By Dan Whitcomb
LOS ANGELES (Reuters) - A wildfire burning at the western edge of Yosemite National Park that killed a firefighter over the weekend has injured two more, officials said on Wednesday, as crews sought to gain a measure of control over the flames ahead of dangerous thunderstorms.
One firefighter broke a leg while battling the Ferguson Fire and remained hospitalized on Wednesday, U.S. Forest Service spokesman Richard Egan said. A second was treated for heat-related illness and released from a local hospital.
The United States is facing an unusually active wildfire year, with some 3.3 million acres (1.3 million hectares) already charred this year, more than the year-to-date average of about 3 million acres (1.2 million hectares) over the past decade.
The California injuries came as crews made a major push to cut containment lines around the conflagration before thunderstorms forecast for this week further whip up the flames.
"These next 48 hours are going to be pretty critical for us in terms of containing the fire," Egan said, adding that lightning strikes could also touch off new hot spots.
The blaze has blackened more than 17,300 acres (7,000 hectares) of forest in California's Sierra Nevada mountains and had burned to within a few miles of Yosemite's western boundary as of Wednesday afternoon, prompting closure of State Route 140 and a park entrance.
Fire managers have issued evacuation orders or advisories for the mountain communities of Jerseydale, Mariposa Pines, Clearing House and Incline.
Complicating firefighting efforts was an inversion layer of thick black smoke, visible for miles, that has prevented water-dropping aircraft from flying into narrow canyons.
That inversion layer was expected to partly clear on Wednesday as the storm approached, allowing aircraft to make runs at the fire, Egan said.
Firefighter Braden Varney was killed on Saturday when a bulldozer he was using to cut a fire break overturned, according to the California Department of Forestry and Fire Protection.
Varney is the 10th U.S. wildland firefighter to die in the line of duty this year, according to National Interagency Fire Center data.
California has had its worst start to the fire season in a decade, with more than 220,421 acres (89,201 hectares) blackened and six major wildfires burning statewide as of Wednesday.
In Oregon, where the Substation Fire has burned more than 36,000 acres since breaking out on Tuesday, Governor Kate Brown declared an emergency, prompting authorities to issue evacuation from communities along the Deschutes River.
The risk of large wildfires is set to ease in much of the Southwest and Rocky Mountains due to expected summer rains, but remains high in California through at least October.
(Reporting by Dan Whitcomb; Editing by Scott Malone and James Dalgleish)