493
FXUS63 KFSD 141941
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
241 PM CDT SUN SEP 14 2025
KEY MESSAGES
- SCATTERED THUNDERSTORM DEVELOPMENT WILL CONTINUE THROUGH THE
EVENING HOURS. AN ISOLATED STRONG TO SEVERE STORM REMAINS
POSSIBLE, WITH BRIEF DOWNBURST WINDS AND 1" HAIL THE MAIN
RISKS.
- TEMPERATURES REMAIN ABOVE NORMAL THROUGH TUESDAY BEFORE A
STRONGER COOLDOWN BACK TO NEAR OR BELOW NORMAL TEMPERATURES IS
EXPECTED THE SECOND HALF OF THE WEEK.
- CONVECTION RISKS RETURNS BY TUESDAY, WITH A PATTERN SHIFT
TOWARDS A MULTIDAY RAIN RISK INTO THE UPCOMING WEEKEND.
DISCUSSION
ISSUED AT 237 PM CDT SUN SEP 14 2025
THIS AFTERNOON: CONVECTIVE TEMPERATURES HAVE BEEN MET IN MOST
LOCATIONS THIS AFTERNOON SPARKING THE DEVELOPMENT OF ISOLATED TO
SCATTERED THUNDERSTORMS OVER PORTIONS OF THE TRI-STATE AREA. MLCAPE
VALUES REMAIN BETWEEN 1000-1500 J/KG AND EFFECTIVE SHEAR REMAINS
NEAR 30 KNOTS, HOWEVER MID-LVL LAPSE RATES REMAIN RATHER WEAK AND
SOUNDINGS ARE GENERALLY THIN. THAT SAID, DCAPE IS FAIRLY IMPRESSIVE
AOA 1200 J/KG. STORMS THAT HAVE DEVELOPED THUS FAR THIS AFTERNOON
HAVE EXHIBITED FAIRLY SHORT LIFESPANS WITH SHALLOW CORES, WITH
SOME BRIEF DOWNBURSTS.
LATE AFTERNOON AND THIS EVENING: ADDITIONAL SCATTERED THUNDERSTORMS
WILL DEVELOP WITHIN NARROW AREAS OF CONFLUENCE IN EASTERN NEBRASKA,
SOUTH DAKOTA, AND ADJACENT AREAS OF MN/IA. THOUGH SOUNDINGS REALLY
SUGGEST NO MAJOR ENVIRONMENTAL CHANGES, OTHER THAN A LESSONING OF
THE MID-LVL DRY LAYER THIS EVENING. THUS, WE'LL LIKELY CONTINUE TO
SEE ISOLATED STRONGER STORMS, PERHAPS TURNING BRIEFLY SEVERE WITH 60
MPH DOWNBURSTS POSSIBLE AND MARGINALLY SEVERE HAIL. WE'LL ALSO
WATCH AN AREA OF CLEARING OVER NORTH CENTRAL NEBRASKA AND SOUTH
CENTRAL SOUTH DAKOTA THROUGH THE AFTERNOON, WHERE ADDITIONAL SURFACE
BASED DEVELOPMENT TIED TO THE SURFACE LOW MAY TAKE PLACE. THREATS
ARE LIKELY NOT TO CHANGE MUCH WITH THIS ACTIVITY GIVEN A SIMILAR
ENVIRONMENT TO AREAS FURTHER EAST, HOWEVER AT LEAST THROUGH SUNSET,
AN ISOLATED TOR RISKS COULD DEVELOP OVER THE FAR WESTERN COUNTIES OF
THE CWA. SEVERE WEATHER RISKS LIKELY BEGIN TO WANE AS SUNSET
AND DIURNAL COOLING ARRIVES, THROUGH GIVEN INCREASE IN THE LLJ A
VERY ISOLATED STRONG SOUTH TO NORTH WIND GUST COULD DEVELOP IN
CONVECTION. SHOWERS DISSIPATE AREAWIDE THROUGH DAYBREAK.
MONDAY: THE UPPER TROUGH PULLS NORTHEAST EARLY MONDAY, LEAVING
BREEZY SOUTHERLY TO SOUTHWESTERLY WINDS IN PLACE THROUGH THE DAY.
