944
FXUS63 KFSD 031735
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1235 PM CDT MON AUG 3 2026
KEY MESSAGES
- DRY AND SEASONABLY WARM THROUGH THIS AFTERNOON. BREEZY SOUTH
WINDS GUST 30 TO 40 MPH, HIGHEST WEST OF I-29.
- SHOWER AND STORM CHANCES RETURN LATER TODAY THROUGH TONIGHT.
ISOLATED STRONG TO SEVERE STORMS ARE POSSIBLE IN PORTIONS OF
SOUTHEASTERN SOUTH DAKOTA AND FAR WESTERN MINNESOTA LATER THIS
EVENING. WIND GUSTS TO 65 MPH AND QUARTER SIZED HAIL ARE THE
MAIN THREATS.
- COOLER TEMPERATURES MID WEEK WITH SCATTERED SHOWERS AND
STORMS. SEASONAL TEMPERATURES RETURN LATE WEEK, WITH LOW AND
UNCERTAIN RAIN CHANCES INTO THE WEEKEND.
UPDATE
ISSUED AT 334 AM CDT MON AUG 3 2026
PLEASANT AND WARM START TO THE MORNING, ALBEIT A BIT BREEZY WITH
SOUTHERLY WIND GUSTS 25-30 MPH. WINDS ARE LIGHT ACROSS NORTHWESTERN
IA, SO MAY SEE SOME BRIEF AND EXTREMELY PATCHY FOG TOWARD/EAST OF
THE US HWY 59 CORRIDOR. WITH COMPRESSING SPG AHEAD OF THE SURFACE
COLD FRONT, EXPECT WIND GUSTS TODAY AROUND 30-40 MPH, WITH A FEW
ISOLATED HIGHER GUSTS WEST OF I-29. SEASONAL CONDITIONS PREVAIL.
NO SIGNIFICANT CHANGES TO THE SHORT TERM FORECAST. MINOR ADJUSTMENTS
TO THE DAY 1 SPC OUTLOOK, SHIFTING THE MARGINAL (LEVEL 1 OF 5) RISK
BACK TO THE WEST SLIGHTLY. BIGGEST CHALLENGE IN THE SHORT TERM
REMAINS THE TIMING AND DEVELOPMENT OF CONVECTION WITH THE SURFACE
FRONT AND THE TRAILING WAVE AS WELL AS HOW MUCH WE DESTABILIZE. SOME
OF THE LATEST GUIDANCE INDICATES THAT THERE MAY STILL BE A MODEST
CAP IN PLACE (ESPECIALLY LOOKING AT SOUNDINGS), AND THAT INSTABILITY
AND SHEAR MAY BE OFFSET SLIGHTLY THROUGH THE EVENING HOURS. THERE
MAY BE A NARROW WINDOW THIS EVENING FROM 7 PM THROUGH MIDNIGHT WHERE
STRONG TO SEVERE STORMS (LIKELY ELEVATED STORMS) MAY PRODUCE WIND
GUSTS TO 65 MPH AND QUARTER SIZED HAIL IN THE WESTERN PARTS OF OUR
FORECAST AREA.
SHOWERS AND STORMS MAY BECOME MORE WIDESPREAD THROUGH THE OVERNIGHT
HOURS AS THE MID/UPPER LEVEL WAVE AND FRONT MOVE IN, PROVIDING THE
SYNOPTIC SUPPORT. HOWEVER, DECREASING INSTABILITY AND STILL SLIGHTLY
OFFSET SHEAR SHOULD LIMIT SEVERITY AS STORMS CONTINUE TO PRESS EAST
OVERNIGHT INTO EARLY TUESDAY.
DISCUSSION
ISSUED AT 151 PM CDT SUN AUG 2 2026
CLEAR SKIES PERSIST ACROSS THE AREA THIS AFTERNOON AS HIGH
TEMPERATURES HAVE WARMED TO THE 80S. WINDS REMAIN MORE ON THE BREEZY
SIDE, MAINLY FOR LOCATIONS ALONG AND WEST OF THE JAMES RIVER WHERE
GUSTS UP TO 20-30 MPH ARE BEING OBSERVED. WINDS WILL WEAKEN SOME
THROUGH THE EVENING HOURS BUT REMAIN ELEVATED OVERNIGHT AS AN UPPER
LEVEL WAVE BEGINS TO EJECT INTO THE NORTHERN PLAINS, STRENGTHENING
THE LOW LEVEL JET (LLJ). THE LLJ WILL ALSO KEEP LOW TEMPERATURES ON
THE WARM SIDE WITH LOWS ONLY FALLING TO THE 60S TO LOW 70S
OVERNIGHT. PATCHY VALLEY FOG IS POSSIBLE AGAIN TONIGHT THOUGH
NORTHWEST IOWA WILL HAVE THE BEST POTENTIAL FOR FOG AS WINDS WILL BE
WEAKEST THERE.
MONDAY WILL BE A WARMER DAY AS HIGH TEMPERATURES WARM TO THE 80S AND
90S. WITH WILL REMAIN BREEZY WITH GUSTS UP TO 35 MPH EXPECTED DURING
THE AFTERNOON TIME FRAME. A COLD FRONT WILL BE PUSHING INTO THE AREA
FROM THE WEST BY THE LATE AFTERNOON AND EARLY EVENING TIMEFRAME.
