textproduct: Sioux Falls

KEY MESSAGES

- Periods of light to moderate showers will return by Friday bringing beneficial rainfall to the area. While exact amounts are uncertain, there is growing confidence in half an inch or greater for most areas.

- Below normal temperatures will continue through Saturday before warmer conditions return from Sunday onwards.

UPDATE

Issued at 855 PM CDT Wed May 20 2026

The forecast remains on track with any lingering sprinkles to very light showers being thwarted by a dry sub-cloud layer according to soundings. Besides the lingering cloud cover, tonight should be mostly quiet as temperatures approach the low 40s for the night. Looking into Thursday, still looking quiet for most of the day as temperatures reach the low to upper 60s. We'll start to see an increase in cloud cover overnight from south to north as warm air advection (WAA) strengthens ahead of our next wave/rain chances. Overall, no significant changes in the forecast have been noted besides the NBM catching up on the QPF side of things. With this in mind, many areas are still on track to receive upwards of 0.50" to 0.75" of an inch of rain during the day on Friday with the potential for isolated pockets of up to 1.00+" west of I-29. Lastly, make sure to plan for the wet and dreary conditions as most of this activity won't be out of our areas until late evening.

DISCUSSION

Issued at 1257 PM CDT Wed May 20 2026

A weak wave and mid level moisture around the dgz moves in tonight, bringing a small threat for showers. Most locations will see a fairly stout dry layer below the incoming moisture which will severely limit rainfall potential. One exception may be west of the James River late this afternoon and early this evening when a little weak instability develops during peak heating which could support isolated showers there.

Lift and very weak instability moves in on Thursday ahead of the next wave. The chances for rainfall remains very limited with this. Otherwise expecting partly to mostly cloudy skies and highs in the 60s.

Thursday night into Friday will see warm advection and upper level support spread into the area. Most of Thursday night will see the better chances remain to the south of the Missouri River, but after midnight chances will increase. For the most part, showery and very isolated thunderstorms will be instability driven near and east of I- 29, while west of I-29 better upper level support for rainfall will be the driving factor. While the convective portion is of course a little less predictable, assuming some convective component does develop a few locations could see 1-2" of rain. Many of the latest models are each indicating swaths about 20-40 miles wide of 1-2" amounts. What also appears to be fairly consistent is that especially west of Highway 81 is where the most consistent suggestions for a more widespread quarter to three quarters of an inch of rain is possible.

Most of the lift will drift northeast on Saturday with a few sprinkles possible in the morning. Otherwise a mild day with highs most in the 60s to lower 70s.

Model soundings hinting at some weak, surface based instability on Sunday afternoon and evening which may allow for an isolated thunderstorm to develop. With some dry low levels and weak shear gusty winds would likely be the main threat if anything can develop. Confidence in this is low for now.

By Monday stronger southerly flow sets up an continues through the middle of the week. High temperatures in the 80s should be common. With upper level ridging in place Monday through Wednesday and very little upper level energy expected to move through the area mostly dry conditions are expected. Some hints of some support Wednesday into Thursday so will have to see if this comes to fruition.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1142 PM CDT Wed May 20 2026

VFR conditions will continue this TAF period. Besides a few lingering showers in a mid-level deck tonight, should see mostly quiet conditions persist through Friday afternoon. Otherwise, southeasterly winds will gradually increase with gusts between 20-30 mph expected through early evening. Lastly, scattered showers will return to the areas south of I-90 towards the end of the TAF period. As a result, added a PROB30 group into KSUX from 04z-06z.

FSD WATCHES/WARNINGS/ADVISORIES

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