Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 241708
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1208 PM CDT FRI JUL 24 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 204 AM CDT FRI JUL 24 2015

MOST IMMEDIATE CONCERN IS THE ONGOING CONVECTION FROM NORTHWEST
INTO SOUTH-CENTRAL MN...MOVING DUE EAST-NORTHEAST AROUND 30 MPH.
PRIMARY INSTABILITY AXIS IS WELL TO THE WEST ACROSS THE EASTERN
DAKOTAS AND THINK CONVECTION WILL OUTRUN THIS MOST UNSTABLE AIR
MASS AS THE RESPONSIBLE SHORT-WAVE ALOFT LIFTS INTO THE WESTERN
GREAT LAKES. THE STRONGEST OF THESE STORMS...SOME OF WHICH HAVE
BEEN SEVERE...SHOULD REMAIN NORTH AND WEST OF THE FORECAST AREA
ALONG NOSE OF 850 HPA JET/MOISTURE TRANSPORT. CLOSER TO THE UPPER
MS RIVER VALLEY...EXPECT AN AREA OF SHOWERS AND THUNDERSTORMS TO
MOVE THROUGH MAINLY BETWEEN 4 AND 9 AM. PRIMARY THREATS WILL BE
LIGHTNING AND HEAVY RAIN...ALTHOUGH CANNOT RULE OUT SOME GUSTY
WINDS.

FOR THE REST OF THE DAY...EXPECT MOSTLY DRY CONDITIONS ACROSS THE
THE UPPER MS RIVER VALLEY. TEMPERATURES WILL RISE INTO THE MID
80S AND WITH DEW POINT TEMPERATURES IN THE MID 60S TO LOWER
70S...TODAY WILL FEEL MUCH MORE HUMID THAN EARLIER THIS WEEK. WITH
HEAT/HUMIDITY...0-3 KM MUCAPE QUICKLY BUILDS TO BETWEEN 1000 TO
3000 J/KG...BUT MODEST MID-LEVEL CAP SHOULD INITIALLY KEEP STORMS
IN CHECK. THAT IS UNTIL A WEAKENING COLD FRONT DROPS INTO THE
REGION LATE THIS AFTERNOON/EVENING. SURFACE CONVERGENCE ALONG THE
FRONT IS UNIMPRESSIVE...BUT THERE IS A WEST-EAST ORIENTED JET
STREAK THAT MOVES INTO CENTRAL MN/NORTHERN WI...RESULTING IN 0 T0
6 KM BULK SHEAR VALUES UP TO 40 KTS. LATEST SUITE OF MESO MODELS
ONLY SHOWING SCATTERED THUNDERSTORM DEVELOPMENT ALONG AND AHEAD OF
THE FRONT LATE THIS AFTERNOON/EVENING...SO SOMEWHAT UNCERTAIN ON
COVERAGE...BUT ANY THUNDERSTORMS THAT DO DEVELOP COULD QUICKLY
BECOME SEVERE. PRIMARY THREATS WOULD BE LARGE HAIL...DAMAGING WIND
AND HEAVY RAIN. THUNDERSTORM CHANCES DROP TO ZERO BEHIND THE
FRONT OVERNIGHT WITH TEMPERATURES DROPPING INTO THE 60S.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 204 AM CDT FRI JUL 24 2015

NOT MUCH TIME SPENT ON THE LONG TERM GIVEN MORE IMMEDIATE CONVECTIVE
CONCERNS...BUT WILL SEE ADDITIONAL SHOWER AND THUNDERSTORM CHANCES
SUNDAY/MONDAY AS A SERIES OF WEAK SHORT-WAVES MOVE THROUGH BUILDING
RIDGE ALOFT. MORE IMPRESSIVE TROUGH MOVES INTO THE NORTHERN PLAINS
ON TUESDAY...BRINGING ADDITIONAL THUNDERSTORM CHANCES AHEAD OF A
COLD FRONT WHICH WILL SWEEP ACROSS THE REGION TUESDAY NIGHT.
TEMPERATURES THROUGH TUESDAY WILL BE WARM WITH DAILY HIGHS AT
LEAST IN THE MID 80S WITH SOME AREAS APPROACHING 90 DEGREES BY
MONDAY/TUESDAY. DEW POINT TEMPERATURES WILL ALSO BE RATHER
HIGH...RESULTING IN HUMID CONDITIONS. TEMPERATURES/HUMIDITY
WEDNESDAY THROUGH FRIDAY WILL BE LOWER IN THE WAKE OF TUESDAY
NIGHT/S COLD FRONT. ALSO NOT EXPECTING MUCH IN THE WAY OF
PRECIPITATION THE LATTER HALF OF THE WEEK GIVEN DOMINANT SURFACE
HIGH PRESSURE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1208 PM CDT FRI JUL 24 2015

SKIES ARE BEGINNING TO CLEAR OUT BEHIND THE EARLY MORNING ROUND OF
SHOWERS AND STORMS AND EXPECT TO SEE SCATTERED OR SOME BROKEN MID
LEVEL CLOUDS OVER THE AREA. THE COLD FRONT IS STILL WEST OF THE
AREA AND IS EXPECTED TO SLIDE THROUGH DURING THE EVENING HOURS.
THE CONCERN BECOMES WHETHER ADDITIONAL STORMS WILL DEVELOP AS THE
COLD FRONT COMES IN. BOTH THE 24.12Z NAM AND 24.15Z RAP FORECAST
SOUNDINGS SUGGEST A CAP WILL DEVELOP THIS AFTERNOON AHEAD OF THE
FRONT AS WARM AIR ALOFT MOVES IN AND THAT THIS CAP WILL REMAIN IN
PLACE UNTIL AFTER THE FRONT MOVES THROUGH. THE BEST CHANCES FOR
THE CAP TO BE DISPLACED LOOK TO BE OVER CENTRAL INTO SOUTHWEST
WISCONSIN. BASED ON THIS...PLAN TO SHOW SOME LATE AFTERNOON
CUMULUS CLOUDS DEVELOPING THAT COULD GO TO A VFR CEILING FOR A
WHILE BUT WILL NOT INCLUDE ANY MENTION OF SHOWERS OR STORMS. SKIES
SHOULD BECOME CLEAR FAIRLY QUICKLY BEHIND THE FRONT WITH THE WINDS
DROPPING UNDER 10 KNOTS FROM THE NORTHWEST.

&&

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

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...04



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