textproduct: Sioux Falls

KEY MESSAGES

- Scattered showers possible this afternoon mainly west of the James River Valley with light accumulations expected.

- Cooler conditions continue this week. Above normal temperatures are expected Sunday through Wednesday.

- Showers and isolated thunderstorms are expected from Thursday evening through Friday night. Severe weather not expected. However, some ensemble guidance suggests about a 40 percent chance for a half an inch or more of rain during this time.

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 /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 610 PM CDT Wed May 20 2026

VFR conditions are expected this TAF period. Taking a look at satellite imagery, mid to high level clouds continue to stream into the area from the south with our next short wave. While this could lead to a few hours of -SHRA across areas south of I-90 and west of the James River Valley, should see most of this activity taper down overnight. Lastly, southeasterly winds will gradually decrease into the overnight hours to end the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES

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