Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 291701
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1201 PM CDT SAT AUG 29 2015

.UPDATE...
ISSUED AT 1201 PM CDT SAT AUG 29 2015

THE LOW CLOUDS ARE HOLDING TOUGH ACROSS THE AREA THIS MORNING. THE
SHORT WAVE TROUGH HAS MOVED PASSED THE REGION ALLOWING SUBSIDENCE
TO DEVELOP...BUT THE 29.12Z NAM FORECAST SOUNDINGS DO NOT SHOW
THIS TO BE VERY STRONG AND MAY ACTUALLY HELP TO STRENGTHEN THE LOW
LEVEL INVERSION. WITH THE MOISTURE TRAPPED BELOW THIS
INVERSION...IT WILL TAKE MUCH OF THE DAY AND POSSIBLY INTO THE
EVENING TO REALLY CLEAR THE CLOUDS OUT. VISIBLE SATELLITE IS
SHOWING SOME THINNING OF THE CLOUDS AND IF THIS CONTINUES...THE
CLEARING COULD DEVELOP YET THIS AFTERNOON. FOR NOW WILL GO WITH A
MORE PESSIMISTIC FORECAST AND HAVE INCREASED THE CLOUD COVER FOR
THE REMAINDER OF THE DAY AND DROPPED HIGH TEMPERATURES A COUPLE OF
DEGREES.

&&

.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 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1201 PM CDT SAT AUG 29 2015

JUST HOW LONG THE MVFR CEILINGS WILL HOLD ON IS THE FIRST CONCERN
WITH THE FORECAST. SOME THINNING OF THE CLOUDS EVIDENT ON VISIBLE
SATELLITE...BUT THE 29.12Z NAM FORECAST SOUNDINGS SUGGEST THE
CLOUDS WILL HOLD ON WELL INTO THE EVENING. WITH WEAK SUBSIDENCE
OVER THE AREA...WILL BE PESSIMISTIC AND KEEP THE MVFR CEILINGS
INTO THE EVENING. SKIES SHOULD THEN CLEAR/SCATTER OUT FOR A SHORT
WHILE THIS EVENING BEFORE IT LOOKS LIKE FOG WILL FORM. PLENTY OF
LOW LEVEL MOISTURE FROM THE RECENT RAINS AND A DEEP LAYER OF LIGHT
WINDS AND WILL TAKE BOTH TAF SITES DOWN TO IFR WITH LOW
VISIBILITIES AND CEILINGS. THIS COULD TAKE MOST OF SUNDAY MORNING
TO TOTALLY DISSIPATE...ESPECIALLY IN THE VALLEY FOR KLSE AND WILL
HOLD THE IFR CONDITIONS FOR MUCH OF THE MORNING.

&&

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

$$

UPDATE...04
SHORT TERM...ROGERS
LONG TERM...ROGERS
AVIATION...04


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