Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 042043
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
343 PM CDT FRI SEP 4 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 343 PM CDT FRI SEP 4 2015

A WARM FRONT...SITUATED  NEAR THE MISSISSIPPI RIVER WILL
GRADUALLY LIFT NORTHEAST  LATE THIS AFTERNOON THROUGH TONIGHT.
ISOLATED SHOWERS AND A FEW THUNDERSTORMS ARE POSSIBLE ALONG THIS
FRONT...MAINLY THROUGH 7 PM. WITH ONLY WEAK SHEAR IN
PLACE...SEVERE WEATHER IS NOT EXPECTED.

A WEAK SHORTWAVE WAS MOVING EAST ACROSS SOUTHWEST MINNESOTA/WESTERN
IOWA THIS AFTERNOON PRODUCING A FEW SHOWERS AND ISOLATED
THUNDERSTORMS. THIS WAVE IS EXPECTED TO PUSH EAST ACROSS THE
FORECAST AREA TONIGHT BRINGING VERY SLIGHT CHANCES FOR SHOWERS AND
POSSIBLY A THUNDERSTORM. LOOKING AT FORECAST SOUNDINGS ACROSS THE
AREA TONIGHT THEY ARE SHOWING DRY AIR FROM JUST ABOVE THE SURFACE
THROUGH AROUND 11KFT FT. AIR PARCELS WOULD HAVE TO BE LIFTED FROM
THIS LEVEL TO GET CONVECTION TO GO. BECAUSE OF THIS...THERE IS
VERY LIMITED CAPE TO WORK WITH. THE MOST LIKELY OUTCOME TONIGHT
WILL BE SOME ALTOCUMULUS CASTELLANUS. THE CONVECTIVE ALLOWING
MODELS CONTINUE TO GENERATE  SCATTERED SIMULATED RADAR RETURNS
TONIGHT SO WILL CONTINUE WITH A SLIGHT CHANCE FOR SHOWERS AND
STORMS ACROSS MUCH OF THE FORECAST AREA OVERNIGHT. THE WARM FRONT
WILL LIFT TO THE NORTHEAST OVERNIGHT INTO SATURDAY MORNING. WARM
SOUTHERLY FLOW WILL BE THE RULE ON SATURDAY ACROSS THE FORECAST
AREA WITH HIGHS CLIMBING INTO THE MID TO UPPER 80S. A FEW
MISSISSIPPI RIVER VALLEY LOCATIONS COULD REACH THE 90 TO 93 DEGREE
MARK.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 343 PM CDT FRI SEP 4 2015

UPPER LEVEL RIDGE AXIS STARTS TO EDGE EAST SATURDAY NIGHT INTO
SUNDAY AS FLOW ALOFT STARTS TO TRANSITION TO SOUTHWEST AS A TROUGH
EDGES EAST ACROSS THE WESTERN CONUS. AN EMBEDDED SHORTWAVE SLIDES
ACROSS MINNESOTA SATURDAY NIGHT INTO SUNDAY MORNING AND COULD JUST
BRUSH NORTHWEST SECTIONS OF THE FORECAST AREA WITH A COUPLE OF
SHOWERS AND THUNDERSTORMS . OTHERWISE THE PRESSURE GRADIENT WILL
CONTINUE TO TIGHTEN ACROSS THE REGION ON SUNDAY AS A COLD FRONT
APPROACHES. VERY WARM AIR AND DEEP MIXING AHEAD OF THE FRONT WILL
ALLOW TEMPERATURES TO SOAR INTO THE UPPER 80S TO LOWER 90S. A FEW
MID 90S ARE POSSIBLE ACROSS PORTIONS OF SOUTHWEST WISCONSIN. HEAT
INDEX VALUES LOOK TO CLIMB INTO THE MID TO UPPER 90S DURING THE
AFTERNOON HOURS...ESPECIALLY ALONG THE MISSISSIPPI RIVER AND
WISCONSIN RIVER VALLEYS...INTO CENTRAL WISCONSIN. SHOWERS AND STORMS
ARE EXPECTED TO DEVELOP ALONG THE COLD FRONT LATE SUNDAY AFTERNOON
ACROSS NORTHEAST IOWA....SOUTHEAST MINNESOTA AND NORTHWEST
WISCONSIN. 0-1KM MUCAPE VALUES LOOK TO CLIMB INTO THE 1200 TO 18000
J/KG RANGE WEST OF THE  MISSISSIPPI RIVER. 0-3 KM BULK SHEAR
VALUES ARE ONLY EXPECTED TO BE IN THE 15 TO 20 KT RANGE. GIVEN THE
CAPE VALUES WE CANNOT RULE OUT A FEW STRONG TO POSSIBLY SEVERE
STORMS WITH THE MAIN THREATS OF STRONG WIND GUSTS...AT LEAST FROM
LATE AFTERNOON INTO EARLY EVENING BEFORE THE CAPE STARTS TO WANE.
THE FRONT WILL PUSH EAST ACROSS THE FORECAST AREA DURING THE
OVERNIGHT HOURS WITH SHOWERS AND STORMS EXPECTED ALONG IT. THE
STORMS WILL PROBABLY BE ON A WEAKENING TREND AS THEY MAKE IT INTO
WESTERN AND CENTRAL WISCONSIN. ANOTHER ITEM WORTH NOTING IS THAT
THE JET POSITION RELATIVE TO THE COLD FRONT. THE 300 MB JET IS
LAGING BEHIND THE FRONT AND ORIENTED PARALLEL WHICH ISN/T
FAVORABLE FOR DEEP LIFT. MUCH MORE COMFORTABLE
TEMPERATURES/DEWPOINTS MOVE INTO THE REGION IN THE WAKE OF THE
FRONT FOR MONDAY INTO TUESDAY. THERE ARE CHANCES FOR SHOWERS AND
STORMS AGAIN ON TUESDAY AS THE FRONT HANGS UP ACROSS CENTRAL IOWA
INTO NORTHERN  ILLINOIS WITH SOME MOISTURE POSSIBLY OVERRUNNING
THE FRONT. WILL HAVE TO KEEP A CLOSE EYE ON EXACTLY  WHERE THIS
FRONT DECIDES TO SET UP. THERE ARE LOW CHANCES FOR SHOWERS AND
STORM FROM WEDNESDAY INTO FRIDAY BUT FORECAST CONFIDENCE IS LOW AT
THIS TIME...SO LEANED TOWARD A MODEL CONSENSUS BLEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1244 PM CDT FRI SEP 4 2015

A SHORT WAVE TROUGH MOVING NORTHEAST THROUGH MINNESOTA WILL BRING
A BROKEN DECK OF 10 TO TO 15K FOOT CLOUDS TO THE AREA FROM LATE
THIS AFTERNOON THROUGH SATURDAY MORNING. WHILE THE MESO MODELS ARE
SHOWING SOME ISOLATED TO SCATTERED SHOWERS AND STORMS...CONCERNED
THAT THE LACK OF FORCING AND DRY AIR BELOW 10K FEET MAY RESULT IN
MAINLY VIRGA...SO DID NOT ADD ANY PRECIPITATION TO THE TAFS. WITH
10 TO 20 KNOT WINDS JUST OFF THE SURFACE AND A BROKEN DECK OF
CLOUDS...DID NOT INCLUDE ANY FOG IN EITHER TAF SITE.


&&

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

$$

SHORT TERM...WETENKAMP
LONG TERM...WETENKAMP
AVIATION...BOYNE



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