499
FXUS65 KBYZ 040830
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
230 AM MDT Mon Aug 4 2025

.KEY MESSAGES...

- A better chance of thunderstorms late today, a few could be
  strong to severe storms with damaging wind the main threat.

- Seasonal temperatures in the upper 80s to lower 90s and mainly
  dry Tuesday through Thursday.

- Much cooler (highs in the 70s) and unsettled conditions
  developing Friday into the weekend.

&&

.DISCUSSION...

Through Tuesday night...

Pacific NW weather system will be moving into the Rockies (Idaho)
today with southwest flow across our region. This will induce
easterly low level winds over the eastern plains of Montana
and increase our moisture compared to yesterday, as well as
increase directional shear (sw flow over east flow). Models
suggest some energy ejecting out ahead of main trough will track
across central Montana pushing a frontal boundary across our CWA.
CAMS suggest convective initiation in the west around 2pm, with
increasing coverage and intensity as convection shifts east.
Timing brings it into Yellowstone County around 6 pm...and
propagates east through the evening potentially becoming a line of
storms extending from northeast Montana as far south as Ashland.
Most of this pushes east after midnight, but cannot rule out some
additional isolated convection from Wheatland County eastward
over east central Montana as energy continues to eject from the
bottom of trough which will be moving into west central Montana
overnight. While we cannot rule out hail late today into the
evening, strong winds and locally heavy rainfall (from Billings
east) will be the main threats with storms.

The main upper trough will track E/NE across northern Montana
Tuesday. The best forcing will remain north of our CWA, but we
could see isolated to scattered showers/storms along our northern
zones through the day. Downslope flow in the mid-levels will
prevail over our area by Tuesday evening once the trough axis
scoots by to the north, leading to a dry and less active evening.

Being a pre-frontal day, high temperatures will be a few degrees
warmer today, mainly in the lower 90s ahead of thunderstorms.
Lows tonight will range from upper 40s over the western
foothills to lower 60s near the Dakota borders. Highs Tuesday will
be 5-7 degrees cooler, in the 80s. BT

Wednesday through Monday...

Thursday will see heights start to lower across Montana as a
Pacific trough moves into the region. Deterministic models are
currently indicating a frontal passage Thursday evening. Easterly
winds are expected to advect in moisture from the plains bringing
widespread PWAT values of greater than one inch. The ECMWF
Ensemble is indicating anomalously high CAPE values for Thursday
and Friday leading to favorable conditions for thunderstorms. It
is to early to determine the potential severity of any storms.
Deterministic models are indicating the potential for dry slotting
over the region Thursday night into Friday morning decreasing
precipitation chances, though the NBM isn`t yet showing this.
Ensemble systems are indicating continued precipitation chances
Friday and Saturday, though there is more uncertainty in how long
precipitation chances will continue. 45% of WPC clusters are
showing a more positively tilted trough and higher precipitation
values and the other 55% of models indicating a more neutral
trough and lower precipitation values for Saturday. Currently, the
heaviest precipitation is expected in more northern parts of
Montana though this is subject change.

The cold front Thursday evening will bring persistent northwest
winds advecting cooler temperatures Friday through the weekend.
Saturday looks to be the coolest with temperatures in the 70s F
for most (10-15 degrees below normal). Sunday and Monday are
expected to see rebounding temperatures back into the 80s F as
the upper level trough moves to the east. Torgerson

&&

.AVIATION...

Isolated showers and thunderstorms are expected to initiate over
the higher terrain/mountains of south central MT after 21Z and
increase in coverage into the evening as a weather system tracks
over the region. Scattered to numerous showers/storms are expected
across east central MT in the evening...tracking eastward through
08Z. Storms may produce hail and isolated wind gusts 40-50kts
along with brief MVFR in heavy rainfall. KBIL-KRPX-KMLS have the
greatest chance of significant impacts (30-60%). BT
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Tue     Wed     Thu     Fri     Sat     Sun
-------------------------------------------------------
BIL 092 060/085 059/090 062/088 060/076 054/079 056/083
    3/W 30/U    00/U    11/B    44/T    21/B    10/U
LVM 087 048/082 049/088 052/085 049/074 045/078 048/082
    3/T 31/U    00/U    12/T    54/T    21/U    00/U
HDN 094 059/086 056/091 060/091 058/078 052/079 053/085
    1/U 40/U    00/U    11/B    44/T    31/B    10/U
MLS 093 065/085 059/091 063/091 061/078 056/077 055/082
    0/U 62/T    00/U    11/B    54/T    32/W    10/B
4BQ 091 063/085 060/092 064/093 062/078 056/077 055/081
    0/U 41/U    00/U    11/U    33/T    42/T    10/B
BHK 090 063/085 057/089 061/090 058/077 053/076 053/080
    0/U 43/T    10/U    22/T    43/T    32/W    10/B
SHR 090 055/085 054/091 058/091 056/077 048/077 050/081
    1/U 20/U    00/U    01/U    23/T    32/T    11/B

&&

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

&&

$$
weather.gov/billings