textproduct: Sioux Falls

KEY MESSAGES

- Isolated strong to severe storms will be possible Tuesday afternoon into early evening. Ping pong ball sized hail is the primary risk, with a few 50 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.

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 /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1158 AM CDT Tue Jun 23 2026

CU field beginning to expand early this afternoon as a frontal boundary begins to move into the forecast area. We'll continue to see gradual shower and storm development over the next 2-4 hours ahead of this boundary, though coverage remains quite uncertain. A few stronger hail producing storms with 50 mph may be possible.

The front will clear HON/FSD by early evening, with scattered showers and thunderstorms lingering near KSUX deeper into the evening. VFR conditions are likely in this activity with very brief visibility and ceiling reductions in passing storms.

VFR skies and light winds arrive overnight and continue into Wednesday morning.

FSD WATCHES/WARNINGS/ADVISORIES

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