000
FXUS63 KARX 111741
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
1141 AM CST WED DEC 11 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 334 AM CST WED DEC 11 2013

MAIN FORECAST CONCERNS ARE ON WIND CHILLS THROUGH TONIGHT AND
PRECIPITATION CHANCES TONIGHT.

CURRENTLY AS OF 09Z...WATER VAPOR LOOP AND RAP 500MB HEIGHT ANALYSIS
SHOWED UPPER RIDGING NEAR THE WEST COAST OF THE U.S....BROAD
TROUGHING OVER THE EAST HALF OF CANADA...AND A SHORTWAVE TROUGH
STRETCHING FROM MN INTO NEBRASKA. AHEAD OF THIS SHORTWAVE TROUGH...A
FRONTOGENESIS BAND OF SNOW ENCOMPASSED MUCH OF EASTERN IOWA INTO
SOUTHERN WI...WHILE CLOUDS COVERED MUCH OF THE FORECAST AREA.
HOWEVER...CLEARING ASSOCIATED WITH SUBSIDENCE IN THE TROUGH WAS
QUICKLY APPROACHING THE FORECAST AREA FROM CENTRAL MN. THIS CLEARING
WAS RIGHT BEHIND A COLD FRONT...WHICH ALSO REPRESENTS AN ARCTIC
AIRMASS POISED TO COME INTO THE AREA TODAY. READINGS ARE BELOW ZERO
FROM NORTH DAKOTA INTO CENTRAL MN...AND IN MANY SPOTS TEENS BELOW
ZERO. 850MB STANDARDIZED TEMPERATURE ANOMALIES ASSOCIATED WITH THIS
ARCTIC AIRMASS ARE 2 BELOW NORMAL. ACCOMPANYING THE ARCTIC AIR ARE
SOME BRISK NORTHWEST WINDS...PARTICULARLY WITH THE ISALLOBARIC PUSH
RIGHT BEHIND THE COLD FRONT. THESE WINDS ARE KNOCKING WIND CHILLS
DOWN TO 20 TO 35 BELOW FROM CENTRAL MN THROUGH NORTHERN WI
NORTHWESTWARD.

THE COLD AIR AND CLEARING SEEN OVER CENTRAL MN WILL RUSH INTO THE
FORECAST AREA QUICKLY THIS MORNING...ASSOCIATED WITH THE COLD
FRONTAL AND SHORTWAVE TROUGH PASSAGE. WINDS SHOULD STAY BRISK ALL
DAY AS A SURFACE OVER THE WESTERN DAKOTAS ENDS UP SLIDING WELL TO
OUR SOUTH...INTO NORTHERN MO BY 00Z. THE STRONGEST WINDS ARE LIKELY
THIS MORNING AS PRESSURES RISE RAPIDLY. TEMPERATURES LOOK TO FALL
THROUGH MID MORNING...MAY GET A LITTLE BUMP UP EARLY THIS AFTERNOON
WITH DAYTIME HEATING...AND FALL YET AGAIN ONCE THE SUN STARTS GOING
DOWN. THUS...ITS GOING TO BE TOUGH TO WARM TODAY. HIGHS IN THE
SINGLE DIGITS ABOVE ZERO APPEARS TO BE ALL WE CAN GET...WITH
LOCATIONS NORTH OF HIGHWAY 10 NOT EVEN REACHING ZERO. FACTOR IN THE
WIND AND MUCH OF THE AREA WILL SEE WIND CHILLS REACHING 20 BELOW
ZERO OR COLDER AT TIMES...ESPECIALLY THIS MORNING AND LATE TODAY.
REGARDING HAZARDS...LIKELY SOMETIME BETWEEN 12-13Z TODAY WE CAN
TRANSITION THE WINTER WEATHER ADVISORY OVER TO A WIND CHILL
ADVISORY IN NORTHEAST IOWA.

