FXUS63 KMPX 090617
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1217 AM CST WED DEC 9 2009
.UPDATE...
06Z AVIATION DISCUSSION ADDED BELOW.
&&
.DISCUSSION...
THE MAJOR WINTER STORM HAS BEGUN ACROSS THE AREA AND WILL LAST
THROUGH WEDNESDAY. CHANGES WERE TO INCREASE SNOWFALL
TOTALS...EXPAND AREA OF 25-35 MPH WINDS DURING WEDNESDAY...AND
ACCORDINGLY INCREASE THE COVERAGE AREA OF WARNINGS.
SIGNIFICANT SYSTEM ENTERING THE CENTRAL PLAINS FROM COLORADO AT 4
PM THIS AFTERNOON. SUBSTANTIAL CYCLOGENESIS IS OCCURRING ACROSS THE
MID-MISSISSIPPI VALLEY. INVERTED TROUGH EXTENDS NORTHEAST FROM
THIS ACROSS KANSAS CITY TO DES MOINES TO EAU CLAIRE. DEW POINTS IN
THE MID 20S TO THE EAST OF THIS BEING UPLIFTED INTO THE AREA AS
LEAD IMPULSE LIFT NORTHEAST FROM ERN NE. WITHIN BROAD WARM AIR
ADVECTION AND ISENTROPIC UPGLIDE...THIS WAVE WILL ENHANCE EAST TO
WEST BANDS ACROSS SOUTHERN MN WITHIN THE NEXT SEVERAL HOURS. THIS
WILL EXPAND NORTH INTO THE TWIN CITIES DURING THE EVENING.
GENERALLY THESE BANDS ARE TRANSIENT...WITH LITTLE RESIDUAL TIME IN
ONE SPOT. ALSO...THE DENDRITIC SNOWFLAKE GROWTH ZONE IS NOT WITHIN
THE DEEPEST VERTICAL OMEGA AT THIS TIME. BOTH OF THESE FACTORS
CHANGE BY LATE EVENING AND OVERNIGHT INTO WED MORNING AS THE SFC
LOW DEEPENS AROUND 17 MB /SEVEN MODEL AVERAGE/ FROM 00Z WED TO 12Z
WED. THE SFC LOW SHOULD BE SRN LAKE MICHIGAN BY 12Z WED. THIS
PANHANDLE HOOKER PATH FAVORS SRN MN INTO WI. AREAL EXPANSIVENESS
OF ISENTROPIC UPGLIDE...HELPED BY A BROAD COUPLED JET STRUCTURE
SEEN ON 12Z RAOBS AND RUC ANALYSIS...WILL FAVOR SIX INCH PLUS
AMOUNTS EVEN FURTHER NORTH IN ADDITION TO THE IDEAL CORRIDOR. THE
CIPS ANALOG GUIDANCE FROM SIMILAR SYNOPTIC SCENARIOS TO THE GFS
GUIDANCE HAS FAVORED MINNEAPOLIS TO SEE SIX PLUS INCHES FROM THE
00Z AND 12Z GFS. SO THIS LENDS CREDENCE TO GREATER AMOUNTS
FURTHER NORTH...AS DO EMPIRICAL TECHNIQUES SUCH AS THE COOKE AND
GARCIA METHODS. THE GREATEST AMOUNTS AND SNOWFALL RATES IN SREF
PROBABILISTIC AND MEMBER GROUPING GUIDANCE FAVOR 9 PM TONIGHT TO 9
AM WED MORNING. THE DENDRITIC GROWTH IS ALSO MAXIMIZED IN THAT
TIME WITH F-GEN PIVOTING WITHIN THAT LAYER ACROSS MAINLY WRN WI
AND FAR ERN MN. MUCH MORE RESIDUAL TIME WILL OCCUR UNDER THE
BANDED SNOW OVERNIGHT AND WED MORNING AS THE LOW PATH IS PARALLEL
TO THE ERN CWA. RATIOS ALSO ARE FAVORED SLIGHTLY HIGHER WHICH
CONTINUES THE TREND OF THE PREVIOUS SHIFT. THIS WILL LEAD TO
SNOWFALL AMOUNTS NEAR OR IN THE DOUBLE DIGITS FROM ALBERT LEA TO
THE SE METRO TO RICE LAKE AND SOUTHEASTWARD. ONE FOOT AMOUNTS NEAR
EAU CLAIRE SEEM LIKELY.
