FXUS63 KMPX 221049
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
449 AM 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 /NEW ULM/. 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.../06Z TAF ISSUANCE/
MAIN CONCERN FOR THE REMAINDER OF THE NIGHT IS LIGHT SNOW MOVING
ACROSS KRWF-KMSP-KRNH REGION. BEST SATURATION NOW MOVING ACROSS THE
CWA NOW-12Z TUE. WILL MENTION SOME IFR CONDS OVER THIS REGION OF
THE FA. DRIER AIR TO THE EAST AND NORTH WILL LIMIT CIGS TO MVFR.
MAY SEE SOME BKN CIGS OVER THE FAR NORTHEAST FA DURING TUE
MORNING...BUT WILL MAINTAIN MVFR CIGS FOR THE MOST PART ACROSS THE
ENTIRE AREA. WEAK LIFT INDICATED ON ISENTROPIC CHARTS COULD
CONTINUE FLURRY THREAT INTO MUCH OF THE DAY. SHOULD BE WIDELY SCT
HOWEVER SO WILL LEAVE OUT OF TAF SITES FOR NOW. CIGS MAY DROP OFF
TO IFR AGAIN TUE NIGHT AS LIFT INTENSIFIES AHEAD OF DEVELOPING
STORM. EASTERLY SFC FLOW WILL CONTINUE THOUGH THE
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER WEATHER ADVISORY UNTIL 9 AM CST THIS MORNING FOR BLUE
EARTH-FARIBAULT-FREEBORN-LE SUEUR-RICE-STEELE-WASECA.
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/DWE
