Helena Valley Northwest, MT 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

763
FXUS65 KTFX 261725
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1125 AM MDT Thu Jun 26 2025

Aviation Section Updated.

.KEY MESSAGES...

 - Isolated to scattered showers and thunderstorms are expected
   each afternoon and evening through Saturday.

 - Some thunderstorms will produce strong wind gusts today.

 - Temperatures trend above seasonal averages early next week
   with a return to to daily thunderstorm chances by the middle of
   next week.

&&

.UPDATE...
/Issued 1030 AM MDT Thu Jun 26 2025/

An area of clouds and light rain showers continues to push through
the area this morning, mostly in line with the forecast if not
slightly more widespread and longer lasting than forecast. The
impact of these lingering clouds on this afternoon`s clouds is a
bit uncertain, so we will see how things develop this afternoon.
Ludwig

&&

.DISCUSSION...
/Issued 1030 AM MDT Thu Jun 26 2025/

 - Meteorological Overview:

The Northern Rockies and MT remain under an overall
zonal/westerly flow aloft into the upcoming weekend with
persistent upper troughing centered in the Gulf of AK sending a
series mainly weak shortwave and upper level jet impulses from
the Pacific eastward along the US/Canadian border. A weak frontal
boundary aloft pushing east across the Rockies early this morning
will spread clouds and a few light showers across central and
north-central MT this morning with thunderstorm development across
central ID and west-central MT developing early this afternoon
and tracking east across north-central and southwest MT later
this afternoon through early this evening. There is a marginal
(5-10%) risk for severe thunderstorms this afternoon across
central/north-central MT, mainly due to strong wind gust
potential. Weaker disturbances moving through the westerly flow
will bring additional chances for widely scattered afternoon
showers and thunderstorms again Friday with more isolated coverage
of any showers/storms on Saturday. In the wake of this series of
disturbances upper level ridging will build across the interior
western US later this weekend into early next week, sending
temperatures above seasonal averages with afternoon maximums
reaching the upper 80s to around 90s across lower elevation
locations by Monday and Tuesday. Mainly dry conditions are also
expected through at least Monday with some moisture return
bringing an increase in daily shower/thunderstorm chances again by
the middle of next week.

 - Forecast Confidence & Scenarios:

Primary concern with thunderstorm activity this afternoon will be
strong winds, noting a relatively deep/elevated mix layer still
in place per the 06z KTFX upper air sounding and mid-level flow
increasing today, supporting the idea of convection with enhanced
outflow or a more organized cold pool despite only modest
instability. Some uncertainty exists related to how much of this
deeply mixed boundary layer will remain going into this afternoon
following mid-level moisture increases and even some light showers
moving across the area this morning. Hi-resolution/convection
allowing model guidance continues to key on stronger storms within
a corridor of CAPE in the 500-1000 J/kg range from roughly
southern Lewis and Clark county east through Fergus county this
afternoon with some higher CAPE potentially pooling east of the
Little Belts, giving the greatest risk for stronger thunderstorms
across Judith Basin and Fergus counties. Hoenisch

&&

.AVIATION...
26/18Z TAF Period

VFR conditions will prevail across all terminals during this TAF
period. The primary concern during this TAF period is isolated
strong to severe thunderstorms between 16/20Z and 17/03Z. All
thunderstorms will produce small hail, frequent lightning, and
gusty, erratic winds. The strongest thunderstorms have the potential
to produce wind gusts in excess of 48 kts. At the end of this TAF
period at the KGTF, KHLN, and KBZN terminals there is a 20 - 40%
chance for showers and thunderstorms. During any thunderstorm there
will be a brief period of mountain obscuration. -IG

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

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  81  55  80  52 /  40  30  30   0
CTB  76  55  74  50 /  20  10  10   0
HLN  80  54  80  52 /  70  30  40  10
BZN  85  50  85  50 /  30  20  30  10
WYS  74  39  75  39 /  10  10  20  10
DLN  79  48  80  47 /  30  10  10   0
HVR  84  55  83  53 /  20  30  10   0
LWT  79  52  75  51 /  40  40  50  20

&&

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

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