Chain laws for commercial vehicles are in effect for Coal Bank and Molas passes between Durango and Silverton on U.S. Highway 550 as a fast-moving storm brings snowfall to the region.
Chains or alternative traction devices are required for all commercial vehicles, including buses.
Passenger vehicles are required to have snow or mud/snow tires, use chains/alternative traction devices or have a four-wheel/all-terrain vehicle.
Dennis Phillips, a meteorologist with the National Weather Service in Grand Junction, said the storm system will hit hardest in the northern parts of Colorado, near Vail and Steamboat Springs.
Weather forecasters were calling for only a couple of inches of snow late Wednesday and early Thursday in the high country of the San Juan Mountains, which may affect travel over mountain passes.
The National Weather Service predicts patchy blowing snow overnight, with a couple of inches accumulating at higher elevations. The wind chill in the high country could dip as low as minus 15 degrees.
In Durango, no significant snowfall is expected, though Phillips said gusty winds could last through Thursday morning.
Thursday is forecast to be sunny with a high near 40 degrees in Durango.