219
FXUS65 KBYZ 041231
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
631 AM MDT Thu Sep 4 2025

.KEY MESSAGES...

- Windy today behind an early morning cold frontal passage;
  northwest to north winds gusting 30-50 mph, strongest east of
  Billings.

- A more significant but brief surge of Canadian wildfire smoke is
  expected today; be prepared for reduced visibility and poorer
  air quality; air quality improves late afternoon and evening.

- Seasonably cool tonight to Saturday; frost possible in eastern
  sheltered valleys Friday night.

- Warmer with increasing chances of precip this weekend into next
  week; above normal temps favored through next week.

&&

.DISCUSSION...

Through Friday Night...

Satellite imagery shows a clipper dropping through AB, and latest
mesoanalysis shows the associated cold front is near the MT
border. There are a variety of issues to consider associated with
today`s system.

(1) Wildfire smoke: The Canadian frontal passage is expected to
bring an increase in near surface smoke upon its arrival, but
latest model trends are a bit more benign, and the window of
poorest air quality should be short-lived. Visibilities in our
region are 9-10SM as of 1am, while upstream in AB they are 4-6SM,
with an air quality designated "unhealthy". Expect thicker smoke
to spread into our cwa (especially the west half) beginning around
sunrise. As the surface high moves in and winds veer more to the
N/NE, "clean air" advection is expected to begin this afternoon.
Would expect much clearer skies by this evening. So overall we are
looking at a 6-9 hour window of worst smoke impacts.

(2) Wind: Post-frontal/mixed NW-N winds will be gusty today. Cold
advection begins in the 12-15z time frame and thus the increasing
wind will occur in the morning, with strongest winds looking like
late morning to mid afternoon. 700mb winds over our east currently
analyzed to be 40kts, and these should max out at 45-50kts before
midday. We won`t quite mix into that layer but forecast soundings
show a likelihood of 30-50 mph gusts, strongest near the Dakotas.
NW flow favored locations like Judith Gap and Sheridan may also
see gusts near 45 mph. Winds will decrease by sunset and turn much
lighter tonight as high pressure continues to settle in from the
north. Below are a few notable gust probabilities:
50+ mph: 25% from Baker to Ekalaka, near 0% elsewhere
40+ mph: 80% Baker to Ekalaka, 50-60% at Judith Gap & Sheridan

(3) Fire Weather: Arrival of cold advection early today helps
here. We are looking at temps holding in the 70s and min RHs of
25-35%, so despite the strong winds, fire concerns will be only
marginally elevated today. That said, take care to not spark a
fire!

(3) Precip Chances: Not good as the air mass is a dry one, but
there seems to be enough shallow mid level moisture and
instability for some light showers in our southern upslope areas
(i.e. Red Lodge, Pryor & Sheridan) between noon and 6pm. The
remainder of the short term period will be dry.

Finally, we are looking at a taste of fall the next couple days
per the dry/cool Canadian air mass with origins in the far north.
Look for lows in the mid 30s to mid 40s tonight, highs Friday in
the 60s to lower 70s, then lows in the 30s to lower 40s Friday
night. There is a risk of frost, most notably in eastern valleys
Friday night. The probability of reaching 36F at Baker is 80%,
while there is a 20% chance of reaching 32F. Other notoriously
cool spots like Mizpah & Brandenberg will also likely see a frost.
Those with sensitive outdoor plants/gardens may want to take
precautions the next couple nights.

JKL

Saturday through Wednesday...

Saturday into Sunday will see heights gradually rise as low
amplitude ridging builds over the region. With this, temperatures
Saturday look to remain cooler in the 60s and 70s before warming
back near to slightly above normal in the upper 70s to mid 80s on
Sunday. As far as precipitation goes for this weekend, Saturday
has trended drier under the building ridge aloft, so the chance of
any weak showers or thunderstorms over the Absaroka- Beartooth
Mountains is now less than 15 percent. However, the chance of
precipitation remains over the mountains and foothills of south-
central Montana and northern Wyoming on Sunday afternoon and
evening as a push of moisture and energy aloft is still
anticipated (20 to 60 percent chance, greatest over the Absaroka-
Beartooth Mountains). While a few showers or weak thunderstorms
could move out over the plains towards Billings on Sunday,
instability looks to drop quickly off the mountains, limiting the
activity over the plains. With this activity, precipitation
amounts look to remain generally light with the best chance of
seeing a wetting rain (0.10 inches) existing over the mountains of
south-central Montana (20 to 40 percent chance).

As we move into next week, a broad trough looks to move in over
the west coast of the United States. While cluster analysis
suggests there is still some uncertainty in the depth and exact
position of this trough, this pattern is favorable for a daily
chance of showers and thunderstorms over at least portions of the
area through the first half of next week. On Monday, the chance
of precipitation looks to remain over the mountains and foothills
before spreading across much of the area Tuesday and Wednesday.
While there is no strong signal for any severe weather over the
plains Tuesday and Wednesday at this time, increased instability
and low- level moisture from south-easterly winds in far eastern
Montana may allow for a few more robust thunderstorms to develop.
Will have to see how things trend. Otherwise, temperatures moving
into next week look to hold steady around to slightly above normal
in the upper 70s to mid 80s. Arends

&&

.AVIATION...

Cold front moving into the region early this morning will bring
gusty NW-N winds through the day. Look for 25-45 knot gusts,
greatest near the Dakotas including at KBHK. Winds will decrease
quickly this evening as high pressure builds in from the north.

There will be a period of Canadian wildfire smoke behind the
frontal passage, but there remains uncertainty with how low
visibilities will drop. Upstream observations suggest a few hours
of 4-6SM possible, and all TAF sites could be affected (though
lowest visibilities should be west of KMLS). Smoke will clear with
a shift to N-NE winds this afternoon and evening. VFR will
prevail once the smoke clears. Will continue to monitor smoke
trends and amend TAFs if necessary.

JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Fri     Sat     Sun     Mon     Tue     Wed
-------------------------------------------------------
BIL 076 044/070 043/076 046/082 058/086 057/083 055/080
    1/N 00/U    00/U    01/B    11/B    22/T    22/T
LVM 078 037/072 036/078 044/083 050/082 048/076 046/075
    1/K 00/U    00/U    02/T    22/T    33/T    33/T
HDN 074 039/070 037/076 041/084 051/087 053/085 052/083
    0/N 00/U    00/U    00/B    00/B    21/B    22/T
MLS 072 042/067 038/069 043/081 050/087 055/086 058/084
    0/N 00/U    00/U    00/U    00/B    11/B    21/B
4BQ 071 042/064 038/068 042/080 053/084 056/085 058/083
    0/N 00/U    00/U    00/U    00/B    01/B    21/B
BHK 070 037/063 033/066 038/077 046/085 052/083 053/081
    0/N 00/U    00/U    00/U    00/B    00/B    21/B
SHR 076 037/068 036/073 039/082 051/083 051/082 050/081
    2/W 00/U    00/U    00/U    01/B    22/T    22/T

&&

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

&&

$$
weather.gov/billings