Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 020000
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
600 PM CST MON FEB 1 2016

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 451 PM CST MON FEB 1 2016

CURRENT WATER VAPOR IMAGERY SHOWS STRONG LOW PRESSURE IN THE MID
LEVELS SPINNING AWAY JUST EAST OF THE FOUR CORNERS AREA. THE VARIOUS
MODELS HAVE COME AROUND TO PRETTY GOOD AGREEMENT WITH REGARDS TO THE
TRACK OF THE 500MB LOW TONIGHT AND TUESDAY...EJECTING THE CENTER OF
THE LOW INTO SOUTHEAST NEBRASKA BY 00Z WEDNESDAY. THE SURFACE LOW
FOLLOWS SUIT...WITH A TRACK FROM NEAR THE OKLAHOMA PANHANDLE
MIDNIGHT TONIGHT...TO NEAR ST. JOE MISSOURI AND FALLS CITY NEB BY
00Z WEDNESDAY. THE MOST MARKED CHANGE IS IN THE NAM...WHICH HAS MADE
A DRAMATIC SHIFT NORTHWARD IN ITS FORECAST WHICH NOW MIMICS THE
GLOBAL MODELS. THE GEM IS ALSO TRENDING NORTHWARD.

IT WILL TAKE A LITTLE WHILE FOR THE 850-700MB LAYER TO SATURATE UP
FROM SOUTH TO NORTH AS THE NIGHT PROGRESSES. THEREFORE SLOWED DOWN
THE BEGINNING OF THE SNOWFALL THIS EVENING FOR OUR SOUTHERN ZONES.
THE SNOW WILL LIKELY NOT BEGIN FOR LOCATIONS ALONG AND NORTH OF I 90
UNTIL VERY LATE TONIGHT OR EARLY TUESDAY. WITH THE OVERALL TREND OF
THE MODELS SHIFTING NORTHWARD...AT LEAST THE NAM AND GEM...THAT
LEADS TO SOME CONFIDENCE TO EXPAND THE BLIZZARD WARNING TO THE NORTH
AND WEST...GENERALLY ALONG AND EAST OF A LINE FROM TYNDALL SOUTH
DAKOTA...TO SIOUX FALLS...AND IVANHOE/MARSHALL MN. WINDS WERE NEVER
REALLY QUESTION FOR THIS EVENT...WITH THE MIXED LAYER MEAN WINDS
ABOUT 35 TO 40 KNOTS TUESDAY AND TUESDAY NIGHT. BUT NOW WITH HEAVIER
SNOW EXPECTED TO THE WEST OF THE ORIGINAL BLIZZARD WARNING...FEEL
THAT WHITE OUT CONDITIONS WILL BE A PROBLEM NOW IN THE NEW AREA. ON
THE BACKSIDE OF THE SNOWBAND...HAVE ISSUED A WINTER WEATHER ADVISORY
FROM GREGORY COUNTY...TO MITCHELL AND BROOKINGS FOR AROUND 2 TO 4
INCHES OF SNOW AND WINDY CONDITIONS. BUT THEIR WIND SHOULD AVERAGE
ABOUT 10 MPH LESS THEN THE WARNED AREA. FRONTOGENESIS IS FAIRLY
STRONG ESPECIALLY IN THE MID LEVELS...WHERE THE LATEST NAM SPLITS
THE 700MB FORCING INTO TWO DISTINCT LOCATIONS. THE FIRST ONE MOVES
NORTHWARD INTO NORTHWEST IOWA THIS EVENING WHICH WILL BASICALLY BE
WASTED SATURATING UP THE LOWER LAYERS. THEN IT PINWHEELS WESTWARD
INTO THE NEW BLIZZARD WARNING SEGMENT LATE TONIGHT AND TUESDAY.
FRONTOGENESIS REMAINS DEEP IN NORTHWEST IOWA AND SOUTHWEST MN FROM
850-650MB ON TUESDAY...AND OUR EASTERN ZONES ALSO HAVE LESS STABLE
EPV* TO DEAL WITH WHICH SHOULD ADD TO SNOW AMOUNTS ALONG AND EAST OF
HIGHWAY 60. SO FOR THE BLIZZARD WARNING AREA...EXPECTING A SOLID 8
TO 13 INCHES OF SNOW ALONG AND EAST OF HIGHWAY 60...TO 6 TO 8 INCHES
IN EXTREME SOUTHEAST SD AROUND YANKTON AND SIOUX FALLS. AMOUNTS WILL
BE A LITTLE LIGHTER ON THE WEST SIDE OF THE BLIZZARD WARNING...BUT
REMEMBER IT WILL NOT TAKE A LOT OF SNOW TO CREATE WHITE OUT
CONDITIONS WITH 25 TO 45 MPH WIND SPEEDS. ONE OTHER INTERESTING
FEATURE IS THE JET...A SECONDARY JET STREAK DEVELOPS IN CENTRAL MN
AND THE WESTERN GREAT LAKES REGION LATE TONIGHT AND TUESDAY WHICH
WILL PLACE OUR AREA IN THE RIGHT ENTRANCE REGION OF THAT JET STREAK.
WITH THE PRIMARY JET TO THE SOUTH NEAR THE UPPER LOW...THAT MEANS
THE ENTIRE EASTERN HALF OF OUR FA WILL BE IN A SUBTLE COUPLED JET
ADDING TO BROAD SCALE ASCENT ON TOP OF THE MESOSCALE ASCENT PROVIDED
BY THE FRONTOGENESIS.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 451 PM CST MON FEB 1 2016