THIS SHOT OF ARCTIC AIR APPEARS TO BE SHORT-LIVED...HOWEVER. A
SHORTWAVE SEEN OVER ALBERTA IS PROGGED BY MODELS TO DROP DOWN
THROUGH CENTRAL MN AND WI BETWEEN 06-12Z TONIGHT. THE APPROACH OF
THE SHORTWAVE HELPS TO SWING WINDS AROUND TO THE SOUTHWEST...AND
SPREAD SOME MID/HIGH CLOUDS INTO THE AREA RESULTING FROM DPVA AND
ISENTROPIC LIFT. SO AFTER SOME COOLING FROM RADIATIONAL PROCESSES IN
THE EVENING...ADVECTIVE PROCESSES WILL HELP TEMPERATURES CLIMB
THEREAFTER. GIVEN THE COLD EVENING...EXTENDED THE WIND CHILL
ADVISORY THROUGH 12Z THU FOR SOUTHEAST MN INTO SOUTHWEST AND
CENTRAL WI. EXPANDED BOTH IN TIME AND AREA THE ADVISORY TO HELP
BLEND WITH MKX AND DVN OFFICES. THE NEXT QUESTION IS IF ANY SNOW
CAN FALL WITH THE SHORTWAVE. THE 11.00Z GFS/CANADIAN/ECMWF ALL
PRODUCE A BAND OF LIGHT QPF...WITH SOUNDINGS SUGGESTING THE
FORCING IS MOSTLY CO- LOCATED WITH THE DENDRITIC GROWTH ZONE. THE
AFOREMENTIONED MODELS ALL SUGGEST A QUICK MOVING BAND...LIMITING
ACCUMULATIONS...BUT A FEW TENTHS SEEM REASONABLE. HAVE RAISED
PRECIPITATION CHANCES TOWARDS 60. NAM IS THE ONLY MODEL NOT
SHOWING ANY PRECIPITATION...BUT EVEN IT HAS INDICATIONS OF THE
FORCING.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 334 AM CST WED DEC 11 2013

MAIN LONG TERM FORECAST CONCERNS ARE ON MINIMAL PRECIPITATION
CHANCES THROUGHOUT.

SOME DEAMPLIFICATION OF THE FLOW ACROSS THE NORTHERN U.S. IS PROGGED
TO OCCUR THURSDAY THROUGH FRIDAY IN RESPONSE TO A TROUGH DROPPING
DOWN THROUGH THE PACIFIC NORTHWEST. THE SWITCH TO A ZONAL FLOW
PATTERN IN THE NORTHERN STREAM APPEARS TO HAVE PLENTY OF MID/UPPER
LEVEL MOISTURE...WHICH IS GOING TO MANIFEST ITSELF IN A LOT OF
CLOUDS. PRECIPITATION CHANCES OVERALL LOOK PRETTY MINIMAL...
THOUGH...AS PLENTIFUL DRY LOW LEVEL AIR IS IN PLACE. ADDITIONALLY...
FORCING APPEARS RESTRICTED TO SOME WEAK MID LEVEL FRONTOGENESIS
STRETCHING FROM NORTHERN/CENTRAL MN INTO NORTHERN WI THU NIGHT AND
FRIDAY. THIS FORCING COULD SQUEEZE OUT SOME SNOW...BUT CONFIDENCE IS
ONLY HIGH ENOUGH FOR A 20 PERCENT CHANCE NORTH OF HIGHWAY 10.
REGARDING THAT AFOREMENTIONED FRONTOGENESIS...THIS WILL OCCUR BEHIND
A COLD FRONTAL PASSAGE PROGGED TO MOVE THROUGH THE AREA THU NIGHT.
SO AFTER A WARMER THURSDAY IN RESPONSE TO LOW LEVEL WARM
ADVECTION...TEMPERATURES HEAD BACK DOWN THU NIGHT...BUT NOT NEARLY
AS COLD AS IT HAS BEEN. DESPITE THE COLD ADVECTION...TEMPERATURES
FRIDAY SHOULD REBOUND CLOSE TO THURSDAYS HIGHS.

