textproduct: Sioux Falls

KEY MESSAGES

- Scattered showers likely south of I-90 with areas of drizzle near and north today. Rain won't be as widespread today as what we saw Thursday, but be prepared for occasional pockets of light rain.

- The active weather pattern continues bringing a high chance (>90%+) of additional rain later tonight into Saturday and again later Monday into Tuesday (>50%).

- Daytime temperatures remain below normal, but should climb closer to normal Sunday and Monday.

UPDATE

Issued at 314 AM CDT Fri Sep 25 2026

Another dreary day on tap with abundant low level moisture across the area. The difference will mainly come down to mid and upper level moisture and whether or not a little rain can develop or if we end up with mostly drizzle. The latest model soundings strongly hint at a deep dry layer from about 400mb to 700mb this morning, basically cutting off the dgz. The exception may be closer to the Sioux City area where a wave in NE drifts north and introduces some mid level moisture. Long story short, mostly drizzle potential this morning except around the Sioux City area.

By this afternoon this weak piece of energy drifts farther north and tries to bring some of this mid level moisture towards I-90. This should bring some scattered showers/patchy light rain into the James River Valley and to near and just north of I-90. Rainfall amounts through sunset should generally be less than a tenth of an inch, maybe closer to a quarter inch near Sioux City.

A stronger wave shifts north later tonight through Saturday morning. This deepens the warm air advection and brings just a touch of weak instability, with soundings looking fairly moist neutral suggesting a fairly efficient rain environment. Right now looks like just enough instability to produce a few rumbles of thunder late tonight into Saturday morning. The latest high res models and ensemble output all fairly consistent on bringing the higher rainfall totals during this time to areas near and east of highway 81, and particularly in parts of northwest IA. Near and east of highway 81 amounts will likely be half an inch to an inch with isolated pockets of 2 inches. While flash flooding and river flooding remain unlikely, ponding of water on roads with the heavier downpours will be possible.

By Saturday night the wave is mostly east of the area with weak upper level troughing remaining in place. Model soundings linger the low level moisture, but does suggest it will become more shallow. There is also a little weak elevated instability that appears to be weakly capped, but might allow for scattered showers Saturday night, on top of patchy drizzle. Farther west, if enough clearing occurs, fog will be possible for areas near and west of the James Valley.

DISCUSSION

Issued at 242 PM CDT Thu Sep 24 2026

An area of steady light to locally moderate rainfall extends from around a Slayton to Yankton line and points east. This area of rain will gradually push east through the remainder of the afternoon and start to fall apart this evening over northwest Iowa. However, patchy drizzle will be possible after this rain departs especially along and east of I-29. A bit drier in the low-levels over parts of northwest Iowa tonight, so it may take a bit longer for drizzle to develop there. Farther west, especially into south-central South Dakota, we will see some breaks in the clouds which will allow temperatures to warm into the middle 70s. Some instability (around 500-750 J/kg) will be present along and ahead of a weak front over south-central South Dakota where this heating is occurring, but plenty of dry mid-level air should prevent scattered showers and storms from developing in these locations. In the off chance (<10%) we get a storm, severe weather is not expected as weak effective shear looks to be place.

Heading into tonight, a few showers will continue to be possible mainly along the Highway 20 corridor. Low stratus looks to spread back west through the night, but before it spreads back into south- central South Dakota, patchy fog can't be ruled out there. Drizzle will begin to become more likely heading into early tomorrow morning as cloud ceilings continue to fall, so keep the rain gear handy for your Friday morning commute. Scattered light showers will develop throughout the day, with chances gradually lifting northward through the afternoon due to strengthening warm air advection at 850 mb. These will be more of the hit or miss variety unlike what we saw today, so keep that umbrella nearby but rain totals will only be a few hundredths to a tenth of an inch during the day on Friday, except for locally higher amounts along the Highway 20 corridor Friday morning. Lowered the high temperatures a bit from the NBM for Friday given the cloud cover and drizzle, with highs mostly in the lower 60s. If some peaks of sun can be realized, a few middle to upper 60s for highs will be possible.

Rain chances will increase Friday night into Saturday morning as the main upper wave pivots through the area. The highest rainfall totals during this time frame will generally be over northwest Iowa and adjacent areas of southeast South Dakota and far northeast Nebraska, where around a half an inch to an inch of rain can be expected. A few pockets of 1-1.5" of rain (15-25% chance) can't be ruled out mainly along and southeast of a Spencer to Sioux City line. This rain should be spread out long enough where flash flooding concerns will be low where these highest amounts occur, but still be prepared for wet roads if traveling especially early Saturday morning.

Showers and very isolated storms will gradually push east through the afternoon, though once again some patchy drizzle will remain possible after any of the rain showers end at least through the early evening Saturday. Drizzle details will be refined as we get closer to the Saturday afternoon. Though some very patchy drizzle will be possible into Sunday morning, should mostly see dry weather for the day. This should allow for some of the warmest temperatures that we've see over the past few days, with highs in the upper 60s to middle 70s. Ultimately, these temperatures will be dependent on how quickly we can scatter out any morning clouds, so expect changes to the forecasted temperatures as we approach Sunday.

Rain chances do look to return once again on Monday, but especially Monday night into Tuesday. This will be as the West Coast longwave trough finally swings into the area. Will have to watch for any heavy rain once again with this activity, especially on top of the rainfall we've seen the past week. LREF probabilities show around a 30-40% chance of at least an inch of rainfall Monday night through Tuesday night, focused over northwestern Iowa. Trends will continue to be monitored as we get closer to next week.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 628 AM CDT Fri Sep 25 2026

Widespread IFR conditions through the period. Drizzle will be fairly widespread through the morning, with showers developing through the day, moving from south to north. Rain will overspread the area tonight through Saturday morning with the most persistent rainfall near and east of highway 81 overnight.

FSD WATCHES/WARNINGS/ADVISORIES

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