Helena Valley Northeast, Montana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

936
FXUS65 KTFX 190140
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
740 PM MDT Thu Jun 18 2026

.KEY MESSAGES...

Key Points

 - Afternoon showers and thunderstorms continue through this
   evening.
 - Warming trend through Saturday ahead of a cold front that will
   bring showers and thunderstorms, some of which may be heavy.
 - Closer to average to start next week, but afternoon showers
   and thunderstorms will remain common.

&&

.UPDATE...

Slight adjustments were made to the short-term forecast based on
updated model guidance and trending observations but otherwise no
major changes were made.  -thor

&&

.DISCUSSION...
/Issued 556 PM MDT Thu Jun 18 2026/

 - Meteorological Overview:

Northwesterly flow aloft continues this afternoon, which is
helping to spur the development of pop up afternoon showers and a
few rumbles of thunder today. Overall, these showers should not be
overly impactful (aside from those caught outside without a
raincoat or umbrella) and provide some more beneficial rain,
though some small hail cant be entirely ruled out given the cold
air aloft.

Once these showers and thunderstorms dissipate this evening, we
will have around a 24-36 hour period of dry weather across North
Central and Southwestern Montana as a weak transient upper level
ridge slides across the area. As it does, temperatures will remain
warm across the Southwest Valleys where highs will get to around
80, though the plains will top out around 70.

A cold front will push through the area on Saturday, bringing
with it another round of showers and thunderstorms as it pushes
through the area. With this forcing mechanism in place, along with
some better atmospheric dynamics and more moisture, the showers
and storms could be a bit more organized and stronger. Right now,
it seems that the largest concern will be some heavy rainfall from
the storms, though some gusty winds and hail will also be
possible.

Beyond Sunday, northwesterly flow aloft will return to the area
for the first half of next week, keeping temperatures closer to
average with some afternoon showers and thunderstorms. Another
weather system will look to push into the area around midweek,
which would bring about another chance for some more organized
shower and thunderstorm activity.

 - Forecast Confidence & Scenarios:

Showers and thunderstorms today: Overall, showers and
thunderstorms this afternoon should remain generally beneficial.
However, a few of the stronger thunderstorms may be able to
produce some small hail and gusty winds, as temperatures aloft are
sufficiently cool to allow for some small hail growth and there
is just enough of a dry mixed layer at the surface to promote some
modestly gusty outflows to around 40mph or so on the high end.

Saturday Thunderstorms: A cold front moving through the
northwestern US on Saturday will bring a round of more organized
showers and thunderstorms to the area as it pushes through. While
a widespread severe outbreak is not expected at this time, the
presence of a forcing mechanism (the front), modest instability,
and modest shear profiles indicate there is some potential for the
storms to be a bit better organized than those of today and
tomorrow. Given this, I cant rule out the possibility of a
stronger storm or two that would be able to produce some
borderline severe wind or hail (58 mph gusts or 1 inch diameter
hail) ahead of the front. The other possibility is that, instead
of hail, a few of the storms could produce some heavier downpours,
which could produce some minor flooding concerns, particularly in
southwestern Montana. Burn scars, such as the Horse Gulch, will
be the main concern, but some ponding in low lying areas is also
possible. Ludwig

&&

.AVIATION...
19/00Z TAF Period

Scattered showers and thunderstorms have begun to decrease across
central and north-central MT, before dissipating by 03Z. Skies
will clear overnight, and winds will turn light and variable
around 04Z. -Dzomba

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  44  73  48  83 /  20   0   0  10
CTB  40  70  46  79 /  20   0   0  10
HLN  46  78  50  83 /  20   0   0  30
BZN  42  78  47  79 /   0   0  10  60
WYS  36  80  43  72 /   0   0  10  90
DLN  43  81  49  76 /   0   0  10  70
HVR  41  72  48  82 /  20   0   0   0
LWT  39  70  45  77 /  20   0   0  20

&&

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

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