483
FXUS65 KBYZ 151502
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
902 AM MDT Wed Oct 15 2025

.KEY MESSAGES...

- Areas of low clouds and fog continue today.

- Precipitation chances increase today; widespread lower elevation
  rain and mountain snow tonight to Thursday evening; snow levels
  around 6500 feet.

- Breezy with scattered showers Friday and Saturday.

- Dry and warmer Sunday, but another Pacific system arrives next
  Monday/Tuesday.

&&

.UPDATE...
An impressive amount of lightning this morning in the middle of
our forecast area. There remains an area of thunderstorms from
eastern Treasure through northern Rosebud Counties as of 845am.
This activity is along an axis of strong 850-700mb warm advection
with sufficient elevated instability, and should exit by noon as
the forcing relaxes. After a short break, more showers and
embedded t-storms arrive from the south this afternoon. There are
cooling tops in southern WY and this seems to be associated with a
shortwave expected to arrive later. Generally speaking, as the
upper low over the central great basin lifts slowly to the
northeast, we will be under increasingly diffluent flow aloft.

Forecast is in good shape with the details of the approaching
weather system. Have dropped the dense fog advisory for Carter and
Powder River. Tonight, as winds shift to W-NW, the risk of fog and
low clouds will decrease substantially, even with the precip.

JKL

&&

.DISCUSSION...

Through Thursday...
A large high amplitude trough over the Great Basin is dominating
the weather across the region. As this feature slowly progresses
eastwards, shortwaves will eject out ahead of the parent through
bringing repeated chances for precipitation over the next two
days.

Weak, yet persistent, return flow out of the east-southeast will
continue advecting in warm air as well as higher moisture content
this morning. This will allow for the development of widespread
advection fog, especially in southeast MT. Farther to the north
and west this increase in moisture may manifest as low cloud bases
with several METARs across the region reporting ceilings below
1kft at this hour. As showers move over the region this morning
and throughout the day Wednesday their will be periods where the
increased mixing from the precip will scatter out the fog and
raise the ceilings before fog may have the chance to redevelop
afterwards as the stability sets back in. As the day goes on,
precipitation will become more widespread which will allow for
most of the fog to scatter out.

Wednesday night the main upper level low will move northeastwards
bringing most of the CWA under strong diffluent flow aloft which
will aid in much of the CWA seeing steady precipitation. PWAT
values will not exceed 0.8" across the region, however the
persistent precipitation, especially across eastern Montana, may
lead to some localized ponding of water.

In terms of mountain snow, it appears that the real show will be
confined to the Absaroka/Beartooths. Snow levels are currently
sitting around 9kft MSL and forecast to slowly drop to around 6kft
MSL by the end of the day Thursday. These higher snow levels are
also indicative of lower snow ratios which are keeping snow totals
down. The highest totals will be on the south-southwest facing
aspects; but even then, the storm total snowfall is forecast to
remain under a foot. WMR

Friday and Beyond...
Behind the trough, west-northwesterly flow will blanket the entire
region which may bring with it some gusty winds. Mid and long
range models all keep 700mb winds under 50kts which will also keep
surface winds on the more modest side of things. The strongest
gusts may occur around Harlowton and Big Timber as these
locations are favorable for terrain gaping with a westerly flow.
Even then, surface wind gusts are still forecast to be under 50mph
region wide.

Moving into the weekend, there is decent agreement amongst the
ensembles that at least shortwave rigging will dominate the
Northern Rockies. Highs for Saturday and Sunday may even be a few
degrees above average with dry conditions region-wide.

Ensemble clusters continue to show another trough digging into
the west early next week with pretty good consensus. Of course
the strength of this trough is still in disagreement and may have
some tropical influence involved as well. WMR

.AVIATION...

Areas of low stratus and fog will continue to impact much of the
region for a good portion of the day, with reductions to
MVFR/IFR/LIFR. Showers with a few embedded t-storms will decrease
through the late morning, then increase this afternoon and evening
as a strong weather system approaches. Expect periodic reductions
to ceilings/visibilities to continue through tonight as
precipitation becomes widespread, but the risk of dense fog and
low clouds will decrease as surface winds shift to the W-NW. This
will be something to monitor. Mountains will be occasionally
obscured in rain/snow showers. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Thu     Fri     Sat     Sun     Mon     Tue
-------------------------------------------------------
BIL 047 042/049 042/060 037/056 040/066 040/057 033/053
    3/W 68/W    42/W    31/U    02/W    44/W    21/B
LVM 048 034/048 031/058 029/057 036/063 031/053 026/051
    7/W 68/W    32/W    40/U    13/W    65/W    21/B
HDN 049 040/049 039/061 034/056 035/068 038/058 030/055
    3/W 89/W    62/W    51/U    11/B    54/W    31/B
MLS 057 045/051 040/058 036/056 035/065 039/057 033/054
    6/W 89/W    72/W    20/U    01/B    23/W    21/B
4BQ 059 044/049 040/057 036/052 035/067 039/056 032/053
    3/W 99/W    51/B    31/U    00/U    23/W    21/B
BHK 050 041/051 037/059 032/053 030/065 035/056 030/054
    4/W 99/W    72/W    10/N    00/U    22/W    21/B
SHR 050 039/047 031/060 030/053 030/070 033/057 026/052
    6/T 89/W    52/W    51/U    01/U    45/W    32/W

&&

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

&&

$$
weather.gov/billings