Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 251000
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
400 AM CST WED FEB 25 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 358 AM CST WED FEB 25 2015

POTENT AND FAST MOVING WAVE NOW MOVING INTO NORTH CENTRAL SOUTH
DAKOTA AND WILL DIVE SOUTHEAST THROUGH THE FORECAST AREA THROUGH
THIS AFTERNOON. BAND OF LIGHT TO MODERATE SNOWFALL AHEAD OF THE WAVE
CONTINUES TO SPREAD ACROSS OUR NORTHERN COUNTIES...BUT IS RUNNING
INTO SOME INITIALLY DRIER LOW LEVELS AS IT APPROACHES SOUTHWEST
MINNESOTA AND AREAS SOUTH OF INTERSTATE 90. EXPECT THAT AS THE WAVE
NEARS...DEWPOINT DEPRESSIONS WILL ERODE AND SNOW WILL WILL QUICKLY
BECOME WIDESPREAD. LATEST GUIDANCE CONTINUES WITH A SLIGHTLY MORE
NORTHEASTERN TRACK TO THE WAVE...WHICH IS SUPPORTED BY THE MORE
NORTHERLY THERMAL GRADIENT AS WELL AS RECENT RADAR/SATELLITE TRENDS.

LATER THIS MORNING AS THE WAVE SWINGS INTO OUR EASTERN FORECAST
AREA...850 MB FRONTOGENESIS BECOMES BETTER ORGANIZED ACROSS
SOUTHWEST MINNESOTA AND NORTHWEST IOWA...COINCIDENT WITH GREATER DIV-
Q SINKING INTO NORTHWEST IOWA. THIS SHOULD ALLOW FOR BETTER
ORGANIZATION OF THE SNOW BAND IN OUR EASTERN COUNTIES. BUT WITH A
MORE NORTHERLY TRACK TO THIS SYSTEM...IT DOES APPEAR THAT THE
MISSOURI VALLEY AND SOUTH CENTRAL SD WILL SEE THE LEAST SNOWFALL -
CLOSER TO AN INCH. DID TRIM BACK POPS AND AMOUNTS IN THESE AREAS.
HIGHEST AMOUNTS WILL BE ACROSS THE IOWA GREAT LAKES INTO THE I90
CORRIDOR OF SOUTHWEST MINNESOTA WHERE 5 TO 7 INCHES SEEM REASONABLE.
CANNOT RULE OUT A FEW LOCALLY HIGHER AMOUNTS IN THIS
AREA...ESPECIALLY IN THE IOWA LAKES WHERE OUR WINTER STORM WARNING
REMAINS IN EFFECT. OVERALL HEADLINES LOOK IN GOOD SHAPE...AND WHILE
THE KSUX AREA AMOUNTS WERE LOWERED A BIT TO AROUND 1 TO 3
INCHES...WILL LEAVE THEM IN THE ADVISORY GIVEN THE EXPECTATION OF A
MESSY COMMUTE. SIOUX FALLS STILL LOOKS SET FOR AROUND 4 INCHES OF
ACCUMULATIONS.

TEMPERATURES WILL CONTINUE TO SLOWLY FALL THROUGH THE DAY TODAY. BY
MIDDAY...TEMPERATURES WILL GENERALLY BE IN THE TEENS OR NEAR 20.
EAST NORTHEAST WINDS THIS MORNING TURN MORE NORTHERLY IN THE
AFTERNOON AND INCREASE TO 15 TO 25 MPH. WHILE SOME LOCALIZED
DRIFTING OF SNOW IS POSSIBLE...BUT WILL LEAVE OUT BLOWING SNOW
MENTION IN THE FORECAST. VISIBILITIES WILL DROP IN THE BANDS OF
SNOW...BUT WILL GENERALLY BE GREATER THAN A MILE.

