FXUS63 KMPX 232159
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
359 PM CST WED DEC 23 2009
.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... /18Z TAF ISSUANCE/
LONG DURATION WINTER STORM WILL GETTING UNDERWAY THIS AFTERNOON.
UPPER LEVEL LOW PRESSURE OVER NEW MEXICO IS HELPING TO DEVELOP A
SFC INVERTED TROUGH FROM OKLAHOMA INTO IOWA. THIS TROUGH WILL
BECOME BETTER DEVELOPED THROUGH TONIGHT AND HELP FOCUS
PRECIPITATION DEVELOPMENT THIS AFTERNOON INTO THIS EVENING. SNOW
SHOWERS WILL EXPAND IN COVERAGE ACROSS SOUTH CENTRAL MN THIS
AFTERNOON WHILE A MORE SIGNIFICANT BAND OF PRECIPITATION MOVES
NORTHWARD FROM WESTERN IOWA. INITIALLY SNOW SHOWERS WILL BE SHORT
LIVED BUT WILL DROP VSBY DOWN TO 1 TO 2 SM. BEST FORCING ARRIVES
THIS EVENING AND OVERNIGHT WITH A PERIOD OF LIGHT TO MODERATE
SNOWFALL ACROSS THE TERMINALS WITH A MIX OF ICE PELLETS OR
FREEZING RAIN POSSIBLE ACROSS EXTREME SOUTH CENTRAL MN AND CENTRAL
WI. A BREAK IN THE FORCING AND A PERIOD OF DRIER AIR ALOFT ARRIVES
THURSDAY MORNING WHICH WILL DECREASE PRECIP INTENSITY AND POSSIBLY
LEADING TO SOME FZDZ SOUTHEAST. SNOW WILL PICK UP AGAIN LATE
THURSDAY AFTERNOON AND CONTINUE INTO FRIDAY MORNING BEFORE
DECREASING IN INTENSITY FRIDAY AFTERNOON. DETAILS FOLLOW...
KMSP...CIGS AROUND 3 KFT WILL DECREASE THROUGH THE AFTERNOON. MORE
INTENSE AND PERSISTENT SNOW SHOWERS WILL ARRIVE AFTER 22Z OR
BRINGING VSBY DOWN TO 1 TO 2 SM OR SO. BEST FORCING ARRIVES
AROUND 02 OR 03Z AND EXPECT 3/4SM VSBY WITH 1/2SM POSSIBLE AT
TIMES LATE THIS EVENING AND EARLY TONIGHT. FORCING WILL WANE
TOWARDS DAYBREAK THURSDAY LEADING TO LOWER SNOW INTENSITY AND SOME
IMPROVEMENT IN CIG/VSBY BUT MAGNITUDE IS NOT QUITE CLEAR. A SMALL
CHANCE FOR ICE PELLETS REMAINS THURSDAY MORNING AS WELL BUT
ATMOSPHERE LOOKS TO BE COLDER THAN EARLIER THOUGHT SO WILL STICK
WITH ALL SNOW. ANOTHER SURGE OF SNOW WILL ARRIVE LATE THURSDAY
MORNING AND CONTINUES THROUGH THURSDAY AFTERNOON WITH MORE 1/2 TO
1 SM VSBY. EAST-NORTHEAST WINDS WILL CONTINUE THROUGH THE PERIOD
WITH A SLIGHT SHIFT TO MORE A MORE NORTHERLY COMPONENT THURSDAY
AFTERNOON. SPEEDS OF 12 TO 15 KTS ARE EXPECTED WITH GUSTS TO THE
LOW 20S. SNOWFALL BY 12Z THURSDAY LOOKS TO BE IN THE 3 TO 5 INCH
RANGE. TOTAL SNOW AMOUNTS BY FRIDAY EVENING LOOK TO RANGE FROM 15
TO 20 INCHES.
KAXN/KSTC/KRWF...CONDITIONS WILL DETERIORATE THROUGH THE AFTERNOON
STARTING AT KRWF WHERE SNOW SHOWERS WILL BEGIN BY 19Z OR SO WITH
AN INCREASE IN SNOW COVERAGE LATER THIS AFTERNOON. HAZY CONDS WILL
CONTINUE AT KAXN AND KRWF AS WELL. SNOWFALL WILL EXPAND NORTHWARD
THROUGH LATE AFTERNOON WITH THE FOCUS FOR SNOW AT KRWF DURING THE
EVENING THE FROM MID EVENING THROUGH LATE TONIGHT AT KAXN/KSTC.
LULL EXPECTED FROM EARLY THURSDAY MORNING INTO LATE MORNING BUT
SNOW WILL LIKELY TO FALL JUST AT A REDUCED RATE. CIGS/VSBY WILL BE
TRICKY DURING THE LULL BUT LOOK TO HOVER AROUND THE IFR/MVFR
THRESHOLD. HEAVIER SNOW WILL RETURN AROUND MIDDAY AND CONTINUE
THROUGH THE AFTERNOON. EAST-NORTHEAST WINDS WILL CONTINUE THEN
TURN NORTHERLY THURSDAY. SNOWFALL FROM THIS AFTERNOON UNTIL 12Z
THURSDAY SHOULD RANGE FROM 4 TO 6 INCHES. STORM TOTAL SNOWFALL BY
FRIDAY EVENING LOOKS TO RANGE FROM 18 TO 24 INCHES WITH THE
HIGHEST AMOUNTS FROM KRWF TO KSTC.
KRNH/KEAU...KRNH WILL SEE MUCH THE SAME CONDITIONS AT KMSP WITH
SNOW INCREASING IN COVERAGE AND INTENSITY LATE THIS AFTERNOON WITH
THE BULK OF IT ARRIVING EARLY THIS EVENING...FOLLOWED BY A LULL
THURSDAY MORNING. KEAU WILL BE TRICKIER AS THE TERMINAL WILL BE
CLOSER TO WARMER AIR TRYING TO COME ON ALOFT. MAY SEE SOME FZDZ AS
FORCING INCREASE LATE THIS AFTERNOON BUT THE ATMOSPHERE IS LOOKING
COLDER THAN EARLIER FORECAST. THEREFORE EXPECT MAINLY SNOW THIS
EVENING AND TONIGHT BUT WILL NEED TO WATCH THE POSSIBILITY OF ICE
PELLETS. FORCING AND MOISTURE DECREASE THURSDAY MORNING BRINGING A
LULL IN THE PRECIP BUT THIS MAY BE THE BEST CHANCE FOR FZDZ AT
KEAU BEFORE SNOW INCREASES BY THURSDAY AFTERNOON. KEAU SNOW
AMOUNTS WILL HINGE ON PRECIP TYPE. IF CURRENT THINKING OF MAINLY
SNOW TONIGHT PANS OUT THEN 2 TO 4 INCHES ARE POSSIBLE BY 12Z
FRIDAY. WINDS WILL BE PRIMARILY EAST-NORTHEAST THROUGH THE PERIOD.
..MDB..
&&
.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
