262
FXUS63 KBIS 081830
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1230 PM CST Mon Dec 8 2025

.KEY MESSAGES...

- A strong low pressure system will bring high-impact weather to
  western and central North Dakota late tonight through Tuesday
  night.

- Medium to high chances for freezing rain across northwest and
  central North Dakota late tonight through Tuesday morning,
  with ice accumulations as high as one tenth of an inch.

- Very strong winds expected late Tuesday morning through
  Tuesday night, with gusts as high as 65 mph possible.

- Medium to high chances for accumulating snow in the Turtle
  Mountains area Tuesday morning through Tuesday evening.

- Medium to high chances for another round of light accumulating
  snow across all of western and central North Dakota Wednesday
  afternoon through Thursday night.

- Above average temperatures today through Tuesday, then below
  average expected for the rest of the week. Friday could be
  very cold with dangerous wind chills.

&&

.UPDATE...
Issued at 1230 PM CST Mon Dec 8 2025

Clouds are clearing in the west and central behind the warm
front. Winds are starting to pick up in the west as well. The
latest NBM was loaded into the forecast. We used NBM 90th for
winds and wind gusts again for Tuesday.

UPDATE
Issued at 1010 AM CST Mon Dec 8 2025

The surface warm front is still moving east through the state.
The southwest has already warmed to the upper 30s, and skies are
clearing out west. Light snow is falling along and east of
Highway 83, along with patchy areas of fog. The rest of the
forecast remains on track. We will be upgraded the High Wind
Watch at some point today, we are just waiting for the 12z
models to determine what counties will be in a Advisory vs
Warning.

UPDATE
Issued at 655 AM CST Mon Dec 8 2025

Surface observations and webcams continue to indicate an area of
fog/ice crystals reducing visibility from around Stanley to Linton
and Ashley, with occasional quarter mile visibility being reported.
A Special Weather Statement has been issued to address the patchy
dense fog.

Radar reflectivity shows scattered light precipitation across
western North Dakota. If any of this is reaching the ground, for
which there has yet to be any confirmation, it is likely reaching
the surface as freezing rain. We continue to expect only trace
amounts of precipitation with this activity, and therefore very
little to no impacts from icing.

&&

.DISCUSSION...
Issued at 512 AM CST Mon Dec 8 2025

A weak clipper system embedded in northwest flow is approaching
the region early this morning, with a surface low analyzed over
southern Saskatchewan. Widespread stratus downstream of the low
has persisted much longer than expected over the eastern two
thirds of North Dakota, and central parts of the state have
experienced areas of fog and/or ice crystals along the western
edge of the stratus. The stratus and fog are expected to
diminish with the arrival of the warm front attendant to the
low, which was approaching the MT/ND border at 4 AM CST. As this
warm front moves across the western half of the state through
this morning, it could produce some very light freezing rain or
snow. There is a dry layer of low level air in place that should
limit any snow or ice accumulation to trace amounts at most.
There is an exception to this though from the greater Turtle
Mountains area into the Devils Lake Basin where CAMs are in good
agreement that a burst of snow, possibly mixed with freezing
rain or sleet, will cross the area mid to late morning as the
surface low moves toward the northern Red River Valley. Both
operational and experimental NBM guidance show medium to high
probabilities for measurable snow, but very low probabilities
for exceeding 1 inch through this afternoon. Elsewhere, expect a
windier but warmer day with highs mostly in the 30s and
westerly winds around 20 to 25 mph, gusting as high as 35 mph in
the afternoon.

A well-advertised powerful clipper system will begin to impact
the region late tonight, with impacts continuing through Tuesday
night. Global ensembles show remarkable consistency on the
track of the surface low, with only negligible differences in
its path among the means of all clusters. Timing is only
slightly more inconsistent, with a couple of GEFS-heavy clusters
slower than the other two. However, the 00z HREF is distinctly
shifted northeastward from the global ensemble means. The
greatest difference in expected impacts on account of this
uncertainty would be along and to the north and east of Highway
52, where the southern global models solution would result in
higher chances for snow, not as strong winds, and lower chances
for ice accumulation, and the northern HREF solution would favor
the opposite. Keeping this uncertainty in mind, each important
aspect of this system is discussed below, and there is high
confidence in each of the three main impactful phenomena
occurring somewhere.

