304
FXUS65 KBYZ 171030
AFDBYZ

Area Forecast Discussion...Updated
National Weather Service Billings MT
430 AM MDT Mon Aug 17 2026

.KEY MESSAGES...

- Marginal Risk for severe storms over central MT today; strong
  winds are the primary threat.

- Scattered showers and thunderstorms expected through Tuesday.
  Drier for last half of week.

- Seasonal temps in the 80s through most midweek, pushing into
  the lower 90s by late week.

&&

.UPDATE...

The Storm Predicition Center has introduced a Marginal Risk (1/5)
for severe thunderstorms over central MT today. The main concern
with any storms will be strong wind gusts up to 65 mph. Heavy rain
and hail are secondary concerns. The timing of any strong to
severe thunderstorms looks to occur between 2 and 9 PM MDT. The
rest of the forecast remains in good shape. Stay weather aware
today. Matos

&&

.DISCUSSION...

Today through Sunday...

The shortwave moving through the area now will be the last of the
weak waves we have seen over the past several days. Starting today
we will shift to a slightly different regime, however the chance
for showers and storms will stick around a little bit longer.
Later today a lobe of energy will eject off of the upper level
low centered over the Hudson Bay. This will drift southwards into
the high plains giving most of the CWA a shot at precipitation
this evening into Tuesday.

Storms will kick off of the mountains mid-to late afternoon just
as that area of broad scale ascent moves into the region. Storms
should be able to initiate fairly easily in this region of CVA
due to the enhancement of the mountains as well as the lack of
any CIN due to sufficient daytime heating. SB and ML CAPE values
are both not anything to write home about, however widespread
500-1000 J/Kg will be plenty to sustain these storms in
conjunction with the modest 7-8 C/Km mid-level lapse rates.
Moisture content should be fairly similar to today. The question
here will be whether or not the surface winds will be able to
return to easterly early enough today to support decent moisture
advection prior to convective initiation. Regardless, it does
look like these storms will be decently high based which would
result in a downburst / gusty wind threat. The HREF ensemble is
suggesting 0-6 Km shear may be widespread over 40 kts with
pockets of 50 kts. While I do think this may be a touch overdone,
this suggests that the environment will be supportive of isolated
supercell development amongst the scattered thunderstorms. The
main limiting factor in terms of hail development is the lack of
CAPE and how skinny the profile is. That being said, the shear in
the hail growth zone is very supportive of tilted storms and
hydrometer size sorting. In short, strong winds will be the main
threat this afternoon and evening with the potential for some
large hail in the strongest storm or two.

After the initial vort max, a couple more push through our region
is quick succession Monday night through Tuesday evening which
will allow for continuous chances for showers and thunderstorms.
While strong storms are less likely on Tuesday, the threat for
heavy rain may go up as the atmosphere gets progressively more
saturated throughout the event.

Wednesday will be a transition day as the upper level low moves off
to the east. Showers will probably be hanging around the area
Wednesday morning and gradually diminish / move east as the day
goes on. By Wednesday night a rige will be in place over the
intermountain region which will keep most of the CWA warm and
dry. As weak vort maxes ride along the ridge mid to late week, there
could be widely isolated showers in the eastern 2/3 of the CWA any
given day. This pattern will continue into the weekend as temps
slowly increase each day. There is still a difference between the
GFS and ECMWF ensembles in terms of highs for this weekend as the
GFS wants to have us flirt with triple digits again Saturday
whereas the ECMWF keeps highs in the low 90s.

The ridge should not stick around too long though as models hint
at it only lasting into the weekend. The potential for a trough to
move off of the BC coast and track just north of the
international border is possible. For anyone who is looking
forward to the next season, this seems to have a hint of an Autumn
flavor to it in terms of location and progression. WMR

.AVIATION...

Scattered showers and thunderstorms are expected to develop across
the region this afternoon and evening. A few storms could be
strong to severe over central MT, capable of producing strong wind
gusts to 55 knots and heavy rainfall. The risk for stronger storms
exists north of KBIL but all terminals may be impacted by showers
and thunderstorms late this afternoon. Potential TS times are
listed below:

KLVM: 21-04z
KBIL: 23-05z
KMLS: 00-06z
KSHR: 21-06z

Matos
&&

.PRELIMINARY POINT TEMP/POPS...

    Tdy Tue     Wed     Thu     Fri     Sat     Sun
-------------------------------------------------------
BIL 084 059/081 058/085 059/089 062/090 064/090 063/088
    1/B 33/T    40/U    00/U    00/B    22/T    42/W
LVM 082 050/080 046/084 050/088 054/090 056/088 053/084
    1/B 44/T    40/U    00/U    01/B    24/T    52/T
HDN 087 056/084 054/088 054/091 057/093 061/094 061/090
    1/B 33/B    30/U    00/U    00/B    11/B    31/B
MLS 085 058/083 057/087 058/091 061/090 062/091 064/090
    1/B 53/T    41/U    00/U    00/B    01/B    31/B
4BQ 086 059/082 057/086 058/090 061/091 063/091 064/090
    1/B 32/T    51/U    00/U    00/B    11/B    41/B
BHK 085 053/082 052/085 055/090 056/088 057/088 059/090
    1/B 52/B    32/T    10/U    00/U    01/B    32/W
SHR 083 054/079 050/083 051/088 055/091 057/090 058/088
    3/B 34/T    41/U    00/U    00/U    12/T    23/T

&&

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

&&

$$
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