Up to 8 inches of snow is forecast Saturday over a string of high mountain passes under winter weather advisories from the National Weather Service. Forecasters warn that travel could be very difficult, and one office specifically warns that tire traction will be reduced. For anyone driving over a pass this weekend, the tread left on their tires may matter as much as the snow totals.
Snow Totals by Pass
All three advisories run from 2 a.m. ET to 11 p.m. ET Saturday:
- Southwest San Juan Mountains, Colorado (NWS Grand Junction): 4 to 8 inches above 9,000 feet, with locally higher amounts, covering Silverton, Molas Pass, Coal Bank Pass, Rico and Hesperus
- Eastern San Juan Mountains above 10,000 feet, Colorado (NWS Pueblo): up to 7 inches at Wolf Creek Pass and Cumbres Pass
- Tusas Mountains, New Mexico, including Chama (NWS Albuquerque): 3 to 6 inches above 9,000 feet, with locally higher amounts
Molas and Coal Bank sit on US 550 between Durango and Silverton, Wolf Creek carries US 160 east of Pagosa Springs, and Cumbres is on Colorado 17 near the New Mexico line. The Colorado Department of Transportation lists maximum grades of more than 7 percent on Molas, 6.8 percent on Wolf Creek, 6.5 percent on Coal Bank and 6.3 percent on Cumbres, which leaves little margin for worn tires on fresh snow.
Colorado’s Traction Law and Tire Tread
Colorado can put its Passenger Vehicle Traction Law into effect on any state highway when conditions call for it. Under CDOT’s rules, every vehicle then needs at least 3/16 inch of tread, plus one of the following: four-wheel or all-wheel drive, tires marked M+S, winter tires with the mountain-snowflake symbol, or tires with a manufacturer all-weather rating. Chains or an approved alternative traction device also satisfy the law.
The 3/16-inch minimum applies even to AWD vehicles, so a crossover running on worn all-season tires does not comply simply because power goes to all four wheels. That minimum is equivalent to 6/32 inch on a tread gauge, and it is worth measuring the inner, center and outer grooves, since tires rarely wear evenly. Drivers whose tires fall short need chains or an approved alternative traction device to comply.
Reduced Traction on US 64
The New Mexico advisory is quite specific: NWS Albuquerque says travel could be very difficult on US 64 between Tres Piedras and Tierra Amarilla, and adds that tire traction will be reduced, so drivers should leave more room to the vehicle ahead.
Colorado road conditions and any traction law notices are posted on COtrip. In New Mexico, the state’s road report is at nmroads.com or by calling 511.
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