Freezing Rain:

- Broad warm air advection is forecast to initiate widespread
  light precipitation from west to east late tonight into early
  Tuesday morning. There are high probabilities for maximum
  temperatures aloft above freezing, except in the Turtle
  Mountains area where these probabilities are still at medium
  values. Surface temperatures will begin warming at all
  locations near the onset of or prior to rain reaching the
  surface, but temperatures at the starting time of this warm up
  are favored to be from around freezing in the southwest to
  several degrees Fahrenheit below freezing northwest and
  central. Temperatures are forecast to rise above freezing
  prior to sunrise in the southwest, with the freezing line
  progressing northeastward and approaching the Turtle Mountains
  area no later than noon. There is medium to high confidence
  in a period of light freezing rain across a large portion of
  northwest and central North Dakota late tonight through
  Tuesday morning, with ice accumulations around a few
  hundredths to as high as one tenth of an inch. It is worth
  noting that the HREF shifts its mean maximum ice accumulation
  as far northeast as Bottineau to Rugby and has no ice
  accumulation to the south and west of the Missouri River,
  likely due to both its northward shift of the system as a
  whole and also temperatures warming quicker than what the NBM
  projects. If confidence in this freezing rain forecast remains
  this high or increases further, a Winter Weather Advisory
  will likely be needed.

Snow:

- Snow probabilities have shifted northward and decreased at
  higher thresholds (2 inches and above), even in global
  ensembles. The HREF understandably has its snow amounts
  shifted even further north, with the 1-inch contour in its
  probability- matched mean (PMM) not even reaching Rugby and
  barely touching Bottineau. The PMM does however show 4-6
  inches within the Turtle Mountains. Meanwhile, the latest
  global ensembles still project a 50 percent chance of 1 inch
  of snow as far south and west as Highway 52.

Wind:

- Wind remains the most concerning aspect of this system. There
  is high confidence in a 50-60+ kt 850 mb jet crossing the
  region from northwest to southeast, with all favorable
  ingredients for maximum momentum transfer present. The
  northeastward extent of high-impact winds remains uncertain,
  with CAMs bringing a period of near to above warning criteria
  winds to our entire forecast area, while global ensembles keep
  probabilities for 850 mb winds exceeding 50 kts to the south
  and west of Highway 52.

Other Considerations:

- Snow that is already on the ground should not be blowable by
  the time the strong winds arrive on account of above freezing
  temperatures both today and Tuesday and the period of light
  rain/freezing rain that is anticipated late tonight through
  Tuesday morning. It goes without saying that any combination
  of strong winds with falling or freshly fallen snow would be
  concerning. In theory, the overlap between the strongest winds
  and highest snow amounts should be minimal, however far north
  or south that zone may end up. It is a little disconcerting
  though that the HREF brings both higher snow amounts and very
  strong winds to the far northeast reaches of our forecast
  area. Our wind and snow forecast, which is heavily rooted in
  the NBM, is more reflective of the global models solution that
  keeps impactful winds away from most of the accumulating
  snow. Nevertheless, our blowing snow model does show medium
  probabilities for visibility less than half a mile just
  outside our forecast area from around Devils Lake to
  Cooperstown.

- There is a low end potential for snow squalls with the main
  punch of colder air Tuesday afternoon and evening. Several
  necessary ingredients are forecast to be present, but it is
  far from certain if or where they may line up. It is also
  possible that it could be just rain instead of snow if this
  were to happen far enough to the southwest.

- A flash-freeze is highly likely Tuesday evening through the
  night. Midday temperatures in the mid 30s to mid 40s are
  forecast to fall into the mid teens (north) to mid 20s (south)
  by mid evening.

A persistent active northwest flow pattern remains favored to
continue through the weekend. Forecast highlights include
periodic medium chances for additional rounds of accumulating
snow and much colder temperatures. Beyond Tuesday, the highest
snow chances are in western North Dakota Wednesday night into
Thursday, and there is also now a signal for a period of mixed
precipitation types in the southwest over this time frame. Below
average temperatures are favored from Wednesday through the
weekend, but there is medium to high confidence in Thursday
night through Friday night being an exceptionally cold period.
The NBM continues to favor lows in the teens below zero each of
these nights, and highs on Friday below zero for most locations.
There is also concern for a longer duration of hazardous to
dangerously cold wind chills, with minimum values as low as 35
to 45 below zero Friday morning.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1230 PM CST Mon Dec 8 2025

MVFR to VFR today. Patchy fog in the east is creating MVFR VIS
and SCT CIGs of 400ft. Winds will be westerly and breezy this
afternoon before gusting near 50kts Tuesday. Periods of freezing
rain is likely early Tuesday morning before switching to rain
through Tuesday.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from Tuesday morning through late Tuesday
night for NDZ001-002-009>011-017>022-031>036-040>048-050-051.
High Wind Watch from Tuesday afternoon through late Tuesday
night for NDZ003>005-012-013-023-025-037.

&&

$$

UPDATE...Smith
DISCUSSION...Hollan
AVIATION...Smith