* WHAT...Heavy snow expected. Total snow accumulations between 4 and 19 inches. In the central Idaho mountains, including the towns of Stanley, Ketchum, and Hailey, amounts will range from 5 inches at the lowest elevation to more than 24 inches on the very highest peaks. For the areas bordering Utah, expect 1 inch at the lowest elevations to more than 20 on the highest peaks in that area. In the eastern and southeastern highlands, snowfall will range from 3 inches at lowest elevation to more than 20 inches in passes heading to Wyoming.

* WHERE...Big Lost Highlands/Copper Basin, Sawtooth/Stanley Basin, Sun Valley Region, Wood River Foothills, Big Hole Mountains, Centennial Mountains - Island Park, Teton Valley, Bear River Range, Blackfoot Mountains, Caribou Range, Franklin/Eastern Oneida Region, Marsh and Arbon Highlands, Raft River Region, and Southern Hills/Albion Mountains.

* WHEN...From 5 AM Thursday to 5 PM MST Friday.

* IMPACTS...Roads, and especially bridges and overpasses, will likely become slick and hazardous. Travel could be very difficult to impossible. The hazardous conditions could impact the Thursday morning and evening commutes.