397
FXUS63 KFSD 210805
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
305 AM CDT TUE JUL 21 2026
KEY MESSAGES
- COOLER TEMPERATURES AND LOWER HUMIDITY ARE EXPECTED FOR THE
REST OF THE WORK WEEK, WITH TEMPERATURES CLIMBING BACK TO THE
90S NEXT WEEKEND.
- THE MAJORITY OF THIS WEEK WILL BE DRY. POSSIBLE EXCEPTIONS MAY
BRING LIGHT SHOWERS TO PORTIONS OF THE MISSOURI RIVER VALLEY
TUESDAY NIGHT-WEDNESDAY, WITH A BROADER 30-50% CHANCE OF SHOWERS
OR A FEW NON-SEVERE STORMS LATE THIS WEEK.
UPDATE
ISSUED AT 305 AM CDT TUE JUL 21 2026
TAKING A LOOK ACROSS THE AREA, QUIETER CONDITIONS PERSIST THIS
MORNING AS COOLER AIR CONTINUES TO FUNNEL IN BEHIND YESTERDAY'S COLD
FRONT. FROM HERE, EXPECT THE QUIETER CONDITIONS TO PERSIST FOR THE
DAY WITH HIGHS ONLY PEAKING IN THE MID 70S TO MID 80S WITH NORTHERLY
SURFACE WINDS AND LINGERING COLD AIR ADVECTION (CAA) IN PLACE ALOFT.
OTHERWISE, WE'LL CONTINUE TO SEE SOME WILDFIRE SMOKE ALOFT AS WELL
MAINLY ALONG AND WEST OF THE JAMES RIVER VALLEY WITH LIMITED SURFACE
IMPACTS. LASTLY, THE FORECAST REMAINS ON TRACK FOR A FEW SCATTERED
SHOWERS ALONG THE MISSOURI RIVER VALLEY TONIGHT AS A WEAK WAVE
SLIDES THROUGH. WHILE SEVERE WEATHER IS NOT EXPECTED, POCKETS OF
MODERATE RAINFALL WILL BE POSSIBLE ALONG WITH AN OCCASIONAL RUMBLE
OF THUNDER.
DISCUSSION
ISSUED AT 125 PM CDT MON JUL 20 2026
THIS AFTERNOON: A COOL FRONT CONTINUES TO PUSH SOUTHEAST THROUGH
THE FORECAST AREA EARLY THIS AFTERNOON. BEHIND THE FRONT, ELEVATED
MOISTURE MAY CONTINUE TO PRODUCE ISOLATED SHOWERS OR THUNDERSTORMS
DRIVEN BY A NARROW CORRIDOR OF VORTICITY SINKING THROUGH CENTRAL
MINNESOTA. THIS ACTIVITY IS LIKELY TO REMAIN ELEVATED AS IT MOVES
INTO SOUTH CENTRAL MINNESOTA. EVENTUALLY IT MAY BECOME MORE SURFACE
BASED AS IT MOVES INTO NORTHERN IOWA. SECONDARY ACCAS OR ISOLATED
THUNDERSTORMS FURTHER WEST INTO CENTRAL SOUTH DAKOTA ARE EXPECTED
TO CONTINUE TO STRUGGLE SOUTHEAST. ELSEWHERE, MOISTURE POOLING
AHEAD OF THE BOUNDARY ALONG WITH THERMAL COMPRESSION AHEAD OF THE
FRONT WILL PUSH HEAT INDEX VALUES INTO THE 100S ALONG AND SOUTH OF
I-90 THIS AFTERNOON. DRIER AIR ADVECTING BEHIND THE PASSAGE OF
THE FRONT SHOULD LEAD TO DROPPING HEAT INDEX VALUES AFTER 3PM FROM
NORTH TO SOUTH, WITH ALL HEADLINES ON SCHEDULE TO END BY 7-8PM.
