000 
FXUS63 KARX 150939 CCA
AFDLSE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
339 AM CST TUE JAN 15 2002

FORECAST CONCERNS THIS PACKAGE...CLOUDS TODAY...SNOW CHANCES LATER
TONIGHT/WED WITH NEXT SYSTEM APPROACHING FROM THE CENTRAL PLAINS...
TEMPS THRU THE PERIOD.

DATA ANALYSIS AT 08Z SHOWED THE SURFACE LOW OVER SOUTHERN LK HURON.
A TROUGH AXIS EXTENDED BACK ACROSS CENTRAL WI INTO CENTRAL MN. WV
IMAGERY SHOWED THE SHORTWAVE/SHEAR AXIS PUSHING SOUTHEAST ACROSS THE
AREA EARLY THIS MORNING. REGIONAL RADAR COMPOSITE AND SURFACE OBS
INDICATED WIDESPREAD -SN/FLURRIES IN DEEPER MOISTURE EAST OF THE
SHEAR AXIS THIS MORNING. RADAR LOOP HAS SHOWN A DECREASING TREND IN
INTENSITY/AREAL COVERAGE SINCE 06Z. FOG PRODUCT IMAGERY INDICATING
WIDESPREAD LOW SC DECK ACROSS THE WEST HALF OF THE REGION EARLY THIS
MORNING...NOT BEING HANDLED WELL BY THE MODELS. LOW CLOUD DECK WAS
KEEPING TEMPS ON THE WARM SIDE...WITH 08Z READINGS AT OR ABOVE
NUMERICAL GUIDANCE HIGHS FOR TODAY.

00Z MODELS SHOW NO GLARING INITIALIZATION ERRORS...AND AGAIN LOOK TO
REFLECT REALITY QUITE WELL EARLY THIS MORNING. AS POINTED OUT IN
PMDHMD...AVN LOOKS TO HAVE BETTER HANDLE ON STRENGTH OF TROUGH/UPPER
LOW OVER ID/NV EARLY THIS MORNING. IT IS THIS FEATURE THAT IMPACTS
OUR AREA LATER TONIGHT/WED WITH ANOTHER ROUND OF -SN. MODELS CONTINUE
TO TREND A BIT STRONGER/LESS SHEARED WITH THIS WAVE AS IT PUSHES
ACROSS THE UPPER MIDWEST ON WED. MINOR MODEL DIFFERENCE HAVE LITTLE
IMPACT ON THE WEATHER TODAY...BUT WILL FAVOR ETA FOR DETAILS. THE
RELATIVELY SMALL MODEL DIFFERENCES WITH STRENGTH/TIMING OF THE NEXT
SHORTWAVE...THE MOISTURE...AND POSITION OF LOW LEVEL FEATURES HAVE
IMPACTS STARTING LATE TONIGHT. AT THIS TIME WILL FAVOR BLEND OF ETA/
AVN SOLUTIONS FOR TONIGHT AND BEYOND.

FOR TODAY...SHORTWAVE/SHEAR AXIS AND DEEPER MOISTURE EXIT EAST OF
THE AREA THIS MORNING. WITH THE WIDESPREAD LOW SC DECK EXTENDING
BACK INTO THE EASTERN DAKOTAS...AND LACK OF ANY REAL STRONG SINKING
MOTION OR LOW LEVEL COLD ADVECTION BEHIND THE DEPARTING SHORTWAVE...
NOT TOO OPTIMISTIC ABOUT SEEING MUCH SUN ACROSS THE FORECAST AREA
TODAY. CLOUDS AND NORTHWEST WINDS TO KEEP TEMPS FROM WARMING MUCH
TODAY...WITH HIGHS ONLY A FEW DEGREES ABOVE CURRENT READINGS. THUS
FAVORED WARMER AVN-MAV GUIDANCE HIGHS FOR TODAY. MID/HIGH LEVEL
MOISTURE AHEAD OF THE NEXT TROUGH ALREADY SPREADS ACROSS THE AREA
THIS EVENING. WITH CONTINUED MOSTLY CLOUDY TO CLOUDY SKIES...AND
WIND BECOMING LIGHT...TEMPS NOT LIKELY TO FALL FAR TONIGHT AND
FAVORED THE WARMER MAV GUIDANCE FOR LOWS.

MODELS QUICKLY SPREAD LOW LEVEL WARM ADVECTION/ISENTROPIC LIFT AND
MID LEVEL Q-G CONVERGENCE ACROSS IA AND TOWARD THE FORECAST AREA
TONIGHT. BEST LOW LEVEL FORCING SKIRTS THE SOUTH END OF THE FORECAST
AREA EARLY WED...WHILE BEST UPPER LEVEL FORCING...PV ADVECTION/300MB
AGEOSTROPHIC FLOW/DIVERGENCE PASSES OVER THE AREA WED. BIGGEST
QUESTION REMAINS AMOUNT OF MOISTURE THE SYSTEM WILL HAVE TO WORK
WITH. ETA THE DRIEST OF THE 3 MODELS THIS MORNING...AND ITS SOLUTIONS
PAINTS THE LEAST PRECIP...AS EXPECTED. INITIAL LIFTING WILL GO TO
SATURATING THE RATHER DRY MID LEVELS...HOWEVER ALL MODELS GENERATE
SOME LIGHT PRECIP OVER THE SOUTHWEST HALF OF THE FORECAST AREA BY
12Z WED. ADDED POPS TO ZONES ACROSS SOUTHWEST HALF OF FORECAST AREA
FOR TONIGHT AND RAISED POPS TO LIKELY OR CATEGORICAL...ALONG WITH
ADDING ACCUMULATIONS...FOR MUCH OF THE AREA ON WED. FAVORED BLEND OF
MAV/NGM-FWC POPS AT THIS TIME. MID/UPPER TROUGH AXIS PASSES WED
AFTERNOON...WITH THE ACCUMULATING SNOWS TAPERING OFF. UNDER PLENTY OF
CLOUDS...FAVORED WARMER OF NUMERICAL TEMP GUIDANCE FOR WED AND WED
NIGHT.

FORECAST FOR WED NIGHT AND BEYOND OF MOSTLY CLOUDY WITH FLURRIES
LOOKS REASONABLE...AS MEDIUM RANGE MODELS CONTINUE TO STRUGGLE WITH
STRENGTH/TIMING OF SHORTWAVES THRU THE /DIRTY/ NORTHWEST FLOW.

.LSE...NONE.

RRS