382
FXUS63 KFSD 190540
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1240 AM CDT WED AUG 19 2026
KEY MESSAGES
- SCATTERED SHOWERS AND STORMS WILL SLIDE ACROSS THE AREA INTO
THE DAYTIME HOURS TODAY. SEVERE WEATHER CHANCES ARE LOW, BUT
THE STRONGEST STORMS WILL BE CAPABLE OF WIND GUSTS TO 50 MPH
AND SMALL HAIL MAINLY IN SOUTH-CENTRAL SOUTH DAKOTA AND ALONG
THE MISSOURI RIVER VALLEY.
- LATE THURSDAY AFTERNOON AND EVENING THUNDERSTORMS POSSIBLE
ALONG AN APPROACHING FRONT. BEST CHANCES IN NORTHERN AND
CENTRAL MN, BUT ISOLATED RISKS ALSO FURTHER SOUTHWEST. LARGE
HAIL AND LOCALIZED STRONG WINDS MAIN RISKS.
- MOSTLY DRY CONDITIONS HEADING INTO THE WEEKEND WITH HIGHS
EITHER SIDE OF 80 DEGREES. MORNING RAIN ON SUNDAY IS POSSIBLE.
UPDATE
ISSUED AT 938 PM CDT TUE AUG 18 2026
STORMS OVER SOUTHWEST MINNESOTA AND NORTHWEST IOWA EARLIER THIS
EVENING HAVE DIMINISHED AND PUSHED EAST OF THE AREA. THE WEAK
SURFACE FRONTAL BOUNDARY RESPONSIBLE FOR THOSE EARLIER STORMS
CONTINUES TO DRIFT SOUTHEASTWARD, WITH FURTHER DEVELOPMENT
UNLIKELY AS INHIBITION BUILDS. SO NEXT WE'LL KEEP OUR EYES OUT
TO ONGOING STORMS IN WESTERN SOUTH DAKOTA AND EASTERN WYOMING
THAT WILL DRIFT EASTWARD THROUGH THE OVERNIGHT HOURS, DRIVEN BY
A CONTINUED ACTIVE NORTHWEST FLOW PATTERN. SO LIKE THE PAST
COUPLE OF NIGHTS, WILL HAVE TO SEE IF THIS ACTIVITY COULD
MAINTAIN ANY SEVERITY AS IT MOVES INTO OUR AREA.
MUCAPE VALUES WILL LINGER IN THE 1000-1500+ J/KG RANGE MAINLY
IN SOUTH-CENTRAL SOUTH DAKOTA, WITH INSTABILITY DECREASING WITH
NORTHWARD EXTENT ACROSS THE CENTRAL PART OF THE STATE.
EFFECTIVE SHEAR VALUES WILL BE SUFFICIENT TO SUSTAIN CONVECTION
AS WELL, SO THUNDERSTORMS DO AT LEAST APPEAR LIKELY WEST OF THE
JAMES RIVER BY 3-4 AM. CHANCES FOR SEVERE WEATHER WITH THIS
LOOK VERY LOW GIVEN WEAK MID LEVEL AND LOW LEVEL LAPSE RATES AND
WEAK MID LEVEL FLOW. HOWEVER, A STRONGER WIND GUST UP TO 50 MPH
AND SMALL HAIL CAN'T BE RULED OUT MAINLY IN SOUTH-CENTRAL SOUTH
DAKOTA THROUGH DAYBREAK. STORMS SHOULD WEAKEN QUICKLY AS THEY
MOVE EAST AS THEY ENCOUNTER MORE STABLE AIR; HOWEVER, SOME RAIN
AND GENERAL THUNDERSTORMS WILL CONTINUE TO BE POSSIBLE THROUGH
THE EARLY AFTERNOON HOURS AS THE ACTIVITY GRADUALLY PUSHES EAST.
