500
FXUS63 KBIS 110014
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
614 PM CST Wed Dec 10 2025

.KEY MESSAGES...

- Another round accumulating snow will start this evening
  through Thursday night. Areas of freezing rain are also
  expected across the west and south (including Bismarck/Mandan)
  through late Thursday morning.

- Below average temperatures are expected through the upcoming
  weekend, with dangerous wind chills Thursday evening through
  Sunday morning.

- More accumulating snow is possible across the west and south
  central Friday through early Saturday.

&&

.UPDATE...
Issued at 612 PM CST Wed Dec 10 2025

Snow is falling across much of western North Dakota early this
evening. The snow has been heavy at times, with visibility falling
as low as 1/2 mile. Surface observations and radar imagery already
show conditions improving near the Montana border, but a period of
freezing drizzle could follow the band of snow across much of
the area through tonight. This is separate from the band of
freezing rain that is forecast to set up over southwest North
Dakota later tonight. No headline changes for this update, but
eastward expansion may need to be considered if confidence in
freezing drizzle grows. The most notable forecast adjustment for
this update was to increase PoPs, especially in the near-term
to match what is being observed.


&&

.DISCUSSION...
Issued at 250 PM CST Wed Dec 10 2025

Currently in the Northern Plains northwest flow is giving way to
zonal flow off the Pacific Ocean. This zonal flow is part of the
Atmospheric River event on going in Washington. This will add
ample moisture to the incoming low pressure system already in
north central Montana. A stationary front is extending off the
low through southeast Montana and western South Dakota. Moisture
ahead of the system has extended into central North Dakota,
creating light snow in a few locations.

The Storm:

The system will start as snow with the cold temperatures across
the west, ahead of the warm front. The front will slowly move
into North Dakota, enhancing the forcing and QPF with strong
frontogenesis along the front. The front will be located on a
northwest to southeast diagonal from just south of Williston to
Sioux County starting early Thursday morning. The strongest
fgen forcing will be between 4am CST and 11am CST. Very strong
flow in the jet stream located directly above the front will
also enhance the strength of the system. As the low moves closer
to North Dakota, the warm sector aloft will rotate into the
state. This will melt the falling snow in this layer into rain
that then will freeze on any surface. It will then switch back
to snow as a backdoor cold front cools the air aloft. Surface
temperatures in the far southwest will warm above freezing and
rain will then be the main threat there. The snow elsewhere will
continue through Thursday afternoon. Overall 1 to 2 inches of
snow is possible across all of western and central ND. The first
inch of snow will fall first, then freezing rain, then back to
snow in the wrap around and back door cold front. Up to two
tenths of an inch of freezing rain accumulation is expected in
the southwest and south central. The forecast challenge with
this system is 1. the QPF amounts and 2. the ice accumulation.
Models vary on the QPF amount. With snow accumulating first,
then freezing rain, the challenge is what will the ground
conditions be like with that combination. Will the rain soak
into the snow and not be raw ice on top, or will it glaze the
snow like a donut. For QPF we blended WPC`s forecast with the
NBM forecast, and then limited some of the freezing rain so we
didn`t get widespread amounts over 0.20 inches.

Timing:

The first round of snow will move into western North Dakota
before sunset, spreading east. By midnight CST the main band of
snow will reach the Missouri River in the southeast. This about
the same timeframe when freezing rain switches from the snow in
the southwest. Just after midnight the front will slide into
the southwest with the warmer air aloft, creating widespread
rain and freezing rain across the west, southwest and south
central. The highest chance of freezing rain will be when the
fgen increases starting around 3am CST and ending around 10am
CST. This will greatly affect the morning commute again, like
Tuesday. There will likely be 1 inch of snow on the ground with
freezing rain on top of that for your commute. After 10am the
main precip type will be snow, except in the southwest where it
will be rain. This will continue through Thursday evening.


The backside of this system will bring some very cold Arctic air
through the Northern Plains. Highs for Friday and Saturday will
be in the single digits below and above zero, with dangerous
low temperatures Thursday night through Sunday morning. Expect
wind chill temperatures between 20 and 40 degrees below zero. We
will need Extreme Cold Advisories and Warnings for this period.
This blast of cold air is part of surge of very strong
northwest flow, that will also create a low pressure off the
Rockies Mountains. In a converging zone between that low and the
high pressure entering northern ND, more snow is likely. Snow
amounts have been wavering but they seem to be around 3-5 inches
in the far southwest part of the state. The incoming high
pressure will limit the snow to the far southwest part of the
state, or push it out of the state. It will depend on the
timing of the high and how far it moves south. The snow will
linger through Saturday. The rest of the weekend will be cold
and dry as the ridge axis moves towards the state. The ridge
axis then moves into the state for Monday, warming temperatures
to above freezing through about the 17th of December.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 612 PM CST Wed Dec 10 2025

A band of snow will move from west to east across the state this
evening through tonight. Primarily IFR visibility with the snow, but
with some periods of LIFR possible. Trailing the snow is the
potential for a period of freezing drizzle or light freezing rain,
except in southwest North Dakota where a more persistent band of
freezing rain, transitioning to rain closer to the Montana
border, is expected through tonight. By 12Z, widespread
precipitation is expected along and south of a line from KXWA to
KJMS, with freezing rain (rain in far southwest North Dakota)
transitioning back over to snow.

Ceilings are forecast to lower through tonight, reaching at least
IFR at most terminals Tuesday morning. A southeast breeze around 10
kts will become light and variable late tonight into Thursday
morning, then northwest around 10-15 kts (strongest in western North
Dakota) Thursday afternoon.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM CST /5 PM MST/ Thursday for
NDZ009-010-017>021-031>035-040>046.

&&

$$

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