Helena Valley West Central, MT 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

016
FXUS65 KTFX 250154
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
754 PM MDT Thu Jul 24 2025

.KEY MESSAGES...

 - Seasonable temperatures over the next week.

 - Dry today, though coverage and intensity of thunderstorms
   increases Friday into the weekend.

 - Daily opportunities for showers and thunderstorms, some which look
   to be on the stronger side, persists into much of next week.

&&

.UPDATE...

There was just enough instability to initiate isolated convection
along the Idaho border in far Southwest Montana this evening.
This activity should fade out over the next couple of hours or
so. Otherwise, mostly clear skies and diminishing winds are
expected tonight. A strengthening southwesterly flow aloft will
bring breezy conditions to most areas on Friday. Widely scattered
showers and thunderstorms are then expected to develop over
Southwest Montana in the afternoon before moving northward into
Central Montana later in the evening. Localized strong wind gusts
and isolated lightning will be the primary storm hazards to watch
for. - RCG

&&

.DISCUSSION...
/Issued 136 PM MDT Thu Jul 24 2025/

 - Meteorological Overview:

A broad, overall lower amplitude upper level ridge will set up
across the eastern half of the CONUS over much of the upcoming week.
This setup will result in a persistent southwesterly flow aloft for
the Northern Rockies, which will become increasingly conducive to
shower and thunderstorm development, mainly in the afternoon and
evening through the upcoming week.

The ridge well to the east is just beginning to build today,
which is resulting in a more zonal flow aloft across the Northern
Rockies. Given the lack of forcing today and temperatures aloft
that are a touch too warm, the region looks to stay dry. That
said, a few showers near the ID border near Monida Pass and
vicinity cannot be ruled out this evening.

Flow becomes increasingly southwesterly Friday across the Northern
Rockies, with a compact upstream upper trough/low over CA shedding
some vorticity toward Montana Friday afternoon and evening. This
will support convective initiation in the early to mid-afternoon
hours across Southwest Montana, with activity shifting northeastward
into Central Montana in the late afternoon and evening. Forecast
soundings demonstrate deep inverted-V profiles, with limited shear.
Hence, the main threat for Friday appears to be gusty winds, with
some gusts in excess of 50 mph, as well as lightning. As this
activity shifts onto the plains Friday evening, increasing
convective inhibition should result in a diminishing trend after
sunset.

The overall setup does not change much this weekend, though flow
aloft does increase in magnitude, with slightly cooler temperatures
aloft as well. This will result in larger instability as well as
better shear, which will be more supportive of organized stronger to
severe thunderstorms Saturday and Sunday. The strongest
thunderstorms this weekend will support the risk for severe wind
gusts and large hail. Timing continues to be in the afternoon
through early evening with this activity, though with increasingly
cooler temperatures aloft, elevated overnight showers and
thunderstorms cannot be ruled out.

To not drag on saying the same things over and over again, much of
early next week is looking similar to this weekend, with daily
opportunities for strong to severe thunderstorms, most favored in
the afternoon and evening. The main difference moving deeper into
next week will be for increasing PWATs from better surface flow from
the east over the plains. Should storm motion be on the slower side
when the better moisture arrives, there would be an increased risk
for localized flash flooding from more persistent showers and
thunderstorms over any given area. -AM

 - Forecast Confidence & Scenarios:

Overall confidence levels in the evolution of the broad scale
pattern is high. Day to day uncertainty related to the timing and
exact placement of mesoscale features will continue until 12 to 24
hours prior to each round of showers and thunderstorms.

Gusty winds will be the main concern Friday with large hail also
becoming a concern Saturday and beyond where thunderstorms form.
As mentioned in the overview section above, moisture increases
toward the middle of next week, which will raise concerns for at
least localized heavy rain on top of threats already mentioned. -AM

&&

.AVIATION...
25/00Z TAF Period

Decreasing winds and mostly clear skies are expected tonight.
Southwesterly flow aloft strengthens on Friday and brings increased
west to southwesterly surface winds with gusts mostly staying in the
15 to 30 kt range. Widely scattered shower and thunderstorm
development will initiate over the higher terrain of Southwest
Montana after 25/20Z before moving north and eastward over the
central and southwest valleys through 26/06Z. Localized gusty
winds in excess of 35 kts and isolated lightning will be the
primary hazards. Afternoon temperatures on Friday will reach and
exceed 90 degrees for most terminals, potentially causing density
altitude concerns. - RCG

Refer to weather.gov/zlc for more detailed regional aviation
weather and hazard information.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  58  91  55  87 /   0   0   0  20
CTB  53  82  50  79 /   0   0   0  20
HLN  57  91  56  87 /   0  20  20  30
BZN  53  91  52  91 /   0  20  20  20
WYS  41  81  39  81 /  10  20   0  10
DLN  49  86  48  85 /   0  30  30  30
HVR  57  91  55  87 /   0   0   0   0
LWT  55  86  54  82 /   0  20  40  20

&&

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

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