279
FXUS63 KFSD 240208
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
908 PM CDT SUN AUG 23 2026
KEY MESSAGES
- SHOWERS AND STORMS SHOULD BE A BIT MORE WIDESPREAD LATE
TONIGHT INTO EARLY TOMORROW MORNING (50-70%). LOCALLY HEAVY
RAIN AND A VERY ISOLATED SEVERE STORM ARE POSSIBLE.
- MONDAY EVENING AND NIGHT COULD SEE AN ISOLATED SEVERE STORM,
WITH THE BETTER CHANCES IN CENTRAL SD AND ALSO NEAR HIGHWAY
14.
- OTHERWISE MOST DAYS THROUGH NEXT WEEK WILL SEE HIGHS IN THE
80S AND LOWS IN THE UPPER 50S TO MID 60S.
UPDATE
ISSUED AT 902 PM CDT SUN AUG 23 2026
A WEAK AREA OF CONVERGENCE EXTENDING FROM ROUGHLY IVANHOE, MN
TO SPIRIT LAKE, IA MAY PRODUCE A SPRINKLE OF TWO THIS EVENING,
BUT THE MAIN AREA TO WATCH WILL BE IN SOUTH-CENTRAL SOUTH DAKOTA
AFTER MIDNIGHT WHEN THE LOW LEVEL JET CRANKS UP TO AROUND 30-
35 KTS AND HELPS DEVELOP SHOWERS AND STORMS.
ELEVATED INSTABILITY VALUES HAVE TRENDED UP FOR TONIGHT;
HOWEVER, THE LAYERS WITH ACCESS TO THE MOST CAPE WILL HAVE LESS
SHEAR TO WORK WITH AND THIS IMBALANCE WILL LIMIT ANY SEVERE
WEATHER POTENTIAL. WITH THE LLJ IN PLACE AND DRIFTING EASTWARD,
ADDITIONAL SHOWERS AND STORMS WILL DEVELOP, INCREASING
COMPETITION BETWEEN UPDRAFTS WHICH WILL ALSO HELP LIMIT THE
SEVERE POTENTIAL. NOT TO MENTION INSTABILITY AND SHEAR WILL ALSO
BE FURTHER DECREASING AS SHOWERS AND STORMS MOVE EAST-SOUTHEAST
INTO THE EARLY MORNING HOURS. ALL THAT TO SAY, THE ONLY
REASONABLE WINDOW FOR A STORM TO PERHAPS PRODUCE QUARTER-SIZED
HAIL WILL BE THE INITIAL DEVELOPMENT AROUND 1-2 AM IN GREGORY
COUNTY, WITH ANY SEVERE THREAT RAPIDLY DIMINISHING AS NEW
SHOWERS/STORMS DEVELOP AND PUSH EAST-SOUTHEAST.
TIMING FOR SHOWER AND STORMS HAVE ALSO SHIFTED A BIT LATER IN THE
LATEST GUIDANCE, WITH ACTIVITY LIKELY NOT REACHING THE I-29 CORRIDOR
UNTIL CLOSER TO 5 AM AND THE HEAVIER SHOWERS NOW NOT PUSHING SOUTH
OF THE AREA UNTIL CLOSER TO THE 7-9 AM TIME FRAME. LOCALLY HEAVY
RAINFALL IS EXPECTED WITH ANY STORMS GIVEN HIGH PWATS PUSHING 1.75+"
BUT ACTIVITY SHOULD BE PROGRESSIVE ENOUGH TO PRECLUDE ANY FLOODING
CONCERNS. A FEW POCKETS OF 1-1.25" OF RAIN WILL BE POSSIBLE WHERE
THE STRONGEST STORMS MOVE OVER WITH VERY LOW CHANCES (<5%) OF A
SPOT PICKING UP 2" IF A MULTIPLE STORMS GO OVER AN AREA.
