textproduct: Sioux Falls

KEY MESSAGES

- Very isolated valley fog may develop through the Monday morning commute, with a low (30% or less) chance of visibility falling below 6 miles.

- Above to well above normal temperatures expected into the weekend. Temperatures from 10 to 20 degrees above normal Wednesday through Saturday morning. Normal highs are upper 50s with normal lows in the mid/upper 30s.

- 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 252 AM CDT Mon Oct 19 2026

Guidance remains quite split on fog development this morning, but majority of guidance including short term ensembles limits coverage to river valleys. Both the REFS and HREF probability of visibility at any one location around or below 30%, with generally lower probability of visibility below 2 miles. Confidence is low a bit lower as we have an increase in high clouds, which thus far has been keeping temperatures a few degrees warmer. We'll cool into the upper 30s to mid 40s with light winds.

Raised high temperatures closer to the NBM 90th for the next three days, which results in highs anywhere from 2-6 degrees warmer each day than the blend. Warmer temperatures and periodically breezy conditions will help fuels cure, which may lead to additional fire concerns this week. Highs today in the 60s, and light winds limit fire concerns today. Temperatures continue to warm into mid week.

Dry conditions prevail into late week, with continued downward trend and southern shift in ensemble probability of measurable precipitation Wednesday into Wednesday night - less than 10% outside of the GEFS which is around 20%.

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 /12Z TAFS THROUGH 12Z TUESDAY/

Issued at 542 AM CDT Mon Oct 19 2026

VFR conditions prevail through the period. May see some very localized fog in the river valleys this morning, but confidence is low (less than 30%). However, fog could briefly reduce visibility to MVFR conditions. Light winds generally vary through the period from easterly to southeasterly. Occasional gusts around 15 knots west of I-29.

FSD WATCHES/WARNINGS/ADVISORIES

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