textproduct: Sioux Falls

KEY MESSAGES

- Northwest winds gusting 30-50 mph early this morning will gradually decrease through the day.

- Light snow returns late tonight into Saturday, mainly focused near to north of I-90. Amounts will be light, perhaps an inch or two.

- A major winter storm system moves into the area Saturday evening through early Monday. Moderate to heavy snow and strong winds are expected. A Winter Storm Watch for Blizzard conditions has been issued for locations along and northeast of a line from Chamberlain, South Dakota to Beresford, South Dakota to Ida Grove, Iowa line. Winter Storm Watch is in effect beginning Saturday evening into Monday morning.

UPDATE

Issued at 405 AM CDT Fri Mar 13 2026

With the strongest push of cold advection now south/east of the forecast area, wind speeds have fallen off across western portions of our CWA. Thus have canceled the High Wind Warning along and west of the James River. While locations farther east have begun to ease, still seeing gusts solidly in the strong Advisory to borderline warning level, so will let that area ride for now.

Looking ahead, made a minor change to the Winter Storm Watch for Saturday night through Sunday night, expanding southward into a few more counties to account for blizzard potential at snowfall totals less than 6 inches. While we could very well see blizzard conditions with totals as low as 2 or 3 inches, only expanded into areas where confidence in 4+ is higher for now given uncertainty in how tight the southern gradient of the snow band may be.

Issued at 940 PM CDT Thu Mar 12 2026

Winds are beginning to increase, a hour or two later than previously expected. Huron Airport has seen a peak gust through the time of this discussion of 70 mph, with a few other sites close to or above that over the last hour or so. Expect winds and gusts to continue to increase from west to east over the next few hours. Gusts to 55-65 mph with sporadic gusts to 75 mph are expected, so no planned changes to the on-going High Wind Warnings.

Noticing a couple of trends this evening as the 13.00z data as it begins to come in. With regards to snow chances Friday night into early Saturday, latest guidance is showing a bit more tightening in the snow band as the wave lifts north as well as the 850mb and 700mb fronts. This tightening also seems to be tied to strengthening frontogenesis (f-gen), likely around 700mb. Most of the area should see less than 2 inches of new snow, but would not be surprised to see areas with locally higher amounts. Depending on where exactly this falls, expect to see some melting before the main show.

As for the Saturday evening to early Monday system, both 12.18z and 13.00z guidance is showing a shift to the north, with some NAM guidance shifting the heavier snow through the evening hours north of US Hwy 14 (vs a bit further south toward I-90) and not bringing snow to the Sioux Falls area until after midnight Sunday. Now, we need to take this with a bucket of salt. Over the last couple of years, models have shown this northern shift in the track of a significant winter system roughly 48 hours before onset just for the models to shift back to the south within 24-36 hours of onset. We'll be closely monitoring trends, and folks with local and regional travel plans from Saturday into early next week should continue to keep a close eye on the forecast over the next 24 hours - be prepared to alter or cancel travel plans.

DISCUSSION

Issued at 250 PM CDT Thu Mar 12 2026

An active pattern is ahead with confidence for significantly impactful weather increasing. Looking aloft at GOES water vapor we can see the flow aloft is northwesterly with a 140-150 kt jet streak. The exit region of which is located over the Tri-State area through this afternoon and overnight. The resulting wind divergence aloft will further enhance winds in the LLJ as surface convergence increases and pressure falls ahead of an incoming Clipper system. As we begin to mix higher into the boundary layer today we will tap into that 30-40 kt LLJ. Gusts at the surface will increase through the afternoon as a result, reaching 30-45 mph.

The clipper system places us in a strong WAA regime this afternoon. However, there are a few details that may work to limit afternoon highs. Clouds continue to flow in from the northwest, and have advanced further south faster than previously anticipated. There is also a chance for isolated to scattered rain showers and thunderstorms this afternoon and evening, roughly between 3pm to 9pm. Soundings indicate a very dry subcloud layer, which will limit how much actually reaches the ground. However, due to a 10 degree C dewpoint temperature depression, evaporative cooling as rain falls through the dry layer may produced severe wind gusts of 60+ mph. This is outlined in the SPC Day 1 Marginal (level 1 of 5) outlook. Considering this have decided to go with the slightly cooler NBM highs for this afternoon. Along and south of a rough line from Huron to Storm Lake highs will range from the low to upper 60s, warmest along the southern Missouri River Counties. This area is also expected to see the lowest relative humidity values, less than 30%. To the north of that line highs will be in the 50s with higher relative humidity values. Though we have some lingering snow/snowmelt on the ground from yesterday, and the cooler highs today, the low humidity and very strong winds keep Grassland Fire Danger in the Very High to Extreme categories for this afternoon. See the Fire Weather Discussion below for more details.

