An upper-level trough brought in enough moisture and instability to produce isolated severe thunderstorms over Central MT. Dry air at the surface helped storms produce severe wind gusts.
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The episode as NWS TFX wrote it up.
An upper-level trough brought in enough moisture and instability to produce isolated severe thunderstorms over Central MT. Dry air at the surface helped storms produce severe wind gusts.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Great Falls, MT wrote its last area forecast discussion before the first event at May 26, 4:27 PM MST, 18 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Great Falls MT 527 PM MDT Tue May 26 2026 Aviation Section Updated. .KEY MESSAGES... - Very warm to hot temperatures continue for much of the workweek,especially over the plains. - There will also be daily rounds of showers and thunderstorms, some will be strong to severe and may contain localized heavy downpours. - Cooler temperatures and an opportunity for more widespread precipitation moves in this weekend. && .DISCUSSION... /Issued 139 PM MDT Tue May 26 2026/ - Meteorological Overview: A blocking pattern will maintain troughing over the western conus for the next week or so, with a mid -level closed low drifting southeastward from the Pacific NW into the Great Basin and remaining there through the workweek. This will bring in an increasingly unstable south to southeasterly flow aloft over the Northern Rockies for daily rounds of showers and thunderstorms. A shortwave will provide bulk shear over 30 kts today while ML CAPE stays mostly in the 200 to 600 J/kg range, highest along the Rocky Mountain Front. The primary threat for this afternoon and evening will be localized gusty winds with inverted V forecast soundings, but some instances of near or severe hail can't be ruled out with H500 temperatures as low as -15C. The flow aloft becomes weakly diffluent on Wednesday and Thursday and shear levels drop to negligible levels due to a general lack of shortwave energy; however, ML CAPE ramps up to over 1000 J/kg and PWATS begin to approach and even exceed the one inch mark, highest over central and north-central MT. The lack of forcing will result in lower storm coverage away from terrain, but localized downpours will become a concern in addition to a continued wind and hail threat. The closed low and associated elongated trough over the Pacific NW will undergo some shearing and transformation before it swings northward into the Northern Rockies heading towards the weekend. This looks to bring a round of stronger to severe thunderstorms sometime between late Thursday through early Saturday; followed by a period of cooling temperatures and more widespread areas of rain and embedded thunderstorms later Saturday into Sunday. A southwesterly flow aloft then develops in the wake of the departing system and brings warming temperatures and more rounds of showers and thunderstorms next week. - RCG - Forecast Confidence & Scenarios: Daily rounds of showers and thunderstorms though Friday followed by more widespread precipitation this weekend... Showers are already lifting northward into western and southwestern MT early this afternoon. Cloud cover is hampering CAPE and DCAPE over the southwest, but this should change as this activity moves over the warm and dry surface farther north. Forecast soundings indicate that strong wind gusts will be the primary hazard to deal with and this is corroborated by the latest suite of hires guidance. Convective wind gusts will generally range somewhere between 35 and 60 mph, strongest along the Rocky Mountain Front and over central/north-central MT, especially along and southwest of a Sweetgrass Hills to Lewistown line. Storm motion will be south/southeast to north/northwest, a little different than the typical southwest to northeast motion we typically see. This added easterly component may also increase the risk for an isolated land spout, although the chances for such an event are less than 2% within 25 miles of any point. The strongest and most widespread shower and thunderstorm activity will generally occur between 3 and 9 pm tonight, with a more isolated brand of showers continuing into the overnight hours. The wind shear necessary for the maintenance of stronger showers and thunderstorms drops off on Wednesday and Thursday with lack of shortwave energy and the forcing from the main low still far to our southwest. Some of this void will be fulfilled by ML CAPE levels increasing to over 1000 J/kg and PWATs nearing the one inch mark, but storm coverage should generally be slightly less than today for areas away from higher terrain. The slower storm motion and higher moisture levels will increase the concern for localized flooding for higher prone areas such as burn scars, especially for mountain areas and lower elevations west of I15. There will also be continued instances of thunderstorm winds and hail. Most ensembles keep the main closed low pressure system over the Great Basin area through the workweek before swinging back northward towards the Northern Rockies this weekend. If this pans out as forecast, there will be a period of stronger thunderstorms sometime between late Thursday and early Saturday followed by more widespread rains and embedded thunderstorms for the second half of the weekend. Although, there are some uncertainties to iron out, the heaviest precipitation is projected to occur along the Continental Divide and over central and southwest areas extending from the highway 12 corridor northward to the central island ranges. The latest NBM probabilistic guidance currently gives a 50 to 70% chance for rainfall amounts exceeding one inch for the 48 hour period ending 6 am Monday morning. - RCG && .AVIATION... 26/18Z TAF Period Predominately VFR conditions are expected through the 2700/2800 TAF period; however, temporary MVFR/low-VFR conditions are possible beneath shower and thunderstorm activity. Biggest impact to terminal operations will be gusty and erratic winds up to 45kts beneath and near thunderstorm activity across the KWYS, KEKS, KBZN, and KHLN through 03z this evening and 02-07z Wednesday at KGTF, KCTB and KLWT. Mountains will be obscured at times over the next 24 hours. - Moldan && .PRELIMINARY POINT TEMPS/POPS... GTF 55 85 56 91 / 70 30 30 20 CTB 54 82 52 88 / 70 50 50 30 HLN 51 84 52 90 / 70 40 30 20 BZN 45 83 46 90 / 50 40 20 20 WYS 37 79 39 83 / 50 40 10 20 DLN 43 79 46 87 / 50 30 20 20 HVR 61 95 55 97 / 40 30 30 20 LWT 53 85 52 89 / 50 20 30 30 && .TFX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 9 PM MDT Wednesday for Hill County-Northern Blaine County. && http://www.weather.gov/greatfalls
Special Weather Statement
National Weather Service Great Falls MT
450 PM MDT Tue May 26 2026
MTZ315-316-262330-
Upper Blackfoot and MacDonald Pass MT-Gates of the Mountains MT-
450 PM MDT Tue May 26 2026
...A STRONG THUNDERSTORM WILL IMPACT SOUTHWESTERN LEWIS AND CLARK
COUNTY THROUGH 530 PM MDT...
