FXUS63 KMPX 240006
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
605 PM CST WED DEC 23 2009

.UPDATED FOR AVIATION 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... /00Z TAF ISSUANCE/ 

KMPX - INITIAL SURGE OF MOISTURE/SNOW LIFTING NORTH ABOUT 18KTS ON 
KMSP RADAR.  THIS SHOULD AFFECT THE AIRPORT AREA BETWEEN 0030Z-07Z 
THIS EVENING WITH LIFR CIGS/VSBY.  SNOWFALL RATES ARE AROUND 3/4 
INCH AN HOUR. EXPECT AROUND 2-3 INCHES SNOW THROUGH MIDNIGHT.  MAY 
BE A LULL IN THE SNOW AFTER 07Z...WITH PERHAPS A BIT OF SPOTTY 
-FZDZ.  LEFT THIS OUT OF THE TAF FROM NOW.  CONTINUING TO MONITOR 
THE UPPER CIRCULATION OVER IOWA.  THIS MAY DEVELOP ANOTHER SNOW BAND 
LATE TONIGHT...DEVELOPING MAINLY AFTER 12Z.  WILL CONTINUE TO 
MONITOR.  OTHERWISE...MODELS SUGGEST NEXT SIGNIFICANT SNOW INCURSION 
WOULD COME IN AFTER 18Z THU AND THEN AFTER 00Z FRI.    

REST OF FA SHOULD SEE LOWERING CIGS/VSBY IN -SN WITH MODERATE SNOW 
AFFECTING KRWF-KAXN-KRNH AREA THIS EVENING INTO EARLY MORNING.  MAY 
SEE SOME -FZRAPL INTO THE KEAU MAINLY AFTER 12Z FRI AS THICKNESSES 
CONTINUE TO RISE.  NO SIGNIFICANT IMPROVEMENT IN FLYING CONDITIONS 
EXPECTED THRUT TAF FCST PERIOD. 

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WARNING UNTIL 6 AM CST SATURDAY FOR BLUE EARTH-
     BROWN-FARIBAULT-FREEBORN-LAC QUI PARLE-LE SUEUR-MARTIN-
     NICOLLET-REDWOOD-RENVILLE-RICE-SIBLEY-STEELE-WASECA-
     WATONWAN-YELLOW MEDICINE.

     WINTER STORM WARNING FROM MIDNIGHT TONIGHT TO 6 AM CST SATURDAY 
     FOR BENTON-DOUGLAS-KANABEC-MILLE LACS-MORRISON-POPE-STEVENS-
     TODD.

     WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 AM CST SATURDAY 
     FOR ANOKA-CARVER-CHIPPEWA-CHISAGO-DAKOTA-GOODHUE-HENNEPIN-
     ISANTI-KANDIYOHI-MCLEOD-MEEKER-RAMSEY-SCOTT-SHERBURNE-
     STEARNS-SWIFT-WASHINGTON-WRIGHT.

WI...WINTER STORM WARNING FROM 9 PM THIS EVENING TO 6 AM CST SATURDAY 
     FOR BARRON-CHIPPEWA-DUNN-EAU CLAIRE-PEPIN-PIERCE-POLK-RUSK-
     ST. CROIX.

&&

$$

RAH/MDB