Area Forecast Discussion
Issued by NWS Twin Cities, MN

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355
FXUS63 KMPX 122145
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
345 PM CST FRI FEB 12 2016

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 345 PM CST FRI FEB 12 2016

THE SHORT TERM PERIOD WILL SEE QUIET WEATHER AS A STRONG HIGH
PRESSURE AREA BUILDS IN FROM THE NORTH THROUGH THE NIGHT...SETTING
THE STAGE FOR ONE OF THE COLDER NIGHTS OF THE WINTER ACROSS MUCH OF
THE REGION. THE CORE OF THE ARCTIC AIR MASS IS CURRENTLY OVER
NORTHEASTERN ONTARIO AND WILL SHIFT SOUTHEAST THROUGH THE EASTERN
GREAT LAKES TOWARD THE NORTHEASTERN CONUS.  SO...WE WILL MISS OUT ON
THE CORE OF THE AIR MASS...BUT WILL STILL BE WELL BELOW NORMAL
TONIGHT AND TOMORROW THANKS TO THE HIGH PRESSURE PROVIDING US WITH
MOSTLY CLEAR SKIES AND CALM WINDS TONIGHT. HIGH CLOUDS WILL WORK
INTO WESTERN MN OVERNIGHT...SO TEMPS MAY BOTTOM OUT CLOSER TO 06-09Z
BEFORE LEVELING OFF.

FOR SATURDAY...WINDS WONT TURN SOUTHERLY UNTIL LATER IN THE DAY
ACROSS EASTERN MN AND WESTERN WI ESPECIALLY...AHEAD OF THE INCOMING
SYSTEM WHICH IS DISCUSSED IN DETAIL IN THE LONG TERM PORTION OF
THIS DISCUSSION.  HIGHS TOMORROW WILL BE IN THE SINGLE DIGITS TO
LOWER TEENS...AND MID AND UPPER LEVEL CLOUDS WILL BUILD IN FROM WEST
TO EAST...ESPECIALLY IN THE AFTERNOON.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 345 PM CST FRI FEB 12 2016

SNOW WILL SPREAD INTO WESTERN MN AT THE START OF THE LONG TERM AS
A STRONG SHORT WAVE OVER THE WESTERN HIGH PLAINS AND WAA HEAD OUR
WAY. THE ECMWF AND GFS DETERMINISTIC MODELS HANDLE THIS SYSTEM
WELL WITH REGARDS TO THE ONSET...DURATION AND PRECIPITATION
AMOUNTS. HOWEVER...WE DID NOTICE A WESTWARD ADJUSTMENT TO THE MAX
QPF AXIS TODAY WHICH IS NOW MORE ACROSS THE MN RIVER VALLEY. IN
FACT...TIME LAGGED GFS BUFKIT DATA FOR KMSP SHOWS A DOWNWARD TREND
IN TOTAL SNOWFALL OVER THE PAST SIX RUNS.

THIS WESTWARD ADJUSTMENT WITH THE QPF IS NOT TOTALLY REFLECTED IN
OUR FORECAST TODAY SINCE THIS MAY BE MORE LIKE A PENDULUM OF A
CLOCK AND SWING BACK TO THE EAST OVER THE NEXT 24 HOURS. THERE IS
ALSO CONCERN WITH THE ECMWF SHOWING MORE OF A NEGATIVELY TILTED
TROUGH AT H5 DEVELOPING ACROSS THE FA ON SUNDAY...WHICH MAY SKEW
THINGS A LITTLE TO THE EAST. COMPOUNDING THE PROBLEM IS THE SNOW
RATIOS EXPECTED...WHICH THROUGH DIFFERENT METHODS ARE QUITE
DIFFERENT. HENCE...FORECAST SNOWFALL AMOUNTS ACROSS EASTERN MN
AND WESTERN WI MAY BE AN INCH OR TWO TOO HIGH.

