textproduct: Sioux Falls

KEY MESSAGES

- Scattered storms continue mainly south of I-90 late this evening. The risk for severe weather is decreasing in our forecast area, but stronger storms may produce locally heavy rain, with small hail and a few 40 mph gusts also possible.

- Near to slightly below normal temperatures continue through the end of the week with passing showers and isolated thunderstorms to the north by early Friday.

- Growing potential for an extended period of heat and humidity beginning Saturday, but intensifying Sunday into next week. Heat and humidity could bring very low probabilities for thunderstorms each day.

UPDATE

Issued at 1035 PM CDT Tue Jun 23 2026

Scattered storms continue to fire on weak boundaries in portions of northwest Iowa and southwest Minnesota this evening. Storms have remained shy of severe limits to this point and should generally weaken as instability decreases through the remainder of the evening. That said, we could see isolated to scattered non-severe storms continue into the overnight as the surface boundary and weak instability axis drift southeast.

Little change to the remainder of the forecast with seasonably cool temperatures mid-week trending upward this weekend through the final days of June next week. Humidity levels look to be on the rise this weekend into early next week as well, and will have to monitor for potential heat headlines.

DISCUSSION

Issued at 1234 PM CDT Tue Jun 23 2026

THIS AFTERNOON/EVENING: Weak frontal boundary continues to drift southeast early this afternoon. Instability continues to slowly grow ahead of this boundary, through latest RAP/HRRR MLCAPE estimates continue to range between 900-1400 J/KG. As we reach convective temps we'll begin to see isolated strong or severe storms by mid- late afternoon. The increase in effective wind shear AOA 40 knots could drive a few slightly more organized storms, however rather marginal mid-lvl lapse rates and tall-thin CAPE profiles may indicate the severe risks may be more limited. Analog soundings would suggest hail up to 1.5" will be possible, with very isolated stronger wind gusts. The latest SSCRAM guidance also points to greater hail than wind risks through the heart of the CWA by mid- late afternoon. The persistent dPVA this evening along with flattening of the surface front may keep scattered showers and embedded thunderstorms going along or south of I-90 through the evening and into the early overnight hours (along Highway 20). The severe weather risk should diminish quickly by 7-8PM however.

TONIGHT: A light wind will persist for most of the region overnight, with a slightly increased northwest wind developing by daybreak Wednesday.

WEDNESDAY-THURSDAY: A pair of quiet days, with cooler temperatures can be expected for Wednesday and Thursday as surface ridging moves through the region. Variable afternoon CU may develop through the region Wednesday afternoon as highs climb into the middle to upper 70s. Light and variable winds may lead to patchy fog Thursday morning, though we'll watch for some high level clouds drifting northward into the MO river valley Thursday morning. This cloud cover will be tied to a low-lvl baroclinic zone stretching from the Black Hills region towards the Omaha area. Temperatures once again remain in the middle to upper 70s.

FRIDAY: A stronger mid-lvl wave ejects out of the Central and Northern Rockies early Friday. The 00Z ECE/EC continued to be focused further south than the GEFS/GFS/CMC/CME/NAM with the track of this wave, associated warm advection, and greatest potential for light QPF. That said, the probability for more than 0.10" is no more than 20-30% in any solution. By Friday afternoon, the advancement of a warm front and increasing EML should lead to only minor risks for redevelopment by the evening over central South Dakota.

SATURDAY-MONDAY: A general pattern evolution towards western CONUS troughing and southeastern CONUS ridging develops quickly Saturday. This pattern will signal a shift towards much warmer temperatures, stronger EML development, and convection risks generally driven by the need for a triggering mechanism to overcome the inhibition. More impactful will be the arrival of very warm temperatures. Temperatures Saturday rise toward the middle to upper 80s, however highs will accelerate upwards Sunday and Monday into the 90s. Latest NBM/LREF indicate high probabilities (>70) of exceeding 90 degrees with >30-50% probabilities of exceeding 95 degrees Sunday. One thing to be aware of is the warm bias in GFS and GEFS surface temperatures as we move through next week which could skew blends slightly and present some pretty unrealistic high temperature/CAPE projections.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 642 PM CDT Tue Jun 23 2026

A cluster of storms will continue to move across portions of southwest Minnesota early this evening, with a low (30-40%) chance for additional development from northeast Nebraska into northwest Iowa prior to 24/06Z. Will keep a small window of TS potential at KSUX this evening, but overall storm chances at TAF sites are low.

VFR conditions will prevail through the period, though storms may produce locally IFR conditions and erratic wind gusts to 35-40kt. Away from storms, southwest winds at or below 12kt will turn to the west and northwest, with occasional gusts 20-25kt Wednesday afternoon.

FSD WATCHES/WARNINGS/ADVISORIES

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