THIS FRONT MAY HAVE THE POTENTIAL TO DEVELOP SHOWERS AND
THUNDERSTORMS. HOWEVER, STEEP MID LEVEL LAPSE RATES WILL YIELD A
STOUT CAPPING INVERSION. THERE ALSO LOOKS TO BE MID TO HIGH LEVEL
CLOUDS SITUATED ABOVE THE FRONT THROUGHOUT THE DAY ON MONDAY THAT
COULD RESULT IN SLIGHTLY COOLER TEMPERATURES. THAT SAID, BOTH THE
HREF AND REFS HAVE DECREASED THEIR PROBABILITIES FOR A STRONG CAP TO
REMAIN IN PLACE. THEY NOW SHOW A 40-70% CHANCE FOR CONVECTIVE
INHIBITION (CIN) TO REMAIN AT -50 J/KG OR LESS. THIS SUGGESTS THAT
THE CAP COULD BE WEAK ENOUGH FOR ONE OR TWO STORMS TO DEVELOP ALONG
THE COLD FRONT AS IT PUSHES INTO THE MISSOURI RIVER VALLEY. THIS
POTENTIAL IS STILL UNCERTAIN AS THE LATEST 12Z HI-RES GUIDANCE SHOWS
SOME VARIANCE IN STORMS DEVELOPING ALONG THE FRONT. THIS MAY BE A
SCENARIO WHERE STORMS DEVELOP IN THE EVENING ALONG THE ELEVATED
PORTION OF THE COLD FRONT WHERE CIN WILL BE LESS. SHOULD STORMS
DEVELOP, THEY CONTINUE TO LOOK TO BE JUST AHEAD OF THE STRONGER
VERTICAL SHEAR. STILL NOT OUT OF THE QUESTION FOR THESE ISOLATED
STORMS TO BE STRONG TO SEVERE. EFFECTIVE SHEAR VALUES LOOK TO BE ON
THE ORDER OF ABOUT 40 KNOTS WHILE MIN TO MAX THETA-E DIFFERENCE
VALUES WILL BE DOWN TO ABOUT -15K. THUS, LARGE HAIL UP TO THE SIZE
OF HALF DOLLARS AND DAMAGING WINDS TO 60 MPH WILL BE POSSIBLE IF THE
ISOLATED STORMS DO DEVELOP. CHANCES FOR STRONG TO SEVERE STORMS WILL
BE WANING INTO THE OVERNIGHT HOURS BUT RAIN SHOWERS LOOK TO PERSIST
THROUGH THE NIGHT ALONG THE ELEVATED FRONT.
THE SURFACE FRONT WILL PUSH THROUGH THE FORECAST AREA DURING THE
OVERNIGHT HOURS. HOWEVER, THE ELEVATED FRONT WILL REMAIN OVER MAINLY
NORTHWEST IOWA FOR THE DAY. THIS IS WHERE THE BULK OF THE RAIN IS
EXPECTED TO FALL. THE RAIN AND CLOUD COVER WILL KEEP HIGH
TEMPERATURES ON THE COOL SIDE WITH HIGHS ONLY REACHING UP TO THE
70S. THE RAIN WILL PERSIST THROUGH THE ENTIRETY OF TUESDAY AND
THROUGH WEDNESDAY MORNING BEFORE PUSHING SOUTHEAST OF THE AREA. THE
ENSEMBLES CONTINUE TO SHOW MODERATE TO HIGH PROBABILITIES BETWEEN A
50-80% CHANCE FOR RAINFALL AMOUNTS TO EXCEED A TENTH OF AN INCH.
THEIR PROBABILITIES DECREASE TO 0-40% AND ARE CONCENTRATED ALONG AND
SOUTH OF HIGHWAY-20. THUS, LIGHT RAINFALL AMOUNTS OF A TENTH OF AN
INCH TO POSSIBLY EXCEEDING A QUARTER OF AN INCH IS MOST LIKELY AT
THIS TIME.
WITH LINGERING CLOUD COVER AROUND, WEDNESDAY WILL BE ANOTHER COOL
DAY WITH HIGHS ONLY WARMING TO THE 70S. BROAD TROUGHING WILL WILL
RESIDE OVER THE NORTHERN PLAINS FOR THE BACK HALF OF THE WEEK AND
NEXT WEEKEND. TEMPERATURES LOOK TO WARM BACK TO NEAR SEASONABLE IN
THE 80S TO POTENTIALLY 90S EACH DAY. THERE COULD POTENTIALLY BE MORE
CHANCES FOR RAIN BUT THESE CHANCES ARE UNCERTAIN FOR NOW.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 1230 PM CDT MON AUG 3 2026
SCATTERED THUNDERSTORMS WILL DEVELOP AROUND THE JAMES RIVER
VALLEY AFTER ABOUT 3Z THIS EVENING. A FEW OF THESE WILL BE
STRONG TO SEVERE. AS THEY PROGRESS EAST LATER THIS EVENING AND
EARLY OVERNIGHT THE STRENGTH SHOULD WANE. ADDITIONAL SHOWERS ARE
EXPECTED THROUGHOUT THE DAY ON TUESDAY, WITH THE BETTER CHANCES
SOUTH OF I-90. OUTSIDE OF ANY SHOWERS AND THUNDERSTORMS, VFR
CONDITIONS ARE EXPECTED.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...MEYERS
AVIATION...08
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