BLIZZARD CONDITIONS LINGERING INTO TUESDAY NIGHT WITH STRONGEST
WINDS IN THE UPPER MIXED LAYER ACTUALLY DURING THE EARLY EVENING AT
40 TO 45 KNOTS...WITH WORST CONDITIONS WHERE SNOWFALL CONTINUES.
LIKELY THE ONLY MODERATE SNOWFALL REMAINING BY EARLY EVENING WILL BE
ACROSS PORTIONS OF SOUTHWEST MINNESOTA INTO NORTHWEST IOWA WHERE
TAIL END OF WEAK TROWAL CONTINUES TO LINGER...WITH GENERALLY LIGHT
SNOWFALL ELSEWHERE. AS SNOWFALL WINDS DOWN LATER IN THE EVENING AND
EARLY OVERNIGHT...AND WINDS ACTUALLY START TO GRADUALLY EASE...
SHOULD SEE THE COVERAGE OF BLOWING SNOW ACROSS NORTHWEST IOWA...
SOUTHEAST SOUTH DAKOTA AND SOUTHWEST MINNESOTA SLOWLY DIMINISH AS
WELL...BUT AREAS OF BLOWING SNOW WILL CONTINUE RIGHT INTO EARLY
MORNING MAINLY EAST OF I 29.

WINDS WILL CONTINUE TO EASE ON WEDNESDAY...AND NEW SNOW AND COLD
ADVECTION LIKELY TO KEEP TEMPS ON THE CHILLY SIDE. COULD EVEN SEE A
FEW FLURRIES WITH LOW LEVEL SCATTERED TO BROKEN CLOUDS. ANOTHER
REINFORCING WAVE SLIPS SOUTHEAST BY LATER WEDNESDAY...BUT SHOULD BE
NO MORE THAN A CLOUD PRODUCER. GOOD THING FOR THE CLOUDS...WITH WEAK
RIDGE SHIFTING OVER EARLY EVENING AND DECOUPLED WINDS...WOULD BE
OPEN TO GET QUITE CHILLY...BEFORE INCREASING WEST TO SOUTHWEST
GRADIENT ALLOWS FOR RISING TEMPS LATER IN THE NIGHT. ANOTHER FAIRLY
COMPACT WAVE MOVES TOWARD EASTERN SOUTH DAKOTA LATE NIGHT AND EARLY
MORNING...AND PERHAPS WILL NEED TO THINK ABOUT A FEW FLURRIES OR
LIGHT SNOW CHANCES AHEAD OF SYSTEM.  AS WAVE PASSES BY...WILL GET A
REINFORCING COLD FRONT DURING THE AFTERNOON WHICH COULD START SOME
FALLING TEMPS NORTH TO SOUTH IN THE AFTERNOON.  THE ROLLER COASTER
CONTINUES WITH ANOTHER SPLITTING WAVE BY FRIDAY...TURNING WINDS BACK
AROUND SOUTHERLY AFTER WEAK RIDGE THURSDAY NIGHT. NOT MUCH FOR
EFFECTIVE DYNAMICS...AND PERHAPS A SMALL CHANCE FOR LIGHT SNOW
NORTHEAST. PUSH OF MILDER TEMPS STARTS ON FRIDAY...WITH RETURN TO
30S...MID TO UPPER 30S IN THE LESSER SNOW AREAS WEST.

