571
FXUS65 KTFX 240248
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
748 PM MST Sun Nov 23 2025

.KEY MESSAGES...

 - Wintry weather moves into the area overnight tonight and
   tomorrow morning, bringing widespread snow and localized
   freezing rain to the Hi-Line.

 - Drier for midweek, but still a few snow showers around with
   temperatures near to below normal.

 - Another round of snowy weather looks likely next weekend, with
   the coldest air of the season likely pushing in behind the
   snowfall.

&&

.UPDATE...
Updated forecast is out for this evening. Main adjustment was just
to the timing of the current winter statement. The latest NAM has
the precipitation beginning closer to 6 AM in the Havre/Harlem
areas, along with the precipitation going into Monday evening in
this area. Thus just some adjustments to the start/end time for
this area. Otherwise, the overall forecast is on track.

Overall, there hasn`t been much precipitation on radar over the
entire Pacific Northwest until the past hour. The storm is just
starting to develop, with precip developing quickly now over
eastern Washington/eastern Oregon. This area of precipitation will
move east of the divide after Midnight and then into the
Havre/Harlem areas on Monday morning.

Colder air is already moving south of the border, with
temperatures in the 20s around Shelby. With warmer air aloft, some
of the precip will fall in the form of rain and freeze on contact
after Midnight in the Cut Bank/Shelby/Sweet Grass area. This
includes portions of I-15 in this area. Colder air will move in
during the day on Monday, changing the rain to snow.

For areas further south, in the Great Falls/ Helena/ Bozeman
areas, the precipitation is also likely to start out as rain, but
then change to snow as well. However, since temperatures are still
in the 40s, combined with a warm ground, the chance for freezing
precipitation is lower in these areas at this time.

Overall, this is the first of several weather disturbances this
week, with each disturbance bringing in colder and colder air. By
next weekend, the GFS model has air temperatures ranging from 10
below to 20 below across portions of North Central MT. At this
time, the GFS is one of the colder models, but this probability
is possible should we develop a good snow cover this week and get
some clearing skies overnight next weekend. Brusda

&&

.DISCUSSION...
/Issued 451 PM MST Sun Nov 23 2025/

 - Meteorological Overview:

Upper level ridging currently over the area today will break down
overnight tonight and tomorrow as a shortwave approaching the
Northwestern US begins to influence the area. For tonight, that
will generally mean increasing cloudiness, though for the
Continental Divide and the Hi-Line, the impacts will begin to be
felt overnight as snow begins in the higher terrain and some rain
or even freezing rain begins to fall along the Hi-Line overnight
tonight. Precipitation will begin to spread southward and eastward
quickly tomorrow morning as colder air surges into the area, with
a period of rain for lower elevations quickly changing over to
snowfall as temperatures fall. For most lower elevations, snowfall
will struggle to accumulate on roads and sidewalks, but in the
higher terrain colder temperatures overnight tonight and higher
snowfall rates will allow for some accumulations, with some of the
highest passes like Kings Hill Pass on track to see at least 6
inches of snowfall through tomorrow afternoon and evening.

High pressure will build into the area on Tuesday behind this
system, bringing a bout of cooler, but closer to normal
temperatures for the midweek, though northerly winds may allow for
some scattered snow showers, especially along the Rocky Mountain
Front and on the north slopes of the Little Belt and Snowy
Mountains (Great Falls to Lewistown Corridor). More widespread
light snowfall is possible on Thanksgiving Day as an elevated warm
front lifts through, though accumulations on Thursday should be
light.

Snowfall may increase in intensity overnight Thursday as another
surge of cold air starts to push into the area, clashing with the
warm air aloft trying to work into the area. While uncertainty
remains with the snowfall with this system, one thing that
continues to be clear is that there is an increasing likelihood of
the first arctic air mass of the season pushing into the area
over the weekend, with widespread subzero temperatures continuing to
be a substantial possibility (>40% for most areas by early next
week). -Ludwig

 - Forecast Confidence & Scenarios:

Accumulating Snow and isolated freezing rain tonight through Monday
evening...

Winter Weather Advisories remain in effect for the Southern Rocky
Mountain Front, Big Belt, Bridger and Castle Mountains, Little Belt
and Highwood Mountains, Bears Paw Mountains and Southern Blaine
County where probabilities for 4" or more of snow range from a 50-
75%. While initially warm ground temperatures will lead to some
melting across these locations snowfall rates of 1/2" per hour or
more during the daylight hours, which have a 30-60% chance of
occurring, will lead to snow accumulating even on warm surfaces.

The Winter Weather Advisory for the East Glacier Park Region remains
in effect; however, there is growing concern that the combination of
heavy snow and strong winds could significantly reduce visibilities
west of East Glacier and over Marias Pass. Additionally,
probabilities for 8" or more of snow over Marias Pass are now at a
65% chance, with even a 25% chance of 12" or more of snow. Future
shifts may need to consider upgrading the advisory to a warning, but
for now we will hold onto the advisory to see if the trend for
higher snowfall amounts holds.

In addition to the snowfall, confidence is increasing in at least
some isolated to scattered freezing rain along the Montana Hi Line
east of Cut Bank, including I-15 near the Canadian border. Road
temperatures remain around 50 degrees as of 3PM today, but are
likely to get very close to, if not just below, freezing overnight
as some rain manages to fall. While most areas should see roads stay
just above freezing, any bridges and overpasses seem likely to see
some ice accretion overnight tonight and early tomorrow morning,
which has prompted the issuance of an additional Winter Weather
Advisory for these areas. - Moldan/Ludwig

Late Week System

Models continue to suggest that late next week could be on the
snowy and cold side as a big pattern change continues to come into
increase in likelihood. Current NBM probabilities have continued
to slowly adjust upward for a few inches of snow late next week
for just about the entire state, with most of the area along and
north of a Helena to White Sulphur Springs line having a 50%
chance for at least 2-4 inches of snow Friday through Saturday.
Behind this snow, temperatures look to plunge into the deep
freeze, with around a 40% or higher chance of subzero temperatures
area wide by early next week. With much uncertainty remaining on
what could be an impactful period, be sure to monitor later
forecasts as details become clearer. Ludwig

&&

.AVIATION...
24/00Z TAF Period

Generally quiet conditions will prevail over the CWA this evening.
Then expect increasing chances for rain/snow to develop after 07z
Mon, with scattered areas of precip continuing through Monday
afternoon. Colder air will move into the CWA during the morning
hours, thus the rain will change to snow. Some freezing rain is
possible along the Highway 2 corridor between Browning and Harlem.
Mountains/passes will be obscured at times across the CWA
throughout the day on Monday. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  39  47  21  38 /  30  80  60   0
CTB  31  39  13  33 /  30  80  30   0
HLN  34  42  19  36 /  30  70  40   0
BZN  32  45  14  35 /  20  80  20   0
WYS  24  35   6  28 /  10  90  30   0
DLN  32  45  12  35 /  10  40   0   0
HVR  29  43  16  35 /  10  90  70   0
LWT  34  47  16  34 /  20  70  50   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 11 PM this evening to 11 PM MST
Monday for Big Belt, Bridger and Castle Mountains-East Glacier
Park Region-Little Belt and Highwood Mountains-Southern Rocky
Mountain Front.

Winter Weather Advisory from 6 AM to 11 PM MST Monday for Bears
Paw Mountains and Southern Blaine-Hill County-Northern Blaine
County.

Winter Weather Advisory from midnight tonight to noon MST Monday
for Eastern Glacier, Western Toole, and Central Pondera-Eastern
Toole and Liberty.

&&

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