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Severe · Flash Flood WatchActive alert

Flash Flood Watch issued September 18 at 3:21AM MDT until September 20

Affecting Little Belt and Highwood Mountains; Big Belt, Bridger and Castle Mountains; Elkhorn and Boulder Mountains; Gallatin Valley

In effect until: Sep 18, 2026, 9:15 PM

Little Belt and Highwood Mountains; Big Belt, Bridger and Castle Mountains; Elkhorn and Boulder Mountains; Gallatin Valley

Possible impact zone in Big Belt, Bridger and Castle Mountains; conditions develop through 9:15 PM.

You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued.

Read the original bulletin (official text)
* WHAT...Flash flooding and debris flows caused by excessive rainfall
are possible over the Horse Gulch area and burn scars from the
summer of 2026.

* WHERE...Portions of central and southwest Montana, including the
following areas, in central Montana, Big Belt, Bridger and Castle
Mountains, Elkhorn and Boulder Mountains and Little Belt and
Highwood Mountains. In southwest Montana, Gallatin Valley.

* WHEN...From this evening through Saturday evening.

* IMPACTS...Heavy rainfall over the Horse Gulch and Burn Scars of
2026 is expected up to and during the period of the watch.
Residents near he Horse Gulch area and burn scars from the summer
of 2026 should prepare for potential debris flow. Be sure to stay
up to date with information from local authorities. Heavy rainfall
could trigger flash flooding of low-lying areas, urbanized street
flooding, and debris flows in and near recent wildfire burn scars.

* ADDITIONAL DETAILS...
- National Weather Service Meteorologists are forecasting heavy
rainfall over recent burn scars, which may lead to flash flooding
and debris flows.
- Some locations that may experience flash flooding include...
Areas near recent burn scars from the summer 2026 and the Horse
Gulch area.
- http://www.weather.gov/safety/flood
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Alert data: U.S. National Weather Service / NOAA · Translation: WeatherTranslate™