157
FXUS63 KFSD 090230
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
930 PM CDT SAT AUG 8 2026
KEY MESSAGES
- THUNDERSTORM RISKS CONTINUE TO REMAIN LOW INTO THE OVERNIGHT
HOURS, WITH SOME FOCUS ALONG OR NORTH OF HIGHWAY 14, AND
NORTHWEST IOWA AFTER MIDNIGHT. MARGINAL HAIL AND 60 MPH WINDS
WOULD BE THE MAIN RISKS ANY ANY STORM.
- LATE SUNDAY EVENING INTO MONDAY COULD BE A FOCUS POINT FOR
STRONG TO SEVERE CONVECTION IN WESTERN INTO CENTRAL SOUTH
DAKOTA. WHILE UNCERTAIN, ONE OR TWO CLUSTERS OF SEVERE STORMS
MAY DEVELOP.
- NEARLY DAILY PRECIPITATION RISKS WILL CONTINUE WELL INTO NEXT
WEEK, HOWEVER CHANCES REMAIN LOW DUE TO THE HIGH UNCERTAINTY
IN THE FORECAST.
UPDATE
ISSUED AT 927 PM CDT SAT AUG 8 2026
MINOR CHANGES TO THE PREVIOUS FORECAST POPS TO UPDATE FOR THE MOST
CURRENT TIMING AND TRACK OF STORMS. CURRENT BISMARK ND RADAR SHOWS
THUNDERSTORMS ALONG THE CENTRAL ND/SD BORDER. THIS STORM IS
PROGRESSING SOUTHEAST ALONG THE SURFACE BASED INSTABILITY GRADIENT.
IF IT HOLDS TOGETHER IT WILL ENCOUNTER AN INCREASINGLY CAPPED
ENVIRONMENT. AS IT APPROACHES THE NORTHWEST BORDER OF OUR CWA
(BEADLE AND KINGSBURY COUNTIES) IT WILL EITHER HAVE FALLEN APART
OR TRANSITIONED INTO ELEVATED CONVECTION. A SUBTLE MID TO UPPER
LEVEL WAVE AND ASSOCIATED SURFACE LOW WILL FUNNEL MODERATE
MOISTURE IN FROM THE SOUTH. A 925-850 MB THETA-E RIDGE WILL FORM
AS A RESULT. CONVECTION IS EXPECTED TO CONTINUE TO INITIATE
ALONG THIS RIDGE. ESPECIALLY AS THE LLJ KICKS INTO GEAR AFTER
MIDNIGHT. THIS WILL WORK TO FOCUS CONVERGENCE AND MAY INCREASE
STORM INTENSITY, BECOMING STRONG TO SEVERE. MAIN RISKS WILL BE
WIND GUSTS TO 65 MPH AND HAIL OF 1 TO 1.5 INCHES. AT THIS POINT
THE MAIN ACTIVITY WILL BE OVER SOUTHWEST MINNESOTA. AS THE
STORMS CONTINUE SOUTHEAST THEY MAY BEGIN TO TAKE ON MCS
CHARACTERISTICS IN THE FORM OF ONE OR MORE BOWING SEGMENTS.
STORMS PROGRESS TO THE SOUTHEAST OUT OF OUR CWA AFTER 8 AM
SUNDAY.
OVERALL SHORT TERM GUIDANCE IS IN BETTER AGREEMENT ON STORM
INITIATION AND MODE. HOWEVER, DIFFERENCES IN WAVE TRACK, TIMING, AND
LLJ INTENSIFICATION COULD RESULT IN ADJUSTMENTS TO THE MOST INTENSE
THUNDERSTORM ACTIVITY. THE HRRR AND RAP13 KEEP STORMS NORTH OF
HIGHWAY 14 IN EASTERN SOUTH DAKOTA AND INTO SOUTHWEST MINNESOTA AND
NORTHWEST IOWA. THE ARW AND NAMNEST HAVE THE WAVE AND LLJ FARTHER
WEST, AND STORMS IMPACTING MORE OF SOUTHEAST SOUTH DAKOTA. AS
SUCH, THE CONFIDENCE IN COVERAGE AND SEVERITY OF OVERNIGHT
STORMS REMAINS LOW. THESE TRENDS WILL CONTINUE TO BE MONITORED
THROUGH THE OVERNIGHT HOURS.
