Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 161947
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
145 PM CST TUE DEC 16 2014

.SHORT TERM...(TONIGHT AND WEDNESDAY)
ISSUED AT 145 PM CST TUE DEC 16 2014

SYSTEMS MOVING AGAIN ACROSS THE UPPER MIDWEST BUT QUESTIONS REMAIN
THE SAME ABOUT THE CLOUDS - HOW LONG WILL THEY LINGER. AT LEAST FOG
NOT A CONCERN NOW.

ONE SHORT WAVE TROUGH EXITING EASTERN GREAT LAKES THIS AFTERNOON BUT
SECOND IMPULSE WAS MOVING ACROSS MINNESOTA RIGHT ON THE HEELS OF
FIRST. WITH LESS MOISTURE TO WORK WITH...LIFT ASSOCIATED WITH SECOND
IMPULSE NOT ENOUGH TO GENERATE MORE PRECIPITATION OUTSIDE OF SOME
FLURRIES THAT WILL LINGER INTO THIS EVENING ACROSS MAINLY PARTS OF
WISCONSIN.

MEANWHILE COLD AIR ADVECTION CONTINUES WITH LARGE AIRMASS CHANGE
TAKING PLACE.

ALTHOUGH SOME BREAKS IN STRATUS DECK OBSERVED ACROSS WESTERN
MINNESOTA INTO IOWA...MODEL GUIDANCE AND BUFKIT SOUNDINGS SUGGEST
LOW POTENTIAL FOR ANY CLEARING IN OUR AREA UNTIL POSSIBLY WEDNESDAY
AFTERNOON...OR PERHAPS EVEN LATER. HAVE BUMPED UP SKY COVER NEXT 24
HOURS BUT WILL TRY AND REMAIN OPTIMISTIC. ALSO HAD TO MODERATE SOME
GUIDANCE ON LOW TEMPERATURES TONIGHT BASED ON MORE TREND TO HOLD
CLOUDS IN...BUT COULD BE TIGHT GRADIENT WHERE IT CLEAR OFF. WILL
FOLLOW NAM IDEAS OF CLEARING LINE WORKING INTO SOUTHWEST SERVICE
AREA BUT HIGHER RISK OF CLOUDS IN NORTH CENTRAL WISCONSIN.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 145 PM CST TUE DEC 16 2014

WEATHER BASICALLY NIL THROUGH REST OF WORK WEEK AS PSEUDO ZONAL FLOW
SETS UP AHEAD OF NEXT WEAK SHORT WAVE ON FRIDAY. LACK OF FORCING
WILL MAKE FOR CHALLENGING CLOUD COVER ALL WEEK THOUGH SO PREFER IDEA
OF SMALL DIURNAL CHANGES BUT A LOT WILL DEPEND ON IF INVERSIONS CAN
BE DECREASED TO CLEAR THINGS OUT.

AS BROAD TROUGH MOVES THROUGH CENTRAL U.S. WE WILL REMAIN NORTH OF
BETTER FORCING AND PRECIPITATION FRIDAY INTO FRIDAY NIGHT.

MAIN FORECAST CONCERNS ARE PRECIPITATION CHANCES MONDAY INTO
TUESDAY. THE 16.12Z GFS/GEM/ECMWF ARE IN GOOD AGREEMENT IN
DEVELOPING WEST TO EAST ZONAL FLOW ACROSS THE NORTHERN TIER UNITED
STATES THIS WEEKEND AND THEN DIG UPPER LEVEL TROUGH OVER THE CENTRAL
UNITED STATES BY 12Z TUESDAY. THE BIGGEST DIFFERENCE BETWEEN THE
MODELS IS THE ECMWF IS SLIGHTLY MORE PROGRESSIVE IN DIGGING UPPER
LEVEL TROUGH OVER THE CENTRAL UNITED STATES THAN THE 16.12Z GFS/GEM.
THE 16.12Z GFS/ECMWF ARE SHOWING DECENT LIFT AND FORCING IN
ASSOCIATION WITH THE UPPER LEVEL TROUGH DIGGING OVER THE CENTRAL
UNITED STATES MONDAY INTO TUESDAY. THIS SHOULD SPREAD PRECIPITATION
INTO THE FORECAST AREA MONDAY INTO TUESDAY AND HAVE INCREASED
PRECIPITATION MONDAY INTO TUESDAY BASED ON THIS. THE 16.12Z
GFS/ECMWF ARE IN AGREEMENT TEMPERATURES ALOFT RISE ABOVE FREEZING
OVER PORTIONS OF THE FORECAST AREA MONDAY AND SUGGEST A WINTRY MIX
OF PRECIPITATION ACROSS MUCH OF THE FORECAST AREA. FOR NOW...HAVE
INTRODUCED A RAIN/SNOW MIX DURING THE DAY MONDAY.
THEN...PRECIPITATION TRANSITIONS TO ALL SNOW MONDAY NIGHT...AS BOTH
THE 16.12Z GFS/ECMWF INDICATE COLDER AIR ADVECTS INTO THE UPPER
MIDWEST AND GREAT LAKES REGION BY 12Z TUESDAY WITH 925MB
TEMPERATURES RANGING FROM PLUS 1 DEGREES CELSIUS TO MINUS 3 DEGREES
CELSIUS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY NOON)
ISSUED AT 1131 AM CST TUE DEC 16 2014

RADAR SHOWS THE LAST OF THE SNOW BAND WITH THE DEPARTING LOW TO PUSH
EAST OF KLSE AROUND 19Z. WHILE TO THE WEST...DEEPER CYCLONIC
CONVERGENCE AHEAD OF A SHORTWAVE AND MID LEVEL LOW DROPPING INTO MN
WAS SQUEEZING OUT SOME FLURRIES AND SCT MVFR VSBYS ACROSS MUCH OF
MN. AS DRIER LOW LEVEL AIR CONTINUES TO SPREAD IN ON THE BRISK
NORTHWEST WINDS...EXPECT VSBYS IN ANY LINGERING FLURRIES TO BE
MAINLY 6SM OR GREATER BY MID AFTERNOON. CIGS UPSTREAM OF THE TAF
SITES MAINLY 1500-2500 FT. LINGERING IFR CIGS AT KRST SHOULD IMPROVE
TO MVFR BY 20Z. MVFR CIGS THEN LOOK TO PERSIST THRU THE TAF PERIOD
AS ABUNDANT LOW LEVEL MOISTURE AND CYCLONIC FLOW REMAIN OVER THE
AREA. NORTHWEST WINDS TO REMAIN BRISK/GUSTY INTO THE EVENING THEN
SLOWLY DIMINISH TO AROUND 10 KTS FOR WED MORNING.

&&

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

$$

SHORT TERM...SHEA
LONG TERM...SHEA/DTJ
AVIATION...RRS


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