textproduct: Sioux Falls

KEY MESSAGES

- Isolated sprinkles to showers are possible this afternoon and may continue into the evening.

- Showers and embedded thunderstorms arrive by daybreak Tuesday and spread eastward in the day. Very isolated strong storm redevelopment is possible in the afternoon with a risk of hail. - Below normal temperatures continue through mid week before more seasonable temperatures return from late week into the weekend.

UPDATE

Issued at 841 PM CDT Mon Jun 22 2026

Light scattered showers/drizzle are dissipating this evening as what little elevated instability wanes. Winds are light and variable, but with somewhat persistent cloud cover tonight lows will be on the warm side, in the upper 50s. Overnight, modest to moderate moisture influx will begin to saturate and weakly destabilize the low to mid- levels. Near sunrise Tuesday winds in the boundary layer become southerly as WAA and a weak 25-30 kt LLJ set up over central South Dakota. A series of weak shortwaves will approach out of the west, triggering scattered showers and weak thunderstorms. Severe weather is not anticipated but an isolated stronger thunderstorm could produce 30-40 mph wind gusts. Storms will move east to southeast across the region through the morning.

Some disagreement in guidance about afternoon clouds results in uncertainty in the afternoon forecast. Some guidance shows more substantial clearing ahead of an approaching cold front, while others keep clearing to isolated pockets. Current soundings indicate a modest 500-1000 J/kg MUCAPE. Should the better clearing be realized instability will likely increase. Mid-level lapse rates remain marginal at 6.5 C/km, however 0-6 km bulk shear is roughly 35- 45 kts. This is enough to support a few more organized storms. Considering all this there are two most likely scenarios for Tuesday afternoon. The scenario with less clearing will result in weak showers and isolated thunderstorms capable of producing small hail. The scenario with more clearing could result in thunderstorms, a few of which could become strong to severe. Threats with the high end scenario include hail up to the size of a half dollar and wind gusts to 50 mph. Timing of storms will be mid to late afternoon and into the evening hours Tuesday.

DISCUSSION

Issued at 1256 PM CDT Mon Jun 22 2026

THIS AFTERNOON/EVENING: Isolated to widely scattered sprinkles to showers will persist into early evening, as soundings indicate sharp low-lvl lapse rates and a small pocket of instability. The lack of low-lvl flow would suggest no strong organization to this activity. These sprinkles/showers may linger into the evening given weak perturbations in the mid-lvl flow, but QPF will be minimal.

TONIGHT: Ejecting shortwaves off the Central/Northern Rockies will develop several clusters of convection over the western Dakotas and Nebraska Panhandle this evening. With this activity outrunning most of it's meager instability by midnight, it will begin to cross into the western CWA by daybreak. While a low chance, a few 30 to 40 mph gusts may be possible.

TUESDAY: Showers and embedded thunderstorms move east through the CWA on Tuesday. Eventually by mid-day to the early evening a few pockets of clearing may try to develop along and ahead of a weak cold front drifting eastward. While soundings suggest instability is marginal (700-1000 J/KG), if those larger pockets develop (where the uncertainty in the forecast remains), slightly more unstable airmass could develop. Shear throughout the effective layer supports some storm organization, however mid-lvl lapse rates are marginal. All that said, a continued potential for isolated strong storms with hail will be possible Tuesday afternoon and early evening.

Wednesday: High pressure arriving will lead to a very pleasant and dry Wednesday. Temperatures rise into the middle to upper 70s.

THURSDAY-FRIDAY: Slightly cooler than normal temperatures remain in place for the end of the week as the mid-lvl flow remains westerly. A subtle trough passing through the Central Plains may cast an increase in cloud cover and perhaps a few showers through the MO River valley Thursday . A stronger upper wave ejects to the northeast by Friday bringing with it an increased chance for showers and thunderstorms (60+%) by Friday. Greatest potential appears to be north of I-90, but quiet a bit of variability remains with the track of this wave.

SATURDAY-SUNDAY: The longwave pattern appears to shift for the upcoming weekend, with this pattern amplifying into next week. By Saturday a long wave trough forms over the western third of the CONUS, with an increasing ridge in the southeastern part of the CONUS. Sharpening southwest flow over the Plains will help push both warmer temperatures and increasing convection risks through central Canada and the Northern Plains. Temperatures will also rise back to normal or above normal levels towards the 90 degree mark.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1228 AM CDT Tue Jun 23 2026

Light and variable wind becomes southerly around daybreak and increases ahead of an approaching cold front. Afternoon gusts of 17- 24 kts are expected. Winds become northwest behind the front and decrease.

Showers and isolated thunderstorms are also possible beginning around daybreak over central South Dakota. These weak storms will move southeast through the morning. A short break late morning through early afternoon before the aforementioned cold front enters the region from the northwest. As it progresses to the southeast another round of strong to severe thunderstorms are possible, mainly along and east of the James River Valley. Risks include hail to the size of a half dollar and wind gusts to 50 mph. Storms should exit southeast of the region in the latter part of the period. VFR conditions are expected for the majority of the period. The exception being under any stronger storms where brief periods of MVFR are possible.

FSD WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None. IA...None. NE...None.