Snow started Monday night in Colorado’s mountains and will continue throughout the week, likely making its way into the Denver area on Friday, according to the National Weather Service.

Colorado’s mountain roads, including Interstate 70 at the Eisenhower-Johnson Tunnel and Berthoud Pass, were already snow-covered Tuesday morning, according to the weather service.

“With more snow to come throughout the day, a Winter Weather Advisory was issued for the Front Range Mountains,” forecasters said.

That advisory will be in effect until 8 p.m. Tuesday for parts of Jackson, Larimer, Boulder, Grand, Gilpin, Clear Creek, Summit and Park counties, including Rocky Mountain National Park. Additional snow accumulations between 6 and 14 inches are possible on Tuesday, forecasters said in the alert.

As of Tuesday, the weather service’s snow forecasts included:

• 2 inches on I-70’s Vail Pass, with up to 3 inches possible
• 3 inches in Winter Park, with up to 4 inches possible
• 4 inches in Eldora and on U.S. 6’s Loveland Pass, with up to 5 inches possible
• 4 inches on U.S. 40’s Berthoud Pass near Winter Park, with up to 7 inches possible
• 5 inches at Bear Lake in Rocky Mountain National Park, with up to 7 inches possible
• 6 inches on U.S. 34’s Milner Pass in RMNP, with up to 8 inches possible
• 7 inches on Colorado 14’s Cameron Pass near Fort Collins, with up to 8 inches possible
• 9 inches on Mount Zirkel, the highest summit of Colorado’s Park Range of the Rocky Mountains, with up to 11 inches possible

“Travel could be very difficult,” weather service forecasters stated in the winter weather advisory. “The hazardous conditions will impact the Tuesday morning and evening commutes.”