* WHAT...Heavy snow possible. Total snow accumulations 6 to 12 inches except between 12 and 18 inches over the mountains possible.

* WHERE...Camas Prairie, Boise Mountains, and West Central Mountains.

* WHEN...From this evening through Friday morning.

* IMPACTS...Roads, and especially bridges and overpasses, will likely become slick and hazardous. Travel could be very difficult to impossible.