DISCUSSION
ISSUED AT 123 PM CDT SAT AUG 8 2026
THIS AFTERNOON: WE'RE CONTINUING TO WATCH A SLOWLY NORTHEASTWARD
ADVANCING MID-LVL CLOUD DECK EARLY THIS AFTERNOON. THIS CLOUD LAYER
MARKS THE ADVANCING EDGE OF MOISTURE (AND INSTABILITY) ADVECTING
WITHIN THE 850:700 MB LAYER. A PARCEL LIFTED FROM THIS LEVEL STILL
APPEARS TO BE FIGHTING A BIT OF INHIBITION, WHICH WILL KEEP ONLY
VERY LOW POPS IN THE FORECAST AS THIS MOVES NORTHEAST. ELSEWHERE,
WILDFIRE SMOKE ALOFT REMAINS QUITE THICK, AND MAY HAVE SLIGHT
IMPACTS ON HIGH TEMPERATURES THIS AFTERNOON.
TONIGHT: THE FORECAST REMAINS SOMEWHAT UNCERTAIN THIS EVENING AND
OVERNIGHT, THOUGH THERE ARE AT LEAST BETTER SIGNALS FOR WHERE
CONVECTION MAY FORM AFTER DARK TODAY. LATEST SHORT TERM GUIDANCE
POINTS TO TWO DISTINCT AREAS OF FOCUS. ONE NEAR THE SD/ND BORDER
INTO WEST CENTRAL MINNESOTA WHERE CURRENT AC FIELD ENDS UP BY
SUNSET. THE INITIATION OF AT LEAST A 25 TO 35 KNOT LLJ SHOULD BE
ENOUGH TO DEVELOP A FEW STORMS. IT'S POSSIBLE THAT A MINOR
SHORTWAVE COULD ALSO DROP SOUTHEAST AFTER MIDNIGHT HELPING PUSH THIS
ACTIVITY TOWARDS HIGHWAY 14 AND SW MINNESOTA BY DAYBREAK. A SECOND
AREA TO WATCH WILL BE NORTHWEST AND NORTH CENTRAL IOWA WHERE
SLIGHTLY STRONGER LLJ CONVERGENCE DEVELOPS. ANY ACTIVITY THAT FORMS
SHOULD PASS ALONG THE FAR EASTERN CWA BY 12Z. REALISTIC MUCAPE
BETWEEN 1500-2000 J/KG WITH 20-25 KNOTS OF SHEAR MAY PRODUCE A FEW
STRONGER STORMS WITH LARGE HAIL.
SUNDAY: A CONTINUED UNCERTAIN FORECAST REMAINS FOR SUNDAY. MORNING
CONVECTION SHOULD WEAKEN BY MID-MORNING AS THE LLJ WEAKENS AND ANY
ACTIVITY PUSHES EAST OF THE CWA. IN IT'S WAKE, THERE REMAINS NO
STRONG TRIGGERING MECHANISMS FOR ANY CONVECTION FURTHER WEST AND LOW-
LVL AND SURFACE FLOW MAY TURN MORE NORTHEASTERLY BY MID-DAY.
NEVERTHELESS WHILE WE MAY SEE CAPE VALUES PUSH 2500-3000 J/KG, HREF
PROBABILITIES OF LESS THAN 100 J/KG CIN REMAIN ONLY AROUND 25%,
SUGGESTING THAT SURFACE BASED CONVECTION MAY BE HARD TO COME BY.
WILDFIRE SMOKE WILL AGAIN BE QUITE THICK ON SUNDAY, AND HAVE LOWERED
TEMPERATURES A DEGREE OR TWO. THOUGH THE ONGOING DROUGHT MAY ALSO
COUNTER ACT SOME OF THOSE LIMITING EFFECTS.
