Oregon's biggest forest fire of the year, a virtual firestorm of a blaze that was creating its own weather, threatened to force evacuation of a campground-filled crater Tuesday. Nearly 300 more firefighters were on their way to the blaze.

Smoke-filled skies prompted dozens of central Oregon visitors to flee campgrounds near Bend on Monday, and officials said there was a 90 percent chance that resorts and summer homes in the Newberry Crater, 5 miles in diameter, would be evacuated Tuesday.

"There are only two ways in and out of the area, one right across the head of the fire," Forest Service spokesman Greg McClarren said.