793
FXUS65 KBYZ 140039
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
539 PM MST Sat Dec 13 2025

.KEY MESSAGES...

- Warmer and mostly drier weather expected to return Sunday
  through mid week. Expect rapid snowmelt this coming week.

- Periods of strong wind for foothills/gap locations including
  Livingston/Nye starting tonight and lasting through the
  foreseeable future. Strong winds across the entire area
  Wednesday.

- Chance of extreme cross winds along US-191 corridor (Big Timber
  to Judith Gap) Wednesday.

&&

.UPDATE...

Updated forecast to lower low temperatures for tonight. With
plenty of snow on the ground and diminishing cloud cover
temperatures in sheltered low lying areas have plummeted with
sunset. Baker has dropped to -9F already and many other locations
central and east are flirting with forecast lows. For western
areas the opposite is true in that warm advection and scouring of
the cold air has pushed temperatures well above overnight
forecasts. Adjusted both areas for latest trends. In the east went
several degrees cooler than current forecasts. Overall expect
temperatures to rise for most locations overnight as westerly
winds spread warmer air into the area and scour out all but the
lowest sheltered locations. For the Baker area this means a few
hours with apparent temperatures below -25 degrees due to
increasing southerly winds. Expect the exposure to these bitter
apparent temperatures to be short so do not plan on a cold
advisory at this point for Fallon county but will keep an eye on
it this evening. Rest of the forecast in good shape.

Hydrology (For Rapid Snowmelt)...Much warmer temperatures are
expected for Sunday-Tuesday with plenty of snow melt expected. A
look at Montana Mesonet sites across the forecast area shows very
few locations with frozen ground and these are confined to far
northeast sections. Moisture saturation is likewise low across the
area in the shallow to mid depths. So, expect snowmelt to soak
into the ground for the most part over the next few days. That
said those in poor drainage locations should take steps to prevent
water from pooling around foundations and possibly getting into
basements. Also, clear storm drains and drainage infrastructure
to allow the water to flow freely. Chambers

&&

.DISCUSSION...

Tonight through Saturday...

Areas of light snow came to an end earlier today with upslope and
baroclinicity weakening over the area as mid level flow
transitioned from cyclonic to slightly anti-cyclonic. Cold air
remains in place over the high plains and will mean another cold
night for most locations, but warmer air over the western
foothills will slowly push eastward. So temps as far east as
Yellowstone County may slowly rise after midnight into Sunday
morning. This makes the forecast for overnight lows tricky, as
some locations may see coldest overnight temps before midnight.
For example, Billings may drop to single digits this evening
before warming into the 20s by sunrise.

Temps are then expected to warm over the region for Sunday ranging
from 50s west to lower 40s east as ridging aloft kicks in. However,
due to recent deep snowpack models may be over forecasting the
warm up in central zones. Have adjusted temps down a bit to
account for this (used blend of 10-25-50 percentiles over central
zones). Ridging to westerly zonal flow will prevail through the
week resulting in generally above normal temps.

No significant precipitation events are expected this week.
However, a rather dynamic clipper system moving across the region
at midweek may bring a shot of rain/snow to lower elevations (and
wind), with a better chance of snow accumulations on west facing
slopes in the high country.

The primary weather impact this week will be wind. Model
consensus suggest the Idaho Falls/Lewistown pressure gradient
increases into the 10-15 mb range with 700 mb winds of 30-35 kts
tonight into Sunday morning. Local studies suggest 60% chance of
gusts 50 mph or greater. We will keep sub-advisory level winds
(45-55 mph) in forecast for now late tonight/tomorrow for gap
locations (Livingston/Nye), but cannot rule out a gust to near 60
mph. By Monday night the pressure gradient across the Paradise
Valley and foothills reaches 12-17 mb on average which raises
chance of gusts to 60 mph plus to 85%. 700 mb winds increase
substantially Monday/Monday night into Tuesday reaching 50-70 kts
across the western foothills including the US-191 corridor. Local
studies show the chance of gusts over 60 mph averaging 70% at Big
Timber Tuesday morning. If these trends continue wind highlights
will be necessary. After a relative lull Tuesday night, another
period of extreme 700mb winds is possible in relation to the
aforementioned clipper system on Wednesday when progs are
depicting speeds over 80kts. This is a similar scenario to last
Tuesday morning when gusts to 97 mph were recorded at Big Timber
and gusts over 50 mph were common further east over the plains.
This will need to be closely monitored and messaging ramped up.
Current deterministic forecasts do not indicate this level of wind
gusts yet, but based on the pattern we suspect wind gusts
forecasts will increase as we move forward. Periods of strong
winds may continue through the end of the week. BT

.AVIATION...

00z TAF Discussion...

Shallow cold airmass sits over the area this evening. Ridging is
building in from the west aloft and pressure falls are developing
over the northern plains where the jet stream is located. This
combination will work to pull the arctic air eastward tonight into
tomorrow. Latest KBLX VWP shows SW winds @25kt less than 1kft
above the surface. As a result expect warmer air and gusty
southwest winds to develop over the western foothills overnight as
well as poking into at least the higher hills across central
zones. This will include KBIL though have kept wind gusts at the
lower end of whats possible for now. KLVM will see gusts
increasing steadily overnight toward 40kts by sunrise. Low level
wind shear is in the TAFs for KBIL/KSHR/KMLS at various times
through tomorrow morning. Warm advection usually leads to some
low lying fog development this time of year, but the current
situation shows strong enough winds just off the surface that
mechanical mixing will likely inhibit fog development for all but
he lowest river valley locations across the eastern half of the
forecast area. Otherwise VFR conditions will prevail through
Sunday. Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Sun     Mon     Tue     Wed     Thu     Fri     Sat
-----------------------------------------------------------
BIL 004/041 031/046 038/049 035/048 023/039 029/047 027/043
    00/B    00/B    01/B    16/O    11/B    24/O    42/S
LVM 029/053 035/055 042/052 038/049 025/040 030/047 027/041
    00/N    00/N    01/N    28/O    12/S    56/O    42/S
HDN 002/039 020/045 034/048 031/048 016/037 024/047 023/042
    00/B    00/U    01/B    27/O    21/B    24/O    42/S
MLS 903/038 023/042 034/046 030/045 012/027 018/041 017/035
    00/U    00/B    01/B    24/O    21/B    22/O    31/B
4BQ 007/043 025/044 035/049 032/050 017/035 025/047 024/041
    00/U    00/U    01/B    14/O    20/B    12/O    31/B
BHK 912/039 023/043 032/046 025/042 007/023 011/040 013/032
    00/U    00/U    01/B    24/O    20/B    12/O    31/B
SHR 005/047 027/052 033/053 030/053 018/040 023/050 022/042
    00/U    00/U    01/B    15/O    21/B    12/O    42/S

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.

&&

$$
weather.gov/billings