Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 240929
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
429 AM CDT TUE MAR 24 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 429 AM CDT TUE MAR 24 2015

ANOTHER COMPLICATED FORECAST IN THE SHORT TERM AS TWO PHASED WAVES
SHIFT EAST ACROSS THE PLAINS TODAY.  MODELS CONTINUE TO SHOW
STRONGER UPPER LEVEL ENERGY ASSOCIATED WITH THE SOUTHERN WAVE.
SHOWERS AND THUNDERSTORMS CURRENTLY DEVELOPING ACROSS EASTERN
NEBRASKA ALONG THE LEADING EDGE OF THE UPPER WAVE.  EXPECT BAND OF
RAIN TO DEVELOP OVER THE NEXT FEW HOURS NEAR THE MISSOURI RIVER
VALLEY IN RESPONSE TO INCREASING ISENTROPIC LIFT. THE BAND OF RAIN
MAY LIFT NORTHEAST FAST ENOUGH MOVING INTO AREAS WHERE THE
TEMPERATURE IS SLIGHTLY BELOW FREEZING ACROSS NORTHWEST IOWA INTO
SOUTHWEST MINNESOTA.  EXPECT ANY LATENT HEAT RELEASE IN THE FREEZING
PROCESS TO HELP WARM THE ATMOSPHERE LEADING TO RELATIVELY SHORT
PERIOD OF FREEZING RAIN BEFORE RAIN TAKES OVER.

AS UPPER LEVEL DYNAMICS INCREASE...FORECAST SOUNDINGS WET BULB DOWN
TO BELOW FREEZING WITH ANY AIR ABOVE FREEZING BEING CONTAINED RIGHT
NEAR THE SURFACE. WITH DEW POINTS ACROSS MUCH OF IOWA IN THE UPPER
20S TO NEAR 30...AM CONCERNED ABOUT THE SNOW POTENTIAL ACROSS
EASTERN EDGE OF THE FORECAST AREA IN NORTHWEST IOWA AND SOUTHWEST
MINNESOTA.  MODEL SOUNDINGS SUGGEST A SMALL AMOUNT OF ELEVATED
INSTABILITY...SUGGESTING THE POTENTIAL FOR THUNDER SNOW AS DYNAMIC
COOLING TAKES OVER.  FOR NOW...SIDED WITH SNOW RATES AROUND AN INCH
PER HOUR...BUT CONCEIVABLY BE HIGHER IF ATMOSPHERE GOES CONVECTIVE.
WITH EXPECTATION OF ACCUMULATING SNOW THIS AFTERNOON ACROSS PORTIONS
OF NORTHWEST IOWA INTO SOUTHWEST MINNESOTA...WENT AHEAD AND ISSUED A
SMALL WINTER WEATHER ADVISORY.  CURRENTLY HAVE ONE TO THREE INCHES
OF SNOW IN THE ADVISORY AREA...BUT COULD BE HIGHER IF CONVECTIVE
SNOW DEVELOPS.

THE UPPER WAVE SHIFTS EAST FAIRLY QUICKLY THIS EVENING AND AS A
RESULT DYNAMICS WIND DOWN ACROSS THE AREA. THIS IS AHEAD OF THE COLD
FRONT ASSOCIATED WITH THE WAVE TO THE NORTH...SO THE TEMPERATURES
WARM ALOFT TO THE POINT WHERE COULD SEE LIGHT MIXED PRECIP DEVELOP
ON THE BACK EDGE OF THE PRECIPITATION SHIELD.

