Sioux Falls, SD 57101 Weather

Key Messages

- HIGH FIRE DANGER TODAY: Strong wind gusts of 30 to 45 mph combined with warm temperatures will create high fire danger. Agricultural harvest activities will have the greatest risks into the evening.

- COOLER WITH SCATTERED WEEKEND RAIN: A slow-moving front will bring increased clouds and occasional rain this weekend. Temperatures will be notably cooler (40s/50s) by Sunday.

- SIGNIFICANT RAINFALL LIKELY MONDAY-TUESDAY: A large multi-day system will bring widespread rain to start the new work week. Confidence in amounts over 1" through Tuesday morning remain high.

- ACTIVE WEATHER CONTINUES: A second fast moving system may bring rain chances back by Tuesday Night and Wednesday, with temperatures near seasonal normals.

Discussion

Issued at 1218 PM CDT Fri Oct 23 2026

THIS AFTERNOON: Winds continue to increase early this afternoon with observed gusts between 30 and 45 mph. Temperatures continue to warm into the 70s, and potential for some highs in the 80s remain possible along and west of the James River valley. However, a persistent mid-upr cloud deck may limit the climb this afternoon. Out in western South Dakota, we're beginning to see the first signs of a frontal boundary forming that will gradually move eastward overnight. The fire danger remains very high this afternoon, especially for agricultural areas, please see separate discussion.

TONIGHT: An elongated upper trough stretching across the Rockies and into southern California will begin to stretch and split in two overnight. Northern energy tracking eastward across southern Canada will be strong enough to nudge the aforementioned surface boundary into the I-29 corridor by mid-mornign Saturday. Ahead of this boundary, convergence on a 40 knot LLJ and the arrival of a mid-lvl vorticity maxima should be enough to allow isolated to scattered showers to develop and and ahead of this boundary. MUCAPE may be as high as 300 J/KG after 3am, so have increased PotThunder to at least suggest isolated lightning strikes into mid-morning.

SATURDAY-SUNDAY: While northern stream energy moves eastward across Canada, a large upper trough will remain over the Four Corners region through the weekend. Overhead and closer to home, the aforementioned surface boundary will linger across the Tri-State area this weekend. This front, stacked on top by a low-lvl frontal zone, as well as somewhat persistent divergence from the right entrance region of an upper jet, will keep scattered rain chances and quite a bit of cloud cover through the area during the weekend. Now the degree of rain coverage is still up in the air, given somewhat diffuse and transient lift at times, but also some sub cloud dry air that could linger. So will continue to advertise a narrow stripe of low to mid-range PoPs that will fluctuate north and south with the movement of the low-lvl baroclinic zone.

Temperatures will be quite tricky on Saturday as the front bisecting the CWA could lead to a large temperature discrepancy from Huron to Storm Lake. 12Z guidance has trended downwards with highs slightly, so blended in short term guidance to account for trends the NBM may not have caught onto yet. There seems to be much more consistency in guidance that cooler air may sink further south behind the front for Sunday. With a persistent and cool northeast surface flow in the CWA, highs may struggle to break the 50s in portions of the CWA with the warmest highs near Highway 20.

MONDAY-TUESDAY: Slight discrepancies in medium range guidance on Thursday have resolved somewhat this morning. The large upper trough in the Four Corner begins to eject northeast late Sunday into Monday, and will begin to enhanced warm advection northward and increase the intensity of the low-lvl frontal zone through the CWA by Monday morning. We'll have to watch for any potential instability arrival, but fairly widespread moderate rain may begin to form Monday morning and gradually retreat northward as the upper trough enters the Plains.

Aviation

Issued at 637 PM CDT Fri Oct 23 2026

Breezy conditions with southerly gusts of 20-30 kts will continue through most of the period, though we will gradually see a downtrend in winds as the night and daytime on Saturday progresses. The exception will be near and west of the James River where a secondary push of stronger gusts towards 35-40 kts will follow a cold frontal passage around and just after sunrise Saturday.

Also tonight, some mainly directional low level wind shear will be present given the southwesterly low level jet. An eastward moving cold front will enter central South Dakota by daybreak, turning surface winds to the northwest area-wide as it moves through during the daytime hours on Saturday. Lastly regarding winds, gusts will diminish below 20 kts for everyone by the last few hours of the period.

Rain chances will increase late tonight into tomorrow morning for areas mainly between I-29 and the James River, though exact placement of where this activity develops remains a bit uncertain. Thus, PROB30 groups for showers at KFSD and KHON make the most sense at this time. Thunder chances are low with this activity (less than 20%), but can't entirely be ruled out. As we head throughout the day on Saturday, additional showers look to develop, though thunder chances will diminish below 15% as we head throughout the day.

Fire Weather

Issued at 1220 PM CDT FRI Oct 23 2026

Strong southeast wind gusts between 30 and 45 mph will continue this afternoon. Temperatures are a bit slower to rise today in response to cloud cover overhead. However highs still well into the 70s will be likely, with RH values dropping between 35 and 45% by peak heating this afternoon. Very high GFDI conditions will continue into early evening. While grassland moisture levels and RH remain high enough to prevent widespread red flag warnings this afternoon, AG related fire danger will be near critical into early evening. Harvest activities may want to postpone until winds subside and local partners need to remain vigilant into the evening.

A front moves from west to east early Saturday turning winds west northwesterly and bringing increased rain chances through the weekend. A widespread wetting rain is likely early in the work week.