964
FXUS65 KBYZ 181855
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
1255 PM MDT Sat Jul 18 2026

.KEY MESSAGES...

- Isolated to scattered thunderstorms this afternoon and evening.
  A few may be strong over the west and far southeast MT. Heavy
  rain, strong winds and hail are all threats.

- Marginal Risk (Level 1/4) of flash flooding over the
  Absaroka/Beartooths today.

- Daily chance of showers and thunderstorms through next week with
  high temperatures mainly in the 80s to upper 90s, warmest this
  weekend.

&&

.DISCUSSION...

Through Friday...

Upper ridging remains over the region today, with the axis
centered over eastern MT and an upper low slowly moving into
southern British Columbia. Water vapor satellite imagery shows
monsoonal moisture streaming into the region from the south once
again today. Moisture will be greatest this afternoon and evening
over the southern mountains and southeast MT, with PWATs
approaching or exceeding 1.50 inches. There are two areas of focus
for shower/thunderstorm development this afternoon. Convection
looks to build over the southern mountains this afternoon lifting
north and east through the late afternoon and early evening hours.
A weak wave will bring another round of convection to western
areas this evening, spreading west to east into central areas into
the late evening and overnight hours. A few strong storms are
possible over the west and southeast MT with modest instability
(CAPE values of 500-1500 J/kg). Deep layer shear is forecast to be
near 30 to 35 kts over southeast MT, with 20 to 30 kts of shear
over western areas. Very heavy rainfall, strong winds and hail are
possible with the strongest storms. SPC has a marginal risk for
severe weather for areas along and west of Roundup to Livingston
line, though as mentioned, there could be a few stronger storms
over southeast MT as well, and latest hi-res guidance does show a
couple stronger helicity tracks there. There remains a marginal
risk for excessive rainfall over the Beartooth/Absaroka mountains
through the evening.

A weak upper low sliding east through southern Canada flattens
the ridging even more for Sunday and Monday, with a weak front
moving through the area on Sunday and a backdoor front for Monday.
The majority of the convection looks to remain confined to
southern areas on Sunday, as the combination of some weak jet
energy, falling heights and a weak frontal passage allow
thunderstorms to form over the mountains/foothills and move west
to east during the afternoon and early evening. Some thunderstorms
could be strong to severe with modest instability and shear in
place. SPC has a marginal risk for severe thunderstorms Sunday
afternoon and evening from Billings and areas east. Monday looks
to be mostly dry, as monsoonal moisture is pushed south of the
region. As flow becomes more westerly, smoke from wildfires over
Washington and Oregon may start to filter into the region by
Monday.

Ensembles remain in good agreement heading towards the middle of
next week in a return of ridging to the region, as well as an
increase in monsoonal moisture. This will keep a daily chance for
showers and thunderstorms in the forecast, with near to slightly
above normal temperatures. High temperatures are forecast to range
from the upper 80s to 90s most days, with some locations
approaching 100 degrees over the east on Saturday and Sunday. STP

.AVIATION...

Isolated to scattered showers and thunderstorms will develop off
the higher terrain across south central MT and northern WY this
afternoon, mainly affecting KSHR from 21Z-04Z. An additional wave
of thunderstorms will move in from the west to east early in the
evening (~01-04Z) at KLVM. Currently, KBIL has about a 10% chance
for a thunderstorm from 20Z-01Z today, but confidence is slightly
higher for thunderstorms late in the evening. Main threats with
these thunderstorms will be heavy rain, gusty winds and small
hail. TS

&&

.PRELIMINARY POINT TEMP/POPS...

    Sun     Mon     Tue     Wed     Thu     Fri     Sat
-----------------------------------------------------------
BIL 067/097 066/091 065/090 066/093 068/091 066/098 068/099
    22/T    20/U    00/B    11/B    33/T    21/U    31/U
LVM 057/095 056/093 056/091 057/091 058/090 057/095 058/095
    22/T    20/U    01/B    24/T    65/T    33/T    32/T
HDN 064/097 063/092 062/091 063/094 065/092 064/099 066/100
    22/T    20/U    00/B    21/B    32/T    31/U    31/U
MLS 067/098 066/091 063/088 064/094 067/094 067/101 070/102
    21/U    20/U    00/B    11/B    22/W    21/G    21/G
4BQ 067/098 066/091 063/088 064/092 066/091 065/097 068/100
    31/U    20/U    00/B    21/B    43/T    21/U    21/U
BHK 063/098 062/090 058/086 058/091 061/092 062/098 065/101
    21/U    20/N    00/B    11/B    12/W    21/U    21/G
SHR 060/094 060/091 058/091 059/091 060/087 059/095 062/096
    32/T    20/U    01/B    24/T    57/T    22/T    22/T

&&

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

&&

$$
weather.gov/billings