Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 012056
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
356 PM CDT MON SEP 1 2014

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 355 PM CDT MON SEP 1 2014

AS OF 20Z...COLD FRONT HAD WORKED ITS WAY EAST TO JUST WEST OF
MARSHALL MN TO SIOUX FALLS SD TO JUST WEST OF SIOUX CITY. EXPECT
DEEP CONVECTION TO BE FOCUSED ALONG AND EAST OF THE BOUNDARY. HAVE
ADJUSTED THE HWO TO FOCUS ON THE HIGHWAY 60 AND EAST
CORRIDOR...WHERE STORMS ARE EXPECTED TO DEVELOP AROUND 22Z WITH THE
POTENTIAL FOR LARGE HAIL...DAMAGING WINDS AND ISOLATE TORNADOES.
WITH NEAR SURFACE LAYER FLOW BECOMING SOUTHWEST...STILL NOT A TON OF
DIRECTIONAL SHEAR...BUT STILL SOME DECENT SPEED SHEAR TO AID IN
STORM ORGANIZATION.  BETTER BACKED FLOW FURTHER TO THE SOUTH ALONG
THE I-80 CORRIDOR IN WESTERN AND CENTRAL IOWA AIDING IN BETTER
FELICITY. DO NOT EXPECT THIS BOUNDARY TO WORK MUCH FURTHER NORTH
THAN HIGHWAY 30 SOUTH OF OUR FORECAST AREA...THEREFORE...MAIN SEVERE
WEATHER THREATS SHOULD BE PRIMARILY WIND AND HAIL DRIVEN FOR THE
EASTERN PORTIONS OF OUR FORECAST AREA.  WITH AFOREMENTIONED SPEED
SHEAR AND CAPE VALUES AROUND 1500-2000 J/KG AND MINIMAL CAP...EXPECT
STORMS TO DEVELOP AS SHORTWAVE LIFTING FROM SOUTHEAST AIDS IN UPPER
LEVEL SUPPORT AND LIFT.

EXPECT SEVERE THREAT TO SHIFT EAST OF THE AREA AFTER 03Z.  STILL MAY
HAVE SOME POST FRONTAL SHOWERS SHIFT THROUGH THE AREA OVERNIGHT.

COOLER AND DRIER CONDITIONS ARE EXPECTED ON MONDAY...WITH NEAR
NORMAL HIGHS IN THE MID AND UPPER 70S.  FAST MOVING SHORT WAVE
APPROACHING FROM THE WEST MAY GENERATE A FEW LATE AFTERNOON
THUNDERSTORMS ACROSS CENTRAL SOUTH DAKOTA...BUT SHOULD REMAIN BELOW
SEVERE LIMITS WITH LIMITED AMOUNTS OF MOISTURE AND INSTABILITY.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 355 PM CDT MON SEP 1 2014

MID LEVEL WARM AIR ADVECTION DEVELOPS TUESDAY NIGHT...ALLOWING
CLOUDS TO INCREASE FROM THE SOUTH OVERNIGHT. COULD SEE ENOUGH WEAK
CONVERGENCE TO TRIGGER SOME ISOLATED SHOWERS AND PERHAPS A FEW
RUMBLES OF THUNDER ACROSS OUR WESTERN AND NORTHERN FORECAST
AREA...MAINLY LATE AT NIGHT INTO WEDNESDAY MORNING AS THE LOW LEVEL
JET NOSES INTO SOUTH CENTRAL SOUTH DAKOTA AND A WEAK MID LEVEL
IMPULSE LIFTS NORTHEAST INTO THE AREA. WITH SOME DECENT WARMING AND
BREEZY SOUTHERLY WINDS DOMINATING WEDNESDAY...TEMPERATURES WILL WARM
SIGNIFICANTLY IN OUR WEST...APPROACHING HIGHS NEAR 90. FURTHER
EAST...TEMPERATURES WILL ALSO IMPROVE IMPROVE INTO THE MID TO UPPER
80S...BUT COULD BE TEMPERED SOME BY RESIDUAL MID LEVEL CLOUDS INTO
THE AFTERNOON HOURS.

SURFACE LOW DEEPENS OVER THE CENTRAL DAKOTAS WEDNESDAY NIGHT AND
LIFTS INTO NORTHERN MINNESOTA THURSDAY AFTERNOON AS AN UPPER TROUGH
SKIMS THE NORTH DAKOTA AND CANADIAN BORDER. ISOLATED WARM AIR
ADVECTION SHOWERS AND THUNDERSTORMS WILL AGAIN BE POSSIBLE ACROSS
OUR NORTHEASTERN HALF...MAINLY IN THE LATE AFTERNOON AND EVENING ON
WEDNESDAY. A COLD FRONT TRACKS EAST ACROSS THE FORECAST AREA DURING
THE DAY ON THURSDAY...BRINGING ANOTHER CHANCE OF SHOWERS AND
THUNDERSTORMS ALONG WITH THE FRONT...MAINLY IN THE EVENING ACROSS
NORTHWEST IOWA AND ADJACENT COUNTIES. STILL QUITE A BIT OF
UNCERTAINTY IN THE TIMING AND LOCATION OF THIS FRONT...WITH THE GEM
DROPPING THE FRONT MUCH FURTHER SOUTH THAN THE OTHER
MODELS...AND WELL AWAY FROM THE FORECAST AREA ON THURSDAY.

SURFACE RIDGE EXPANDS INTO THE REGION FRIDAY THROUGH
SUNDAY...LEADING TO SOME PLEASANT...COOL AND DRY WEATHER CONDITIONS.
HIGHS WILL DROP WELL BELOW NORMAL...ONLY TOPPING OUT IN THE UPPER
60S AND LOWER 70S ON FRIDAY AND SATURDAY...AND IMPROVING A FEW
DEGREES ON SUNDAY. MODELS DIVERGE SIGNFICANTLY EARLY NEXT
WEEK...WITH THE GFS DEVELOPING SOME STRONG WARM AIR ADVECTION INTO
WESTERN AND CENTRAL SOUTH DAKOTA AND SOME SCATTERED SHOWERS AND
THUNDERSTORMS AS EARLY AS SUNDAY NIGHT. CONFIDENCE REMAINS LOW
HOWEVER...GIVEN THE MUCH DRIER PATTERN SEEN IN THE ECMWF.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1232 PM CDT MON SEP 1 2014

FOCUS THIS SET OF TAFS WAS THE CONVECTION THAT IS EXPECTED TO
DEVELOP ACROSS WEST CENTRAL SOUTH DAKOTA THIS AFTERNOON...AND
SPREAD EAST OVERNIGHT. HAVE ADDED HIGH BASED SHOWERS TO THE
FORECAST..THOUGH LIMITED INSTABILITY MAY LEAD TO A RUMBLE OF
THUNDER OR TWO AT TAF SITES. WESTERLY FLOW PREVAILS THROUGH THE
PERIOD...GENERALLY REMAINLY AT OR BELOW 10 KNOTS.


&&

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

$$

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


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