Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 212327
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
627 PM CDT SUN SEP 21 2014

.SHORT TERM...(TONIGHT)
ISSUED AT 200 PM CDT SUN SEP 21 2014

THE VIGOROUS UPPER LEVEL SHORTWAVE TROUGH THAT BROUGHT THE
SHOWERS/STORMS TO THE REGION LAST NIGHT WAS TRACKING ACROSS THE
EASTERN GREAT LAKES EARLY THIS AFTERNOON. SFC FRONT EXTENDED
WESTWARD FROM SYSTEMS/S LOW...BACK ACROSS WI. ADD IN FAVORABLE LOW
LEVEL LAPSE RATES AND SPOTTY/SCATTERED SHOWERS CONTINUED ACROSS
CENTRAL-EASTERN WI.

THE BOUNDARY WILL SLIP SOUTH BY THE EVENING WITH HIGH PRESSURE
BUILDING INTO IA/MO OVERNIGHT. A LOT OF DIURNAL ELEMENTS TO THE
CURRENT CLOUD MASS ACROSS THE REGION...AND WITH THE LOSS OF DAYTIME
HEATING AND SINKING AIR ASSOCIATED WITH THE HIGH...EXPECT THESE
CLOUDS TO CLEAR QUICKLY THIS EVENING. COULD SEE SOME FOG IN THE
RIVER VALLEYS FOR MONDAY MORNING.

.LONG TERM...(MONDAY THROUGH SUNDAY)
ISSUED AT 200 PM CDT SUN SEP 21 2014

GFS/ECMWF/GEM ALL IN GOOD AGREEMENT WITH BUILDING A STRONG UPPER
LEVEL RIDGE ACROSS THE CENTRAL U.S. FOR MUCH OF THIS WEEK. ALL WANT
TO SLIP A SHORTWAVE TROUGH FROM THE WEST COAST INTO THE
CENTRAL/NORTHERN PLAINS TUE...THEN TRIES TO LIFT IT EAST/NORTHEAST
ACROSS THE UPPER MISSISSIPPI RIVER VALLEY. GEM/GFS SPLIT THE UPPER
LEVEL ENERGY...TAKING A PIECE NORTH OF THE AREA...AND HANGING A
SOUTHERN PIECE OVER THE PLAINS. ASSOCIATED SFC FRONT ISN/T OVERLY
CONVERGENT IN THE LATEST SOLUTIONS. SOME LOW LEVEL MOISTURE
TRANSPORT COULD HELP FUEL SOME SHOWERS. THE GFS/GEM AND EVEN THE NAM
WOULD HOLD ANY PCPN ACROSS MN...PUSHING INTO SOUTHERN CANADA. SOME
SHOWER CHANCES OVER IA AND WEST INTO THE PLAINS. PREVIOUS EC RUN
FAVORED KEEPING THE SHORTWAVE TOGETHER...THUS STRONGER AND MORE
CONVERGENT TOWARD THE SFC WITH THE FRONT. HOWEVER...THE 12Z RUN IS
NOW MORE INLINE WITH THE SPLITTING SOLUTION. WILL LEAN THIS WAY.

THE BIT OF SOUTHERN ENERGY COULD RETROGRADE TO THE WEST WHILE THE
UPPER RIDGE CONTINUES TO ASSERT ITSELF. A SFC HIGH SETS UP SHOP OVER
THE EASTERN GREAT LAKES...PUTTING THIS REGION UNDER SOUTHERLY FLOW.
TEMPS WILL WARM...WITH 850 MB TEMPS CLIMBING FROM AROUND 8 C ON
MONDAY TO 16 C FRI. NAEFS 850 MB TEMP ANOMALIES POINTING TO +2
ACROSS SOUTHERN CANADA FOR THU-SAT...BUT 0-1 LOCALLY. STILL...LOOKS
LIKE ABOVE NORMAL TEMPERATURES TOWARD THE END OF THE WEEK...AND
COULD BE A VERY MILD OKTOBERFEST FOR THOSE IN THE LA CROSSE AREA.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 627 PM CDT SUN SEP 21 2014

RIVER VALLEY FOG AT KLSE IS THE MAIN FOCUS FOR THE PERIOD AS COOL
CANADIAN HIGH PRESSURE BUILDS IN FROM THE WEST. SEVERAL POSITIVES
FOR IFR FOG INCLUDE COOLER TEMPS...SOME CLOUDS TODAY WITH LATE
DAY CLEARING...AND THE EXPECTATION THAT THE WINDS THROUGH 3 KFT
WILL BEGIN TO LIGHTEN UP TO LESS THAN 10 KTS TONIGHT.
TEMP/DEWPOINT SPREADS LATE THIS AFTERNOON ARE WITHIN THE
CLIMATOLOGICAL BOUNDARIES FOR DENSE FOG AND A TIME TREND ANALYSIS
OF VARIOUS MODEL SOLUTIONS POINTS TO HIGHER CONFIDENCE FOR A DENSE
FOG PERIOD. AT THIS POINT...INCLUDED 1 SM VISIBILITIES AND 200 FT
CEILINGS...BUT WILL MONITOR TRENDS EARLY THIS EVENING TO DETERMINE
IF A 1/4 SM PERIOD IS NECESSARY. OTHERWISE...MONDAY WILL BE A VFR
DAY WITH ONLY A WIND SHIFT AS THE HIGH MOVES THROUGH THE REGION.

&&

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

$$

SHORT TERM...RIECK
LONG TERM....RIECK
AVIATION.....ZT


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