Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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029
FXUS63 KFSD 112140
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
340 PM CST THU FEB 11 2016

.SHORT TERM...(THIS EVENING THROUGH FRIDAY)
ISSUED AT 340 PM CST THU FEB 11 2016

SNOWFALL CONTINUES TO MOVE SOUTHEASTWARD ACROSS THE FORECAST AREA AT
THIS TIME. THE SNOW IS ALIGNED VERY WELL WITH THE 750-700MB
FRONTOGENESIS LAYER...AND THE UPPER SUPPORT WILL EXIT OUR SOUTHEAST
ZONES IN NORTHWEST IA BETWEEN 00Z AND 03Z THIS EVENING. AT THE
MOMENT...RADAR TRENDS SHOW THE HEAVIER SNOWFALL TRACKING MORE
SOUTHEASTWARD INTO THE HEART OF NORTHWEST IA...INSTEAD OF SOUTH
TOWARD SIOUX CITY. THEREFORE MAY HAVE TO DECREASE SNOW AMOUNTS IN
SIOUX CITY AND YANKTON LOCATIONS. OVERNIGHT LOWS STILL LOOK ON TRACK
HOWEVER THEY ARE A BIT PROBLEMATIC IN FAR NORTHERN ZONES FROM NEAR
BROOKINGS OVER TO THE MARSHALL MN VICINITY. THERE IS SOME EVIDENCE
ON THE HIRES MODELS THAT CLEARING COULD OCCUR OVER THOSE LOCATIONS
LATE TONIGHT. HOWEVER WITH INCREASING WINDS THE TEMPERATURES STILL
MAY NOT PLUMMET TOO BAD.

THE NEXT COLD AIR SURGE DEFINITELY ADVECTS IN FOR FRIDAY.
TEMPERATURES WILL LIKELY NOT MOVE A WHOLE LOT THROUGH THE DAY AND
CONDITIONS WILL BE BREEZY...ESPECIALLY ALONG AND EAST OF INTERSTATE
29. BUT IT SHOULD BE A SUNNY DAY.


.LONG TERM...(FRIDAY NIGHT THROUGH THURSDAY)
ISSUED AT 340 PM CST THU FEB 11 2016

FOCUS IN THE MEDIUM RANGE IS THE SERIES OF WAVES THAT ARE EXPECTED
TO IMPACT THE AREA ON SATURDAY INTO SUNDAY.  LEADING WAVE IS
FIGHTING QUITE A BIT OF DRY AIR IN THE LOWER LEVELS OF THE
ATMOSPHERE AND HAVE KEPT POPS ACROSS THE WESTERN HALF OF THE
FORECAST AREA. MODELS ARE STARTING TO COME INTO BETTER AGREEMENT ON
THE TRACK OF THIS SYSTEM...AND WITH THE GFS/ECMWF REMAINING THE MOST
CONSISTENT AND SOLUTIONS CONVERGING TOWARDS THOSE SOLUTIONS...HAVE
STUCK CLOSE TO THOSE SOLUTIONS.  AS THE MAIN WAVE MOVES THROUGH
SATURDAY NIGHT INTO SUNDAY...SNOW SHOULD DEVELOP ACROSS CENTRAL AND
EASTERN PORTIONS OF THE FORECAST AREA. SNOW RATIOS LOOK TO BE AROUND
14-16:1. LIFT IS ENHANCED BY RIGHT ENTRANCE REGION OF JET CENTERED
ON THE TENNESSEE RIVER VALLEY. HAVE INCREASED POPS INTO THE
CATEGORICAL RANGE SATURDAY NIGHT ACROSS THE EASTERN HALF OF THE
FORECAST AREA. IN ADDITION...INCREASING SOUTHEASTERLY WINDS WILL
LIKELY CREATE SOME AREAS OF BLOWING SNOW....ESPECIALLY THROUGH THE
OVERNIGHT HOURS.

AS THE BOUNDARY SHIFTS THROUGH THE AREA ON SUNDAY...SNOW SHOULD COME
TO AN END ACROSS THE AREA.  MODELS SHOW WARMER AIR MOVING INTO THE
REGION BUT QUESTIONS REMAIN ABOUT HOW AGGRESSIVE THE WARM WILL BE.
THE GFS KEEPS 925 HPA TEMPS BELOW ZERO...WHILE THE ECMWF WARMS
THINGS TO 1 TO 5 DEGREES C ABOVE ZERO BY 00Z TUESDAY.  TOOK THE
MIDDLE OF THE ROAD APPROACH FRO NOW...AND STUCK WITH CONSENSUS
NUMBERS.  MODELS SHOW A VOLATILE PATTERN SETTING UP FOR MONDAY
THROUGH WEDNESDAY NEXT WEEK WITH DIFFERENT SOLUTIONS ON THE AMOUNT
OF WARMING.  THERE ARE HINTS THAT COOLER AIR MAY TRY TO FILTER INTO
THE REGION ON TUESDAY INTO WEDNESDAY...WITH THE FLOW BECOMING
NORTHEAST TO EAST.  WITH GUIDANCE TEMPERATURES WARMER THAN 925 HPA
MIXOUT...HAVE COOLED HIGHS ON WEDNESDAY.  IF THERE IS A FAIR AMOUNT
OF CLOUDS IN THE EAST...IT IS POSSIBLE NUMBERS MAY BE CLOSER TO CONS
RAW/ECMWF WHICH WOULD SUGGEST NEED TO TAKE ANOTHER 3-6 DEGREES OFF
HIGHS.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1133 AM CST THU FEB 11 2016

THE PRIMARY NEAR TERM CONCERN IS WHEN SNOW WILL START AT THE TAF
SITES THIS AFTERNOON. ALL HIRES MODELS AND SATURATION PROFILES ARE
STILL SHOWING SNOW TO WORK ITS WAY FROM NORTHWEST TO SOUTHEAST AS
THE AFTERNOON PROGRESSES...AND TIMED THE BEGINNING OF THE SNOWFALL
IN THE TAF SITES BASED ON THE SATURATION OF THE 850-700MB LAYER...
WHICH BY THE WAY IS CURRENTLY STILL FAIRLY DRY. BUT WHEN THE
SNOWFALL DOES START...AM EXPECTING IFR VISIBILITIES BASED ON WHAT
IS UPSTREAM IN CENTRAL AND NORTHERN SD. THE SYSTEM RAPIDLY EXITS
EARLY THIS EVENING THROUGH NORTHWEST IOWA...AND THAT WILL END THE
SNOWFALL BUT LOWER END MVFR TO UPPER END IFR CEILINGS WILL LIKELY
LINGER. DRIER AIR WILL THEN ADVECT SOUTHWARD VERY LATE TONIGHT AND
FRIDAY MORNING PRODUCING VFR CONDITIONS FROM NORTH TO SOUTH.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

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



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