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FXUS65 KBYZ 211934
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
134 PM MDT Mon Sep 21 2026

.KEY MESSAGES...

- Warmer and drier much of the work week. 80s return midweek.

- Scattered showers and storms late Tuesday into Wednesday.

&&

.DISCUSSION...

Rest of Today through Sunday...

Low clouds continue to clear over southeast Montana and portions
of northern Wyoming this afternoon. Ridging will generally take
over the pattern this week, bringing warmer and mostly dry
conditions.

HiRes models show patchy fog developing along and north of I-90
from Billings to Livingston tonight. Coverage and density are
expected to be less than this morning though reductions to
visibility will still impact travel. This will continue to be
monitored overnight.

Models and ensembles continue to depict a shortwave moving
through the region late Tuesday through early Wednesday. This
looks to bring the best chance of precipitation to much of
southern Montana and northern Wyoming this week. Disagreement on
the extent of precipitation remains amongst deterministic models,
though the latest forecast has a low to moderate chance across the
area. The best chance exists in the Absaroka/Beartooth, Pryor,
and Bighorn mountains.

While soundings do show CAPE values between 1000 and 2000 J/kg
Tuesday afternoon/ evening, the lack of sufficient forcing and
mostly weak shear will likely keep the chance for storms very
low. Overnight though, a few thunderstorms could develop as the
shortwave moves through. Though surface inversions will develop,
elevated instability of a several hundred J/kg of CAPE will
linger mostly in far southeast Montana. The main concerns with any
storms are gusty winds, heavy rainfall, and hail. The risk for
stronger to potentially severe thunderstorms remains low at this
time.

The rest of Wednesday through Friday, the forecast has a very low
chance (less than 15 percent) for precipitation across the area.
Winds look to increase over the foothills west of Billings on
Friday, ahead of a deepening trough over the Pacific Northwest.
Uncertainty remains high with this system over the weekend. The
latest ensemble tracks take it through northwest Montana and into
Canada, leaving southeast MT and northern WY on the drier side of
things. Continue to monitor the forecast as the weekend
approaches.

High temperatures are forecast in the 70s to 80 degrees Tuesday
and Wednesday, and upper 70s to mid 80s Thursday and Friday.

Matos

.AVIATION...

18Z discussion.

Low clouds will continue to clear for all but far southeastern
Montana, including KBHK, this afternoon. Fog is possible (10-20%
chance) near all TAF sites overnight. Mid and high clouds move in
from the west Tuesday morning. Archer

&&

.PRELIMINARY POINT TEMP/POPS...

    Tue     Wed     Thu     Fri     Sat     Sun     Mon
-----------------------------------------------------------
BIL 047/077 054/079 052/082 053/082 053/071 046/069 048/069
    00/B    31/U    00/U    00/U    10/B    11/B    32/W
LVM 043/078 047/077 046/081 049/081 046/070 040/069 040/068
    00/B    30/U    00/U    01/N    22/W    23/W    52/W
HDN 044/080 051/080 047/084 050/084 049/074 044/072 045/071
    00/B    41/B    00/U    00/U    00/B    11/B    22/W
MLS 048/077 052/077 050/084 056/082 053/074 047/071 048/071
    00/U    44/W    00/U    00/U    00/B    21/B    32/W
4BQ 047/077 053/077 049/082 055/080 054/075 049/074 050/071
    00/U    41/B    00/U    00/U    00/U    21/B    42/W
BHK 043/072 048/076 046/083 051/080 050/076 044/072 045/071
    00/N    67/T    00/U    01/N    00/U    21/B    52/W
SHR 040/077 047/077 043/081 048/082 048/076 043/074 044/070
    00/U    41/U    00/U    00/U    01/U    12/W    33/W

&&

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

&&

$$
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