Hysham, Montana Weather Forecast Discussion

379
FXUS65 KBYZ 060725
AFDBYZ
Area Forecast Discussion
National Weather Service Billings MT
125 AM MDT Mon Oct 6 2025
.KEY MESSAGES...
- Chilly with localized fog early this morning.
- Building high pressure aloft brings dry and warmer weather
  through Friday.
- Next reasonable chance of precipitation is the weekend.
&&
.DISCUSSION...
Today through Tuesday Night...
Upper trof dropping slowly thru WY continues to bring some very
light precip to our south as of 07z, mainly over the Bighorns, but
some light showers may eke into far southern Powder River/Carter
before it exits entirely. Once we get past ~15z, dry conditions
will persist through the remainder of the period as high pressure
builds over the region. There is a low risk (20%) of localized
valley fog early this morning. Existing cloud cover is preventing
temps from dropping too quickly but skies are mostly clear in the
far east, and we are starting to see breaks along portions of the
western foothills. Dew point spreads are quite low at this hour
(4F or less) so fully expect there to be some fog by sunrise.
Something to monitor.
07z temperatures are in the 30s to lower 40s. Again depending on
cloud cover, a good portion of the region should be in frost or
freeze territory by daybreak. For many locations this will be the
chilliest morning seen so far this fall, which says more about the
warm early fall than the coolness of this air mass.
Expect high temperatures in the 50s today and 60s Tuesday as the
ridge brings persistent downslope warming. Frost and freeze
potential will be more localized tonight due the downslope
gradients and warm advection. Lows will reach the upper 20s to
lower 40s, coolest in sheltered valleys. Tuesday night will be
milder yet.
When skies clear be sure to check out the snow-topped mountains.
JKL
Wednesday through Monday...
There is now good agreement that the cutoff upper level low
pressure system off the west coast will lead to increased heights
across Montana. This will create temperatures around 5 degrees
above average Wednesday and Thursday (70 F) before increasing to 5
to 15 degrees above average Friday and Saturday (70-80 F).
There is good ensemble agreement that an upper level trough will
drop into the region next weekend and bring a pattern change to
wetter and cooler conditions. Precipitation chances return
Saturday and last through Monday. Currently, the NBM is giving a
30-70% chance for getting greater than 0.25 inches of
precipitation across the region. Given how far out this system is,
it is difficult to provide further details at this time. Torgerson
.AVIATION...
Scattered light rain/snow showers near KSHR and the Bighorns will
taper off by 12-14z. There remain areas of low clouds with local
MVFR ceilings along the western foothills (near KLVM, K6S0 &
KHWQ) which will diminish slowly through the early morning. Also,
depending on where and when skies clear over the next few hours,
localized valley fog or low clouds are possible until ~15z. Fog
development is of low confidence at this time (

NWS BYZ Office Area Forecast Discussion