343
FXUS65 KBYZ 051700
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
1000 AM MST Fri Dec 5 2025

.KEY MESSAGES...

- Periods of moderate to heavy snow in the Beartooth-Absaroka and
  Crazy Mountains through the weekend. Heaviest snow on west to
  northwest aspects.

- Generally windy along the western foothills through the weekend,
  with gusts of 30 to 50 mph.

- A couple waves of light snow in the east, from Miles City to
  Baker and Ekalaka, could cause travel difficulties. Highest
  chances of snow are late tonight and Saturday morning, then late
  Saturday night and early Sunday.

- High confidence for a period of strong winds along the western
  foothills Monday night and Tuesday. This will coincide with much
  above normal temperatures through the first half of next week.

&&

.UPDATE...

Updated forecast for latest precipitation and wind gust model
trends this morning. Also extended the Winter Weather Advisory
for the Bighorn mountains into Saturday afternoon and added the NE
Bighorn mountains to the advisory.

Strong Pacific jet stream cuts across the area later today and
sags south through tomorrow. This will drag cooler Canadian air
into the area from the northeast which will then be over-run by
elevated the elevated warm/moist Pacific airmass. The result will
be a rollercoaster of temperatures, gusty winds at times
(especially western foothills and mountains), as well as periods
of precipitation over the next 48 hours.

Currently a stalled out front is located from near Miles City
southeast toward Alzada. Have been getting a mix of precipitation
types in the vicinity of this stalled front this morning and
enhanced that in the forecast through this afternoon.
Interestingly, the drier air to the west of this front means a
transition back to snow as the main precipitation type due to
wetbulb effects. So areas from Billings to Forsyth while above
freezing will mainly see slight chances for light snow,
transitioning to mixed precipitation from Forsyth into western
Fallon county and then back to snow in the Baker area where sub
freezing air is deeper. Travelers should use caution in where
mixed precipitation is encountered as cold road surfaces could ice
up some in addition to any snow and ice already present.
Precipitation has been light enough and road conditions haven`t
been reported as any worse than before precipitation began, so no
advisory or SPS being issued at this time but will continue to
monitor the situation.

Winds increase later this afternoon and especially this evening as
the jet stream moves into the area. Light to moderate mountain
wave wind gusts are being hinted at in the HRRR this evening along
the Beartooth/Crazy mountain foothills, eventually working into
the Sheridan foothills late tonight. Existing snow cover should
help to limit how much wind makes it to the lower foothills, but
increased wind speeds for these areas tonight and will see if the
hi-res models go any stronger with subsequent runs. The usual
windy areas of the western foothills will see winds increase
tonight as well with gusts in the 40 to 50 mph range common from
Livingston/Nye north to Big Timber and Harlowton overnight.

For the mountains the combination of recent and ongoing snowfall
and winds increasing to 45 to 80 mph will present additional
impacts from blowing snow with periods of whiteout conditions
expected along with significant drifting snow. Enhanced warning
messaging to this effect and extended the Winter Weather Advisory
for the Bighorn mountains/added the NE Bighorn zone into Saturday
afternoon mainly to account for this additional threat.

Precipitation tonight will be interesting as there may be a couple
of transitions from snow to rain and back to snow across western
and central zones, including at least a low probability (10-20%)
for a wintry mix including freezing rain/sleet. The transition
time looks to be in the 9pm to 4am time frame based on the latest
NBM trends. Much like today in the east, for some locations even
with temperatures above freezing any rain may freeze on surfaces
that remain frozen, including some roads. Something to be aware of
for those traveling across the area tonight. It does look like
precipitation turns back to all snow by sunrise Saturday morning.
Luckily overall precipitation amounts forecast for this mixed
event look low (less than 0.1 inch) due to the westerly downslope
winds working against precipitation making it to the ground.

For this afternoons forecast package will be looking closely at a
Winter Weather advisory for N. Rosebud, Custer, Fallon and
possibly Carter county for areas of 2 to 4 inches of snow tonight
through Saturday night. Will also take a hard look at the mixed
precipitation potential central and west. Chambers

&&

.DISCUSSION...

Through next Thursday...

Very complex weather pattern through the weekend. Have made no
changes to the Winter Highlights for area mountains.

Satellite imagery shows a shortwave dropping thru central MT in NW
flow aloft. Though steepest lapse rates of 7-8c/km are further
east, we are seeing snow showers over the western mountains &
foothills, over to the Pryors & Bighorns. Gardiner web cameras
suggest maybe an inch of new snow. Snow will lessen thru the
morning as the wave departs, but could see some lighter snow
showers linger w/ some diurnal instability over the mountains and
in the east. Attention will then turn to the stronger upstream
shortwave currently just off the BC coast, which has a significant
Pacific moisture tap.

