516
FXUS63 KFSD 021852
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
152 PM CDT SUN AUG 2 2026
KEY MESSAGES
- PATCHY VALLEY FOG IS AGAIN POSSIBLE TONIGHT, MAINLY ACROSS
PARTS OF NORTHWEST IOWA. ANY FOG THAT DOES DEVELOP SHOULD
BURN OFF BY MID MORNING.
- DRY CONDITIONS AND SEASONABLY WARM TEMPERATURES CONTINUE INTO
MID-AFTERNOON MONDAY.
- SHOWER AND STORM CHANCES RETURN MONDAY NIGHT INTO WEDNESDAY.
AN ISOLATED STRONG TO SEVERE STORM IS POSSIBLE IN PORTIONS OF
SOUTHEAST SOUTH DAKOTA MONDAY EVENING, IF STORMS CAN DEVELOP.
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 MONDAY/
ISSUED AT 1232 PM CDT SUN AUG 2 2026
VFR CONDITIONS ARE EXPECTED FOR THE TAF PERIOD. LIGHT SOUTHEASTERLY
WINDS BEGIN THE TAF PERIOD. THE SOUTHEASTERLY WINDS WILL REMAIN
ELEVATED THROUGH THE OVERNIGHT HOURS AS THE LOW LEVEL JET (LLJ)
STRENGTHENS ALOFT. THIS WILL RESULT IN LOW LEVEL WIND SHEAR (LLWS)
FOR LOCATIONS ALONG AND WEST OF THE JAMES RIVER TONIGHT. THE LLWS
WILL COME TO AN END IN THE MORNING HOURS BUT BREEZY SOUTHERLY WINDS
WITH GUSTS UP TO 20-35 KNOTS WILL END THE PERIOD.
ISOLATED VALLEY FOG IS POSSIBLE TONIGHT MAINLY ACROSS PARTS OF
NORTHWEST IOWA WHERE WINDS ARE WEAKEST.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...MEYERS
AVIATION...MEYERS
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