Hail in Montana, June 25, 2026

Area Forecast Discussion
National Weather Service Great Falls MT
1253 PM MDT Thu Jun 25 2026

.KEY MESSAGES...

 - Numerous showers and thunderstorms this afternoon, a few of which
   look to be on the strong side.

 - Additional showers and thunderstorms Friday and Saturday ahead
   of a cooler day on Sunday with additional precipitation into
   Monday.

 - Uncertainty remains in the exact track of the greatest
   precipitation amounts for this weekend into early next week.

&&

.DISCUSSION...

Broad upper level troughing with embedded upper level low presently
in the eastern Gulf of Alaska will continue to drift southeast
toward the Pacific Northwest through the remainder of the day and
through the end of the week. Flow aloft over the Northern Rockies
becomes increasingly southwesterly as a result, with embedded waves
ejecting from the approaching broader trough supporting several
rounds of showers and thunderstorms through Saturday.

The first wave moves through today, though there looks to be a bit
of a split regime from a parameter space perspective. Areas over
the plains looks to have the greatest instability, while areas
over Southwest Montana look to have the greatest shear. Where both
of these better parameter spaces overlap this afternoon (Most
likely between the MT-200 and I-90 corridors), there will be the
risk for large hail in the strongest thunderstorms.

Forcing increases a bit heading into Friday as the core of the
upper low approaches the Pacific NW. This forcing looks sufficient
to result in plenty of cloud cover and showers around through the
morning near the Continental Divide. This keeps confidence low
with respect for any stronger thunderstorms developing in these
areas by Friday afternoon. Areas further east have a better
opportunity to receive some daytime heating, which will be the
primary focus for afternoon thunderstorm development. While this
occurs, stronger southwesterly flow aloft looks to nudge in from
the south. This will result in gradually increasing shear from
south to north through the afternoon. Should the instability
develop in areas where the shear is able to move in quick enough,
there will be a localized risk for a stronger thunderstorm, most
favored across Central Montana east of I-15. Also worth noting
will be the risk for brief heavy downpours with the strongest
thunderstorms given anomalous moisture in place. Areas
susceptible to impacts from briefly heavy rain should be aware of
this risk, including areas around recent burn scars such as Horse
Gulch.

The increasing southwesterly flow aloft mentioned prior will also
result in a generally breezy day for most areas south of I-90 from
late Friday morning through the afternoon. The risk for impactful
gusts (58+ mph) appears low/localized at this time, however.

Additional showers and thunderstorms will be around again on
Saturday as the core of the upper low begins to translate across the
Northern Rockies. The risk for any stronger thunderstorm over the
plains and adjacent areas of Central Montana will be conditional on
how much surface moisture will be in place. Guidance that features
higher Tds, closer to 55-60F, features ample instability and shear
that would be capable of producing strong to severe thunderstorms.
Guidance that keeps Tds closer to 50F keeps instability much lower
and as a result would be result in a more run-of-the-mill type of
thunderstorm day. All that said, there is a marginal risk for severe
weather Saturday near and east of US-87.

There remains quite a bit of uncertainty with respect to the track
that the most favorable forcing for stratiform type precipitation
will take later weekend into next week. Most guidance keeps the
most favorable forcing along the Rocky Mountain Front, including
in Glacier NP. Latest trends in some guidance actually places the
better forcing west of the Continental Divide by Sunday into
Sunday night. The main takeaway will be for cooler conditions
heading into Sunday, with snow levels falling furthest where the
upper level low tracks. Cold/raw back country conditions will
exist, particularly where the greatest precipitation falls.

General troughing holds through the middle of next week, which will
keep things unsettled. Temperatures near to a touch below average
with dally opportunity for showers and thunderstorms is a reasonable
expectation at this point for this timeframe. -AM

&&

.AVIATION...
25/18Z TAF Period

Primary concern this TAF period will be for numerous showers and
thunderstorms developing across the region this afternoon and early
evening. Gusty winds, hail, and lightning will be the primary
concern from the strongest thunderstorms. Precipitation diminishes
through the late evening and overnight before developing once
again along the Continental Divide later tomorrow morning. Gusty
southwest winds slowly develop late tomorrow morning across
portions of Southwest Montana. -AM

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  53  76  51  70 /  20  70  70  50
CTB  52  69  48  68 /  30  60  40  20
HLN  56  75  51  67 /  20  80  70  80
BZN  51  78  47  65 /  30  50  70 100
WYS  42  73  40  56 /  30  30  60 100
DLN  53  74  46  62 /  10  50  70 100
HVR  50  80  51  75 /  40  50  90  40
LWT  47  76  47  67 /  50  60  70  90

&&

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

http://www.weather.gov/greatfalls

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