677
FXUS63 KFSD 070840
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
340 AM CDT MON SEP 7 2026
KEY MESSAGES
- ISOLATED, NON-SEVERE THUNDERSTORMS CONTINUE ACROSS
NORTHWESTERN IOWA THROUGH DAYBREAK. SEVERE WEATHER IS NOT
EXPECTED, BUT LOCALLY HEAVY RAIN HAS BEEN OCCURRING AND MAY
LEAD TO ISOLATED FLASH FLOODING.
- ISOLATED TO SCATTERED SHOWERS AND STORMS ARE POSSIBLE ALONG
AND NORTH OF I-90 THIS MORNING INTO EARLY AFTERNOON. SEVERE
RISK IS LOW.
- ADDITIONAL SCATTERED AND POSSIBLY SEVERE STORMS EXPECTED LATE
THIS AFTERNOON ACROSS SOUTHEASTERN AND SOUTH CENTRAL SOUTH
DAKOTA, MOVING EAST THROUGH TONIGHT. PING PONG BALL SIZED
HAIL, 60 MPH WIND GUSTS, AND BRIEF HEAVY RAIN ARE THE MAIN
THREATS. A TORNADO OR TWO POSSIBLE.
- QUIET BUT CONTINUED WARM CONDITIONS ARE EXPECTED FOR THE REST
OF THE WORK WEEK.
UPDATE
ISSUED AT 339 AM CDT MON SEP 7 2026
AN AREA OF SHOWERS AND STORMS CONTINUES OVER NORTHWESTERN IA INTO
SOUTHEASTERN SD EARLY THIS MORNING, TIED TO A WAVE AND SOME LL
CONVERGENCE. ALTHOUGH SEVERE WEATHER IS NOT EXPECTED, AM CONCERNED
WITH FLASH FLOODING DUE TO TRAINING STORMS OVER NORTHEASTERN
WOODBURY AND INTO NORTHWESTERN PLYMOUTH COUNTY - HAVE SEEN REPORTS
OF OVER 3 INCHES SINCE MIDNIGHT AND ISSUED A FLASH FLOOD WARNING
THROUGH 6 AM FOR THIS AREA. MAY SEE FURTHER DEVELOPMENT IN THIS AREA
INTO SOUTHWESTERN MN THROUGH THE MORNING HOURS AS THE 700 MB WAVE
LIFTS NORTH.
FURTHER WEST, WATCHING THE ACTIVITY ACROSS WESTERN SD/NE WHICH IS
TIED TO THE NEXT WAVE AND ANOTHER SEGMENT OF THE LLJ. THIS MAY BE
THE CATALYST FOR ADDITIONAL SHOWERS/STORMS, MAINLY NORTH OF I-90,
MID-LATE MORNING INTO THE EARLY AFTERNOON HOURS. SEVERE WEATHER RISK
IS LOW WITH THESE STORMS.
MAIN FOCUS IS WITH THE INCREASING LLJ LATER THIS AFTERNOON AND
TONIGHT, IN TANDEM WITH MAIN TROUGH EJECTION FROM THE ROCKIES.
LEADING WAVE AND LLJ ALONG WITH A SURFACE BOUNDARY AND DESTABILIZING
ATMOSPHERE SHOULD PROVIDE THE CATALYST FOR SHOWERS AND STORMS TO
DEVELOP. INSTABILITY ALL MODES OF SEVERE WEATHER ARE POSSIBLE FROM
ROUGHLY 5 PM THROUGH 1 AM, AS INITIAL DISCRETE CELLS MAY GROW
UPSCALE AND MOVE EAST. SHEAR AT ALL LEVELS INCREASES THROUGH THE
EVENING, AND INCREASING MID LEVEL LAPSE RATES WILL ALSO BE
SUPPORTING OF HAIL TO THE SIZE OF PING PONG BALLS - POSSIBLY LARGER
IF A STORM CAN MAINTAIN DISCRETE STATUS FOR LONGER. A TORNADO OR TWO
ARE POSSIBLE WITH SURFACE BASED STORMS WITH CURVED HODOGRAPHS AND
INCREASING SHEAR IN THE LOWEST LEVELS. 65 MPH WIND GUSTS ARE ALSO
POSSIBLE. MAY SEE SOME LOCALLY HEAVY RAINFALL AS WELL, BUT MORE
PROGRESSIVE STORM MOTION SHOULD HELP LIMIT WIDESPREAD CONCERNS.
