390
FXUS65 KBYZ 260704
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
104 AM MDT Sat Sep 26 2026

.KEY MESSAGES...

- Expect cooler temperatures this weekend.

- Unsettled conditions Sunday into Monday with seasonable
  temperatures and a chance for precipitation.

&&

.DISCUSSION...

Saturday through Friday...

Dry cold front will move through the forecast through the early
monring hours, bringing a period of gusty (20-40mph, locally
stronger Musselshell to Fallon county) northwest winds to the
region, and cooler more seasonal temperatures for the weekend. At
this point not seeing any measurable precipitation with this
system as the main energy and push of moisture tracks northeast
away from our area. Highs on Saturday look very pleasant around 70
degrees with sunny skies and diminishing wind in the afternoon.

Next system set to impact the region arrives late Sunday. Ahead of
this system expect quiet weather across the region with continued
seasonal temperatures, but an increase in cloud cover Sunday. That
said, during the day atmospheric moisture levels will climb as low
level southeast winds advect plains moisture into the area,
boosting PWATs above an inch east of Billings Sunday night through
Monday night. So, there is significant moisture available for a
storm system to utilize late this weekend into early next week.
The problem is that the west coast system that is forecast to move
into the region is splitting its energy, sending the vast majority
of the forcing around us. As a result, precipitation probabilities
and amounts are trending downward run to run in the models. The
latest NBM (which plays catchup to the model runs, so is a bit
behind in lowering precipitation chances) shows the potential for
a quarter of an inch of precipitation Sunday night into Tuesday
morning confined to areas near the eastern state line at around a
50% probability. For most of the forecast area the probability
for a tenth of an inch is sitting under 20%. Probabilities for
snow have plummeted in the western mountains as well, with chances
for an inch or more during the event sitting at 30% and that is
above 10.5kft. If that holds, impacts to travel or activities in
the mountains will be minor.

Dry period builds in with zonal flow aloft keeping sunny skies and
breezy afternoons over the region Tuesday through Thursday. Next
potential storm system is being advertised for next weekend. The
rub is that only about 40% of ensemble members are advertising a
storm system of any strength during this period. 20% are sliding
an Alberta Clipper type trof into the Northern Plains/Great Lakes
bypassing our area to the north/east, and the remaining 40% of
ensembles including a whopping 76% of ECMWF members keep a
warm/dry zonal flow pattern transitioning to a ridge over the area
Friday-Sunday. So, not a lot of confidence in the far extended
forecasts. That makes sense given the chaotic nature of numerous
tropical systems roaming the Pacific, impacting the upper pattern
(tele-connections). For now advertising temperatures in the 60s
with a chance of lower elevation precipitation, and a chance for
snow in the mountains Friday into the weekend, but expect
potentially significant changes as the NBM picks up on the
uncertainty within a majority of todays ensemble model runs.
Chambers

.AVIATION...

VFR flight conditions will prevail through today, though there
could be (20-30% chance) a few hours of stratus (3kft or lower)
and local fog development (10% 3sm or lower) from 08-12z along
the eastern state line, including KBHK. A dry cold front will move
through the forecast area through early morning. Winds will turn
to the north-northwest gusting 20 to 35kts for a few hours post
frontal, strongest over areas north and east of Billings.
Nocturnal inversion may protect some areas from the gusty winds,
but the strong pressure rises associated with the frontal passage
should be enough to stir surface winds up for an hour or so just
about everywhere. Low level wind shear is in the forecast for most
of the area for at least a few hours ahead of the front where
southerly winds could reach 40kts just off the surface prior to
the front moving through. A bit of low cloud development (~4kft
AGL) is forecast along and behind the front through mid day,
but at this time the downslope winds are expected to prevent
precipitation or any post frontal flight category restrictions.
Winds diminish by mid day for all areas. Chambers

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Sun     Mon     Tue     Wed     Thu     Fri
-------------------------------------------------------
BIL 069 047/063 047/066 046/073 050/071 047/068 047/065
    0/U 02/E    21/E    00/U    00/U    00/B    12/W
LVM 069 042/065 040/068 039/072 044/071 040/070 040/065
    0/U 01/E    12/T    00/U    11/U    01/B    12/W
HDN 071 044/068 045/068 044/074 047/072 045/070 045/067
    0/U 02/E    22/W    00/U    00/U    00/B    12/W
MLS 070 047/068 050/068 047/073 050/072 047/068 047/066
    0/U 02/E    32/W    00/U    10/U    00/B    11/B
4BQ 070 048/072 053/067 048/072 051/072 048/069 048/068
    0/U 01/B    42/W    10/U    00/U    00/U    01/B
BHK 070 044/069 049/067 045/071 048/072 045/067 044/066
    0/U 02/E    74/W    10/U    01/U    00/B    11/B
SHR 072 042/068 045/065 042/071 043/071 042/069 041/067
    0/U 00/B    24/W    20/U    01/U    10/U    12/W

&&

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

&&

$$
weather.gov/billings