FURTHER WEST AND SOUTH...CONFIDENCE IS INCREASING ON SEVERAL
INCHES OF SNOW SATURDAY EVENING ALONG WITH 20 TO 25 MPH SUSTAINED
WINDS. THE SNOW AND WIND WILL CONTINUE OVERNIGHT AND EARLY SUNDAY
MORNING WITH LOCATIONS ACROSS WEST CENTRAL THROUGH SOUTH CENTRAL
SEEING 4 TO LOCALLY 6 INCHES OF SNOW ALONG WITH CONSIDERABLE
BLOWING AND DRIFTING SNOW. TEMPORARY WHITEOUT CONDITIONS ARE
POSSIBLE IN THESE AREAS SATURDAY NIGHT. WE DEBATED ON ISSUING A
BLIZZARD WATCH...BUT SINCE THIS IS A WAA EVENT...THE MIXING LAYER
IS RATHER SHALLOW (1500 FEET) WITH TOP OF THE CHANNEL WINDS NEAR
30 MPH FOR AN HOUR OR TWO. A BLOWING SNOW MODEL THAT WE USE TO
EVALUATE BLIZZARD POTENTIAL INDICATED LOW PROBABILITIES. IF
SUSTAINED WINDS WERE A LITTLE HIGHER...MORE IN THE 25 TO 30 MPH
RANGE...THEN PROBABILITIES FOR A BLIZZARD START TO CLIMB. IN THE
END...WE ISSUED A WINTER STORM WATCH FOR SATURDAY NIGHT AND EARLY
SUNDAY MORNING FOR THE AFOREMENTIONED AREAS DUE TO THE SNOW AND
BLOWING/DRIFTING SNOW. A CHECK OF THE CIPS ANALOGS SHOWED THAT THE
NUMBER ONE ANALOG (19800205) HAD 4 TO LOCALLY 6 INCHES OF SNOW
FROM EASTERN SOUTH DAKOTA THROUGH SOUTHWEST MINNESOTA TO EASTERN
IOWA.

LOOKING PAST THE WEEKEND...YET ANOTHER STRONG SHORT WAVE IS
HEADED OUR WAY FROM THE NORTHWEST FOR TUESDAY. THE GFS AND ECMWF
HAVE SIMILAR TIMING ON THIS FEATURE BUT ARE AT ODDS ON THE PATH.
THE GFS WOULD INDICATE ACCUMULATING SNOW FROM THE TWIN CITIES ON
NORTH AND EAST WHILE THE ECMWF WOULD HAVE THE SNOW MUCH FATHER
WEST AND SOUTH. AT THIS POINT...SMALL CHANCE POPS COVER THE AREA
BUT THIS COULD CERTAINLY CHANGE IN THE NEXT FEW DAYS.

A WARMING TREND WILL COMMENCE FOR THE LATTER HALF OF THE WORK
WEEK WITH HIGHS RISING INTO THE 30S. WITH THE INFLUX OF WARMER AIR
WILL COME THE CHANCE FOR SOME RAIN AND SNOW. NOTHING TOO
SIGNIFICANT AT THIS TIME WITH MUCH OF THE PRECIPITATION FORECAST
TO THE NORTH OF US.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1139 AM CST FRI FEB 12 2016

GENERALLY CLEAR SKIES FOR THE PERIOD. WINDS NW 10-15 GUSTING OVER
20 KNOTS THROUGH SUNSET...THEN DIMINISHING AND BECOMING LIGHT AND
VARIABLE OVERNIGHT...WHEN TEMPERATURES FALL WELL BELOW ZERO. WINDS
EVENTUALLY DEVELOP A SE COMPONENT LATE IN THE PERIOD
TOMORROW.

KMSP...NO CHANGE FROM MAIN DISCUSSION.

/OUTLOOK FOR KMSP/
SUN...MVFR/IFR WITH -SN LIKELY. WIND SSE 15 KT.
MON...MVFR/VFR CIGS. WIND W 10 KT.
TUE...MVFR/VFR WITH -SN POSSIBLE.  WIND NW 10 KT.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
WI...WIND CHILL ADVISORY UNTIL 8 AM CST SATURDAY FOR WIZ014>016-
     023>028.

MN...WINTER STORM WATCH FROM SATURDAY EVENING THROUGH SUNDAY MORNING
     FOR MNZ054>056-064-065-073>075-082-083-091-092.

     WIND CHILL ADVISORY UNTIL 8 AM CST SATURDAY FOR MNZ074>078-
     082>085-091>093.

&&

$$

SHORT TERM...SPD
LONG TERM...RAH
AVIATION...SPD



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