Update, noon Saturday: Firefighters are gaining ground in their battle to contain the Washington Fire, burning in Alpine County southeast of Lake Tahoe.

Fire managers reported Saturday that while the acreage of the fire has grown to 17,622 acres (about 28.5 square miles), the blaze is now 29 percent contained. The firefighting force assigned to the blaze has grown to more than 1,100.

Local officials have lifted evacuation alerts in the town of Markleeville and nearby Grover Hot Springs State Park.

Due to a growing threat of thunderstorms, the National Weather Service has issued red-flag warnings for the area around the fire -- and for the entire Sierra Nevada north of Yosemite National Park and throughout the mountains of Northern California. The warnings also cover the western two-thirds of Oregon and the western half of Washington state.

The major threat posed by the thunderstorms is dry lightning that can be counted on to start fires. Thunderstorms that swept across drought-stricken Northern California in June 2008 sparked what was later termed a "fire siege" -- about 1,750 individual blazes that burned 1.2 million acres and killed 13 firefighters.

Update, 11:05 a.m. Thursday: Fire crews have made progress building a protective line between the Washington Fire and the town of Markleeville in Alpine County. Total area burned: 17,205 acres (about 28 square miles). Containment: 10 percent. About 900 firefighters, aided by three air tankers and a dozen helicopters, are working the fire.

Update, 10 p.m. Tuesday: The updated stats, as of Tuesday evening, on the Washington Fire burning near Markleeville in Alpine County: 16,553 acres (26 square miles) burned. The fire has burned to within about a mile and a half of the town of 200, which is also the county seat. Incident commanders directing the force of 500 or so firefighters on the ground and a squadron of air tankers and helicopters drawn from around the West have made protecting Markleeville their top priority.

In their evening news update, fire managers said crews made "excellent progress" in strengthening fire lines near the town and establishing 5 percent containment. Markleeville residents remain on alert to leave the area, though no evacuation has been ordered.

Fire crews are also trying to keep the fire from reaching the site of the Leviathan Mine, off of Highway 89 near Monitor Pass. The former open-pit sulphur mine is a Superfund site that has been leaking acid-laced water into nearby creeks for decades.

Weather conditions have improved somewhat in the area, with winds dropping and humidity rising. The major issue in the forecast over the next several days is the increasing chances of thunderstorms by the weekend. Temperatures in the Markleeville, elevation roughly 5,500 feet above sea level, are forecast to hit the mid-90s by Friday.

Update, 12:15 a.m. Tuesday: The Washington Fire burning across the rugged terrain of Alpine County, southeast of Lake Tahoe, doubled in size on Monday.

Fire managers said the blaze, believed to have started with a lightning strike last Friday, has burned about 15,000 acres, or roughly 24 square miles. (In Bay Area terms, that's equivalent to half the area of San Francisco, a little less than a third of Oakland and just a sliver -- a little less than one-seventh -- of San Jose.)

Fire managers also reduced their estimate of containment -- from 10 percent to 0 percent -- because of strong erratic winds that posed a danger to the 500 or so firefighters working to stop the blaze's spread toward Markleeville. Severe drought conditions and continuing low humidity also continue to play a part in the fire's rapid spread.

At its closest point, the fire is about four miles southeast of Markleeville, a town of about 200 and seat of Alpine County. The Sheriff's Office there has put residents on notice that an evacuation may be ordered.

So far, the fire is not believed to have burned any structures, but it has produced thick columns of smoke that have affected communities to the east and northeast, across the Nevada state line.

Update, 4:40 p.m. Monday: The Washington Fire near the Alpine County town of Markleeville has now burned 9,500 acres -- about 15 square miles -- and is just 10 percent contained.

Jenny Ramella, a spokeswoman for the Sierra Front Interagency Dispatch Center in Minden, Nevada, said that about 500 firefighters are expected to be on the lines Monday afternoon. They're focusing their efforts on the northwest flank of the blaze, the edge closest to Markleeville.

The fire, which has burned across the junction of Highways 4 and 89 about 4 miles from the town, has prompted what the sheriff's office is calling a "pre-alert" that an evacuation may be ordered.

Ramella said the fire is most active near Heenan Lake, near the point where Highway 89 crosses Monitor Pass. She said weather conditions "are a lot better than yesterday," when winds gusting over 40 mph and humidity under 10 percent pushed the fire toward Markleeville.

Original post (11:20 p.m. Sunday): The weekend brought red-flag fire conditions to the eastern slope of the Sierra south of Lake Tahoe -- and the hot, dry, windy weather helped whip a small fire that started Friday afternoon into a blaze that on Sunday sped through canyons and across ridges toward the popular summer tourist spot of Markleeville.

The Sierra Front Interagency Dispatch Center, the federal agency coordinating response to the blaze, reported Sunday evening that the Washington Fire had burned 6,500 acres -- about 10 square miles -- and had shut down two state routes across the mountains: Highway 89 across Monitor Pass and Highway 4 across Ebbetts Pass.

The fire was driven by ridgetop winds that topped 40 mph during the day Sunday and humidity in the single digits. Sierra Front's Sunday night statement said the highest priority for fire crews was defending Markleeville, 20 miles southeast of Lake Tahoe.

Campgrounds along Highway 4 south of Markleeville up to Ebbetts Pass were evacuated, and people in the town were notified they might have to leave. As of 10 p.m. Sunday, the Alpine County Sheriff's Office said via Facebook the fire was "very active," though not currently moving directly toward the town.

Markleeville is a town of just 200 or so and is the seat of Alpine County, which, with about 1,200 residents, is California's least populous. But the town is near a popular state park, Grover Hot Springs, and the surrounding area attracts campers, fishers, hikers and cyclists.