At 450 PM MDT, Doppler radar was tracking a strong thunderstorm 17
miles southeast of Lincoln, or 24 miles northwest of Helena, moving
northwest at 15 mph.
HAZARD...Wind gusts up to 50 mph and nickel size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Lincoln.
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.
&&
LAT...LON 4698 11266 4676 11230 4666 11240 4666 11242
4670 11242 4670 11254 4684 11254 4684 11280
4699 11280
TIME...MOT...LOC 2250Z 131DEG 20KT 4675 11247
MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH
RCGSpecial Weather Statement
National Weather Service Great Falls MT
508 PM MDT Tue May 26 2026
MTZ320-323-324-326-270000-
Missouri Headwaters MT-Big Belt, Bridger and Castle Mountains MT-
Canyon Ferry Area MT-Gallatin Valley MT-
508 PM MDT Tue May 26 2026
...STRONG THUNDERSTORMS WILL IMPACT SOUTHWESTERN BROADWATER...
NORTHEASTERN MADISON...SOUTHEASTERN JEFFERSON AND NORTHERN GALLATIN
COUNTIES THROUGH 600 PM MDT...
At 507 PM MDT, Doppler radar was tracking strong thunderstorms along
a line extending from 6 miles southwest of Manhattan to near
Belgrade. Movement was northwest at 30 mph.
HAZARD...Wind gusts of 45 to 55 mph and half inch hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Bozeman, Belgrade, Three Forks, Manhattan, Logan, Amsterdam, Trident,
Church Hill, Willow Creek, Menard, Madison Buffalo Jump State Park,
and Missouri Headwaters State Park.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.
&&
LAT...LON 4603 11188 4604 11096 4580 11079 4572 11079
4568 11158
TIME...MOT...LOC 2307Z 120DEG 26KT 4578 11142 4574 11116
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...55 MPH
WilsonSpecial Weather Statement
National Weather Service Great Falls MT
520 PM MDT Tue May 26 2026
MTZ313-317-270015-
Judith Basin County and Judith Gap MT-
Little Belt and Highwood Mountains MT-
520 PM MDT Tue May 26 2026
...A STRONG THUNDERSTORM WILL IMPACT SOUTHEASTERN JUDITH BASIN AND
SOUTHWESTERN FERGUS COUNTIES THROUGH 615 PM MDT...
At 520 PM MDT, Doppler radar was tracking a strong thunderstorm 17
miles south of Hobson, or 21 miles north of Harlowton, moving
northwest at 25 mph.
HAZARD...Wind gusts up to 50 mph and penny size hail.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor hail damage to vegetation is
possible.
Locations impacted include...
Utica and Sapphire Village.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4675 10976 4670 10982 4671 10987 4675 10996
4674 11003 4675 11005 4674 11006 4690 11041
4706 11017
TIME...MOT...LOC 2320Z 128DEG 21KT 4675 10988
MAX HAIL SIZE...0.75 IN
MAX WIND GUST...50 MPH
GlinskasThe Great Falls radar (KTFX), 142 km away, was scanning. The volume nearest the first event began at 23:47 UTC.
4 thunderstorm wind. Local standard time, as filed.
Mesonet station MTTOS Toston Bridge Us-287 Mp 87.0 thunderstorm wind gust.
Mesonet station GINM8 Ginger RAWS thunderstorm wind gust.
Mesonet station EKHM8 Elkhorn RAWS - 8 W Townsend thunderstorm wind gust.
AWOS station KSBX 2 nnw Shelby thunderstorm wind gust.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2026Every state in 2026This day in weather historyWarnings in Montana, May 2026
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1338753, 1338754, 1338755, 1338756.