FXUS63 KMPX 221802 CCA
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1202 PM CST TUE DEC 22 2009

.DISCUSSION...
THE MAIN FORECAST CONCENTRATION IS ON THE POTENTIAL FOR A WHOPPER
OF A WINTER STORM TO IMPACT THE REGION OVER THE CHRISTMAS HOLIDAY.

IN THE MEANTIME...THE FOCUS IS ON THE AREA OF SNOW OVER
CENTRAL/SOUTHERN MN ASSOCIATED WITH A SHORTWAVE MOVING ACROSS THE
SD/NE/IA REGION. WEAK UPGLIDE ON THE 270K- 285K SURFACE LINGERS
OVER SOUTHERN MN TODAY AS THE WAVE PASSES TO THE SOUTH...SO
ANTICIPATE FLURRIES AND/OR LIGHT SNOW SHOWERS TO BE A REALITY
GENERALLY ALONG/SOUTH OF THE INTERSTATE 94 CORRIDOR. BUFKIT
SOUNDINGS INDICATE LOSS OF SATURATION IN THE DENDRITIC GROWTH ZONE
/AROUND -10C/ AFTER 15Z...SO COULD SEE SOME FREEZING DRIZZLE AS
WELL.

NOW...ON TO THE MAIN FOCUS. 10Z WATER VAPOR IMAGERY SHOWS A
STRONG UPPER LEVEL LOW OVER THE PACIFIC NORTHWEST. THIS FEATURE
WILL PLUNGE SOUTH ACROSS THE WEST COAST TODAY...CROSS THE
FOUR CORNERS REGION TONIGHT...AND EJECT NORTHEAST TO THE PLAINS
REGION ON WEDNESDAY. SINCE THIS SYSTEM HAS BEEN HIGHLY
ADVERTISED...WILL CONCENTRATE ON THE TRENDS/CHANGES THAT HAVE BEEN
OBSERVED OVERNIGHT. THE MAIN ITEM OF NOTE...WAS THE WESTWARD SHIFT
THAT 00Z DETERMINISTIC MODELS MADE. A 50-100 MILE WEST/NORTHWEST
SHIFT WAS NOTED IN THE DPROG/DT OF THE NAM/GFS SFC LOW LAST
NIGHT...WITH 00Z RUNS BRINGING IT INTO SERN MN BY 12Z FRIDAY. THIS
WOULD DRAW WARMER AIR INTO THE SERN PORTION OF THE CWA...WHICH
WOULD LIKELY MEAN FREEZING/MIXED PRECIPITATION FOR THE FIRST PART
OF THE EVENT. ADDITIONALLY...SNOWFALL AMOUNTS COULD BE FURTHER
REDUCED IF THE DRY SLOT WORKS INTO SRN/ERN MN AND WRN WI. 

THERE IS HIGH CONFIDENCE THIS SYSTEM WILL DUMP DOUBLE DIGIT
SNOWFALL AMOUNTS SOMEWHERE CLOSE TO /IF NOT IN/ THE AREA...AS A
PROLONGED PERIOD OF FRONTOGENESIS COMBINES WIT A PLENTIFUL FETCH OF
MOISTURE. THERE COULD ALSO BE MINOR ICE ACCUMULATIONS FROM
SOUTH/EAST CENTRAL MN INTO WEST CENTRAL WI. WINTER STORM WATCH 
THEREFORE LOOKS GOOD...AND WILL HOPEFULLY BE ABLE TO NARROW SOME OF 
THE DETAILS TODAY AS THE SYNOPTIC PATTERN BECOMES CLEARER. 21Z SREF 
PLUME DIAGRAMS ILLUSTRATED THE POTENTIAL FOR ABUNDANT SNOWFALL WITH 
THIS SYSTEM...PER MEAN/MAX SNOW PRECIP VALUES OF 1.18/1.54 INCHES 
FOR MVE /MONTEVIDEO/. THEY ALSO INDICATED THE POTENTIAL FOR 
SLEET/FZRA BETWEEN WEDNESDAY EVENING AND THURSDAY EVENING AT MVE AND 
MSP. HAVE INCLUDED MIXED PRECIP FROM WEDNESDAY EVENING THROUGH 
FRIDAY FROM SOUTH/EAST CENTRAL MN INTO WEST CENTRAL WI.

&&

.AVIATION.../18Z TAF ISSUANCE/ 
FLYING CONDITIONS LOWERING AS LOW PRESSURE SYSTEM DEVELOPS OVER THE 
WESTERN U.S. DURING THE PERIOD.  EASTERLY AIRFLOW WILL CONTINUE OVER 
THE TAF SITES WITH LOW LEVELS MOISTENING AHEAD OF PRECIP BAND 
DEVELOPS LATE IN THE DAY WEDNESDAY AND WEDNESDAY NIGHT.  WEATHER 
CONDS LOWERING TO MVFR TO IFR CONDITIONS BY DAYBREAK WEDNESDAY.  
SOME PATCHY FREEZING DRIZZLE DEVELOPING OVER SOUTHWEST HALF OF THE 
MN. SOMEWHAT DRIER AIR WILL KEEP THE FREEZING DRIZZLE FROM REACHING 
OR MOVING INTO WESTERN WISCONSIN OVERNIGHT. 

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH FRIDAY
     AFTERNOON FOR ANOKA-BENTON-BROWN-CARVER-CHIPPEWA-CHISAGO-
     DAKOTA-DOUGLAS-GOODHUE-HENNEPIN-ISANTI-KANABEC-KANDIYOHI- 
     LAC QUI PARLE-LE SUEUR-MCLEOD-MEEKER-MILLE LACS-MORRISON-
     NICOLLET-POPE-RAMSEY-REDWOOD-RENVILLE-RICE-SCOTT-SHERBURNE-
     SIBLEY-STEARNS-STEVENS-SWIFT-TODD-WASHINGTON-WRIGHT-YELLOW
     MEDICINE.

     WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY 
     AFTERNOON FOR BLUE EARTH-FARIBAULT-FREEBORN-MARTIN-STEELE-
     WASECA-WATONWAN.

WI...WINTER STORM WATCH FROM WEDNESDAY EVENING THROUGH FRIDAY 
     AFTERNOON FOR BARRON-CHIPPEWA-DUNN-EAU CLAIRE-PEPIN-PIERCE-
     POLK-RUSK-ST. CROIX.

&&

$$

LS/MTF