Our next period of concern comes this evening and overnight as the Clipper system drops southeast into Minnesota. The SPG continues to tighten as pressure falls ahead of the cold front. The LLJ enhances as divergence aloft increases. Temperatures in the mid-levels drop rapidly 6-10 degrees C behind the front. All these factors will work together to produce very strong winds beginning later this afternoon and continuing through Friday morning. By 6pm CDT tonight gusts east of I-29 will be between 25-35 mph. Areas to the west will be seeing gusts 35-45 mph. As we continue into the evening gusts continue to increase and spread southeastward. Widespread gusts of 55-65 mph are expected with isolated gusts up to 75 mph possible. Winds remain strong through 4-6 am CDT when they will begin to gradually taper off through Friday morning, becoming light in the afternoon. Afternoon highs will be cooler thanks to the northwesterly winds brining in cold air, reaching only the mid 30s to 40s.

Saturday will begin with light snow beginning to fall during the early morning hours as warm air advection (WAA) strengthens aloft, tightening the elevated frontal temperature gradient and also strengthen the frontogenesis (FGEN) along it. The dendritic growth zone (DGZ) will also be saturated with sufficient omega (upward motion) in it to support a band of snow. The good news about this band is that not expected to last long as the FGEN will be weakening during the morning hours. Light snowfall is expected with this band which looks to fall across near and north of I-90. Saturday afternoon will be more on the dry side as the upper level wave responsible for additional impacts will be pushing in from the Northern Rockies. High temperatures look to warm to the 30s to up to around 50F during the afternoon timeframe though depending on how much snow falls during the morning hours, highs temperatures could come down a bit.

Chances for snow will be increasing Saturday evening as WAA restrengthens aloft. This in turn will re-tighten the temperatures gradient and thus restrengthen the FGEN along the elevated front. This will be the main show as strong QG ascent resides in the right entrance region of an upper level jet. Snow will expand in coverage through the rest of the evening and entire overnight hours. There could be a small area of mixed precipitation on the leading edge of the band of snow as the WAA just barely pushes temperatures above freezing aloft. The strong front will translate southwards after beginning around the highway-14 corridor. This will quickly cool the warmed temperatures, turning any mixed precipitation back over to snow. The strongest ascent will come during the overnight hours and into early Sunday morning where the latest deterministic guidance shows strong FGEN around 700 mb along with low stability and negative equivalent potential vorticity (EPV) values above the front. Thus, the bulk of the snow looks to fall during this period of time. At the same time, winds will be strengthening as snow fall rates increase. Gusts will be out of the east/northeast with gusts strengthening up to 30-40 mph throughout the night. With such strong winds in place as snow is falling, blowing snow is expected with the falling snow. The best forcing for ascent will be sliding eastwards throughout the morning hours on Saturday. This will gradually end snowfall across the area from northwest to southeast. Though latest trends keep snow chances going through the afternoon timeframe. Winds will turn to out of the north during this period of time with gusts further increasing up to about 50 mph. Snow will have the potential to blow around after snow is done falling. Thus, blowing snow looks to persist for the rest of Saturday even after the snow finishes falling. Thus, have decided to issue a Winter Storm Watch for Blizzard conditions. The Watch is in effect from Saturday evening through Monday morning as the weakening winds will still result in some blowing snow through Sunday night. Snowfall amounts at this time look to be impactful with the ensembles showing a 40- 90% chance for snowfall totals to exceed 6 inches mainly along and northeast of a Chamberlain, South Dakota to Beresford, South Dakota to Storm Lake, Iowa line. The highest probabilities lie across southwest Minnesota. The ensembles spread increases up to a foot of snow where the probabilities span from a 20-60% chance, highest again across southwest Minnesota. This combination of wind and snowfall looks to bring the most impactful winter storm of the season to the area. While details can change heading into this event, please continue to monitor the latest forecast for the most up to date information.

The rest of the next week looks to begin on the cold side and slowly warm throughout the week. There could be additional chances for snow during the middle of the week but details are uncertain.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 639 AM CDT Fri Mar 13 2026

Northwest winds still gusting 25-45kt at the start of this TAF period (strongest in southwest Minnesota). These will gradually decrease through the day, with light/variable winds becoming prevalent tonight.

MVFR stratus is fairly widespread early this morning, but has been breaking up around the western and southern periphery over the past couple of hours. This stratus is expected to likewise diminish through the morning, with VFR conditions prevailing this afternoon and evening. MVFR ceilings and MVFR-IFR visibility will redevelop in a band of light snow after 14/06Z, mainly north of I-90 though KFSD could see brief MVFR visibility.

FSD WATCHES/WARNINGS/ADVISORIES

SD...Winter Storm Watch from Saturday evening through Monday morning for SDZ040-056-062-066-067. Winter Storm Watch from Saturday evening through late Sunday night for SDZ038-039-052>055-057>061-064-065. MN...Winter Storm Watch from Saturday evening through Monday morning for MNZ071-072-080-081-089-090-097-098. IA...Winter Storm Watch from Saturday evening through Monday morning for IAZ001>003-012>014-021-022-032. NE...None.