Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 150330
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
930 PM CST SUN DEC 14 2014

.UPDATE...
ISSUED AT 916 PM CST SUN DEC 14 2014

ONLY MINOR CHANGES TO THE ONGOING FORECAST FOR MONDAY. INITIAL
ROUND OF RAIN BEGINNING TO LIFT TOWARD THE SOUTHERN CWA A BIT
AHEAD OF SCHEDULE. THIS PRECIP IS ENTIRELY IN THE FORM OF RAIN.
FURTHER WEST...MODELS A BIT TOO FAR EAST WITH THE WARM NOSE WITH A
MIXED BAG OF PRECIPITATION WEST OF THE MISSOURI RIVER.

PRECIPITATION SHOULD REALLY BEGIN TO BLOSSOM PRIOR TO DAYBREAK AS
STRONG DYNAMIC FORCING BEGINS TO MOVE INTO THE AREA. 00Z NAM AND
LATEST RAP CONTINUE TO SNOW TEMPERATURES HOLDING NEAR OR SLIGHTLY
ABOVE FREEZING THROUGH MID-DAY FROM SIOUX FALLS AND POINTS
SOUTHEAST WHICH COULD MITIGATE THE FREEZING RAIN RISK. POINTS
FURTHER NORTH STILL STAND THE HIGHEST RISK FOR A FEW HOURS OF
ACCUMULATING ICE...WITH TEMPERATURES BETWEEN 30-32 DEGREES.
SOUNDINGS ALSO TRENDING TOWARDS A FAIRLY NARROW AND RAPID
TRANSITION ZONE FROM RAIN TO SLEET TO MODERATE SNOW AROUND MID-DAY
IN THE I-29 CORRIDOR. WITH THE NAM/RAP SUGGESTING A SLIGHT
SOUTHWARD WOBBLE TO THE SYSTEM...HAVE LOWERED SNOW AMOUNTS IN
HURON SLIGHTLY AND RAISED AMOUNTS IN SE SD...SW MN...AND FAR NW IA
SLIGHTLY. THE NARROW AXIS OF A WEAK TROWAL WILL DRAG ACROSS THE
CWA INTO THE EVENING HOURS EXTENDING LIGHT SNOW TOWARD MIDNIGHT...BUT
THE IMPACTS OF WET AND WARMED GROUND ON ACCUMULATED SNOW AMOUNTS
OVER THE SOUTHEASTERN CWA REMAIN IN QUESTION.

GIVEN A SLIGHT BUMP IN SNOW FURTHER SOUTH...WILL ADD LINCOLN AND
LYON COUNTIES TO THE ADVISORY WHERE SNOW TOTALS MAY PUSH THE 3
INCH MARK.

&&

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 248 PM CST SUN DEC 14 2014

LARGE...MOIST ALMOST SPRING LIKE SYSTEM REALLY GETTING WRAPPED UP
THIS AFTERNOON IN NORTH TEXAS. AT THE SURFACE THE COLD FRONT HAS
WORKED ACROSS MOST OF SOUTH DAKOTA AND WAS APPROACHING SIOUX FALLS
AT 2030Z. STARTING TO BECOME CONCERNED THAT THIS SURGE EAST OF THE
LOW LEVEL COLD AIR AND THE VERY WOUND UP NATURE OF THE UPPER LOW
WILL BRING A BIGGER THREAT FOR FREEZING PRECIPITATION THAN
PREVIOUSLY THOUGHT. LATEST TREND IN THE 18Z NAM HINTS THAT THIS
MAY BE THE CASE AS THE WARM LAYER ALOFT STILL IN PLACE THROUGH 18Z
OVER MUCH OF SOUTHWEST MINNESOTA AND FAR EASTERN SD. THIS
CONTINUES TO LOOK LIKE THE FOCAL POINT WHERE THE WARM MOIST AIR
ALOFT WRAPS BACK FROM THE NORTHEAST OVER THE TOP OF THE COLDER AIR
AT THE SURFACE. WILL OPT FOR A WARNING OVER A HANDFUL OF COUNTIES
IN THIS AREA AS ICING POTENTIAL LOOKS TO BE ABOUT 2 TENTHS OF AN
INCH...AND POSSIBLY A LITTLE MORE...COUPLED WITH THE LIKELIHOOD OF
2 TO 3 INCHES OF SNOW IN THE AFTERNOON AND EVENING AND NORTH WINDS
LIKELY GUSTING TO ABOUT 35 TO 40 MPH. STILL SOME HOPE THAT SURFACE
TEMPERATURES DOWN THE INTERSTATE 29 CORRIDOR COULD STAY JUST A
TOUCH ABOVE FREEZING BUT THAT HOPE IS BEGINNING TO DWINDLE A BIT
AS THIS COLDER AIR SURGES EAST TODAY AND THE WARM LAYER ALOFT
STAYS IN PLACE A BIT LONGER.

