273
FXUS63 KFSD 100126
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
826 PM CDT WED SEP 9 2026
KEY MESSAGES
- SEVERE WEATHER POSSIBLE FRIDAY AFTERNOON AND EVENING.
CONFIDENCE REMAINS LOW DUE TO STRONG CAPPING POTENTIAL.
- ADDITIONAL MODERATE TO HIGH CHANCES (50-80 PERCENT) FOR
SHOWERS AND THUNDERSTORMS RETURN SATURDAY NIGHT INTO EARLY
NEXT WEEK. SEVERE RISK IS LOW.
- COOLER CONDITIONS ARRIVE THIS WEEKEND INTO EARLY NEXT WEEK
WITH OCCASIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS.
UPDATE
ISSUED AT 824 PM CDT WED SEP 9 2026
TAKING A LOOK ACROSS THE AREA, MOSTLY QUIET CONDITIONS CONTINUE THIS
EVENING AS A WEAK SURFACE HIGH PROGRESSES THROUGH THE AREA. WITH
LIGHTER SURFACE WINDS IN PLACE OVERNIGHT, CAN'T RULE OUT SOME PATCHY
FOG TO START THE MORNING MAINLY ALONG OUR WATER WAYS AND LOWER
SPOTS. HOWEVER, THIS SHOULD ERODE JUST AFTER DAYBREAK AS OUR DIURNAL
HEATING RETURNS. FROM HERE, MORE QUIET AND SEASONABLE CONDITIONS
WILL CONTINUE INTO THURSDAY AS HIGHS APPROACH THE UPPER 70S TO MID
80S FOR THE DAY. NOW THAT WE'RE OUT OF PEAK EVAPOTRANSPIRATION (ET)
AND HARVESTING HAS BEGUN, SHOULD SEE DEW POINTS DECREASE A BIT MORE
LEADING TO MORE COMFORTABLE CONDITIONS WITH MANY AREAS SITTING IN
THE 50S MOST DAYS. LASTLY, ALL EYES CONTINUE TO BE ON FRIDAY'S
SEVERE WEATHER CHANCES AS A COLD FRONT PROGRESSES THROUGH THE
REGION. WHILE SOME UNCERTAINTY REMAINS, THE CHANCES FOR ANYTHING
STRONGER WILL BE CONDITIONALLY DEPENDENT ON IF WE CAN GET ENOUGH
CONVERGENCE ON THE FRONT ITSELF TO BREAK THROUGH THE WEAKENING CAP.
EITHER WAY, SPC CURRENTLY HAS MOST OUR OUR AREA OUTLINED IN A
DAY 3 MARGINAL RISK (LEVEL 1 OF 5) WITH PORTIONS OF FAR EASTERN
SD AND SOUTHWESTERN MN OUTLINED IN A SLIGHT RISK (LEVEL 2 OF 5)
FOR FRIDAY AFTERNOON AND EVENING.
DISCUSSION
ISSUED AT 1251 PM CDT WED SEP 9 2026
HIGH PRESSURE SETTLE SOUTH TONIGHT AND SHOULD LEAD TO SOME CRISP
MORNING TEMPERATURES ON THURSDAY. LOOK FOR MORNING LOWS FROM THE MID
40S IN THE LOWER SPOTS TO THE LOWER 50S.
RETURN FLOW SETS UP THROUGH THE DAY THURSDAY WITH SOUTHERLY WINDS
LIKELY GUSTING TO 25 MPH WEST OF I-29. HIGHS WILL GENERALLY CLIMB
INTO THE 80S, WITH SOME 70S ACROSS PARTS OF NORTHWEST IA AND
SOUTHWEST MN.
THE LEADING EDGE OF A MID LEVEL WAVE WILL SNEAK INTO CENTRAL SD
LATE THURSDAY NIGHT INTO FRIDAY MORNING, RESULTING IN INCREASED LOW
TO MID LEVEL WARM ADVECTION. WHILE MOST OF THE AREA IS CAPPED DUE TO
DRY AIR, A SMALL WEDGE OF INCREASED MOISTURE AROUND 8000 FEET MAY
BRING WEAK, 200-400 J/KG, ELEVATED INSTABILITY BASED AROUND 8000
FEET. THIS COULD RESULT IN SOME ACCAS ON FRIDAY MORNING, WITH
IMPACTS ON THE MINOR SIDE.
