Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 130421
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1121 PM CDT SAT APR 12 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 332 PM CDT SAT APR 12 2014

SURFACE TROUGH IS RESIDING OVER THE EASTERN PORTIONS OF THE CWA THIS
AFTERNOON WITH A WEAK TRAILING COLD FRONT EXTENDING THROUGH OUR FAR
SOUTHEASTERN ZONES. THIS BOUNDARY WILL CONTINUE TO DROP TO THE
SOUTH...AND MODELS STILL INDICATING SOME POSSIBLE THUNDERSTORM
DEVELOPMENT IN OUR FAR SOUTHEAST DURING THE LATE AFTERNOON AND
EVENING AS A SHORTWAVE LIFTING OUT OF EASTERN NEBRASKA INTERACTS
WITH THE FRONT. EVEN SO...LOOKS LIKE MOST OF THIS ACTIVITY WILL
OCCUR TO THE SOUTH OF OUR CWA. OTHERWISE...A MORE SIGNIFICANT
BOUNDARY RESIDES THROUGH NORTHWESTERN SOUTH DAKOTA...WITH
TEMPERATURES ONLY IN THE 40S BACK THROUGH WESTERN NORTH DAKOTA
BEHIND THE SYSTEM. THIS FRONT WILL WORK TO THE SOUTH OVERNIGHT...AND
STILL EXPECTING SHOWERS TO DEVELOP IN OUR WEST LATER TONIGHT...THEN
EXPAND TO THE EAST INTO SUNDAY AS A MID LEVEL FRONT MOVES INTO THE
AREA AND FRONTOGENESIS STRENGTHENS ACROSS THE AREA. THE BETTER
POTENTIAL FOR PRECIPITATION WILL GENERALLY BE FROM THE INTERSTATE 90
CORRIDOR AND SOUTHWARD WHERE THE BETTER MID AND UPPER LEVEL SUPPORT
WILL RESIDE. THERMAL PROFILES WILL BEGIN TO COOL OVERNIGHT AND
SUNDAY IN COLD AIR ADVECTION REGIME...THROUGH MODELS HAVE COME IN
SLIGHTLY WARMER WITH LOW LEVEL TEMPERATURES THROUGH THE PERIOD...SO
THINK THAT THE SNOW POTENTIAL MAY BE A LITTLE LESS THAN PREVIOUSLY
THOUGHT. STILL COULD SEE SNOW MIX IN WITH THE RAIN ACROSS OUR NORTH
AND WEST AFTER 12Z ON SUNDAY...BUT WITH SURFACE TEMPERATURES IN THE
UPPER 30S TO LOWER 40S ON SUNDAY AFTERNOON...NOT SURE HOW MUCH OF
THAT WILL ACTUALLY REACH THE SURFACE WITHOUT MELTING.

WILL HAVE A WIDE RANGE OF TEMPERATURES ACROSS THE CWA
TONIGHT...DROPPING INTO THE MID 30S THROUGH THE NORTHERN JAMES RIVER
VALLEY...TO NEAR 50 THROUGH THE SIOUX CITY TO STORM LAKE CORRIDOR.
AS COLD AIR ADVECTION CONTINUES ON SUNDAY...TEMPERATURES WILL
CONTINUE TO SLOWLY DROP THROUGH THE MORNING HOURS OF SUNDAY...THEN A
GENERAL STEADYING OUT IN THE AFTERNOON TO UPPER 30S LOWER 40S AS
MENTIONED ABOVE.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 332 PM CDT SAT APR 12 2014

SYSTEM WORKS ITS WAY OUT OF THE AREA FAIRLY QUICKLY THROUGH THE
EVENING HOURS ON SUNDAY EVENING.  WITH COLD AIR
AROUND...PRECIPITATION SHOULD CHANGE OVER TO SNOW FAIRLY QUICKLY IF
IT HASN/T DONE SO ALREADY.  BREEZY NORTHWEST WINDS HANG ON THROUGH
THE OVERNIGHT HOURS SUNDAY NIGHT WITH STRONG COLD AIR ADVECTION AND
30 KNOTS OF FLOW AT 925 HPA.