Before diving into specifics, want to point out that complexities
with our weekend weather will revolve around a wavering Canadian
surface boundary, which will periodically backdoor toward but
likely not reach our western foothills. This will have obvious
impacts on temperatures and where overrunning snowfall sets up. It
also means persistently gusty downslope winds along the western
foothills. The one sure thing is that mountain snowfall will
remain periodically heavy on W-NW aspects.

WEEKEND WIND. Upstream wave will induce a period of lee side
pressure falls later today, which will shift from NW to SE
tonight. Ascent and instability aren`t ideal for wind, but still
looks like a period of 30-50 mph gusts in the usual windy spots in
the west (Livingston, Big Timber, Nye & Harlowton) tonight and
Saturday morning. Another ripple of elevated wind gusts, of
similar magnitudes, is expected Saturday night into Sunday. The
probability of 50+ mph gusts is ~45% each time.

WEEKEND SNOW. Additional snow amounts of 10-20" expected on west
aspects of the western mountains from now through the weekend
(heaviest prior to Sunday). Bighorns and Pryors will see
occasional slop over when flow shifts enough to the NW with each
wave passage. The BC wave will provide some overrunning snow
tonight & Saturday. This will be brief from Harlowton to Billings
as downslope winds take over, but a 1-2" accumulation is a fair
bet in the northeast from Forsyth to Miles City, Baker and Ekalaka
(locations which will stay solidly on the cold side of the
surface boundary). The probability of exceeding 2" is about 25%.
Then, on the back side of the wave as a cold front backdoors
through Billings, areas of light snow showers are possible late
Saturday into Saturday night. Later Saturday night into Sunday the
boundary shifts back east and more overrunning light snow is
possible in our far east.

TEMPS THROUGH WEEKEND. Ranging from the 20s to lower 30s in the
east to mid 30s to mid 40s along western foothills. Billings could
see rapid fluctuations tomorrow, with a high near 40F followed by
a late afternoon drop potentially into the 20s. Something to
watch.

NEXT WEEK. With confidence the first half of next week will be
much warmer than normal across the entire region, as the Canadian
boundary exits and we are dominated by downslope winds. Main
impact to monitor is a period of potentially very strong winds
along the western foothills Monday night and Tuesday. Local
guidance shows a >90% chance of 60+ mph gusts at the gap
locations, and EC ensembles show a mean gust of 60 mph at Big
Timber (a very strong signal indeed). There will be a Pacific
wave/moisture too, meaning more snow for the western mountains and
some rain showers at lower elevations. Look for temps in the 40s
to lower 50s Monday & Tuesday, followed by some cooling for
Wednesday. We could see another Canadian front and chance of snow
by next Thursday...but a lot of spread in the ensembles after a
confidently mild first half of the week.

JKL

.AVIATION...

An area of MVFR ceilings, with occasional local reductions to
IFR, will spread across the area east of KBIL this morning and may
impact KSHR through 18Z and KMLS and KBHK through the TAF period.
Lingering showers will taper off this morning before the next
round moves in from the west late afternoon/early evening and
spreads east overnight. Under the heaviest snow showers, expect
occasional ceiling and visibility reductions to IFR/LIFR. Archer

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sat     Sun     Mon     Tue     Wed     Thu
-------------------------------------------------------
BIL 038 028/039 021/041 029/043 040/050 029/041 029/042
    2/S 84/W    20/N    10/B    14/W    54/W    54/W
LVM 039 031/041 027/041 029/045 041/050 026/041 030/045
    7/S 94/W    30/N    30/N    25/W    65/W    54/W
HDN 038 023/037 017/042 024/044 030/048 026/041 025/040
    3/S 87/W    50/B    20/B    25/W    65/W    65/W
MLS 035 018/027 010/035 020/039 030/045 023/036 023/034
    3/O 88/S    51/B    10/B    34/W    42/J    52/W
4BQ 034 021/035 014/039 023/041 030/047 026/038 026/037
    3/O 65/S    20/B    10/B    14/W    53/W    43/W
BHK 033 013/022 004/032 016/038 025/042 017/032 015/032
    3/S 8+/S    34/J    00/B    34/W    42/J    42/J
SHR 037 018/040 018/043 021/046 026/051 023/039 023/041
    2/S 55/W    30/B    10/B    13/W    64/W    54/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning in effect until 2 PM MST Saturday FOR
      ZONES 67-68.
     Winter Weather Advisory in effect until 2 PM MST Saturday FOR
      ZONE 171.
WY...Winter Weather Advisory in effect until 2 PM MST Saturday FOR
      ZONE 198.

&&

$$
weather.gov/billings