Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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411
FXUS63 KFSD 020845
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
245 AM CST TUE FEB 2 2016

...BLIZZARD EXPECTED ACROSS THE REGION TODAY...

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 242 AM CST TUE FEB 2 2016

EARLY THIS MORNING...WATCHING A VERY POWERFUL WINTER STORM
DEVELOP ACROSS THE SOUTHERN PLAINS. DRY AIR ALOFT HAS CERTAINTY
HAD A BIT OF AN IMPACT OVER THE AREA...OUTSIDE OF A RATHER
PERSISTENT BAND OF 700 MB FRONTOGENESIS ALONG THE SOUTHERN FRINGES
OF THE CWA. THE REAL SHOW CONTINUES TO DEVELOP OVER THE MID/LOWER
MO RIVER VALLEY AS BROAD DIFFLUENCE OVERSPREAD THE REGION.

MODELS HAVE TRENDED A BIT SLOWER OVERNIGHT BUT THE OVERALL TRACK
OF THIS SYSTEM SEEMS TO BE HANDLED RELATIVELY WELL. MODERATE TO
HEAVY SNOWS WILL LIFT NORTHWARD AFTER DAYBREAK...WITH INTENSE
FRONTOGENESIS IN THE 750-650MB LAYER FORMING JUST SOUTH OF THE CWA
AND PIVOTING NORTH AND NORTHEAST INTO THE EARLY AFTN. LATEST HIGH
RES GUIDANCE ALSO SHOWING A BIT OF ELEVATED INSTABILITY THROUGH
MID- MORNING ACROSS THE SOUTHERN AND SOUTHEASTERN ZONES...WHILE
THE POTENTIAL FOR THUNDERSNOW IS LOW...I WOULD NOT RULE IT OUT. AS
THE INITIAL WAVE OF SNOW LIFTS NORTHWARD...WE SHOULD SEE SOME
IMPRESSIVE RATES...UPWARDS OF 2 TO 4 INCHES OF SNOW PER HOUR AT
TIMES INTO MID- DAY.

BY THE AFTERNOON...WOULD ANTICIPATE MID-LVL DRY SLOT TO PIVOT INTO
IOWA AND SKIRT THE FAR SOUTHEASTERN CWA...THIS MAY TEMPORARILY LOWER
SNOW RATES IN THE FAR SOUTHEAST AND EAST THIS AFTERNOON...SHIFTING
THE FOCUS FOR HEAVIER SNOW TOWARDS PORTIONS OF CENTRAL AND EASTERN
MINNESOTA.  HOWEVER...WE WILL NOT BE DONE WITH THE SNOW UNTIL WELL
INTO THE EVENING HOURS...AS THIS MATURE SYSTEM SHOULD HAVE A WELL
FORMED TROWAL...WITH NEARLY 50 KNOTS OF FLOW ROTATING AROUND THE
WESTERN FLANK OF THE SYSTEM. WHILE THE SNOW RATES MAY BEGIN TO TAPER
OFF IN THE LATE AFTERNOON AND EVENING HOURS...AM ANTICIPATING
ACCUMULATING SNOWS UNTIL AT LEAST MIDNIGHT.

THE NORTHWESTERN FLANK OF THIS SYSTEM SHOULD HAVE A FAIRLY TIGHT
GRADIENT IN AMOUNTS...ESPECIALLY WITH DRY AIR ADVECTING SOUTHWEST
INTO THE WESTERN DAKOTAS.  THE MOST UNCERTAINTY IN THE FORECAST IS
IN THE FAR NORTHWESTERN CWA...WHERE IT IS POSSIBLE THAT LITTLE SNOW
FALLS NEAR HURON...CHAMBERLAIN AND DE SMET. THAT SAID...WITH
TROWAL AXIS SETTLING IN A BIT FURTHER WEST AND NORTHWEST...HAVE
BUMPED UP TOTALS THROUGH THE MID-SECTION OF THE CWA SLIGHTLY.

WHAT MAKES THIS SYSTEM DANGEROUS WILL BE THE VERY STRONG WINDS
EXPECTED TO MOVE THROUGH THE AREA. LATEST GUIDANCE CONTINUES TO
SUGGEST A SPG OF NEARLY 60 UBAR/KM WITH 0-0.5KM WINDS FROM NAM/GFS
PUSHING 45 KNOTS AS THE SFC LOW TRACKS ACROSS SOUTHERN IA.  THINKING
THAT A FEW GUSTS UPWARDS OF 50 MPH WILL BE POSSIBLE FROM MID-MORNING
THROUGH THE AFTERNOON. THE SPG WILL BEGIN TO RELAX LATE THIS
EVENING...BUT 20-30 MPH SUSTAINED WINDS WITH 35 MPH GUSTS LOOK TO
CONTINUE THROUGH AT LEAST MIDNIGHT. GIVEN THE LOWER SLR DURING THE
INITIAL HEAVY SNOW...VISIBILITIES WILL BE SIGNIFICANTLY REDUCED
TO NEAR WHITE OUT CONDITIONS AT TIMES. THE QUESTION WILL BE HOW
MUCH THE SNOW WILL BLOW AROUND ONCE IT IS FINISHED AFTER MIDNIGHT.

