textproduct: Sioux Falls

KEY MESSAGES

- Temperatures remain below normal for the rest of the work week. Departures from normal will average 5 to 8 degrees below normal.

- Outside of two light rain chances early Wednesday and Thursday night, much of the 7 day forecast is dry.

- Temperatures this weekend into early next week rise well above normal with highs well into the 90s in most locations. Heat related headlines may be needed at times this weekend.

UPDATE

Issued at 920 PM CDT Tue Jul 21 2026

Forecast remains on track this evening with no significant changes planned. Main question over the next 12-18 hours will be how far northeast light rain can develop into a deep sub-cloud dry layer. Latest high-res models continue to focus chances for measurable rain southwest of a Huron-Sioux Falls-Ida Grove line with the better chances from south-central South Dakota into northeast Nebraska, mainly near and south of the Missouri River.

Coolest temperatures tonight will be in our eastern areas where skies will remain mostly clear (aside from upper level wildfire smoke) much of the night. Current dew points in the lower-mid 50s and light/variable winds will allow for decent radiational cooling, though the smoke layer may prevent optimal cooling. Still anticipate lows in the mid 50s over southwest Minnesota, ranging up to lower 60s where clouds will be more prevalent in our southwest counties.

DISCUSSION

Issued at 1252 PM CDT Tue Jul 21 2026

THIS AFTERNOON: Plenty of cool air aloft has poured southward into the region, with morning strato-cu continuing to slowly mix upwards. High temperatures given the cloud cover will remain in the upper 70s to lower 80s. Aloft, the increasing northwesterly flow could bring high level smoke though the region into the night.

TONIGHT: Surface high pressure drifts into the Midwest and western Great Lakes region overnight. Winds turn light and variable which, may lead to fairly cool overnight lows in areas east of the James River. The low-lvl airmass is fairly dry, so fog probabilities will remain very localized to sheltered valleys and riverways. Further west, high level clouds increase after midnight as mid- lvl warm advection focuses over the West River areas and the Nebraska panhandle. A few sprinkles to light rain showers may reach the central portions of SD into the James River valley by daybreak.

WEDNESDAY: A subtle shortwave drops southeast from the Black Hills region across central Nebraska during Wednesday. Much of the CWA will remain under the influence of low-lvl dry air advection from the northeast during the day. While mid-lvl lift spread east towards the I-29 corridor, most guidance struggles to produce more than sprinkles east of I-29, with the best low-lvl saturation focused along and south of the MO River valley. Any QPF that falls will be light. The most impact from this system may be increased cloud cover and temperatures in the 70s and 80s.

THURSDAY: After another night with variable cloud cover, light winds, and cooler temperatures, Thursday will see surface winds return back to the South early in the day. We'll be watching another slightly stronger wave cross the Rockies during the day on Thursday. Model guidance has been a bit all over with this wave, with the GFS and about 40% of it's ensemble members stubbornly further to the NE than all of the other major model guidance. The ECMWF/ICON/GEM/UKMET and to some degree NAM force this wave further southeast bringing the majority of rain chances to western SD, central and northern NE and western Iowa. The latest NBM has hedged a bit more towards the drier solutions as more drier input is received, and I continue to favor the greatest focus for rain along the MO River valley. That said, if there is some shift towards the outlier solutions, moisture convergence could be enough to at least produce some meaningful rain into Thursday night.

FRIDAY-MONDAY: A 600 DM ridge builds through the Central Plains heading into the upcoming weekend. This ridge, unlike the past weeks, it a bit more suppressed which may serve to delay the most intense heat into the second half of the weekend. Temperatures are likely to surge into the 90s Saturday and Sunday with initial focus for the hottest temperatures west of the James River Saturday and then further east Sunday. Even with the slightly warm biased NBM, there is some potential for heat related headlines this weekend. Convection chances remain low for Saturday, but may rise slightly on the edge of the EML late Sunday. A very hot Monday is also possible with a similar setup for weak flow convection on the edge of the EML in the afternoon evening.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 650 PM CDT Tue Jul 21 2026

Lingering scattered 5-6kft AGL clouds and northerly wind gusts will subside with sunset. Additional mid-high level clouds will expand east overnight into Wednesday, with variable light winds (at or below 10kt).

Light rain showers/sprinkles may accompany the thicker mid-level clouds through portions of the James and Missouri River Valleys late tonight into early Wednesday afternoon, with better chances remaining south/west of our TAF locations. Conditions within any showers should remain VFR with no thunder expected.

FSD WATCHES/WARNINGS/ADVISORIES

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