SUNDAY NIGHT: SLIGHTLY INCREASED POPS ARRIVE LATE SUNDAY EVENING
INTO MONDAY AS THERE SEEMS TO BE SOME MID-LVL VORTICITY MOVING
THROUGH THE REGION. WHILE HIGHLY UNCERTAIN ON THE TRACK, THIS COULD
AT LEAST POSE SOME RISKS FOR STRONGER CONVECTION FORMING EARLY IN
THE EVENING IN WESTERN SD/ND ON THE NOSE OF AN INCREASING LLJ. THIS
CONVECTION WILL BE INITIALLY SURFACE BASED AND CAPABLE OF VERY
LARGE HAIL. THERE ARE SOME HINTS THAT THESE STORMS COULD CONGEAL
AND BEGIN TO PRODUCE A BIT MORE WIND AS THEY REACH CENTRAL SD.
THE LIMITING FACTOR IN THE EASTWARD PROGRESSION COULD BE A VERY
DRY SUB 600 MB LAYER AS THESE STORMS REACH THE JAMES RIVER
VALLEY.
MONDAY-WEDNESDAY: THE FIRST HALF OF THE WEEK CONTINUES TO LOOK VERY
UNCERTAIN GIVEN THE QUASI-ZONAL OR SLIGHTLY NORTHWEST FLOW PATTERN
ALOFT. IT'S CERTAINLY POSSIBLE ONE OR MORE OF THESE DAYS WILL
FEATURE A RAIN CHANCE, BUT THESE ARE ALL DEPENDENT ON ANY WEAK EDDY
IN THE FLOW. THERE CONTINUES TO BE SOME CONSISTENCY AGAIN TODAY ON
ONE OF THESE WAVES ARRIVING MONDAY EVENING INTO TUESDAY AND AGAIN
INTO WEDNESDAY MORNING. THE AVAILABLE INSTABILITY WOULD SUGGEST
AT LEAST A CONTINUED LOW-RISK FOR A SEVERE STORM OR TWO, THOUGH
WIND SHEAR CONTINUES TO BE BORDERLINE. TEMPERATURES REMAIN NEAR
THEIR SEASONAL NORMALS IN THE LOWER TO MIDDLE 80S.
THURSDAY-FRIDAY: NO CHANGES IN THIS PORTION OF THE FORECAST,
WHERE MID-LVL FLOW FLATTENS AND BECOMES WESTERLY. POPS WILL BE
ELEVATED INTO THURSDAY AS A COLD FRONT MAY PASS THROUGH THE
REGION. THERE CONTINUES TO BE GROWING SIGNS OF A SLIGHT COOLDOWN
INTO THE WEEKEND.
AVIATION /00Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 651 PM CDT SAT AUG 8 2026
VFR CONDITIONS ARE EXPECTED TO PREVAIL THE MAJORITY OF THE PERIOD.
SOUTHERLY WINDS WILL REMAIN SLIGHTLY BREEZY AHEAD OF AN APPROACHING
SURFACE LOW. A BRIEF LULL IN THE WINDS AS THE LOW MOVES SOUTHEAST
THROUGH THE REGION AROUND SUNRISE. WINDS WILL THEN BECOME
NORTHEASTERLY BEHIND IT GUSTING TO 15-20 KTS. THERE IS SOME
INDICATION OF A BRIEF ONE TO TWO HOUR WINDOW OF LLWS AS THE LOW
PASSES. THE ONLY TAF SITE WITH A CLEAR ENOUGH SIGNAL TO INCLUDE
WAS KSUX. WILL CONTINUE TO MONITOR THE TRENDS AND UPDATE AS
NECESSARY.
SCATTERED SHOWERS TO ISOLATED THUNDERSTORMS ARE POSSIBLE AFTER
MIDNIGHT TONIGHT. WHILE WIDESPREAD SEVERE WEATHER IS NOT
ANTICIPATED, A STORM OR TWO MAY BECOME STRONG TO SEVERE PRODUCING
WIND GUSTS TO 52 KTS AND HAIL TO THE SIZE OF A QUARTER. RISK AREA
REMAINS ALONG AND NORTH OF HIGHWAY 14 INTO SOUTHWEST MINNESOTA.
STORMS SHOULD BE CLEAR OF THE AREA BY MID-MORNING
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...AJP
DISCUSSION...DUX
AVIATION...AJP
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