THE SOUTHWARD PROGRESSION OF THE BOUNDARY WILL CONTINUE INTO THE
EVENING REACHING A LINE FROM NORFOLK TO SIOUX CITY TO ESTHERVILLE BY
4-5PM. SOUNDINGS ALONG THE BOUNDARY CONTINUE TO LOOK VERY CAPPED,
WITH MUCH LESS FORCING GENERALLY EXPECTED OVER THE FRONT. IT'S THE
ACCAS OVER CENTRAL SD THAT WE'LL NEED TO KEEP AN EYE ON EARLY THIS
EVENING, AS IT DOES HAVE SOME POTENTIAL TO INTENSIFY SLIGHTLY AS IT
REACHES HIGHWAY 20 AND COULD BECOME SURFACE BASED. IF UPSCALE
GROWTH COULD HAPPEN, THE COMBINATION OF SHEAR AND INSTABILITY
COULD SIGNAL SOME GOLF BALL SIZED HAIL AND 60 MPH WINDS. AGAIN
THOUGH, THIS LOOKS LIKE A VERY LIMITED AREA IN TIME AND SPACE
THIS EVENING.
TONIGHT: DEW POINTS WILL CRASH OVERNIGHT, SIGNALING A RETURN OF
COOLER AND DRIER AIR. OVERNIGHT LOWS MAY FALL WELL INTO THE 60S BY
DAYBREAK TUESDAY.
TUESDAY: A BEAUTIFUL DAY IS ANTICIPATED ON TUESDAY WITH CANADIAN
HIGH PRESSURE SINKING SOUTHWARD. HIGH TEMPERATURES ONLY IN THE
UPPER 70S TO LOWER 80S WITH DEW POINTS IN THE 50S WILL SIGNAL A
GREAT.
WEDNESDAY-FRIDAY: THE SEMI-NORTHWEST FLOW THROUGH THE SECOND HALF
OF THE WEEK WILL KEEP COOLER TEMPERATURES IN THE REGION THROUGH THE
REST OF THE WEEK. HIGHS ARE EXPECTED TO REACH THE LOWER 80S EACH
DAY. A WEAK PERTURBATION IN THIS FLOW PATTERN LEAVES THE CENTRAL
ROCKIES EARLY WEDNESDAY. MOST GUIDANCE TRACKS THIS WAVE THROUGH
NEBRASKA, BUT A FEW SOLUTIONS COULD BRING LIGHT RAIN RISKS INTO MID-
DAY WEDNESDAY ALONG AND WEST OF THE JAMES RIVER VALLEY. A SECOND
WAVE ARRIVES BY THURSDAY NIGHT INTO FRIDAY, BUT AGAIN, UNCERTAINTY
IN TRACK KEEPS THE RISKS FOR ANY PRECIPITATION LESS THAN 30% IN MOST
LOCATIONS ALONG OR WEST OF I-29.
SATURDAY-SUNDAY: WE'LL AGAIN SEE RISING TEMPERATURES BY NEXT
WEEKEND, AS CONFIDENCE IS HIGH IN AN EXPANDING MID-LVL RIDGE THROUGH
THE PLAINS. THIS RIDGE HOWEVER WILL BE MORE SUPPRESSED THAN THE
ONE THAT HAS JUST LEFT THE REGION, SIGNALING A SHORTER SURGE IN
TEMPERATURES TO THE 90S/100S, BUT ALSO ALLOWING A RIDGE RIDER
OR TWO TO MOVE THROUGH THE PLAINS BY THE END OF THE WEEKEND.
AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 1207 AM CDT TUE JUL 21 2026
VFR CONDITIONS ARE EXPECTED THROUGH THIS TAF PERIOD WITH A BROAD
AREA OF WILDFIRE SMOKE REMAINING MOSTLY ALOFT.
NORTH-NORTHWEST WIND GUSTS 20-25KT DEVELOP SHORTLY AFTER SUNRISE
TUESDAY, WITH GUSTS QUICKLY DIMINISHING BY SUNSET TUESDAY EVENING.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...05
DISCUSSION...DUX
AVIATION...JH
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