The Colorado Department of Transportation cautioned drivers Sunday night that avalanche mitigation work will cause delays on U.S. Highway 160 at Wolf Creek Pass and in the U.S. 550 mountain corridor.

On Sunday, the threat of avalanches was rated “moderate” in the southern and northern San Juan Mountains, and “high” in Colorado’s central and northern Rockies.

Twelve to 18 inches of dense snow fell in the past 24 hours in the San Juans, the Colorado Avalanche Information Center said.

“This snow is drifting into slabs up to four feet thick especially on easterly facing slopes. With continued wind loading, natural avalanches can release and run long distances,” CAIC said.

Wolf Creek Ski Area reported at 5:20 p.m. Sunday that it received 18 inches of snow in the preceding 24 hours and 22 inches in the preceding 48 hours.

U.S. 160 at Wolf Creek Pass will be closed for avalanche mitigation beginning at 6 a.m. Motorists should expect a lengthy delay, CDOT said.Eastbound traffic will be stopped near the chain-up station at Treasure Falls, mile point 157. Skiers should arrive at this point before 6 a.m. in order to reach the ski area.

Westbound traffic will be stopped at the pass summit, mile point 167. Skiers traveling westbound will be able to reach the ski area throughout the day, since the closure point is west of the resort.

Avalanche work will take place on U.S. 550 at Coal Bank, Molas and Red Mountain passes. Motorists traveling between Durango and Ouray can expect lengthy delays most of the morning, beginning at 7 a.m., CDOT said.Northbound traffic will be stopped at Cascade, mile point 53. Southbound traffic will be stopped south of Ouray, mile point 92.