Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 040900
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
400 AM CDT FRI SEP 4 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 400 AM CDT FRI SEP 4 2015

FORECAST FOCUS IS ON SMALL RAIN CHANCES TODAY AND INTO TONIGHT.
CONVERGENT AREA SEEN IN SURFACE ANALYSIS AT 08Z FROM NORTHERN
IL...NORTHWEST THROUGH NORTHEAST IA AND INTO MN. OVERRUNNING THIS
AREA RESULTING IN NORTHWEST TO SOUTHEAST BANDS OF CLOUD COVER.
SOME CONVECTION OVER SOUTHWEST WI LAST NIGHT...BUT NOTHING
RECENTLY. BUT SATELLITE IMAGERY SHOWS CASTELLANUS ACROSS IA WITH
ISOLATED SLOW-MOVING -TSRA...WHICH HAS BEEN PERCOLATING ALL NIGHT.
WATER VAPOR IMAGERY CLEARLY SHOWS THE SHORT WAVE DROPPING SLOWLY
ACROSS WI AND INTO IL. MEANWHILE A WEAK RIPPLE WAS MOVING
NORTHEAST ACROSS THE DAKOTAS. THUS WITH THE MAIN FORCINGS JUST
OUTSIDE OUR FORECAST AREA...THE RAIN CHANCES ARE LIMITED. MODELS
ALL HAVE VARYING DEGREES OF RAIN CHANCES...WITH GFS MOST ROBUST
AND NAM MOST PALTRY. DESPITE WEAK FORCING...DEGREE OF AVAILABLE
MOISTURE AND INSTABILITY SHOULD AT LEAST ALLOW FOR SOME
POSSIBILITY FOR RAIN.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 400 AM CDT FRI SEP 4 2015

AREA TO REMAIN IN THE HOT AND STICKY RIDGE UNTIL LATE SUNDAY.
CLOSED CIRCULATION OVER THE PACIFIC NORTHWEST WILL EVENTUALLY
SHIFT FAR ENOUGH EAST INTO MANITOBA BY MONDAY. THIS WILL SEND A
COLD FRONT THROUGH THE REGION SUNDAY NIGHT. THERE IS A VERY GOOD
CHANCE FOR THUNDERSTORMS ALONG THIS BOUNDARY...ESPECIALLY GIVEN
THE SIGNIFICANT AIRMASS CHANGE AND THE AMOUNT OF MOISTURE AND
INSTABILITY AHEAD OF IT. AT FIRST BLUSH IT APPEARS THERE WOULD BE
A RISK FOR STRONG OR EVEN SEVERE STORMS AS THE FRONT PASSES. BUT
WITH THE FRONT PASSING AFTER THE PEAK DIURNAL TIMEFRAME...AND WITH
THE BEST SHEAR LAGGING IT...NOT OVERLY IMPRESSED. STILL...IT BEARS
WATCHING. COOLER WEATHER THEN ON TAP FOR THE REMAINDER OF THE
WEEK...MORE TYPICAL OF SEPTEMBER. ANOTHER CHANCE FOR SHOWERS
MONDAY NIGHT INTO TUESDAY THE TROUGH MOVES EAST ACROSS ONTARIO.
ZONAL TO SLIGHTLY NORTHWEST FLOW THEN PREVAILS THROUGH NEXT
WEEKEND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1148 PM CDT THU SEP 3 2015

DESPITE SOME MIXING AT THE SURFACE FROM THE SOUTHEAST WINDS...MVFR
VISIBILITIES HAVE ALREADY DEVELOPED AT KRST. THE 04.00Z NAM
FORECAST SOUNDINGS SUGGESTS THE SURFACE WILL STAY NEARLY SATURATED
THROUGH THE NIGHT...SO WILL CONTINUE THE MVFR VISIBILITY
REDUCTION...BUT STILL THINK THE WINDS AT THE SURFACE AND ALOFT
WILL BE TOO STRONG TO ALLOW IFR CONDITIONS TO DEVELOP. THERE WAS
STILL A 7 DEGREE TEMP/DEW POINT SPREAD AT 04.04Z AT KLSE AND THE
NAM FORECAST SOUNDINGS NOW DO NOT SHOW SATURATION OCCURRING
OVERNIGHT SO HAVE GONE BACK TO A PREVAILING MVFR VISIBILITY LATE
TONIGHT IN SOME FOG WITH JUST A SHORT PERIOD WITH SOME IFR
POSSIBLE. ONCE THE FOG BURNS OFF FRIDAY MORNING SHOULD BE VFR
CONDITIONS FOR THE REST OF THE PERIOD. A PASSING SHORT WAVE TROUGH
FRIDAY EVENING COULD BRING IN SOME MID LEVEL CLOUDS TO KRST FOR A
HIGH VFR CEILING.


&&

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

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...04



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