Kirby, Montana Weather Forecast Discussion

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FXUS65 KBYZ 160150
AFDBYZ
Area Forecast Discussion
National Weather Service Billings MT
750 PM MDT Mon Sep 15 2025
.KEY MESSAGES...
- Persistent chances for showers and thunderstorms through
  Tuesday. 10-50% chance of receiving greater than 0.5 inches of
  additional rain.
- Light snow accumulations in the Beartooth Mountains above 10kft
  tonight through Wednesday morning. May impact travel over the
  highest elevations along the Beartooth Highway.
- Becoming drier with seasonal temperatures for the end of the
  work week. Above normal temperatures for the weekend.
&&
.UPDATE...
Upper low continues to evolve slowly over northwest WY. There is
an area of strong-ish thunderstorms lifting thru the far southeast
corner of MT, otherwise strongest ascent and main axis of showers
as of 0140z is draped across our north from west to east (i.e.
Harlowton to Baker). Mid level W-NW winds are providing some
downslope to the south of this area. Over time tonight, the low
will pivot such that a component of dry-slotting will impact
southeast MT while backside precip associated with a developing
trowal will be focused over our west and north central parts, and
there will begin to be upslope enhancement along the north aspects
of the Beartooth-Absarokas as winds shift northerly. Have made
some pop/wx/QPF adjustments to align with these trends over the
next 12-18 hours. As far as high elevation snow is concerned,
latest mesoanalysis shows freezing levels over our west at ~11kft
currently, and this seems consistent w/ current temp of 37F at
Quad Creek Raws (elev. 9774 above Vista Pt). So once the trowal
precip begins in the western mountains later tonight we will be
seeing wet snow above 10-11kft. A Winter Weather Advisory is in
effect for the Beartooth Highway. JKL
&&
.DISCUSSION...
A 500 mb Pacific trough will drop down to our west over the next
few days. This will put the region in a favorable deformation zone
today bringing precipitation chances of 40-60% across the region.
CAPE values 58 mph the
main threat with these storms. Models are indicating that
convection could continue through the overnight hours.
Upper level flow out of the southwest today will transition to
northeasterly flow Tuesday as moisture wraps around the system.
Models are showing a band of precipitation setting up over
southeast Montana. There is a lot of uncertainty as to where this
band will set up leading to a wide range of potential
precipitation amounts. Overall, today through Tuesday, most
locations have a 40-50% chance of getting greater than 0.5 inches
of precipitation with lower chances near the Dakotas border. Cool
700 mb temperatures near 0C and upslope flow with Tuesdays band of
precipitation will lead to snowfall above 10,000 ft. Accumulations
are expected to be in the 1-3 inch range. This has the potential
to impact travel on the Beartooth pass.
High temperatures Wednesday are expected to be in the mid 60s to
mid 70s F.
Continued upper level troughing over the northern plains will keep
weak low pressure over the central and northern plains Wednesday
through Friday. This will continue to wrap moisture into Montana
keeping PWAT values 100-150% of normal. The low pressure and
moisture plume will drift to the east diminishing precipitation
chances every day. Wednesday will see locations south of a line
from Red Lodge to Miles City have a 20-50% chance for
precipitation. Thursday, Carter and Fallon Counties have a 20%
chance for precipitation decreasing to 

NWS BYZ Office Area Forecast Discussion