000
FXUS63 KMPX 040030
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
630 PM CST TUE DEC 3 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 251 PM CST TUE DEC 3 2013

THIS EVENING THROUGH WEDNESDAY EVENING...WIDESPREAD ACCUMULATING
SNOW STILL ON TRACK...WITH NOT TOO MANY CHANGES FROM THE MORNING
FORECAST PACKAGE. EARLY THIS MORNING... THE GFS AND NAM FINALLY
TRENDED TOWARD THE ECMWF/UKMET/GEM SOLUTION. DID GAIN CONFIDENCE
IN WARNING CRITERIA SNOWFALL FROM JUST WEST OF THE METRO TO
ALEXANDRIA... WITH THE HEAVIEST BAND LIKELY TO SETUP IN A SW-NE
ORIENTED FASHION FROM ST CLOUD UP TOWARDS DULUTH. FROM THE METRO
TO THE EAST...THE SITUATION BECOMES MUCH MORE COMPLICATED DUE TO
THE MIXED PRECIPITATION POTENTIAL. THE SURFACE LOW DEVELOPING ON
THE LEE OF THE ROCKIES WILL MOVE OUT OVER THE PANHANDLE OF OK
BEFORE CURLING NORTHEAST THROUGH EASTERN IOWA AND WISCONSIN. WITH
THIS TRACK...WARM AIR ADVECTION IN THE LOW LEVELS WILL TURN THE
PRECIP TYPE TO A MIXED BAG AND RAIN IN THE EAST METRO AND AREAS TO
THE SOUTHEAST DURING THE LATE MORNING HOURS ON WEDNESDAY. THE EC
THERMAL PROFILE IS COOLER THAN THE EXTREMELY WARM 12Z RUN OF THE
NAM...AND WARMER THAN THE COOL GFS. THE NAM CONTINUES TO WOBBLE
THE MOST WITH THE THERMAL PROFILE. THE 18Z NAM COMING IN AS I
WRITE THIS DISCUSSION...SHOWED THE 0C LINE AT 850MB PULLING BACK
TO THE SOUTHEAST...CLOSER TO THE EC SOLUTION. THIS SITUATION IS
ANOTHER CLASSIC SETUP OF A VERY TIGHT SNOWFALL GRADIENT OVER THE
METRO...WITH NORTHWEST SUBURBS EXPECTING 6-8" AND SOUTHEAST
SUBURBS CLOSER TO 3-5" WITH SOME SLEET MIXED IN. THE DEFORMATION
ZONE WILL REMAIN JUST TO THE WEST OF THE METRO AND WILL HELP
PRODUCE THE HEAVIEST AMOUNTS FROM ST CLOUD TO THE NORTHEAST NEAR
MILLE LACS LAKE WHERE 8-10" IS POSSIBLE. CONFIDENCE IN KNOWING
WHERE THAT RAIN/SNOW LINE WILL SETUP IS BELOW AVERAGE FOR BEING
THIS CLOSE TO THE EVENT. IF THE GFS TURNS OUT TO BE CORRECT... THE
ENTIRE METRO WILL BE IN FOR ALL SNOW 6"+ WOULD BE MORE WIDESPREAD.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 251 PM CST TUE DEC 3 2013

AT THE START OF THE PERIOD THE BROAD SURFACE TROUGH WILL HAVE
BECOME BETTER ORGANIZED INTO AN SURFACE LOW HOVERING AROUND
995-998MB. THIS SURFACE LOW WILL CONTINUE TO DEEPEN AS IT LIFTS
NORTHEAST TOWARDS JAMES BAY...WHILE COLD AIR OVERSPREAD THE UPPER
MIDWEST. THIS COLD AIR WILL REMAIN IN PLACE THROUGH EARLY NEXT
WEEK...WITH ANOTHER CHANCE OF SNOW OVER THE WEEKEND.

BY 00Z THURSDAY COLD AIR ADVECTION WILL BE IN PLACE ACROSS THE
ENTIRE REGION...WITH FORECAST SOUNDINGS ACROSS WESTERN MINNESOTA
SHOWING 25KTS IN THE MIXED LAYER...WITH LOW 30KT POTENTIAL AT THE
TOP OF THE CHANNEL. THE COLD AIR ADVECTION WILL KEEP THE BOUNDARY
LAYER WELL MIXED...SO FULLY ANTICIPATE REALIZING THIS WIND
POTENTIAL OVERNIGHT...ESPECIALLY IN THE OPEN AREAS OF WESTERN
MINNESOTA. THIS LOW 30KT GUST POTENTIAL IS BELOW THE 40KT
THRESHOLD THAT IN THE PAST HAS PRODUCE BLIZZARD CONDITIONS ALONG
THE MINNESOTA RIVER VALLEY...BUT STILL EXPECT AREAS OF BLOWING
SNOW ALONG WITH TEMPERATURES FALLING INTO THE SINGLE DIGITS BY
MORNING WHICH WILL MAKE TRAVEL DIFFICULT AS ANY TREATED ROADWAYS
QUICKLY TURN TO ICE. FORECAST SOUNDINGS ALSO SHOW SATURATION IN
THE DENDRITIC GROWTH ZONE...SO SHOULD HAVE LIGHT SNOW LINGERING
THROUGH THURSDAY MORNING AS WELL. ACCUMULATIONS WILL BE
NEGLIGIBLE...BUT ANY LIGHT SNOW WILL AID IN REDUCING
VISIBILITIES...SO WILL LIKELY SEE THE WINTER STORM WARNING LAST
THROUGH 12Z THURSDAY DESPITE THE MAJORITY OF THE ACCUMULATING SNOW
ENDING PRIOR TO 18Z.

