABASHA AREA LATE THIS EVENING.

IT IS UNCERTAIN WHETHER THESE STORMS WILL HOLD TOGETHER...BUT
PEOPLE LIVING IN WABASHA...DODGE...MOWER AND OLMSTED COUNTIES
SHOULD MONITOR LATER WEATHER CONDITIONS FOR POSSIBLE WATCHES...
WARNINGS OR STATEMENTS.

A SEVERE THUNDERSTORM WATCH IS ALREADY IN EFFECT FOR DODGE AND
MOWER COUNTIES UNTIL 10PM.

IF YOU PLAN TO BE OUTDOORS THIS EVENING...CHECK THE LATEST WEATHER
INFORMATION AND KEEP AN EYE ON THE SKY.

SHEA