542
FXUS63 KFSD 070239
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
939 PM CDT SUN SEP 6 2026
KEY MESSAGES
- SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE FOR AREAS
SOUTH OF I-90 THROUGH THE EVENING. SHOWERS SHOULD REMAIN
BELOW SEVERE CRITERIA.
- ISOLATED TO SCATTERED MORNING SHOWERS ARE POSSIBLE ALONG AND
NORTH OF I-90. THESE ARE NOT EXPECTED TO BE SEVERE.
- ISOLATED STRONG TO SEVERE STORMS WILL AGAIN BE POSSIBLE LATE
MONDAY AFTERNOON INTO TUESDAY MORNING. LARGE HAIL UP TO THE
SIZE OF A PING-PONG BALL, WIND GUSTS OF 60 MPH, HEAVY RAIN ARE
ALL POSSIBLE. THOUGH THE RISK IS LOW, AN ISOLATED TORNADO IS
ALSO POSSIBLE.
- QUIET BUT CONTINUED WARM CONDITIONS ARE EXPECTED FOR THE REST
OF THE WORK WEEK.
UPDATE
ISSUED AT 934 PM CDT SUN SEP 6 2026
AN AREA OF CONVERGENCE ALONG A SURFACE BOUNDARY WILL KEEP
SHOWERS AND THUNDERSTORMS IN THE FORECAST FOR MUCH OF THE
OVERNIGHT. STORMS WILL MOST LIKELY REMAIN ALONG AND SOUTH OF
I-90, BUT IT IS POSSIBLE A FEW MAY SNEAK FARTHER NORTH,
ESPECIALLY ALONG AND EAST OF I-29. THESE STORMS ARE NOT EXPECTED
TO BE SEVERE, HOWEVER THEY COULD STILL PRODUCE 40-50 MPH WIND
GUSTS AND BRIEF PERIODS OF HEAVY RAIN.
THROUGH THE OVERNIGHT SOUTHERLY 850 MB WINDS ADVECT IN A PLUME OF
WARM AND MOIST AIR. BY SUNRISE A MARGINALLY UNSTABLE ENVIRONMENT
WILL BE IN PLACE WITH A LOW AMPLITUDE WAVE APPROACHING OUT OF THE
SOUTHWEST AND AN INCREASING LLJ. THIS COULD TRIGGER A MORNING
ROUND OF ELEVATED SHOWERS AND THUNDERSTORMS IF A PARCEL CAN LIFT
OFF THE 850-700 MB LAYER. WIDE SPREAD SEVERE WEATHER IS NOT
ANTICIPATED, HOWEVER ONE OR TWO STORMS MAY BECOME STRONG TO
SEVERE PRODUCING HAIL TO THE SIZE OF A QUARTER AND WIND GUSTS TO
60 MPH. THESE SHOULD STAY ALONG AND NORTH OF I-90 AS THEY
PROGRESS TO THE EAST. TIMING IS MOST LIKELY BETWEEN 10 AM AND 3
PM MONDAY.
MEANWHILE, THETA-E CONTINUES TO ADVECT IN FORMING A DEEP RIDGE OVER
CENTRAL AND EASTERN SOUTH DAKOTA NORTH TO THE CANADIAN BORDER.
