313
FXUS65 KBYZ 110605
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
1205 AM MDT Fri Sep 11 2026

.KEY MESSAGES...

- Cooler weather today into next week.

- Occasional chances of showers (mainly light) today through
  Sunday night. Scattered thunderstorms possible in southeast
  Montana Sunday.

- Snow showers in the mountains above 10000 feet Sunday and Sunday
  night; minimal to no accumulation.


&&

.DISCUSSION...

Next 7 Days...

The forecast for Friday and Saturday remains roughly the same as
what we have been seeing for the past 1 to 2 days. A cold front is
forecast to move through the CWA this morning which will bring
with it our first taste of fall. In addition to the notable
increase in moisture, the high temperatures today will be roughly
10 degrees below average for most locations, or 20 degrees colder
than what we saw Thursday. Just behind this FROPA, and lingering
through the day Friday, there will be scattered showers and
thunderstorms. The highest coverage of precip will be in the
mountains and foothills of south-centeral Montana and decreasing
in coverage with eastward extent. Saturday will be fairly similar
to Friday with temps 10 degrees below average and isolated showers
across the region. Coverage of precipitation will decrease through
the day leading to widely isolated showers by evening.

Over the past day or so models have trended the Sunday shortwave
farther to the north. This would result in warmer and drier
conditions then previously forecast. At one point there was a few
inches of snow forecast above 9kft and a high chance of a wetting
rain across the entire CWA Sunday, there is now a less than a 50%
chance region-wide for a wetting rain Sunday. With this more
northerly track of the low now, we will actually see a slight temperature
rebound on Sunday. There is still a large model spread on how
much temps will rebound, but highs near average are possible
before another push of cool air to start the work week.

With parts of our CWA now in the "dry slot" of the low on Sunday,
there is a slight chance that some stronger thunderstorms may
develop in the eastern portion of the CWA. During the afternoon
and evening Sunday, a cold front will push from west to east
across the area acting the the primary source of lift for any
convection. Due to the cooler temps, modeled MU-CAPE values remain
under 1000 J/Kg, however this would be plenty sufficient given
the strong source of lift aiding CI as the front pushes through
late afternoon and evening. Additionally, shear values in SE
Montana will be in the 30-50kt range due to the proximity and
location of the upper level low. In terms of moisture, PWAT values
are forecast to exceed 1" in the eastern 1/3 of the CWA ahead of
the FROPA which will be plenty for thunderstorm development.
With this event just now being depicted on models, plus it being
several days away, there is still several questions surrounding
the event. The few CAMs that run out that far are depicting some
strong storms in NE WY and just clipping SE Montana. This signal
will be monitored as we get closer to the potential event.

To start the work week we will remain under the main branch of
the jet stream which will allow for near to just below average
temperatures to linger through the first part of the week. There
is a chance that isolated showers continue with these cooler
temperatures due to the strong jet dynamics overhead. WMR

.AVIATION...

There is a small chance (~10%) for MVFR conditions with low
clouds this morning at KMLS and KBIL. Isolated showers and a few
thunderstorms are expected to enter south central MT around 12Z
spreading east through the morning and afternoon. TS

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sat     Sun     Mon     Tue     Wed     Thu
-------------------------------------------------------
BIL 067 049/066 046/071 047/066 042/066 044/068 044/073
    2/W 30/E    23/W    20/N    00/B    00/B    10/U
LVM 070 043/066 040/069 038/064 035/066 038/069 039/074
    4/T 51/E    33/T    41/N    00/U    01/U    11/U
HDN 070 045/070 043/076 043/068 038/070 040/070 040/075
    5/W 61/E    22/W    50/N    00/U    10/B    10/U
MLS 070 048/065 045/071 048/066 041/066 044/070 044/073
    2/W 23/W    24/W    91/N    00/U    11/B    10/U
4BQ 074 048/069 048/073 048/068 041/067 045/072 044/075
    0/U 43/W    43/W    70/N    00/U    11/B    10/U
BHK 073 042/066 040/067 043/067 037/067 040/073 040/074
    2/N 24/W    52/W    92/W    00/U    12/W    10/U
SHR 076 042/072 043/077 041/067 037/068 040/071 038/075
    2/T 31/B    31/B    30/N    00/U    11/U    11/U

&&

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

&&

$$
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