Helena Valley, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

176
FXUS65 KTFX 200539
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1039 PM MST Fri Dec 19 2025

Aviation Section Updated.

.KEY MESSAGES...

- Rain/snow/wintry mix showers continue across Southwest MT this
  afternoon, with an isolated snow squall possible along the
  frontal passage up on mountain passes.

- Gusty winds decreases from north to south through the rest of
  the day.

- Minor snow lingers along the Northern Continental Divide Saturday.

- Daily chances for mountain snow with slight chances for rain/snow
  at lower elevations continue next week.

&&

.UPDATE...
/Issued 826 PM MST Fri Dec 19 2025/

Slight adjustments were made to the winds based on trending obs
and updated model guidance but otherwise no major changes were
made to the going forecast.

The cold front that was previously across southwest Montana has
now pushed into northern Idaho/Wyoming. Lingering snow showers are
expected to continue over the next couple hours along the southern
Madison and Gallatin ranges including West Yellowstone but
otherwise the rest of southwest Montana will remain dry through
the rest of the night.

The main concern will be the potential for light to moderate snow
along the Northern Rockies including Marias Pass. For now the
current Winter Weather Advisory remains sufficient as impacts at
and below pass level are not expected to exceed warning criteria.
The previous forecast of 3 to 6 inches at Marias Pass remains on
track with the primary concerns through tomorrow afternoon being
slick roads and periods of low visibility along the US-2.
-thor

&&

.DISCUSSION...
/Issued 826 PM MST Fri Dec 19 2025/

 - Meteorological Overview:

The front continuing to move south through Southwest MT this
afternoon will bring minor mountain snow with lower elevation
snow/wintry mix showers. Warmer surfaces temperatures at lower
elevations will make any snowfall struggle to accumulate, but
can`t rule out an inch of accumulations from a moderate snow
shower. Snow squall chances look to be on the low end, but can`t
rule out one or two over the mountain passes. Farther north, a
Canadian Front will continue to bring in colder temperatures,
with the MT/Canadian border already dropped into the single digits
this afternoon. Gusty winds continue along the MT Highway 200
corridor this afternoon, but once that colder arctic air works in
the winds will begin to decrease.

Westerly flow aloft will keep streaming in moisture and orographic
lift for minor snow along the Northern Continental Divide/Eastern
Glacier Park region from tonight through the day Saturday.
Though, the rest of the region will likely get downsloped and
remain dry for Saturday.

On Sunday, a better upper-level wave coming through will bring
better chances for light mountain snow and lower elevation rain/snow
through Monday for mainly the Rocky Mountain Front and Southwest
MT.

The pattern shifts to more southwest flow aloft, keeping above
average temperatures across the region through mid next week.
Daily chances for lighter mountain snow and lower elevation
rain/snow continues next week.

 - Forecast Confidence & Scenarios:

Winds for the rest of today:

Winds generally have down trended sooner than forecasted across
the North-Central MT plains through the I-90 corridor. This has
led to the early cancellation of the High Wind Warnings there. Hi-
res guidance showed a lingering mid level jet max continuing to
mix down strong winds along the MT Highway 200 corridor through
the afternoon hours, so I left those High Wind Warnings in effect
until the evening. With the front moving through the Southwest,
there`s still a good chance for some strong winds to mix down to
the surface through the rest of the afternoon as well.

Mountain Snow Through Saturday:

Nothing has changed too much with the existing winter weather
advisories across Southwest MT. The front will continue to bring
moderate snow/snow showers, which will still bring additional
minor snow accumulations of 2-4" at pass level through tonight.

For the Northern Continental Divide/Eastern Glacier Park area,
snow as lightened up this afternoon. Therefore, I cancelled the
Winter Weather Advisory early. Incoming moisture and vorticity
maximums aloft passing through the area starting tonight will
bring another round of snow showers. There is a 70% chance for 4"
of snow along Marias Pass through Saturday afternoon. Minor snow
accumulations expected at pass level has prompted another issuance
of a Winter Weather Advisory for tonight through tomorrow
afternoon. -Wilson

&&

.AVIATION...
20/06Z TAF Period

VFR conditions will prevail through the period. Breezy west to
southwest winds will return across most terminals late Saturday
morning through the afternoon. -thor

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  28  40  26  42 /   0   0   0   0
CTB  19  35  23  37 /  10   0   0   0
HLN  24  38  21  39 /  10  10   0  10
BZN  18  37  18  40 /  40   0   0  20
WYS   8  27  14  36 /  90  10  20  90
DLN  18  34  19  39 /  30   0   0  20
HVR   5  30  19  36 /  10   0   0   0
LWT  22  36  24  41 /   0   0   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 5 PM MST Saturday for East Glacier
Park Region-Southern Rocky Mountain Front.

&&

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