Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 160431
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1031 PM CST SAT NOV 15 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 317 PM CST SAT NOV 15 2014

EVERYTHING PANNING OUT PRETTY MUCH AS EXPECTED WITH A WIDESPREAD 3
TO 5 INCHES OF SNOWFALL. SOME ENHANCED BANDING JUST NORTH OF SIOUX
FALLS EAST DOWN INTERSTATE 90 INTO SOUTHWEST MINNESOTA MAY HAVE
PRODUCED SOME ISOLATED 6 TO 6.5 INCH SPOTS. LUCKILY WITH THIS CASE
THE SNOW IS VERY LIGHT AND FLUFFY AND THERE IS LITTLE IF ANY WIND
THUS FAR SO NO MAJOR BLOWING AND DRIFTING. THERE IS STILL GOING TO
BE SOME BLOWING SNOW LATE THIS AFTERNOON WEST OF THE JAMES RIVER BUT
NOT QUITE ENOUGH TO CAUSE MAJOR PROBLEMS. FORCING SHIFTS EAST THROUGH
THE EVENING AND BY ABOUT 8 PM MOST OF THE MEASURABLE SNOW WILL BE
EAST OF INTERSTATE 29 AND BY ABOUT 1 AM THE SNOW SHOULD BE OUT OF
THE CWA. COLDER AIR FILTERS IN BEHIND WITH SOME CLEARING EXPECTED SO
FAIRLY COLD OVERNIGHT.

SUNDAY AND ESPECIALLY SUNDAY AFTERNOON POSES A DIFFERENT PROBLEM
WHICH WILL BE BLOWING SNOW. IN THE MORNING WINDS WILL MAINLY BE FROM
THE WEST AS A VERY STRONG PV ANOMALY DROPS SOUTH INTO SOUTH DAKOTA.
AS THIS PV ANOMALY MOVES THROUGH DURING THE AFTERNOON NORTHWEST
WINDS WILL INCREASE QUITE A BIT AS STRONG COLD AIR ADVECTION SWINGS
THROUGH. THIS WILL START TO CHURN UP THE LIGHT FLUFFY SNOW THATS
CURRENTLY ON THE GROUND AND SHOULD DROP VISIBILITIES PRETTY QUICKLY
AS GUSTS CLIMB UP CLOSE TO 40 MPH. DURING THE AFTERNOON THE MAIN
THREAT WILL BE WEST OF INTERSTATE 29. HIGHS MAINLY IN THE 20S BUT
FALLING PRETTY QUICKLY LATE IN THE AFTERNOON AND EVENING.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 317 PM CST SAT NOV 15 2014

STRONG FRONT AND PRESSURE RISE COUPLET WORKING THROUGH THE
REMAINDER OF THE AREA SHORTLY AFTER 00Z...AND WILL BE ACCOMPANIED
BY PULSE OF STRONGER WINDS DURING THE EARLY EVENING. WINDS MAY
COME DOWN BRIEFLY...BUT CONTINUED COLD AIR ADVECTION OVERNIGHT
ALONG WITH WINDS OF 30 TO 35 KNOTS IN THE MIXED LAYER WILL KEEP
STRONG AND GUSTY WINDS THROUGH MUCH OF THE NIGHT. AREAS OF BLOWING
SNOW WILL CONTINUE TO BE THE PRIMARY CONCERN. IN FACT...ADDITIONAL
SUBSIDENCE WITH GRADIENT INCREASING FOR A TIME BEHIND THE UPPER
WAVE ALONG WITH SHALLOW MIXING ON MONDAY SHOULD BRING THE MORE
PERSISTENT AND GUSTY WINDS...AND LIKELY REDUCTION IN VISIBILITY.
THROUGH THE SUNDAY NIGHT AND MONDAY PERIOD...NOT OUT OF THE
QUESTION WITH CHARACTER OF SNOW THAT COULD BE SOME PERIODS OF NEAR
BLIZZARD CONDITIONS...ESPECIALLY IF CAN AUGMENT WITH A FEW DAYTIME
FLURRIES...WHICH WOULD APPEAR PROBABLE GIVEN THE LOWER LEVEL LAPSE
RATES. BY LATER MONDAY...SURFACE GRADIENT WILL START TO DROP OFF
ENOUGH THAT WESTERN AREAS WILL IMPROVE BY MID AFTERNOON...AND BY
SUNSET IN THE EAST. OTHER FACET OF WINDS WILL COME WITH THE COLD
TEMPS...WITH WIND CHILLS LARGELY 10 BELOW TO 20 BELOW ZERO SUNDAY
NIGHT THROUGH MONDAY NIGHT. LOOKS TO BE A SOLID BET FOR A RECORD
LOW MAXIMUM TEMPERATURE ON MONDAY.

