Boyd, Montana Weather Forecast Discussion

415
FXUS65 KBYZ 220149
AFDBYZ
Area Forecast Discussion
National Weather Service Billings MT
749 PM MDT Sun Sep 21 2025
.KEY MESSAGES...
- Weather system brings precipitation (40-80% chance from Rosebud
  County west), cooler temperatures, and gusty northwest winds to
  the region into Monday.
- Wet mountain snow (up to a few inches) forecast above 9,000 to
  10,000 feet late today into Monday.
- Warm and dry conditions return by the middle of the week.
&&
.UPDATE...
Widely scattered showers and a few weak t-storms have impacted
western zones since late afternoon, and in fact, as of 0130z there
is a modest (~20kt) outflow boundary moving from Stillwater into
western Yellowstone County. This is not the cold front, however.
Latest surface analysis shows a cold front having pushed thru
Bozeman and about to enter the far western boundary of our cwa.
Showers (w/ some embedded lightning) are a bit more robust along
and behind the front, so expect precip chances to begin to
increase in the far west shortly. Ascent from the main upper trof
is still to our west but will arrive later tonight. Mesoanalysis
shows freezing levels of around 10kft over WA. We will see snow
levels drop over our mountains beginning late tonight, and current
forecast of these snow levels falling to 9-10kft look good.
Overall, forecast is in good shape. Have adjusted pops/wx per
current trends, and have increased post-frontal winds a bit
through tonight. Expect a few hours of 15-25 knot gusts as the
front passes.
18z ensembles show precip over the next 24 hours of 0.25-0.50"
over the mountains tapering to 0.10-0.20" over central areas
(including Billings) and little to no precip east of Rosebud
County.
JKL
&&
.DISCUSSION...
The rest of today through Sunday...
The chance of precipitation will increase this afternoon into
Monday, beginning over the west, as a weather system and
associated cold front moves through. Then, Tuesday into the
weekend will become warm and mostly dry as an upper level ridge
builds in.
The mountains and foothills have the best chance of precip, with a
60-80% chance of at least 0.25 inch, while over the plains as far
east as Rosebud County may see one to two tenths, with generally a
less than 40% chance of seeing more than 0.25 inch.
Over the mountains, precip will begin as rain before snow levels
drop between 9000 to 10000 ft. Models have moved the timing of the
snow levels dropping to Monday morning, which is when the best
chance of precip is expected to exit the Absaroka/Beartooths and
begin over the Bighorns. As a result, snow amounts have decreased
slightly over the Absaroka/Beartooth mountains and increased over
the Bighorns. The greatest snow accumulations, up to a few inches,
continue to be expected over the highest peaks, with generally a
less than 20% chance of more than 4 inches of snow. Over the
Beartooth Pass, there is a 20% chance of up to 1 inch of snow.
Over US-14 in the Bighorn mountains, there is a 30% chance of up
to 2 inches of snow.
A few thunderstorms, especially over the mountains, are possible
(10-30% chance) into Monday, however, no severe storms are
expected. With any storms that develop, winds may gust to around
35-45 mph. Otherwise, Monday will be generally breezy behind the
front, with widespread gusts in the 20s and 30s mph.
By Tuesday, the system will have exited the region and upper level
ridging will begin to build in, bringing warmer and mostly dry
conditions. At the end of the week, the ridge begins to flatten
and may allow isolated (10-20% chance) showers and thunderstorms
during the afternoon and evening hours.
Highs Monday will be in the low 60s over the west to low 70s over
the east. Monday night into Tuesday morning will see cold
temperatures, with lows dropping into the mid 30s over the west
to mid 40s over the east. Temperatures will then increase under
the building ridge, with highs generally in the 80s for midweek
into the weekend. Archer
.AVIATION...
Showers will become widespread west of Rosebud County tonight.
Expect local MVFR near the foothills, and western mountains will
become obscured tonight as snow levels fall to near 9000 feet. In
addition to the precipitation, a cold frontal passage tonight will
bring a shift to NW winds gusting 15-30 knots. NW winds will
persist into Monday, decreasing from west to east through the day.
STP/PM
&&
.PRELIMINARY POINT TEMP/POPS...
Mon     Tue     Wed     Thu     Fri     Sat     Sun
-----------------------------------------------------------
BIL 054/064 045/072 050/082 053/083 054/083 052/078 052/078
    57/W    00/U    00/U    00/U    00/U    10/U    11/U
LVM 046/063 037/073 041/081 045/082 046/080 045/077 045/075
    95/W    00/U    00/U    00/U    01/U    11/U    11/U
HDN 052/064 042/073 045/083 047/083 047/085 048/081 047/079
    27/W    10/U    00/U    00/U    00/U    10/U    10/U
MLS 054/069 046/075 047/083 049/082 050/085 050/080 052/080
    12/W    00/U    00/U    00/U    00/U    00/U    00/U
4BQ 053/066 048/072 048/080 050/081 051/083 051/079 052/079
    02/W    10/U    00/U    00/U    00/U    10/U    00/U
BHK 047/073 044/074 046/082 049/082 049/083 047/077 047/078
    00/N    00/U    00/U    00/U    00/U    00/U    00/U
SHR 051/061 041/071 042/080 045/082 047/083 046/079 046/078
    18/W    30/U    00/U    00/U    00/U    10/U    01/U
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings

NWS BYZ Office Area Forecast Discussion