The flames from the so-called 'Mountain fire' came within sight of Palm Springs Friday, fueled by thick brush that hasn't burned in 35 years. NBC's Miguel Almaguer reports.

LOS ANGELES - Firefighters raced on Friday to buttress defensive lines against a fierce blaze roaring for a fifth day near the scenic mountain resort of Idyllwild in Southern California, as thunderstorms in the forecast threatened to hamper efforts to subdue the flames.

The so-called Mountain Fire has already burned across more than 24,800 acres of dry brush and timber and forced the evacuation of Idyllwild after destroying seven nearby homes and other property in the rugged San Jacinto range, authorities said.

The blaze, which ranks as federal fire managers' top priority among 17 large wildfires across several western states, erupted on Monday afternoon in the San Bernardino National Forest, about 100 miles east of Los Angeles.

The San Jacinto range overlooks Palm Springs, Cathedral City, Rancho Mirage and several smaller desert towns to the northeast, but the main threat has been to the village of Idyllwild, a popular vacation destination in the mountains.

The mile-high community, known for its hiking trails, rock climbing and arts and music scene, was ordered evacuated on Wednesday, along with the neighboring town of Fern Valley and surrounding parks and campgrounds as flames advanced.

Combined with smaller communities ordered to vacate earlier in the week, authorities estimated that some 6,000 residents, campers and other seasonal visitors had been chased out by the fire. Some 2,200 homes remained under evacuation on Friday.

Lt. Gov. Gavin Newsom declared a state of emergency for Riverside County on Friday.

Citing the potential for "extreme fire growth" on Friday afternoon, the county Sheriff's Department issued an evacuation warning to residents of Pine Cove, adjacent to Idyllwild, urging them to be ready to flee at a moment's notice.

The famed Palm Springs Aerial Tramway, a rotating gondola that carries visitors from the desert floor to an observation post near the San Jacinto peak, also has been closed down because of heavy smoke.

Palm Springs safe for now

But Rico Smith, a spokesman for the U.S. Bureau of Land Management, said the fire's northern edge was still about six miles from the center of Palm Springs, a city of 46,000 known for trendy shopping and restaurants that was once a playground for Hollywood stars like Frank Sinatra and Bing Crosby.

With wide stretches of sparse, desert vegetation separating the mountain foothills from Palm Springs and nearby communities, those towns were not in imminent danger, Smith said.

On the mountain, fire crews continued to reinforce a defensive buffer zone along a high ridge line between the western flank of the blaze and Idyllwild. One favorable factor for much of the week has been relatively calm winds, although officials had feared that thunderstorms forecast for later Friday might complicate efforts to keep flames at bay.

The fire has now grown large enough to create its own potentially hazardous weather. Towering columns of smoke and ash spewed from the blaze can breed storm activity by themselves, fire officials said.

If those columns rise high enough, they can form ice clouds that could eventually force the smoke plumes to collapse, unleashing down drafts that can push the fire in numerous directions.

An incident report Friday evening said the blaze was 15 percent contained. No injuries have been reported, but seven residences were destroyed on Tuesday along with five commercial structures, more than a dozen outbuildings and several vehicles. The cause of the fire remained under investigation.

Experts say this year could see one of the worst U.S. fire seasons ever. In recent weeks, a Colorado wildfire ranked as that state's most destructive on record ravaged more than 500 homes and killed two people. In Arizona, 19 members of an elite "hotshot" crew died while battling a separate fire on June 30.

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