107
FXUS65 KTFX 050342
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
842 PM MST Thu Dec 4 2025

.KEY MESSAGES...

 - First round of snow tonight will primarily focus on the
   mountains of central and southwest Montana with significant
   travel impacts expected along the mountain passes.

 - A lull in heavy snow is expected late Friday morning through
   the afternoon.

 - The second round of snow will arrive late Friday afternoon and
   have more widespread impacts both in the mountains and
   potentially across the lower elevations.

&&

.UPDATE...

Northwest flow aloft will continue to bring down mini shortwaves
through the night. This will continue to bring snow across Central
and Southwest MT, with more moderate to heavy snow in the
mountains. Moderate to heavy snow should lighten up Friday
morning. Temperatures dropping down into the 20s to teens will
result in wet pavements refreezing overnight and cause slick
driving conditions. Current winter products in affect this evening
still remain on track. -Wilson

&&

.DISCUSSION...
/Issued 443 PM MST Thu Dec 4 2025/

 - Meteorological Overview:

There will be two rounds of heavy snow expected over the next few
days. The first round is ongoing and will last through Friday
morning with the most of the impacts expected in the mountains of
central and southwest Montana as well as Gallatin Valley and
Boulder Hill.

There will be a lull in the activity with lighter mountain snow
late Friday morning through late Friday afternoon with the second
wave of snow arriving by the evening. The second round will be
more widespread with the potential for lower elevation snow along
the valleys and northern plains.


 - Forecast Confidence & Scenarios:

The mountains will receive the heaviest amounts and are thus the
focus of the current Winter Storm Warnings. Travel along mountain
passes will be hazardous at times with reductions in visibility,
slippery conditions, and rapidly changing conditions among the
expected hazards. The hardest impacted passes and roads include
Kings Hill, Deep Creek, and Bozeman Passes and Highway 191 south
of Bozeman to the Idaho border. Motorists traveling along these
roads should carry an emergency kit in their vehicle and be
prepared for potential travel delays along their commute.


Gallatin Valley/Bozeman/Boulder Hill Snow:

While the heaviest amounts are still confined to the mountains,
there is increasing concern for impacts in Boulder Hill and Bozeman
proper tonight through Friday morning associated with this first
wave of snow. Travel concerns remain at the top of the list for
potential impacts. One particular concern is that the initial
snowfall will melt on the pavement and combine with any other
snowmelt from the day which will then refreeze as the night goes
on. This may create a thin layer of ice along area roads which,
with additional snowfall expected through the night, may make for
difficult travel at times. Because of the potential impact to
travel along with the 2 to 4 inches of snowfall expected through
tomorrow morning, the decision was made to put Gallatin Valley and
Boulder Hill in a Winter Weather Advisory.

Additional snowfall is expected with the second wave but because
there is a 12-18 hour lull in snowfall expected between rounds of
snow, for now, the focus will be on tonight and the potential
headlines for tomorrow will be addressed with later forecast
packages. Additionally there is some guidance in the hi-res models
that a snowband may set up around the Gallatin Valley at some
point with the second round which could produce higher snowfall
amounts and greater impacts in the Gallatin Valley which could
potentially make it a candidate for a warning tomorrow. But
because confidence is low in the snowband, Gallatin Valley will
not be added to a watch at this time. But folks in the area should
prepare for difficult driving conditions Friday evening through
Saturday morning as well.


Lower Elevation Snow Friday/Saturday:

There is growing confidence in a snowband setting up across
north-central Montana. The problem is this is turning out to be a
scenario of high confidence in a snowband occurring, low
confidence in where exactly the snowband sets up. What this means
for messaging of impacts is that most locations across the
northern plains can reasonably expect 1 to 2 inches of snow Friday
and Saturday with the second wave. Where the snowband sets up is
where locations may see 4 to 6 inches of snow with potentially
higher amounts locally. For now this appears to be a solid
advisory criteria event, however, there are some suggestions in
the models that a couple areas could reach warning criteria. But
because there is such low confidence in where the heavier snow
amounts will be located and things keep changing with every model
update, there is simply not enough to issue any headlines at this
point until updated hi-res model guidance arrives that gives a
clearer picture on what might unfold. In the meantime, folks
across the northern plains should be prepared for general winter
weather conditions with the understanding that if they are under
the snowband there could be periods of moderate to heavy snow with
significant reductions in visibility possible along area roads.
-thor


&&

.AVIATION...
05/00Z TAF Period

Periods of light to at times moderate snow will affect areas along
and southwest of a KGTF to KLWT line through much of the next 24
hours, with IFR/MVFR/low-VFR to potentially LIFR conditions
expected through the entire 0500/0600 TAF period at the KLWT,
KHLN, KBZN, and KEKS terminals. At this time the KBZN terminal
has around a 30% chance of seeing the aforementioned LIFR
conditions, especially from the evening hours tonight through
early morning hours on Friday. Across the remaining terminals of
KCTB, KHVR, and KGTF MVFR/low-VFR conditions will largely prevail
with precipitation remaining over the adjacent mountains.
Mountains will be obscured for the next 24 hours. - Moldan

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  22  37  21  33 /  20  40  80  50
CTB  15  30  10  25 /  10  40  90  30
HLN  24  37  29  40 /  40  50  90  60
BZN  23  36  26  39 / 100  60  90  60
WYS  15  30  19  33 /  90  90 100  80
DLN  23  39  27  40 /  50  50  70  20
HVR  18  29   9  22 /  20  40  90  60
LWT  21  34  19  33 /  60  40  90  70

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Friday afternoon through Sunday morning
for East Glacier Park Region-Southern Rocky Mountain Front.

Winter Storm Warning until 2 PM MST Saturday for Big Belt,
Bridger and Castle Mountains-Gallatin and Madison County
Mountains and Centennial Mountains-Little Belt and Highwood
Mountains.

Winter Weather Advisory until 11 AM MST Friday for Elkhorn and
Boulder Mountains-Gallatin Valley.

Winter Storm Warning until 5 PM MST Saturday for Northwest
Beaverhead County.

&&

$$
http://www.weather.gov/greatfalls