183
FXUS65 KBYZ 311920
AFDBYZ

Area Forecast Discussion
National Weather Service Billings MT
120 PM MDT Thu Jul 31 2025

.KEY MESSAGES...

- Scattered thunderstorms today through Saturday. Strong to
  severe storms are possible. Locally heavy rainfall can be
  expected with storms.

- Thunderstorm and precipitation potential decrease from Saturday
  into next week.

- Seasonal temperatures for the next 7 to 10 days.

&&

.DISCUSSION...

Through Saturday night...

Unusual pattern for the end of July into early August with an
upper level ridge over the top of persistent low level east-
southeast flow. Usually by this time of the year the upper ridge
would mean mixed out dry southwest to west flow and maybe some dry
high based afternoon/evening thunderstorms. But this year we are
looking at the potential for very wet and potentially strong
thunderstorms as the upper ridge provides some capping for
discreet convection and the east-southeast winds pumps in plains
moisture and provides the shear for rotating updrafts to support
large hail and longer lived thunderstorms. This pattern continues
through tomorrow before the upper level pattern breaks down to a
weak zonal flow regime for the weekend. The zonal flow long with a
push of drier air from the PacNW desert areas will help to lower
PWATs over the area and produce a downward trend in Thunderstorm
intensity and coverage heading into early next week.

SPC has a marginal risk for severe thunderstorm for most of the
forecast area this afternoon, with a slight risk in the vicinity
of the Bighorn mountains. Thunderstorms get going over the
Beartooth mountains around 2pm and spread northeast into the
Billings and Sheridan areas by 6pm or so. Storm show
intensification in the models early evening from Sheridan county
northeast into Rosebud and Powder River counties before moving
into Fallon and Carter counties between 10pm and midnight.
Overall storm movement is going to be fairly slow and these storms
will have a lot of moisture to work with. The combination of slow
movement and heavy rainfall brings an increased threat for flash
flooding with any stronger storms through this evening. Coverage
of storms is the limiting factor for going with another Flash
Flood Watch today.

Storm potential tapes off around midnight, but doesn`t completely
go away especiall over SE Montana. There will also be the
potential for patchy fog in the hours around sunrise just about
everywhere.

A very similar thunderstorm set up develops for Friday afternoon
as a disturbance pushes in from the southwest and kicks off
convection over the western mountains mid afternoon, tracking
northeast through the evening hours. NCAR neural net forecast is
less clustered with severe potential compared to Thursdays progs,
but deterministic models are once again favoring areas from
Sheridan county across SE Montana for more robust thunderstorm
activity. Current SPC outlook for Friday has a marginal threat for
portions of SE Montana, but could see an expansion further
northeast as the new CAM guidance arrives. PWATs are a tad lower
for Friday, but still well above normal and supportive of heavy
downpours.

Saturdays convection looks to initiate south of the area and build
northward into the evening hours. So, a bit of a later start to
things compared to today and Friday. Looks like a few storms may
linger into the overnight hours across central and eastern zones.

Temperatures reach the mid 80s today, with more upper 80s for
Friday and Saturday (seasonal temperatures for this time of year).
Low temperatures will be mainly in the 60s each night, held up by
residual cloud cover and higher humidity levels. Chambers

Sunday through Friday...

As mentioned in the short term discussion, atmospheric moisture
levels (PWATs) should be on the downward trend from the end of the
weekend through next week. Most of this is due to the southeast
winds in the lower levels not being as persistent (becoming mainly
overnight low level jet induced) and with more consistency in
breaking the cap in the afternoon allowing drier downslope westerly
air to mix down to the surface. The result is a decrease in
precipitation potential and thunderstorm coverage as we go through
the extended period. That said there is a Pacific disturbance
that moves into the area Tuesday into Wednesday that could bring a
period of more organized thunderstorm development. Currently the
track being advertised is from southwest Montana into NC Montana
which puts our area on the drier side of the system. However, just
a slight track adjustment southward would bring better
precipitation potential than advertised in the going forecast.
Stay tuned.

Temperatures really aren`t too bad for this time of year with
highs in the upper 80s to lower 90s through the period, and lows
holding mainly in the lower 60s. Chambers

&&

.AVIATION...

VFR conditions will largely prevail throughout the period.
Isolated to scattered showers and thunderstorms are forecast for
all sites this afternoon and evening. Some storms may be strong
to severe, with hail as large as quarters, gusty and erratic
winds, and heavy rain. The chance for strong to severe storms is
greatest for KLVM, KBIL, and KSHR. Confidence is highest for
stronger storms at or near KSHR starting around 21z. Brief
reductions to flight categories will be possible with
thunderstorms. Matos

&&

.PRELIMINARY POINT TEMP/POPS...

    Fri     Sat     Sun     Mon     Tue     Wed     Thu
-----------------------------------------------------------
BIL 061/088 060/086 060/085 059/091 060/087 059/089 060/090
    33/T    43/T    44/T    21/U    22/W    11/U    10/U
LVM 052/085 051/084 050/084 051/088 051/084 051/086 052/089
    34/T    44/T    43/T    12/T    32/W    11/U    00/U
HDN 060/089 058/087 058/085 057/092 060/088 057/090 058/091
    42/T    53/T    44/T    21/U    22/W    11/U    10/U
MLS 063/086 062/086 061/084 060/090 062/087 059/089 062/089
    42/W    53/T    55/T    21/U    23/T    21/U    11/U
4BQ 062/085 062/085 061/081 059/087 062/087 060/089 062/089
    72/T    52/T    44/T    21/U    22/T    21/U    11/U
BHK 060/077 057/080 058/079 057/084 059/085 058/085 058/086
    44/T    52/T    55/T    31/U    23/T    31/U    21/U
SHR 055/086 054/084 054/081 053/089 057/087 054/089 056/089
    63/T    42/T    34/T    21/U    22/W    11/U    11/U

&&

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

&&

$$
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