textproduct: Bismarck

KEY MESSAGES

- Accumulating snow expected across much of southern North Dakota Wednesday into Thursday, with amounts generally around 3 to 6 inches.

- A more significant snow event could impact the region Friday into Saturday, with medium to high chances for at least 6 inches of snow across much of southern North Dakota.

- Cloudy and breezy with well below normal daytime temperatures of highs in the 30s through Saturday.

UPDATE

Issued at 654 AM CDT Wed Apr 1 2026

Some very light snow is being reported under the reflectivity that stretches along I-94 as of 645 AM CDT, but the recently launched upper air sounding at Bismarck does show a layer of low RH from the surface to around 800 mb. The larger picture forecast for today remains on track, but rapid-refresh guidance is still inconsistent on the finer details of snowfall throughout the day. Also not mentioned in the previous full- length discussion, there is potential for stratus to lower near the surface of the higher terrain across western North Dakota later tonight into Thursday morning, which may create areas of fog.

DISCUSSION

Issued at 431 AM CDT Wed Apr 1 2026

Two separate systems will bring impactful winter weather to much of southern North Dakota today through Saturday, with lower chances for impacts farther north.

A shortwave trough is ejecting off the mountains of Wyoming early this morning into an area of increasing warm air advection and under the right entrance region of a weak upper level jet streak. Despite these forcing mechanisms translating across the Northern Plains through today, deterministic guidance shows the strongest forcing from each specific mechanism, or at each layer of the troposphere, to be disjointed. This has resulted in high variability of run-to- run snow accumulation outcomes, both for high and coarse resolution models. From a big-picture point-of- view, the highest snow probabilities through tonight are focused over south central North Dakota across all ensemble systems. However, there is a clear dichotomy between the ECMWF ensemble (higher maximum snow amounts) and GEFS (lower maximum snow amounts). The HREF generally favors a snowier outcome with high probabilities for exceeding 3 inches, but only low point- specific probabilities for exceeding 6 inches. A closer examination of HREF members though reveals a highly variable and somewhat chaotic footprint of potential snow amount outcomes, and every member simulates a system maximum of at least 6 inches of snow somewhere. The disorganized nature of the forcing is likely the key culprit in the wide variety of outcomes. Also in play is the potential for transient pockets of strong upward vertical motion through the dendritic growth zone that also contains steep lapse rates that could locally enhance snowfall rates.

The initial shortwave is forecast to get wrapped into a deepening Colorado low system that moves from the Great Plains to the Upper Mississippi River Valley on Thursday. There has been and continues to be a high degree of uncertainty on the western extent of the precipitation shield on Thursday. For example, the 06Z HRRR shows just pockets of lighter snow as far west as Highway 83 late Thursday morning, while the 06Z NAMnest shows a large shield of persistent light snow as far west as Highway 85 at the same time. We still anticipate that today will be the more impactful day across our forecast area. NBM snow threshold probabilities from today through Thursday afternoon across the Winter Weather Advisory are generally high for at least 2 inches, medium for 4 inches, and low for 6 inches. But again, there is high spatial variability, particularly in the experimental NBMv5.0 that more heavily weighs high-resolution output at short forecast time ranges. There continues to be a consistent signal for the highest +6" probabilities along the sloping terrain of western LaMoure and Dickey Counties, where snowfall and orographic enhancement from east-southeast surface winds are forecast to have the longest residence time.

The second system appears to be more straightforward, but also more impactful. A stronger upper level low that is already approaching the coast of the Pacific Northwest today will cross the Northern Rockies on Thursday and eject into the Northern Plains on Friday. There is still the typical timing and location uncertainty that can be expected at this forecast time range, but every ensemble cluster shows a mean closed 500 mb low crossing the region from Friday into Saturday. While there could be some embedded mesoscale banding at times, this primarily appears to be a synoptic-scale forcing event with intense Q-vector convergence in the presence of the left exit region of a strong upper jet. This lends to higher confidence in ensemble- based snow projections. The latest iteration of the NBM has taken a notable jump higher, now painting a 70 percent chance or greater for at least 6 inches of snow along and south of a line roughly from Bowman to Washburn to Carrington. The 50th percentile snow amounts are in the 1 to 3 inch range along and north of Highway 2, and also extending back down into McKenzie County. The highest 50th percentile amounts of around 10 inches are focused from around Lake Oahe to the southern James River Valley.

Daytime temperatures will remain well below normal through this stretch of active weather, with highs only in the 30s through at least Friday. Saturday could begin to see a slow warming trend, depending on the departure timing of the stronger low. A warming trend is then favored through the first half of next week, but that could be temporarily delayed in areas that receive the highest snow amounts through the end of this week. Breezy conditions are also expected at times through the stretch of active weather, but strong winds are not anticipated. Major impacts from blowing snow appear very unlikely at this time, especially outside of falling snow due to its higher liquid content.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 654 AM CDT Wed Apr 1 2026

Areas of snow are forecast across southern North Dakota throughout the day, then refocusing over the eastern half of the state through tonight. Periods of MVFR to IFR visibility can be expected under falling snow. MVFR ceilings are forecast to develop across all of western and central North Dakota from mid morning through the afternoon, falling to IFR this evening and LIFR at most terminals overnight. Areas of freezing fog or mist could reduce visibility across the western half of the state tonight, but not anticipating a widespread dense fog event at this time. East-southeast winds around 10-20 kts are expected through the forecast period.

BIS WATCHES/WARNINGS/ADVISORIES

Winter Weather Advisory until 1 PM CDT /noon MDT/ Thursday for NDZ018>020-033-034-041-042-044-045. Winter Weather Advisory until 7 PM CDT Thursday for NDZ021>023- 025-035>037-046>048-050-051.