Severe Thunderstorm Warning 14, NWS Great Falls, MT

Area Forecast Discussion
National Weather Service Great Falls MT
332 PM MDT Fri May 29 2026

.KEY MESSAGES...

 - Scattered to widespread showers and thunderstorms will continue
   through the evening across the region, with an isolated chance
   of severe winds gusts and large hail with the strongest storms.

 - Widespread rainfall and high terrain snow expected Saturday
   through Monday.

 - Flooding due to heavy rainfall are possible for areas near and
   west of the I-15 corridor across North-Central MT.

 - Daily chances for showers and thunderstorms continue next
   week, with a warm up in temperatures.

&&

.DISCUSSION...

 - Meteorological Overview:

A closed upper-level low slowly moving through the region will
bring wetter conditions to the region through the beginning of
next week. This afternoon, scattered showers and thunderstorms
have popped up across the region, and will continue through the
rest of the day. Good shear and instability in the region will
allow for some storms to become strong to severe today. The main
hazards will be severe wind gusts greater than 58 mph, small to
large hail, and a localized flash flooding over urban/burn scar
areas. The best corridor for severe storms lies along and north of
MT Highway 200. -Wilson

For Saturday through Monday, the upper level low will continue to
drift northward and move from south to north across MT. This will
allow for widespread rain to affect much of the CWA this weekend,
with the heaviest rainfall likely along and west of the I-15
corridor across North-Central MT. Temperatures will be much
cooler starting Saturday. The airmass will still be unstable
enough for some lightning strikes during the afternoon/evening
hours over the weekend though. Snow levels will remain above pass
level, with light slushy accumulations near 7,000ft possible. The
low level jet picks up Sunday morning across the Hi-line/North-
Central MT. This will bring breezy to gusty winds for that area
throughout the day Sunday, with the strongest in the morning
hours. Winds for the most part will stay below High Wind Warning
criteria, but the combination of the east/northeast winds and
heavy rainfall threat can loosen trees up better, causing them to
fall and cause tree damage/power outages.

For Tuesday through next Friday...expect a gradual warming trend
by later next week. There will continue to be a chance for
scattered showers/thunderstorms most days next week. The latest
GFS/EC are showing signs of another fairly good weather system
later next week, but the models differ on timing/strength a
bit, thus confidence is low at this time for precip amounts late
next week. -Wilson/Brusda

 - Forecast Confidence & Scenarios:

Confidence has been increasing for the risk of 1 to 3 inches of
rainfall across the region. The 25th percentile of ensemble
members (lower end amounts) show between 0.75" to 1.5", with the
75th percentile (higher end amounts) between 1.5" to 3". The 90th
percentile (10% chance of occurring) shows 3.5" to 4" for areas
along and west of the I-15 corridor across North-Central MT. There
may be some enhanced impacts to rivers and creeks due to snowmelt
runoff depending on how quickly the cold air comes in. As a
result, a Flood Watch has been issued Saturday through Monday (see
Hydrology for more info). Where the corridor of best moisture/low
level convergence sets up is ultimately where the heaviest
precipitation will fall.

The colder air is not as cold/deep as previous forecasts.
Therefore, impacts are expected to be limited to slushy
accumulations mostly above 7,000ft. We will closely monitor for
any additional impacts in case the trend changes.-Wilson

&&

.AVIATION...
29/12Z TAF Period

Isolated thunderstorms will affect areas mainly north of Highway 2
through about 14z this morning. Otherwise scattered thunderstorms
will develop over Southwest MT this afternoon and then move
northward through North Central MT during the late
afternoon/evening hours. Strong gusty surface winds/heavy rain
likely with stronger storms this afternoon. A more widespread rain
starts to develop after 09z Saturday over Southwest MT, moving
northwest towards the Helena/Great Falls area by 12z Sat.
Widespread rain likely the rest of Sat and much of Sun over the
CWA. Mountains will be obscured at times this afternoon by passing
thunderstorms, then become obscured once again over
Central/Southwest MT after 09z Sat as the widespread rain begins.
Brusda

&&

.HYDROLOGY...

Widespread rainfall will affect the CWA this weekend. In looking
at NOAA Atlas 14, 2 inch rainfalls in a 2 day period happen about
every 2 to 5 years in the Great Falls area. For areas west of
Augusta, a 3 inch rainfall in a 2 day period also happens about
every 2 to 5 years. Thus the spring storm that we are forecasting
this weekend is on par for a fairly common spring storm...it is
just that we have not had a storm like this in a few years.

Current river forecasts for Saint Mary, and the Sun River are
forecasted to go into flood stage late Sunday into Monday. This
forecast is heavily dependent on the precipitation amounts and
could change in the coming day(s). Many mountains have melted out
the snowpack for the season, but a few areas along the divide do
have snow, especially Glacier Park. This will add to run off
concerns for rivers like the Sun River, Badger Creek, and the St
Mary's River.

