An embedded wave within more broad troughing digging into the Pacific Northwest moved across the region late night August 6 into August 7. Elevated instability increased as showers and thunderstorms moved eastward from Central Montana toward Fergus county.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS TFX wrote it up.
An embedded wave within more broad troughing digging into the Pacific Northwest moved across the region late night August 6 into August 7. Elevated instability increased as showers and thunderstorms moved eastward from Central Montana toward Fergus county. As these thunderstorms continued to balloon and cross Lewistown Divide, they became severe, producing a wide swath of gusts in excess of 55 mph, including a peak gust of 71 mph just east of Lewistown Divide.
Later in the day ample instability and shear developed across Fergus county again to result in an instance of large hail near Grass Range.
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 Aug 7, 12:32 AM MST, 1 hour 38 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Great Falls MT 132 AM MDT Thu Aug 7 2025 .KEY MESSAGES... - Numerous showers and thunderstorms this afternoon and evening across the region, with a few on the strong to severe side. - Much cooler for Friday, with showers and a few thunderstorms in the afternoon. - Trending back warmer this weekend into next week. && .DISCUSSION... - Meteorological Overview: The initial wave associated with an approaching upper trough over the Pacific NW is moving overhead early this morning. Sufficient forcing from this wave has allowed for elevated showers and thunderstorms to develop, mainly over the plains. This activity will spread eastward through the remainder of the overnight and exit this morning. Attention then turns to this afternoon and evening, when the main wave of the aforementioned trough begins to swing through. Stout forcing from this troughing will help maximize what little instability develops through the afternoon, resulting in numerous showers and thunderstorms this afternoon and evening. The most robust thunderstorms that form will be capable of taking on at least brief supercell characteristics given the strong shear in place. Forecast hodographs feature long, straight shear profiles, suggesting large hail will be a concern in the most robust thunderstorms, on top of strong wind gusts. The setup will be discussed a bit further in the uncertainty section below. Cooler temperatures move in behind a front, which will allow for a cool day Friday as the core of the upper trough moves across the Northern Rockies. Although surface temperatures will be below average, sufficiently cool temperatures aloft will still allow for afternoon showers and thunderstorms. The risk for a strong thunderstorm is low, though it should be mentioned that a period of more widespread (synoptic) gusty winds do look to develop during the day Friday over the plains. The upper troughing moves off to the east this weekend, allowing for a northwesterly flow aloft to develop well off to the east of a building ridge over the eastern Pacific Ocean. This setup more or less continues into the middle of next week. Glancing blows from waves traversing through the northwesterly flow aloft may promote low-end chances for showers and thunderstorms at times early next week, but the main takeaway is for a warming and largely drying trend heading into early next week. Confidence in specifics decreases significantly late next week, but ensemble means do favor troughing in some capacity. -AM - Forecast Confidence & Scenarios: There still remains some uncertainty with respect to how well the region destabilizes today. Forcing from the approaching trough looks to result in quite a bit of cloud cover, which would limit just how much surface heating and resulting instability develops. Should cloud cover hold off a bit more in the late morning and early afternoon, a trend toward more numerous strong to severe thunderstorms thunderstorms would be reasonable. Conversely, if the region fails to clear out in a meaningful way, the risk for a strong to severe thunderstorm would be lower. Overall, the area with the best chance for ample instability to develop would be in the Lewistown area and vicinity. -AM && .AVIATION... 07/06Z TAF Period A shortwave passing through a southwesterly flow aloft will continue to bring scattered showers and few isolated thunderstorms through 07/12Z, with the most coverage over Central/North-central Montana. Isolated instances of gusty winds and lightning looks to be the primary concerns for the overnight hours. The main trough, currently over the Pacific Northwest, will approach the Northern Rockies on Thursday and send a couple rounds of showers and thunderstorms through Southwest and North-central Montana between 07/18 and 08/06Z. The strongest and most widespread activity looks to occur over areas east of a KHLN to KHVR line and north of I90. Some storms will be capable of strong, gusty winds, hail, brief downpours in addition to lightning. - RCG Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 76 49 71 53 / 40 50 30 20 CTB 72 50 65 50 / 30 20 50 20 HLN 76 48 72 51 / 70 60 20 10 BZN 81 44 73 45 / 60 80 20 10 WYS 76 36 68 32 / 30 50 20 0 DLN 78 40 71 40 / 50 50 10 0 HVR 80 53 70 54 / 30 40 60 50 LWT 74 46 67 49 / 60 70 40 20 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && http://www.weather.gov/greatfalls
Special Weather Statement
National Weather Service Great Falls MT
238 AM MDT Thu Aug 7 2025
MTZ313-314-318-070915-
Snowy and Judith Mountains MT-Judith Basin County and Judith Gap MT-
Fergus County below 4500ft MT-
238 AM MDT Thu Aug 7 2025
...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL JUDITH BASIN AND
CENTRAL FERGUS COUNTIES THROUGH 315 AM MDT...
At 236 AM MDT, Doppler radar was tracking a strong thunderstorm over
Moore, or 14 miles west of Lewistown, moving northeast at 40 mph.
HAZARD...Wind gusts up to 40 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...
Lewistown, Hobson, Moore, Danvers, Suffolk, Forestgrove, Moccasin,
Giltedge, Glengarry, Heath, Hilger, and Christina.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Torrential rainfall is also occurring with this storm and may lead to
localized flooding. Do not drive your vehicle through flooded
roadways.
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 4684 10973 4710 10999 4752 10928 4699 10887
TIME...MOT...LOC 0836Z 238DEG 43KT 4700 10973
MAX HAIL SIZE...0.50 IN
MAX WIND GUST...40 MPH
RCGPreliminary Local Storm Report
National Weather Service Great Falls MT
302 AM MDT Thu Aug 7 2025
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0248 AM Tstm Wnd Gst 3 SW Lewistown 47.03N 109.47W
08/07/2025 M52 MPH Fergus MT ASOS
ASOS station KLWT Lewistown Airport.
&&
AMThe Billings radar (KBLX), 145 km away, was scanning. The volume nearest the first event began at 09:10 UTC.
4 thunderstorm wind, 2 hail. Local standard time, as filed.
MT Mesonet station Forestgrove N. Peak gust for the sensor.
AWOS station K1NM Novemeber. Peak gust for the sensor.
Weather underground station near Grass Range.
AWOS station K1OM Oscar. Peak gust for the thunderstorm at this sensor.
Spotter estimated hail up to an inch in size.
Report received of a wind shield cracked from falling hail.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2025Every state in 2025This day in weather historyWarnings in Montana, August 2025
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: 1287563, 1287564, 1287565, 1287566, 1287567, 1287568.