ON MONDAY NIGHT...WITH SURFACE RIDGE BUILDING INTO THE AREA...
ENOUGH RELAXATION OF THE GRADIENT FROM AROUND I 29 WESTWARD ALONG
WITH CLEARING POTENTIAL TO ALLOW STRONGER COOLING THAN GUIDANCE
SUGGESTS...AND HAVE TAKEN A GOOD SOLID 4-7 DEGREES OFF VALUES FOR
OVERNIGHT LOWS. RETURN FLOW KICKS IN TUESDAY...AND WHILE WILL GET
OFF SURFACE TO WARM CONSIDERABLY...LIKELY WITH SNOWCOVER AND EARLY
INVERSION TO FIND LESS OF AN IMPACT ON WARMING SURFACE TEMPS...
ESPECIALLY GIVEN THE DEGREE OF HIGH CLOUDS STREAMING IN AHEAD OF
NEXT NORTHWEST FLOW WAVE DURING THE PEAK OF THE DAY.

LONGER TERM WROUGHT WITH TIMING DIFFERENCES BETWEEN VARIOUS
SOLUTIONS...AND EVEN SOME DIFFERENCES ON EVOLVING THE LARGER
SCALE...UNDER A GRADUALLY DEAMPLIFYING PATTERN BY THE WEEKEND.
ECMWF SOMEWHAT OFF ON ITS OWN WITH STRENGTH AND PERSISTENCE OF
FEATURES BY LATE WEEK...AND HAVE ADJUSTED TOWARD MORE OF A MEAN
BETWEEN IT AND THE PUSHY GFS...ALONG WITH ENSEMBLE CLUSTERING
TOWARD SLOWER CHANGE.

LIKELY TO SEE A FEW MORE FLURRIES WITH NEXT SURGE ON LATER TUESDAY
NIGHT AND WEDNESDAY...AND WILL DRIVE TEMPS DOWN SEVERAL DEGREES
ONCE AGAIN. WINDS WILL PICK UP AGAIN LATER TUESDAY NIGHT WITH
STRONG COLD ADVECTION AND HEALTHY UNIDIRECTIONAL FLOW. LIKELY NOT
AS STRONG AS WINDS FROM SUNDAY NIGHT/MONDAY...AND MODIFICATION OF
THE SNOWPACK SHOULD LESSEN THREAT FOR BLOWING SNOW.

HEADING TO THE CLOSE OF THE WEEK AND START OF THE WEEKEND...WILL
GET ANOTHER POTENTIAL WINDOW FOR MORE EXTREME OVERNIGHT COOLING
FOR THURSDAY NIGHT...THEN WATCHING A GRADUAL MODERATION THROUGH
SATURDAY. WOULD NOT BE SHOCKED TO FIND NEED TO ADD IN A LIGHT
PRECIP THREAT BY SATURDAY...GIVEN TRENDS TO SETTING UP WARM AIR
ADVECTION/CONFLUENCE NEAR THE AREA.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1032 PM CST SAT NOV 15 2014

VISIBILITIES 1-3SM IN SNOW IN SOUTHWEST MN AND NORTHWEST IA WILL
END BY 09Z. CEILINGS 1-3K FEET IN THE SAME AREA WILL IMPROVE TO
VFR BY 11Z. VFR CONDITIONS SHOULD THEN CONTINUE THROUGH 18Z.
18Z-17/00Z NORTHWESTERLY SURFACE GUSTS TO 25 KNOTS WILL DEVELOP
FROM THE WEST WITH ISOLATED AREAS OF VISIBILITY 3-5SM IN BLSN.
THESE CONDITIONS WILL CONTINUE THROUGH 17/06Z.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY FROM 3 PM SUNDAY TO 6 PM CST MONDAY FOR
     SDZ039-040-054>056-060>062-065>071.

     WINTER WEATHER ADVISORY FROM NOON SUNDAY TO 3 PM CST MONDAY FOR
     SDZ038-050-052-053-057>059-063-064.

MN...WINTER WEATHER ADVISORY FROM 3 PM SUNDAY TO 6 PM CST MONDAY FOR
     MNZ071-072-080-081-089-090-097-098.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR MNZ081-
     090.

IA...WINTER WEATHER ADVISORY FROM 3 PM SUNDAY TO 6 PM CST MONDAY FOR
     IAZ001>003-012>014-020>022-031-032.

     WINTER WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR IAZ002-
     003-013-014-021-022-032.

NE...WINTER WEATHER ADVISORY FROM 3 PM SUNDAY TO 6 PM CST MONDAY FOR
     NEZ013-014.

&&

$$

SHORT TERM...08
LONG TERM...CHAPMAN
AVIATION...



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