888
FXUS65 KTFX 182148
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
248 PM MST Tue Nov 18 2025

.KEY MESSAGES...

 - Periods of light mountain snow will continue through Wednesday.

 - A fast moving weather system will bring breezy conditions and
   periods of mountain snow this weekend.

 - Cooler and wetter weather is expected next week leading up to
   Thanksgiving.

&&

.DISCUSSION...

 - Meteorological Overview:

A moist, but weak, southwesterly flow aloft persists until
Wednesday when a Pacific trough passes through the Northern
Rockies. This will maintain variably cloudy skies and spotty areas
of light precipitation. Snow levels will be lowest on Wednesday
while the trough axis moves overhead; however, negligible
precipitation amounts and the lack of colder air aloft will offer
little support for accumulating snow. Overnight and morning low
stratus and patchy fog will continue to be a concern through
Wednesday morning, especially near the Hi-Line; however, abundant
mid- and high level clouds should limit the overall coverage and
impact from dense fog.

Weak ridging aloft will bring dry and mild conditions for the
second half of the work week while the northern jet stream stays
in Canada and a closed low slides down the California coast. The
upper level jet moves southward into the Northern Rockies this
weekend and brings periods breezy to windy conditions, cooler
temperatures, and some mountain snow. A northwesterly flow aloft
develops and sends a series of colder troughs through the state
heading into the Thanksgiving holiday. This looks to bring periods
of mostly light snow and the coldest temperatures of the season so
far. -RCG


 - Forecast Confidence & Scenarios:

Fog Tonight:

There is around a 20% chance for fog development along the Hi-Line
and valleys of southwestern Montana overnight. The limiting factor
in confidence is the timing of the low stratus deck expected to
push through. If skies are unable to clear out and the stratus
deck moves in first then fog will not be an issue. Otherwise,
there could be some patchy dense fog in locations that clear out
tonight.


Mountain Snow and Lower Elevation Rain Tonight/Wednesday:

Light mountain snow is expected to linger around through Wednesday
afternoon. Snow amounts from here on out are not expected to
amount to much at pass level and below with only the peaks
potentially seeing up to a couple additional inches of snow. For
lower elevation rain, accumulation is generally expected to be
minimal with southwest Montana having the highest chance for
seeing light rain.


Wind and Snow This Weekend:

Snow amounts along the Northern Rockies have decreased from the
previous model runs which is not to say that locally higher
amounts are not possible but rather confidence is decreasing in
these occurring. The latest model guidance has a 10-30% chance of
the Northern Rockies exceeding 2 inches and a 10% chance of
exceeding 4 inches at the peaks. As of now there low confidence in
significant impacts to Marias Pass with the most likely scenario
being less than an inch at pass level and below.

When it comes to wind gusts in excess of 55 mph, there is a
greater than 80% probability along the Rocky Mountain Front
dropping off to a 50% chance around Cut Bank. The probabilities
on Saturday are slightly lower with a 60-80% chance along the
immediate Rocky Mountain Front decreasing to 50% chance around Cut
Bank. Overall the two days are expected to be fairly windy but
there are currently no indications or confidence in reaching high
wind criteria at this time.


Wind, Cold, and Snow Thanksgiving Week:

There are still high levels of uncertainty regarding the week of
Thanksgiving. The highest confidence lies in that there will be a
trough that moves over the western CONUS next week. Everything
else from the snow amounts to the cold temperatures keeps changing
enough with each model update that it is difficult to pin down
any specifics at this time. The latest run of the models ran a
little drier and colder than the previous runs. Notably the GFS
wants to run a little colder than the Euro which could impact not
only how much snow the lower elevations receive but how cold it
gets in the wake of the front.

One of the additional items to watch will be the wind,
particularly at the start of the event on Monday/Tuesday. The GFS
continues to increase upper level winds Monday afternoon into
Tuesday morning across north-central Montana. Right now the NBM is
erring on the side of caution and maintaining lighter winds in the
forecast but this will be something to watch in the coming days as
it is possible there could be impactful wind ahead of the cold
temperatures moving in.   -thor


&&

.AVIATION...

18/18Z TAF Period

The initial concern this TAF period will be for some lingering low
clouds/fog over the plains through early afternoon. Otherwise the
concern today will be for isolated pockets of precipitation,
mainly over the mountains.

Heading into late tonight, a cold front drops south from Canada,
resulting in a wind shift to a more northerly direction with at
least brief instances of low clouds at most terminals Wednesday
morning. A few instances of rain or snow showers will move in ahead
of and with the front Wednesday morning, but was too low confidence
to warrant mention in any TAFs at this time. Mountains looked to
be obscured at times near and behind the front. -AM

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  30  44  25  53 /   0  10   0   0
CTB  30  44  20  50 /  10  10   0   0
HLN  32  44  26  49 /  20  30   0   0
BZN  31  46  25  49 /  20  20   0   0
WYS  26  43  23  45 /  10  30  10  10
DLN  30  48  27  48 /  10  10   0   0
HVR  28  43  19  45 /  10  10   0   0
LWT  27  42  24  53 /  10  10   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

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