Rescuers who were kept off the High Sierra for five days by winter storms managed to get to the wreckage of a light plane and found an 11-year-old boy alive, huddled in a sleeping bag near the bodies of his mother and stepfather.

Donald Scott Priest of Orinda, Calif., was found Friday in the rear of the craft, after having survived zero-degree cold since the plane crashed in a storm near Yosemite Jan. 4. His pants had frozen to his legs and his body temperature had dropped to 87 degrees.

The boy was listed in critical but stable condition yesterday, although doctors said he may lose a foot or part of his leg because of frostbite.

The deaths of his mother and stepfather, Ronald J. and Lee Vaughn, in the crash, and the discovery of three more bodies in Santa Cruz County, brought to 29 the number killed in storms that dumped up to 10 feet of snow on the Sierra Nevada and produced mud slides in lower elevations of Northern California.

The storms destroyed $280 million worth of residential and commercial property, state and local officials estimated. At least 6,023 homes were damaged and 439 destroyed, said Nels Rasmussen, chief administrative officer of the California Office of Emergency Services.

Yesterday, road crews were trying to reach the remainder of about 3,000 people who had been stranded a week by a snowfall up to 10 feet deep south of Lake Tahoe.

Across the Midwest, a blast of "extremely dangerous" Arctic air sent wind chills 70 degrees below zero, and foot-deep snows fell on some cities as the deep freeze spread eastward. Temperatures dropped as low as 46 degrees below zero at Embarrass, Minn.

A near-blizzard assaulted northeastern Ohio with more than a foot of snow east of Cleveland. Motorists were warned to stay off ice-glazed roads, especially Interstate 90 between Cleveland and Buffalo, N.Y., because of the possibility of a "white-out" with the wind chill factor at 30 below.