COLD AIR ADVECTION ALOFT DIES AWAY ON MONDAY AND WINDS GRADUALLY
DECREASE THROUGH THE DAY. HOWEVER...STRONG MIXING WITH
UNIDIRECTIONAL SHEAR PROFILE WILL STILL DRAW MOMENTUM DOWN FROM
ALOFT KEEPING CONDITIONS IN THE BREEZY CATEGORY THROUGHOUT THE DAY.
DESPITE STRONG MIXING...HAVE SIDED WITH HIGHS WELL BELOW NORMAL WITH
850 HPA TEMPS IN THE -4 TO -8 RANGE.

AS FLOW TURNS SOUTHERLY ON TUESDAY...EXPECT STRONG WARMING
THROUGHOUT THE DAY AND RAISED FORECAST HIGHS CLOSE TO MIXOUT FROM
850 HPA WITH WARM FRONT LIFTING NORTH.  TEMPERED WARMING POTENTIAL A
BIT ACROSS SOUTHWEST MINNESOTA AS TIMING OF THE FRONT LATER IN THE
DAY MAY ALLOW FOR SLIGHTLY LESS WARMING.

ABOVE AVERAGE TEMPERATURES DON/T LAST HOWEVER AS A SERIES OF PHASED
WAVES MOVE INTO THE PLAINS.  ECMWF SUGGESTS THE FORECAST AREA MAY BE
CAUGHT BETWEEN THE TWO WAVES...WHILE THE GFS SUGGESTS SYSTEMS MAY
SYSTEMS MAY SLOWLY MELD INTO ONE.  BOTH THE ECMWF AND GFS SUGGEST
THIS IS A RELATIVELY SLOW SYSTEM...AND WITH THERMAL PROFILES
POTENTIAL EXISTS WITH A MIXTURE OF PRECIPITATION TYPES.  FOR
NOW...DIDN/T GET TOO FANCY WITH WEATHER TYPES BUT THE POTENTIAL
EXISTS FOR ACCUMULATING SNOW WITH THIS SYSTEM.  APPEARS AS THOUGH
THE DYNAMICS MOVE OUT OF THE AREA LATE THURSDAY NIGHT INTO
FRIDAY...SO HAVE DROPPED POPS ON SATURDAY WITH A WARMUP EXPECTED FOR
EASTER WEEKEND.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY EVENING)
ISSUED AT 1121 PM CDT SAT APR 12 2014

MVFR STRATUS IN NORTH DAKOTA/NORTHERN SOUTH DAKOTA AT THE START OF
THE PERIOD WILL SLOWLY WORK SOUTHWARD WITH PUSH OF COLDER LOW LEVEL
AIR. THIS SHOULD BRING A PERIOD OF MVFR CEILINGS TO TAF LOCATIONS...
EXPECTED TO BE MOST PROLONGED AT KSUX AND OTHER AREAS SOUTH OF I-90
WHERE CHANCE OF MORE WIDESPREAD PRECIPITATION IS GREATER THROUGH THE
DAY ON SUNDAY.

IN ADDITION TO PRECIPITATION/MVFR CEILINGS...INCREASING GUSTY NORTH
WINDS WILL CREATE AVIATION CONCERNS THROUGH THE PERIOD. FREQUENT
GUSTS ABOVE 25KT EXPECTED WEST OF INTERSTATE 29 OVERNIGHT...WITH THE
STRONGEST WINDS EXPANDING ACROSS THE FORECAST AREA EARLY SUNDAY
MORNING. BY DAYBREAK SUNDAY...GUSTS WILL FREQUENTLY TOP 30KT ACROSS
THE AREA...WITH SUSTAINED WINDS AROUND 25KT/GUSTS TO 35KT OR HIGHER
LIKELY THROUGH THE AFTERNOON. ONLY SLIGHT DECREASE IN WINDS EXPECTED
AFTER SUNSET SUNDAY EVENING.

&&

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

$$

SHORT TERM...JM
LONG TERM...
AVIATION...JH






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