A separate Winter Storm Watch issued by the National Weather Service in Great Falls extends the heavy snow threat through 6 a.m. Monday, October 12th, covering the Big Belt, Bridger, and Castle Mountains along with the Gallatin and Madison county mountain ranges and the Centennial Mountains to the south.
The NWS is forecasting six to twelve inches of accumulation along the Big Belt Mountains — which rise directly east of Helena — and the same range above 7,000 feet in Madison and Gallatin county terrain. Winds could gust to 45 miles per hour. The watch begins Saturday evening and runs nearly a full day longer than the watch covering the Helena Valley and western passes.
The Big Belts are visible from most of Helena and serve as a reference point residents use to read incoming weather. Snow accumulating in that range at these levels over a multi-day period will affect drainage patterns and road conditions on routes connecting Helena to the Smith River corridor and points east.
Residents with property, hunting access, or travel planned in any of these ranges this weekend should plan for the possibility that conditions deteriorate faster than the watch timeline suggests. Early-season wet snow at these elevations can compact quickly on roads and remain well after valley snow melts. The NWS Great Falls office will issue updated advisories as the storm system develops.