Helena Valley West Central, MT 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

334
FXUS65 KTFX 250231
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
831 PM MDT Sun May 24 2026

.KEY MESSAGES...

 - Warm, breezy and mostly dry conditions for much of the region
   today, with some isolated showers and thunderstorms possible in
   Southwest MT this afternoon.

 - Monday through Friday will see daily chances for showers and
   thunderstorms in the afternoon and evening hours. Some of
   these storms could be strong to severe.

 - Warm temperatures will continue through Tuesday, with a brief
   cool down Wednesday and Thursday.

&&

.UPDATE...

Satellite imagery shows areas of mainly high clouds streaming
across the Northern Rockies and MT this evening with the exception
of some dissipating cumulus buildup and isolated showers across
far SW MT. Dry and mild conditions will prevail tonight with
generally light winds. Did add some patchy smoke to parts of far
southwest Lewis and Clark/Jefferson counties overnight with active
burning noted on satellite and webcams at the Jericho Creek fire.
For tomorrow, flow aloft turns southwesterly and begins to import
some initially mid-upper level moisture into the region for
isolated to widely scattered afternoon thunderstorm development
that tracks north through the region into the evening. These will
be high-based showers/thunderstorms with an environment favorable
for gusty winds but minimal precipitation. Hoenisch

&&

.DISCUSSION...
/Issued 548 PM MDT Sun May 24 2026/

 - Meteorological Overview:

Due to zonal flow aloft, today will be warm, breezy and mostly
dry across the region, with the exception of a few showers and
weak thunderstorms possible in Southwest MT this afternoon.
Tomorrow, an upper-level trough begins to move inland from the
west coast, bringing widespread chances for showers and
thunderstorms. The upper level trough will transition the zonal
flow to southwesterly flow, advecting warm air into Montana. This
warm air advection, combined with upper level ridging to the east,
will make for the warmest day of the week for most of the region,
with highs in the 80s to low 90s. The warm temperatures will last
through Tuesday, before a cold front Tuesday night will bring a
brief cool down Wednesday and Thursday.

On Tuesday, the axis of the upper level trough moves southeast
down western Oregon and and northern California, resulting in
southeasterly flow into the region. The trough settles into a spin
over California and Nevada Wednesday and Thursday, creating a
shift to a more steep southerly flow. On Friday, the trough begins
to break down and the axis moves northeast towards Montana,
putting the region back into southeasterly flow.

With the daily influence of this trough spinning to the southwest
of Montana comes an ushering of moist and unstable air into the
region each day. Combined with the warm afternoon temperatures,
there is a daily chance for showers and thunderstorms through the
rest of the approaching work week. Some of these storms could be
strong to severe, depending on the position of the trough and the
timing of the moisture each day. See the "Forecast Confidence &
Scenarios" section for more details. -Dzomba




 - Forecast Confidence & Scenarios:


Monday Thunderstorms:

Overall, these showers and thunderstorms look relatively mild
compared to what is expected later in the week. With CAPE
generally expected to stay below 1000 J/kg, there is not a lot to
work with. Some isolated instances of strong, gusty winds are
certainly possible across Southwest Montana but nothing reaching
the level of concern compared to what arrives later in the week.


Tuesday Thunderstorms:

One of the limiting factors on Tuesday will be moisture. The 00Z
run of the GFS has continued the trend of pushing back the timing
for when the moist air gets pulled up into Central Montana. The
Euro still has dewpoints getting close to 50 degrees starting at
around 6 PM. Either way, the trend is that the moist air is not
expected to arrive until much later in the day than what would
normally be favorable for severe weather.

This not to say that severe weather is not possible. With highs
across the Northern Plains in the mid 80s to mid 90s, there is
still a potential for isolated, strong, diurnally-driven
convection. Because moisture is going to be lacking, especially in
the early afternoon hours, the main concern will be dry
downbursts which could produce isolated instances of strong winds.

All things considered, the timing of the moisture will determine
the dynamics of the afternoon. If the moisture is able to arrive
earlier in the day, the chances for stronger convection increases.
However, if the current trend of the GFS pushes the arrival
further into the evening/overnight hours, then the threat lessens
significantly. Despite only being a couple days out, there is
still uncertainty as to how Tuesday will play out.

 through Friday.
Wednesday Thunderstorms:

By Wednesday, moist air is expected to filter into Central and
North- Central Montana with the latest Euro pushing afternoon
dewpoints into the low to mid 60s across the Northern Plains. The
current areas of concern are focused more on Central Montana,
particularly around Judith Basin, Fergus, Chouteau, Hill, and
Blaine counties. The latest model runs continue to show a modest
1000-1500 J/kg CAPE across the region. The limiting factor on
Wednesday will be how warm temperatures get. Right now, east of a
line between Havre and Lewistown, highs in the upper 70s to mid
80s are expected, with locations to the west of that line only
reaching the low to mid 70s. Widespread cloud cover throughout the
day is possible, which could further limit afternoon instability.

Simply put, it is not unreasonable for a couple of the storms on
Wednesday to be near-severe or severe. However, right now there is
too much uncertainty in the morning setup to make any
deterministic calls on how widespread or significant the threat
will be.


Thursday and Friday Thunderstorms:

While there is still a bit of uncertainty as to exactly how this
upper level trough will set up across the western CONUS, there is
increasing confidence with the latest model runs that both
Thursday and Friday will be widespread thunderstorm days. As of
now, the Euro is a lot more generous with CAPE than the GFS on
both days. The Canadian opted more for a confined area of higher
CAPE across the central third of the CWA on Thursday, roughly
between Great Falls and Bozeman. On Friday, the Canadian shows
higher CAPE values in the northern half of the CWA. -thor and
Dzomba


&&

.AVIATION...
25/00Z TAF Period

VFR conditions will prevail through the period. There is a chance
for showers and thunderstorms to develop Monday afternoon along
the Continental Divide and across Southwest Montana. Coverage is
expected to remain isolated but periods of mountain obscuration
are possible after 25/18Z. Any thunderstorm that develops is
expected to be on the drier side, so the main concerns will be
lightning and gusty, erratic winds.   -thor

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  48  88  56  88 /   0   0  10  50
CTB  45  85  52  84 /   0   0  10  50
HLN  47  85  51  84 /   0  10  20  40
BZN  44  84  48  83 /   0  10  30  60
WYS  33  78  39  75 /  20  20  10  60
DLN  43  81  46  79 /   0  20  30  40
HVR  49  91  58  96 /   0   0  10  10
LWT  46  85  53  88 /   0   0   0  10

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$
http://www.weather.gov/greatfalls