Carter, Montana Weather Forecast Discussion

880
FXUS65 KTFX 022038
AFDTFX
Area Forecast Discussion
National Weather Service Great Falls MT
238 PM MDT Thu Oct 2 2025
.KEY MESSAGES...
- Scattered shower and thunderstorm activity increases today
  through Saturday.
- A Pacific weather system will bring accumulating mountain
  snow Saturday and Sunday with snow levels at least briefly
  falling down to the valleys and plains Sunday morning.
- The first widespread hard freeze expected by Monday morning
  and again Tuesday morning.
- Drier and milder conditions return early next week before more
  unsettled conditions redevelop heading towards next weekend.
&&
.DISCUSSION...
- Meteorological Overview:
An approaching Pacific trough will strengthen the southwesterly
flow aloft over the Northern Rockies over the next couple of days,
while passing shortwaves bring variable cloudiness and increased
shower and isolated thunderstorm activity. Localized heavy
downpours will be the primary hazard to monitor, particularly if
they occur over the more sensitive burn scars over central and
southwest MT. Otherwise, the thunderstorm threat will be limited
to localized gusty winds, small hail, and occasional lightning
impacting outdoor activities, mainly on Friday
By Saturday, the trough begins to split as it approaches from the
west while merging with a strengthening trough diving
southeastward out of BC/AB. This will be responsible for bringing
the coolest temperatures of the season so far and the much
anticipated mountain snow. Colder air aloft will infiltrate the
Northern Rocky Mountain Front by Saturday afternoon before quickly
spreading southward through the remainder of the forecast area
Saturday night into Sunday. H500/H700 temperatures on the order of
-20C/-5C will support snow levels falling to 4,000 to 5,000 ft
 level by Sunday morning and the heavier bursts of precipitation
 will encourage snow levels to at least briefly fall to the valley
 floors and plains. Lower elevations are also expected to undergo
 widespread freezing low temperatures, especially Sunday night
 and Monday morning when lows in the teens and 20s will be common
 across the forecast area, coldest over some of the wind protected
 central and southwest valleys.
Most ensembles favor some resemblance of ridging to move Monday
through Wednesday for moderating temperatures and generally dry
conditions, but the Northern Rockies look to sit on the eastern
periphery of this feature causing the area to be susceptible to
passing disturbances within a northwesterly flow aloft. Although
unsettled conditions are favored to return for the second half of
the week, forecast uncertainty erodes due to poor ensemble
agreement and run to run consistency. - RCG
- Forecast Confidence & Scenarios:
Increased shower and thunderstorm activity followed accumulating
mountain snow and lower elevation hard freeze this weekend...
The shower and thunderstorm activity over the next couple of days
will generally be low impact aside from the threat for heavier
downpours impacting area burn scars. The highest probabilities (40
to 60%) for rainfall exceeding a half inch or more will be
highest for central and southwestern locations west of I15 for the
24 hour period ending 6 pm Friday. This will shift southeastward
Friday night into Saturday, mostly impacting southwest locations
east of I15 and south of highway 12.
Then the focus shifts to the Pacific trough ejecting eastward and
bringing accumulating mountain snow the much of the Northern
Rockies. Snow will initialize along the Northern Rocky Mountain
Front and over the higher terrain of the southwest on Saturday
before snow levels fall to the 4,000 to 5,000 ft level Saturday
night into Sunday. This is when snowfall will be heaviest and most
widespread and expand to include all mountain areas. As mentioned
in previous sections, heavier bursts of precipitation and or
increasing cold air aloft may send snow levels down to the plains
and valley floors for a period, mainly Saturday night and early
Sunday.
Snowfall exceedance probabilities have gone up over the last 24
hours. Areas above 7,000 ft along the Northern Rocky Mountain
Front are looking at over a 70% chance for snow totals over 3
inches and around 50% for 6 inches or more. Lesser amounts are
expected for Marias Pass where there is only a 30% chance for
snowfall greater than 3 inches. In the southwest, the Gallatin and
Madison mountain ranges above 7,000 feet have a 50% chance for
snowfall above 6 inches. Other mountain areas should see amounts
generally in the 1 to 3 inch range and most lower elevations of
north-central and southwest MT will see little to no
accumulations.
Impacts will be greatest for those braving the outdoor wet, raw,
and cold conditions with an increased hypothermia risk for those
not properly dressed for the weather. Also, forest roads may
become muddy, slushy and even impassible. Given the increased
probabilities for totals exceeding 6 inches, isolated power
outages and tree damage can`t be ruled out, especially for the
trees that have retained there foliage. After collaboration with
neighboring offices winter storm watches were posted for the
Glacier National Park area and the higher terrain of the Madison
and Gallatin ranges in southwest MT fro Saturday night into
Sunday. Although the expected amounts are a bit lower than
warning/watch criteria, this is the first expected widespread
snowfall of the season and a high end one at that.
The other impact from this system will be the first widespread
hard freeze of the season for lower elevations. The southwest
valleys will be coldest where lows may dip into the teens and even
single numbers Sunday night and Monday morning. Most lower
elevations have over 60% for low temperatures below 28F Monday
morning and only a slightly less chance for the same hard freeze
criteria Monday night into Tuesday morning. - RCG
&&
.AVIATION...
02/18Z TAF Period
VFR conditions will prevail across all terminals during this TAF
Period outside of during any thunderstorms. At the KBZN and KEKS
terminals there is a 15 - 30% chance for thunderstorms between now
and 03/03Z. Any thunderstorm will produce a brief heavy downpour,
lightning, and gusty, erratic winds. At the KEKS and KBZN terminals
there is a 20 - 40% chance for rain showers during the duration of
this TAF Period. At the KGTF and KHLN terminals there is a 20 - 50%
chance for rain showers between 02/21Z and 03/11Z. At the KCTB
terminal from 03/00Z through the end of the TAF Period there is a 20
- 40% chance for rain showers. At the KHVR terminal there is a 20  -
50% chance for rain showers between 03/02Z and 03/12Z. At the KLWT
terminal there is a 20 - 40% chance for rain showers between now and
03/11Z. Across Southwestern Montana there will be periods of
mountain obscuration during this TAF Period. -IG
&&
.HYDROLOGY...
There will be increased shower and isolated thunderstorm activity
over the next couple of days, mostly over central and southwest
MT. While flooding is generally not expected, moisture levels will
be high enough to support rainfall rates up to or greater than a
quarter inch per hour. Flooding and or land slides over burn scars
can`t be ruled out should they undergo heavier downpours. - RCG
&&
.PRELIMINARY POINT TEMPS/POPS...
GTF  48  64  45  58 /  60  70  50  20
CTB  42  60  39  54 /  40  30  10  20
HLN  48  64  44  56 /  70  80  70  50
BZN  43  71  42  53 /  40  40  70  80
WYS  35  64  34  48 /  20  40  80 100
DLN  42  68  40  52 /  50  60  70  70
HVR  47  69  43  61 /  50  50  30  10
LWT  45  70  43  54 /  40  20  50  60
&&
.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late Saturday night through Sunday
morning for East Glacier Park Region.
Winter Storm Watch from Saturday evening through Sunday
afternoon for Gallatin and Madison County Mountains and
Centennial Mountains.
&&
$$
http://www.weather.gov/greatfalls

NWS TFX Office Area Forecast Discussion