Lewistown, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

707
FXUS65 KTFX 090457
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1057 PM MDT Tue Jul 8 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Heat continues through Wednesday, along with a few gusty
   showers and thunderstorms each afternoon.

 - Cold front pushes through Thursday, bringing a few showers
   along with cooler temperatures.

 - Seasonable temperatures this weekend along with dry
   conditions, before another cold front pushes through early next
   week.

&&

.UPDATE...
/Issued 759 PM MDT Tue Jul 8 2025/
Updated forecast is out. Just adjusted grids towards current
trends. Isolated showers/thunderstorms continue to affect
Southwest MT. Not much measurable rainfall occurring, but some
wind gusts of 35 to 45 mph and lightning. Most of these storms
should diminish between Midnight and 2 AM. Overnight lows look on
track, but note it will take most of the night of cooling before
we reach the overnight lows, and just for a short time around day
break.

For Wednesday, it will be another very warm afternoon, with
afternoon temperatures of 95 to 100 common over the area. The heat
advisory continues for portions of North Central MT. The other
main concern will be the fire weather and thunderstorm potential.
It will be very close to fire weather statements for Wednesday,
but my current thinking is we have just enough greenness at lower
elevations to hold off for one more day, but with windy conditions
and humidity below 20 percent, any new fire starts will not be
easy to contain during peak heating. The mountains seem green
enough that they should be ok for this event. In terms of
thunderstorms, the HREF continues to prog numerous cells moving
from southwest to northeast through the CWA during the late
afternoon and evening hours, with gusty winds/lightning the main
impact. There will be the potential that some of these storms
could be severe. A short cool snap is then expected for just
Thursday and Friday. Brusda

&&

.DISCUSSION...
/Issued 759 PM MDT Tue Jul 8 2025/

Upper level ridging currently entrenched over the Western US has
brought a warm air mass into North Central and Southwestern
Montana, with many lower elevation locations reaching into the 90s
this afternoon. While skies have been clear so far today, we have
noticed a few puffy cumulus clouds start to develop across the
higher terrain of Southwestern Montana. A few of these may
eventually grow into some virga showers or even dry thunderstorms
this afternoon, potentially producing lightning strikes and gusty
winds.

Wednesday will be another warm day across North Central and
Southwestern Montana, with highs once again reaching the 90s for
most lower elevation locations. With this said, the ridge will
begin to break down during the afternoon, which will result in
gusty winds and increased shower and thunderstorm activity across
the area, mostly across the Plains. A few of the showers and
thunderstorms could produce some strong, gusty winds due to the
very dry air near the surface, and overall synoptic winds and low
RH values could lead to increased fire growth and spread. Please
see the Fire section below for more information.

Beyond tomorrow, a cooler air mass will push into the area,
bringing another chance for some showers on Thursday but then
drier air follows for the weekend. Temperatures will rise a bit
over the weekend, but another cold front will push through the
area on Monday, keeping the mercury from getting quite as high
next week.

 - Forecast Confidence & Scenarios:

Overall forecast confidence remains high through the next few
days, with shower and thunderstorm activity on Wednesday being the
biggest impactful question mark. Most mesoscale models show at
least some shower and thunderstorm development during the
afternoon, though there remains some uncertainty to the coverage
and organization of the storms. Regardless of the organization of
the storms, even a weak shower will be capable of producing gusty
outflows due to the dry air mass in place. Ludwig

&&

.AVIATION...
09/06Z TAF Period

A few lingering showers across Southwest Montana will maintain a
low-end threat for a gust of wind through 09Z or so. Otherwise,
attention turns to daytime hours Wednesday, when a myriad of
impacts develops. Initial concerns will be for gusty surface winds
developing mainly over the western plains. Low-level turbulence
will be possible in these areas.

Progressing further into the day, hot temperatures and deep mixing
will result in very high based showers and thunderstorms in the
afternoon and evening across the region. These showers and
thunderstorms will be capable of producing strong and erratic wind
gusts, with little in way of precipitation. -AM

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

&&

.FIRE WEATHER...
Hot, dry, and windy conditions are expected on Wednesday as an
upper level ridge breaks down across the area. While later in the
year this would necessitate a fire weather statement, current fuel
moisture and ERC values remain relatively low across the area,
which will help reduce the overall fire danger tomorrow.
Additionally, a few gusty showers and thunderstorms will be
possible tomorrow afternoon, which could cause any fires that do
get started to exhibit erratic fire behavior around any showers or
thunderstorms. Ludwig/Brusda

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  61  98  59  78 /   0  10  20  30
CTB  58  91  56  66 /   0   0  20  60
HLN  60  94  59  81 /  10  10  20  20
BZN  55  95  52  85 /  20  10  20  10
WYS  48  83  43  77 /  10  10  20  20
DLN  52  90  48  82 /  10  20  20  10
HVR  61 100  58  77 /   0  10  20  30
LWT  59  92  55  77 /   0  20  20  30

&&

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

&&

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