THE PRIMARY LOW LEVEL HEIGHT FALL/RISE COUPLET PASSES TO OUR SOUTH
WITH THIS SYSTEM...BUT MODEL GUIDANCE CONTINUES IN GOOD AGREEMENT
OF STRONG WINDS THROUGHOUT THE ENTIRE GRADIENT AREA OF THIS
CYCLONE. FACTORS WHICH ARE FAVORABLE FOR STRONG GUSTY WINDS OF 30
KTS IN SOUTH CTRL MN TO 25 KTS IN WEST CTRL WI ARE THE INCOMING
COLD AIR ADVECTION STEEPENING LOW LEVEL LAPSE RATES...A
UNIDIRECTIONAL COLUMN IN THAT AREA...AND AN ASTOUNDING
ISALLOBARIC EFFECT WITH DEEP SFC PRESSURES AS A BASELINE. HAVE
EXPANDED BLIZZARD WARNING NORTH AND EASTWARD. BLOWING AND DRIFTING
SHOULD CONTINUE MANY HOURS AFTER THE SNOWFALL CEASES DUE TO THE
HIGH SNOW TO LIQUID RATIO NATURE OF THE SNOW ON THE GROUND.
HAVE ADDED WIND CHILL MENTION INTO WSW AND HWO DUE TO THE
PLUMMETING TEMPS ON WEDS. -25 WIND CHILLS WILL BE NEARED ON WED IN
WRN MN AND LIKELY ACROSS CTRL MN WED NIGHT WHEN A WIND CHILL
ADVISORY MAY BE NEEDED.
A COLD PATTERN IS FAVORED IN THE LONG RANGE AS REGION IS MIRED IN
DEEP NORTHWEST FLOW EARLY IN PERIOD AS COLD ARCTIC VORTEX
PROGRESSES SOUTHWARD OUT OF NORTHWEST CANADA THEN ACROSS S MB AND
ONTARIO OVER THE WEEKEND. 850 TEMPS REMAIN B15 TO B20 RANGE THRU
MUCH OF PERIOD WITH BRIEF SLIGHT MODERATION AS WEAK SHORTWAVES
RIDE SE THRU THE AREA....ONE ON SATURDAY AND ANOTHER ABOUT SUNDAY
NIGHT/MONDAY. WILL ADD SOME -SN AS THESE FEATURES MOVE THRU. WITH
SNOW COVER EXPECTED ACROSS THE AREA DURING THIS PERIOD...MINIMUM
TEMPERATURES ESPECIALLY WILL LIKELY BE QUITE COLD. ADJUSTED TEMPS
DOWNWARD TO ACCOUNT FOR THIS.
&&
.AVIATION.../06Z TAF ISSUANCE/
MAJOR WINTER STORM CURRENTLY UNFOLDING WILL HAVE SIGNIFICANT
IMPACTS ON ALL TAF SITES FOR AT LEAST FIRST 12 HRS OF TAF. AT
6Z...DEEPENING SFC LOW ANALYZED OVER WRN IL IS PROGGED TO BE NE OF
LAKE HURON BY 06Z WEDNESDAY. CURRENT SATELLITE/RADAR IMAGERY
SHOWING BANDED SNOW OVER SE MN INTO WC WI THAT WILL BE IMPACTING
MSP/RNH/EAU THROUGH AT LEAST 15Z WITH PERIODS OF HEAVIER
SNOWFALL. OTHER IMPACT OF DEEPENING LOW IS RAPIDLY INCREASING
WINDS. THESE WINDS WILL BE SLOWLY TURNING TO THE NW WITH
TIME...WITH NAM/BUFKIT PROFILES SUGGESTING GUST POTENTIAL
APPROACHING 40 KTS AT ALL TERMINALS THROUGH THE MORNING...WITH
GUSTS OVER 30KTS WELL INTO THE AFTERNOON...WHICH WILL KEEP VSBYS
REDUCED THROUGH THE AFTERNOON.