INSTABILITY CONTINUES TO INCREASE AHEAD OF DEEPENING TROUGH OVER THE
EASTERN ROCKIES. THIS TROUGH EJECTS OUT ONTO THE PLAINS IN THE EARLY
AFTERNOON AND A SURFACE LOW PRESSURE FORMS. THE LLJ INCREASES IN
RESPONSE TO A TIGHTENING SPG. BY MID-TO-LATE AFTERNOON THE CAP WEST
OF THE JAMES RIVER WILL HAVE MIXED OUT, AND THE LOW AND ASSOCIATED
FRONTAL BOUNDARY WILL BE AT OUR WESTERN CWA BORDER. MODELS VARY A
BIT BUT IN GENERAL EXPECT 1500-2500 J/KG MUCAPE, 35-45 KTS OF BULK
SHEAR, MARGINAL MID-LEVEL LAPSE RATES, BUT STEEP 7+ C LOW LEVEL
LAPSE RATES TO BE IN PLACE BY THIS TIME. AS THE BOUNDARY SWEEPS
THROUGH THE LLJ CONTINUES TO INCREASE TO 50 KTS. INITIAL CONVECTION
HAS THE POTENTIAL TO BE STRONG TO SEVERE PRODUCING LARGE HAIL THE
SIZE OF A HALF DOLLARS UP TO PING-PONG BALLS, HEAVY RAINFALL, AND
WIND GUSTS TO 60 MPH. A SHARP CLOCK WISE CURVE TO THE HODOGRAPH AND
ENHANCED STRETCHING POTENTIAL COMBINED WITH SURFACE TO 1 KM SRH OF
195 M2/S2 AND SURFACE TO 3 KM SRH OF 300+ M2/S2 ALL INDICATE THE
POTENTIAL THAT UPON CONVECTION INITIATION A STORM OR TWO COULD
PRODUCE A TORNADO. THIS PROBABILITY IS LOW, BUT STILL NEEDS TO BE
MENTIONED. TIMING OF GREATEST SEVERE RISK LOOKS TO BE BETWEEN 6PM
MONDAY AND 1 AM TUESDAY. STORM MODE LOOKS TO BE INITIALLY SUPER
CELLULAR WITH DEEP LAYER SHEAR VECTORS NEARLY PERPENDICULAR TO THE
FRONT. OVER TIME THE VECTORS BECOME ORIENTATED AT A 45 DEGREE
ANGLE, WHICH WOULD LIKELY RESULT IN SUPERCELLS GROWING INTO A
BROKEN LINE.
CERTAINTY IN THE LATE AFTERNOON/EVENING STORMS IS LOW TO MEDIUM, DUE
TO THE FACT THAT MORNING CONVECTION MAY WORK OVER SOME OF THE
ENVIRONMENT. DEPENDING ON WHEN THOSE STORMS AND CLOUDS CLEAR OUT
WILL IMPACT HOW WELL THE ATMOSPHERE RECOVERS.
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 /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 643 PM CDT SUN SEP 6 2026
SCATTERED SHOWERS AND THUNDERSTORMS LINGER ALONG AND SOUTH OF
HIGHWAY 18. THESE WILL CONTINUE TO MOVE EAST AND EXPAND NORTH,
KEEPING CHANCES FOR STORMS IN THE TAFS UNTIL AROUND SUNRISE MONDAY.
A BRIEF LULL BEFORE A WEAK WAVE MOVES NORTHEAST OUT OF WESTERN
NEBRASKA. RENEWED CHANCES FOR SCATTERED THUNDERSTORMS FROM CENTRAL
SOUTH DAKOTA NORTHEAST INTO SOUTHWEST MINNESOTA ARE EXPECTED FOR THE
REMAINDER OF THE PERIOD. WIDESPREAD SEVERE WEATHER IS NOT
ANTICIPATED, HOWEVER AN ISOLATED STORM MAY BECOME STRONG PRODUCING
MARGINALLY SEVERE HAIL AND WIND GUSTS. STORM CHANCES CONTINUE BEYOND
THE END OF THIS PERIOD.
BREEZY SOUTHEAST WINDS GUSTING 15-25 KTS WILL CONTINUE THROUGH THE
OVERNIGHT. NEAR SUNRISE WINDS WILL INCREASE WITH THE APPROACH OF THE
PREVIOUSLY MENTIONED WAVE. WIDESPREAD AFTERNOON GUSTS OF 20-30 KTS
ARE EXPECTED. HIGHEST GUSTS WILL BE ALONG AND WEST OF THE I-29
CORRIDOR. GUSTY WINDS CONTINUE THROUGH THE END OF THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...AJP
DISCUSSION...DUX
AVIATION...AJP
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