Additionally, areal QPF of 1 to 3 inches is possible over the
western half of North Central MT. Overall, much of the area should
be able to handle the first few inches. Recent model runs have an
isolated (10% chance) for 4" of rainfall. The combination of
heavy rainfall and impacts from river/creek flooding has resulted
in a Flood Watch being issued for North-Central MT along and west
of the I-15 corridor. Another impact with be rural, dirt roads
could become washed out if the higher end amounts end up
happening. Depending on how the rivers respond, additional or
extensions of flood products may be needed.

-Brusda/Wilson

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  69  46  53 /  80  90 100 100
CTB  52  67  41  51 /  80  80 100 100
HLN  53  65  44  53 /  60 100 100  90
BZN  47  62  39  51 /  40 100 100  90
WYS  39  56  34  49 /  40 100  80  90
DLN  47  59  39  54 /  40 100  90  80
HVR  54  79  46  62 /  80  70 100 100
LWT  49  67  43  53 /  50  90 100  90

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Flood Watch from Saturday afternoon through Monday afternoon for
Cascade County below 5000ft-East Glacier Park Region-Eastern
Glacier, Western Toole, and Central Pondera-Eastern Pondera and
Eastern Teton-Gates of the Mountains-Northern High Plains-
Southern High Plains-Southern Rocky Mountain Front.

&&

http://www.weather.gov/greatfalls

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Special Weather Statement
National Weather Service Great Falls MT
359 PM MDT Fri May 29 2026

MTZ311-292230-
Bears Paw Mountains and Southern Blaine MT-
359 PM MDT Fri May 29 2026

...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN BLAINE AND
SOUTHEASTERN HILL COUNTIES THROUGH 430 PM MDT...

At 359 PM MDT, Doppler radar was tracking a strong thunderstorm 14
miles east of Parker School, or 20 miles southeast of Havre, moving
north at 10 mph.

HAZARD...Penny size hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

Locations impacted include...
Lloyd.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4823 10943 4824 10950 4840 10954 4835 10926
TIME...MOT...LOC 2159Z 197DEG 10KT 4829 10944

MAX HAIL SIZE...0.75 IN
MAX WIND GUST...<30 MPH

Moldan

Special Weather Statement
National Weather Service Great Falls MT
400 PM MDT Fri May 29 2026

MTZ313-317-292230-
Judith Basin County and Judith Gap MT-
Little Belt and Highwood Mountains MT-
400 PM MDT Fri May 29 2026

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL JUDITH BASIN COUNTY
THROUGH 430 PM MDT...

At 400 PM MDT, Doppler radar was tracking a strong thunderstorm 9
miles south of Stanford. This thunderstorm was nearly stationary.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

This storm will remain over mainly rural areas of central Judith
Basin County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4698 11022 4700 11028 4712 11029 4703 11009
TIME...MOT...LOC 2200Z 217DEG 4KT 4701 11023

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

Moldan

Special Weather Statement
National Weather Service Great Falls MT
411 PM MDT Fri May 29 2026

MTZ313-317-292245-
Judith Basin County and Judith Gap MT-
Little Belt and Highwood Mountains MT-
411 PM MDT Fri May 29 2026

...A STRONG THUNDERSTORM WILL IMPACT CENTRAL JUDITH BASIN COUNTY
THROUGH 445 PM MDT...

At 410 PM MDT, Doppler radar was tracking a strong thunderstorm 14
miles southwest of Hobson, or 18 miles south of Stanford, moving
north at 10 mph.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

This storm will remain over mainly rural areas of central Judith
Basin County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4686 11006 4687 11019 4697 11019 4696 11000
TIME...MOT...LOC 2210Z 187DEG 9KT 4690 11013

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

Moldan

Special Weather Statement
National Weather Service Great Falls MT
414 PM MDT Fri May 29 2026

MTZ311-292245-
Bears Paw Mountains and Southern Blaine MT-
414 PM MDT Fri May 29 2026

...A STRONG THUNDERSTORM WILL IMPACT SOUTHERN BLAINE COUNTY THROUGH
445 PM MDT...

At 413 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles southwest of Hays, or 13 miles west of Zortman, moving north at
5 mph.

HAZARD...Nickel size hail.

SOURCE...Radar indicated.

IMPACT...Minor hail damage to vegetation is possible.

This storm will remain over mainly rural areas of southern Blaine
County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4792 10872 4792 10888 4791 10889 4799 10893
      4800 10868
TIME...MOT...LOC 2213Z 173DEG 6KT 4793 10882

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...<30 MPH

Moldan

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