textproduct: Sioux Falls

KEY MESSAGES

- Cool and Damp Conditions Continue Today: Lingering clouds and morning light drizzle will keep high temperatures 10 to 15 degrees below normal (near 60 degrees).

- Mid-Week Rain: Widespread soaking rain (0.50 to 1.0+) and isolated, non-severe thunderstorms return late Wednesday into Thursday morning.

- More Rain By the Weekend: An active weather pattern continues bringing a high chance (>60%) of additional rain Friday night into Saturday.

- Gradual Warming Trend: Temperatures will rebound to near- normal highs in the upper 60s to lower 70s starting Thursday and lasting through the weekend.

UPDATE

Issued at 325 AM CDT Tue Sep 22 2026

No significant changes to the forecast early this morning. While drizzle is not as widespread or heavy as the past couple of days, we are still seeing occasional -RA/-DZ reported by various ASOS and AWOS stations, with indications of light precip on some area web cams as well. Think potential for measurable precip is lower given shallower cloud depth than yesterday, thus will continue to carry lower-end drizzle chances into the morning hours. By midday, forecast soundings show the stratus layer becoming sufficiently thin to end the drizzle threat, though sunshine may still be hard to come by outside of southwest Minnesota and perhaps part of the I-29 corridor in response to a drier east-northeast flow out of Minnesota.

DISCUSSION

Issued at 121 PM CDT Mon Sep 21 2026

THIS AFTERNOON: Widespread stratus, drizzle, and showers persist, with new development over NW Iowa expected to continue into the evening hours. Temperatures with the clouds are quite cool today, only reaching the mid-50s, some 10-15 degrees below normal.

TONIGHT: The large upper low will slowly wobble southeast tonight, most likely bringing an end to the widespread shower activity through the night. HOWEVER, soundings show an extensive low stratus layer persisting, with the depth of this low-lvl airmass combined with weak forcing allowing drizzle and areas of lower visibility to continue into daybreak Tuesday.

TUESDAY: The upper low moves away from the area with a very slow arrival of shortwave ridging by mid-day. Drizzle may linger into mid-late morning in a few areas as another weak 700mb vorticity area slides towards the Tri-State area mid-morning. Widespread cloud cover is now anticipated into early/mid afternoon. Eventually we may see stratus thin and some breaks appear by the late afternoon, but temperatures will again remain nearly 10 degrees below normal either side of 60 degrees.

WEDNESDAY-THURSDAY: Mid-lvl heights rise as we head into Wednesday, partially in response to a deeper trough lifting towards the Central and Northern Rockies. The arrival of this trough will accomplish a few things. Firstly, inducing lee side troughing in the western High Plains and turning surface winds nearby towards the south. Secondly, inducing a 40 knot southerly low level jet by Wednesday afternoon allowing low-lvl moisture to stream back northward into the central Dakotas. Finally, bringing a bit more warm air northward which should allow us to warm into the 60s in most areas with the lower 70s in south central South Dakota.

Shower and isolated thunderstorm development may develop by late Wednesday afternoon and slide east in the evening and overnight hours, driven by broad warm advection, weak dPVA from the wave to our northwest, but also the arrival of a secondary area of vorticity lifting out of the Southwest US. Rainfall amounts are not expected to be excessive, but the 25/75th 24hr QPF from the NBM would suggest amounts between 0.25 and 1.5 inches. The GEFS/EC/GEPS mean QPF sits around 1.1 in most locations. At this junction I'm not anticipating any severe weather risks, with MUCAPE around 500 J/KG on average with the passage of this precipitation.

We'll gradually clear out during the second half of Thursday, but there will be some potential for additional clouds to move in by Friday morning. Temperatures behind the precipitation Thursday will rebound back to the upper 60s to lower 70s depending on clearing.

FRIDAY-SUNDAY: A wet September will continue as we approach next weekend with yet another progressive upper trough lifting through the Rockies and into the Plains by late Friday into Saturday. This wave will bring high rain chances (>60% as of this product) Friday night into Saturday morning. Temperatures will trend slightly warmer for the upcoming weekend with most guidance settling on highs near normal (upper 60s to lower 70s).

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1220 AM CDT Tue Sep 22 2026

Widespread low level stratus continues to blanket the vast majority of the area. The stratus is sitting mainly at MVFR/IFR levels with visibilities mostly at VFR levels. Some locations, mainly across northwest Iowa are reporting visibilities down to MVFR/IFR levels. Some drizzle remains possible beneath the stratus for the rest of the night. Some models suggest ceilings could briefly bounce between categories at any individual location. For now, have kept ceilings consistent but trends will be monitored. The stratus will begin to lift through the morning hours tomorrow to VFR/MVFR levels though remain draped across most of the area. The mix of VFR/MVFR stratus looks to persist for the rest of the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES

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