textproduct: Sioux Falls

KEY MESSAGES

- Patchy fog is possible tonight, though the potential for fog is low (<=20%).

- Above normal temperatures expected through next weekend, from 10 to 20 degrees above normal Wednesday through Saturday morning.

- Precipitation chances remain very low (less than 10%) until late week.

- Continued dry, warm, and periodically breezy conditions could lead to elevated fire concerns through the week.

UPDATE

Issued at 847 PM CDT Sun Oct 18 2026

A weak front continues to sit across the area this evening. Currently it is sitting along an approximate line from Marshall, Minnesota to Dell Rapids, South Dakota to Tripp, South Dakota. The surface trough that this boundary resides in will keep winds a little bit more on the light and variable side relative to locations outside of the trough. These light and variable winds will create the potential for patchy fog tonight. That said, this potential is low (<=20%) and located along and southeast of the boundary. The other factor keeping the lower risk for fog is incoming high level cirrus from a weak shortwave trough beginning to drift into the Plains. The cirrus will keep low temperatures down to the the low 40s across the area, with a few locations falling into the upper 30s.

Monday will see a continuation of above normal temperatures, though a bit cooler from today as the thermal ridge pushes off to the southeast. This will leave 850 mb temperatures around +6 to +9C across the area. Mixing these temperatures to the surface will result in high temperatures in the mid 60s across the area. Skies will clear out as the cirrus pushes east of the area. The clear skies, above normal temperatures, and light southeasterly winds will make for a pleasant Fall day. Low temperatures Monday night will remain mild, only falling to the low to mid 40s.

DISCUSSION

Issued at 120 PM CDT Sun Oct 18 2026

Quiet weather ahead for the next several days. A weak front settles into the area tonight into Monday morning. This should bring lighter winds and a bit cooler low temperatures, mainly from the upper 30s to lower 40s. With the light winds and some weak surface convergence along the boundary, some patchy fog will be possible. For now the fog appears as though it will mainly be in low lying locations.

Monday should prove the be a fairly mild day with winds generally below 15 mph. Highs mostly mid 60s.

Stronger southerly flow will be in place on Tuesday which could bring some elevated fire weather concerns as temperatures climb into the 70s. A weak boundary settle south on Wednesday, with winds expected to be much weaker than Tuesday. With some heating ahead of the incoming front, highs should climb into the mid 70s in most locations with an 80 degree reading not out of the question.

Stronger troughing develops to the west Thursday into Friday which will bring an increase in southerly flow to the area, with some elevated fire weather concerns once again. Highs both days will be in the 70s.

Rain chances increase Friday into Saturday morning as this trough spreads on the Northern Plains. For now rainfall amounts look fairly light with the 50th percentile from the EC/Canadian and GFS ensemble output all less than a quarter of an inch, with the Canadian and EC Ensemble generally less than a tenth of an inch. Low temperatures on Friday and Saturday mornings will be very mild with stronger southerly flow in place. Lows both mornings will be just a touch below the seasonal normals for high temperatures.

Saturday and Sunday will see cooler temperatures but for now the air mass behind this system is not looking too cold, so anticipating highs in the 60s both days.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1044 PM CDT Sun Oct 18 2026

VFR conditions are expected for the TAF period. Light and variable winds are expected tonight. This could lead to the development of patchy fog across the area. However, this potential remains low (<= 20%) because of high level cirrus beginning to overspread the area now. The cirrus is expected to persist through the night. Will monitor trends through the night. Winds will pick up out of the southeast tomorrow with speeds up to 5 to 10 knots. These southeast winds will finish out the TAF period.

FSD WATCHES/WARNINGS/ADVISORIES

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