Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 141147
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
547 AM CST SUN DEC 14 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 237 PM CST SAT DEC 13 2014

THE MAIN CHALLENGES AGAIN TONIGHT ARE FOR STRATUS AND FOG. SOUNDINGS
SUPPORTING DEEPER LOW LEVEL MOISTURE COUPLED WITH A BIT OF
INSTABILITY AT THE TOP OF THE MOIST LAYER. SUSPECT THAT THIS WILL
LEAD TOWARDS MORE WIDESPREAD DRIZZLE AND FOG OVERNIGHT INTO SUNDAY
MORNING. WILL ISSUE A RELATIVELY SMALL DENSE FOG ADVISORY IN FAVORED
SPOT BUT IF THE FOG AND DRIZZLE DOES DEVELOP IT HAS A CHANCE TO
BECOME A BIT MORE WIDESPREAD AS SOUNDINGS A FAIRLY SUPPORTIVE OVER
MUCH OF THE AREA. TEMPERATURES WILL REMAIN VERY WARM OVERNIGHT WITH
LOWS FROM THE MID 40S TO LOWER 50S. IF SOME THE THE SITES IN
NORTHWEST IOWA CAN HOLD ON THROUGH MIDNIGHT TOMORROW NIGHT ABOVE
ABOUT THE MID 40S THE WILL BE SOME ALL TIME RECORD WARM LOWS SET.
SIOUX CITY HAS A DECEMBER RECORD WARM LOW OF 45 DEGREES AND THE
FORECAST FOR TONIGHT IS A LOW OF 52 BUT BY MIDNIGHT SUNDAY NIGHT
TEMPERATURES ARE EXPECTED TO GET RIGHT DOWN TO ABOUT 45 SO WILL BE
VERY CLOSE.

MOISTURE AND LIFT WILL GRADUALLY INCREASE IN THE FAR SOUTHERN CWA
SUNDAY AFTERNOON AS A STRONG LOW PRESSURE WRAPS UP ACROSS NEBRASKA.
FOR THE MOST PART PROBABLY LOOKING AT THE POTENTIAL FOR MEASURABLE
DRIZZLE THROUGH 0Z MONDAY MORESO THAN RAIN. THE COOLER AIR WILL
BEGIN TO SETTLE ACROSS THE AREA SO GRADUALLY FALLING TEMPERATURES
WEST OF INTERSTATE 29. HIGHS STILL EXTREMELY MILD WITH LOWER TO MID
50S EAST OF THE JAMES RIVER VALLEY AND 40S TO THE WEST.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 237 PM CST SAT DEC 13 2014

FOCUS IN THE MEDIUM RANGE AND EXTENDED IS ON THE STORM SYSTEM
AFFECTING THE PLAINS.  IN GENERAL...MODELS HAVE SUGGESTED THAT THE
WARM AIR WILL HANG ON LONGER ACROSS THE EAST...CHANGING
PRECIPITATION TYPE AS THE VARIOUS LOBES OF ENERGY ROTATE THROUGH THE
REGION.

MODELS SHOW RELATIVELY STACKED SYSTEM HEADED INTO MONDAY AND AS
SUCH...SYSTEM SHOULD BE A RELATIVELY SLOW MOVER.  HAVE SIDED CLOSER
TO A GFS/ECMWF BLEND...WHICH SEEMS TO BE IN THE MIDDLE AMONGST THE
VARIOUS SOLUTIONS.  THE CANADIAN IS EVEN SLOWER AND WARMER...WHILE
THE NAM IS QUICKER AND COOLER. APPEARS THE COOLER AIR WILL TRY TO
SPREAD SOUTH AND EAST ACROSS THE AREA THROUGH THE DAY ON MONDAY.  AS
THERMAL PROFILES COOL...PRECIPITATION WILL TRANSITION FROM A LIQUID
TO A SOLID BUT COULD BE A SOMEWHAT MESSY TRANSITION DUE TO WARM NOSE
AROUND 800-850 MB...POTENTIALLY ALLOWING SURFACE TEMPERATURES TO
FALL BELOW FREEZING PRIOR TO TEMPS ALOFT.  THIS MAY LEAD TO A FEW
HOURS OF FREEZING RAIN OR SLEET....WITH GREATEST POTENTIAL FOR ICE
APPEARS TO BE ACROSS THE HIGHWAY 14 CORRIDOR. WITH WARMER
SOLUTIONS...HAVE CUT BACK ON SNOWFALL AMOUNTS...ESPECIALLY ACROSS
THE EAST WHERE THE WARM AIR HANGS UP CLOSE TO 00Z TUESDAY.  BY
THEN...APPEARS AS THOUGH THE WAVE AND THE DYNAMICS BEGIN TO SHIFT
NORTH AND EAST OF THE FORECAST AREA AND ANY LINGERING PRECIPITATION
WILL BE LEFT IN THE WRAP AROUND.

