Slightly cooler temperatures and a bit more moisture in the air has decreased the intensity of the twin fires nearly identical in size burning in northeastern Jackson County, but inbound thunderstorms have crews on alert for the new blazes lightning could bring. 

A red flag warning is in effect from noon to 10 p.m. Tuesday, which comes with the potential of winds that could hasten the spread of existing wildfires and new lighting-sparked fires.

"Gusty thunderstorm winds could contribute to fire spread. Even with some rainfall, initial attack resources could be overwhelmed and holdover fires are possible," a Weather Service bulletin reads.

The Blanket fire, which started about nine miles northeast of Prospect, is 4,739 acres in size, according to public information officer Shane Rossbach. The Spruce Lake fire, burning in the western boundary of Crater Lake National Park, is at 4,681 acres. Fire personnel received the revised acreage following late-night infrared scans from an aircraft.

Smoke from both fires kept air quality at "moderate" for much of Jackson and Josephine counties Tuesday. The Oregon Department of Environmental Quality issued an air quality alert because of the fluctuating pollution levels.

Firefighters are further along on the Blanket fire, which is 31 percent contained and continues to burn eastward into an old burn area with plenty of dead timber and snags. Additional growth on the south and southwest flanks has slowed.

"They've really worked to tie that end up," Rossbach said.

Spruce Lake, a few miles north of Blanket, is 13 percent contained. Crews continue to shore up the northern and southern flanks in burn scar areas. Some spot fires ignited in the lake's caldera, though crews snuffed those, Rossbach said. A Level 1 Evacuation notification, which means park visitors and residents should be aware they could be asked to leave, is in place for Rim Village and the park's headquarters area, according to fire officials.

West Rim Drive remains closed from Rim Village to North Junction, as does the Pacific Crest Trail from the park's southern boundary to Highway 62, and from the intersection of the Dutton Creek Trail north to the North Entrance Road, according to park public information officer Marcia McCabe. The Union Peak, Stuart Falls, Pumice Flat, Boundary Springs, Bald Crater Loop, Bert Creek, Discovery Point and Lightning Springs trails are closed inside the park, as is the Rim Trail from Discovery Point to North Junction.

— Reach reporter Ryan Pfeil at 541-776-4468 or rpfeil@mailtribune.com. Follow him at www.twitter.com/ryanpfeil.