textproduct: Sioux Falls

KEY MESSAGES

- Temperatures this week are expected to be warm for this time of year, in the upper 60s and 70s. Average highs for this time of year are upper 50s to low 60s, with lows in the mid to upper 30s.

- Dry conditions are expected through Thursday evening of this week. Rain chances return Friday morning and continue through the weekend. (roughly 50%)

- Warm, dry, and periodically breezy conditions this week will lead to localized elevated fire danger.

DISCUSSION

Issued at 200 PM CDT Mon Oct 19 2026

A few high cirrus clouds and light southeast winds will result in a very pleasant fall evening. Weak WAA overnight will keep our lows warm for this time of year, in the low to mid 40s. (Average is mid 30s) Early Tuesday morning some patchy valley fog is possible, especially for areas along and west of the James River Valley. Here ensembles indicate a roughly 20-40% probability of visibility falling to 2 miles or less. Any fog that forms will be short lived and will mix out quickly as winds begin to increase after sunrise.

Tuesday an upper ridge broadens and shifts east over central and eastern CONUS. Surface high pressure settles over the Great Lakes region, and winds will become southerly. At the same time a mid- level wave along the western US/CAN border will push southeast. As it does so the SPG at the surface will tighten and winds will increase and become breezy. By mid-Tuesday afternoon gusts of 15-25 mph are expected with the highest winds along and west of the James River Valley. Occasional gusts up to 30 mph are possible in south central South Dakota. The NBM continues to have a low bias where high temperatures are concerned. After coordination with neighbors, boosted highs with a blend of NBM/NBM90. Highs for Tuesday are expected to climb into the upper 60s to low 70s, with averages for this time of year in the upper 50s to low 60s.

While minimum relative humidity values will remain well above critical (near 40% or greater) the warm and dry conditions will result in the Grassland Fire Danger Index elevating to the moderate category for areas along and west of I-29 Tuesday. The main concern for fire will be in the fields themselves as harvesting operations continue. Warm, dry, and periodically breezy conditions are expected to continue through the week, keeping Fire Danger slightly elevated. Please use caution and report any fires immediately.

Early Wednesday morning the previously mentioned wave will drag a weak cold front through the region. Guidance has continued to back off on rain chances with the front, keeping any rain that forms well south of our CWA. Winds will change from southerly to southeasterly as the front moves through in the afternoon. Highs for Wednesday will again be well above average in the low to mid 70s.

Through the overnight and continuing on into Friday strong WAA in the mid levels will work to sharply amplify the upper ridge. Heights aloft will rise to near the maximum of climatology. At the surface we can expect clear skies and warm highs in the mid to upper 70s both Thursday and Friday. Winds will also be increasing beginning Thursday afternoon as a deepening upper trough off the western coast moves inland. The tightening SPG will result in afternoon wind gusts out of the south-southeast at 15 to 25 mph. Strongest winds will be along and west of I-29, with occasional gusts to 30 mph possible over central South Dakota. Gusty winds move slowly east through the overnight and into Friday. By noon widespread gusts of 25 to 35 mph are possible. Once again the strongest winds will be located over central South Dakota where gusts in excess of 45 mph are possible. Winds decrease gradually through the overnight, but continue gusting 20-30 mph through early Saturday afternoon.

By early Friday morning the first wave of vorticity moves into the region bringing chances for showers and possibly a few strikes of lightning. By Friday evening the main surface cold front will be located over central South Dakota, and rain chances increase and move east with the it. At this point model divergence is large, and too uncertain to try to describe track and timing. Rain totals are also very uncertain with ensembles currently showing a 50% probability or less of 0.25 inches. Severe weather during this time is not anticipated.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1219 PM CDT Mon Oct 19 2026

VFR and mostly clear skies will prevail this period. The remaining cirrus east of I-29 will gradually clear off through the afternoon.

Winds will be out of the south to southeast and light for the majority of the period. Shortly after 20.12Z Tuesday winds will become southerly and start to increase. By the end of the period gusts of 15-23 kts are expected across most of the CWA.

FSD WATCHES/WARNINGS/ADVISORIES

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