Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 291130
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
630 AM CDT SAT AUG 29 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 345 AM CDT SAT AUG 29 2015

CHALLENGES INCLUDE CLOUD TRENDS AND TEMPERATURES TODAY AND THEN
FOG POTENTIAL TONIGHT. 29.00Z MODEL SUITE IN GOOD AGREEMENT AND
WILL USE A BLENDED MODEL APPROACH FOR THE FORECAST.

29.08Z SURFACE ANALYSIS SHOWS A ELONGATED LOW PRESSURE CENTER
ACROSS SOUTH-CENTRAL IA INTO NORTHWEST MO AND A NARROW RIDGE AXIS
FROM NORTHEAST CO INTO CENTRAL MN. LAST OF THE LIGHT RAIN SHOWERS
FROM YESTERDAY NOW MOVING INTO EASTERN WI...ALTHOUGH LOW STRATUS
EXTENDS AS FAR WEST AS A LINE FROM NEW ULM MN TO MARSHFIELD WI.
THESE CLOUDS WILL BEGIN A SLOW TREK EASTWARD AFTER SUNRISE AS
LOW-MID LEVEL WINDS TURN TO THE NORTH BEHIND THE DEPARTING TROUGH.
EXPECT MOST AREAS TO CLEAR OUT BY MID-LATE AFTERNOON. DESPITE
INCREASING SUNSHINE...A COOLER AIR MASS WITH 925 HPA TEMPERATURES
FROM 17 TO 19 CELSIUS WILL RESULT IN AFTERNOON HIGHS MAINLY IN THE
MID 70S.

AFOREMENTIONED SURFACE RIDGE AXIS MOVES OVER THE FORECAST AREA
TONIGHT WITH MODEL SOUNDINGS SHOWING A LIGHT WIND LAYER (LESS
THAN 10 KTS) UP TO 10 KFT. WITH MOSTLY CLEAR SKIES AND AMPLE NEAR
SURFACE MOISTURE FROM YESTERDAY/S RAINS...EXPECT FOG TO DEVELOP
ACROSS THE UPPER MS RIVER VALLEY. ADDED PATCHY FOG ACROSS THE
ENTIRE FORECAST AREA FROM 06Z-14Z...AND INCREASED TO AREAS OF FOG
ALONG THE RIVER VALLEYS. WIDESPREAD FOG IS EXPECTED ALONG THE WI
RIVER VALLEY. AREAS OF DENSE FOG A POSSIBILITY...BUT CERTAINTY IN
SPATIAL COVERAGE STILL LOW AT THIS TIME. WILL NEED TO WATCH FOR
POSSIBLE ADVISORY-LEVEL CONDITIONS BY SUNDAY MORNING.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 345 AM CDT SAT AUG 29 2015

ONCE FOG BURNS OFF SUNDAY MORNING...EXPECT MOSTLY SUNNY SKIES FOR
THE REST OF THE DAY. SURFACE HIGH PRESSURE SLIDES EASTWARD...
RESULTING IN LIGHT SOUTHERLY WINDS. HIGH PLAINS THERMAL RIDGE AXIS
BEGINS TO EXPAND EASTWARD...WITH TEMPERATURES RISING BACK INTO THE
UPPER 70S TO LOWER 80S.

FOR THE REST OF THE WEEK...925 HPA TEMPERATURES RISE TO BETWEEN 23
AND 26 CELSIUS AS A STRONG 500 HPA RIDGE DOMINATES THE EASTERN
HALF OF THE CONUS. EXPECT LITTLE DAY-TO-DAY VARIATION IN
TEMPERATURES WITH DAILY HIGHS FROM THE MID TO UPPER 80S. HOWEVER...
WITH PERSISTENT SOUTH-SOUTHWESTERLY SURFACE WINDS...SOME VALLEY
LOCATIONS COULD TOP THE 90 DEGREE MARK. OVERNIGHT LOWS WILL
GENERALLY BE IN THE 60S. MONDAY THROUGH FRIDAY...MORNING VALLEY
FOG THREAT APPEARS LOW GIVEN STRONGER WINDS ATOP THE NOCTURNAL
BOUNDARY LAYER AND THE POTENTIAL FOR SOME MID-HIGH LEVEL CLOUD
COVER.

IN GENERAL...EXPECT A DRY FORECAST NEXT WEEK. THERE IS A SLIGHT
CHANCE FOR SHOWERS AND THUNDERSTORMS MAINLY TUESDAY NIGHT INTO
WEDNESDAY AND AGAIN FRIDAY NIGHT INTO SATURDAY AS WEAK/ILL-
RESOLVED SHORT-WAVES RIDE THE RIDGE IN SOUTHWEST FLOW ALOFT. WITH
HIGHER TEMPERATURES AND INCREASED LOW-LEVEL HUMIDITY...DAILY CAPE
VALUES INCREASE UP TO 2000 J/KG AT TIMES...BUT WITH LITTLE TO NO
DEEP LAYER SHEAR AND PRIMARY MID-LEVEL MOISTURE TRANSPORT WEST OF
THE FORECAST AREA...DO NOT EXPECT ANY STORMS THAT DO DEVELOP TO
BECOME SEVERE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 630 AM CDT SAT AUG 29 2015

EXPANSIVE IFR/LIFR STRATUS AND FOG IN PLACE ACROSS THE AREA THIS
MORNING IN THE WAKE OF RECENT AMPLE RAINFALL FROM FRIDAY INTO THE
OVERNIGHT HOURS. LOOKING FOR GRADUAL IMPROVEMENT THIS MORNING WITH
LIFTING OF FOG AND EROSION OF STRATUS FROM WEST TO EAST. VFR
CONDITIONS EXPECTED BY 18-19Z TIMEFRAME. RIDGE OF HIGH PRESSURE
SETS UP OVER THE AREA TONIGHT FOR LIGHT WINDS...AND COMBINED WITH
RATHER MOIST SURFACE/LOWER BOUNDARY LAYER IN PLACE...LOOK FOR
AREAS/WIDESPREAD FOG TO DEVELOP LATE TONIGHT INTO SUNDAY MORNING.
VFR CONDITIONS EXPECTED TO DETERIORATE AT KRST/KLSE INTO IFR/LIFR
RANGE AFTER 07-08Z.

&&

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

$$

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



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