FOR FRIDAY NIGHT AND SATURDAY...THE FOCUS HAS BEEN ON A SHORTWAVE
TROUGH AND GENERAL SYSTEM COMING OUT OF THE CENTRAL PLAINS. THIS
SHORTWAVE TROUGH IS CURRENTLY AN UPPER LOW SITTING OFF THE FAR
SOUTHERN CALIFORNIA COAST. 11.00Z ECMWF/GFS/CANADIAN HAVE TRENDED
SLIGHTLY FARTHER SOUTHEAST WITH THIS SYSTEM...AND AS SUCH...THE
PRECIPITATION ALSO MOVED A LITTLE FARTHER AWAY. THERE STILL ARE
INDICATIONS THAT THE MID LEVEL FRONTOGENESIS SITTING OVER NORTHERN
WI ON FRIDAY WILL SLIDE SOUTH OVER THE REST OF THE AREA FRIDAY
NIGHT...POSSIBLY SQUEEZING OUT A LITTLE LIGHT SNOW.
THEREFORE...HAVE HAD TO MAINTAIN SOME 20-40 PERCENT
CHANCES...HIGHEST BETWEEN 06-12Z SATURDAY. CHANCES CONTINUE
THROUGH THE DAY SATURDAY AND INTO SATURDAY NIGHT...MORE IN
RESPONSE TO A POTENT SHORTWAVE TROUGH DROPPING DOWN FROM MANITOBA
INTO UPPER MICHIGAN.

FOR SUNDAY AND BEYOND...SUNDAY IS LOOKING CHILLY AS THE POTENT
TROUGH BRINGS DOWN A BRIEF SHOT OF ARCTIC AIR WITH IT ON ITS BACK
SIDE. 850MB TEMPS FALL TO -14 TO -20C AT 18Z SUNDAY PER 11.00Z
ECMWF...COLDEST OVER TAYLOR COUNTY. MAY GET CLOSE FOR NEEDING A WIND
CHILL ADVISORY SUNDAY MORNING. A WARM ADVECTION PATTERN THEN LOOKS
TO ENSUE FOR SUNDAY NIGHT INTO MONDAY AS YET ANOTHER DECENT
SHORTWAVE TROUGH TRACKS FROM MANITOBA INTO UPPER MICHIGAN. FOLLOWED
CONSENSUS AND INCLUDED 20 PERCENT CHANCES FOR MONDAY. TEMPERATURES
MAY REBOUND HIGHER TOO THAN CURRENTLY FORECAST...BUT GIVEN HOW FAR
OUT THIS PERIOD IS IN THE FORECAST...STAYED CLOSER TO A MODEL
CONSENSUS WITH HIGHS IN THE 15-20 RANGE.

FOR THOSE LOOKING FOR A WARM-UP...THE ECMWF CONTINUES TO HINT AT ONE
FOR THE MIDDLE TO END OF NEXT WEEK AS A DEEP TROUGH FORMS OVER THE
WESTERN U.S.. THE CFS HAS ALSO BEEN ADVERTISING ABOVE NORMAL
TEMPERATURES DURING THIS SAME TIME PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1141 AM CST WED DEC 11 2013

COLD CYLCONIC NORTHWEST FLOW ALOFT WILL USHER IN ANOTHER WEAK
SHORTWAVE TROUGH INTO THE REGION THIS EVENING/OVERNIGHT. PLAN ON
VFR CONDITIONS TO DETERIORATE INTO MVFR RANGE AS THIS WAVE
APPROACHES IN THE 06-08Z TIME FRAME AS CLOUD HEIGHTS LOWER AND
VISIBILITY GETS REDUCED IN FALLING LIGHT SNOW. EXPECTING KLSE TO
BE IMPACTED BY THE FALLING SNOW MORE THAN KRST. NOT EXPECTING MORE
THAN 1/4-1/2 INCH. IT APPEARS THE LIGHT SNOW WILL EXIT EAST OF
THE AREA SOON AFTER DAYBREAK WITH LINGERING MVFR/IFR STRATUS
THROUGH THE REST OF THE MORNING HOURS.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WIND CHILL ADVISORY UNTIL 6 AM CST THURSDAY FOR WIZ017-029-
     032>034-041>044.

     WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST THURSDAY
     FOR WIZ053>055-061.

MN...WIND CHILL ADVISORY UNTIL 6 AM CST THURSDAY FOR MNZ079-086>088-
     094>096.

IA...WIND CHILL ADVISORY UNTIL 6 AM CST THURSDAY FOR IAZ008>010-018-
     019-029.

     WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST THURSDAY
     FOR IAZ011-030.

&&

$$

SHORT TERM...AJ
LONG TERM...AJ
AVIATION...DAS