SNOW TAPERS OFF FROM WEST TO EAST THIS AFTERNOON AND SHOULD
COMPLETELY EXIT THE FORECAST AREA BY SUNSET. ARCTIC HIGH PRESSURE
BEGINS BUILDING INTO THE NORTHERN PLAINS LATE TONIGHT AND SKIES WILL
START CLEARING TOWARDS DAYBREAK. TEMPERATURES WILL DROP INTO THE
SINGLE DIGITS BELOW ZERO WHICH COMBINED WITH NORTHERLY WINDS AROUND
10 TO 15 MPH WILL PRODUCE WIND CHILLS OF 20 TO 30 BELOW ZERO. WILL
LIKELY NEED A WIND CHILL HEADLINE...BUT WITH THE ONGOING WINTER
WEATHER HEADLINES...WILL HOLD OFF ISSUING FOR WIND CHILLS FOR NOW.

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 358 AM CST WED FEB 25 2015

IN THE WAKE OF THE SNOW PRODUCING SYSTEM TODAY...THE MAIN FEATURE
OF THE WEATHER FOR THE END OF THE WORK WEEK WILL BE THE EXTREME
COLD. WILL MOST CERTAINLY BE DEALING WITH ADVISORY LEVEL WIND
CHILLS THROUGH AT LEAST MIDDAY THURSDAY...IF NOT FOR THE ENTIRE
DAY IN SOME LOCATIONS EAST OF I 29. AS MENTIONED BEFORE...WILL NOT
ISSUE THIS COLD HIGHLIGHT UNTIL SNOW DRIVEN HEADLINES ARE WINDING
DOWN. LOCATIONS WITH FRESH SNOWCOVER AND -20 TO -22C 925 HPA TEMPS
ALONG WITH FIGHTING COLD AIR ADVECTION THROUGH THE DAY MAY NOT
SEE ACTUAL TEMPS GET ABOVE ZERO. SEVERAL LOCATIONS WILL BE AROUND
RECORD COLD MAXIMUM VALUES FOR THE DAY. COULD BE SOME SHALLOW
STRATOCUMULUS ALMOST ANYWHERE EAST OF THE JAMES...BUT MORE
SUNSHINE EXPECTED THAN CLOUDS...AND PROBABLY JUST A BIT TOO COLD
AND SUBSIDENT FOR ANY EFFECTIVE FLURRY DEVELOPMENT. ON THURSDAY
NIGHT...SURFACE RIDGE BUILDS OVER WITH WINDS DIMINISHING QUICKLY
IN THE EVENING...AND ALMOST CERTAIN TO BE QUITE CLEAR. HAVE
FACTORED IN THE EXPECTED NEW SNOW COVER AND DROPPED LOWS QUITE A
BIT NORTHEAST TWO THIRDS...WHILE ALLOWING FOR LESS COOLING IN THE
SOUTHWESTERN CWA...WHICH WILL EVEN PICK UP A TAD OF SOUTHERLY FLOW
LATE. EVEN A PUFF OF WIND...WHICH WILL BE MORE FAVORED IN THE
EASTERN HALF OF THE CWA...WILL DRIVE WIND CHILLS AGAIN EASILY INTO
THE ADVISORY RANGE. ON FRIDAY...FLOW TURNS TO THE SOUTH AND
SOUTHWEST AS ARCTIC HIGH SPREADS EASTWARD...BUT WARMING WILL BE
SIGNIFICANTLY CHALLENGED BY ALBEDO AND STABILIZING THERMAL
PROFILE...SO AGAIN TRIMMED EASTERN AREAS DOWN QUITE A BIT AGAINST
WARMER GUIDANCE.

PUSH OF WARM AIR ADVECTION FRIDAY NIGHT INTO SATURDAY...STRUGGLING
AGAINST THE RETREAT OF THE DRIER LOW LEVEL TRAJECTORY. LIKELY TO
GET AN INCREASE IN MID LEVEL CLOUDS ON FRIDAY NIGHT AND EARLY
SATURDAY...THEN SURGE OF SOME LOWER CLOUDS TOWARD THE SOUTHERN CWA
AS SOUTHERLY JET INCREASES THROUGH THE DAY SATURDAY. TEMPS WILL
MODERATE...BUT ONLY TO THE UPPER TEENS AND 20S...AND WILL NOT EVEN
FEEL THAT WARM WITH THE GREATER DEGREE OF CLOUDS AND SOUTHERLY
WIND. KEPT A MINIMAL MENTION FOR LIGHT SNOW DURING THE AFTERNOON
ACROSS THE SOUTHEASTERN THIRD OF THE CWA WITH WEAK LEADING WAVE
PASSING THROUGH CONFLUENCE ZONE. INFLUENCE OF NORTHERN STREAM
WILL LIKELY EXERT A DRYING INFLUENCE ON NORTHERN EDGE OF THE
PRECIPITATION THREAT THROUGH EARLY SUNDAY...LIMITING TO PERHAPS
A LIGHT DUSTING OF MEASURABLE SNOWFALL FOR ONLY THE SOUTHEASTERN
CWA.

