Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 292301
AFDARX

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

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 335 PM CDT WED JUL 29 2015

WATER VAPOR IMAGERY THIS AFTERNOON SHOWED AN UPPER LOW MOVING ACROSS
NORTHERN ONTARIO DRAGGING A COLD FRONT ACROSS LOWER
MICHIGAN/NORTHERN INDIANA. MEANWHILE SURFACE HIGH PRESSURE  WAS
IN PLACE ACROSS WESTERN NEBRASKA THROUGH WYOMING AND INTO THE
NORTHERN ROCKIES. A TIGHT PRESSURE GRADIENT WAS IN PLACE ACROSS
THE UPPER MISSISSIPPI RIVER VALLEY RESULTING IN BREEZY WEST WINDS
OF 15 TO 23 MPH WITH GUSTS APPROACHING 35 MPH AT TIMES. THESE
WINDS WILL SUBSIDE THIS EVENING WITH THE LOSS OF DAYTIME
HEATING/MIXING. WE WILL THEN SEE CLEAR SKIES ACROSS THE AREA
DURING THE OVERNIGHT HOURS WITH HIGH PRESSURE IN CONTROL. LOOK FOR
LOW TEMPERATURES TO FALL INTO THE UPPER 50S TO LOWER 60S. A WEAK
SHORTWAVE MOVES THROUGH THE AREA TONIGHT IN NORTHWEST FLOW ALOFT
BUT THE SURFACE HIGH WILL CONTINUE TO DOMINATE THE WEATHER
PATTERN. ANOTHER PLEASANT WEATHER DAY IS IN STORE FOR THE REGION
ON THURSDAY WITH THE HIGH IN CONTROL. A FAIRLY TIGHT PRESSURE
GRADIENT REMAINS IN PLACE PROVIDING PERSISTENT WEST/NORTHWEST
WINDS OF 10 TO 15 MPH WITH GUSTS APPROACHING  23 MPH. A WEAK
SHORTWAVE MOVES THROUGH NORTHERN WISCONSIN THURSDAY AFTERNOON AND
COULD TRIGGER A FEW ISOLATED SHOWERS OR A THUNDERSTORMS NORTH AND
EAST OF THE INTERSTATE 94 CORRIDOR. CONFIDENCE IS LOW THAT THIS
ACTIVITY WOULD IMPACT CLARK AND TAYLOR COUNTIES SO WILL NOT
INCLUDE IT IN THE FORECAST AT THIS TIME. HOWEVER...WILL BE
INCREASING CLOUD COVER ACROSS THESE AREA TO ACCOUNT FOR A CUMULUS
CLOUD FIELD THAT IS EXPECTED TO FORM DURING THE LATE MORNING INTO
THE AFTERNOON HOURS. ANOTHER WEAK SHORTWAVE MOVES ACROSS NORTHERN
WISCONSIN AND UPPER MICHIGAN. THE NAM/GFS ALONG WITH SOME
MESOSCALE MODELS GENERATE SOME PRECIPITATION OVER NORTHERN
WISCONSIN AND UPPER MICHIGAN THURSDAY NIGHT BUT GIVEN THAT THE
ATMOSPHERE SHOULD BE FAIRLY CAPPED BY THEN WILL NOT INCLUDE ANY
MENTIONABLE PRECIPITATION AT THIS TIME.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 335 PM CDT WED JUL 29 2015

THE SAME PATTERN OF WEAK SHORTWAVES IN NORTHWEST FLOW WILL HOLD INTO
FRIDAY AS ANOTHER WAVE MOVES THROUGH THE NORTHERN WISCONSIN FRIDAY
AFTERNOON. AGAIN FORECAST MODELS SHOW SOME SHOWER AND THUNDERSTORM
ACTIVITY  OVER THE NORTHERN HALF OF WISCONSIN WITH THIS WAVE. THE
NEXT WAVE MOVES INTO THE REGION SATURDAY NIGHT AND LOOKS TO BRING
A ROUND OF SHOWERS AND STORMS TO THE AREA. 0-1 KM MUCAPE VALUES
INTO THE 700 TO 1500 J/KG RANGE ALONG WITH 0-3 KM BULK SHEAR
VALUES OF 30 TO 35 KTS. SO A FEW STRONG TO PERHAPS SEVERE STORMS
CANNOT BE RULED OUT BUT THIS WILL ALL DEPEND ON HOW MUCH CAPE CAN
BUILD INTO THE FORECAST AREA AHEAD OF THE APPROACHING WAVE. A COLD
FRONT THEN DROPS SOUTH FROM THE NORTHER PLAINS/SOUTHERN CANADA
LATE SUNDAY AFTERNOON INTO SUNDAY NIGHT BRINGING ADDITIONAL
CHANCES FOR SHOWERS AND STORMS TO THE REGION. SHEAR AND CAPE COULD
SUPPORT STRONG TO SEVERE STORMS LATE SUNDAY AFTERNOON INTO SUNDAY
NIGHT BUT ITS A LITTLE TOO EARLY TO NAIL DOWN EXACT DETAILS. AN
UPPER LEVEL TROUGH WILL THEN DIG INTO REGION FROM CANADA SUNDAY
NIGHT THROUGH MONDAY EVENTUALLY BRINGING SLIGHTLY COOLER
TEMPERATURES TO THE AREA BY TUESDAY. THERE WILL BE CONTINUED LOW
CHANCES FOR SHOWERS AND STORMS MONDAY NIGHT INTO TUESDAY.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 601 PM CDT WED JUL 29 2015

THE WINDS WILL BE THE MAIN CONCERN THROUGH THE PERIOD. HIGH
PRESSURE CENTERED OVER NEBRASKA LATE THIS AFTERNOON WILL DRIFT
SLOWLY SOUTHEAST INTO MISSOURI THROUGH THURSDAY AFTERNOON. THIS
WILL ALLOW THE SKIES TO REMAIN CLEAR THROUGH THE PERIOD. THE GUSTY
WEST WINDS TODAY WILL SETTLE DOWN TO LESS THAN 10 KNOTS THIS
EVENING AS THE LOW LEVEL INVERSION DEVELOPS AND CUTS OFF THE
MIXING. THESE WINDS SHOULD AGAIN BECOME GUSTY THURSDAY ONCE THE
INVERSION MIXES OUT. HOWEVER...THE WINDS SHOULD NOT BE AS STRONG
AS TODAY WITH SUSTAINED WINDS AROUND 15 KNOTS AND GUSTS TO ABOUT
25 KNOTS.

&&

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

$$

SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...04



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