textproduct: Bismarck

KEY MESSAGES

- Low to medium chances for freezing drizzle moving from northeast to southwest across western and central North Dakota this morning.

- Medium to high chances for light snow accumulations (less than an inch) north central into the northern James river Valley this morning. Low chances for at least an inch of snow around the Turtle Mountains.

- Low chances for fog developing northwest and central this morning. - Mild temperatures in the upper teens to upper 20s tonight. Then temperatures falling through the day Wednesday for most areas. Highs northwest and central will be early in the day. Still mild southwest though, with highs in the lower 30s.

- Large spread in temperatures from northeast (colder) to southwest (warmer) through the end of the week.

DISCUSSION

Issued at 345 AM CST Wed Dec 31 2025

Cyclonic flow is found over the northern Plains this morning. A backdoor cold front, trailing off a low pressure system cutting across far northeastern North Dakota, is slowly making its way to the southwest this morning. Along and behind this front, light snowfall has developed across northeastern North Dakota into the Turtle Mountains area, and is expected to slide off to the southeast through this morning. Overall accumulations over north central North Dakota into the northern James River Valley are expected to be light, a few tenths of an inch to an inch at most. Of greater interest for western and central North Dakota is the potential for freezing drizzle this morning. While a dry DGZ is expected to persist across much of the forecast area, the first 1.0-1.5km the column is expected to saturate along and behind the cold front as it moves to the southwest. An interrogation of BUFKIT model soundings indicates that upward motion is anticipated through this saturated layer, which would induce freezing drizzle for some time behind the cold front itself. The two biggest questions are the following:

What is the potential coverage of freezing drizzle? Model soundings indicate that the DGZ in far north central North Dakota should remain saturated enough that light snow can be anticipated. In the far southwest, where front is expected to stall by the late morning and early afternoon, a much more shallow near surface saturated layer is anticipated. With that in mind, and with upward vertical motion through even this shallow layer being limited as the cold front stall, freezing drizzle is less likely. Elsewhere, conditions appear for a low to medium chance of freezing drizzle this morning.

Will surface conditions behind the front cool quickly enough to cause a transition from freezing drizzle to flurries? The expectation is that surface temperatures below -10C would allow for freezing drizzle to become flurries. Cross referencing the time between saturation of the first 1.0km of the column, and the HREF probability of temperatures dropping below -10C, there seems to be a 2 to 4 hour period during which freezing drizzle would be anticipated at any given location. This timeframe falls in line with past observations, in which areas in the northeast have taken around 3 hours for temperatures to drop below -10C once winds switch from the west to the north northeast (i.e. when the cold front passes over them).

With that in mind, we have issued an SPS for much of western and central North Dakota to message the low to medium potential for a very light glaze of ice on elevated and untreated surfaces this morning. Freezing drizzle should diminish through late this morning as surface temperatures continue to drop, and upward motion diminishes with the stalling of the front. Another period of precpitation is possible this afternoon across the northwest tonight through Thursday morning across portions of north central North Dakota into the northern James River Valley as a strong jet streak and moderate FG forcing develops across the northeast. With this forcing expected on the cool side of the baroclinic zone, all precpitation is expected to fall as lightly accumulating snow. Overall amounts are anticipated to be limited to a few tenths of an inch up to an inch at most, mainly as conditions within the DGZ dry out through early to mid Thursday morning. Light flurries will be remain possible over this area through early Thursday afternoon.

Otherwise, for today, low stratus and patchy to areas of fog are possible along and behind the baroclinic zone this morning. Any fog that does develop may linger in the southwest through this afternoon, before again redeveloping and spreading to the northwest and south central overnight into Thursday morning with the next round of precpitation. A strict temperature gradient from northeast to southwest will be found across the state today due to the aforementioned baroclinic zone. Lows this morning are from around zero northeast up to the lower 20s in the far southwest. Highs this afternoon are from around 5 above northeast to the mid 30s southwest.

Conditions through the remainder of the week are expected to remain more or less the same. Cyclonic flow over the northern Plains is expected to persist, though with a ridge building in across the west a slight warming trend can be anticipated through this weekend. Periods of light precpitation can be anticipated if an when any transient shortwave slides down the general flow pattern, with the ensemble highlighting low to medium chances for light, non- accumulating snow across the northeast late Friday through Saturday, and again late Saturday through Sunday. A pattern shift can be anticipated some time during this period as the aforementioned building ridge finally displaces the Hudson Bay Low, though ensemble members remain fairly discordant on when this occurs, and what type of pattern develops after this point. Broadly speaking, the majority of model members (70 percent) favor near to above normal temperatures and mainly dry conditions across the forecast area by early next week, mainly as broad ridging develops across the northern Plains. A much cooler and wetter solution also exists (30 percent of model members) however, as the ridge is flattening by an pacific trough by the mid week. These clusters are not well dispersed, however, with 90 percent of GEFS members in the cooler solution, and 100% of the ENS AND GEPS in the warmer solution.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/

Issued at 345 AM CST Wed Dec 31 2025

MVFR ceilings continue to the east of KMOT and KBIS to begin the 06Z TAF period. Areas to the northeast of KMOT and KJMS are likely to see a period of light snow later tonight, with IFR visibility and ceilings. But this should not reach either of those TAF sites. There could also be some patchy fog developing over south central North Dakota during the overnight hours.

A northwest-to-southeast oriented cold front will move from northeast to southwest across western and central North Dakota late tonight through Wednesday morning. The frontal passage could bring a variety of aviation impacts to all terminals, including 1) an initial period of IFR to LIFR ceilings and freezing fog/mist reducing visibility; and 2) a 2 to 4 hour period of light freezing drizzle trailing the front, with mostly IFR ceilings. The chance of freezing drizzle becomes lower as it reaches southwest North Dakota around midday, but IFR ceilings appear likely to persist from KXWA to KDIK through the afternoon, along with MVFR ceilings from KMOT to KBIS to KJMS. It could also remain or become foggy in southwest North Dakota through Wednesday afternoon.

Westerly winds around 5-10 kts through this evening will turn to the northeast with the passage of the cold front.

BIS WATCHES/WARNINGS/ADVISORIES

None.