textproduct: Bismarck

KEY MESSAGES

- Dense fog across much of northwest and parts of central North Dakota this morning, potentially lingering into the afternoon.

- High chances of lightly accumulating snow and gusty winds tonight, and reduced visibility while snow is falling.

- Wind gusts up to 45 mph in far southwest and south central North Dakota late this afternoon through tonight.

- Gusty winds and very cold temperatures tonight through Sunday night, with wind chills as low as 30 below zero possible.

DISCUSSION

Issued at 427 AM CST Sat Dec 27 2025

A significant change in the weather is expected the next 24 hours as an Arctic cold front crosses the region. Until the frontal passage occurs tonight, concerns for dense fog will persist over parts of the area today.

As of 10 UTC, dense fog with visibility from 1/4SM to 1/2SM is persisting along and north of a line from Columbus in Burke County to near Garrison, Carrington, Jamestown, and Oakes. This is generally along and north of a diffuse warm frontal zone, where light low-level winds, a strong low-level inversion, and a relatively deep low-level saturated layer persists. The frontal zone has nudged slightly northward overnight, as expected, with the KBIS VAD wind profiler sampling increasing and veering winds that are west-southwest near 30 kt around 1000 ft AGL the last few hours. This is consistent with the slow north-northeast progression of the warm frontal zone, and related shallowing of the low-level moisture that has led to dissipation of the dense fog in parts of south central ND. That in turn has allowed us to cancel parts of the Dense Fog Advisory in south central ND where observations have shown increased visibility trends. However, we actually extended the end time of the Dense Fog Advisory until 18 UTC (Noon CST) in north central ND into the James River Valley. Overnight model guidance has suggested persistence of the dense fog longer than previously expected, especially across north central ND. This results from a longer period of weak low-level flow in those areas than earlier simulated, even as flow around 850 mb turns more westerly during the day today. We extended a mention of fog into the afternoon and early evening in north central ND into parts of the James River valley, and it's possible later updates will need to extend some parts of the Dense Fog Advisory past 18 UTC.

Meanwhile, radar has shown a modest increase in reflectivity in central ND the last few hours in an area that's broadly within the exit region of a 100-120 kt 250 mb jet streak, in an area of modest midlevel frontogenesis, and near the west side of mid- level warm air advection that is focused in northeastern ND. The stratus deck in central ND has appeared to be a bit too shallow for freezing drizzle production despite the latter ascent in the form of warm air advection (unlike in northeastern ND closer to Grand Forks, where the stratus deck has been deeper, intersecting with that low and midlevel ascent). Nonetheless, the attempts at precipitation development in central ND are worthy of including a low (20 percent) chance of light freezing rain the forecast in parts of central and moreso north central ND through early this morning. This is very conditional given dry air aloft, and thus far the radar representation would suggest only low odds of any precipitation actually reaching the ground.

Highs today will range from 35 to 45 F in southwest and parts of south central ND, along and south of the warm frontal zone, to the 20s where stratus and fog persist in northern ND.

The approaching Arctic cold front is surging through southern Alberta and into north central MT as of 10 UTC (4 am CST), with temperatures in its wake rapidly falling into the zero F range. Guidance expects the shortwave trough attendant to this front and the front itself to reach western ND late this afternoon, and to cross central ND this evening. The front is forecast to be accompanied by strong low- and midlevel cold air advection, reflected by moderate to strong isotherm packing at 850 mb, and 3-hour surface pressure rises of 8-10 mb crossing southwestern and south central ND late this afternoon and evening. Midlevel winds are forecast to only peak around 35-40 kt, but the cold air advection and strength of the surface pressure rises are supportive of gusty northwest winds following the front. The strongest winds are expected in far southwestern and south central ND, where we have issued a Wind Advisory for gusts up to 45 mph late this afternoon through tonight.

A band of light snow is expected to follow the front from west to east tonight, with high probabilities of light snow on the order of a dusting to one-half inch. There are only low, ~20% probabilities of an inch or more of accumulation, though. This will be driven by a surge of low- and midlevel frontogenesis following the surface frontal passage, augmented to at least some extent from broad synoptic-scale ascent. Some blowing snow is also expected due to the light falling snow and gusty winds.

On Sunday, the cold Arctic air mass will be in place over the area, and ensemble guidance has low spread in calling for highs only from zero to 10 above. A notable surface pressure gradient will exist as a surface low rapidly deepens in the Midwest and Great Lakes region, and forecast soundings show a well-mixed layer extending into midlevel winds of 35 to 40 kt across much of the area. The result will be a windy day, with low to medium probabilities of needing a Wind Advisory. We do note that EFI values are only marginally supportive of needing an advisory, and peak winds in the mixed layer are on the cusp of what is typically associated with advisory events. Either way, the winds and expected air temperatures will result in a very cold day, with wind chills of 15 below to 30 below zero across the area. We have medium to high confidence that a Cold Weather Advisory will eventually be needed for parts of the area, especially in northwest ND (perhaps beginning tonight). We will, however, allow later shifts to determine the exact layout of where the wind chill criteria of -30 F for the advisory will be met, and for how long.

Surface high pressure is expected to cross the area on Sunday night, resulting in the coldest night of the near term, with lows currently forecast to be from 5 below zero to 15 below zero, coldest in northwestern ND. Given the expected surface ridge axis location, the 10th percentile NBM lows which show more widespread lows of 10 below to 20 below zero is a very reasonable potential outcome in some areas.

Ensemble spread is relatively low early next week, and calls for a warming trend Monday and Tuesday as transient ridging crosses the region in mean northwest flow aloft. By midweek, the spread in ensemble members increases and remains significant, on the order of 20 degrees (e.g., NBM 25th to 75th percentile ranges for high temperatures at Bismarck range from -1 F to 22 F on Wednesday/New Years Eve). This is a result of uncertainty in how amplified northwesterly flow becomes in that timeframe, and where an associated significant frontal zone winds up located. The larger-scale flow uncertainty stems from differing outcomes in the speed and amplitude of a trough in the eastern Pacific, with a roughly 50/50 percent probability of either a warmer or cooler scenario locally in the latest ensemble cluster analysis. Despite the uncertainty, the ensemble consensus supports medium chances of light snow along and north of the aforementioned baroclinic zone, and we are including them in the forecast for the period centered on Wednesday.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/

Issued at 427 AM CST Sat Dec 27 2025

Widespread IFR to LIFR ceilings with dense fog will persist across much of northwest and parts of central North Dakota through the day today overnight.

A period of low-level wind shear has been added to the KBIS TAF through about 13z due to west-southwest winds around 30 kt that have developed around 1000 ft AGL.

A cold front is forecast to cross the state from northwest to southeast this afternoon and evening, bringing gusty northwest winds and a period of falling snow to most terminals, along with low ceilings returning across southern North Dakota.

BIS WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until noon CST today for NDZ001>005-010>013- 021>023-025-036-037-048-051. Wind Advisory from 4 PM CST /3 PM MST/ this afternoon to 6 AM CST /5 AM MST/ Sunday for NDZ040>045.