A low pressure storm system and associated atmospheric river of moisture will bring a period of moderate to heavy rainfall to the mountains west of Ketchum, Galena Summit, and Stanley. 1 to 2 inches of rainfall is expected, with locally higher amounts along and west of the spine of the Sawtooths, and lower amounts east of Idaho Highway 75. A couple thunderstorms are also possible, especially Monday afternoon. In addition, temperatures above freezing throughout the event will result in an additional 1 to 3 inches of liquid melting out of the high elevation snowpack. This combination of moderate to heavy rain and melting snow may result in strong rises and localized flooding along smaller creeks and streams, as well as localized rockfalls and landslides. Some backcountry roads and trails may become impassable. The period of greatest potential impacts is expected from 2 AM early Monday morning through 8 PM Monday evening. Anyone with plans in the backcountry and mountains in the Ketchum, Galena Summit, and Stanley corridor should monitor this situation closely and be prepared for hazardous conditions. Consider altering your plans to avoid being in the mountains or backcountry during this period. * WHAT. Flooding caused by rain and snowmelt is possible. * WHERE. Mainly backcountry areas west of Highway 75 including the Ross Fork Burn Scar. * WHEN. From midnight MDT tonight through Monday evening. * IMPACTS. Excessive runoff may result in flooding of rivers, creeks, streams, and other low-lying and flood-prone locations. Creeks and streams may rise out of their banks. Isolated mud and rockslides are possible. * ADDITIONAL DETAILS. - Rainfall amounts of up to 2 inches in the mountains west of Stanley and Ketchum combined with snowmelt. - http://www.weather.gov/safety/flood