BLUSTERY CONDITIONS WILL PERSIST THROUGH THE DAY ON THURSDAY...
WITH COLD AIR ADVECTION CONTINUING AND KEEPING THE BOUNDARY
LAYER MIXED. BY FRIDAY MORNING H850 TEMPS OF -20C WILL BE IN PLACE
ACROSS THE REGION...RESULTING IN SURFACE LOWS OF -10F TO -15F AND
WIND CHILL VALUES NEAR -30F IN FAR WESTERN MN...AND TEMPERATURES
NEAR ZERO WITH WIND CHILL VALUES AROUND -20F ACROSS WESTERN
WISCONSIN. LOW TEMPERATURES WILL BE EVEN COLDER ON SATURDAY
MORNING. THIS TREND CHARACTERIZED BY SEASONABLY COLD AIR WITH A
FEW EMBEDDED SHORTWAVES IN THE SOUTHWEST/ZONAL JET BRINGING SOME
OCCASIONAL FLURRIES WILL CONTINUE THROUGH THE END OF THE PERIOD. A
MORE PRONOUNCED PRECIP OPPORTUNITY COMES SUNDAY INTO MONDAY AS
BOTH THE GFS AND ECMWF 03.12 BRING A SHORTWAVE UP FROM THE DESERT
SOUTHWEST AND A CHANCE FOR ACCUMULATING SNOW.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 601 PM CST TUE DEC 3 2013

ASIDE FROM A FEW POCKETS OF MVFR CONDS AT INITIALIZATION TIME OF
THE 04/00Z TAFS...SOLID IFR-OR-WORSE CONDS EXPECTED THROUGHOUT
THIS SET AS A POTENT LOW PRES CENTER SLOWLY TRUDGES ITS WAY ACRS
THE REGION THRU TMRW. P-TYPE ISSUES WILL BE MITIGATED TO SNOW AS
MODEL GUIDANCE HAS REDUCED ANY SEMBLANCE OF A WARM LAYER ALOFT TO
NOTHING /EXCEPT FOR KEAU WHICH WILL BE CAUGHT IN SOME WARMER AIR
SO THERE MAY BE A VARIETY OF P-TYPES IN THE FIRST HALF OF THE TAF
PERIOD/. USING SHORT-TERM MODEL GUIDANCE...PRECIP ONSET WILL OCCUR
IN THE PRE- DAWN HOURS...THEN THE HEAVIEST BANDS OF PRECIP WILL
OCCUR IN THE LATE MRNG TO EARLY AFTN HOURS...ESP FOR CENTRAL MN
EASTWARD. MOST DEGRADED CONDS WILL OCCUR DURING THAT MIDDAY PERIOD
TMRW THEN CONDS WILL GRADUALLY IMPROVE LATE TMRW INTO TMRW EVE.
THE IMPROVEMENT WILL ROUGHLY COINCIDE WITH A SWING IN WIND
DIRECTIONS AS WINDS SHIFT FROM NE TO N AND NW...AND THE PRES
GRADIENT INCRS OVER WRN MN WHICH WILL INCRS WIND SPEEDS.

KMSP...OBSERVATIONS AT INITIALIZATION ARE BARELY WITHIN MVFR RANGE
BUT HAVE OPTED TO GO FULL-BORE INTO IFR SINCE EXPECTATIONS ARE FOR
IFR-OR-WORSE CONDS TO PREVAIL AT THE TERMINAL FROM THIS EVENING
THRU MUCH IF NOT ALL OF TMRW. THE MAIN ISSUES ARE THE TIMING OF
THE ONSET OF SNOW AND THE TIMING OF ANY HEAVY BANDS OF SNOW.
ATTM...ONSET OF SOLID -SN LOOKS TO BE IN THE 09Z-11Z AREA WITH
HEAVIER BANDS STARTING TO AFFECT THE TERMINAL IN THE 13Z-15Z
TIMEFRAME. THE HEAVIER BANDS LOOK TO LAST UNTIL 18Z-20Z THEN CONDS
SLOWLY IMPROVE AS THE PRECIP BACKS OFF. THERE IS ALSO THE TIMING
OF THE DIMINISHING SNOWFALL WITH THE INCRS IN WINDS...SO VSBY MAY
BE STRONGLY AFFECTED BY BLOWING SNOW. WINDS REMAIN NE THRU TNGT
THEN GRADUALLY BACK TO N AND NW...INCRG IN SPEED TMRW AFTN TO THE
15G22KT AREA.

/OUTLOOK FOR KMSP/
THU...MVFR CIGS PSBL. NW WIND 10-20 KT.
THU NIGHT...VFR. W WIND 5-15 KT.
FRI...MVFR CIGS PSBL. W WIND 5-15 KT.
FRI NIGHT...VFR. W WIND LESS THAN 10 KT.
SAT...VFR. VARIABLE WIND 5 KT OR LESS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER WEATHER ADVISORY UNTIL 6 AM CST THURSDAY FOR MNZ069-070-
     076>078-082>085.

     WINTER STORM WARNING UNTIL 6 AM CST THURSDAY FOR MNZ041>045-
     047>068-073>075.

     DENSE FOG ADVISORY UNTIL NOON CST WEDNESDAY FOR MNZ092-093.

WI...WINTER WEATHER ADVISORY UNTIL 6 AM CST THURSDAY FOR WIZ024>028.

     WINTER STORM WARNING UNTIL 6 AM CST THURSDAY FOR WIZ014>016-023.

&&

$$

SHORT TERM...SPD
LONG TERM...JRB
AVIATION...JPC