by Carlos E. CastaƱeda

DONNER PASS (CBS SF) — Rescuers were searching for a San Francisco snowboarder who was missing in the northern Sierra after a snowstorm, according to authorities.

The Nevada County Sheriff’s Office said 25-year-old Abraham Finkelstein and his father were back-country snowboarding in the Castle Peak Area of Donner Pass Monday afternoon around 5:00 p.m. when they became separated.

Sheriff Keith Royal said the two were hiking to Peter Grubb Hut, three miles north of I-80 at Donner Summit, but decided to turn around when the weather began to deteriorate.

Back country snowboarding or skiing involves hiking up a mountain, then skiing down, according to Sheriff’s Sgt. Justin Martin. The Castle Peak area is across Interstate 80 from Boreal Ridge Ski Park.

Finklestein’s father was able find his way back to their car and called authorities when his son did not return.

20 volunteers have been searching for him since last night along with search teams from Nevada and Placer counties, using cross-county ski teams and snowmobiles.

The Nevada County Sheriff’s Office said it has also requested additional resources through the State of California Office of Emergency Resources.

The command post was located in the parking lot of Boreal ski area.