THAT SAID...DO NOT ANTICIPATE ANY CHANGES TO PRODUCTS THIS
MORNING...AS CURRENT HEADLINES LOOK GOOD. GIVEN WINDS OF THIS
MAGNITUDE...POTENTIAL SNOW ACCUMULATIONS AND SOMEWHAT WET NATURE OF
THE SNOW...ALSO CONCERNED ABOUT POTENTIAL POWER OUTAGES IN ADDITION
TO SIGNIFICANT DRIFTING.


.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 242 AM CST TUE FEB 2 2016

TEMPERATURES AND SMALL CHANCES OF PRECIPITATION ARE THE MAIN
FORECAST CHALLENGES IN THE LONGER RANGE.  DEEP NORTHWEST FLOW
THROUGH THE TROPOSHPERE WILL KEEP TEMPERATURES BELOW NORMAL ON
WEDNESDAY. AS THE STRONG LOW PRESSURE SYSTEM SHIFTS INTO THE GREAT
LAKES REGION...WINDS WILL BE ON THE DECREASE THROUGHOUT THE DAY BUT
COULD STILL SEE SOME BLOWING SNOW THROUGH THE MORNING HOURS. WITH
DEEP FRESH SNOW PACK IN THE EAST AND 925 HPA TEMPS REMAINING THE
TEENS BELOW ZERO...HAVE COOLED HIGHS IN THE EAST SOME.

SHORTWAVES DROP DOWN IN NORTHWEST FLOW ON THURSDAY AND FRIDAY
AFTERNOON AS NORTHERN BRANCH OF THE JET BECOMES REESTABLISHED.  WHILE
THE WAVES ARE MAINLY FOCUSED ON CENTRAL MINNESOTA...ATMOSPHERE IS
EFFICIENT ENOUGH TO WARRANT SMALL POPS IN SOUTHWEST MINNESOTA.  LIFT
IN THE ATMOSPHERE IS CENTERED IN THE DENDRITIC GROWTH ZONE...AND
THERE IS SUFFICIENT MOISTURE AVAILABLE. AHEAD OF BOTH WAVES...925
HPA TEMPERATURES WARM TO NEAR 0C. HAVE RAISED FORECAST LOWS CLOSE TO
BCCONS_ALL AND BCCONS_MOS BOTH WEDNESDAY NIGHT AND THURSDAY NIGHT IN
THE EAST WHERE CLOUDS WILL HANG TOUGH THROUGH MUCH OF THE NIGHT.

FAIRLY BROAD WAVE IS EXPECTED TO IMPACT THE REGION ON SUNDAY INTO
SUNDAY NIGHT.  WAVE IS FAIRLY DISORGANIZED...AND THEREFORE STUCK
WITH GUIDANCE POPS FOR NOW.

LOOKS WINDY AND COOLER EARLY NEXT WEEK AS BRISK NORTHWEST FLOW
DEVELOPS ACROSS THE PLAINS IN THE WAKE OF THE DEPARTING WAVE. EXPECT
A PROLONGED PERIOD OF FALLING TEMPERATURES ON MONDAY AND
TUESDAY...AND IF THE GFS VERIFIES...IT WOULD CONTINUE INTO WEDNESDAY
AS WELL.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1020 PM CST MON FEB 1 2016

AREAS OF LOW STRATUS CONTINUES TO EXPAND ACROSS THE EASTERN HALF
OF THE REGION...WHILE VFR CONDITIONS TO THE WEST WILL CONTINUE TO
RAPIDLY DETERIORATE OVERNIGHT AND EARLY TUESDAY. STRONG WINDS AND
SNOW WILL SPREAD NORTHEAST ACROSS THE REGION...WITH CEILINGS AND
VISIBILITY QUICKLY DROPPING TO IFR AND LIFR IN MODERATE TO HEAVY
SNOW AT TIMES. WITH WINDS INCREASING TO 25 TO 40 KT ON
TUESDAY...BLOWING SNOW WILL ALSO BE A CONCERN AND WILL FURTHER
REDUCE VISIBILITY TO LESS THAN A QUARTER MILE AT TIMES. SNOW
BEGINS TO TAPER OFF FROM WEST TO EAST THIS EVENING...BUT STRONG
WINDS MAY CONTINUE TO CREATE BLOWING SNOW ISSUES INTO THE END OF
THE TAF PERIOD. THE HEAVIEST SNOWFALL IS EXPECTED ACROSS THE
SOUTHEAST HALF OF THE REGION...AND WILL BE A MAJOR IMPACT AT KFSD
AND KSUX.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...BLIZZARD WARNING UNTIL 4 AM CST WEDNESDAY FOR SDZ065>071.

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

     BLIZZARD WARNING FROM 6 AM THIS MORNING TO 4 AM CST WEDNESDAY
     FOR SDZ056-061-062.

MN...BLIZZARD WARNING FROM 6 AM THIS MORNING TO 4 AM CST WEDNESDAY
     FOR MNZ071-072-080-081-089-090-097-098.

IA...BLIZZARD WARNING UNTIL 4 AM CST WEDNESDAY FOR IAZ001>003-012>014-
     020>022-031-032.

NE...BLIZZARD WARNING UNTIL 4 AM CST WEDNESDAY FOR NEZ013-014.

&&

$$

SHORT TERM...DUX
LONG TERM...
AVIATION...



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