QUIETER AND GENTLER WEATHER WILL DWELL FOR MUCH OF THE LONGER RANGE
PERIOD FOLLOWING THE WINTER STORM.  FOR THE MOMENT...A SMALL
CONSENSUS THAT TEMPS WILL WARM QUITE A BIT ON SATURDAY WITH A
MODERATE WEST TO SOUTHWEST FLOW...AND AGAIN LESSER SNOW AREAS WEST
MAY SEE SOME LOWER TO MID 40S. ANOTHER WAVE AROUND SUNDAY WILL PUSH
A FRONT THROUGH...AND BEING A FAIRLY DISTINCT UPPER PV
ANOMALY...HAVE BUMPED UP TO A LOWER CHANCE POP AT THIS TIME. MAY BE
WARM ENOUGH FOR A LITTLE RAIN TO START...BUT GENERALLY SNOW AS TEMPS
ALOFT WILL BEGIN TO FALL AS PRECIP FORCING PUSHES SOUTHEAST. A SOLID
PUSH OF MUCH COLDER AIR WILL SETTLE IN MONDAY WITH BRISK NORTHERLY
WINDS.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 535 PM CST MON FEB 1 2016

VFR CONDITIONS THIS EVENING WILL RAPIDLY DETERIORATE FROM SOUTH TO
NORTH OVERNIGHT INTO THE MID MORNING. STRONG WINDS AND SNOW WILL
SPREAD ACROSS THE REGION...WITH CEILINGS AND VISIBILITY QUICKLY
DROPPING TO IFR AND LIFR IN SNOW AND BLOWING SNOW. POOR CONDITIONS
WILL LAST THROUGH THE END OF THE TAF PERIOD...AND WILL MAINLY
IMPACT FAR SOUTHEAST SD...NORTHEAST NE...NORTHWEST IOWA AND
SOUTHWEST MINNESOTA - INCLUDING KFSD AND KSUX. KHON WILL BE AT THE
EDGE OF THE SNOW BAND...BUT WILL LIKELY SEE AT LEAST MVFR OR BRIEF
IFR CEILINGS AND VISIBILITY. WINDS WILL INCREASE TO 25 TO 40 KT ON
TUESDAY.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...BLIZZARD WARNING FROM 3 AM TUESDAY TO 4 AM CST WEDNESDAY FOR
     SDZ056-061-062-065>071.

     WINTER WEATHER ADVISORY FROM 6 AM TUESDAY TO MIDNIGHT CST
     TUESDAY NIGHT FOR SDZ040-050-054-055-059-060-063-064.

MN...BLIZZARD WARNING FROM 3 AM TUESDAY TO 4 AM CST WEDNESDAY FOR
     MNZ071-072-080-081-089-090-097-098.

IA...BLIZZARD WARNING FROM 3 AM TUESDAY TO 4 AM CST WEDNESDAY FOR
     IAZ001>003-012>014-020>022-031-032.

NE...BLIZZARD WARNING FROM 3 AM TUESDAY TO 4 AM CST WEDNESDAY FOR
     NEZ013-014.

&&

$$

SHORT TERM...MJ
LONG TERM...CHAPMAN
AVIATION...


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