Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 242156
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
356 PM CST WED DEC 24 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 354 PM CST WED DEC 24 2014

REGIONAL SATELLITE IMAGERY HAD SHOWN THE LOWER CLDS/CIGS ACROSS
SD/NE SLOWLY ERODING FROM SW TO NE AS WINDS SHIFT TO THE SW.
HOWEVER...THE NEXT STORM SYSTEM HAS ALREADY SPREAD MID/HIGH LEVEL
CLOUDINESS ACROSS THE DAKOTAS AND INTO MN DURING THE AFTN. ALTHOUGH
WE COULD SEE SOME BREAKS IN THE LOWER CLDS/CIGS LATE TONIGHT FROM SW
TO NE...OVERALL IT WILL REMAIN CLOUDY FOR THIS SHORT TERM PERIOD. IF
WE DO GET A CHC OF PARTLY CLOUDY SKIES...IT WILL OCCUR IN FAR
SOUTHERN MN AS GREATER MIXING IN THE BOUNDARY LAYER DEVELOPS.

AS FOR CHC/S OF SNOWFALL...THERE REMAINS A GOOD PROBABILITY OF A
SMALL BAND OF 1-3" TO FALL ACROSS WC INTO PORTIONS OF CENTRAL MN
DURING THE DAYTIME HRS. THE BEST CHC BASED ON STRONGER FRONTAL
ENERGY WILL OCCUR IN WC MN. IN ADDITION...SNOWFALL RATIOS WILL BE
INITIALLY LOW IN THE 8-1 RANGE...PLUS A WARM GROUND FROM RECENT ABV
NORMAL TEMPS...SHOULD LIMIT SNOWFALL TOTALS. IF THE FORCING
INCREASES FROM THE CURRENT MODEL RUNS...THERE COULD BE LOCALLY
HIGHER AMTS. TEMPS FROM WC TO CENTRAL MN WILL BE THE COLDEST AS
PRECIPITATION AND DENSER CLOUD COVER WILL PREVAIL. IN SC
MN...TEMPS MAY APPROACH 40 DEGREES IF SOME SUN DEVELOPS.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 354 PM CST WED DEC 24 2014

BIGGEST CONCERN IN THE LONG TERM IS SNOWFALL POTENTIAL INHERITED
FROM THE SHORT TERM THURSDAY AFTERNOON THAT WILL CONTINUE THROUGH
FRIDAY NIGHT. AFTER THAT...THE ECMWF IN PARTICULAR IS HINTING AT
ANOTHER QUICK HIT OF SNOW MONDAY BEFORE THE ARCTIC AIR ARRIVES TO
END 2014.

