839
FXUS63 KFSD 031702
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1202 PM CDT THU SEP 3 2026
KEY MESSAGES
- HOT AND HUMID CONDITIONS WILL PERSIST THROUGH AT LEAST
SATURDAY. AFTERNOON TEMPERATURES IN THE 90S WILL PUSH HEAT
INDEX VALUES NEAR 100 AT TIMES. OUTDOOR EVENTS SHOULD PLAN
ACCORDINGLY TO THE HEAT RISKS.
- ISOLATED SHOWERS AND THUNDERSTORMS WILL DIMINISH THIS
AFTERNOON, WITH QUIET CONDITIONS EXPECTED INTO FRIDAY MORNING.
WEAKENING STORMS COULD STILL PRODUCE GUSTY WINDS.
- OCCASIONAL THUNDERSTORMS WILL BE POSSIBLE AGAIN SATURDAY AND
SUNDAY, THOUGH REMAIN HIGHLY UNPREDICTABLE ON LOCATION. A FEW
STRONGER STORMS COULD BE POSSIBLE, THE THE WIDESPREAD RISK OF
SEVERE WEATHER REMAINS LOW.
- A SHIFTING PATTERN MAY BRING HIGHER RAIN CHANCES, SLIGHTLY
COOLER TEMPERATURE, AND A SEVERE WEATHER RISK EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 1158 AM CDT THU SEP 3 2026
THIS AFTERNOON: ANOTHER HOT AND HUMID EARLY SEPTEMBER DAY AS
TEMPERATURES ARE RISING INTO THE 90S. WITH DEW POINTS IN THE UPPER
60S TO LOWER 70S, HEAT INDEX VALUES WILL CLIMB BETWEEN 95 AND 100
DEGREES. MID-LVL VORTICITY THAT HAS BEEN STRUNG ACROSS THE CWA
CONTINUES TO PRODUCE HIGH BASED SHOWERS AND ISOLATED STORMS. WHILE
UPDRAFTS THEMSELVES ARE NOT SIGNIFICANT, HIGH LCLS AND SIGNIFICANT
DCAPE MAY CONTINUE TO LEAD TO POCKETS OF STRONGER WINDS AS THEY
TRACK NORTHEAST AND PULSE. AS LOW-LVL TEMPERATURES INCREASE AND
VORTICITY STRETCHES OUT AND MOVES EAST, THIS ACTIVITY SHOULD
DISSIPATE BY MID-AFTERNOON. SOME LOCALIZED AREAS MAY HAVE AN
IMPACT ON THEIR HIGH TEMPERATURE DUE TO THE ACCOMPANYING CLOUD
COVER.
TONIGHT: SHORTWAVE RIDGING ARRIVES FOR THE OVERNIGHT HOURS, WITH
SKIES CLEARING THIS EVENING. HOWEVER WE'LL REMAIN VERY WARM IN THE
LOW-LVL AND ANY SURFACE WIND WILL RESULT IN LOW TEMPERATURES IN THE
70S. CONVECTION RISKS CONTINUE TO STAY ON THE LOWER END, WITH ANY
FOCUS FOR CONVECTION TIED TO CONVERGENCE ON THE LLJ TO THE EAST OF
THE CWA. WE MAY HAVE TO WATCH FOR SOME FOG FOCUSED IN AREAS ALONG
AND NORTH OF HIGHWAY 14.
FRIDAY: A VARIABLE WIND EARLY WILL GIVE WAY TO SOUTHERLY WINDS
QUICKLY ON FRIDAY. WITH HIGHLY ANOMALOUS 925:850 MB TEMPERATURES
REMAINING IN PLACE, WE'LL AGAIN SEE HIGH TEMPERATURES RISE INTO
THE MIDDLE TO EVEN UPPER 90S. THE FOCUS FOR THE WARMEST
TEMPERATURES MAY BE IN THE JAMES RIVER VALLEY WHERE MORE
SIGNIFICANT IMPACTS FROM THE DROUGHT HAVE CONTINUED. IN THESE
AREAS BOTH HREF AND THE NBM INDICATE A 40-60% PROBABILITY OF
REACHING 100 DEGREES. HEAT INDEX VALUES WILL TOP OUT NEAR 100
DEGREES FOR A COUPLE HOURS MID- AFTERNOON, THOUGH THE DURATION
MAY NOT BE LONG ENOUGH TO WARRANT AN ADVISORY ATTM. OUTSIDE OF
DAYBREAK CONVECTION IN THE FAR EASTERN CWA, SIGNIFICANT CAPPING
SHOULD LIMIT THE POTENTIAL FOR AFTERNOON AND EVENING CONVECTION.
