926
FXUS65 KTFX 131720
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1120 AM MDT Mon Oct 13 2025

Aviation Section Updated.

.KEY MESSAGES...

- Snow over central and north-central Montana diminishes later
  this morning, although lighter snow may persist through Tuesday
  morning along the divide.

- Temperatures slowly warm to near average by the end of the
  week,but there will be day to day opportunities for scattered
  shower activity and mostly mountain snow, especially Wednesday
  through Friday.

- Periods of breezy to windy conditions are expected heading into
  the weekend.

&&

.UPDATE...
/Issued 921 AM MDT Mon Oct 13 2025/

Morning update has been published, with the main adjustment coming
in the form on winter weather highlights. All of the Winter Storm
Warnings have been cancelled or downgraded, with the Southern
Rocky Mountain Front and Southern High Plains being downgraded to
a Winter Weather Advisory which was then subsequently extended
until 6PM MDT this evening. Here additional snow accumulations of
up to 2 inches are expected thanks to low-level northeast upslope
flow, with localized amounts possibly approaching 4 inches.
Elsewhere the Winter Storm Warning for the Gates of the Mountains
was downgraded to a Winter Weather Advisory as light snow was on-
going here; however, no adjustment was made to the endtime as the
bulk of the impactful snow is expected to end near noon MDT.
Finally the Winter Weather Advisories that were in effect for
portions of North Central and Central Montana were cancelled
outside of the Upper Blackfoot and MacDonald Pass Area and Cascade
County below 5000 ft as additional snowfall accumulations of up
to 1" are possible through noon MDT here. Otherwise the only other
adjustment to the on-going forecast was to cool temperatures by 2
to 4 degrees as persistent cold air advection and mid- to upper
level cloudiness will inhibit any significant solar insolation
throughout the day today, especially across Central and North
Central Montana where snow has recently fallen over the past 24
hours. - Moldan

&&

.DISCUSSION...
/Issued 921 AM MDT Mon Oct 13 2025/

 - Meteorological Overview:

Cold northeasterly upslope flow will persist over central and
north- central MT for much of today while warmer air and moisture
overrun the shallow colder air via H500 southwesterly flow. This
will maintain cold and damp conditions for the northern half of
the forecast area today. Snowfall and wintry impacts will peak
this morning before diminishing and retreating to areas along the
Rocky Mountain Front later this afternoon into tonight.

A closed low diving southward along the Pacific Northwest coast
will continue to support difluent flow over the Northern Rockies
for the first half the week. Moisture and weak shortwaves moving
in from the southwest will bring periods of rain showers and
higher mountain snow tonight into Tuesday, mostly for southwest
MT. The cold air over central and north-central MT will slowly
retreat northward heading into mid- week.

The Pacific Northwest closed mid- level low is expected to peak
in intensity over central CA before weakening and swinging
northeastward through the Great Basin and eventually reaching
eastern MT by around Thursday. The evolution of this feature will
be complex as it approaches the region, so the precise locations
of its low pressure center(s) and resultant precipitation
locations is still a bit on the fuzzy side. Overall expect the
most widespread rain and mountain snow to occur between Tuesday
night and Friday. With milder Pacific air moving in, snow impacts
look to be on the minor side and mostly confined to mountain
areas.

Ridging aloft with stronger westerly flow looks to at least
briefly move through the Northern Rockies heading towards the
weekend followed by more passing troughs in an increasingly
northwesterly flow aloft. This will result in periods of breezy to
windy conditions, though the timing details still need to be
worked out depending trough and ridge phasing. - RCG

 - Forecast Confidence & Scenarios:

Snow today through Tuesday morning...

Warm air aloft overrunning cold northeasterly flow in the low
levels continues to bring snow this morning for central and north-
central locations along the divide and near the central island
ranges. The focus of the heaviest snow initially set up in the
Boulder and Helena areas, a little farther south than originally
expected. The Helena Airport set a 24 hour snowfall record
yesterday with 2.6 inches. The main area of snow has since lifted
northward toward the Southern Rocky Mountain Front/central island
ranges and their adjacent plains. Although snowfall has generally
fallen below expectation for the winter storm warned area, I will
leave the warning posted for a bit longer with a general 1 to 4
inches of snow still expected through the morning hours. Slippery
roads and power outages from heavy, wet snow will continue to be
the primary impacts. Snow gradually diminishes later this morning
into the afternoon, though light snow may persist along the Rocky
Mountain Front through Tuesday morning. - RCG

&&

.AVIATION...
13/18Z TAF Period

VFR conditions will prevail at the KWYS terminal during the duration
of this TAF Period. At all terminals except for the KWYS terminal,
at least MVFR-level ceilings will linger until at least 14/12Z.
At the KLWT and KGTF terminal snow will linger for at least the
first two hours of this TAF Period. At the KCTB terminal snow will
at least intermittently affect the terminal between now and
14/00Z. At the KCTB terminal between 14/00Z and 14/06Z there is a
30% chance for snow. At all but the KCTB and KHVR terminals there
is at least a 20% chance for rain or a rain/snow mix from 14/12Z
through the end of the TAF Period. There will be mountain
obscuration during the majority of this TAF Period. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  33  24  40  28 /  80  20  20  30
CTB  30  23  40  21 /  70  30  10  10
HLN  34  25  41  29 /  90  20  40  50
BZN  41  24  48  30 /  10  10  30  60
WYS  46  23  50  27 /  10  40  60  80
DLN  43  25  48  33 /  10  30  40  50
HVR  39  21  48  29 /  40  10  10  30
LWT  35  23  46  29 /  30  20  20  60

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM MDT this evening for Southern
High Plains-Southern Rocky Mountain Front.

Winter Weather Advisory until noon MDT today for Cascade County
below 5000ft-Gates of the Mountains-Upper Blackfoot and
MacDonald Pass.

&&

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