FXUS63 KARX 260838
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
238 AM CST SAT DEC 26 2009

.SHORT TERM...TODAY THROUGH MONDAY NIGHT

MAIN FORECAST CONCERN THROUGH THE PERIOD WILL BE DEEP CLOSED LOW AND
ITS AFFECT ON THE AREA WITH ON/OFF LIGHT SNOW.

SURFACE ANALYSIS EARLY THIS MORNING HAD A 996MB LOW OVER
SOUTHWEST IA WITH A COLD/OCCLUDED FRONT WRAPPED NORTH/NORTHEAST
INTO MN/NORTHWESTERN WI. WATER VAPOR IMAGERY HAS THE CENTER OF THE
MID-LEVEL LOW OVER NORTHERN IL. CURRENT RADAR SHOWING AREAS OF
LIGHT SNOW ACROSS THE AREA IN PV-ADVECTION AROUND THE MID-LEVEL
CIRCULATION. OTHERWISE...STRONG COLD AIR ADVECTION TOOK/TAKING
PLACE OVERNIGHT/EARLY THIS MORNING FROM SOUTH TO NORTH ACROSS THE AREA
BEHIND THE COLD/OCCLUDED FRONTAL PASSAGE. CURRENTLY TEMPERATURES
RANGED FROM THE TEENS ACROSS SOUTHERN SECTIONS OF THE FORECAST
AREA...TO THE LOWER 20S ACROSS THE NORTH.

26.00Z NAM/GFS AND 26.03Z SREF IN GOOD AGREEMENT THROUGH THE SHORT
TERM WITH HANDLING OF THE CLOSED LOW. 

FOR TODAY...THE CLOSED LOW WILL ROTATE FROM NORTHERN IL INTO
CENTRAL WI BY THIS AFTERNOON. MODELS SHOWING MOST OF THE QPF WILL
BE SOUTHEAST OF THE AREA ASSOCIATED WITH EMBEDDED SHORTWAVE AND
PV-ADVECTION...AND NORTHWEST OF THE AREA ASSOCIATED WITH ELONGATED
FETCH OF MOISTURE/TROWAL. IN BETWEEN...WILL LIKELY SEE A MINIMUM
IN SNOW ACTIVITY WITH JUST SCATTERED ON/OFF -SHSN.

THE LOW WILL SLOWLY DRIFT EAST OUT OF THE AREA INTO THE EASTERN
GREAT LAKES BY SUNDAY NIGHT. VARIOUS AND HARD TO TIME EMBEDDED
TROUGHS/LOBES OF PV- ADVECTION WILL ROTATE AROUND THE LOW TO FORCE 
SCATTERED -SHSN/AREAS OF -SN.

BY MONDAY...RIDGING ALOFT BEGINS TO BUILD EAST FROM THE PLAINS.
HOWEVER...THERE STILL SOME SIGNIFICANT LOW-LEVEL LAPSE RATES FOR
CU GENERATION AND PERHAPS A FEW FLURRIES ACROSS EASTERN PORTIONS
OF THE FORECAST AREA.

.LONG TERM...TUESDAY THROUGH FRIDAY

26.00Z GFS/25.12Z ECMWF IN DECENT AGREEMENT DURING THIS PERIOD. 

RIDGE OF HIGH PRESSURE WILL PROVIDE QUIET WEATHER THROUGH TUESDAY 
WITH TEMPERATURES EXPECTED TO BE RIGHT AROUND NORMAL SEASONAL LEVELS. 
ON WEDNESDAY /WEDNESDAY NIGHT...BOTH MODELS SHOWING A FAIRLY 
VIGOROUS MID-LEVEL TROUGH/SURFACE LOW DROPPING SOUTHEAST OUT OF THE 
CENTRAL CANADIAN PROVINCES INTO THE UPPER MIDWEST. MODELS SHOWING A 
PRETTY DECENT BLAST OF ARCTIC AIR MOVING INTO THE REGION WITH THE 
PASSAGE OF A STRONG SURFACE COLD FRONT ASSOCIATED WITH THIS FEATURE. 
GOOD FORCING/LIFT ASSOCIATED WITH THE WAVE/COLD FRONT IS EXPECTED TO 
GENERATE SOME SNOW SHOWER ACTIVITY. COLD CYCLONIC FLOW THEN LINGERS 
THROUGH THE REST OF THE PERIOD AS FAIRLY DEEP MID-LEVEL TROUGH SETS 
UP OVER THE UPPER MIDWEST/GREAT LAKES REGION. THIS IS EXPECTED TO 
CONTINUE -SN/-SHSN ACTIVITY. CURRENT EXTENDED GRIDDED FORECAST 
DATABASE HAS THIS HANDLED WELL EXCEPT FOR FRIDAY WHICH IS CURRENTLY 
DRY BUT MAY ALSO NEED A MENTION OF -SN/-SHSN AS WELL. WILL PASS
THIS ALONG TO THE DAYSHIFT FOR FURTHER ASSESSMENT.

&&

.AVIATION...CONDITIONS ARE EXPECTED TO VARY AND BE HARD TO PIN
DOWN AT TIMES DUE TO THE SCATTERED NATURE OF THE SNOW SHOWERS
THAT WILL BE PRESENT INTO SATURDAY NIGHT. MORE WIDESPREAD LIGHT
SNOW HAS PUSHED OFF TO THE NORTHWEST ALONG THE MAIN SURGE OF COLD
AIR THAT IS WRAPPING INTO THIS LOW PRESSURE SYSTEM THAT AFFECTED
THE REGION FOR THE PAST FEW DAYS. 26.00 FORECAST SOUNDINGS FROM
RST AND LSE INDICATE THAT DRIER AIR WILL BE ADVECTING INTO THE
REGION EARLY THIS MORNING AND SHOULD PROVIDE A BRIEF BREAK IN THE
LIGHT SNOW ACTIVITY FOR A PERIOD THIS MORNING. AS THE NEXT UPPER
LEVEL TROF ROTATES INTO THE REGION THIS AFTERNOON...EXPECT THAT
LIGHT SNOW SHOWER ACTIVITY WILL BE ON THE INCREASE WHICH SHOULD
BRING SOME LOWER VIS/CIG RESTRICTIONS ALONG WITH IT. SO...AM
EXPECTING FAIRLY VARIABLE CONDITIONS INTO SUNDAY MORNING WITH
MAINLY VFR CONDITIONS BUT DROPPING TO LOW END MVFR AT TIMES. WINDS
WILL BACK FROM THE EAST-SOUTHEAST EARLY THIS MORNING TO THE
NORTHEAST THIS AFTERNOON AND NORTHWEST OVERNIGHT INTO SUNDAY
MORNING...BUT SHOULD MAINLY STAY ON THE LIGHT SIDE LESS THAN 10
KTS.

EXPECT MAINLY VFR CONDITIONS WITH SOME VARIABLE DROPS TO LOW END 
MVFR AT TIMES INTO SUNDAY MORNING. 

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

$$

SHORT/LONG TERM...DAS
AVIATION..........HALBACH