HIGH TEMPERATURES WILL AGAIN CLIMB WELL ABOVE NORMAL INTO THE MIDDLE
AND UPPER 80S. GIVEN RECENT TRENDS HAVE NUDGED HIGHS UP A DEGREE OR
TWO. ONLY A VERY SLIGHT CHANCE FOR AN EVENING THUNDERSTORM DEVELOPS
IN CENTRAL AND NORTHWESTERN IOWA IN THE EVENING AS WEAK CONVERGENCE
AND LINGERING DPVA COULD SPARK AN ISOLATED NON-SEVERE STORM.
TUESDAY: ANOTHER VERY WARM DAY IS LIKELY TUESDAY AS A SURFACE
BOUNDARY BECOMES ESTABLISHED FROM SOUTHWEST NEBRASKA THROUGH CENTRAL
AND NORTHEASTERN SOUTH DAKOTA DURING THE DAY. SOUTHERLY FLOW SHOULD
PUSH HIGH TEMPERATURES INTO THE UPPER 80S TO LOWER 90S IN MOST
LOCATIONS. SOUNDINGS SHOW A MOSTLY CAPPED ENVIRONMENT IN THE
AFTERNOON AND EVENING, BUT THERE ARE SOME HINTS THAT CONVERGENCE
ALONG THE AFOREMENTIONED FRONT COULD SPARK A FEW STORMS OVER
NORTH CENTRAL NEBRASKA NORTHEASTWARD LATE IN THE DAY. THIS
CONVECTION RISK MAY INCREASE AFTER DARK AS BOTH AN UPPER WAVE
AND LLJ BEGINS TO INCREASE THROUGHOUT THE CWA.
WEDNESDAY-SATURDAY: A FAIRLY UNSETTLED MIDDLE AND END OF THE WEEK
IS EXPECTED, THOUGH SEVERE WEATHER RISKS CONTINUE TO REMAIN LOW.
MEDIUM RANGE MODELS HAVE TRENDED BACK TOWARDS THE EVENTUAL
DEVELOPMENT OF A SLIGHTLY CUTOFF LOW BY THE END OF THE WEEK WITH
MUCH OF THE CWA TRAPPED ON THE NORTHEASTERN AND EASTERN SIDE OF THE
TROUGH/LOW. THIS WILL RESULT IN MULTIPLE DAYS OF SHOWER AND
THUNDERSTORM RISKS TRENDING INTO NEXT WEEKEND ALONG WITH COOLER
TEMPERATURES. DEPENDING ON THE WOBBLE OF THE UPPER LOW AND
TRAJECTORY OF THE LOW-LVL FLOW AND MOISTURE, SOME LOCALIZED HEAVY
RAIN RISKS COULD ALSO DEVELOP.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1214 PM CDT SUN SEP 14 2025
VFR CONDITIONS CONTINUE OVER MOST OF THE AREA, HOWEVER BUILDUP
OF CONVECTIVE CLOUDS CONTINUES ALONG AND WEST OF I-29 EARLY THIS
AFTERNOON. CONFIDENCE REMAINS LOW ON THE COVERAGE AND DURATION
OF ISOLATED TO SCATTERED STORMS LATER THIS AFTERNOON. AN INITIAL
AREA OF CONVECTION MAY BEGIN TO TRY TO FORM NEAR OR WEST OF I-29
AND DRIFT EASTWARD, WITH A SECONDARY AREA OF PRECIPITATION
FORMING NEAR OR WEST OF THE JAMES RIVER LATER THIS EVENING. WILL
KEEP PREVAILING TSRA/SHRA LIMITED AND FOCUS MORE ON LOWER
PROBABILITY GROUPS GIVEN UNCERTAINTY. PERHAPS HIGHEST CONFIDENCE
ON IMPACTS WILL BE THIS EVENING AND INTO THE EARLY OVERNIGHT
HOURS, AND WILL INSERT VICINITY MENTION AT BOTH FSD/SUX.
OCCASIONAL MVFR TO IFR VISIBILITY MAY BE POSSIBLE IN HEAVIER
RAIN.
SHOWERS AND THUNDERSTORMS MOVE EAST AND/OR DISSIPATE EARLY IN
THE OVERNIGHT LEAVING VFR CONDITIONS IN MOST AREAS AND A
SOUTHWESTERLY WIND. WILL NEED TO WATCH THE HON AREA FOR LOWER
STRATUS THAT MAY TRY TO BUILD INTO THE AREA AFTER MIDNIGHT.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...DUX
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