FXUS63 KMPX 231208
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
608 AM CST WED DEC 23 2009
.DISCUSSION...
ATTENTION IS DRAWN TO A LARGE CLOSED LOW NEAR THE FOUR CORNERS
REGION ON EARLY MORNING WATER VAPOR IMAGERY. THIS FEATURE WILL DIG
SOUTH/EAST TODAY...EJECT NORTH ON THURSDAY...AND UNITE WITH A
SECONDARY LOW SINKING SOUTH FROM SASKATCHEWAN ON FRIDAY. ANTECEDENT
WARM AIR ADVECTION AND ISENTROPIC UPGLIDE AHEAD OF THE PRIMARY LOW
HAVE INITIATED AREAS OF FREEZING DRIZZLE AND A FEW FLURRIES
OVERNIGHT ACROSS SOUTHERN MN. NAM/GFS INDICATE THE LIFT/SATURATION
FROM 270K-280K WILL CONTINUE ALONG/SOUTH OF THE MN RIVER VALLEY
THIS MORNING...SO EXPECT A PERIOD OF FREEZING DRIZZLE THERE. WILL
HIGHLIGHT THE THREAT FOR SOME MINOR GLAZING WITH A WINTER WEATHER
ADVISORY. THE MID LEVELS SATURATE THIS AFTERNOON...SO THE PRECIP
TYPE SHOULD TRANSITION TO SNOW. WARM AIR ADVECTION BLOSSOMS THIS
EVENING AS PRECIPITABLE WATER VALUES NEAR 0.6 INCHES. HAVE MOVED
THE START TIME OF THE WARNING A FEW HOURS EARLIER...AS IT APPEARS
THAT SNOW SHOULD EXPAND FROM SOUTH TO NORTH ACROSS THE CWA BETWEEN
00Z AND 06Z. AFTER 06Z THURSDAY..CONTINUE TO EXPECT THE POTENTIAL
FOR SLEET/FREEZING RAIN ACROSS THE SOUTHEASTERN CWA AS AN ELEVATED
WARM LAYER WORKS IN...AND 0-6KM LAYER MAX WET BULB TEMPS APPROACH
0 CELSIUS. ON THURSDAY...CONTINUE TO EXPECT A RESPITE FROM THE
MORE MODERATE INTENSITY SNOWFALL...UNTIL THURSDAY NIGHT AND
FRIDAY WHEN THE DYNAMICS ASSOCIATED WITH THE AFOREMENTIONED
MERGING LOWS ARRIVE...AND A TROWAL NOSES INTO THE AREA. THE NEARLY
VERTICALLY STACKED SYSTEM WOBBLES OVER IA/MO/IN INTO THE
WEEKEND...AND CONTRIBUTES TO CONTINUED MEASURABLE SNOWFALL THROUGH
SATURDAY.
THIS STORM SYSTEM IS REMINISCENT OF THE INFAMOUS HALLOWEEN BLIZZARD
OF 1991...AS WAS CONFIRMED BY THE GFS212 36 HOUR CIPS ANALOGS.
OVER 27 INCHES OF SNOW WAS OBSERVED AT THE MSP AIRPORT DURING THAT
STORM...WHILE FREEZING PRECIPITATION PLAGUED A GOOD PORTION OF IA
INTO WESTERN WI. THE EXTENDED DURATION OF THE ANTICIPATED SNOWFALL
WITH THE IMPENDING SYSTEM...ALONG WITH THE IMPRESSIVE MOISTURE
PROGGED TO SURGE NORTHWARD FROM THE GULF...CONTINUES TO SUPPORT
ONE TO NEARLY TWO FOOT SNOWFALL ACCUMULATIONS BY THE TIME THE
HEAVIER SNOW WINDS DOWN ON FRIDAY NIGHT...WITH RECORD VALUES
CERTAINLY A POSSIBILITY. HAVE MAINTAINED STORM TOTAL SNOWFALLS
RANGING FROM 10 TO 20 INCHES...WITH THE LOWER ACCUMULATIONS
EXPECTED ACROSS SERN MN INTO WEST CENTRAL WI WHERE A DURATION OF
MIXED PRECIP WILL LIKELY RESULT IN LOWER TOTALS.
DUE TO THE CONTINUED FOCUS ON THE FIRST FOUR DAYS OF THE
FORECAST...LITTLE CHANGES WERE MADE TO THE FORECAST BEYOND SUNDAY.
