Thunderstorms developed across Southwestern Montana in a warm, dry air mass ahead of an approaching cold front. These showers and thunderstorms produced widespread gusty outflow winds, including one that caused a 63 mph wind gust in Beaverhead 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.
Thunderstorms developed across Southwestern Montana in a warm, dry air mass ahead of an approaching cold front. These showers and thunderstorms produced widespread gusty outflow winds, including one that caused a 63 mph wind gust in Beaverhead County.
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 16, 2:00 PM MST, 14 minutes earlier.
Area Forecast Discussion National Weather Service Great Falls MT 300 PM MDT Mon Aug 16 2021 .SYNOPSIS... Hot, dry, and windy conditions today will give away to falling temperatures and widespread rain, even some high elevation snow, for the days on Tuesday and Wednesday. A strong cold front will drop south across the region tonight and through the day on Tuesday, which will help to usher in the cooler temperatures and widespread precipitation for the Northern Rockies. && .DISCUSSION... Tonight through Wednesday...primary forecast concern throughout the period will be a potent summer storm; which will usher in significantly cooler temperatures, brisk northerly winds, widespread precipitation, and overall conditions more similar to that of the fall season. Hot and windy conditions are occurring ahead of a strong cold front that will cross the region late tonight and through the day on Tuesday. Temperatures across the CWA have ranged from the mid-80s across western areas to the near 100 degrees across eastern areas, with very low relative humidity values in the upper single digits to teens at most locations. Mixing has been very efficient today, which has resulted in strong westerly surface winds and gusts across the region, especially over the plains of Central and North Central Montana where wind gusts of 40 to near 50 mph have been observed. Isolated to scattered showers and thunderstorms have developed along and southeast of a Helena to Lewistown line early this afternoon, with continued development and persistence of these showers and thunderstorms expected into the evening hours over the same general area. Given the very dry low and mid-levels across the Northern Rockies, gusty and erratic outflow winds are of concern beneath any shower or thunderstorm through this evening. The aforementioned strong cold front will begin to dive south from Alberta and into North Central Montana late this evening, Central Montana by the mid-morning hours on Tuesday, and Southwest Montana through the afternoon and evening hours on Tuesday. This cold front will provide a wind shift to the northwest and north, along with a prolonged period of wind speeds ranging from 15 to 30 mph through Wednesday morning/afternoon. Ahead of the cold front across Southwest Montana, strong south-to-southwest winds are expected during the day on Tuesday, especially within the north-south orientated valleys where winds will be funneled by the orientation of the terrain. In wake of the cold front, significantly cooler temperatures and widespread precipitation are expected across the region, with high temperatures on Wednesday struggling to rise into the 50s to low 60s (northwestern portions of North Central Montana will only see highs in the upper 50s and low 60s on Tuesday as well). Numerous locations on Wednesday could set record low maximum temperatures given the current forecast highs, especially across Central and North Central Montana where significant cloud cover will inhibit warming. As was mentioned earlier, widespread precipitation in the form of showers, thunderstorms, and even high elevation snow is expected to accompany the cold front and upper level disturbance throughout the period. At this time it appears the heaviest precipitation amounts, which could exceed 1.5", will be focused across Central Montana and in the north and east upslope favored areas. This precipitation event will occur over a prolonged (36- 48hr) period, with generally light to at times moderate intensity, thus hydrological concerns are currently low outside of some localized impacts to recent burn areas is extremely complex terrain. The period of highest precipitation amounts/intensity is generally expected from Tuesday evening through Wednesday morning, with precipitation ending from north to south Wednesday afternoon and evening. - Moldan Thursday through next Monday...Behind this front, the rest of the week looks to remain on the cooler side, as a persistent long-wave upper level trough lingers over the area. An embedded wave in this pattern looks to move through on Friday or Saturday, which would possibly bring another round of rainfall to parts of the area. Ludwig && .AVIATION... 