AS THE COLD FRONT SURGES SOUTH ACROSS THE AREA WEDNESDAY
MORNING...LIFT MAY BE STRONG ENOUGH TO PRODUCE SOME LIGHT
PRECIPITATION ALONG AND SOUTH OF I-90.  THE ATMOSPHERE AHEAD OF THE
FRONT SHOULD BE WARM ENOUGH TO SUPPORT RAIN.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 429 AM CDT TUE MAR 24 2015

NORTH NORTHWEST FLOW PATTERN SETS UP WEDNESDAY THROUGH FRIDAY IN THE
WAKE OF THE EXITING SYSTEM. COOLER TEMPERATURES SETTLE INTO THE
REGION...HOWEVER READINGS WILL BE CLOSE TO SEASONAL NORMALS. A
SLIGHT CHANCE OF LIGHT SNOW ASSOCIATED WITH MID LEVEL LIFT EXITS
NORTHWEST IOWA MONDAY MORNING...WITH DECREASING CLOUDS THROUGH THE
DAY. HIGHS WILL BE IN THE MAINLY IN THE 40S. LOWERED HIGHS IN THE
FAR EAST WHERE FRESH SNOWPACK IS EXPECTED AND HIGHS MAY ONLY REACH
40.

A PAIR OF SHORTWAVES DIVE SOUTHWARD INTO THE NORTHERN PLAINS
THURSDAY THROUGH FRIDAY NIGHT...HOWEVER MODELS ARE NOT SHOWING MUCH
AGREEMENT IN THE TRACK OF THESE WAVES. THEREFORE WILL CONTINUE TO
LEAVE THIS TIME FRAME DRY FOR NOW. A REINFORCING SHOT OF COOLER AIR
HOWEVER WILL HOLD HIGHS TO THE UPPER 30S AND 40S.

THERE IS MUCH STRONGER MODEL AGREEMENT IN NOSING THE UPPER RIDGE
INTO THE HIGH PLAINS ON SATURDAY. A STRONG PUSH OF WARM AIR
ADVECTION AND DECENT MIXING WILL IMPROVE TEMPERATURES SIGNIFICANTLY.
HIGHS WILL BE IN THE UPPER 40S TO NEAR 70. WARMEST TEMPERATURES WILL
BE IN SOUTH CENTRAL SD WHERE THE STRONGEST WARMING AND MIXING
POTENTIAL EXISTS.

GFS AND GEM BRING A COLD FRONT THROUGH THE FORECAST AREA ON SATURDAY
NIGHT...WHILE THE ECMWF LAGS BY NEARLY 24 HOURS. COULD VERY WELL SEE
RAIN SHOWERS WITH THIS WAVE...BUT CONFIDENCE IN THE TIMING IS STILL
FAIRLY LOW. DID INTRODUCE SOME SLIGHT CHANCE POPS ON SATURDAY NIGHT
WITH TWO MODELS IN AGREEMENT.


&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1111 PM CDT MON MAR 23 2015

MAINLY MID LEVEL CLOUDS WILL OVERSPREAD THE AREA THIS EVENING...
WITH CONDITIONS EXPECTED TO DETERIORATE INTO MVFR-IFR RANGE FROM
10Z-16Z AS WIDESPREAD RAIN DEVELOPS ACROSS THE REGION. AS SYSTEM
STRENGTHENS AND COOLS TEMPERATURES ALOFT...WILL LIKELY SEE RAIN
MIX WITH/CHANGE TO SNOW AS IT LIFTS TOWARD SOUTHWEST MN. COULD SEE
BRIEF PERIOD OF RAIN/SNOW MIX AT KFSD THIS AFTERNOON...WITH SOME
MODELS ALSO SHOWING THIS POTENTIAL AT KSUX. HAVE INCLUDED MENTION AT
KFSD...BUT CONFIDENCE IS LOWER AT KSUX SO DID NOT INCLUDE AT THAT
LOCATION. MORE LIKELY TO SEE SNOW FROM SOUTHWEST MN INTO THE IOWA
GREAT LAKES.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 1 AM CDT
     WEDNESDAY FOR MNZ080-081-089-090.

IA...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 1 AM CDT
     WEDNESDAY FOR IAZ002-003-013-014-021-022-032.

NE...NONE.
&&

$$

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



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