THE LARGER SCALE PATTERN KEEPS THE AREA NEAR THE NORTHERN/SOUTHERN
STREAM CONFLUENCE FROM THE WEEKEND INTO EARLY NEXT WEEK. MOST
SOLUTIONS AND ENSEMBLES GIVE THE SOUTHERN STREAM A BIT MORE
INFLUENCE BY LATER MONDAY AND INTO TUESDAY...WITH GFS MOST BULLISH
OF THE SET. EACH DEVELOP A FAIRLY DECENT WAVE ACROSS THE CENTRAL
PLAINS WITH FSD CWA ON THE NORTHWEST EDGE OF DECENT PRECIPITATION
SHIELD WITH THE SYSTEM.  ENOUGH STATISTICAL SUPPORT TO RAISE POPS
10 TO 20 PERCENT FOR THE SOUTHEASTERN HALF OF THE AREA BOTH MONDAY
NIGHT AND TUESDAY...AND WILL HAVE TO WATCH THIS SYSTEM EVOLVE OVER
THE NEXT FEW DAYS AS MODELS STRUGGLE WITH THE TIMING AND INTENSITY
OF WAVES IN THE SPLIT FLOW. TEMPS CERTAINLY SHOULD NOT ECLIPSE
NORMALS THROUGH THE PERIOD.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1059 PM CST TUE FEB 24 2015

SNOW IN DEVELOPING STAGES ACROSS OUR SD COUNTIES AT THE START OF
THIS TAF PERIOD...AND EXPECTED TO INCREASE IN COVERAGE/INTENSITY
FAIRLY RAPIDLY...REACHING EASTERN EDGE OF THE FORECAST AREA AROUND
US HIGHWAY 71 THROUGH DAYBREAK. CONFIDENCE IN A PERIOD OF LIFR
VISIBILITY HAS BEEN INCREASING FOR KHON/KFSD TAF LOCATIONS...
ESPECIALLY IMPACTING THE MORNING FLIGHTS AROUND DAYBREAK AT KFSD.
VISIBILITY SHOULD TREND UPWARD IN THE LATE AFTERNOON WEDNESDAY
THOUGH LINGERING MVFR CEILINGS ARE ANTICIPATED...WITH IMPROVEMENT
TO VFR POSSIBLE TOWARD EVENING.

WINDS BEGIN EASTERLY IN THE 10 TO 15 KT RANGE. HOWEVER AS THE
SYSTEM SHIFTS EAST AND WINDS SWING AROUND TO THE NORTH IN THE LATE
MORNING/AFTERNOON...SPEEDS WILL INCREASE WITH GUSTS TO AROUND
25KTS LIKELY. THIS MAY PRODUCE LINGERING POCKETS OF MVFR
VISIBILITY IN BLOWING SNOW IF FALLING LIGHT SNOW IS STILL AROUND.
POTENTIAL FOR BLOWING SNOW SHOULD DIMINISH AS THE FALLING SNOW
ENDS...THOUGH DRIFTING STILL LIKELY WITH THE GUSTY WINDS INTO THE
EVENING.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR SDZ039-
     040-055-056-062-067-071.

MN...WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR MNZ071-
     072-080-081-089-090-097-098.

IA...WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR IAZ001-
     002-012-013-020-021-031-032.

     WINTER STORM WARNING UNTIL 6 PM CST THIS EVENING FOR IAZ003-014-
     022.

NE...WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR NEZ014.

&&

$$

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


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