DISCUSSION
ISSUED AT 106 PM CDT TUE AUG 18 2026
THIS AFTERNOON: A WEAK FRONTAL BOUNDARY CONTINUES TO SINK SOUTHWARD
EARLY THIS AFTERNOON, WITH NOTICEABLE STRATO-CU FIELD
DEVELOPING ALONG THE HIGHWAY 20 CORRIDOR. THE REMAINDER OF THE
AFTERNOON IS LIKELY TO REMAIN DRY IN MOST LOCATIONS, OUTSIDE OF
VERY ISOLATED DEVELOPMENT ALONG THIS AFOREMENTIONED BOUNDARY.
THIS EVENING/TONIGHT: SOME GUIDANCE SHOWS ISOLATED DEVELOPMENT THIS
EVENING ALONG A WEAK CONVERGENCE ZONE IN SW MINNESOTA AND NORTHERN
IOWA. THIS CONVECTION MAY ALSO BE SPARKED BY A WEAK AREA OF
VORTICITY DROPPING THROUGH THE DAKOTAS FROM THE NORTHWEST. ANY STORM
THAT DEVELOPS WILL BE IN AN AREA OF MLCAPE AOA 1000-1500 J/KG, WITH
SUFFICIENT SHEAR TO PROMOTE PERHAPS A ROTATING STORM.
ANTICIPATING THE SEVERE WEATHER RISKS TO REMAIN LOW.
FURTHER WEST, ADDITIONAL CONVECTION IS EXPECTED TO FORM OVER THE
BLACK HILL REGION THIS EVENING AS A STRONGER WAVE ENTERS THE AREA.
THE TRACK OF THIS WAVE, ALONG WITH HOW THE LLJ PROPAGATES OVERNIGHT,
SHOULD PUSH SOME OF THIS ACTIVITY INTO SOUTH CENTRAL SD AFTER 1AM.
MUCAPE REMAINS QUITE LOW, WITH MARGINAL MID-LVL LAPSE RATES, SO
WIDESPREAD SEVERE WEATHER IS NOT ANTICIPATED. THOUGH, A FEW GUSTY
WIND GUSTS COULD REMAIN POSSIBLE THROUGH 3AM. THERE REMAINS
REASONABLE AGREEMENT THAT THIS CONVECTION COULD TRACK ALONG THE MO
RIVER VALLEY INTO EASTERN NEBRASKA BY DAYBREAK. THIS IS AN AREA
WHERE HIGHER POPS WILL BE FOCUSED.
WEDNESDAY: THE DEPARTURE OF THIS SHORTWAVE SHOULD LEAD TO A PERIOD
OF SUBSIDENCE AND QUIET WEATHER WELL INTO WEDNESDAY. CLOUD COVER MAY
BE MORE SUBSTANCIAL OVER THE SOUTHERN HALF OF THE CWA THANKS TO MID-
UPR CLOUDS FROM CONVECTION. BY THE AFTERNOON SOUTHWESTERLY SURFACE
WINDS WILL RETURN, ALLOWING HIGH TEMPERATURES TO RISE INTO THE UPPER
70S TO LOWER 80S. CONVECTION RISKS IN THE AFTERNOON AND EVENING MAY
BE QUITE NARROWED TO A ZONE AHEAD OF AN APPROACHING SURFACE FRONT IN
NORTH CENTRAL SD. FURTHER SOUTHEAST, THERE DOESN'T SEEM TO BE ANY
STRONG FOCUSING MECHANISM, WITH WEAK CONVECTIVE INHIBITION LIKELY
KEEPING THE AREA FREE OF ANY ISOLATED LARGER STORM GROWTH. WHILE
SURFACE AND LOW-LVL FOCUS REMAINS ABSENT, WE'LL NEED TO WATCH THE
PRESENCE OF ANY WEAK VORTICITY IN THE NW FLOW. FURTHER NORTHWEST,
ANY CONVECTION THAT DEVELOPS ALONG THE FRONTAL BOUNDARY MAY TRY TO
TRACK SOUTHEAST, THOUGH LESSENING INSTABILITY SHOULD LIMIT THE
OVERALL SEVERE RISKS.
