005
FXUS63 KBIS 060745
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
145 AM CST Sat Dec 6 2025

.KEY MESSAGES...

- Medium to high confidence in 1 to 3 inches of snow across
  most of western and central North Dakota tonight through
  Saturday, with locally higher amounts up to 4 inches.

- Medium confidence of light accumulating snow over much of
  western and central North Dakota again on Sunday, with
  accumulations to around an inch along and west of the Highway
  83 corridor.

- A more impactful system could bring strong winds along with
  both rain and snow (medium to high chances) across the region
  Monday night through Tuesday night.

- Temperatures drop to below average this weekend, above average
  Monday and Tuesday, then below average temperatures are favored
  again for the second half of next week.

&&

.UPDATE...
Issued at 144 AM CST Sat Dec 6 2025

Freezing drizzle has not been observed at Bismarck since the time of
the last forecast update, but there continues to be strong
indication through automated surface observations and webcams that
freezing drizzle continues to fall at least across Stark and western
Morton Counties.

So far, the heaviest snow associated with the incoming system has
been much farther north than 00z consensus guidance had favored. The
northern edge of the snow has generally lined up with the HREF
probability-matched mean contour of 1 inch. But the longest duration
snow has been up against that northern edge, and recent KMBX radar
imagery implies some higher rates with possible mesoscale banding
between Stanley and Minot, and as far north as Bowbells. Recent runs
of the RAP do have some enhanced 850 mb frontogenesis along this
axis, but it is farther upstream into northeast Montana and southern
Saskatchewan. However, the RAP does show this stronger frontogenesis
translating eastward along its major axis, which could promote a
longer duration of higher snow rates. Snow-to-liquid ratios are
already thought to be above climatology on account of the colder air
mass with a deep dendritic growth zone and steep mid to upper level
lapse rates. Even though our forecast snow amounts increased across
all of western and central North Dakota with this update, there is
potential for these higher amounts to be further exceeded along and
north of Highway 2 and west of Highway 83.

UPDATE
Issued at 1142 PM CST Fri Dec 5 2025

Quick update to add freezing drizzle to the forecast. Persistent
freezing drizzle was reported throughout the Bismarck/Mandan
area between 1030 PM and 11 PM CST. During this time period, the
KBIS METAR reported a 1400 ft ceiling and 8 mile visibility,
both unusually high for impactful freezing drizzle. Roads were
not observed to be slippery beyond their preexisting state, but
the freezing drizzle was causing windshields to ice over.
Because of the unexpected visibility and ceiling associated with
this freezing drizzle, and forecast soundings showing only weak
favorability for freezing drizzle production, it is difficult to
ascertain its spatial extent and impactfulness beyond the local
area. Any observing site reporting a lower ceiling and
visibility than KBIS was at the aforementioned time is likely
experiencing freezing drizzle. But as of 1130 PM CST, most sites
with these conditions were also reporting snow (from Lake
Sakakawea to the Souris River Valley, and extending west of the
Highway 52 corridor from Minot to the Canadian border). We have
updated the forecast to include freezing drizzle, with coverage
wording driven by recent observations until 2 AM CST, and then
patchy coverage until 6 AM CST. A Special Weather Statement has
also been issued addressing both the freezing drizzle and
expected increase of light snow.

UPDATE
Issued at 959 PM CST Fri Dec 5 2025

The forecast for tonight remains mainly on track. Increased the
timing of snow chances north central, otherwise the rest of POPs
tonight looking good based on radar returns to our west and
latest CAMs. No other major edits to the forecast at this time.

UPDATE
Issued at 632 PM CST Fri Dec 5 2025

Northwest flow aloft this evening continues, with a weak
embedded wave moving across the Dakotas. Weak sfc ridge of high
pressure extends across central North Dakota. A few reports of
light snow/flurries ahead of the mid level wave, with a mix of
low/mid level clouds. We remain on track for a swath of light
snow moving through the region later tonight into Saturday, and
only made some slight modifications to POPs with this update.

&&

.DISCUSSION...
Issued at 248 PM CST Fri Dec 5 2025

Currently, low pressure was situated along the lee of the Northern
Rockies with a cold and dry surface high pressure ridge  from
northern/central Saskatchewan into southern Manitoba. For the most
part, it was dry across the southern half of the state, in the north
associated with a weak inverted trough from northwest into east
central ND.

For late this afternoon into early this evening, there may be some
light snow continuing across the north and possibly a bit of
freezing drizzle with the loss of ice aloft, but in general think
this precip will be very light and on the decrease as high pressure
builds south from Canada.

Late this evening and overnight, cyclogenesis occurs in the northern
High Plains with a surface low depicted in the vicinity of eastern
Wyoming by 12Z Saturday. There is general agreement within the
deterministic model suite in synoptic scale forcing propagating
through southwest ND late this evening through Sunday morning. There
is less agreement in the extent of synoptic scale forcing outside of
the southwest portion of the state. There is also disagreement in
the placement of Frontogenetic forcing. The strongest FG forcing is
at 850 mb over the southwest portion of the state. 70H forcing is
generally along or north of the Canadian border. There is consensus
in moderate to steep lapse rates over most of western and central
ND. The NBM developmental guidance shows a medium to high
probability for at least an inch of snow along, south and west of
Lake Sakakawea and the Missouri River, from 00Z Saturday through 00Z
Sunday, with a medium probability for at least 2 inches of snow over
the far southwest. The probability for at least 4 inches is
generally less than 10 percent, but up to near 20 percent over east
central Montana and to near Beach in southwest ND. Thus given the
ensembles and deterministic guidance there looks to be little change
in the thinking from the previous shift. A medium to High
probability for 1-2 inches of snow south and west of the Missouri
River, with a low potential for up to 4 inches should banding
develop.

On Sunday, another impulse tracks southeast east across the forecast
area, along with warm advection ahead of a warm front.
Deterministic guidance seems to have bumped up the probability for
some light accumulating snows over western and central ND on Sunday,
but as of yet, there`s not much. The NBM is showing some medium
probabilities for an inch or more of snow in the southwest on
Sunday, with generally less than 15 percent chance over central ND.
Would not be surprised to see this increase a bit given the strength
of the wave, warm advection and the possibility of some higher snow
ratios over central ND on Sunday. In general though, light snow
accumulations expected with this feature as well.

We get a brief break on Monday before we see another, possibly
stronger wave track southeast across the region late Monday through
Tuesday. We do warm up on Monday and into Tuesday before we cool
back down for the latter half of the work week. There is still a lot
of uncertainty with this system, but it does look to bring a period
of stronger winds, with the potential for some accumulating snow
north and east, and some rain southwest, with the potential for a
wintry mix in between. Stay tuned!

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1142 PM CST Fri Dec 5 2025

Another round of snow tonight through the day Saturday. Also
could see a period of freezing drizzle from around KDIK to KBIS
through tonight.

Widespread MVFR to IFR ceilings and visibility in snow spreading
west to east across the forecast area tonight into Saturday. LIFR
ceilings/vis possible at times in any heavier areas of snow.
Winds will turn east to northeast tonight, then should be more
northeast on Saturday.

&&

.BIS WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Hollan
DISCUSSION...TWH
AVIATION...Hollan/NH