Helena Valley Northeast, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

389
FXUS65 KTFX 081110
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
510 AM MDT Tue Jul 8 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Hot through tomorrow, with scattered showers and thunderstorms capable
   of producing strong wind gusts in the afternoon and evening.

 - Cooler Thursday with scattered showers and thunderstorms.

 - Warming back up this weekend, with low-end chances for a shower
   or thunderstorm Sunday and Monday.

&&

.DISCUSSION...
/Issued 229 AM MDT Tue Jul 8 2025/

 - Meteorological Overview:

Low amplitude upper level ridging continues across the west today,
though flow aloft gradually trends more zonal and eventually
southwesterly by tonight. Deep mixing and sufficient moisture look
to result in a few very high based showers and thunderstorms this
afternoon and evening across primarily Southwest Montana. Given the
deep mixing, collapsing cores from the showers and thunderstorms
that do manage to form will be capable of producing strong wind
gusts.

No change in thoughts with respect to the Heat Advisory for today.
The hottest areas look to be along the Great Falls to Havre corridor
and adjacent areas.

Aforementioned ridging nudges eastward toward the Great Plains
heading into Wednesday as troughing builds in off to the northwest.
An upper level low that was previously stuck under the ridging off
the coast of CA will lift northeastward toward the Northern
Rockies as a more open wave Wednesday afternoon and evening.
Slightly higher PWATs with this wave will allow for shower and
thunderstorm formation to spread further north for Wednesday
afternoon and evening compared to how today is forecast to play
out. Temperatures Wednesday will still be hot, and as a result
deep inverted-V soundings are once again forecast. Collapsing
cores from these showers and thunderstorms will be capable of
producing strong winds gusts Wednesday afternoon and evening.

Wednesday looks to be the last hot day of this stretch, as by
Thursday morning a cold front associated with a digging wave within
the broader trough looks to to cross the area. Hence, there are not
presently any plans to change the ongoing Heat Advisory for
Wednesday either.

Much cooler temperatures arrive behind the front Thursday. There is
not a ton of agreement as to just how potent the front will be from
a wind perspective, as well as its timing. It is reasonable to
expect at least a few hour period of gusty northwesterly to
northerly winds behind the cold front Thursday. Precipitation looks
to be largely scattered in nature, but greatest in coverage near
terrain.

A west-northwest (Briefly has ridging characteristics initially)
flow then develops in wake of this system heading into Friday and
the weekend. Temperatures trend warmer as a result, with largely dry
conditions forecast Friday into Saturday. Weak waves traversing
through this flow aloft look to bring low-end chances for an
afternoon or evening shower or thunderstorm by Sunday. -AM

 - Forecast Confidence & Scenarios:

The most challenging portion of the forecast in the near term is
deciding how to best advertise the risk for gusty winds from
collapsing showers and thunderstorms. Given the very deep inverted-V
soundings, little if any precipitation is forecast over the next day
or two. Using this logic, the chance for precipitation should
essentially be very low, or near zero. The issue with that is that
gusty winds from showers or thunderstorms cannot be specifically
mentioned if the chance for precipitation in the forecast is that
low. Hence, the compromise was to add low-end PoPs (Around 15%),
which allows the additional mention of gusty winds. It should be
made clear that little precipitation is forecast from showers and
thunderstorms over the next two days, especially today.

Looking ahead further, areas in and around Glacier NP have a roughly
40% chance for 0.25" rain Thursday. Brief instances of snow levels
down to or just below 9,000ft around Glacier NP does not seem
unreasonable Thursday morning into the early afternoon as the
coolest portion of the system passes overhead. -AM

&&

.AVIATION...
08/12Z TAF Period

VFR conditions are expected throughout the duration of the
0812/0912 TAF period as upper level ridging builds in over the
Northern Rockies; however, showers and thunderstorms developing
across Southwest Montana between 18-21z this afternoon and
persisting through 04-07z Wednesday will be capable of producing
gusty and erratic winds at the KBZN and KWYS terminals. These high
based showers and storms are not expected to reduce CIGS or VIS
below VFR. Scattered mountain obscuration is possible Tuesday
afternoon and evening across Southwest and into portions of
Central Montana due to the aforementioned showers and storms. -
Moldan

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  94  61  96  57 /   0   0  20  20
CTB  88  58  87  53 /   0   0   0  20
HLN  94  60  92  57 /   0  10  20  20
BZN  94  55  95  52 /  20  20  20  20
WYS  84  41  83  42 /  20  20  20  20
DLN  89  52  89  49 /  20  20  20  20
HVR  97  61  98  57 /   0  10  20  20
LWT  90  59  92  55 /  20  20  20  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM this afternoon to 8 PM MDT Wednesday for
Cascade County below 5000ft-Hill County-Northern Blaine County-
Western and Central Chouteau County.

&&

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