&&
.AVIATION.../12Z TAF ISSUANCE/
A MAJOR WINTER STORM WILL IMPACT ALL AREA AIRPORTS TONIGHT THROUGH
CHRISTMAS NIGHT. PREVAILING IFR CONDITIONS IN SNOW ARE EXPECTED
FOR THE BETTER PORTION OF THAT TIME...WITH PERIODIC 1/2SM-3/4SM IN
SNOW EXPECTED WITH HEAVIER BOUTS. SIGNIFICANT ACCUMULATIONS OF
SNOW ARE EXPECTED. KEAU WILL LIKELY SEE A MIX TO SLEET AND/OR
FREEZING RAIN LATE TONIGHT INTO THU AND KMSP AND KRNH MAY ON THU.
FIRST...LOW CLOUDS EXPANDED NORTHEAST EARLY THIS MORNING BRINGING
IFR TO RWF AND MVFR TO MOST OF THE OTHER SITES. EXPECT LITTLE
CHANGE IN THE CLOUDS HEIGHTS THROUGH MID-AFTERNOON. CONFIDENCE IS
HIGH ON THIS AT MN TAF SITES. WI SITES MAY TEMPORARILY JUMP AROUND
3 KFT. PATCHES OF FREEZING DRIZZLE HAVE BEEN REPORTED NEAR KRWF
AND EXPECT THAT TO CONTINUE...ESPECIALLY LATE THIS MORNING WHEN
STRONGER LOW-LEVEL ASCENT IS FORECAST. THIS WILL CHANGE TO SNOW
DURING THE AFTN...LIKELY BY 19Z.
SNOW WILL SPREAD FROM SRN MN NORTHWARD TO CTRL MN FROM MID-
AFTERNOON THROUGH EARLY EVENING. ACCUMULATIONS ARE LIKELY AT KRWF
AFTER 23Z AND OTHER SITES BY 01Z TO 04Z. CONDITIONS SHOULD STAIR
STEP DOWN INTO IFR WITH AN LIFR ENHANCED AREA OF SNOW LIKELY
DURING THE LATE EVE AND OVERNIGHT. HAVE GENERALLY GONE 3/4SM TO
1SM AT ALL TAF SITES TO ACCOUNT FOR THIS. 1/2SM SNOW IS POSSIBLE
BUT NOT PROBABLE AT THIS TIME FOR THAT BOUT. THAT WILL BE LIKELY
THU AFTN AND NIGHT AND INTO CHRISTMAS WHEN THE MOST SIGNIFICANT
ACCUMULATIONS WILL OCCUR. A MIX WITH SLEET OR FREEZING RAIN LATE
TONIGHT AND THU MORNING IS PROBABLE AT KEAU AND COULD HAPPEN AT
KMSP. SLEET ACCUMS COULD OCCUR AT KEAU.
KMSP...MVFR CIGS WILL STICK AROUND UNTIL THROUGH THE DAY WITH
MODERATE CONFIDENCE THE EDGE OF THE MVFR CIGS WILL BE WITHIN 50
MILES EAST OF THE AIRPORT LIKELY THROUGH MUCH OF TODAY...BUT DO
NOT EXPECT THAT TO RETRACT WESTWARD MUCH. THE REDUCING VISIBILITY
SNOW ONSET TIME IS HIGHLY LIKELY TO BE BETWEEN 21Z AND 00Z. THERE
MAY BE SOME FLURRIES BEFORE THAT. IFR VISBY AND CIG SNOW LIKELY TO
SET IN BETWEEN 02Z AND 05Z. MORE INTENSE SNOW PROBABLE OVERNIGHT.
THIS IS WHEN QUICK ACCUMS OF TWO TO FOUR INCHES MAY OCCUR AND AN
AWW MIGHT BE NEEDED. AN AWW IS ALMOST A GIVEN FOR A LONGER
DURATION SOMETIME THU INTO FRIDAY. FREEZING PRECIPITATION IS NOT
ANTICIPATED THROUGH 10Z AND A SMALL CHANCE EXISTS TOMORROW
MORNING. A SLIGHTLY BETTER PROBABILITY FOR ICE PELLETS EXISTS
AFTER 10Z AND LASTING THROUGH THE DAY THU.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WARNING FROM 6 PM THIS EVENING TO 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.
WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR BLUE EARTH-
BROWN-FARIBAULT-FREEBORN-LAC QUI PARLE-MARTIN-REDWOOD-
WATONWAN-YELLOW MEDICINE.
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.
&&
$$
LS/MTF