AXN/RWF/STC...THESE TERMINALS WILL SEE THE LEAST AMOUNT OF
SNOWFALL AS BEST FGEN FORCING WILL BE CENTERED OFF TO THE EAST. IN
ADDITION...EXPECT MAINLY MVFR CIGS TO PERSIST OUT HERE...AS SEEN
IN THE GFSLAMP...AS BETTER MOISTURE AND LOWER CLOUDS WILL STAY
CLOSER TO THE LOW...THOUGH A FEW MOMENTS DOWN IN IFR CATEGORY CAN
NOT BE RULED OUT THROUGH 15Z. THOUGH SNOWFALL WILL NOT BE AS
MUCH...STILL PLENTY OF WINDS TO CREATE BLSN ISSUES OUT TO ABOUT
21Z BEFORE WINDS BEGIN TO DIE DOWN.
MSP...LOOKS LIKE WILL BE ON WRN EDGE OF HEAVIEST BANDED SNOW
THROUGH THE EVENING...AND WITH WINDS...EXPECT VSBY TO DROP INTO
THE 1/2SM RANGE FOR A GOOD PORTION OF THE MORNING RUSH...ALSO CAN
NOT RULE OUT SOME VSBYS SNEAKING DOWN UNDER 1/4SM. GFSLAMP HOLDS
VSBYS DOWN TO IFR THROUGH THE AFTERNOON...AND WITH WINDS EXPECTED
TO BE AS HIGH AS THEY ARE THIS SEEMS VERY PLAUSIBLE. GFS ALSO
HOLDS CLOUDS IN STRONG THOUGH 06Z THURSDAY...BUT BOTH NAM AND GFS
WANT TO GO FULL VFR AT MSP BY THE END OF THE PERIOD.
RNH/EAU...THESE TERMINALS WILL FEEL BRUNT OF HEAVIEST SNOWFALL
THROUGH THE MORNING. EAU ALREADY HAS HAD SUSTAINED 3/4SM VSBYS FOR
THE LAST COUPLE OF HOURS...AND SEE NO REASON WHY THIS WILL NOT
CONTINUE TO BE THE CASE THROUGH AT LEAST 15Z. LOOKS LIKE AT LEAST
-SN WILL HOLD ON AT WIS TERMINALS TO ABOUT 00Z. STRONGEST WINDS
WILL ALSO LINGER LONGEST HEAR AND THEY WILL LIKELY HAVE BLSN ISSUE
THROUGH THE ENTIRE 24 HOURS. FOR CIGS...IFR OR LOWER WILL PERSIST
DURING HEAVIEST SNOW THIS MORNING...BUT PROXIMITY TO LOW WILL HOLD
IFR CIGS UNTIL CLOSER TO 00Z...WITH MVFR CIGS HOLDING THROUGH 06Z
THURSDAY.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...BLIZZARD WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR BLUE
EARTH-BROWN-CARVER-DAKOTA-FARIBAULT-FREEBORN-GOODHUE-LE
SUEUR-MARTIN-MCLEOD-NICOLLET-RICE-SCOTT-SIBLEY-STEELE-
WASECA-WATONWAN.
WINTER WEATHER ADVISORY UNTIL 6 PM CST WEDNESDAY FOR BENTON-
DOUGLAS-KANABEC-KANDIYOHI-MEEKER-MILLE LACS-MORRISON-POPE-
STEARNS-STEVENS-SWIFT-TODD.
WINTER STORM WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
ANOKA-CHISAGO-HENNEPIN-ISANTI-RAMSEY-SHERBURNE-WASHINGTON-
WRIGHT.
BLIZZARD WARNING UNTIL 6 PM CST WEDNESDAY FOR CHIPPEWA-LAC QUI
PARLE-REDWOOD-RENVILLE-YELLOW MEDICINE.
WI...BLIZZARD WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR CHIPPEWA-
DUNN-EAU CLAIRE-PEPIN-PIERCE.
WINTER STORM WARNING UNTIL MIDNIGHT CST WEDNESDAY NIGHT FOR
BARRON-POLK-RUSK-ST. CROIX.
&&
$$
MTF/MPG
