textproduct: Sioux Falls

KEY MESSAGES

- Patchy, locally dense, fog across northwestern IA through mid morning leads to visibility below one mile at times.

- Near to slightly below normal temperatures continue through the end of the week. A couple passing shower and storm chances continue through the end of the week.

- 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 254 AM CDT Wed Jun 24 2026

Forecast remains on track this morning.

Showers and very isolated storms are continuing to push south and east of the area, lingering near US Hwy 20 and east of IA Hwy 60. These should exit the forecast area by daybreak. Lingering clouds south of I-90 may be a bit slower to clear this morning, but should decrease by mid morning.

For the rest of the day, dry conditions prevail thanks to surface high pressure sliding south. Despite lots of sunshine today, we'll see another cooler than average day with highs in the 70s thanks to CAA and northwesterly flow. This afternoon brings gusts to around 25 mph.

Next wave moves into south central SD and the southern MO Valley late this afternoon through tonight. Can't rule out some sprinkles to isolated showers, but think that precipitation struggles with lack of lower level moisture. Increasing clouds with lows in the 50s.

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 /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 626 AM CDT Wed Jun 24 2026

Patchy and locally dense fog has developed across northwestern IA this morning, mainly along and east of IA State Hwy 60. Fog is reducing visibility to MVFR/IFR conditions, with KSUX as low as 1/4SM at times. Expect conditions to improve through 13-14z.

Outside of fog, conditions remain VFR through the period with some diurnally driven mid level CU this afternoon and evening. Some mid to high clouds are also expected.

Winds today start light and variable, becoming northwesterly with gusts around 20 to 25 knots. Gusts taper down after sunset.

FSD WATCHES/WARNINGS/ADVISORIES

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