LOCALIZED FLASH FLOODING IS POSSIBLE, ESPECIALLY IF STORMS MOVE OVER
AREAS WHICH HAVE SEEN RECENT HEAVY RAIN.
STILL QUESTIONS FOR TUESDAY REGARDING WHERE THE SURFACE BOUNDARY
ENDS UP AND IMPACTS FROM OVERNIGHT/EARLY MORNING CONVECTION. BETTER
SHEAR LOOKS TO BE OFFSET FROM THE GREATEST INSTABILITY WHICH LIES
AHEAD OF THE FRONT. COULD SEE A STRONGER STORM OR TWO ACROSS
NORTHWESTERN IA AND ADJACENT AREAS OF CENTRAL MN/EASTERN NE/FAR
SOUTHEASTERN SD IN THE AFTERNOON AND EVENING.
DISCUSSION
ISSUED AT 1246 PM CDT SUN SEP 6 2026
THIS AFTERNOON: STRONG CONVECTION CONTINUES TO DEVELOP IN AREAS
ALONG BUT MOSTLY EAST OF I-29 THIS AFTERNOON. THE AREA CONTINUES TO
RESIDE IN A MODERATELY UNSTABLE ENVIRONMENT, BUT LACKS ANY
MEANINGFUL SHEAR AND MID-LVL LAPSE RATES. HOWEVER, CLIMATOLOGICALLY
SIGNIFICANT PWATS ARE IN PLACE, WITH ENOUGH DCAPE TO SUGGEST AN
INCREASED RISK FOR WET MICROBURSTS OVER THE NEXT 1-3 HOURS IN A
NARROW CORRIDOR FROM MADISON TO SIOUX FALLS, SIOUX CENTER, CHEROKEE,
STORM LAKE, LE MARS, AND SIOUX CITY. RAINFALL MAY BE THE MOST
IMPACTFUL HAZARD THIS AFTERNOON WITH 1-2 HR TOTALS OF 3-4" ALREADY
IN PORTIONS OF SOUTHERN MINNESOTA. ADDITIONAL CONVECTION IS LIKELY
TO CONTINUE TO PRODUCE 2-4" TOTALS IN POCKETS OF NW IOWA, THOUGH
COLD POOL DEVELOPMENT MAY HELP PUSH STORMS OFF AN AREA BEFORE
EXTREME VALUES MAY BE PRODUCED. THE STRONGER MCV WILL ALSO NUDGE
IT'S WAY NORTHWARD LATER THIS AFTERNOON, AND MAY WORK TO PRODUCE
ADDITIONAL NORTHWARD/NORTHEASTWARD CONVECTION WITH IT.
TONIGHT: THIS SHORTWAVE/MCV WILL DRAG IT'S FEET EASTWARD THIS
EVENING, WITH SOME EXPECTED WEAKENING OF CONVECTION WITH THE LOST OF
DAYTIME HEATING AND GENERAL STABILIZATION OF THE ENVIRONMENT NEARBY.
HOWEVER, AN INCREASED LLJ MAY BEGIN TO DEVELOP AFTER 02Z WHICH
COULD BRING RETURNING ELEVATED SHOWERS AND ISOLATED
THUNDERSTORMS TO THE CWA LATE THIS EVENING AND CONTINUING INTO
THE OVERNIGHT HOURS. THIS ACTIVITY WILL LIKELY NOT BE SEVERE,
BUT ANY SHOWER COULD STILL BRING BRIEF HEAVY RAIN.
MONDAY-TUESDAY: ELEVATED SHOWER ACTIVITY DIMINISHES TOWARDS DAYBREAK
AS SHORTWAVE RIDGING ARRIVES. AN EJECTING TROUGH OUT OF THE ROCKIES
WILL BRING ADDITIONAL ELEVATED CONVECTION INTO CENTRAL AND NORTHERN
SOUTH DAKOTA INTO MONDAY AFTERNOON, PERHAPS GRAZING THE WESTERN CWA.