1129 AM Mon Aug 16 2021 (16/18Z TAF period) Mix of VFR/MVFR VSBYS expected this aftn as FU and HZ persist across much of the region. Gusty WSWrly sfc winds are likely to prevail across the northern half of the region. For the southern half, sct TSRA/iso dry TSRA may develop late this aftn into the early evening hours...primarily impacting KBZN/KEKS/KWYS. Confidence of development and coverage is currently high enough to at least include VCTS for those TAFs. Convection diminishes tonight, ahead of a strong storm system that is prog to arrive Tuesday. RA is likely to dvlp by late in the 18z TAF period for portions of the region...with deteriorating flight rules for many areas expected nearly areawide by late Tues aftn. && .FIRE WEATHER... Critically dry and windy conditions are occurring across the region today ahead of a strong cold front, which will cross the region tonight and through the day on Tuesday. Isolated to scattered showers and thunderstorms have developed this afternoon across Southwest and into portions of Central Montana, with these showers and storms expected to persist into the evening hours tonight before dissipating. These showers and storms may be on the dry side, producing little rainfall and gusty/erratic outflow winds. The aforementioned cold front will then push south across the area tonight and through the day on Tuesday, brining a wind shift to the north followed by much cooler temperatures and widespread rain. - Moldan/Ludwig && .PRELIMINARY POINT TEMPS/POPS... GTF 55 69 45 55 / 20 90 100 90 CTB 51 56 43 55 / 30 90 100 70 HLN 61 77 49 58 / 20 90 100 100 BZN 55 87 49 62 / 60 60 90 90 WYS 46 82 46 63 / 30 30 80 80 DLN 54 84 45 60 / 30 70 90 90 HVR 58 76 47 58 / 10 80 100 80 LWT 59 81 47 55 / 30 70 80 90 && .TFX WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until midnight MDT tonight Central and Eastern Lewis and Clark National Forest Areas...Chouteau and Fergus Counties...Eastern Glacier/Toole/Central/Eastern Pondera/Liberty...Helena and Townsend Ranger Districts of the Helena National Forest...Hill and Blaine Counties...Lewis and Clark National Forest Rocky Mountain District-Rocky Mountain Front. Red Flag Warning until midnight MDT Tuesday night Gallatin National Forest. && http://www.weather.gov/greatfalls
Special Weather Statement
National Weather Service Great Falls MT
253 PM MDT Mon Aug 16 2021
MTZ053-054-162115-
Broadwater MT-Meagher MT-
253 PM MDT Mon Aug 16 2021
...A thunderstorm will impact portions of east central Broadwater
and south central Meagher Counties through 315 PM MDT...
At 252 PM MDT, Doppler radar was tracking a thunderstorm 15 miles
northeast of Townsend, moving east at 35 mph.
HAZARD...Winds in excess of 30 mph. A few lightning strikes are also
possible.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects.
Locations impacted include...
The southern portion of the Woods Creek Fire...White Sulphur Springs.
This includes the following highways...
Highway 12 between mile markers 11 and 49.
Highway 89 between mile markers 1 and 5, and between mile markers 54
and 57.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
&&
LAT...LON 4631 11129 4648 11138 4665 11081 4640 11069
TIME...MOT...LOC 2052Z 251DEG 31KT 4642 11123
MAX HAIL SIZE...0.00 IN
MAX WIND GUST...30 MPH
SCSpecial Weather Statement
National Weather Service Great Falls MT
300 PM MDT Mon Aug 16 2021
MTZ008-015-055-162130-
Madison MT-Beaverhead MT-Gallatin MT-
300 PM MDT Mon Aug 16 2021
...Isolated strong thunderstorms will impact portions of southern
Madison, central Beaverhead and central Gallatin Counties through
330 PM MDT...
At 256 PM MDT, Doppler radar was tracking a series of strong
thunderstorms, moving east at 35 mph from central Beaverhead County
across southern Madison County and through central Gallatin County.
HAZARD...Winds in excess of 40 mph and pea size hail. Isolated
lightning strikes are also possible.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Cameron and Big Sky.
This includes the following highways...
Highway 191 between mile markers 31 and 62.
Highway 287 between mile markers 14 and 45.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
Some of these storms 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 4505 11273 4550 11092 4536 11092 4535 11104
4508 11104 4511 11110 4505 11115 4501 11110
4493 11110 4476 11257
TIME...MOT...LOC 2056Z 251DEG 30KT 4513 11185
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH
SCSpecial Weather Statement
National Weather Service Great Falls MT
302 PM MDT Mon Aug 16 2021
MTZ051-162130-
Fergus MT-
302 PM MDT Mon Aug 16 2021
...Isolated strong thunderstorms will impact portions of
southeastern Fergus County through 330 PM MDT...
At 301 PM MDT, Doppler radar was tracking isolated strong
thunderstorms moving east at 35 mph across southeastern Fergus
County.
HAZARD...Winds in excess of 40 mph and pea size hail. Isolated
lightning strikes are also possible.
SOURCE...Radar indicated.
IMPACT...Gusty winds could knock down tree limbs and blow around
unsecured objects. Minor damage to outdoor objects is
possible.
Locations impacted include...
Grass Range and Forestgrove.
This includes the following highways...
Highway 200 between mile markers 112 and 113, and between mile
markers 116 and 123.
Highway 191 between mile markers 27 and 45.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
If outdoors, consider seeking shelter inside a building.
These storms 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 4676 10863 4675 10868 4675 10909 4697 10918
4709 10862 4708 10860
TIME...MOT...LOC 2101Z 257DEG 28KT 4692 10892
MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH
SCThe Missoula radar (KMSX), 198 km away, was scanning. The volume nearest the first event began at 21:15 UTC.
1 thunderstorm wind. Local standard time, as filed.
DOT sensor 6 miles southeast of Jackson, MT.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Montana in 2021Every state in 2021This day in weather historyWarnings in Montana, August 2021
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: 970578.