textproduct: Sioux Falls

KEY MESSAGES

- Scattered showers and thunderstorms are expected by late afternoon mainly along and east of a Wagner to Howard to Arlington line. A few storms could become severe with up to 2 inch hail and 65 mph wind gusts being the primary hazards.

- Temperatures will remain above average to begin next week but will trend closer to seasonable as the week progresses.

- Chances for rain (30-50%) will remain for next week. Showers and thunderstorms are possible but severe weather is not expected.

UPDATE

Issued at 400 AM CDT Sun May 24 2026

Taking a look across the area, mostly clear conditions continue with lighter surface winds this morning. With elevated dew points, can't completely rule out some patchy fog mainly in our River Valleys. Any patchy develop should gradually erode with a return to mixing this morning after daybreak. Otherwise, the first half of the day will remain quiet as light southerly surface winds increase. This combined with increasing warm air advection will help highs approach the low to upper 80s and potentially low 90s along the James River Valley. The second half of the day is bit less certain. Looking aloft, we're still on track for scattered showers and thunderstorms from the late afternoon into the overnight hours as a few shortwaves pass through the area.

While there are still some differences among the CAMs mainly due to weaker forcing; we'll likely see storms initiate somewhere along the Missouri River Valley between 4-7 pm and gradually spread eastwards during the course of the evening. With an unstable environment characterized by 1500-2000 J/kg of MLCAPE and 35-45 kts of 0-6 km shear, stronger storms could quickly become severe with large hail up to 2 inches (Hen egg sized) and damaging winds up to 65 mph being the primary hazards. This also further supported by steep lapse rates (7.5-8.5 degrees/km) and inverted V soundings. Otherwise, could see additional development across far eastern SD and southwestern MN as a secondary wave catches up to the first which could bring additional chances for stronger storms by late evening (9pm-12 am). Lastly, should see most of this activity exit east of our area between 12am-2am as temperatures decrease into the low to upper 50s for the night.

DISCUSSION

Issued at 218 PM CDT Sat May 23 2026

Quiet conditions persist this afternoon as weak surface ridging remains in place. This will change over the next few hours as weak thunderstorms look to develop along the Missouri River valley. These storms are not expected to be severe as instability values will weak on the order of about 500 J/kg and deep layer shear be modest at about 30 knots. DCAPE will be modest at around 800 J/kg, contributing to the chance for gusty winds. Isolated wind gusts up to 40-50 mph is possible in the weak storms before they dissipate during the late evening timeframe. Low temperatures will fall to 40s to low 50s tonight.

Sunday will be mostly dry during the day as Saturday's upper level wave will push east of the area, promoting subsidence on its backside. The subsidence along with steepening mid level lapse rates from an arriving EML will result in warm temperatures up to the 80s to just about touching 90F. The warmest temperatures look to occur in south central South Dakota. This also looks to be the same area where convection initiates as these high temperatures will come close to reaching convective temperatures and have minimal inhibition. This looks to be along a weak dryline like boundary before spreading eastwards. These storms will push into a much more unstable environment with CAPE values up to around 2,000 J/kg. Though dry air entrainment may lower CAPE values closer to 1,500 J.kg. The low levels will be on the drier side though which looks to result in inverted-v like soundings. Thus, DCAPE values up to 800 to 1,000 J/kg are expected which look to contribute to damaging winds up to about 65 mph. Hodographs reveal generally long and straight shear profiles. Some curvature in the low levels is possible as the low level jet (LLJ) strengthens in the evening. However, with such dry air in place, LCLs will be higher, based near 850 mb. Thus, a tornado threat is not expected. With long mid and upper level shear profiles shown by the hodograph, mid level and upper level venting can occur, which will contribute to a large hail threat with hail up to 2 inches in diameter. 0-6km shear magnitudes of about 40 knots will keep the severe storm threat going into the evening timeframe before nocturnal stabilization and increasing inhibition end severe storm chances. There remains some uncertainty about the coverage of storms though as remaining CIN could prohibit more widespread thunderstorm coverage. At the same time, mid level heights will be rising aloft. In fact, 500 mb heights look to rise about 6dam aloft! This is not as favorable for severe storms though not completely harmful as mesoscale processes can overcome this limitation. Still, something we will continue to monitor. Could see weak showers persist into the night east of I-29. Low temperatures will be on the warmer side, only falling to the 50s to perhaps low 60s overnight.

Warm temperatures continue through Monday as upper level heights continue to build aloft. Highs look to reach up to the 80s about 90F across the area. The warmest temperatures look to occur across central and south central South Dakota. The warmth looks to continue as heights look to continue to rise aloft and stay that way through the entirety of next week. Medium range guidance, along with the ensembles strongly support an omega block pattern aloft. The ridge axis looks to be parked over the central Plains. While the upper level pattern would support warmer temperatures, latest guidance suggests that a surface highs will push into the Great Lakes region and will result in cooler, easterly flow. Thus, high temperatures look to slowly cool from the 80s to low 90s down to the 70s and 80s throughout the week.

Precipitation chances look to remain modest at about 30-50% through the week. These probabilities can change though depending on how the low levels set up. The good news is that this pattern is not expected to result in any appreciable wind shear across the area. Enough low level moisture could result in sufficient instability though, leading to shower and storm chances. The good news is that no organized severe weather threat is expected though non-severe storms remain possible for the week ahead. Continue to monitor the latest forecast for the most up to date information.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1247 AM CDT Sun May 24 2026

Patchy light fog remains possible early this morning as southerly winds will tend to stay fairly light and clouds push off to our east. Still a good bit of uncertainty as to where any fog develops, but it would favor areas with the clearest skies, mainly near and west of a KPQN to KFSD to KYKN line. Widespread fog is not expected and dense fog seems unlikely at this point (<10% chance). Otherwise VFR conditions are expected through the rest of the period.

Widely scattered showers and storms are set to develop late this afternoon into the evening hours. The isolated storm mode that's expected later today means there is low confidence in where storms develop and thus held off on including any mention of TSRA in the TAFs at this time. Perhaps KFSD and KSUX have a slighter higher chance of a storm impact than compared to KHON, but uncertainty remains quite high. Storms that do develop will be capable of 2-inch hail and 50-55 kt wind gusts, with the window for this occurring likely between 24.22Z to 25.06Z.

Southerly winds will generally increase through the day today, with non-thunderstorm wind gusts as high as 20-25 kts south of I-90 this afternoon into the early evening.

FSD WATCHES/WARNINGS/ADVISORIES

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