AS THE EML GRADUALLY ERODES INTO SOUTH CENTRAL SD LATE IN THE
AFTERNOON, A FEW STRONG TO SEVERE STORMS MAY DEVELOP AND TRACK
EAST SOUTHEAST INTO THE EARLY OVERNIGHT HOURS. AS THE LLJ
INCREASES AFTER DARK, ELEVATED CONVECTION MAY EXPAND IN COVERAGE
WITH CONTINUED LOW- END SEVERE WEATHER RISKS FOR TUESDAY
MORNING.
MORE UNCERTAINTY FOR TUESDAY, WHICH IS FOCUSED MORESO ON THE
LOCATION OF THE SURFACE FRONT AND IMPACTS OF OVERNIGHT ELEVATED
CONVECTION. WHILE THE PRIMARY SURFACE FRONT SETTLES IN NORTHWEST
IOWA, A SECONDARY STRONGER DEW POINT GRADIENT ARRIVES LATER IN THE
AFTERNOON. SHOULD SUFFICIENT CLEARING DEVELOP, THEN A STORM OR TWO
COULD BECOME STRONGER BY MID-AFTERNOON WITH ACTIVITY QUICKLY
TRACKING SOUTHEAST BY THE EVENING.
EXTENDED: WITH ONGOING CONVECTION, NO FORECAST CHANGES MADE TO THE
EXTENDED AS A TEMPORARILY REPRIEVE FROM ACTIVE WEATHER
DEVELOPS. TEMPERATURES MAY STILL REMAIN NEAR TO ABOVE NORMAL
FOR THE REST OF THE WORK WEEK.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1238 AM CDT MON SEP 7 2026
SCATTERED LIGHT SHOWERS ARE ONGOING OVER NORTHWEST IOWA. THESE WILL
TAPER OFF OVER THE NEXT FEW HOURS. VFR CONDITIONS FOR THE OVERNIGHT
EXCEPT FOR AREAS IN SOUTHWEST MINNESOTA WHERE WINDS HAVE BECOME
LIGHT ENOUGH FOR PATCHY FOG TO FORM. FOG WILL DISSIPATE AS SOUTHEAST
WINDS INCREASE THROUGH 07.12Z. GUSTS WEST OF I-29 WILL BE 20-27 KTS,
WHILE GUSTS TO THE EAST WILL BE 20 KTS OR LESS. BREEZY WINDS EXPAND
EAST THROUGH THE AFTERNOON WITH GUSTS OF 20-30 KTS WITH A FEW GUSTS
TO 33 KTS POSSIBLE OVER SOUTH CENTRAL SOUTH DAKOTA. WINDS REMAIN
GUSTY THROUGH THE END OF THE PERIOD.
WE'LL BE WATCHING FOR TWO ROUNDS OF SHOWERS AND THUNDERSTORMS
TOMORROW. THE FIRST ROUND LOOKS TO BEGIN AROUND 07.15Z THROUGH THE
LATE MORNING TO EARLY AFTERNOON. THIS ROUND LOOKS TO REMAIN MOSTLY
NORTH OF I-90. WIDESPREAD SEVERE WEATHER IS NOT EXPECTED, HOWEVER AN
ISOLATED STORM MAY BECOME STRONG TO SEVERE PRODUCING 1 INCH HAIL AND
52 KT WINDS. THE SECOND ROUND LOOKS TO BEGIN IN THE LATE AFTERNOON
TO EARLY EVENING. THIS ROUND BRINGS INCREASED POTENTIAL FOR SEVERE
WEATHER. INITIAL STORM MODE OVER CENTRAL SOUTH DAKOTA WILL MOST
LIKELY BE SUPERCELLS. THESE COULD PRODUCE HAIL UP TO THE SIZE OF A
PING-PONG BALL, HEAVY RAIN, AND WIND GUSTS TO 60 MPH. THOUGH THE
RISK IS LOW AN ISOLATED TORNADO IS ALSO POSSIBLE. AS STORMS APPROACH
THE I-29 CORRIDOR THEY MAY BEGIN TO GROW UPSCALE INTO A BROKEN LINE
TO A QLCS. HAIL THREATS DIMINISH TO MARGINALLY SEVERE BUT WIND RISKS
INCREASE. ISOLATED BRIEF SPIN UPS AND WEAK TORNADOES ARE ALSO
POSSIBLE ALONG BOWING SECTIONS. STORMS WILL BE ONGOING EAST OF I-29
THROUGH THE END OF THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...DUX
AVIATION...AJP
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