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000
FXUS63 KARX 100800
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
200 AM CST WED FEB 10 2010

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT

FORECAST CONCERNS SHIFT TO LIGHT SNOW CHANCES MOVING IN FRI...ALONG
WITH COLD TEMPERATURES EXPECTED FOR THU MORNING.

THE UPPER LEVEL SHORTWAVE TROUGH RESPONSIBLE FOR MUCH OF THE
SNOWFALL OVER THE PAST COUPLE DAYS WAS CHURNING EAST OVER THE OH
RIVER VALLEY EARLY THIS MORNING...PER THE LATEST WATERVAPOR
SATELLITE IMAGERY. LATEST 88-D RADAR IMAGERY PLACES THE BULK OF THE
SNOW OVER EASTERN WI...WITH A FEW STRAY LIGHT SNOW SHOWERS OVER
CENTRAL WI. MEANWHILE...MOST OF MN WAS UNDER CLEAR SKIES PER THE
FOG/STRATUS SAT PRODUCT...THANKS TO AN AREA OF HIGH PRESSURE
BUILDING OVER THE NORTHERN PLAINS.

THE HIGH WILL CONTINUE BUILD EAST...MOVING OVER THE UPPER
MISSISSIPPI RIVER VALLEY/WESTERN GREAT LAKES TODAY/THU. SKIES WILL
CONTINUE TO CLEAR FROM WEST TO EAST TODAY...WITH A MOSTLY CLEAR
OVERNIGHT ON TAP. THIS COULD MAKE FOR A RATHER COLD NIGHT...WITH THE
CLEAR CONDITIONS...LIGHT WINDS AND FRESH SNOW COVER PROMOTING GOOD
RADIATIONAL COOLING. TEMPERATURES ARE IN THE SINGLE DIGITS TO LOWER
TEENS BELOW ZERO OVER THE NORTHERN PLAINS UNDER THE HIGH CENTER
EARLY THIS MORNING...AND THIS AIR MASS WILL BE SHIFTING OVER EASTERN
MN FOR WED MORNING. NUMERICAL GUIDANCE LOOKS MUCH TOO WARM...AND
WILL CONTINUE TO UNDERCUT BY 5 TO 10 DEGREES.

BOTH THE 10.00Z GFS AND NAM SOLUTIONS WANT TO BRING THE NEXT UPPER
LEVEL SHORTWAVE TROUGH SOUTHEAST ACROSS THE NORTHERN PLAINS ON
THU...SPINNING ACROSS IA ON FRI. SOME DIFFERENCES...WITH THE GFS A
BIT MORE WEST THAN THE NAM...BUT BOTH HAVE A SIMILAR
STRENGTH...WHICH IS MUCH WEAKER THAN THE EXITING STORM SYSTEM. SOME
WEAK QG CONVERGENCE WITH THIS FEATURE...MOSTLY IN THE 700-300 MB
LAYER. LOW LEVEL THERMODYNAMICS ARE ALSO RATHER WEAK...WITH SOME
HINTS OF LOW LEVEL WARMING IN THE 925-850 LAYER AND UPGLIDE ON THE
280-295 K SFCS. BUFKIT SOUNDINGS AND TIME/HEIGHT X-SECTION DO
INCREASE THE SATURATION AS THIS UPPER LEVEL FEATURES MOVES IN...AND
WOULD SUPPORT SOME LIGHT SNOW CHANCES. THE 00Z GFS IS FASTER WITH
BRINGING ITS LIGHT SNOW CHANCES INTO THE REGION...ALTHOUGH GENERALLY
CONFINED TO AND WEST OF THE MISSISSIPPI RIVER. THE 00Z NAM IS
SLOWER...AND MORE SIMILAR TO THE 09.21Z SREF AND ECMWF. WILL SIDE
TOWARD THE CONSENSUS FOR TIMING...WITH THE BETTER LIGHT SNOW
CHANCES COMING ON FRI. AS FOR AMOUNTS...COBB OUTPUT ONLY LAYING DOWN
AROUND 1/2 INCH RIGHT NOW...WHICH IS PROBABLY REASONABLE GIVEN THE
WEAK FORCING AND SPEED OF THE SYSTEM.

.LONG TERM...SATURDAY THROUGH TUESDAY

A BIT BETTER CONTINUITY BETWEEN THE GFS AND ECMWF SOLUTIONS THIS GO
AROUND. BOTH CAPTURE A SHORTWAVE TROUGH AND DROP IT ACROSS THE
NORTHERN PLAINS/UPPER MISSISSIPPI RIVER VALLEY FRI NIGHT/SAT. THE EC
IS A BIT FASTER THAN THE GFS...BUT BOTH KEEP THE HEART OF THE UPPER
SYSTEM JUST WEST OF THE LOCAL AREA. THE TRACK COULD BRING SOME LIGHT
SNOW CHANCES TO THE FORECAST AREA...BUT THE BETTER CHANCES WILL BE
OFF TO THE WEST. A SOMEWHAT DIRTY NORTH TO NORTHWEST FLOW A LOFT
WILL THEN PERSIST THROUGH THE EARLY PART OF THE NEW WORK...BUT
TIMING AND PLACEMENT ON ANY OF THE PERTURBATIONS IN THE FLOW ARE
PROBLEMATIC AT THIS TIME. BOTH MODELS DO BUILD A SFC RIDGE ACROSS
THE REGION STARTING SUNDAY...AND THIS MAKE KEEP THE LOCAL AREA DRY
REGARDLESS OF THE UPPER AIR PATTERN. WILL STICK WITH THE DRY
SCENARIO AFTER SAT FOR NOW.

&&

.AVIATION...

A RIDGE OF ARCTIC HIGH PRESSURE OVER THE PLAINS WILL MOVE INTO THE
TAF SITES TONIGHT. EXPECT DRY CONDITIONS DUE TO DRY AIR ASSOCIATED
WITH THE RIDGE MOVING IN. HOWEVER...CLOUD FORECAST IS TRICKY...DUE
TO NORTHERLY FLOW AHEAD OF THE RIDGE BRINGING LAKE EFFECT CLOUDS
FROM LAKE SUPERIOR SOUTHWARD. LOOK FOR MVFR CEILINGS AT KLSE TO
STAY IN PLACE THROUGH MID MORNING...THEN TURN VFR AS THE LAKE CLOUDS
BECOME SCATTERED FROM DAYTIME HEATING AND WINDS BACKING TOWARDS THE
NORTHWEST. LAKE CLOUDS SHOULD REMAIN EAST OF KRST GIVEN THE WIND
DIRECTION. OTHERWISE...VFR CEILINGS AND VISIBILITIES ARE EXPECTED
THROUGH TONIGHT AT BOTH TAF SITES...ALONG WITH DIMINISHING WINDS.

&&

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

&&

$$

SHORT/LONG TERM... RIECK
AVIATION.......... AJ