textproduct: Bismarck

KEY MESSAGES

- Snow and blowing snow with significantly reduced visibility today into early this evening in far south central and southeast North Dakota, including the James River Valley.

- Windy and cold today, with wind chills from 20 below to 30 below zero.

- Decreasing winds tonight, but still cold with lows 5 below zero to 15 below zero.

DISCUSSION

Issued at 402 AM CST Sun Dec 28 2025

Windy and cold weather is expected today, with snow and blowing snow impacts in parts of south central ND into the James River Valley. Continued cold temperatures are expected tonight, but winds will diminish. The early-week forecast will be relatively quiet with no impacts expected, though by midweek, medium chances of snow return to the forecast.

Early this morning a band of moderate snow continues to slowly progress through central ND, with visibilities occasionally as low as 1/2SM, but more commonly in the 1-2SM range, with snow accumulations on the order of 1-2 inches being observed so far. This snow band does appear to be moving a bit more slowly east than expected earlier, which may be the result of the middle- and upper-level flow being more southerly ahead of the upper- level low which is located in northeast MT at this hour. Water vapor imagery suggests that low may be a touch further south than many model simulations had suggested previously. That in turn may be resulting in the more meridional (southerly) flow aloft downstream and a slightly slower eastward progression of the snow band, which is being driven by an area of strong midlevel frontogenesis. The guidance that appears to have the best handle on the placement of the upper-level low supports observational trends in suggesting the band of moderate snow will move through the James River Valley through mid morning, with reduced visibilities in falling and blowing snow even if total accumulations remain on the order of 1 to 3 inches. As the upper-level low continues to move southeast, reaching southeast SD by this afternoon, an area of midlevel warm air advection and forcing on isentropic surfaces to its north suggests light snow will continue and/or "wrap-around" across the James River Valley through the day, even after the initial, frontogenesis- driven band of snow moves out of the area during the morning. NBM probabilities of 1 inch of snowfall in the James River Valley are high (70+ percent), and of reaching 2 inches are medium to high (on the order of 50 to 70 percent). As will be discussed further below, where falling snow overlaps with strong winds in the James River valley and parts of south central ND, significant blowing snow is expected today and into this evening.

We also included low chances of snowfall in central ND today in respect to uncertainty with how far west the "wrap-around" light snowfall will extend, and in parts of western ND this morning as the upper-level low itself crosses that part of the state.

A strong surface pressure gradient is forecast across the state today as an Arctic high pressure system on the order of 1040 mb approaches from southwestern Canada, and as a strong surface low pressure system rapidly deepens while moving across the Midwest and into the Great Lakes. The result will be a windy day, with forecast soundings suggesting mixing of 30 to 40 kt winds at the top of the boundary layer. Blowing Snow Model output suggests significant blowing snow in parts of south central ND and the James River valley, with visibilities of 1/2SM or occasionally as low as 1/4SM expected where falling snow combines with strong winds. Without significant pre-existing snowpack, the blowing snow impacts will be highly sensitive to falling snow, and how much snow falls given the relatively low accumulations that we are expecting. This does raise some uncertainty in the forecast, but we have high confidence in advisory-level blowing snow impacts where the Winter Weather Advisory has been issued. A low probability does exist for blizzard conditions to develop in parts of the advisory area, if snowfall rates become high enough. While that's a low-predictability outcome, it's a scenario we will be monitoring for closely in observational trends.

We did opt to extend the Wind Advisory in far southwest and far south central ND through the day, where the surface pressure gradient remains strong enough for marginal advisory-level winds today. Forecast soundings are marginal for advisory-level gusts, and we did consider allowing the advisory to expire as scheduled early this morning, but opted to extend it given recent trends in observed winds.

We also expanded the Cold Weather Advisory south to include all of western ND through the morning, with observed wind chills on the order of -30 F becoming widespread as of 09 UTC. Wind chills are forecast to slowly rise out of advisory range by afternoon, but it's possible some part of that advisory will need to be extended later pending observed trends.

Highs today are forecast to only range from zero to 10 above zero. We expect lows tonight to range from 5 below to 15 below zero, lowest in western and north central ND closest to the surface ridge axis that is forecast to move from western and into central ND overnight. The air mass will modify somewhat by tonight as the upper-level low exists the area, but we did lean on the colder edge (near the 25th percentile) of ensemble membership for forecast lows tonight. That's based on the position of the surface ridge axis, expected efficient radiational cooling, and observed temperatures underneath the ridge axis upstream in Alberta and Saskatchewan that are in the -10 to -20 F range. It is possible that some areas of western and central ND may be even colder than forecast tonight based on those upstream observations. While winds will be diminishing tonight, and will become light in western ND, we may need to extend or re-issue another Cold Weather Advisory since even light winds may cause wind chills in the -30 F range where actual air temperatures are coldest.

Northwest flow aloft is expected to prevail for much of the upcoming week across the Northern Plains in between a strong Hudson Bay Low and ridging in the western United States. The synoptic-scale pattern has strong confidence from ensemble guidance through midweek, but the regime is expected to yield a strong baroclinic zone and related temperature contrast across the region. The exact placement of that frontal zone carries lower predictability, and will be influenced by weak impulses embedded in the northwest flow. NBM guidance has relatively low spread Monday and especially Tuesday, when a general warming trend is forecast. Highs by Tuesday are broadly forecast to be in the 30s F across much of the area, again, with low spread in ensemble membership, resulting in high confidence in that part of the forecast. However, beginning Wednesday the spread in NBM guidance remains large, on the order of 20 degrees or more. As an example, at Bismarck, the reasonable range outcomes for high temperatures on Wednesday (New Years Eve) is from 8 F to 31 F. Similar spreads in temperature forecasts then continue through the latter part of the week, both due to uncertainty in exact location of the frontal zone, and due to uncertainty in how amplified the northwest flow aloft will be. That's related to the progression of an upstream trough in the Pacific ocean. The bottom line is that the temperature forecast is more uncertain than normal from Wednesday onward, and should be expected to change for some days and locations with later forecasts.

Precipitation-wise, ensemble guidance continues to highlight the Tuesday night and Wednesday timeframe for medium probabilities of snowfall as an impulse crosses the region in northwest flow. We would expect an axis of snowfall along and to the cool (north) side of the baroclinic zone, wherever it ends up exactly by that timeframe. NBM probabilities of 1 inch of snowfall are high in north central ND and the James River Valley in the time period centered on Wednesday, with medium probabilities of 2 inches or more of snowfall. Those probabilities diminish further to the southwest part of the state. Otherwise, low chances of snow are also included in the forecast next weekend based on a consensus of ensemble guidance, too.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 402 AM CST Sun Dec 28 2025

A band of snow with IFR to local LIFR visibility and mainly MVFR ceilings will continue moving across central ND and the James River Valley overnight. Conditions will improve in western ND and parts of central ND as the snow band moves east, but some MVFR ceilings remain possible behind the snow band into Sunday. Snow and blowing snow will linger in the James River Valley including at KJMS into Sunday as the system slows its progression. Northwest winds gusting as high as 30-40 kt are expected area-wide through Sunday afternoon. The wind could combine with fresh snowfall to produce visibility restrictions from blowing snow, especially at KJMS and surrounding areas.

BIS WATCHES/WARNINGS/ADVISORIES

Cold Weather Advisory until noon CST /11 AM MST/ today for NDZ001-002-009-010-017-018-031>033-040-041-043-044. Winter Weather Advisory until 9 PM CST this evening for NDZ023- 025-036-037-046>048-050-051. Wind Advisory until 5 PM CST /4 PM MST/ this afternoon for NDZ040>045.