DISCUSSION
ISSUED AT 237 PM CDT SUN AUG 23 2026
A PAIR OF WAVES ARE AFFECTING THE AREA, OR NEARBY, TODAY. THE FIRST
IS MOVING SOUTHEAST THROUGH NEBRASKA AND IS KEEPING ANY INSTABILITY
TO THE SOUTH AND WEST BOTTLED UP. MODEL SOUNDINGS NOT HINTING AT A
WHOLE LOT OF ACTIVITY THIS AFTERNOON, WITH A FAIRLY DRY AND STABLE
AIR MASS IN PLACE.
TONIGHT A SECOND WAVE WILL PASS BY TO THE NORTH AND WILL SWING A
LITTLE BIT OF MID LEVEL MOISTURE INTO THE AREA. AS THIS MOISTURE
MOVES IN, SOME WEAK ELEVATED INSTABILITY, LIKELY 500-750 J/KG CAPE
DEVELOPS. THIS WILL SUPPORT SOME SCATTERED SHOWER AND ISOLATED
THUNDERSTORM ACTIVITY, BUT FOR NOW SEVERE WEATHER LOOKS
UNLIKELY. A FEW POCKETS OF HEAVIER RAIN ARE ALSO POSSIBLE, BUT
ALSO TRENDING DOWNWARD.
MONDAY WILL SEE TEMPERATURES WARM A BIT WITH HUMIDITY LIKELY TO
INCREASE AS WELL. THIS IS IN RESPONSE TO STRENGTHENING SOUTHERLY
FLOW AS A STRONGER WAVE MOVES EAST ALONG THE CANADIAN BORDER. THIS
WILL INCREASE INSTABILITY, ESPECIALLY TO THE NORTHWEST OF THE AREA,
AND SHOULD BRING SCATTERED THUNDERSTORMS TO PARTS OF CENTRAL SD AND
NEAR THE HIGHWAY 14 CORRIDOR. WITH THE POTENTIAL FOR ABOUT 1000-1500
J/KG CAPE AND DECENT UNIDIRECTIONAL SHEAR, AND ISOLATED SEVERE STORM
WILL BE POSSIBLE IN THESE LOCATIONS. ONE AREA TO WATCH WILL BE NEAR
NORTHWEST IA LATE MONDAY AFTERNOON AND EVENING WHERE THERE ARE SOME
HINTS THE CAP COULD WEAKEN A BIT AS ELEVATED MOISTURE ADVECTION
BRING SOME INSTABILITY TO THAT AREA. LOW CONFIDENCE, BUT SOMETHING
TO MONITOR.
NORTHWEST FLOW ALOFT TUESDAY INTO THE WEEKEND WILL KEEP SEASONALLY
WARM TEMPERATURES IN PLACE WITH HIGHS IN THE 80S AND LOWS FROM THE
UPPER 50S TO MID 60S. STARTING TO SEE A LITTLE MORE CONSISTENCY ON
THE NEXT BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS ON FRIDAY. THE
LATEST CANADIAN, GEFS AND EC ENSEMBLES ALL INDICATE ABOUT A 30-5-
PERCENT CHANCE FOR A TENTH OF AN INCH OR MORE OF PRECIPITATION.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 647 PM CDT SUN AUG 23 2026
SCATTERED SHOWERS AND STORMS LOOK TO DEVELOP LATE TONIGHT,
FAVORING AREAS NEAR AND SOUTH OF I-90 THROUGH DAYBREAK MONDAY.
CONFIDENCE REMAINS FAIRLY LOW AS TO WHETHER OR NOT THIS ACTIVITY
HITS KFSD AND KSUX OR REMAINS JUST SOUTH AND WEST OF THE SITES, BUT
STILL KEPT THE PROB30 GROUPS WITH SOME ADJUSTMENTS TO TIMING,
NOTABLY A LATER POSSIBLE ARRIVAL TIME FOR KSUX.
WINDS WILL GENERALLY REMAIN SOUTHEASTERLY THROUGH THE PERIOD WHILE
STAYING MODERATELY BREEZY. WINDS WILL BE SUSTAINED AROUND 8-12 KTS
THROUGH THE PERIOD WITH OCCASIONAL GUSTS TO AROUND 20 KTS THIS
EVENING AND AGAIN DURING THE DAY MONDAY.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SAMET
DISCUSSION...08
AVIATION...SAMET
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