textproduct: Sioux Falls

KEY MESSAGES

- Confidence remains high in an extended period of warmer weather through the holiday travel week. Temperatures may approach or surpass record values mid to late next week, including Christmas Day.

- Dry weather is expected for the vast majority of the upcoming week. One exception will be this evening with a low (15-25%) chance for a light wintry mix toward Highway 14 and into portions of southwest Minnesota.

- Breezier days will bring elevated fire danger to snow-free areas, mainly across south central South Dakota and through the Missouri River Valley.

DISCUSSION

Issued at 320 AM CST Sun Dec 21 2025

Main concern for today and through the week ahead will be temperatures, especially for our current snow-free areas and expanding with the expected additional loss of snow-pack as we continue to see daytime temperatures climb above freezing. NBM has been under-performing the past couple of days in areas with little to no remaining snow and as such, have adjusted today's forecast toward warmer/drier/breezier conditions, similar to early Spring/late Autumn when RAP/HRRR tend to perform a little better. This leads to minimum humidity this afternoon of 30-40% through the Missouri River Valley, with occasional wind gusts over 30 mph in northeast Nebraska supporting locally Very High grassland fire danger. Lighter winds toward south-central South Dakota will hold the fire danger in the High category.

The gusty winds today precede a subtle mid-level wave which will slide east across the Dakotas/Minnesota late this afternoon and tonight. After a mostly sunny morning, expect increasing high to mid level clouds with this feature, with continued uncertainty whether the combined forcing from the wave and associated strong warm advection will be able to overcome a very dry sub-cloud layer below 8-10kft AGL. High-res models indicate at least a low chance of very light precip (a hundredth or two at most) reaching the ground toward the Highway 14 corridor and perhaps as far south as I-90 in southwest Minnesota this evening to shortly after midnight. With low confidence, will keep precip chances below 25% for now. However, think it's worth mentioning over the NBM dry forecast as the wet bulb temperatures in area soundings would support a threat of very light freezing precip.

Weak warm advection continues through the day Monday, with a west-southwest low level flow supporting decent mixing of 925MB temperatures which climb into the double digits across south central South Dakota and down the Missouri River Valley. This should lead to highs in the mid 50s to lower 60s through this region, with readings tapering down to mid 40s along/northeast of a Huron-Sioux Falls-Storm Lake line. Wind speeds are not as strong as today, which should keep fire danger in check, mostly in the Moderate category with locally High conditions.

Temperatures continue to see some fluctuations through the week, slightly cooler Tuesday, then warming Wednesday/Thursday as an upper ridge builds over the region. NAEFS ensemble seems to be trending toward the ECMWF ensemble with the strength of the upper ridge and associated warming in the low-mid levels, though still some uncertainty regarding timing of an expected wave and cold front which could limit potential warming by Christmas Day in some locations. Both ensembles are showing a high (80-100%) probability of temperatures topping 50 degrees through the Missouri River Valley on Wednesday, with a very sharp gradient to low (<20%) probabilities near and northeast of a Huron-Sioux Falls-Storm Lake line. The gradient of this same probability broadens by Christmas Day, indicative of greater uncertainty, but also pointing to a slightly higher chance (20-40%) that 50 degree readings could expand into the I-90 corridor. Current forecast highs still flirt with records for some areas west of I-29 on Wednesday, and along/east of I-29 on Christmas Day.

While confidence is low due to diverging model solutions, the aforementioned late week wave could bring light precipitation to mainly portions of the forecast area by Christmas night or Friday. Those with post-holiday travel plans should monitor the forecast for updates throughout the week, as precipitation type could be light snow or even a wintry mix.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 1037 PM CST Sat Dec 20 2025

VFR conditions continue through the period. Light winds tonight continue to shift southerly, increasing Sunday morning. Gusts around 20 to 25 knots expected late Sunday morning through the evening hours. Periods of LLWS possible south of I-90 Sunday morning and again Sunday night, and have included mention at KSUX.

Can't entirely rule out some light mixed precipitation after 22.00z north of I-90; however, confidence and chances remain below 30% so will continue to omit mention at this time.

FSD WATCHES/WARNINGS/ADVISORIES

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