468
FXUS65 KBYZ 080909
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
209 AM MST Mon Dec 8 2025

.KEY MESSAGES...

- Very strong southwest to west winds along the western foothills
  tonight through Tuesday morning. Gusts fo 60-70 mph are likely.

- Strong west to northwest winds possible across the plains on
  Tuesday. Wind gusts exceeding 50 mph are likely.

- Warmer than normal temperatures through Wednesday.

- Prolonged period of snowfall in the western mountains. Potential
  for multiple feet of snow through Wednesday, greatest on west
  aspects of the Beartooth Absarokas.

- Next shot of cold air is expected to arrive Thursday, which may
  be accompanied by accumulating snowfall through Friday and maybe
  into Saturday. Uncertainty remains high so please monitor the
  forecast.

&&

.DISCUSSION...
Through next Sunday...

Very active week of weather in store. Be prepared!

Weak shortwave moving across eastern MT is producing some light
rain in our east, as reported at Miles City along with a temp of
32F. Surface temps have climbed to near 40F just SW of Miles City
so it appears the risk of light freezing rain is both real and
brief. Temp at Baker is 23F and some light rain could be there
soon. Elsewhere, downslope flow has pushed temps to the mid 30s to
mid 40s (43F at Livingston at 1am). This will translate to
widespread 40s today and near 50F closer to the foothills.

Lee side trof has brought gusty winds to the western foothills
since last evening, but the shortwave passage has shifted
strongest winds from the gap locations to Big Timber & Harlowton.
That said, a 58 mph gust was observed at a Livingston DOT station
during the evening, and a site near Nye reported 60 mph. Will make
no changes to the Wind Advisory in effect for the gap areas
through 5pm this afternoon.

The real story, as fas as wind is concerned, is a strong episode
coming tonight & Tuesday. Have upgraded all western High Wind
Watches to Warnings. Mid level winds expected to increase to
70-80kts with a IDA-LWT gradient up to near 20mb tonight. This
will get gap flow elevated and could reach 80 mph gusts per local
guidance. The probability of gusts reaching 75 mph is 75%. The
westerly flow won`t favor mountain waves along the Beartooths or
Bighorns, but this is a possibility in the lee of the Crazy
Mountains late tonight prior to a cold front`s arrival. Some
models show mountain top winds near 90 knots here. With or without
mountain waves, by early Tuesday strong west winds will develop
along the US-191 corridor from Big Timber to Harlowton with gusts
likely to exceed 60 mph (80% chance). East of the immediate
foothills it gets more uncertain, as always, but there are a few
items that promote strong winds surfacing further east: (1)
synoptic descent arriving during the day, (2) a lack of snow
cover after a very mild night promoting mixing, and (3) showers
may help strong winds to surface. HRRR over the past couple runs
have shown 50+ knot surface wind gusts spreading east, and this
seems attributed to the deeper mixed layer than some other lower
resolution models show. All of that said, will keep the High Wind
Watch intact for remaining lower elevations.

Post-frontal winds will shift to the NW and decrease fairly
quickly late Tuesday. It does appear there is another period of
foothills wind in store for Wednesday and Wednesday night, but
ingredients aren`t as dire as tonight/tomorrow. Currently looks
like gusts of 40-50 mph.

Quick glance at satellite imagery shows a substantial fetch of
Pacific subtropical moisture which will push through the northern
Rockies over the next several days. Ensembles show pwat amounts
2-3 standard deviations above normal. Orographic flow favors the
Beartooth-Absarokas for heavy snow and have upgraded the Watch to
a Winter Storm Warning for tonight through Wednesday for 1-2 feet
of snowfall on west aspects (90% chance of 12+ inches). The
expectation is for additional snow from Wednesday night thru the
end of the week. The snow will indeed pile up and avalanche danger
in the mountains around Cooke City may increase over the coming
days. Something to keep in mind.

Otherwise, the moisture will bring periods of rain/snow to lower
elevations, starting with warm frontal wet snow from west to east
on Wednesday, then more Thursday as another wave arrives along
with a cold front. Do not expect much snow accumulation at lower
elevations during this time. That could change by Thursday as
Canadian cold sags back into the area. Models have trended a bit
slower with its arrival and it now looks like Thursday is the
transition period. There remains a great deal of uncertainty with
regard to the depth of the cold air and where the heaviest precip
will set up (there are a couple embedded shortwaves between
Thursday night and Saturday), but conceptually in a Pacific
overrunning situation the heaviest amounts will be east of the
foothills. Make no mistake, if the cold air arrives as it appears
it will, moisture content and a deep DGZ support heavy snowfall,
somewhere. This may very well include Billings. Stay tuned.

After very mild weather today through Wednesday (40s to mid 50s
for highs) we should take a dive to the single digits and teens by
the end of the work week. Ensemble consensus is for below normal
temps with a lee side surface high thru Saturday. Models diverge
further thereafter, but cluster analyses favor a warmer downslope
pattern arriving by Sunday and persisting into next week.

JKL

.AVIATION...

Strong winds continue over the western foothills, including KLVM,
with gusts around 40-50 kts. These winds will increase late this
evening into Tuesday morning, with gusts in the 60s kts. For all
other TAF sites, winds will increase Tuesday morning, with gusts
of 40-50 kts common by Tuesday afternoon. Archer

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Tue     Wed     Thu     Fri     Sat     Sun
-------------------------------------------------------
BIL 047 042/053 032/050 030/037 006/016 007/027 017/042
    1/N 14/W    58/W    66/O    75/S    22/S    00/B
LVM 047 044/050 034/053 038/047 019/038 029/045 029/048
    1/N 36/W    89/W    66/O    64/O    11/B    01/B
HDN 047 037/053 029/047 026/036 004/016 003/024 008/040
    1/B 26/W    59/W    87/O    76/S    32/S    11/B
MLS 042 032/049 024/039 020/027 902/009 001/018 003/033
    1/E 32/W    17/W    65/S    53/S    42/S    10/B
4BQ 045 034/051 027/042 026/034 003/014 005/023 009/038
    1/B 22/W    27/W    75/O    64/S    32/S    10/B
BHK 042 029/046 018/034 016/028 907/006 904/018 003/032
    3/W 72/W    04/J    64/S    52/S    42/S    10/B
SHR 047 029/054 026/049 026/038 006/024 010/034 016/046
    0/B 14/W    57/W    76/O    64/S    21/B    10/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...High Wind Watch in effect from late tonight through Tuesday
      afternoon FOR ZONES 29>33-36-37-57-58-138-169-170-173-235.
     High Wind Warning in effect from 5 AM to 5 PM MST Tuesday FOR
      ZONES 34-42.
     High Wind Warning in effect from 11 PM this evening to 5 PM
      MST Tuesday FOR ZONES 63-141-172-228.
     Wind Advisory in effect until 5 PM MST this afternoon FOR
      ZONES 65-66.
     High Wind Warning in effect from 5 PM this afternoon to 11 AM
      MST Tuesday FOR ZONES 65>68.
     Winter Storm Warning in effect from 5 PM this afternoon to 5
      PM MST Wednesday FOR ZONE 67.
WY...High Wind Watch in effect from late tonight through Tuesday
      afternoon FOR ZONE 199.

&&

$$
weather.gov/billings