Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 242342
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
542 PM CST WED DEC 24 2014

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 330 PM CST WED DEC 24 2014

ANOTHER DAY OF STRATUS...MIXED AT TIMES WITH FOG/FREEZING
DRIZZLE/FLURRIES. CLEARING LINE CURRENTLY MAKING STEADY PROGRESS
THROUGH THE WESTERN/SOUTHWESTERN FORECAST AREA...AND EXPECT THIS
TREND TO CONTINUE...FOR A LITTLE WHILE. LATEST RAP/HRRR CLOUD BASE
FORECASTS HALT THE CLEARING LINE NEAR A HURON-SALEM-SIOUX CITY LINE
THIS EVENING...THOUGH THE COVERAGE OF THE LOWER CLOUD BASES DO SEEM
TO BECOME SPOTTIER WITH TIME...POTENTIALLY INDICATING AT LEAST SOME
SCATTERING OR THINNING OF THE STRATUS DECK. AT ANY RATE...LOOKS TO
BE A FAIRLY CLOUDY NIGHT FOR NORTHERN AND EASTERN PORTIONS OF THE
FORECAST AREA...WITH MOSTLY CLOUDY CONDITIONS IN THE SOUTHWEST AS
WELL...AS MID-HIGH CLOUDS SPREAD ACROSS THE AREA.

ON THE PRECIPITATION FRONT...HAVE SEEN IMPROVEMENT IN EXPANSE OF
RADAR RETURNS ON THE KFSD 88D...WHICH WERE INDICATIVE OF STEADIER
FLURRIES/FREEZING DRIZZLE THROUGH MUCH OF THE MORNING AND EARLIER
THIS AFTERNOON. THUS HAVE OPTED TO NOT CARRY ANY MENTION OF THIS
LIGHT PRECIPITATION INTO THE NEW FORECAST...THOUGH DO HAVE IT IN THE
GRIDS THROUGH THE BALANCE OF THE AFTERNOON. WITH THE EXPECTED CLOUD
COVER AND LIGHT SOUTHERLY FLOW OVERNIGHT...TEMPERATURES SHOULD HOLD
IN THE LOWER TO MID 20S FOR LOWS.

ATTENTION THEN TURNS TO APPROACHING WAVE WHICH WILL BRING BAND OF
SNOW TO PARTS OF THE AREA BEGINNING CHRISTMAS DAY IN NORTHERN PARTS
OF THE AREA. MID LEVEL SATURATION DEEPENS THROUGHOUT TONIGHT...BUT
FORECAST SOUNDINGS MAINTAIN DRY LAYER BELOW 800MB THROUGH AT LEAST
12Z...SO WILL LEAVE THE FORECAST AREA DRY THROUGH TONIGHT. EVEN
THROUGH THE MORNING...LIFT ON 295K ISENTROPIC SURFACE IS PRETTY
WEAK...SO ONLY LOW POPS WORKING INTO OUR FAR NORTH BY MIDDAY. LIFT
REALLY BEGINS TO INCREASE ACROSS THE NORTHWEST THIRD OF THE AREA
THROUGH THE AFTERNOON...AS MID LEVEL THERMAL GRADIENT BEGINS TO
TIGHTEN AND ISENTROPIC FLOW SHIFTS AROUND TO SOUTH-SOUTHEAST AHEAD
OF THE TROUGH. THUS HAVE POPS RAMPING UP TO LIKELY NORTHWEST OF A
BURKE-MITCHELL-BROOKINGS LINE BY THE END OF THE DAY...WITH AREAS
AROUND CHAMBERLAIN-HURON HAVING THE BEST CHANCE OF SEEING A HALF
INCH OR A LITTLE MORE PRIOR TO 00Z. TEMPERATURES A LITTLE TRICKY
GIVEN SOME LINGERING UNCERTAINTY IN STRATUS COVERAGE. IN GENERAL
EXPECT READINGS TO BE HIGHER THAN TODAY...WITH MOST AREAS WARMING
INTO THE 30S.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 330 PM CST WED DEC 24 2014

