Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 250058
AFDMPX

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

.UPDATE...
ISSUED AT 651 PM CST WED DEC 24 2014

UPDATED TO INCLUDE 00Z AVIATION DISCUSSION BELOW.

&&

.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 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 651 PM CST WED DEC 24 2014

IR SATELLITE IMAGERY SHOWS THE VAST MAJORITY OF THE MPX COVERAGE
AREA COVERED WITH LOW-END MVFR TO UPPER-END IFR CEILINGS...AND
THIS TREND LOOKS TO HOLD FORT FOR MUCH OF THE OVERNIGHT HOURS.
LITTLE REASON TO EXPECTED OTHERWISE WITH THE NIGHTLY INVERSION
TRAPPING LLVL MOISTURE IN PLACE AND A PREVAILING SOUTHERLY FLOW.
WITH HIGH PRESSIRE BARELY HOLDING ON GOING INTO THE MORNING...
THERE IS SOME OPTIMISM FOR POTENTIALLY SOME LOW-END VFR CEILINGS
TO HAVE A BRIEF OPPORTUNITY TO DEVELOP. HOWEVER...AN APPROACHING
WINTER STORM SYSTEM WILL KEEP ANY VFR DURATION QUITE LOW...
BRINGING BACK MVFR-TO-IFR CEILINGS LATE DAY INTO TMRW EVE. WRN MN
SITES HAVE THE POTENTIAL FOR -SN TO DEVELOP LATE DAY INTO TMRW
EVE. AS THE LOW PRES SYSTEM APPROACHES...A PERIOD OF LGT/VRBL
WINDS WILL DEVELOP BEFORE WINDS SWING AROUND TO NE LATE TMRW.

KMSP...INITIALIZED AT LOW-END END MVFR BUT WITH A GOOD NUMBER OF
SITES UPSTREAM REPORTING IFR CEILINGS...HAVE ALSO ADDED IN AN
EARLY TEMPO FOR IFR CEILINGS. CELINGS TO REMAIN PREVAILING MVFR
THRU THE OVERNIGHT...BUT WITH SOME HINT THAT CEILINGS RISE ABOVE
THE 1700FT THRESHOLD. HAVE ALSO ADVERTISED THE LATE MRNG WINDOW OF
VFR BUT THERE IS SOME WAVERING CONFIDENCE ON THIS THINKING. MVFR
CEILINGS RETURN LATE DAY AND REMAIN IN PLACE...BUT PRECIP CHCS ARE
TOO LOW FOR INCLUSION AT THIS POINT.

/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.
&&

$$

UPDATE...JPC
SHORT TERM...JLT
LONG TERM...MPG
AVIATION...JPC





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