126
FXUS65 KTFX 171751
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1151 AM MDT Fri Oct 17 2025

Aviation Section Updated.

.KEY MESSAGES...

 - A period of strong winds is expected from the end of the work
   week and through much of the weekend, with the strongest winds
   arriving on Sunday.

 - Temperatures for much of the next week will be near to above
   normal.

 - Two periods of mountain snow are expected, with the first
   occurring from today through tonight and the second
   opportunity coming Sunday morning through Monday morning.

&&

.UPDATE...
An approaching wave within a slightly northwesterly flow aloft
along with ridgetop stability resulted in mountain wave activity
earlier this morning across the Rocky Mountain Front and out to
Cut Bank. Mid-level flow near or in excess of 50kts was translated
to the surface as a result of this mountain wave activity. Mid-
level flow, and perhaps more importantly ridgetop stability has
decreased since, and will continue to do so as daytime heating
continues. A more widespread breezy wind look to develop as a
result for most of the plains later this morning into the
afternoon.

A cold front associated with the aforementioned wave shifts south
from Canada late this afternoon into the evening, which will
result in a period of rain/snow showers at lower elevations and
snow showers in the mountains. Surface temperatures appear
marginal for snow at lower elevations, hence when combined with
mild temperatures ahead of the front today (Warm roads), any snow
that does fall at lower elevations would struggle to accumulate
on roadways. Reduced visibility will be the main concern with snow
showers that do develop at lower elevations.

Elsewhere in the mountains the quick hitting nature of the snow
showers should limit accumulations. An instance or two of a quick
inch or so is reasonable, though anything more than that would be
quite localized. Hence, no Winter Weather Advisories are being
considered at this time. Precipitation moves out late tonight into
Saturday morning as brief upper level ridging builds in.

The forecast was updated to reflect latest trends as well as to
decrease snow levels to get a mention of a mix of rain/snow at
lower elevations a bit quicker for late afternoon and evening over
the plains. No significant changes otherwise. -AM

&&

.DISCUSSION...
/Issued 200 AM MDT Fri Oct 17 2025/

 - Meteorological Overview:

A rather progressive and unsettled pattern is expected across the
Northern Rockies for much of the next week, with several robust
shortwaves diving/sweeping southeast to east over the region and
bringing opportunities for gusty winds and predominately mountain
snow and lower elevation rain/snow mixes.

The first of these robust shortwaves will dive southeast and over
North Central through Southwest Montana from the morning hours today
through the evening hours tonight, with transient ridging quickly
building east from the Pacific Northwest from Saturday morning
through Saturday evening before the second and "strongest" shortwave
sweeps east and over the Northern Rockies from Sunday morning
through Monday morning. Mountain snow showers, rain/snow showers
across lower elevations, and gusty southwest to west surface winds
will accompany the first of the aforementioned shortwaves through the
day and overnight hours tonight; with the potential for some of the
snow shower over the mountains to produce significant reductions in
visibility. A brief lull between precipitation and the gustiest of
winds can then be expected on Saturday as upper level ridge moves
overhead, but this will be short-lived as surface winds begin to
increase from late Saturday afternoon/evening. Surface winds through
the day on Sunday will be stronger than that of today/tonight,
especially along the Rocky Mountain Front points east towards the I-
15 corridor where mountain wave activity and a strong pressure
gradient will support localized high wind speeds/gusts. As the
shortwave moves over the Northern Rockies on Sunday snow levels will
fall from northwest to southeast, with the potential for impactful
snow falling along the Continental Divide north of the Montana Hwy
200 corridor. Temperatures the timeframe will be near to above
normal across lower elevations thanks to the downsloping southwest
to west winds.

Beyond Monday a quasi-zonal pattern with embedded waves will help to
maintain periods of gusty surface winds, precipitation chances along
the Continental Divide, and near to above normal temperatures. -
Moldan

 - Forecast Confidence & Scenarios:

Snow showers through tonight...

NBM probabilities for snowfall accumulations of 1" or greater are in
excess of a 50% chance for the Continental Divide north of the
Montana Hwy 200 corridor, Little Belt Mountains, and portions of the
Gallatin and Madison Range in Southwest; with most of these
mountainous locations ranging between a 10-30% chance for 2" or more
of snow. Main impact from any snow shower through the day today and
early morning hours on Saturday will be reduced visibilities,
especially over short distances given the banded nature of the snow
showers parallel to the orientation of the upper level flow.


Strong to High Winds on Sunday...

