729
FXUS65 KBYZ 011040
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
440 AM MDT Tue Jul 1 2025

.KEY MESSAGES...

- Turning quite warm this week with many locations in the 90s
  today through Thursday. Up to 70% chance of a few triple digits
  Wednesday (Forsyth/Miles City).

- Increasing chance for late day showers and thunderstorms the
  rest of the week.

- Cooler temperatures with a continued chance for precipitation
  for the holiday weekend.


&&

.DISCUSSION...

Today through Wednesday night...

Strong ridging over the region will continue today and warmer
temperature. Highs today are expected to be in the upper 80s to
lower 90s. Upper low off the Calif coast will result in a weak
southerly flow in the mid levels (monsoonal in nature) and advect
some moisture and weak impulse energy into our southwest. So look
for some isolated to scattered showers/thundershowers over and
near the Beartooths/Absaroka Ranges late today through the early
evening. Some of this could try to spill over to the nearby plains
in the evening, but we do not see much dynamics to support deep
convection, so it may just be some light showers of sprinkles if
and when it reaches even as far east as Billings before
dissipating overnight. Convection is expected to be relatively
high based, with isolated strong wind gusts the main threat. There
is also a small chance (10-15%) for thunderstorms in Fallon and
Carter Counties along the Dakota border today, forming within a
convergence zone/inverted surface trough. If something does
develop, it may be capable of strong winds and some hail.
Overnight lows tonight will be on the warmer side with 50s to mid
60s common.

Even warmer afternoon conditions are expected Wednesday with
highs pushing well into the 90s to near 100 degrees. The chance
of seeing 100 degrees ranges from 25-65% over and near the river
valleys from Treasure, Rosebud and into Custer County. Specifically,
about 65% chance of 100 or greater at Miles City on Wednesday.
The ridge axis aloft will shift a bit east allowing for a better
mid level moisture fetch from the S/SW, while southeast low level
flow brings in higher dewpoints over the plains. We do anticipate
an increased coverage of showers/storms. Convection will initiate
over the higher terrain in the afternoon and propagate east
through the evening. MUCAPE will range from 750-1200 J/kg with the
highest values along the Dakota border. Effective shear progged
to be 30-40 Kts may support a few strong storms with strong wind
gusts and small hail.

Impacts note...We have issued a Heat Advisory valid Wednesday for
Treaure, Rosebud and Custer Counties. Keep in mind, this area
represents where the highest heat risk values are located, but
all areas across the lower elevations will be well above normal.
Those with outdoor activities should be thinking about heat safety
precautions as the warmest temperatures (and heat indices) of the
season are expected at midweek. BT


Thursday through Sunday...

The upper level ridge will be squarely over the region by
Thursday. This will allow for continued hot temperatures in the
mid to upper 90s, with localized 100F temps toward Miles City.
Despite the ridge being in place, there will be mid level
moisture advection from the southwest (Monsoon), and low level
moisture advection from the southeast. In short, its going to be
hot and moist (PWATs ~1.0 inches) with 30 to 60 percent chances
for afternoon/evening showers and thunderstorms across the
forecast area Thursday afternoon.

A more substantial trough moves in from the PNW on Friday
knocking temperatures back into the low to mid 80s. The cold front
and cooler mid level air will increase instability and lift over
the area continuing the chance (30-60 percent) for showers and
thunderstorms. PWAT values, however, will be slightly lower Friday
meaning that there is less of a chance of heavy rainfall in these
storms. Seasonal temperatures with afternoon and evening shower
and thunderstorm chances continue through the weekend.

Regarding the mid to late week heat: While temperatures will be
well into the 90s with even a few triple digits, the forecast
temperatures are not unusual for this time of year, which is
generally the warmest time of year for the northern Rockies. The
latest Extreme Forecast Index shows low temperatures only getting
into the 60-70th percentile (mid 60s to low 70s F). That said,
the combination of heat and humidity is starting to register on
the Heat Risk forecast. Those with outdoor activities (recreation
or work) should be thinking about heat safety precautions as the
warmest temperatures (and heat indices) of the season arrive this
week. Chambers/WMR

&&

.AVIATION...

VFR conditions will prevail across the region through 22Z.
Towards the end of the period some isolated thunderstorms start to
form over the mountains which could push their way into
KLVM/K6S0/KSHR after 22Z. Any of these storms that move off of the
mountains could briefly impact a terminal with heavy rain and
gusty winds up to 40kts (30% chance). KBIL has a less than 20%
chance that a storm will impact the terminal and should remain VFR
for the entire period. Mountains will be partially obscured after
20z. WMR

&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Wed     Thu     Fri     Sat     Sun     Mon
-------------------------------------------------------
BIL 094 064/096 064/090 062/084 058/081 056/084 057/086
    1/U 21/B    22/T    45/T    53/T    22/T    22/T
LVM 092 056/091 056/086 053/082 048/079 048/082 050/084
    2/T 23/T    35/T    57/T    64/T    32/T    22/T
HDN 095 062/098 062/092 061/087 058/082 055/085 056/087
    0/U 11/U    22/T    54/T    53/T    32/T    21/U
MLS 095 065/100 067/095 066/088 061/083 057/085 060/086
    0/U 01/U    31/E    53/T    53/W    32/T    31/U
4BQ 095 064/095 068/092 065/085 060/082 058/083 060/085
    0/U 10/U    21/B    53/T    42/T    32/T    31/U
BHK 090 060/092 065/093 062/085 057/078 054/080 056/083
    2/T 20/U    22/T    52/T    43/T    32/T    32/T
SHR 093 059/094 060/087 057/084 053/081 051/083 053/085
    1/U 21/B    24/T    55/T    43/T    22/T    22/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...Heat Advisory in effect from 9 AM to 9 PM MDT Wednesday FOR
      ZONES 30>32-173.
WY...None.

&&

$$
weather.gov/billings