The National Weather Service office in Great Falls issued a Flash Flood Watch beginning early Thursday morning, September 18, covering portions of central and southwest Montana through midnight Saturday. The watch specifically flags the Horse Gulch area and burn scars left by summer 2026 wildfires as zones of elevated concern, where heavy rain can trigger not just flooding but debris flows with little warning.
The watch covers a broad swath of terrain familiar to Helena-area residents and outdoor users: the Big Belt, Bridger, and Castle Mountains; the Elkhorn and Boulder Mountains; the Little Belt and Highwood Mountains; and portions of the Gallatin Valley to the southwest. These are areas where drainage patterns, steep terrain, and fire-altered soil conditions can accelerate water movement dramatically compared to unburned ground.
Burn scars are particularly dangerous during heavy rain events because the fire-hardened soil repels water rather than absorbing it, sending runoff cascading downhill faster and with more debris than a normal storm would produce. The summer 2026 fire season left multiple scars across the region, and NWS forecasters flagged those areas by name in the watch language — an indication that forecasters consider them a primary concern during this weather system.
Residents living near drainages, gulches, or below any of the named mountain ranges should monitor NWS Great Falls updates closely and be prepared to move quickly if conditions deteriorate. Flash flooding can develop faster than official warnings can be issued. The watch runs through midnight Saturday, September 20.