Kirby, Montana Weather Forecast Discussion

704
FXUS65 KBYZ 100824
AFDBYZ
Area Forecast Discussion
National Weather Service Billings MT
224 AM MDT Wed Sep 10 2025
.KEY MESSAGES...
- Above normal temperatures through Thursday.
- Daily chance of showers and thunderstorms over portions of the
  area through Thursday, best over the mountains and foothills.
- Good chance of more significant precipitation in east (40-70%
  chance >0.5in) and cooler temps Friday into Sunday.
&&
.DISCUSSION...
Through Thursday night...
Satellite imagery exhibited our current synoptic pattern with an
upper ridge axis over eastern Montana and the high plains, while a
large upper low sat over the northern Calif/Oregon area. As the
western CONUS upper low gradually slides east into the Rockies, we
will see increasingly diffluent mid level flow across our western
and central zones...with associated disturbances tracking across
our CWA as well. Our eastern zones will see low level flow turn
strongly to the southeast and advect in higher low level moisture
with PWAT values get to around 150% of normal from Rosebud County
eastward by this afternoon. The corresponding MUCAPE values reach
1500-2000 J/kg over our far eastern zones (Custer, Fallon,
Carter).
So we continue to look for isolated to scattered showers/thunder
over the western half of the CWA where forcing and upper dynamics
are best...while the east only sees isolated activity despite the
significant MUCAPE, as forcing may be limited. Any activity that
develops in the east could become strong to severe, but with less
forcing and weak shear our confidence is low. Plus, soundings show
a weak cap through the afternoon where the CAPE is highest, and by
the time the cap breaks it may be after dark when lapse rates
begin to shrink. We may see isolated convective showers linger
overnight. as they drift north/northeast.
By Thursday...the upper low will be over the Great Basin in Nevada
with strong diffluent dynamics and Pacific moisture feed into our
central and west, while monsoonal moisture and impulses work up
into the southeast corner. The deterministic GFS shows a strong
Pacific front pushing west to east across our area by evening with
associated convection developing. This may produce some gusty
northwest winds (25-40 mph) winds behind the front. Again, high
MUCAPE in the far east may go un-used as darkness may fall before
convection is initiated in the far eastern zones...but we cannot
rule it out all together. Most of the convective activity will
lift to our north/northeast overnight.
Highs today will be in the 80s to lower 90s, nearly 10-15 degrees
above normal. Highs on Thursday will be affected by the dynamic
nature of the weather system moving at us, with readings ranging
from upper 70s west to near 90 east. Overnight lows will be in
the upper 40s and 50s.
Wildfire smoke...Southerly flow will increase over the region
with the approaching upper low and push wildfire smoke to the
north of our region today through at least Thursday. BT
Friday through Tuesday...
By the end of the week, a low pressure system is expected to move
into western MT. Cooler conditions and increased chances for
precipitation will be in play through the weekend. Ensembles and
models have trended downward over the past few days on
precipitation totals as models have trended towards a more
northerly track of the low. Currently, areas Billings eastward
have about a 40-70% chance of at least half an inch of
precipitation Friday through Sunday. Areas of Rosebud Co. east
have about a 40-50% chance of getting at least an inch. There is
still a lot of spread or range of rainfall totals, mainly for
southeastern MT, allowing for some uncertainty to remain. With
some instability remaining into Friday (MUCAPE ~ 600-800 J/kg),
isolated to scattered thunderstorms are expected if there is
forcing in place (dependent on where the low tracks). Ensembles
are then bringing in a shortwave low right behind for late
Monday/Tuesday time frame, continuing the unsettled pattern.
High temperatures will be in the 70s to low 80s Friday, cooling
into the upper 60s and 70s Saturday. Temperatures will remain in
the 70s for the remainder of the period. TS
&&
.AVIATION...
Isolated showers over south central MT and northern WY are
expected to dissipate through the morning. A low level jet
overnight could bring minor low level wind shear to KMLS (about
25 kts at 1500 ft AGL). Wildfire smoke will continue to reduce
slant range visibility through the morning. Smoke is expected to
gradually clear through the day today. Scattered showers and
thunderstorms will begin to develop off the Beartooth/Absarokas
this afternoon with the main threat being gusty winds of 30-40
kts. TS
&&
.PRELIMINARY POINT TEMP/POPS...
Tdy Thu     Fri     Sat     Sun     Mon     Tue
-------------------------------------------------------
BIL 087 060/083 054/081 055/074 054/076 053/079 054/075
    0/H 15/T    33/W    56/T    32/W    12/W    34/W
LVM 084 051/078 044/075 044/072 044/074 044/076 045/073
    2/T 27/T    34/T    45/T    33/W    23/T    34/T
HDN 090 056/086 050/083 052/074 051/076 049/080 051/077
    1/H 12/T    33/W    76/T    52/W    11/U    33/W
MLS 091 061/089 056/084 056/073 054/075 053/080 054/077
    2/H 11/B    32/W    77/T    63/W    22/U    22/W
4BQ 089 063/090 057/083 056/071 053/074 052/079 054/076
    2/H 11/B    22/T    76/T    52/W    11/U    22/W
BHK 087 059/090 054/083 054/073 051/075 050/078 051/077
    2/N 11/B    31/B    77/T    63/T    21/U    22/W
SHR 090 054/085 049/081 048/070 045/075 046/080 048/075
    1/B 12/W    24/T    77/T    42/W    12/U    34/W
&&
.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...None.
WY...None.
&&
$$
weather.gov/billings

NWS BYZ Office Area Forecast Discussion