Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 301139
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
639 AM CDT SUN AUG 30 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 341 AM CDT SUN AUG 30 2015

MOST IMMEDIATE CONCERN IS PATCHY DENSE FOG EARLY THIS MORNING.
BECAUSE NOT ALL LOW CLOUD FROM YESTERDAY DISSIPATED AND THE FACT
THAT 0.5 KM SOUTHWEST WINDS ARE INCREASING FROM NOW UNTIL
SUNRISE...WIDESPREAD DENSE FOG IS IN QUESTION. THERE HAVE BEEN
SOME SITES ACROSS THE REGION THAT HAVE REPORTED ONE-HALF MILE OR
LESS IN FOG...BUT NOT CONSISTENTLY AS VISIBILITY GOES UP AND DOWN
OVER RELATIVELY SHORT PERIODS. FOR NOW...WILL COVER FOG THREAT
WITH A SPS...BUT MONITOR CAREFULLY FOR MORE WIDESPREAD PERSISTENT
LOW VISIBILITY THAT COULD NECESSITATE AN ADVISORY.

WHETHER STRATUS OF FOG...MOST AREAS SHOULD WAKE UP TO GRAY/FOGGY
SKIES. HOWEVER...LOW-LEVEL MOISTURE SHOULD BEGIN TO MIX OUT AFTER
SUNRISE AS BOUNDARY LAYER DEEPENS TO BETWEEN 1500 AND 2000 FT BY
MIDDAY. SHOULD FINALLY BEGIN TO SEE A FAIR AMOUNT OF SUN BY EARLY
TO MID AFTERNOON. WITH A SLOW START TO WARMING FOR THE DAY...
DROPPED TEMPERATURES A FEW DEGREES WITH HIGHS NOW EXPECTED IN THE
MID TO UPPER 70S. FOR AREAS THAT SEE A BIT MORE SUN...HIGHS MAY
WARM INTO THE LOWER 80S.

EXPECT MOSTLY CLEAR SKIES TONIGHT WITH LIGHT SOUTHERLY WINDS. WILL
KEEP PATCHY VALLEY/BOG FOG MENTION...BUT ITS OCCURRENCE IS A BIT
LESS CERTAIN. MODEL SOUNDINGS SHOWING NEAR SURFACE SATURATION...
BUT ALSO 15 TO 20 KTS IMMEDIATELY ABOVE THE NOCTURNAL INVERSION.
THIS SET-UP MAY BE MORE FAVORABLE FOR LOW STRATUS THAN FOG...BUT
SOMETHING TO WATCH. LOWS TONIGHT WILL DROP INTO THE 60S.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 341 AM CDT SUN AUG 30 2015

MONDAY THROUGH WEDNESDAY...500 HPA RIDGE MOVES INTO THE EASTERN
CONUS...ALTHOUGH PERHAPS A BIT FLATTER THAN PREVIOUSLY FORECAST
GIVEN WEAK SHORT-WAVES MOVING THROUGH SOUTHWEST FLOW ALOFT. MAIN
IMPACT WILL BE WARMING TEMPERATURES WITH DAILY HIGHS IN THE 80S...
ALTHOUGH SOME VALLEY LOCATIONS COULD APPROACH 90 DEGREES GIVEN
FAVORABLE SOUTH-SOUTHWEST SURFACE WIND. RIDGE AXIS RETROGRADES
BACK ACROSS THE SOUTHERN PLAINS FOR LATE IN THE WEEK...RESULTING
IN THUR/FRI/SAT POSSIBLY BEING THE WARMEST DAYS OF THE WEEK WITH
MANY LOCATIONS INTO THE UPPER 80S...PERHAPS 90 DEGREES.

WILL KEEP PERIODIC 20-30 POPS THROUGH THE WEEK...ALTHOUGH THINK
DRY CONDITIONS WILL BE THE RULE SINCE AXIS OF MAXIMUM MID-LEVEL
MOISTURE TRANSPORT REMAINS MAINLY WEST OF THE FORECAST AREA AND
DEEP LAYER SHEAR IS WEAK. BEST CHANCE FOR MORE WIDESPREAD SHOWERS
AND THUNDERSTORMS HOLDS OFF UNTIL LATE SATURDAY INTO SUNDAY AS
EASTERN PACIFIC TROUGH/COLD FRONT FINALLY PUSH FAR ENOUGH EAST TO
IMPACT THE UPPER MS RIVER VALLEY. WILL INTRODUCE HIGH END CHANCE
POPS FOR THIS PERIOD. WITH CLOUDS/POSSIBLE RAIN AND APPROACHING
COLD FRONT...COULD SEE TEMPERATURES BEGIN TO RETREAT AS EARLY AS
NEXT SUNDAY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 639 AM CDT SUN AUG 30 2015

LIGHT/CALM WINDS AND MOIST LOWER BOUNDARY LAYER FROM RECENT
RAINFALL LEADING TO MESSY MIX OF MVFR TO LIFR FOG AND STRATUS
ACROSS THE AREA EARLY THIS MORNING. LOOK FOR THE FOG AND STRATUS
TO BURN OFF/ERODE BY LATER THIS MORNING AS SOUTH/SOUTHWEST WINDS
MIX BOUNDARY LAYER OUT. SURFACE HIGH SLIPS SOUTHEAST OF THE AREA
TONIGHT FOR CONTINUED SOUTHERLY FLOW.LOOKS LIKE SOME STRATUS WILL
FILL BACK INTO THE AREA AFTER MIDNIGHT...BUT EXTENT IS UNCERTAIN
AT THIS TIME. INCLUDED SCT003 MENTION AT BOTH KRST AND KLSE IN THE
09-10Z TIME FRAME. FOG SEEMS UNLIKELY AT THIS POINT DUE TO
SOUTHERLY WINDS KEEPING LOWER BOUNDARY LAYER STIRRED UP.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR WIZ017.

MN...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR MNZ086-094-
     095.

IA...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR IAZ008>010-
     018-019-029.

&&

$$

SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...DAS


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