A trough with an embedded disturbance aloft produced isolated showers and thunderstorms across the region. S.
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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.
A trough with an embedded disturbance aloft produced isolated showers and thunderstorms across the region. Increased monsoonal moisture from the Southwest U.S. created enough buoyancy to produce a few stronger thunderstorms. One severe storm produced severe winds in Southwest Montana.
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 Sep 9, 1:59 PM MST, 2 hours 51 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Great Falls MT 259 PM MDT Tue Sep 9 2025 .KEY MESSAGES... - Hazy skies will continue across portions of north-central Montana through Wednesday afternoon. - Isolated to scattered showers expected through the rest of the evening into tomorrow. - More widespread chances for showers Thursday through Sunday. && .DISCUSSION... - Meteorological Overview: Today an upper-level ridge is over North-central, Central, and Southwestern Montana with an upper-level trough approaching the area. As a result it will be another warm day today. Due to the southwest flow aloft combined with monsoonal moisture, there will be isolated showers and thunderstorms this afternoon and evening across North-central, Central, and Southwestern Montana. The strongest thunderstorms will produce strong wind gusts, frequent lightning, and a brief heavy downpour. On Wednesday the upper-level ridge begins to shift eastward and the upper-level trough approaches Montana. On Wednesday it will be another warm day with isolated showers and thunderstorms across North-central, Central, and Southwestern Montana due to the upper-level ridge and approaching trough combined with monsoonal moisture. Today and Wednesday due to the Southwest flow aloft there will be hazy skies from regional wildfires across North-central, Central, and Southwestern Montana. On Thursday the upper-level trough moves over North-central, Central, and Southwestern Montana. This will cool temperatures down and bring another round of showers and thunderstorms to the area. The strongest thunderstorms will produce strong winds, frequent lightning, and a brief heavy downpour. On Friday the upper-level trough remains over North-central, Central, and Southwestern Montana. This will cool temperatures down to near seasonal averages across the area and bring showers to the area. Saturday through Monday generally an upper-level trough persists with a few upper- level shortwaves. This will keep temperatures at about seasonal averages with daily chances for showers across North-central, Central, and Southwestern Montana Saturday through Monday. -IG - Forecast Confidence & Scenarios: Showers/Thunderstorms Today through Thursday: Coverage through this evening and tomorrow afternoon will be isolated to scattered. In general, these storms are expected to stay far below severe thresholds although a couple stronger storms could produce locally heavy downpours. The bigger concern is for what occurs Thursday afternoon across north-central Montana. Looking at all the parameters for instability, the potential exists for stronger storms to develop along the Hi-Line with higher probabilities of severe weather further east of the region. The uncertainty in this set up is in how the cold front progresses and what timeframe it arrives in central Montana. Variations between model runs have made it difficult to pin down exactly what the threat level will be for Thursday. But there is enough of a concern for what might unfold that this will be something to watch with future updates. Rainfall Amounts: Thursday through Sunday, across north-central and central Montana there is a greater than 75% chance of at least 0.25", a 50-70% chance of at least 0.5", and a 30-50% chance of at least 0.75". Across southwest Montana Thursday through Sunday there is a 40-60% chance of at least 0.25" and a 20-40% chance of at least 0.5". Thus the takeaway for now is that most locations will see some measurable rain through the weekend. Some heavier amounts are possible but it is more likely that the heavy amounts will be local to where the stronger storms develop. In general, the Hi- Line has the highest probabilities of seeing these higher amounts. -thor && .AVIATION... 09/18Z TAF Period VFR is forecast to dominate terminals across the region through the next 24+ hours with a low probability of restrictions due to localized shower activity and haze/smoke from nearby wildfires. At the regional scale, a band of shower activity with isolated embedded T is presently as of noon Tue moving into SW MT and is expected to push north through today, exiting north overnight. SHRA/T coverage is forecast to grow more sparse further north and east... with a 40% chance in SW MT versus a 20% or less chance along the Hi-Line. Scattered showers may linger along the Hi-Line in the early daytime on Wed. Though VFR CIGs are expected with this activity, mountain top obscuration will still be present in the vicinity of showers. Additionally nearby wildfire smoke will cause periodic reduction in VIS...though restrictions are not expected at terminals. For winds...broad, regional flow is generally light and out of the southeast, however terrain funneling and variable flow from shower activity will dictate direction with speeds generally below 10 kts. Localized gusts 15-25 kts can be expected with -SHRA; iso T will also be present in the region and capable of producing gusty/erratic winds, with around a 25% chance in SW MT. -Casey Refer to weather.gov/zlc for more detailed regional aviation weather and hazard information. && .PRELIMINARY POINT TEMPS/POPS... GTF 53 82 53 75 / 30 10 20 50 CTB 49 79 51 74 / 30 20 20 40 HLN 52 83 53 78 / 40 20 30 60 BZN 47 83 50 78 / 20 10 20 60 WYS 37 73 39 67 / 40 10 30 60 DLN 45 78 46 73 / 40 10 10 40 HVR 54 85 55 79 / 20 20 20 40 LWT 52 82 54 74 / 20 10 20 60 && .TFX WATCHES/WARNINGS/ADVISORIES... None. && http://www.weather.gov/greatfalls
The Pocatello radar (KSFX), 209 km away, was scanning. The volume nearest the first event began at 23:48 UTC.
1 thunderstorm wind. Local standard time, as filed.
Corrects previous non-thunderstorm wind gust report from 10 WSW Grant. Mesonet station BRRM8 Brenner RAWS measured a 64 mph wind gust. Time is estimated based on radar.
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, September 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: 1287770.