Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 291726
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1226 PM CDT WED JUL 29 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 303 AM CDT WED JUL 29 2015

AT 3 AM...A COLD FRONT EXTENDED FROM MARQUETTE MICHIGAN TO VINTON
IOWA. AHEAD OF THIS FRONT...THE SURFACE DEW POINTS WERE AROUND
70. MEANWHILE IN THE WAKE OF FRONT...DEW POINTS RANGED FROM THE
MID 50S TO MID 60S. SCATTERED SHOWERS LINGERED ACROSS SOUTHERN
CLAYTON COUNTY IN NORTHEAST IOWA AND GRANT COUNTY IN SOUTHWEST
WISCONSIN. WITH THE MESO MODELS SHOWING THAT THESE SHOWERS WILL
END BY 29.10Z...THEY WERE NOT INCLUDED IN THE TAFS.

WITH WEAK TO MODERATE SUBSIDENCE IN THE WAKE OF THIS FRONT AND
DOWNSLOPE OFF THE PLAINS WILL KEEP SKIES MAINLY SUNNY TODAY. WITH
DIURNAL MIXING...MOST AREAS WILL MIX UP TO 800 MB. THIS WILL ALLOW
WIND GUSTS OF 25 TO 30 KNOTS TO MIXED TO THE SURFACE AT TIMES
BETWEEN 29.16Z AND 30.01Z.

WITH SOUNDINGS SHOWING VERY DRY BELOW 800 MB AND ONLY A VERY
SHALLOW LAYER OF LIGHT WINDS...NOT ANTICIPATING ANY FOG TONIGHT.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 303 AM CDT WED JUL 29 2015

THROUGHOUT MUCH OF TIME PERIOD...THE MODELS CONTINUE TO SHOW A
SERIES OF WEAK SYSTEMS ROUNDING THE WESTERN RIDGE. DUE TO MODERATE
TO STRONG FLOW ALOFT...THESE SYSTEM WILL PERIODICALLY MOVE THROUGH
THE REGION EVERY 12 TO 24 HOURS. INITIALLY FROM THURSDAY INTO
SATURDAY...THE AIR MASS LOOKS TO PARCHED IN THE UPPER MISSISSIPPI
RIVER VALLEY FOR ANY PRECIPITATION TO OCCUR.

WITH SOUNDINGS CONTINUING TO SHOW VERY DRY BELOW 800 MB AND ONLY
A VERY SHALLOW LAYER OF LIGHT WINDS...NOT ANTICIPATING ANY FOG
ON EITHER THURSDAY NIGHT OR FRIDAY MORNING.

ON SATURDAY NIGHT AND SUNDAY MORNING...THE MODELS HAVE A BIT MORE
CONSISTENCY THAT MODERATE 850 MOISTURE TRANSPORT AHEAD OF AN
APPROACHING SHORT WAVE WILL RESULT IN MESOSCALE CONVECTIVE
COMPLEX DEVELOPING OVER SOUTH DAKOTA DURING THE LATE AFTERNOON AND
EVENING...AND THIS WILL TRACK INTO THE AREA DURING THE NIGHT.
WHILE THE 0-3 KM SHEAR WILL RANGE FROM 30 TO 35 KNOTS /FAVORABLE
FOR LINE OR LINES OF STORMS/...THE 0-1 KM CAPES WEST OF THE
MISSISSIPPI RIVER WILL ONLY BE UP TO 1000 J/K...SO THERE ARE STILL
QUESTIONS ON WHETHER THERE WILL BE ENOUGH INSTABILITY FOR ANY
SEVERE WEATHER.

ADDITIONAL STORM CHANCES WILL BE POSSIBLE FROM SUNDAY NIGHT INTO
TUESDAY. HOWEVER TIMING REMAINS A QUESTION...SO DID NOT MAKE TOO
ANY MODIFICATIONS FROM THE MODEL CONSENSUS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1226 PM CDT WED JUL 29 2015

GOOD VFR CONDITIONS THIS AFTERNOON THRU THU...WITH P6SM SKC EXPECTED
THRU THE PERIOD. THIS AS CAN HIGH PRESSURE AND A SEASONABLY DRY
AIRMASS FROM THE NORTHERN PLAINS SPREADS INTO THE UPPER MIDWEST.
TIGHTER PRESSURE GRADIENT OVER THE AREA THIS AFTERNOON ALONG WITH
DIURNAL MIXING TO NEAR 6K FT...IS RESULTING IN BRISK/GUSTY WEST TO
NORTHWEST WINDS OF 15-25KT G25-35KT. THESE WINDS WILL DIMINISH WITH
LOSS OF DIURNAL HEATING/MIXING LATE THIS AFTERNOON/EARLY THIS
EVENING...WITH WEST TO SOUTHWEST WINDS OF 8-12KTS OVERNIGHT INTO THU
MORNING. PRESSURE GRADIENT WILL RELAX ON THU...BUT DIURNAL
WARMING/DEEP MIXING STILL LOOKS TO RESULT IN NORTHWEST WINDS 10-15KT
G20-25KT FOR LATE THU MORNING/THU AFTERNOON.

&&

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

$$

SHORT TERM...BOYNE
LONG TERM....BOYNE
AVIATION.....RRS


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