Helena, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

484
FXUS65 KTFX 042329
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
529 PM MDT Sat Jul 4 2026

Aviation Section Updated.

.KEY MESSAGES...

 - Warm, breezy, and generally dry through the rest of the
   afternoon.

 - Daily chances for showers and thunderstorms Sunday through
   Wednesday; a few may be strong to severe.

&&

.DISCUSSION...
/Issued 248 PM MDT Sat Jul 4 2026/

 - Meteorological Overview:

Breezy conditions will continue through the rest of the day before
tapering off towards the evening hours. A couple isolated showers
may try to form but nothing significant or impactful is expected
at least through the rest of Saturday.

Heading towards Sunday, a shortwave trough moving across the
region along with a shift to more southwesterly flow in Montana
will allow for more moisture and instability across the region
through the evening hours. Hi-res model guidance has the highest
shear across the northern half of our CWA but has the higher CAPE
values mismatched towards the southern portion of the CWA. Overall
the result of this setup will be a chance for showers and
thunderstorms across a good portion of the region but a higher
chance for strong to severe thunderstorms towards the middle
section of our CWA. The main threats with these thunderstorms will
be hail, strong wind, and heavy downpours.

For Monday and Tuesday, a shortwave trough riding along
southwesterly flow will bring ample moisture and instability to
the region allowing for showers and thunderstorms, especially
across Southwest Montana. The main threats will be hail, strong
winds, and heavy downpours. Model soundings indicate that
precipitable water values are going to be close to or potentially
above the daily climatological max. With this in mind, there will
some concerns for localized flooding, especially in urban and
poor-drainage areas and along burn scars with temporary rises in
creeks and streams possible.

Behind the trough some temporary shortwave ridging will build
allowing for temperatures to warm Tuesday into Wednesday across
the region. By Wednesday a Pacific trough starts to make its way
into the region bringing a chance for thunderstorms primarily
across the northern half of the CWA and a chance for severe
weather, especially east of a line between Chester and Great
Falls. The level of confidence in thunderstorms on Wednesday
afternoon remains similar to the previous forecast. With surface
temperatures across North-Central and Central Montana expected to
be in the upper 80s to low 90s and dewpoint temperatures expected
to be in the upper 50s to low 60s, that alone is usually enough to
cause some level of concern. The addition of the cold front is
then expected to provide the forcing needed to kick-start
thunderstorm activity across the northern half of the CWA.

The GFS continues to put out a more mellow version of events
across the region while the Euro has been more robust in the
coverage and intensity of thunderstorms. The Canadian has been a
little more selective in the coverage area compared to the Euro
but still suggests strong storms are possible over the eastern
half of the state. The two main things that introduce the highest
amount of uncertainty are the track and timing of the Pacific
trough. This is where the GFS, Euro, and Canadian all start to
diverge. Whether the trough ends up further south or north or what
time of day the cold front ends up arriving in our portion of the
state will all make huge differences in how the potential for
severe weather pans out. Ultimately it is still too early to have
a clear grasp on the finer details but it is something that will
be watched carefully in future forecasts. In the meantime, folks
should be prepared for the potential of strong to severe
thunderstorms on Wednesday afternoon, especially north of the
Highway 200 corridor.  -thor

&&

.AVIATION...
05/00Z TAF Period

Aside from some diurnal winds that will diminish over first couple
hours of the TAF period, the main concern over the next 24 hours
or so will be for thunderstorms Sunday afternoon across portions
of Southwest and Central MT. Gusty winds and hail will be the
primary concern with stronger thunderstorms. -AM

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  85  54  77 /   0   0  10  20
CTB  49  80  48  74 /   0   0   0   0
HLN  56  87  57  79 /   0  20  20  20
BZN  54  88  54  83 /   0  40  40  20
WYS  44  84  48  82 /   0  20  20  20
DLN  52  86  53  80 /   0  30  20  40
HVR  56  86  53  81 /   0   0  10   0
LWT  53  84  51  77 /   0  20  60  10

&&

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

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