902
FXUS63 KFSD 030152
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
852 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. BREEZY SOUTH WINDS WILL BE GUSTING 25-35
MPH WITH SOME 40 MPH GUSTS POSSIBLE WEST OF THE JAMES RIVER
VALLEY.
- SHOWER AND STORM CHANCES RETURN MONDAY NIGHT AND CONTINUE INTO
WEDNESDAY. AN ISOLATED STRONG TO SEVERE STORM IS POSSIBLE IN
PORTIONS OF SOUTHEAST SOUTH DAKOTA MONDAY EVENING, IF STORMS
CAN DEVELOP.
UPDATE
ISSUED AT 850 PM CDT SUN AUG 2 2026
THE REST OF THIS EVENING WILL BE PLEASANT AND DRY, BUT ON THE BREEZY
SIDE WITH SOUTH WINDS GUSTING 20-25 MPH. LOWS TONIGHT WILL FALL TO
THE 60S. SOME VALLEY FOG IS POSSIBLE, MAINLY OVER NORTHWEST IOWA
WHERE WINDS WILL BE LIGHTEST. HOWEVER, CONFIDENCE THAT WINDS WILL
BECOME CALM ENOUGH FOR FOG IS LOW. UPPER LEVEL CLOUDS WILL FLOW IN
FROM THE WEST AHEAD OF AN INCOMING COLD FRONT. AS THE COLD FRONT
APPROACHES MID-MORNING WINDS WILL BEGIN TO INCREASE AND SPREAD EAST.
REGION WIDE GUSTS OF 25-35 MPH ARE EXPECTED WITH THE STRONGEST WINDS
ALONG AND WEST OF THE JAMES RIVER VALLEY IN THE AFTERNOON. HERE
OCCASIONAL GUSTS TO 40 MPH ARE POSSIBLE. WINDS DECREASE THROUGH
THE EVENING MONDAY BUT REMAIN BREEZY THROUGH THE OVERNIGHT.
MONDAY DURING THE DAY CONDITIONS WILL BE DRY AND WARM WITH HIGHS IN
THE 80S AND 90S. SKIES WILL BE PARTLY CLOUDY AND HAZY FROM WILDFIRE
SMOKE. MONDAY AFTERNOON THE COLD FRONT AND SURFACE LOW PRESSURE
SYSTEM WILL BE POSITIONED OVER CENTRAL SOUTH DAKOTA. AS THIS
PROGRESSES EAST SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE
POSSIBLE THROUGH THE OVERNIGHT. STRENGTH OF STORMS IS IN QUESTION
DUE TO A WELL CAPPED ENVIRONMENT. HOWEVER, SHOULD ONE LIFT OFF THE
850-700 MB ELEVATED FRONT IT COULD BECOME STRONG TO SEVERE. PRIMARY
THREATS ARE WIND GUSTS TO 65 MPH AND POSSIBLY MARGINALLY SEVERE HAIL
TO THE SIZE OF A QUARTER. AS THE MAIN UPPER WAVE PIVOTS OVER THE
REGION SHOWERS AND THUNDERSTORMS CONTINUE THROUGH THE DAY TUESDAY.
THESE LOOK TO REMAIN MOSTLY SOUTH OF I-90 AND OVER NORTHWEST IOWA.
TUESDAY EVENING HAS RENEWED CHANCES FOR SHOWERS AND THUNDERSTORMS AS
ANOTHER SHORTWAVE PIVOTS THROUGH THE REGION. CURRENTLY THE BEST
DYNAMICS ARE LOCATED TO THE SOUTHEAST OF THE REGION OVER IOWA.
THEREFORE SEVERE STORMS RISKS FOR OUR CWA TUESDAY EVENING ARE LOW. A
THIRD, SLIGHTLY DEEPER SHORTWAVE PIVOTS THROUGH THE REGION WEDNESDAY
EVENING. ONCE AGAIN THE BEST DYNAMICS ARE TO THE SOUTH AND EAST OF
OUR CWA, AND CONFIDENCE IN SEVERE WEATHER IS LOW.
PERSISTENT CLOUD COVER AND COLD AIR ADVECTION ON NORTHERLY
WINDS BEHIND THE FRONT WILL KEEP HIGH TEMPERATURES FOR BOTH
TUESDAY AND WEDNESDAY ON THE COOL SIDE OF CLIMATOLOGY, IN THE
70S.
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 /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 614 PM CDT SUN AUG 2 2026
VFR CONDITIONS ARE EXPECTED THROUGH THIS PERIOD. SOUTHERLY WINDS
GUSTING 17-27 KTS WILL EXPAND EAST INTO MINNESOTA AND IOWA THROUGH
THE OVERNIGHT. SHORTLY AFTER SUNRISE WINDS WILL INCREASE AHEAD OF AN
APPROACHING COLD FRONT. SOUTHERLY GUSTS OF 20-30 KTS WILL BE
WIDESPREAD ACROSS THE REGION. THE HIGHEST GUSTS ARE EXPECTED ALONG
AND WEST OF THE JAMES RIVER VALLEY WHERE THEY COULD REACH UP TO
37 KTS. WINDS BEGIN TO DECREASE NEAR THE END OF THE PERIOD. AT
THE SAME TIME THE COLD FRONT SHOULD BE ENTERING CENTRAL SOUTH
DAKOTA TURNING WINDS TO THE NORTH.
DIRECTIONAL LLWS IS EXPECTED FOR AREAS ALONG AND WEST OF THE JAMES
RIVER BEGINNING AROUND MIDNIGHT AND CONTINUING UNTIL SHORTLY AFTER
DAYBREAK SUNDAY. SPORADIC SHEAR IS ALSO POSSIBLE AS THE COLD FRONT
PASSES. HOWEVER, CONFIDENCE WAS TOO LOW TO INCLUDE AT ANY OF THE TAF
SITES AT THIS TIME.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...AJP
DISCUSSION...MEYERS
AVIATION...AJP
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