FOR THURSDAY NIGHT THROUGH FRIDAY NIGHT...AN UPPER TROUGH WORKING
ACROSS THE ROCKIES ON THURSDAY WILL EJECT NORTHEAST ACROSS THE
PLAINS AS A POSITIVELY TILTED TROUGH FRIDAY THAT WILL BE GETTING
SHEARED OUT AS IT GETS ABSORBED INTO NRN STREAM ENERGY ACROSS CANADA
FRIDAY NIGHT. AT THE SFC...THE UPPER LOW WILL LEAD TO LEE
CYCLOGENSIS ON THU OVER COLORADO...WITH A COLD FRONT WORKING INTO
WRN MN. THIS FRONT WILL STALL OUT ACROSS MN INTO FAR NW WI THU NIGHT
AS A WAVE WORKS NORTH ALONG THE FRONT INTO IOWA ON FRIDAY. AT THE
VERY LEAST THIS WEATHER PATTERN WILL ENSURE THAT WE MAINTAIN THE
OVERCAST SKIES THROUGH FRIDAY NIGHT...BUT COULD ALSO RESULT IN
ANOTHER PROLONGED PERIOD OF PRECIP STARTING THURSDAY AFTERNOON AND
LASTING THROUGH FRIDAY NIGHT. THE PRECIP WOULD START THURSDAY AS THE
WAA BAND PUSHES INTO WRN AND CENTRAL MN. THIS BAND LOOKS TO SLOWLY
DIMINISH OVERNIGHT AS RIDGING BUILDS IN ALOFT...HELPING TO BREAK
DOWN  MOISTURE AND LIFT ALONG THE 295K SFC. AFTER THAT...FOR MUCH OF
FRIDAY WE GET INTO ANOTHER POTENTIAL DRIZZLE SETUP AS UPPER FORCING
MOVES AWAY...BUT LOW LEVEL FORCING INCREASES WITH THE TROUGH MOVING
ACROSS THE AREA. TEMPERATURES WILL BE A COUPLE OF DEGREE COOLER FOR
FRIDAY AS WELL...WHICH MEANS ANY DZ WOULD BE IN THE FORM OF FZDZ.
NOT OVERLY CONFIDENT THOUGH ON DRIZZLE POTENTIAL FRIDAY...SO SIMPLY
LIMITED SNOW CHANCE MENTION TO 30% OR LESS...BUT THIS WILL OBVIOUSLY
NEED TO BE REEVALUATED. AFTER THAT...12Z MODELS HAVE COME INTO GOOD
AGREEMENT ON ANOTHER BAND OF SNOW WORKING UP FROM SOUTH CENTRAL MN
INTO CENTRAL WI IN RESPONSE TO WHATS LEFT OF THE MAIN UPPER TROUGH
WORKING ACROSS THE REGION AS IT GETS ABSORBED BY THE MAIN NRN STREAM
ENERGY ACROSS SRN CANADA. AGAIN MOISTURE LOOKS LIMITED...BUT ALL
GUIDANCE SHOW THIS BEING ANOTHER BAND OF 1-3 INCHES OF SNOW WHEREVER
IT FALLS. THE FRIDAY NIGHT BAND LOOKS TO FALL A HUNDRED OR SO MILES
SOUTH OF THE THU/THU NIGHT BAND...SO THERE WILL LIKELY BE A STRIP IN
BETWEEN THAT SEES VERY LITTLE. RIGHT NOW...THIS STRIP OF
LITTLE/NOTHING LOOKS TO ENCOMPASS MUCH OF THE TWIN CITIES METRO AREA.

AFTER THAT...MODELS CONTINUE TO BE ALL OVER THE PLACE WHEN IT COMES
TO SNOW POTENTIAL AS THE ARCTIC BOUNDARY COMES INTO THE AREA. THE
PROBLEM COMES WITH HOW FAR EAST ENERGY WILL MAKE FROM A DEEP TROUGH
THAT WILL BE DIGGING ACROSS THE ROCKIES SUN/MON. THE GEM/GFS TAKE A
CLIPPER TYPE SNOW FROM THE WRN DAKOTAS TO NW MO SUN/MON...WHILE THE
ECMWF TAKES THIS SNOW FROM THE WRN DAKOTAS TO ACROSS SRN MN. GIVEN
THE AMOUNT OF MOVEMENT WE HAVE SEEN IN THE MODELS WITH THIS
SNOW...LIMITED POPS TO SUNDAY NIGHT AND ACROSS SRN MN. AFTER
MONDAY...ITS INTO THE FREEZER WITH THE ACTIVE WEATHER LOOKING TO
LARGELY AVOID THE UPPER MS VALLEY FOR A WHILE AS SRN STREAM ENERGY
STAYS DOWN ALONG THE GULF COAST WHILE NRN STREAM ENERGY REMAINS
MOSTLY IN CANADA.