COLD AIR CONTINUES TO POUR INTO THE REGION MONDAY NIGHT INTO TUESDAY
MORNING AS SKIES CLEAR.  WITH 925 HPA WINDS IN THE 30-40KNOT
RANGE...WILL LIKELY BE CLOSE TO ADVISORY CRITERIA.  FOR THE TIME
BEING...WILL NOT ISSUE ANY HEADLINES FOR NOW...BUT APPEARS TO BE
MORE OF AN ADVISORY THAN WARNING EVENT WITH MORE OF THE
PRECIPITATION FALLING AS RAIN.

EXPECT SMALL DIURNAL RANGE ON TUESDAY AS AREA REMAINS LOCKED IN DEEP
NORTHWESTERLY FLOW AND DECREASING PRESSURE GRADIENT ACROSS THE AREA.

HAVE NOT CHANGED EXTENDED DUE TO ACTIVE WEATHER IN THE MID-RANGE.
IN GENERAL...APPEARS AS THOUGH TEMPERATURES WILL BE SEASONAL WITH A
CHANCE OF PRECIPITATION CREEPING BACK INTO THE FORECAST AROUND
THURSDAY AS ADDITIONAL SHORT WAVES MOVE THROUGH THE REGION.  HARD TO
SAY HOW SYSTEM WILL EVOLVE EXACTLY...AS GFS RETROGRADES MID LEVEL
ENERGY WHILE ECMWF DIGS TROUGH DOWN THE SPINE OF THE ROCKIES INTO
THE CENTRAL PLAINS. BEST CHANCES FOR PRECIPITATION APPEAR TO BE

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 547 AM CST SUN DEC 14 2014

IFR-LIFR CONDITIONS WILL DOMINATE THROUGH THE PERIOD...THOUGH
BRIEF IMPROVEMENT TO MVFR-LOW END VFR IS POSSIBLE...MAINLY IN
AREAS WEST OF THE I-29 CORRIDOR. PRIMARLY LIGHT-MODERATE DRIZZLE
AND FOG THROUGH THE DAY WILL GRADUALLY INCREASE TO BONAFIDE RAIN
SPREADING OVER THE AREA TONIGHT. LOCATIONS WEST OF I-29 WILL SEE
THE RAIN BECOME A WINTRY MIX OF FREEZING RAIN/SLEET AFTER 06Z AS
COLDER SURFACE AIR BEGINS TO UNDERCUT LINGERING WARM LAYER ALOFT.
EVENTUALLY THE MIXED PRECIPITATION WILL SWITCH TO SNOW AS LAYERS
ALOFT COOL...HOWEVER THIS NOT LIKELY TO OCCUR AT KHON UNTIL AFTER
THIS TAF PERIOD.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM CST MONDAY FOR SDZ039-
     040-053>055-059-060-065-068.

     WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM CST MONDAY
     FOR SDZ050-052-057-058-063-064.

     WINTER WEATHER ADVISORY FROM 8 AM TO 6 PM CST MONDAY FOR SDZ056-
     061-062-066-069.

MN...WINTER WEATHER ADVISORY FROM 8 AM TO 6 PM CST MONDAY FOR MNZ071-
     072-080-097-098.

     DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR MNZ089-090-
     097-098.

IA...DENSE FOG ADVISORY UNTIL 10 AM CST THIS MORNING FOR IAZ001>003-
     012>014-020>022.

NE...NONE.
&&

$$

SHORT TERM...08
LONG TERM...
AVIATION...JH


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