textproduct: Sioux Falls

KEY MESSAGES

- Near to record high temperatures continue Saturday afternoon.

- Fire danger will become elevated Saturday afternoon in most of the area, and may turn critical along the Missouri River into NW Iowa. Any burning activities should be postponed.

- The passage of a front Saturday night will bring potential for 40+ mph wind gusts initially, and then wind chills below freezing by daybreak Sunday.

- A roller coaster ride of temperatures and wind can be expected next week, increasing fire danger, but with little to no rain anticipated.

DISCUSSION

Issued at 1214 PM CDT Sat Mar 21 2026

THIS Afternoon: Near to record temperatures continue to remain possible Saturday afternoon as temperatures surge into the 80s. Quite a few locations already saw their first 80 degree temperature of the year on Friday, but others will see these temperatures today. This will mark some of the earliest 80 and 90 degree highs on record. A weak surface front remains stalled through the heart of the CWA early this afternoon, leading to a bit of a lull or drop in wind speeds along and south of I-90. However, we are seeing some modest increase in southwesterly flow through eastern Nebraska, pushing into the Missouri River valley region by mid- afternoon and then NW Iowa by late afternoon and early evening. Winds may be a tad lighter than previously expected, but dangerously low RH continue the fire danger risks with rapid spread increased.

TONIGHT: 12Z high resolution CAMs all show the cold front, steadily dropping southward this evening, but the true surge of 925:850 CAA not arriving until late evening. The arrival of this cold air, inducing steep surface to 900mb lapse rates, will allow the development of strong gusts upwards of 40 to 45 mph into the overnight hours. These winds arrive near Highway 14 by 9-10pm, I-90 by 11pm, and Highway 20 after midnight. Have manually increased gusts through the overnight to account for the wind potential. At this point, the brevity of the higher gusts does not require a wind advisory. After a beautiful day/evening, anyone that builds a backyard fire should make sure these are extinguished as they could provide easy sparks for fire starts. Further behind the front, weak 700:500 vorticity traveling through the westerly mid-lvl flow could lead to sprinkles to very light showers tracking as far south as I- 90 by sunrise.

SUNDAY: Sunday morning we complete the circle of seasons back to Winter as wind chills fall below freezing through late morning. The good news is that it's now late March and as winds turn light through the afternoon, we should again see temperatures back to normal in the lower 50s.

MONDAY: As we've been discussing the past week, much of the upcoming work week will remain quiet as the mid-lvl pattern continues to be dominated by an anomalously strong upper ridge over the southwestern US. While this ridge will be weakening slightly early in the week, it is expected to rebuild as the week moves forward. By Monday, we'll again see the return of low-lvl warm advection which will allow a tongue of moisture to drift through the Dakotas. This meager moisture layer combined with weak to modest lift could result in a few scattered high based showers moving SW to NE Monday afternoon. There is only around 50 J/KG MUCAPE moving through, so not anticipating much in the way of lightning development. Wind will also increase in the afternoon, gusting over 25-30 mph at times west of I-90. RH values however will remain in the mid-30 percent range which will lower fire danger slightly.

TUESDAY-WEDNESDAY: That southwestern ridge really begins to increase on Tuesday, pushing warmer low-lvl temperatures further east through the Plains and towards the Great Lakes. A surface warm front is expected to develop through the Dakotas and Minnesota by Tuesday, allowing warmer air to surge northward and keeping winds southerly both days. Tuesday will again feature increased fire danger, as increasing low-lvl flow off the Western Plains increases to 40 knots. Afternoon soundings show potential for deeper mixing and potential for further dew point/RH drops than the deterministic NBM would suggest. If wind gusts continue to increase, then elevated fire danger may develop through the afternoon. That aforementioned weak front will settle southward on Wednesday, through temperatures may actually rise even further as the feedback from dry Spring ground and increasing March sun angle increases. Current projections place high temperatures in the 60s and 70s in most locations, with weaker low-lvl flow reducing general fire danger risks.

THURSDAY-FRIDAY: Mid-lvl flow flattens for the second half of the week allowing a very progressive shortwave to track along the US/Canada border on Thursday. This system is expected to push a stronger cold front southward through the Plains, bringing both near to slightly below normal temperatures to end the week but also strong wind gusts. While quite a bit of averaging is taking place, LREF guidance indicates a 50% probability of 30+ mph wind gusts with a 5% probability of near advisory level gusts Thursday. With lowering afternoon RH and continuation of gusts, this raises the potential for fire weather concerns already showing up in very high GFDI forecasts. Winds are expected to decrease Friday and continue to remain low into the weekend. Precipitation chances with this system and front remain low partially due to the lack of low-lvl moisture, but mostly the track of the upper wave to the northeast. At this time, ensembles only point to a 20% probability of measurable rain.

AVIATION /00Z TAFS THROUGH 00Z MONDAY/

Issued at 655 PM CDT Sat Mar 21 2026

Winds will become northerly and begin to increase behind a cold front this evening as much colder air flows into the region. Strong, gusty winds are expected to begin to impact the area along Highway 14 around 22.02Z, expanding south into the I-90 corridor around 22.04Z, Highway 20 corridor around 22.06Z. Sustained winds of 20-25 kts with gusts 30-40 kts are expected, with isolated gusts to 45 kts possible. The strongest winds should be south of the region around sunrise, gradually decreasing through the day. By the end of the period winds will become light and variable.

Clouds begin to push in from the north and light sprinkles become possible after 22.00Z. Sprinkles are most likely to remain along and north of I-90. Ceilings will degrade to MVFR with patchy IFR possible. Lower ceilings look to remain along and north of Highway 18. Ceilings begin to improve in the morning and should be back to VFR around 22.11Z and for the rest of the period.

FIRE WEATHER

Issued at 1214 PM CDT Sat Mar 21 2026

Frontal boundary arriving a bit faster than previously expected, bringing lighter winds to areas south of I-90 late this morning. At this point, the strongest southerly winds may end up just south of the Missouri River and then extend northeast into several northwest Iowa counties. With that said, while RH values are going to fall near 10-15%, gusts are likely going to fall short of RFW criteria. With extremely low RH, ANY fire start will spread very quickly due to dry fine fuels. Will continue to monitor conditions over the RFW, but at this time no changes are anticipated.

Perhaps bigger concerns arrive after sunset as a strong cold front will push winds towards the 30 to 45 mph mark for a period of time overnight. While RH values will be rising very quickly with the cooler air, any fire that was started earlier in the day could pose a risk for reigniting. Similarly, for those enjoying a backyard fire this evening given the nice weather, ensure those fires are fully extinguished.

Looking to Sunday...dry and breezy conditions are again expected, with GFDI values rising towards the high category.

CLIMATE

Issued at 1214 PM CDT Sat Mar 21 2026

Record High Temperatures:

March 21: KFSD: 83/1910, KSUX: 85/1910, KHON: 84/1907, KMHE: 88/1907

Record High Minimum Temperatures:

March 21: KFSD: 49/1938, KSUX: 48/2012, KHON: 45/1938

FSD WATCHES/WARNINGS/ADVISORIES

SD...Red Flag Warning until 10 PM CDT this evening for SDZ050-063- 068>071. MN...None. IA...Red Flag Warning until 10 PM CDT this evening for IAZ020-031- 032. NE...Red Flag Warning until 10 PM CDT this evening for NEZ013-014.