454
FXUS65 KTFX 300359
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
959 PM MDT Thu Oct 29 2026

Aviation Section Updated.

.KEY MESSAGES...

- Patchy dense fog continues this afternoon and is likely to
  expand in area tonight; potentially another round Friday night.

- Seasonable afternoon temperatures the next few days, with the
  potential for warmer afternoon temperatures by later next week.

- A good chance for widespread rain and snow Saturday night into
  Sunday over much of the region.

&&

.UPDATE...
/Issued 713 PM MDT Thu Oct 29 2026/

This evening into Friday morning there will be fog along and west
of the I-15 corridor between Cascade and the Canadian border. For
the update, minimum temperatures across North-central Montana were
decreased and the hourly temperatures were regenerated. Also the
fog coverage along and west of the I-15 corridor between Cascade
and the Canadian border was increased. The rest of the forecast is
on track. -IG

&&

.DISCUSSION...
/Issued 713 PM MDT Thu Oct 29 2026/

Today...

Areas of fog and low clouds persist across much of the north-
central MT plains, where a very moist low level airmass is in
place on the southwestern fridge of surface high pressure centered
across the Canadian Prairies. Light low level easterly upslope
flow is supporting some of the most widespread/dense fog affecting
areas adjacent to the Rocky Mountain Front and Cascade county. A
Dense Fog Advisory continues through 21z adjacent to the Rocky
Mtn Front.

Tonight through Friday night...

Surface high pressure currently centered across southern AB/SK
slowly slides eastward through Friday night and is likely to hold
the shallow/moist airmass in place across the the plains,
maintaining at least some areas of low clouds and fog across
portions of north-central MT. Dense fog advisories will likely be
needed again tonight through Friday morning for many of the same
locations experiencing fog today. Latest high resolution model
ensembles give a 60% probability for visibility 1/2 mile or less
for areas of north-central MT along and west of I-15.
Additionally, overnight temperatures near or slightly below
freezing will support freezing fog again tonight as well, and even
the potential for some patchy freezing drizzle with the risk for
localized icing, particularly affecting bridges and overpasses.

This weekend...
An upper level low over the Pacific Northwest will dig southeast
towards Utah into Saturday. This will result in a moist southerly
flow aloft to developing  over Central MT. As a result, rain/snow
is forecast to develop Saturday night over Southwest MT and then
move into Central MT by Sunday morning. Latest model guidance
continues to support widespread precipitation development Saturday
night into Sunday with precipitation exiting the area Sunday
night or Monday morning. This storm system will bring rain/snow
to much of the CWA. Snow levels will be high to start, generally
above 7000 feet on Saturday, but then are forecast to fall down to
about 4000 feet Monday. By Monday, most of the precipitation will
have exited the region, but mountain snowfall is likely Saturday
night into Sunday. Snow accumulations around the Pony/Big Sky area
are starting to approach warning criteria. Thus a winter storm
watch might be needed for Zone 330. Otherwise, a winter weather
advisory is looking likely for mountain areas of Southwest and
portions of Central MT from Saturday night into Sunday night.

As the next upper level ridge starts to build over the northern
Rockies. The main question is how strong will it be. Overall, we
expect drier and slightly warmer conditions by the later portions
of next week as this upper level expands. Afternoon temperatures
might be a bit warmer than currently forecast for the later half
of next week. Hoenisch/Brusda/WMR

&&

.AVIATION...
30/06Z TAF Period

VFR conditions will prevail at all terminals except for the KCTB,
KGTF, KLWT, and KHVR terminals during this TAF Period. Fog will
affect the KGTF and KCTB terminals through at least 30/17Z. This fog
will become dense after 30/09Z and reduce visibility to at least one
half mile through at least 30/16Z. Through at least 30/16Z there
will be LIFR-level ceilings at the KCTB and KGTF terminals with LIFR-
level cielings continuing through the end of the TAF Period at the
KCTB terminal. At the KHVR and KLWT terminals during a portion of
this TAF Period there will be at least IFR-level ceilings. Across
North-central Montana there will be periods of mountain
obscuration during the majority of this TAF Period. -IG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  28  39  30  52 /  10   0  10   0
CTB  25  36  26  50 /  30  10  10   0
HLN  28  45  31  50 /   0   0  20   0
BZN  27  48  30  48 /   0   0  10  30
WYS  23  52  26  45 /   0   0  50  70
DLN  30  50  33  48 /   0  10  20  30
HVR  27  46  26  50 /   0   0   0   0
LWT  25  47  29  53 /   0   0   0   0

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon MDT Friday for Cascade County
below 5000ft-Eastern Glacier, Western Toole, and Central Pondera-
Eastern Pondera and Eastern Teton-Gates of the Mountains-
Northern High Plains-Southern High Plains.

&&

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