textproduct: Sioux Falls

KEY MESSAGES

- Showers and embedded thunderstorms arrive around daybreak this morning and spread eastward through the day. Very isolated strong storm redevelopment is possible this afternoon and evening, with a risk of half dollar sized hail and 60 mph between 1PM and 9PM CDT. - Below normal temperatures continue through mid week before more seasonable temperatures return from late week into the weekend.

- Periodic shower and storm chances continue through this week.

UPDATE

Issued at 255 AM CDT Tue Jun 23 2026

No significant changes to the forecast this morning.

First wave is ejecting out of the Black Hills and into northern NE, with some showers and isolated storms across this area and expect the main area of precipitation to move east into the MO River Valley over the next couple of hours - leading showers/storms are developing ahead of the wave at the time of this discussion. Severe risk with this activity remains very low, even as these storms move east through the later morning hours.

By late morning into early afternoon, surface cold front moves into western portions of the forecast area while the next mid/upper wave move into northern SD and ND. LLJ also slightly strengthens through the day. Ensemble guidance from the ECMWF and GFS have both increased in the probability of CAPE over 1000 J/kg this afternoon/evening, now around 40-70% - highest in both models near and east of I-29. Still differences in both the deterministic and ensembles in how quickly the front moves through and how much we can recover from this morning's convection. SPC Day 1 Marginal (level 1 of 5) risk continues to fit the risk well, given uncertainty. With moderate mid level lapse rates and modest shear, hail to half dollar size remains the main threat with any stronger storm, especially if the greater instability is realized. However, can't rule out an isolated gust to around 60 mph. Think that the timing of the greatest risk is from 1PM to 9PM CDT.

Highs today remain on the cooler side, in the 70s. Showers and storms taper off late tonight from west to east, with lows in the 50s.

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 /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 631 AM CDT Tue Jun 23 2026

Showers and isolated storms this morning along/south of I-90 in SD, which have been reducing visibility to MVFR and lower conditions at times. We'll see additional showers and thunderstorms develop later this morning through the day ahead of a cold front. Guidance is quite varied on exact timing and coverage, so hedged a bit away from prevailing groups, especially toward KHON and KSUX where guidance is more varied. A stronger storm this afternoon and evening could produce hail to the size of half dollars and wind gusts around 50 knots.

Outside of convection, VFR conditions prevail. Winds at times today gust around 20 knots, tapering down late this evening.

FSD WATCHES/WARNINGS/ADVISORIES

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