FXUS63 KARX 040914
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
314 AM CST FRI DEC 4 2009

.SHORT TERM...TODAY THROUGH SUNDAY NIGHT

MAIN FORECAST CONCERN IS ON TEMPERATURES AND SNOW CHANCES TODAY AND
AGAIN SUNDAY AND SUNDAY NIGHT.

WATER VAPOR IMAGERY AT 07Z SHOWS SHORTWAVE MOVING ACROSS SOUTHERN
WISCONSIN. LINGERING FLURRIES BEING PICKED UP BY RADAR AND SURFACE
REPORTS ACROSS MUCH OF THE FORECAST AREA. INFRARED SATELLITE
IMAGERY SHOWING CLOUDY SKIES ACROSS MUCH OF THE REGION...BUT SOME
CLEARING WAS OCCURRING ACROSS SOUTHERN MINNESOTA AND NORTHEAST IOWA.

04.12Z MODELS IN GOOD AGREEMENT THROUGH 78 HOURS...BUT STILL
SHOWING PROBLEMS BEYOND THAT WITH THE SYSTEM TO AFFECT THE AREA
SUNDAY NIGHT. NO CLEAR CUT FAVORITE AS GFS THE FURTHEST SOUTH WITH
THE SURFACE LOW AND HAVE GENERALLY TAKEN A COMPROMISE WITH THE
TRACK.

IN THE NEAR TERM...BACK EDGE OF CLOUDS PUSHING INTO
SOUTHEAST MINNESOTA AND NORTHEAST IOWA EARLY THIS MORNING.
WILL LIKELY SEE SOME BREAKS EARLY ACROSS THESE AREAS...BUT
SKIES SHOULD QUICKLY CLOUD BACK UP LATER THIS MORNING. IN
THE MEANTIME...SHORTWAVE TROUGH WILL TRANSLATE INTO THE EASTERN GREAT
LAKES TODAY WITH CYCLONIC FLOW CONTINUING OVER THE AREA. ANOTHER
SHORTWAVE ROTATES SOUTHWARD ACROSS LAKE SUPERIOR TONIGHT. 300MB-700MB
QG CONVERGENCE CROSSES THE NORTHERN SECTIONS TODAY AND TONIGHT. WEAK
OMEGA SIGNAL ACROSS THE NORTH ALONG WITH BOTH THE NAM AND GFS
PAINTING SOME QPF. THUS HAVE GONE WITH LOWER END POPS FOR MEASURABLE
SNOW ACROSS THE NORTH WITH FLURRIES ELSEWHERE. WEAK COLD ADVECTION
ALONG WITH SNOW COVER WILL KEEP TEMPERATURES DOWN TODAY AND LOWERED
THEM A FEW DEGREES FROM THE PREVIOUS FORECAST.

QUIET WEATHER THEN EXPECTED SATURDAY...BUT TEMPERATURES WILL REMAIN
BELOW NORMAL STRUGGLING TO MAKE THE FREEZING MARK AS SNOW COVER
CONTINUES TO IMPACT DEGREE OF WARMING. GUIDANCE VALUES AGAIN LOOK
TO WARM AND UNDERCUT BY 2 TO 4 DEGREES.

ATTENTION THEN TURNS TO SYSTEM THAT AFFECTS THE AREA LATE SUNDAY AND
SUNDAY NIGHT. DEEP QG CONVERGENCE OVERSPREADS THE AREA AHEAD OF THE
APPROACHING SHORTWAVE. MODELS IN DISAGREEMENT WITH THE TRACK OF THE
SURFACE LOW...BUT INDICATIONS ARE IT COULD BRING A SWATH OF
ACCUMULATING SNOW TO THE SOUTHERN SECTIONS OF THE FORECAST AREA.
WITH THE MODEL DIFFERENCES DID NOT MAKE ANY CHANGES TO THE
POP/WEATHER GRIDS IN THIS TIME FRAME WITH THE HIGHER PROBABILITIES
RESIDING IN AREAS SOUTH OF INTERSTATE 90...BUT STILL IN THE CHANCE
CATEGORY.

.LONG TERM...MONDAY THROUGH THURSDAY

04.00Z GFS AND ECMWF SHOWING GOOD CONSENSUS IN LIFTING A POTENT
SHORTWAVE OUT OF THE SOUTHWEST AND TOWARD THE AREA TUESDAY AND
WEDNESDAY. ATTENDANT SURFACE OW DEEPENS TUESDAY NIGHT WITH THE GFS
INDICTING PRESSURES OF 984 MB...WHILE THE ECMWF LOWERS PRESSURES
TO 978MB. TRACK IS CONSISTENT AND FURTHER NORTH THEN PREVIOUS RUNS...
BRINGING IT ACROSS NORTHERN ILLINOIS. LOW LEVEL THERMAL PROFILES
INDICATE THAT PRECIPITATION WOULD FALL AS ALL SNOW. THIS STORM HAS
THE POTENTIAL TO BRING SIGNIFICANT SNOW TO THE AREA...AND WITH THIS
IN MIND AND AFTER COLLABORATION WITH SURROUNDING OFFICES DID RAISE
POPS TUESDAY THROUGH WEDNESDAY.

&&

.AVIATION...

SHORTWAVE RESPONSIBLE FOR THE -SN/FLURRIES AND THE MVFR/LCL IFR
CIGS/VSBYS THU AFTERNOON/EVENING WILL CONTINUE TO ROTATE AWAY FROM
THE AREA. HOWEVER...WITH MID LEVEL CYCLONIC FLOW REMAINING OVER THE
AREA TODAY INTO TONIGHT...SOME FLURRIES LIKELY TO LINGER IN/AROUND
THE AREA. WITH LACK OF STRONGER FORCING/LIFT AND SHALLOWER MOISTURE
OVER THE AREA...ANY VSBY RESTRICTIONS WITH THE FLURRIES EXPECTED TO
BE MINIMAL. CLOUD DECK MORE PROBLEMATIC TODAY. CLEAR SKIES JUST TO
THE WEST OF THE FCST AREA EARLY THIS MORNING...NOT BEING HANDLED
WELL BY FCST MODELS. SOME OF THIS MAY WORK INTO KRST AREA THIS
MORNING...BUT CONFIDENCE NOT HIGH WITH THE MID LEVEL CYCLONIC FLOW
AND MODEL SOUNDINGS/RH PROGS INDICATING ABUNDANT MOISTURE IN THE
925-850MB LAYER TO REMAIN OVER THE AREA TODAY/TONIGHT. THE OTHER
ISSUE WITH THE CLOUDS IS CIG HGTS IN THE 2K TO 4K FT RANGE OVER AND
UPSTREAM OF THE AREA. WITH MORE WESTERLY FLOW IN THE LOWER LEVELS
TODAY AND THE CLEAR SKIES TO THE WEST EARLY THIS MORNING...WOULD
EXPECT CIGS TO RISE INTO VFR RANGE TODAY...THEN WITH PASSAGE OF
ANOTHER WEAK MID-LEVEL TROUGH...DROP INTO THE 2K-3K FT RANGE TONIGHT.
DRIER AIR IN THE 925-700MB LAYER AND VFR CONDITIONS LOOKS TO SPREAD
ACROSS THE AREA FOR SAT.

&&

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

$$

SHORT/LONG TERM...RABERDING
AVIATION...RRS