Climate anomaly indicators such as the NAEFS and ECMWF EFIs continue
to support a window for strong, to localized high, winds on Sunday
across Southwest through North Central Montana. H700 cross barrier
flow of 40-50kts early Sunday morning over the Rocky Mountain Front
and immediate plains adjacent to the Rocky Mountain Front will
expand eastward and southward across the remainder of North Central
through Southwest Montana through the day. Between 12z Sunday and
00z Monday the H700 flow will peak at between 2-3 standard
deviations above normal, which combined with the passage of the
upper level shortwave supports a favorable window for peak momentum
transfer to the surface. Latest ECMWF EFIs also support at least a
climatologically unusual windy day on Sunday, with two main areas in
which values range from 0.6 to nearly 0.9. The first area exists
along and north of the Montana Hwy 200 corridor, with values peaking
from the Eastern Glacier Park Region eastward along the US Hwy 2
corridor towards Havre. The second area of noteworthy EFI values on
Sunday are focused along and south of the I-90 corridor in Southwest
Montana, with the highest values of either area being confined to
near the Madison River Valley and West Yellowstone Area.

BUFKIT soundings from the Rocky Mountain Front points eastward
towards Cut Bank support the potential for mountain wave activity
during the early to late morning hours on Sunday, with said sounding
profiles showing peak cross barrier flow near a layer of ridgetop
stability. Latest NBM probabilities for wind gusts in excess of 55
mph range from 45%, 55% and 70% along the US Hwy 2 corridor from
East Glacier, to Browning, to Cut Bank respectively, with a 10%,
20%, and 35% chance for gusts to exceed 65 mph at each location
respectively. At Cut Bank specifically the 35% chance for wind gusts
to exceed 65 mph is noteworthy as the 99th Percentile Maximum Wind
Gust for October is around 66 mph. NBM probabilities for
sustained winds of 40 mph or greater at Cut Bank are also relatively
high at a 65% chance, which given the potential enhanced wind
speeds/gusts due to mountain wave activity and then from daytime
mixing has given us the confidence to issue a High Wind Warning for
Eastern Glacier, Western Toole, and Central Pondera Counties from
10z Sunday through 02z Monday. Additionally, Eastern Toole and
Liberty Counties were added to the High Wind Watch given favorable
wind probabilities in lee of the Sweet Grass Hills due to the
potential for localized mountain wave activity.

For the Madison River Valley surface winds will mainly be out of the
south for much of the day on Sunday before veering to the southwest
later in the day, with the H700 flow being out of the west for the
entirety of day. This lack of unidirectional flow from the surface
through H700 within the Madison River Valley casts some doubts as to
whether high winds will materialize, and for that reason a High Wind
Watch has not been issued at this time. None-the-less latest NBM
probabilities do support a 20% chance for wind gusts in excess of 55
mph within the Madison River Valley and a 50% chance for sustained
winds of 40 mph around the Ennis Area.


Mountain Snow from Sunday morning through Monday morning...

Snow levels will fall through the day on Sunday, especially beyond
15z Sunday in a northwest to southeast fashion, as an upper level
shortwave and attendant Pacific cold front sweeps east across the
Northern Rockies. NBM probabilities for snowfall accumulations in
excess of 2" are highest along the Continental Divide north of the
Montana Hwy 200 corridor where the chance of exceeding said amount
generally ranges from a 40-80% through the timeframe. Furthermore
the probability of exceeding 4" or more of snow for these same areas
ranges from a 20-60% chance, with the highest probabilities over the
Glacier National Park Region. The combination of falling snow and
gusty west winds will need to be monitored as significant reductions
in visibility may materialize for areas like US Hwy 2 over Marias
Pass. - Moldan

&&

.AVIATION...
17/18Z TAF Period

Gusty winds will continue across the CWA until about 02z Sat,
before diminishing a bit. A Canadian cool front will move
southward through the CWA overnight. Lower elevation rain showers
and mountain snow showers are expected. Impacts from precip will
be brief, generally less than an hour at the terminals and a few
hours in the mountains. Most of the precipitation exits the CWA
by 12z Sat. Mountains/passes will be obscured at times across the
CWA. Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  61  30  56  46 /  10  60   0  20
CTB  55  27  54  41 /  60  50   0  20
HLN  60  31  56  38 /  20  40   0  10
BZN  59  29  53  36 /  10  50   0   0
WYS  45  21  45  25 /  10  40   0   0
DLN  59  26  54  35 /   0  10   0   0
HVR  58  28  56  37 /  30  50   0  10
LWT  58  28  51  35 /  10  60  10  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

High Wind Watch from late Saturday night through Sunday evening
for Eastern Glacier, Western Toole, and Central Pondera-Eastern
Toole and Liberty.

&&

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