At least one man died when the slide rolled through Rumble Gully, which is in a U.S. Forest Service wilderness area that borders the Mount Baker Ski Area about 45 miles east of Bellingham.
The body of snowboarder 19 year-old Justin M. Parker was recovered Sunday from beneath 20 feet of snow.
A second man, Sean Riches, 25, believed to be a skier, is still missing.
Whatcom County Deputy Ron Peterson said the avalanche was "just a small amount of what's ready to fall."
About 20 feet of snow had fallen in the area over the past 12 days, so going outside the maintained ski area was like "playing Russian roulette," Peterson said.
In wilderness areas, "no avalanche-control work is allowed or done," ski area spokeswoman Gwyn Howat said Monday.
Signs and a rope line warn those venturing into the area, she said. The sign tells hikers, snowboarders and skiers that there will be a $500 minimum fine for any rescue effort, and notes that such efforts may not be possible.
The slide was estimated to be moving "close to 200 miles per hour" when it hit, Howat said. It took only a few seconds for the slide to bury the slope and everything in its path.
One witness reported that he was rewinding a roll of film, a process that takes about five seconds, when he looked up and saw the avalanche start.
"In the time it took his film to rewind," said Howat, "it was over."
Search efforts were suspended Sunday due to extreme avalanche danger.
"The search will resume once avalanche conditions stabilize," Howat said. When that is "entirely depends on the weather," she said, noting that more snow is expected in the next few days, topping off 690 inches of snowfall so far this season.
"It doesn't look too promising for conditions to improve any time relatively soon," she said.
In many resorts, snow sports are limited to maintained areas and those caught out of bounds may lose their lift tickets.
But at Mount Baker, skiers and snowboarders may go outside the boundaries but only at their own risk.
"It's public land, so public access is available," said Howat, though boundaries and safety concerns are prominently noted.
"People who go there clearly make the choice to leave the ski area and enter into the back country," she said. "It's alluring in some cases."
Doug Freymeyer, operations leader for Bellingham Mountain Rescue, said the avalanche was the largest he had ever seen on the eleven thousand-foot peak.