FOR TEMPERATURES...THERE WILL BE TWO TEMPERATURE DROPS THIS PERIOD.
THE FIRST WILL COME BEHIND THE FRIDAY FRONT...THIS WILL SEND HIGHS
BACK DOWN TO ABOUT NORMAL FOR THE WEEKEND. THE ARCTIC BOUNDARY
ARRIVES MONDAY...BUT THERE CONTINUES TO BE DISAGREEMENTS ON WHEN
THAT ARRIVES...WITH THE GFS BRINGING IN THE ARCTIC AIR SUNDAY
NIGHT...WITH THE ECMWF WAITING UNTIL LATER MONDAY. CONTINUED TO
FAVOR THE WARMER ECMWF SOLUTION GIVEN THE FACT THAT EACH SUCCESSIVE
RUN OF THE GFS DELAYS TO THE ARCTIC AIRS ARRIVAL SOME...AND WITH
LITTLE IN THE WAY IN SNOW COVER SOUTH OF CANADA...THE COLDER AIR
WILL LIKELY BE BIT DELAYED IN GETTING HERE. AS FOR THAT COLD
AIR...THE CORE IF IT ACTUALLY LOOKS TO GO WEST OF MN OUT ACROSS THE
HIGH PLAINS AS A 1050 MB HIGH BUILDS SOUTH ALONG THE FOOTHILLS OF
THE ROCKIES. STILL...WITH 925-850 TEMPS FORECAST TO BE BETWEEN -16C
AND -20C BY NEW YEARS EVE...IT STILL LOOKS GOOD FOR A RATHER CHILLY
FINAL DAY OF 2014 WITH HIGHS LIKELY STAYING IN THE SINGLE
DIGITS...EVEN IF WE DO NOT HAVE MUCH SNOW COVER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1105 AM CST WED DEC 24 2014

WIDESPREAD LOW END MVFR/IFR/LIFR CIGS/VSBYS CONTD ACROSS MOST OF MPX
CWA...WITH THE EXCEPTION NEAR KEAU WHERE CIGS ROSE ABV 3K THIS
MORNING.

BASED ON CONTINUED VERY MOIST BOUNDARY LAYER...INVERSION STRENGTHENING
AND LIMITED MIXING IN THE BOUNDARY LAYER AS WINDS BACK TO THE SW/S
OVERNIGHT...WILL LEAN TOWARD IFR/MVFR CIGS THRU THE PERIOD.

ALTHOUGH EARLIER TAFS HAD A PERIOD OF VFR CONDS OVERNIGHT...THERE
REMAINS SOME OPTIMISM ON VFR BRIEFLY MOVING INTO WESTERN MN DURING
THE OVERNIGHT HRS BEFORE ANOTHER SYSTEM LOWERS CIGS/VSBYS IN
-SN...MAINLY NORTH OF HWY 212 OR FROM KDXX TO KSTC. WINDS WILL
SLOWLY BECOME W/SW THIS EVENING AS A RIDGE BUILDS ACROSS THE AREA.
MORE SW/S WINDS DEVELOP TOMORROW AS A STORM SYSTEM APPROACHES FROM
THE WEST BY THE AFTN.

KMSP...

KEPT CIGS BLW 1.7K THRU THE AFTN/EVENING AS UPSTREAM OBS/CONDS
LOOK FAVORABLE FOR THIS TO OCCUR. STILL SOME OPTIMISM ON VFR CONDS
LATE TONIGHT AS WINDS SHIFT TO THE SW. HOWEVER...DUE TO THE
STRENGTHENING INVERSION AND VERY MOIST BOUNDARY LAYER...I HAVE LOW
CONFIDENCE ON THIS SCENARIO. EVEN IF WE GET THE VFR CONDS...MVFR
CIGS WILL LIKELY REDEVELOP THURSDAY AFTN AS THE NEXT STORM SYSTEM
MOVES IN FROM THE WEST. SFC WINDS WILL START FROM THE NW AND BACK
TO THE W/SW THIS EVENING AND MORE S/SSE BY THURSDAY AFTN. SPDS
WILL REMAIN AOB 10 KTS.

/OUTLOOK FOR KMSP/

FRI...MVFR/IFR WITH CHC -SN. WINDS NNW 10 KTS.
SAT...VFR. WINDS WNW 5-10 KTS.
SUN...VFR... WINDS SSE 5 KTS.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

SHORT TERM...JLT
LONG TERM...MPG
AVIATION...JLT





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