textproduct: Sioux Falls

KEY MESSAGES

- Portions of southeast South Dakota will see a Level 2 of 5 risk for severe storms this evening and again Thursday late afternoon and evening, with lesser risks farther east and south. Large hail and damaging winds are the primary threats, with an isolated tornado also possible.

- Pockets of heavy rainfall in excess of 2 inches are possible today through Thursday. Widespread flash flooding risks are low. However, flood prone areas and locations which received recent heavy rainfall could see isolated impacts.

- While details are far more uncertain, an isolated to scattered severe storm risk will linger into Friday. The greater risks at this time shift southeast into eastern Nebraska, Iowa and far southern Minnesota.

- Temperatures remain in the 80s through the week and rise towards the low 90s by the end of the weekend.

UPDATE

Issued at 455 AM CDT Wed Jun 3 2026

Storms have moved into our far western counties early this morning, but eastward progress will be slow as the instability axis in central SD and only slowly expands east through this morning. Recent HRRR runs show the line maintaining much farther east than other CAMs and given stronger development at the south end of the complex, there may be something to the HRRR trends. Confidence is low, though, so will only maintain low 20-30% pops about as far east of Highway 81 through midday for now.

This trend in the HRRR is also leading to a slower recovery for the afternoon, resulting in a slower and slightly farther west point of initiation along a slowly advancing cold front this evening. While the HRRR is slower/farther west, the latest 3km NAM has trended in the other direction, initiating storms along our western CWA border by 3-4pm with a faster progression to the east than we have seen in other solutions. While this is leading to some uncertainty in exact timing of initiation, the overall location and evolution of storms during the late afternoon and evening remains on track. These initial discrete storms will produce the greatest threat for large hail, perhaps 2 inches or larger, for the first 1-3 hours after development. The storms then evolve into one or more linear segments which will bring a transition to a threat of damaging winds up to 70 mph as the line moves southeast during the evening. Waning instability and decreased shear over Nebraska/Iowa/Minnesota should result in the severe threat diminishing after midnight.

Thursday could see a repeat of today in terms of severe storm timing, but with a couple of glaring differences with regard to evolution. First, the low level focus for storms looks to be residual boundaries from tonight's convection, perhaps more of a west-east oriented quasi-warm front, rather than a southwest to northeast oriented cold front. Second, confidence is much lower regarding where the boundary/boundaries will be located, and thus location of initiation is much more uncertain and is subject to change.

By Friday, the upper level pattern transitions from southwest flow to a more quasi-zonal flow, but embedded waves still look to trigger at least isolated strong to severe storms by mid to late afternoon. As alluded to in the SPC Day 3 outlook, if recovery from Thursday night's MCS is sufficient, a more organized area of development is possible. This potential is currently favored across southeast portions of our forecast area, but like Thursday, details are uncertain and subject to change as we see how storms evolve over the next couple of days.

DISCUSSION

Issued at 148 PM CDT Tue Jun 2 2026

CURRENTS & TONIGHT: Another warm and breezy day continues! Taking a look across the area, mostly clear and quiet conditions persist this afternoon with breezy southeasterly winds. As some lingering isentropic lift continues to progress through the area this afternoon, can't rule out a few spotty diurnally-driven showers to thundershowers. While severe weather is not expected, any festering activity mainly west of I-29 could produce locally heavy downpours and an occasional stroke of lightning. From here, additional showers and weakening thunderstorms will progress through portions of southcentral SD this evening with a shortwave lifting out of the Black Hills. While this activity is not expected to be severe, can't completely rule out up to 40 mph wind gust at times with any stronger activity. Lastly, another warm night is expected with lows mainly upper 50s to low 60s expected.

WEDNESDAY & THURSDAY: Looking into the midweek, could see an additional shower or two linger in our far northwest around daybreak. However, should see most of this activity weaken as it lifts to the northeast. From here, quieter conditions will temporarily return with more seasonal conditions as temperatures as peak in the upper 70s to mid 80s for the day. Looking aloft, we're still on track for additional showers and thunderstorms to develop along/ahead of an approaching cold front by late Wednesday afternoon. With dew points in the low to mid 60s, developing thunderstorm will have access to an decently unstable environment characterized by 1000-2000 J/kg of MLCAPE with about 20-30 kts of shear. With this in mind, a few stronger storms are expected with the main hazards being up to golf ball sized hail and damaging winds up to 65 mph. With currents guidance suggesting instability will gradually weaken with southeastward extent, thinking the greatest threat will be to areas along and west of I-29 from 4pm to 12am. While there could be a lingering severe risk east of I-29 through 3 am with a strengthening nocturnal LLJ, thinking any stronger activity would be isolated at best given the time of day.

Otherwise, scattered showers with isolated thunderstorm could linger across areas east of I-29 through daybreak on Thursday as the front pushes eastwards. Looking into the rest of Thursday, another warm day is ahead with highs mainly in the low to mid 80s. Could see the return of showers and thunderstorms by Thursday evening as an approaching shortwave intersects a lingering cold/stationary boundary draped roughly from northeastern SD into southcentral SD. While areas along and north of I-90 look like the current area of interest, its worth noting that most of this developing activity should lift to east-northeast following the bulk shear vector. Nonetheless, the environment will be very similar to Wednesday's with 1000-1800 J/kg of MLCAPE and 25-35 kts of shear. With this in mind, expect additional chances for up to Ping-pong ball sized hail and 60 mph winds with the strongest activity. Lastly, this activity will continue progressing eastwards overnight with the potential for some additional redevelopment across portions of northwestern IA with a nocturnal LLJ late though confidence isn't as high yet.

FRIDAY ONWARDS: Heading into the extended period, quasi-zonal flow into the weekend will bring another shortwave through the region on Friday. Given how Thursday's event will likely run late, the main question is if the atmosphere can recover in time for the arrival of the next wave. With this in mind, confidence is low in organized severe weather at this time, However, that will be subject to change depending on how things go with the previously mentioned event. Otherwise, heights will build by Saturday with an approaching mid- level ridge keeping precipitation chances at bay through at least late-Sunday as the ridging begins to break down. Lastly, temperatures will begin to trend warmer into the weekend with highs mainly in the mid to upper 80s and low 90s.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1251 PM CDT Wed Jun 3 2026

Clouds will increase this afternoon ahead of an approaching cold front. Thunderstorms are expected to form over central South Dakota between 03.22-0401Z. Some of these storms could be severe producing large hail to 2 inches, wind gusts to 70 mph, and a few tornadoes are possible. Storms will progress across the region this evening, growing upscale into a quasi-linear system with one or more bowing segments. Threat will then switch to mainly winds, but hail and brief tornadoes along the leading edge remain possible. Storms will progress east of the region by Thursday morning.

Ceilings are expected to remain VFR to MVFR except under stronger storms, where IFR and LIFR are possible for brief periods. Winds will be breezy out of the south gusting 22-28 kts, decreasing after sunset. Winds will then be somewhat variable and light through the remainder of the period.

FSD WATCHES/WARNINGS/ADVISORIES

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