ANOTHER AREA OF CONCERN WILL BE OVER PARTS OF SOUTH CENTRAL SOUTH
DAKOTA WHERE THE INITIAL SURGE OF THE COLD FRONT ALOFT/PV ANOMALY SWINGS
NORTH TONIGHT AND REALLY LOOKS TO INTERACT NICELY WITH THE LOW
LEVEL THERMAL GRADIENT THAT IS DEVELOPING RIGHT NOW. MODELS IN
VERY GOOD AGREEMENT WITH OVERALL PRECIPITATION AMOUNTS WITH ONLY
THE ECMWF A LITTLE FARTHER SOUTH ON THE LOCATION OF THE HEAVIEST
PRECIPITATION. SINCE THE ECMWF DYNAMICS ARE IN FAIRLY CLOSE
ALIGNMENT WITH THE OTHER MODELS WILL KEEP AXIS OF HIGHEST
PRECIPITATION PRETTY CLOSE TO PREVIOUS FORECAST.

ON A SIDE NOTE NOT OUT OF THE QUESTION TO HEAR A RUMBLE OF THUNDER
NEAR SIOUX CITY INTO PARTS OF NORTHWEST IOWA AS SOUNDINGS HINTING AT
JUST A TOUCH OF ELEVATED INSTABILITY EARLY THIS EVENING.

AS THE WAVE SHIFTS EAST ON MONDAY THE TROWAL COLLAPSES AND THE
MAJOR THREAT FOR ICING WILL END. EXPECTING MAINLY A BRIEF ONE TO
TWO HOUR TRANSITION WINDOW FROM RAIN TO MINOR ICING TO SNOW OVER
THE REMAINDER OF SOUTHEAST SD INTO NORTHWEST IOWA. THE SNOW WILL
THEN BUILD INTO THE AREA WITH THE HEAVIEST AMOUNTS FROM ABOUT LAKE
ANDES TO BROOKINGS. OTHER THAN CHARLES MIX AND GREGORY COUNTIES
AREAS TO THE NORTH WILL SEE SOMETHING CLOSER TO 3 TO 5 INCHES.

.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 248 PM CST SUN DEC 14 2014

RELATIVELY QUIET PERIOD IN THE EXTENDED AS EARLY WEEK SYSTEM LIFTS
TO THE NORTHEAST AND SECOND SYSTEM DIVES INTO THE GREAT LAKES
REGION. THIS SYSTEM REMAINS CUT OFF FROM THE JET STREAM WHICH IS
CONCENTRATED ACROSS THE SOUTHERN US...SO SYSTEM IS RELATIVELY SLOW
TO MOVE.  AS THE PATTERN GRADUALLY EVOLVES...EXPECT UPPER LEVEL
RIDGE TO BUILD ACROSS THE NORTH PLAINS LATE IN THE WEEK.  MODELS
HAVE COME INTO BETTER AGREEMENT ON LATE WEEK SYSTEM AS ENERGY
REMAINS CONCENTRATED SOUTH OF THE FORECAST AREA UNDER THE JET. AS
SUCH...HAVE A DRY FORECAST THROUGH THE PERIOD. IN
GENERAL...TEMPERATURES APPEAR TO BE FAIRLY SEASONAL...WITH THE
COOLEST TEMPERATURES TUESDAY NIGHT AS WEAK SURFACE RIDGE BUILDS
INTO THE AREA FROM THE NORTH. THEREAFTER...A GRADUAL WARMING TREND
IS EXPECTED THROUGH THE WEEKEND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 532 PM CST SUN DEC 14 2014

LIGHT RAIN WILL CONTINUE TO DEVELOP ACROSS THE AREA THROUGH THE
EVENING...THEN TRANSITION TO A WINTRY MIX WEST OF THE INTERSTATE
29 CORRIDOR AFTER 06Z. THE TRANSITION TO WINTRY MIX...AND
EVENTUALLY TO ALL SNOW...WILL SPREAD EASTWARD THROUGH THE MORNING
AND AFTERNOON ON MONDAY...NOT REACHING PORTIONS OF NORTHWEST IOWA
UNTIL LATE AFTERNOON.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY FROM 4 AM TO 6 PM CST MONDAY FOR SDZ039-
     053-054-059-060-065-068.

     WINTER STORM WARNING FROM 8 AM TO 6 PM CST MONDAY FOR SDZ040-056.

     WINTER WEATHER ADVISORY FROM 8 AM TO 6 PM CST MONDAY FOR SDZ055-
     061-062-066-067-069.

     WINTER WEATHER ADVISORY UNTIL 6 PM CST MONDAY FOR SDZ052-057-058-
     064.

     WINTER STORM WARNING UNTIL 6 PM CST MONDAY FOR SDZ050-063.

MN...WINTER STORM WARNING FROM 8 AM TO 6 PM CST MONDAY FOR MNZ071-072-
     080-097.

     WINTER WEATHER ADVISORY FROM 8 AM TO 6 PM CST MONDAY FOR MNZ081-
     089-098.

IA...WINTER WEATHER ADVISORY FROM 8 AM TO 6 PM CST MONDAY FOR IAZ001.

NE...NONE.
&&

$$

UPDATE...DUX
SHORT TERM...08
LONG TERM...
AVIATION...JM



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