A member of the Midewin Interagency Hotshot Crew burns vegetation along a containment line to help control the fire within Shenandoah National Park. (Norm Shafer/For the Washington Post)

The massive wildfire tearing through the southern portion of Shenandoah National Park grew substantially Thursday and crossed over to the eastern side of Skyline Drive in several spots, a development that firefighters had been hoping to prevent. And smoke from the fire has drifted as far north as Washington’s southwestern suburbs, prompting concern from residents there.

The blaze, which is being called the Rocky Mount Fire, began Saturday afternoon and has consumed 8,000 acres of parkland, up from 5,600 on Wednesday. It has grown into one of the worst fires in the park’s 80-year history. The fire is 40 percent contained, but with no significant rain in the forecast, officials think the blaze will not be fully contained until next week.

Even as the fire grows and has shut down portions of Skyline Drive and the Appalachian Trail, National Park Service officials say they are confident that it can be managed, and the rest of the park’s 196,000 acres remain open to visitors. Communities that adjoin the park are not endangered, and no evacuations have been ordered. Small fires that jumped to the east of Skyline Drive on Thursday were quickly controlled by crews creating containment lines and utilizing water drops from helicopters, a Park Service official said.

Additional personnel arrived Thursday in Grottoes, Va., about 135 miles southwest of Washington, to join the federal response team that has made the volunteer fire department there its command center. Nearly 350 firefighters and support crew from around the country have been battling the blaze. Using leaf blowers, rakes, shovels and bulldozers, firefighters have established containment lines on the northern and western sides of the fire, hoping to get rid of leaves and debris that would fuel the flames.

A wind forecast model shows the likely trajectory of smoke Thursday afternoon. (D.C.-Baltimore National Weather Service)

Their priority continues to be preventing the fire from leaping out of the park’s boundaries and into the small communities that adjoin its western edge. But their efforts have been hampered by winds gusting to 25 mph, the rugged terrain and extremely dry conditions. Containment lines have not yet been fully established along the fire’s southern border, said John Miller, an incident commander with the Virginia Department of Forestry.

As of Thursday afternoon, there had been no serious injuries associated with the fire and no structures had been affected, said Lisa Wilkolak, a Park Service spokeswoman.

Smoke and ash have settled over nearby communities and extended as far west as Interstate 81 and Harrisonburg, home to James Madison University. Officials in neighboring Rockingham County issued a smoke alert to warn the 76,000 residents about poor visibility on roads, and state and federal officials continue to monitor air quality in the region.

Early Thursday, the wind switched directions and began pushing the smoke and fire to the north and northeast. Hazy skies and the smell of smoke drifted into the Washington region and could last into Friday before a cold front passes through later in the night. To prevent sending out firefighters on false alarms, authorities are asking people to refrain from calling 911 unless they see a fire burning.

Rain is approaching the Washington region on Friday along with a cold front, both of which will act to clear the air in Northern Virginia. Showers will help to clean the air of smoke particles, and winds will shift from the north and northwest behind the cold front by Saturday — good for clearing the air in the Washington region but bad for air quality south of the Shenandoah fire.