FXUS63 KARX 102140
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
340 PM CST THU DEC 10 2009

.SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT

MAIN FOCUS OF THIS FORECAST PERIOD IS ON THE WIND CHILLS OVERNIGHT
INTO FRIDAY MORNING ALONG WITH THE CHANCES FOR AN ACCUMULATING
SNOW SATURDAY NIGHT INTO SUNDAY.

ALTO CU HAS BEEN ROLLING INTO THE REGION AHEAD OF A SHORT WAVE
TROF SLOWLY PROPAGATING THROUGH CENTRAL MINNESOTA. A FEW
AUTOMATED SITES ACROSS SOUTHERN MN HAVE BRIEFLY REPORTED SOME -SN
FROM TIME TO TIME...SO EXPECT THIS TREND TO CONTINUE EASTWARD INTO
OUR REGION TONIGHT. NAM AND GFS BUFKIT SOUNDINGS AREN'T SHOWING
MUCH IN THE WAY OF OMEGA WITH THIS TROF PASSAGE...SO AM NOT
EXPECTING ANY SNOW ACCUMULATION OVERNIGHT.

WITH TEMPERATURES EXPECTED TO DROP BACK BELOW ZERO TONIGHT AND
WINDS REMAINING AROUND 10 MPH OR SO...WIND CHILLS ARE EXPECTED TO
MAINLY DROP INTO THE -10 TO -20 RANGE ACROSS MOST OF THE FORECAST
AREA. THE COLDEST AREA APPEARS TO BE TAYLOR AND CLARK COUNTIES
WHERE WIND CHILLS OF -20 TO -25 ARE EXPECTED. THEREFORE...WILL BE
ISSUING A WIND CHILL ADVISORY STARTING AT 9PM TONIGHT RUNNING TO
9AM FRIDAY MORNING. THE MAIN LIMITING FACTOR IS CLOUD COVER WHICH
AT THIS POINT SEEMS TO BE AT LEAST SCATTERED TO BROKEN...BUT IF
THIS DECK FILLS IN OR DOESN'T CLEAR OUT OVERNIGHT...TEMPS MAY NOT
DROP AS LOW AS ADVERTISED. CONDENSATION PRESSURE DEFICITS INCREASE
OUT AHEAD OF THE TROF...BUT SHIFT OFF TO THE EAST BY DAYBREAK
FRIDAY. 

BEYOND THIS THE SHORT TERM GUIDANCE IS IN GOOD AGREEMENT FOR
GRADUALLY BRINGING WARMER AIR BACK INTO THE REGION AS A RIDGE AXIS
OF HIGH PRESSURE PROPAGATES THROUGH...WHICH WILL BRING SFC WINDS
BACK AROUND TO THE SOUTHWEST. 850MB TEMPS WILL GRADUALLY IMPROVE
FROM AROUND -22C TONIGHT TO -15C BY FRIDAY AFTERNOON...AND TO -5C
BY SATURDAY. HIGHS WILL CLIMB BACK INTO THE MID TO UPPER TEENS ON
FRIDAY AND MID TO UPPER 20S ON SATURDAY AS THE GRADUAL WARMING
CONTINUES. DID CONTINUE THE TREND OF KNOCKING A FEW DEGREES OFF OF
THE TEMPS WITH THE FRESH SNOW PACK IN TACT.

NEXT BEST CHANCE FOR AN ACCUMULATING SNOWFALL APPEARS TO BE ON
SATURDAY NIGHT INTO SUNDAY AS A SHORTWAVE TROF CURRENTLY OFF THE
COAST OF CALIFORNIA PROPAGATES INTO THE UPPER MISSISSIPPI RIVER
VALLEY. SHOULD SEE AN AREA OF LIGHT SNOW DEVELOP ALONG THE LEADING
EDGE OF WARM AIR ADVECTION AT 850MB AND AHEAD OF THIS MID LEVEL
TROF. THIS TROF SEEMS TO DEEPEN AS IT GETS EAST OF US...WHICH
WOULD MATCH UP WITH THE BEST ISENTROPIC FORCING...SO THE BETTER
CHANCES FOR AN ACCUMULATING SNOW WILL LIKELY BE OFF TO THE EAST IN
SOUTHERN WISCONSIN. FOR NOW...WILL BE GOING FOR ABOUT AN INCH OF
SNOW IN SOUTHWEST WISCONSIN.

.LONG TERM...MONDAY THROUGH THURSDAY

MAIN FORECAST CHALLENGE WITH THE EXTENDED PERIOD IS WITH TIMING
ANY SHORTWAVE TROFS THAT DIG DOWN FROM CANADA FOR NEXT WEEK. HAVE
MAINLY LEFT THE FORECAST OVER THIS PERIOD DRY...BUT ADDED A SLIGHT
CHANCE FOR SOME LIGHT SNOW ON THURSDAY FOR WHAT APPEARS TO BE THE
STRONGEST TROF COMING ACROSS. TEMPERATURES WILL BE BELOW NORMAL
THROUGH MOST OF THE WEEK WITH NORTHWESTERLY UPPER LEVEL FLOW IN
PLACE. THE COLDEST AIR WILL LIKELY TUESDAY MORNING INTO WEDNESDAY
AS THE CORE OF A HIGH PRESSURE SYSTEM MOVES ACROSS THE PLAINS.

&&

.AVIATION...TONIGHT AND FRIDAY

LATEST WATER VAPOR SATELLITE IMAGERY INDICATING A COUPLE OF WEAK 
SHORTWAVE TROUGHS EMBEDDED IN NORTHWEST FLOW ALOFT OVER THE NORTHERN 
PLAINS AND UPPER MIDWEST. FIRST IMPULSE OVER CENTRAL MINNESOTA 
PRODUCING SCATTERED STRATOCUMULUS DECK CLOUDS AND A FEW FLURRIES 
OVER THE MINNESOTA RIVER VALLEY AND SOUTH CENTRAL MINNESOTA EARLY 
THIS AFTERNOON. CEILINGS RANGE FROM 2500 TO 5000 FEET WITHIN 
STRATOCUMULUS DECK. THIS DECK CLOUDS/WEAK WAVE WILL MOVE EAST OVER 
THE AREA THROUGH THE AFTERNOON AND EARLY EVENING HOURS. SKY 
CONDITIONS ARE EXPECTED TO REMAIN SCATTERED AND CEILINGS REMAIN VFR 
AT BOTH KRST AND KLSE TAF SITES THIS AFTERNOON AND EVENING. SKY MVFR 
CONDITIONS MAY BE POSSIBLE THOUGH FOR A SHORT DURATION TIME. HAVE 
KEPT VFR CONDITIONS THROUGH THIS EVENING. NEXT SHORTWAVE OVER THE 
WESTERN DAKOTAS PUSHES EAST INTO THE CENTRAL MINNESOTA AND NORTHERN 
WISCONSIN. WEAK FORCING IN ASSOCIATION WITH SHORTWAVE TROUGH SHOULD 
ALLOW FOR THE POSSIBILITY OF FLURRIES ACROSS THE REGION. DUE TO  
TIMING ISSUES AND SHORT DURATION OF MVFR CONDITIONS...HAVE KEPT 
SCATTERED 2000-2500 FEET AT BOTH KRST AND KLSE TAF SITES AFTER 07Z 
FRIDAY.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...WIND CHILL ADVISORY FROM 9 PM THIS EVENING TO 9 AM CST FRIDAY 
     FOR WIZ017-WIZ029.

MN...NONE.
IA...NONE.
&&

$$

SHORT/LONG TERM...HALBACH
AVIATION...DTJ