CONVECTION RISKS MAY INCREASE SLIGHTLY BY DAYBREAK SATURDAY AS SOME
GUIDANCE HINTS AT THE REDEVELOPMENT OF LLJ CENTERED THROUGH CENTRAL
SOUTH DAKOTA. AS HAS BEEN THE NORMAL, VERY ISOLATED STRONG
CONVECTION COULD BE POSSIBLE, AND WITH STEEP MID-LVL LAPSE RATES,
THIN STABLE BOUNDARY INVERSION, AND CONSIDERABLE DRY AIR IN THE SUB-
CLOUD AREA, ADDITIONAL HEAT BURSTS MAY BE POSSIBLE.
SATURDAY-SUNDAY: A BIT MORE UNCERTAINTY LINGERS FOR THE DAYTIME
HOURS OF SATURDAY. ANY MORNING CONVECTION COULD GENERATE MID-
LVL VORTICITY THAT COULD CAUSE PERSISTENT LINGERING ISO-SCT
STORMS INTO THE EARLY AFTERNOON HOURS. SHOULD CONVECTION FORM
AND LINGER, THEN IT MAY MESS WITH THE AFTERNOON TEMPERATURE
FORECAST. CURRENTLY ANTICIPATING ANOTHER HOT AND HUMID DAY WITH
HIGHS IN THE 90S, AND A FEW HOURS IN THE MID-LATE AFTERNOON WITH
HEAT INDEX VALUES EITHER SIDE OF 100. ANYONE WITH
AFTERNOON/EVENING OUTDOOR ACTIVITIES MAY WANT TO CONSIDER
ADJUSTING THE TIMING OF THEIR PLANS DUE TO THE HEAT.
THE BROAD RIDGE REMAINS PLANTED OVERHEAD ON SUNDAY, WITH SOME
POTENTIAL FOR MID-LVL VORTICITY TO RIDE OVER THE TOP OF THE RIDGE
SATURDAY NIGHT AND SUNDAY. THESE WAVES ARE HIGHLY UNPREDICTABLE,
AND LEAD TO SPURIOUS MCS DEVELOPMENT THAT MAY OR MAY NOT DEVELOP.
TYPICALLY THESE MCS WOULD TRACK ALONG THE PERIPHERY OF THE EML
(SOMETIMES TRACKED BY THE +10 TO +12C TEMPERATURE LINE). THIS COULD
CAUSE A WEAKENING MCS TO TRACK SOUTHWARD INTO THE TRI-STATE
AREA EARLY IN THE DAY.
MONDAY-WEDNESDAY: UPPER TROUGHING DIGGING INTO THE WESTERN CONUS
WILL SUPPRESS THE CENTRAL PLAINS RIDGE AND PUSH IT SLIGHTLY FURTHER
TO THE EAST. THE RESULTING SOUTHERLY MID-LVL FLOW WILL PULL STRONGER
RETURN FLOW NORTHWARD AND LEAD TO AN INCREASE IN POPS FOR THE EARLY
PORTIONS OF THE WEEK. DEPENDING ON THE POSITIONING OF THE SURFACE
FRONTS AND UPPER JET, AN INCREASED SEVERE WEATHER SIGNAL COULD
DEVELOP. THIS SIGNAL SEEMS TO ALSO BE HINTED AT BY THE AI LEARNING
MODELS FOR MONDAY AND TUESDAY.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1158 AM CDT THU SEP 3 2026
A NARROW CORRIDOR OF HIGH-BASED SHOWERS AND ISOLATED
THUNDERSTORMS CONTINUES TO TRACK NORTHEAST AND MAY IMPACT THE
SIOUX FALLS AIRPORT OVER THE NEXT 1-2 HOURS. LOCALIZED MVFR
VISIBILITY COULD BE POSSIBLE IN HEAVIER RAIN.
ELSEWHERE VFR CONDITIONS WILL PERSIST INTO THE EVENING AND
OVERNIGHT HOURS AS WINDS TURN VARIABLE. BY DAYBREAK, PATCHY FOG
MAY DEVELOP WITH HIGH BOUNDARY LAYER MOISTURE IN PLACE. VFR
CONDITIONS WITH A DEVELOPING SOUTHERLY WIND ARRIVE LATE MORNING
FRIDAY.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...DUX
AVIATION...DUX
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