466
FXUS65 KTFX 160539
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1139 PM MDT Wed Oct 15 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Mountain snow across portions of Southwest Montana along with a
   bit more widespread lower elevation rain tonight into
   Thursday.

 - Trending milder toward the end of the week into the weekend,
   with a few showers around and breezy periods at times.

&&

.UPDATE...
/Issued 843 PM MDT Wed Oct 15 2025/

An elongated upper level wave will bring mountain snow and lower
elevation rain tonight through Thursday for places mainly east of
the Grant to Havre line. Though, most of the precipitation will
be concentrated over Southwest MT. Marginal low temperatures
Thursday morning and snow initially melting from warmer pavements
for mountain passes along and near the Madison and Gallatin
ranges will keep snow accumulations low (up to 1-2"). Most of the
impacts will remain above pass level, so a Winter Weather Advisory
is not needed at this moment. Forecast soundings show good low
level moisture and lighter winds to develop patchy fog across the
region overnight. -Wilson

&&

.DISCUSSION...
/Issued 843 PM MDT Wed Oct 15 2025/

 - Meteorological Overview:

Broad, elongated troughing across the interior west will continue to
nudge eastward through the remainder of the day and overnight. An
embedded, more potent wave is lifting northeastward within this
troughing, moving across WY and into Eastern MT during the day
Thursday. Although the majority of the upper level support for
precipitation will miss the region to the east, eastern areas will
still see a round of precipitation into the day Thursday. As slightly
cooler air works in tonight, snow levels look to fall to around
6,000-6,500 ft, and perhaps a bit lower at times. Most mountain
snow looks to be light, though the Madison and Gallatin ranges and
vicinity do look to see at least a couple inches of accumulation
above pass level. Given the lack of forecast impacts at pass
level, no Winter Weather Advisories are being considered at this
time. Mainly light rain is forecast at times at lower elevations
into Thursday with this system, largely in eastern areas.

A northwesterly flow develops in wake of the departing troughing
heading into Thursday night. A wave diving southeastward from BC
within the developing NW flow aloft will pass across the region
Friday night into Saturday. Initial impacts from this system will be
for a period of breezy winds, mostly over the plains Friday. As the
main portions of the wave moves overhead Friday evening and into
early Saturday, a quick period of precipitation develops. Snow in
the mountains with this system looks to be brief, hence the
window for accumulations looks to be rather narrow. The chance for
2 inches new snow peaks around 60% along the Rocky Mountain Front.

Upper level ridging briefly builds in for Saturday into early Sunday
before another upper level trough begins to approach from the west.
Before precipitation arrives with this system another period of
breezy winds looks to develop, again most favored over the plains.
The downslope nature of the winds looks to limit precipitation over
the plains with this system late Sunday into Monday, with areas
along the Continental Divide and across Southwest Montana most
favored for precipitation.

A rather progressive pattern continues after Monday. Cluster
guidance does not lend much confidence in specifics, as there is
roughly a 50/50 split between ridging and troughing toward the
middle of next week. -AM

 - Forecast Confidence & Scenarios:


Snow tonight into Thursday in the Madisons, Gallatins and vicinity:

Overall the chance for more than 3 inches of snow is only greater
than 50% at the highest peaks. At lower elevations the chance is
much lower, only around 10% or so in Big Sky. Hence, given the lack
of confidence in any meaningful impacts at this point, no Winter
Weather Advisories are being considered at this time. Regardless,
those planning to recreate in the mountains in these areas should
be prepared for cold/raw conditions.


Wind:

Two periods of gusty winds are favored. The first looks to be
Thursday night into Friday. The chance for a 58 mph gust between Cut
Bank and Browning is between 10 and 20% for this timeframe.

For the second period of wind late weekend the chance for a 58 mph
gust is higher, closer to 40% over the aforementioned area.


Mountain Snow Sunday into Monday:

Confidence in accumulating mountain snow is greatest along the
Continental Divide and across Southwest Montana over this
timeframe. Most terrain in these areas has a 50% chance or
greater for 3 inches of snow with this event. Elsewhere across
much of Central MT terrain and over the island ranges on the
plains the chance for 3 inches snow is much lower, mostly less
than 20%. -AM

&&

.AVIATION...
16/06Z TAF Period

The precipitation off to the east will continue to fill in west
through the morning, affecting Southwest MT and the KLWT area.
There is a little uncertainty in precipitation timing since
recent model runs trend this precipitation band a little drier.
Patchy fog will remain a concern tonight, which will bring brief
IFR/LIFR conditions if it does develop. Clouds will slowly clear
throughout Thursday as this weather system exits. West winds
start to pick up along KCTB Thursday evening. -Wilson

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  33  54  37  57 /  20  20   0  20
CTB  29  58  36  53 /   0   0   0  40
HLN  34  53  35  58 /  20  20   0  20
BZN  33  48  29  57 /  40  60  10  10
WYS  28  43  23  45 /  50  60  30  10
DLN  32  51  29  56 /  50  20   0   0
HVR  33  54  34  55 /  30  20   0  20
LWT  32  46  33  53 /  40  60  20  20

&&

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

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