Helena Valley, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

821
FXUS65 KTFX 151505
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
905 AM MDT Wed Oct 15 2025

.KEY MESSAGES...

- A Pacific weather system will bring periods of rain showers
  and mountain snow today and Thursday, mostly over central and
  southwest Montana today.

- Periods of breezy to windy conditions, a few showers, and
  mild temperatures are generally expected heading into the
  weekend.

- More periods of showers, mountain snow, and breezy to windy
  conditions continue into next week.

&&

.UPDATE...

Elongated upper troughing across much of the west continues to
shift east/northeast today into tonight. The best forcing/support
for precipitation mainly looks to be east of I-15 through today
into tomorrow as the system continues to nudge away from the
region. Snow levels look to fall on the back side of this system
heading into tonight, mainly impacting the mountains east of I-15
across SW MT. Snow levels look to briefly fall to around 6,000 to
6,500 ft tonight into Thursday across the aforementioned terrain.
Given forecast amounts at and below pass level that are rather
low at the moment, we will continue to hold off on a Winter
Weather Advisory. Those planning to recreate in the
Madisons/Gallatins and adjacent ranges into Thursday should plan
for cold/raw conditions.

Ongoing low clouds will result in foggy passes through at least
the remainder of the morning, mostly across Southwest and Central
MT.

Partial clearing this afternoon near the ID border between Monida
Pass and West Yellowstone looks to result in at least a brief
opportunity for a rumble of thunder this afternoon.

Minor tweaks were made to the forecast to account for
latest trends. Overall changes were minor. -AM

&&

.DISCUSSION...
/Issued 536 AM MDT Wed Oct 15 2025/

 - Meteorological Overview:

An elongated mid-level trough is now approaching the Northern
Rockies from the west/southwest while local observations log
another morning with low stratus, patchy fog, and scattered areas
of light rain/snow. A closed low over the Great Basin is still
expected to trek northeastward into eastern MT by Thursday
evening. This will bring the most widespread period of lower
elevation rain and mountain snow tonight into Thursday.

Although some cooling aloft will occur on the backside of this
system, H700 temperatures should stay in the -2 to -5C range and
keep snow impacts on the minor side and mostly confined to the
central and southwest mountains. Most of the precipitation is
still expected to fall east of a Dillon to Havre line and the
primary area of concern continues to be be snow in the Madison and
Gallatin mountain ranges.

A fast moving trough then quickly dives southeastward out of
BC/AB and brings breezy to windy conditions and a few showers to
the Rocky Mountain Front and the plains Thursday night into Friday
before transient ridging dries things and warms temperatures
above average Saturday into Sunday. A progressive pattern looks to
continue into early next week with another trough moving into the
region later Sunday into Monday for more winds, showers, and
mountain snow. - RCG

 - Forecast Confidence & Scenarios:

Rain, snow and winds through the weekend...

Precipitation associated with the incoming trough is still
expected to favor areas of east of a Dillon to Havre line.
Probabilities have not changed much over the last 24 hours with a
20 to 50% chance for rainfall/liquid equivalent precipitation
amounts exceeding a half inch for the 48 hour period ending Friday
at 6 am, highest over mountain areas. Snowfall probabilistic
guidance continues to keep the best chances for accumulating snow
over the Madison and Gallatin ranges above 6,000 ft where there is
still around a 50 to 70% chance for snow totals over 3 inches for
the same 48 hour period ending at 6 am Friday. The peak of the
snowfall looks to occur late tonight into Thursday and will
primarily impact those recreating in the back country above pass
level.

The trough that moves in from the northwest Thursday night and
Friday will generally be a provider of gusty winds, though there
will be some passing widely scattered showers and light mountain
snow as well. The plains will see wind gusts over 40 mph at times
and gusts over 50 mph can be expected along the Rocky Mountain
Front. This fast moving system will offer little in the way of
cooling, but will rather serve to hold temperatures in check for a
day or so.

After transient ridging brings a brief period of temperatures
warming above average and dry conditions Saturday through early
Sunday, another trough moves in sometime Sunday into early next
week. The timing ultimately depends on whether the system
undergoes any shearing/splitting processes that would slow it`s
arrival. The faster solutions bring it in as early as Sunday
morning. More winds, showers, and mountain snow can be expected
when upon its arrival while temperature mostly trend near average.
- RCG

&&

.AVIATION...
15/12Z TAF Period

An approaching Pacific trough and excessive low level moisture
will maintain periods of rain/snow, patchy fog, and low stratus
for much of the period. While all areas will initially be impacted
by MVFR/IFR/LIFR conditions, the focus of the most degraded
flight categories will generally shift to areas along and east of
KDLN to KHVR line after 15/20Z. - RCG

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  46  33  54  37 /  40  30  40  10
CTB  49  27  58  36 /   0   0  10   0
HLN  48  33  53  35 /  40  40  40  10
BZN  49  33  48  29 /  60  50  60  20
WYS  50  28  43  23 /  80  70  80  50
DLN  48  32  51  29 /  50  30  20  10
HVR  48  33  54  34 /  70  50  40  20
LWT  47  32  46  33 /  70  50  70  30

&&

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

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