ACTIVE FORECAST WITH SNOW EVENT FRIDAY INTO SATURDAY AND COOL DOWN
EXPECTED NEXT WEEK. DEEP TROUGH ACROSS THE DESERT SOUTHWEST  BREAKS
DOWN AND COMES OUT IN A SERIES OF WAVES. FIRST UPPER WAVE IS
EXPECTED TO IMPACT THE AREA THURSDAY NIGHT.  AS THE WAVE SHEARS
NORTHEAST...EXPECT FRONTAL BAND TO DEVELOP EXTENDING FROM SOUTH
CENTRAL SOUTH DAKOTA INTO NORTHEAST SOUTH DAKOTA INTO WESTERN
MINNESOTA. 700 MB FRONTOGENETIC FORCING LIFTS NORTH AND EAST ONLY
PROVIDE A GLANCING BLOW ACROSS THE NORTHEAST HALF OF THE FORECAST
AREA.  HOWEVER...THE SOUTHERN PORTIONS OF THE FORECAST AREA DOES NOT
MISS OUT ENTIRELY AS THE FIRST WAVE DRIVES THE 700 MB BOUNDARY SOUTH
AND EAST AS A SECOND PIECE OF ENERGY LIFTS NORTHEAST ACROSS THE
AREA.  ATMOSPHERE IS FAIRLY EFFICIENT WITH DEEP DENDRITIC LAYER
ALOFT.  HAVE INCREASED POPS ACROSS THE SOUTHEASTERN HALF OF THE
FORECAST AREA.....BUT LIKELY HAVE TO INCREASE EVEN FURTHER WITH
ADDITIONAL ITERATIONS OF THE FORECAST.  AM EXPECTING A QUICK INCH OR
TWO AS THIS WAVE LIFTS NORTHEAST.

THE WEATHER THIS WEEKEND LOOKS TO BE RELATIVELY QUIET WITH NEAR
NORMAL CONDITIONS.  THE FIRST OF A SERIES OF ARCTIC PUSHES IS
EXPECTED TO ARRIVE SUNDAY NIGHT.  AS THE ARCTIC AIR WORKS SOUTH
COULD SEE LIGHT SNOW DEVELOP AS ANY LINGERING MOISTURE IS LIFTED.
TEMPERATURES LOOK TO BE BELOW NORMAL TO CLOSER OUT 2014 INTO THE
BEGINNING OF 2015 AS TEMPERATURES CONTINUE TO TUMBLE.  FOR A PERIOD
MONDAY INTO TUESDAY...ATMOSPHERE FROM THE SURFACE TO 600 MB IS
DENDRITIC.  RAISED POPS OVER GUIDANCE ON MONDAY...BUT HAVE NOT ADDED
MENTION OF PRECIPITATION ON TUESDAY AS THERE WILL LIKELY BE VERY
LITTLE IN THE WAY OF LINGERING MOISTURE AS ARCTIC AIRMASS SPILLS
SOUTHWARD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 534 PM CST WED DEC 24 2014

THERE STILL REMAINS A GREAT DEAL OF UNCERTAINTY REGARDING CEILING
HEIGHT AND POTENTIAL FOR CLEARING THROUGH THE TAF PERIOD. MODELS
CONTINUE TO HAVE A TOUGH TIME HANDLING DEPTH AND HEIGHT OF THIS
LOW LEVEL MOISTURE. SOME CLEARING OF THE LOW STRATUS HAS DEVELOPED
WEST OF THE JAMES RIVER AND CAN BE SEEN EXPANDING ACROSS NORTHEAST
NEBRASKA. KHON AND KSUX HAVE THE BEST POTENTIAL FOR CLEARING IN
THE NEXT FEW HOURS...WHILE KFSD MAY REMAIN NEAR THE EDGE OF THE
CLEARING LINE...WITH MUCH OF NORTHWEST IOWA AND SOUTHWEST
MINNESOTA LESS LIKELY TO CLEAR. WITHIN THE LOW STRATUS...CEILINGS
WILL BE IFR AND LIFR WITH SOME PATCH FOG LOWERING VISIBILITY AS
WELL. ADDITIONAL STRATUS WILL BEGIN BUILDING INTO SOUTH CENTRAL
THROUGH EAST CENTRAL SD WITH SOME LIGHT SNOW POSSIBLE MAINLY
AFTER 18Z.

&&

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

$$

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


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