YOSEMITE NATIONAL PARK, CALIF., AUG. 12 -- Lightning fires have burned more than 200,000 acres of California forest in the last week, and experts said today it could get get "much, much worse" because of the lengthy drought.

In Yosemite National Park, closed to tourists since Friday, two fires have burned more than 15,000 acres. Flames were within two miles of the Merced Grove, a stand of giant sequoias, and within two miles of the Badger Pass ski area.

Fires also burned today in parts of Alaska, Idaho, Oregon, Utah and Washington state, said the Boise Interagency Fire Center in Idaho; a fire in south-central Montana was controlled late Saturday. The national firefighting command center said nearly 20,000 firefighters were at work on fires that had covered 856,000 acres, more than half of that acreage in Alaska.

The Army has begun firefighting training for about 2,800 soldiers at bases in Washington state and Colorado. They should be available for duty in western states by midweek.

California's worst fire was in Tehama County about 200 miles northwest of Yosemite. In the Sequoia National Forest, a fire has burned over 24,000 acres and firefighters worked to protect the communities of Kernville and Alta Sierra.

"The 200,000-acre figure for the state is probably pretty conservative," said Karen Terrill of the California Forestry Department. "What I hear the experts saying is that this could get to be much, much worse."

In Yosemite, firefighters took special precautions to protect the sequoia trees, some of them 2,000 years old, in Merced Grove. This included cleaning up forest debris in the area and treating the trees with a fire retardant.

But the thick-barked sequoias have lived through other fires, Terrill noted, and probably could make it easily through another.

The Yosemite fires were about 10 miles west of Yosemite Valley, the heavily visited site of Half Dome, El Capitan and Bridalveil Falls.