THIS WAVE WILL DEEPEN A BIT AND TRACK JUST NORTH OF THE AREA ON
FRIDAY AFTERNOON AND EVENING, LEADING TO A WEDGE OF INCREASED
TEMPERATURES IN THE LOW LEVELS. THIS WILL LEAD TO WIDESPREAD HIGHS
IN THE MID 80S TO LOWER 90S. THE QUESTION THEN COMES TO WHAT ARE THE
CONVECTIVE CHANCES AS THIS WEDGE OF WARM AIR SETTLE SOUTH AND COOLER
AIR FILTERS IN BEHIND ON FRIDAY NIGHT. THE ENVIRONMENT AHEAD OF THIS
FRONT WILL BE FAIRLY UNSTABLE, 2000-3000 J/KG, WITH ABOUT 40 KNOTS
OF DEEP LAYER SHEAR. THE LOWER LEVELS SHOW A NICE SOUTH TO SOUTHWEST
INFLOW, SUGGESTING THAT NEW UPDRAFTS MAY BE ON THE SOUTHWEST FLANK
OF ANY DEVELOPMENT. GIVEN THE INSTABILITY AND SHEAR AS WELL AS THE
POTENTIAL FOR DISCRETE CELLULAR DEVELOPMENT, ALL MODES OF SEVERE
WEATHER WILL BE POSSIBLE, INCLUDING GOLF BALL SIZED HAIL, WIND GUSTS
TO 70 MPH AND ISOLATED TORNADOES. THE MAIN NEGATIVE WILL BE THE
POTENTIAL FOR A FAIRLY STRONG CAPPING INVERSION. THIS SUGGESTS THAT
THERE MAY BE A VERY SMALL WINDOW SHORTLY BEFORE SUNSET TO GET ANY
STRONG UPDRAFTS GOING THAT COULD PRODUCE HIGHER END SEVERE WEATHER.
AS THIS SYSTEM LIFTS EAST NORTHEAST FRIDAY NIGHT, COOLER AND DRIER
AIR WILL SETTLE SOUTHWARD AND BRING A PLEASANT SATURDAY WITH HIGHS
IN THE 70S AND DEW POINTS IN THE 45 TO 55 DEGREE RANGE.
A STRONGER SYSTEM WORKS ONTO THE NORTHERN PLAINS SUNDAY INTO EARLY
MONDAY AND SHOULD BRING A MORE WIDESPREAD AREA OF SHOWERS AND
THUNDERSTORMS TO THE REGION. THE LATEST ENSEMBLE OUTPUT FROM THE
GEFS, EC AND CANADIAN ALL SUGGEST ABOUT A 30-60 PERCENT CHANCE FOR
A HALF AN INCH OR MORE OF RAINFALL FOR MUCH OF THE AREA WITH A
SLIGHT LEAN TOWARDS THE BETTER CHANCES NEAR AND NORTH OF I-90.
WEST TO SOUTHWEST FLOW ALOFT CONTINUES THROUGH MID WEEK KEEPING THE
CHANCES FOR SHOWERS AND THUNDERSTORMS IN THE AREA DURING THIS TIME.
WITH SLIGHTLY COOLER AIR IN PLACE BEHIND THE SUNDAY SYSTEM AND THE
POTENTIAL FOR CLOUDS AND PRECIPITATION, TEMPERATURES WILL BE A BIT
COOLER WITH HIGHS IN THE 70S AND LOWS IN THE UPPER 40S TO MID 50S.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 652 PM CDT WED SEP 9 2026
VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. WITH A WEAK HIGH
PRESSURE SYSTEM MOVING THROUGH THE AREA WINDS ACROSS THE REGION WILL
SHIFT FROM PRIMARILY WEST/NORTHWESTERLY TO SOUTHERLY BY THE END OF
THE TAF PERIOD. TIMING OF THIS SHIFT IS EXPECTED BETWEEN 16-18Z,
WITH KHON FIRST AND KSUX LAST. NO SIGNIFICANT IMPACTS FOR CEILING OR
VISIBILITY THROUGH THE AREA WITH THE PROGRESSION OF SAID HIGH
PRESSURE. THE NOCTURNAL LOW-LEVEL JET WILL STRENGTHEN AFTER THE TAF
PERIOD LEADING TO LLWS POTENTIALLY AT KFSD WITH UP TO 45KTS EXPECTED
THROUGH FRIDAY MORNING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...05
DISCUSSION...08
AVIATION...RAFALSKI
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