Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 300453
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1153 PM CDT TUE JUL 29 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 245 PM CDT TUE JUL 29 2014

SCATTERED LOW TOPPED CONVECTION HAS DEVELOPED ACROSS THE
REGION...PARTICULARLY IN NORTHWEST WISCONSIN WHERE 29.18Z RAP
ANALYSIS SHOWS ABOUT 500-1000 J/KG OF SBCAPE. THE LIFT FOR THIS
CONVECTION APPEARS TO MAINLY BE FROM A 700MB TROUGH DIVING SOUTH
INTO THE WESTERN GREAT LAKES. AS DIURNAL HEATING COMES TO AN
END...EXPECT THAT THE COVERAGE OF THESE SHOWERS WILL DIMINISH AS
THE EVENING GOES ON.

CONFIDENCE IS NOT AS HIGH WITH WHETHER CONVECTION WILL INITIATE
TOMORROW AFTERNOON ACROSS WISCONSIN. THE FORCING OVERALL IS MUCH
WEAKER...YET WE ARE STILL IN CYCLONIC FLOW ALOFT WITH THE TROUGH
NEARBY IN ONTARIO. HAVE LEFT A SLIGHT CHANCE TO CHANCE OF
SHOWERS/STORMS IN TOMORROW AFTERNOON MAINLY IN WESTERN WISCONSIN
TO ALONG THE MISSISSIPPI RIVER IN IOWA/MINNESOTA DUE TO SOME WEAK
INSTABILITY DEVELOPING BETWEEN 800-600MB PER 29.12Z NAM/GFS
SOUNDINGS.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 245 PM CDT TUE JUL 29 2014

A STALLED MID TO UPPER LEVEL PATTERN THROUGH THE REST OF THE WORK
WEEK WILL LEAD TO LITTLE CHANGE IN LOCAL CONDITIONS WITH MAINLY
NORTHWEST FLOW ALOFT KEEPING COOLER THAN NORMAL TEMPERATURES IN
PLACE. SOME DIURNAL CONVECTION STILL LOOKS POSSIBLE THROUGH FRIDAY
AS THE CORE OF THE MID LEVEL TROUGH DRIFTS EAST OVER THAT TIME
FRAME. STILL NOT MUCH MORE THAN 100-500 J/KG OF SB/MLCAPE AND WEAK
DEEP SHEAR TO WORK WITH...SO ANY CONVECTION SHOULD REMAIN PULSEY.
THERE APPEARS TO BE SOME CONSENSUS IN THE 29.12Z GUIDANCE THAT
SURFACE TO MID LEVEL RIDGING WILL SET UP ACROSS THE REGION ON
SATURDAY SO THAT CONVECTION SHOULD NOT DEVELOP WITH A MAINLY
SUBSIDENT AIR MASS IN PLACE.

SOME SLIGHTLY WARMER AIR LOOKS LIKE IT WILL GET ADVECTED INTO THE
REGION ON SUNDAY AHEAD OF THE NEXT SYSTEM/COLD FRONT THAT WILL
MOVE INTO THE REGION FROM THE NORTH ON SUNDAY. THE 29.12Z
GFS/ECMWF/GEM ALL OFFER DIFFERENT SOLUTIONS ON THE POSITION OF
THIS FRONT AND HOW FAR SOUTH IT WILL MAKE IT EARLY NEXT WEEK. THE
GEM OFFERS UP THE FARTHEST NORTH/WARMEST SOLUTION WITH THE ECMWF
BEING A FASTER SOLUTION THAN THE GFS WITH ITS PUSH SOUTH
SUNDAY THROUGH TUESDAY. SOME DECENT INSTABILITY COULD DEVELOP
ALONG/AHEAD OF THIS FRONT...SO WILL HAVE TO KEEP AN EYE ON ITS
TRENDS GOING THROUGH THE WEEKEND/EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1153 PM CDT TUE JUL 29 2014

SHOWERS ARE FINALLY DISSIPATING WITH LOSS OF DAYTIME HEATING...
DESPITE TRACKING FARTHER WEST THAN PREVIOUSLY EXPECTED. BOTH TAF
SITES SHOULD BE PRECIP FREE THROUGH THE MORNING HOURS. POTENTIAL
EXISTS AGAIN DURING THE AFTERNOON FOR SHOWERS TO DEVELOP...THOUGH
COVERAGE SHOULD BE LESS THAN WHAT OCCURRED ON TUESDAY.
NEVERTHELESS...FEEL CONFIDENT ENOUGH TO INCLUDE A VCSH AT BOTH
TAF SITES. THESE SHOWERS WILL THEN DISSIPATE DURING THE EVENING
HOURS...PERHAPS QUICKER THAN TODAY GIVEN LESS COVERAGE.

OVERALL VFR CONDITIONS WILL CONTINUE. THE BIG THING TO WATCH FOR
IS POTENTIAL FOR FOG FORMATION THIS MORNING. CLOUDS ARE SCATTERING
OUT AROUND THE REGION. GIVEN RECENT RAIN AND LIGHT WINDS...AT A
MINIMUM EXPECTING SOME BR TO FORM PRIOR TO SUNRISE. ITS POSSIBLE
VISIBILITIES GO EVEN LOWER.

&&

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

$$

SHORT TERM...HALBACH
LONG TERM...HALBACH
AVIATION...AJ


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