textproduct: Bismarck

KEY MESSAGES

- Dense fog across much of northwest and parts of central North Dakota through the rest of today.

- 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.

DISCUSSION

Issued at 254 PM CST Sat Dec 27 2025

There are multiple hazards through the short term period, with a low stratus deck and dense fog ongoing to start the afternoon, and an Arctic front that will bring strong winds, light snow, and colder temperatures.

This afternoon, a shortwave trough was digging over western Montana, with a surface low and attendant cold front moving from eastern Montana into western North Dakota. Ahead of these features, very low stratus and areas of dense fog have been persistent through the day, with satellite imagery revealing the stratus continuing to expand south as of this writing. It has been tricky determining where the Dense Fog Advisory needs to be, as some locations under the leading edge of the stratus are immediately in dense fog, while others have only marginally reduced visibility. Right now, we have the advisory in effect for northern and parts of central North Dakota, including parts of the James River Valley, until midnight tonight. Highp-res guidance has been consistent in showing the cold front scouring out the dense fog tonight, so would expect conditions to improve from west to east and western portions of the advisory will likely be able to be cancelled early.

Attention then turns to the Arctic front that is rapidly approaching the western edge of the forecast area. As expected, we are seeing an increase in wind speeds and much colder air moving in behind the front due to a bubble of pressure rises and low and mid-level cold air advection. A Wind Advisory goes into effect later this afternoon for portions of southwest and south central North Dakota where forecast soundings show wind potential generally up to 40 knots available at the top of the mixed layer. There is also a swath of light snow with the front, currently extending from northeast Montana back to just east of the Billings area. There is a low but non-zero chance for some light freezing rain on the leading edge of precipitation, depending on if there is any precipitation able to make it to the ground when the warm nose aloft still exists, but this is a very narrow temporal window before the column quickly cools and snow becomes the dominant p-type.

Snow amounts are expected to be light, with generally a half inch to an inch south and west, and 1 to 2 inches north central. The concern comes from this snow falling while there are strong winds with the front, which will lead to reduced visibility, potentially significantly reduced. Looking at upstream observations, it is reasonable to assume that visibilities could drop as low as one half of a mile for a brief period of time, but modestly low visibilities could persist for a few hours at any one location as the main swath of snow moves through. The front and associated snow will move into western North Dakota this afternoon, slowly pushing east through the night and exiting the area by Sunday morning. The main message we are emphasizing is that even though not much snow is expected, travel could still become hazardous due to the strong winds and blowing snow, especially in open country.

As arctic air filters into the region, temperatures will drop quite a bit tonight, and with the strong winds, wind chills will range from 20 to 35 below zero. We have issued a Cold Weather Advisory for part of western North Dakota to account for this hazard, in effect overnight tonight through Sunday morning.

While the upper low tracks southeast and becomes more stacked through the day Sunday, strong winds and likely some light, wraparound snow will continue through daytime hours and potentially into the evening, depending on how quickly the system exits the region. A Wind Advisory might be needed for parts of the south central and James River Valley on Sunday, but will let the next shift evaluate this more. Otherwise, Sunday will be much colder, with forecast highs generally in the single digits above zero. With surface high pressure building in later Sunday into Monday, Sunday night will be quite cold, with forecast air temperatures generally from 5 to 15 below for the entire forecast area. Additional cold weather headlines may be needed.

Cluster analysis for the start and middle of next week shows that ensemble members agree on the broad synoptic pattern featuring a deep Hudson Bay low and subsequent northwest flow across the Northern Plains. Temperatures warm quickly back into the 30s by Tuesday, with generally low chances for precipitation Monday and Tuesday. Blended guidance is painting a general 20 to 40 percent chance of light snow late Tuesday night through Wednesday as an embedded shortwave traverses the cyclonic flow. Right now this looks like a relatively benign system, with NBM 5.0 probabilities for at least 2 inches of snow topping out around 30 percent.

NBM temperature percentiles have been consistently advertising a very large range in potential high temperatures on New Year's Eve, signaling that there is uncertainty on where the baroclinic zone ends up, which will influence surface temperatures. This signal continues through the end of the week, although spread is highest on New Year's Eve. There is more confidence in the general pattern of a large temperature spread across the area, with coldest temperatures north central to warmest southwest. There could also be some wind chill concern for New Year's Eve night into New Year's Day morning, with current NBM deterministic low temperatures 10 to 15 degrees below zero in north central North Dakota. To end the week and start the new year, there is still uncertainty in the progression of an eastern Pacific trough, with the aforementioned large spread in NBM temperature percentiles. For now, blended guidance keeps a dry forecast on Thursday and Friday before chances for snow return for the weekend.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1215 PM CST Sat Dec 27 2025

Very low ceilings and areas of dense fog continue across parts of northern North Dakota and the James River Valley, including KXWA, KMOT, and KJMS, with IFR to LIFR conditions. This activity is likely to continue through much of the evening before improving west to east as a cold front sweeps through the state. Behind the front, winds will become northwest and gust up to around 35 knots. Light snow is also expected with the front, with a period of MVFR to IFR visibilities for a few hours as snow is falling. MVFR to IFR ceilings are also expected behind the front, including across southwestern ND where VFR conditions will be present during the day today (until the front arrives late).

BIS WATCHES/WARNINGS/ADVISORIES

Dense Fog Advisory until midnight CST /11 PM MST/ tonight for NDZ001>005-009>013-017-021>023-025-037-048-051. Cold Weather Advisory from midnight CST /11 PM MST/ tonight to noon CST /11 AM MST/ Sunday for NDZ001-002-009-010-017-018. Wind Advisory until 6 AM CST /5 AM MST/ Sunday for NDZ040>045.