FXUS63 KMPX 240549
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1149 PM CST WED DEC 23 2009
.UPDATE...
ADDED 06Z TAF DISCUSSION BELOW.
&&
.DISCUSSION...
THE MAKINGS FOR A MAJOR WINTER STORM FOR THE UPPER MISSISSIPPI
VALLEY CONTINUE TODAY. THE COUPLING OF TWO UPPER LOWS...ONE
CURRENTLY OVER SASKATCHEWAN AND THE OTHER OVER NEW MEXICO...IS
PROJECTED TO OCCUR TO OUR SOUTH BY CHRISTMAS DAY. DETAILS ARE A
LITTLE CLEARER TODAY...BUT PLENTY OF QUESTIONS REMAIN.
FIRST...IT IS BEGINNING TO LOOK LIKE THERE WILL BE THREE
WAVES OF PRECIPITATION OVER THE NEXT 48 HOURS. THE FIRST
ASSOCIATED WITH WARM ADVECTION TONIGHT. SNOW ACCUMULATION OF 3 TO
5 INCHES FORECAST FOR MUCH OF THE AREA WITH A LITTLE LESS OVER
WEST CENTRAL WISCONSIN AND FAR SOUTHERN MN DUE TO WARM AIR CONCERNS.
THE LOW LEVEL PROFILE IN TODAY'S MODEL RUNS ARE A LITTLE
COOLER...BUT THE NAM REMAINS THE WARMEST AND ON THE EDGE FOR
FREEZING RAIN...SLEET AND SNOW FROM AROUND ALBERT LEA THROUGH
MENOMONIE TO LADYSMITH. THEREFORE...CONTINUED A MIX THROUGH MUCH
OF THE FORECAST PERIOD FOR THESE AREAS BUT EMPHASIZED SNOW AS THIS
WAS THE PREDOMINATE TYPE.
THE SECOND AND THIRD ROUNDS OF PRECIPITATION ARE TOMORROW
AFTERNOON AND EVENING AND THEN LATE TOMORROW NIGHT AND PART OF
CHRISTMAS DAY WHEN A SIGNIFICANT PV ANOMALY APPROACHES FROM THE
SOUTH. TRENDS IN THE DETERMINIST RUNS TODAY ARE FOR MORE QPF. IN
FACT...ALL NOW HAVE 2 TO 2.5 INCHES ALONG AND WEST OF INTERSTATE
35 BY THE END OF CHRISTMAS DAY. 295/300K THETA CHARTS SHOW A LONG
DURATION OF UPGLIDE AND STRONG ADIABATIC OMEGA. MIXING RATIOS
CLIMB INTO THE 3 TO 4 G/KG RANGE AS PW PEAKS NEAR 250 PERCENT OF
NORMAL.
FORECAST TODAY WAS TO USE A BLEND OF THE PREVIOUS FORECAST ALONG
WITH WEIGHT ON THE DETERMINISTIC RUNS...WITH THE MOST WEIGHT
PLACED ON THE GFS. IN THE END...THIS RESULTED IN A FEW MORE
INCHES OF STORM TOTAL SNOW ACCUMULATION FOR THE FORECAST AREA.
GRIDDED SNOW ACCUMULATION BY FRIDAY EVENING RANGES FROM 20 TO 22
INCHES ALONG AND WEST OF INTERSTATE 35 TO THE DAKOTAS BORDER WITH
15 TO 20 INCHES EAST OF INTERSTATE 35 AND ALL OF WEST CENTRAL WI.
IT WAS INTERESTING TO NOTE TODAY THAT THE CIPS ANALOG SITE USING THE
12Z GFS ONLY FOUND ONE ANALOG AND THAT WAS THE HALLOWEEN BLIZZARD
(110191). THIS UNDERSCORES HOW DIFFICULT IT IS WITH THE PHASING OF UPPER
LOWS.
EVENTUALLY...THIS SYSTEM WILL PULL OFF TO THE EAST LATE IN THE
WEEKEND WITH DRY WEATHER INDICATED FOR EARLY NEXT WEEK. THE NEXT
THREAT FOR PRECIPITATION WOULD BE MID TO LATE NEXT WEEK.
&&
.AVIATION.../06Z TAF ISSUANCE/
SHRT TERM FORECAST CONCERN IS THE MIXED PRECIP THREAT POSSIBLY HEADED
TOWARD KMSP.. THERE IS THE POSSIBILITY OF ICE PELLETS FOR A FEW
HOURS BETWEEN 06Z AND 10Z. AFTER THIS FIRST WAVE OF PRECIP MOVES
THROUGH...THERE IS ALSO A MINOR THREAT OF FREEZING DRIZZLE. THIS
WILL NEED TO BE WATCHED IN THE MORNING HOURS. OTHERWISE THE WAVE
OF SNOW WILL CONTINUE TO MOVE INTO CENTRAL MN AND AFFECT
KSTC...AND KAXN WITH IFR CIGS AND VSBYS...POSSIBLY LIFR. THERE
WILL BE A BREAK IN THE INTENSITY OF PRECIP DURING THE MORNING INTO
THE AFTERNOON WITH STILL LOW END MVFR CIGS TO OCNL IFR WITH VSBYS
2-3 SM IN SNOW. LIGHT FREEZING RAIN OR DRIZZLE WILL ALSO AFFECT
KEAU DURING THE MORNING HOURS EXPECT THE NEXT WAVE OF SNOW TO MOVE
THURSDAY AFTERNOON AND CONTINUE THROUGH THE END OF THE PERIOD...AS
A STRONG LOW PRESSURE SYSTEM STARTS TO PIVOT NORTH THROUGH THE
MISSISSIPPI VALLEY. EXPECT IFR TO LIFR CIGS AND VSBYS OVER MOST
TAF SITES.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR ANOKA-BLUE
EARTH-BROWN-CARVER-CHIPPEWA-CHISAGO-DAKOTA-FARIBAULT-
FREEBORN-GOODHUE-HENNEPIN-ISANTI-KANDIYOHI-LAC QUI PARLE-LE
SUEUR-MARTIN-MCLEOD-MEEKER-NICOLLET-RAMSEY-REDWOOD-RENVILLE-
RICE-SCOTT-SHERBURNE-SIBLEY-STEARNS-STEELE-SWIFT-WASECA-
WASHINGTON-WATONWAN-WRIGHT-YELLOW MEDICINE.
WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR BENTON-DOUGLAS-
KANABEC-MILLE LACS-MORRISON-POPE-STEVENS-TODD.
WI...WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR BARRON-CHIPPEWA-
DUNN-EAU CLAIRE-PEPIN-PIERCE-POLK-RUSK-ST. CROIX.
&&
$$
JVM/JPR