THURSDAY: ANY PRECIPITATION RISK CONTINUES TO LOOK MINIMAL HEADING
INTO THURSDAY MORNING AS A STRONGER EML BEGINS TO BUILD INTO THE
REGION. SOUTHWESTERLY SURFACE WINDS OVERNIGHT MAY KEEP OVERNIGHT
LOW TEMPERATURES FROM FALLING SIGNIFICANTLY. THE AFOREMENTIONED
SURFACE BOUNDARY FROM WEDNESDAY WILL SINK SOUTHEAST THROUGH THE
DAY ON THURSDAY PROVIDING A FOCUS MECHANISM FOR STORMS BY LATE
AFTERNOON AND EVENING. MLCAPE APPROACHING 2000-3000 J/KG MAY DEVELOP
ALONG THIS BOUNDARY AS DEW POINTS TRY TO QUICKLY SURGE NORTHWARD.
THE LINGERING QUESTIONS FOR CONVECTIVE DEVELOPMENT ARE FOCUSED
ON THE TRACK OF MID-LVL VORTICITY IN THE LATE AFTERNOON, ALONG WITH
CONVECTIVE INHIBITION AHEAD OF THE BOUNDARY. THE TRACK OF SHORTWAVE
ENERGY COULD FAVOR MORE DEVELOPMENT IN CENTRAL AND NORTHERN MINNESOTA,
WITH ONLY ISOLATED STORMS FURTHER SOUTHWEST ALONG THE BOUNDARY. WHILE
INSTABILITY IS GREATER, SHEAR IS A BIT MORE MARGINAL SUGGESTING
LESS ORGANIZATION TO ANYTHING THAT DEVELOPS.
FRIDAY-MONDAY: MID-LVL HEIGHTS BEGIN TO RISE OVER THE ROCKIES AS THE
RIDGE AMPLIFIES. THE LINGERING, BUT SHARPER, NW FLOW PATTERN
OVER THE DAKOTAS MAY BRING ONE MORE WAVE INTO THE REGION FRIDAY.
HOWEVER THE SOUTHWARD PASSAGE OF THURSDAYS FRONT SHOULD PUSH
THE BEST BOUNDARY LAYER MOISTURE SOUTH OF THE AREA. THE RIDGE
AXIS BEGINS TO PUSH EASTWARD AS WE MOVE INTO THE UPCOMING
WEEKEND. A PLEASANT SATURDAY IS LIKELY IN THE REGION WITH HIGHS
EITHER SIDE OF 80. INCREASING LOW-LVL WARM ADVECTION INTO SUNDAY
COULD BRING ELEVATED SHOWERS AND THUNDERSTORMS EASTWARD INTO
SUNDAY MORNING, ALONG WITH MORE CLOUDS AND SLIGHTLY WARMER HIGHS
INTO THE LOWER TO MIDDLE 80S. AT THIS TIME, RAIN COVERAGE MAY
BE LIMITED WITH ONLY A 20-30% POP.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1237 AM CDT WED AUG 19 2026
SCATTERED SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE AREA
FROM GENERALLY WEST TO EAST THROUGH THE MORNING HOURS AND INTO
THE EARLY AFTERNOON. THE STRONGEST ACTIVITY WITH THIS WILL
MOSTLY BE CONTAINED ALONG AND SOUTH OF THE MISSOURI RIVER
VALLEY, THOUGH WEAKER THUNDERSTORMS WILL BE POSSIBLE FARTHER
NORTH AS WELL. OUTSIDE OF THE THUNDERSTORMS AND SOME OF THE
HEAVIER SHOWERS, VFR CONDITIONS ARE EXPECTED.
WINDS WILL BE MOSTLY LIGHT AND VARIABLE THROUGH THE PERIOD,
ONLY PICKING UP SLIGHTLY WEDNESDAY AFTERNOON OUT OF THE SOUTH-
SOUTHWEST AROUND 5-9 KTS. WINDS WILL TURN LIGHT AND VARIABLE
ONCE AGAIN WEDNESDAY NIGHT, EXCEPT NEAR AND WEST OF THE JAMES
RIVER WHERE WINDS WILL STAY IN THAT 5-9 KT RANGE EVEN AFTER
SUNSET.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SAMET
DISCUSSION...DUX
AVIATION...SAMET
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