Firefighters and equipment were redistributed Friday to prepare for high wind with gusts forecast up to 60 mph, while forest fires kept two small towns evacuated and the oldest national park mostly closed to visitors.
Saturday "may be the worst day since this entire episode began," U.S. Forest Service official Brian H. Avery said Friday. "We're trying to prepare for that today, because tomorrow will be too late to prepare for it."
Meanwhile, about 300 miles to the northwest in Montana's Glacier National Park, a firefighter was killed by a falling tree, becoming the fifth person to die in wildfires that have charred 3.8 millions acres of forests and rangeland in the West this year.
In Washington, President Reagan signed emergency legislation Friday that clears the way for Canadian firefighters to join the battle against the Western blazes.
The measure authorizes the U.S. Forest Service to reimburse the Canadian government for the cost of mobilizing its firefighting personnel and equipment. Congressional staffers have said 35 Canadian planes could be put into action as soon as Reagan signed the bill.
Meteorologists had been predicting that an advancing weather front would produce extremely high winds during the weekend in Yellowstone but might also bring some rain or snow by Monday.
A revised forecast Friday no longer anticipated any rain or snow, Avery said at a briefing on fire conditions.
"We see no direct relief in sight, and we are anticipating major fire activity," Avery said, adding that "probably in excess of 150,000 acres" could be burned by wind-whipped flames.
The Yellowstone fires have scorched nearly 1.2 million acres in and around the park, including adjacent areas in Idaho, Montana and Wyoming. The cost of fighting the fires has reached $76.1 million for the Greater Yellowstone Area, Dempsey said.
Smoke from the Yellowstone fires has drifted as far east as Chicago and as far south as Los Angeles and often is visible on satellite weather photographs.
Smoke conditions were worst in the Wyoming counties bordering the park.
In Montana, a dead tree on the perimeter of a 527,500-acre fire burning in Glacier Park and the Flathead National Forest toppled over on five firefighters, killing one and sending four others to a hospital with broken bones, National Forest Service spokesman Craig Hess said.
In Yellowstone, emphasis shifted from the Old Faithful complex, which should be "in reasonably good condition" because Wednesday's firestorm burned an area around the perimeter that should provide a buffer against any further major burning.