Editor's note: This updates with decision from the National Park Service headquarters in Washington that the Blue Ridge Parkway would remain open, though facilities and campgrounds along it would be closed in the event of a government shutdown, adds comments from the Coalition of National Park Service Retirees.

With Congress at odds over whether to pass a Continuing Resolution to keep the federal government in business, National Park Service and concessions staff were preparing Monday for the possible closure of the National Park System.

Exactly what "closure" means, though, differs across the park system.

In general, under guidelines released last week by the Interior Department, day users in the parks would be told to immediately leave the parks, while those staying in campgrounds or lodges would have 48 hours to leave.

However, the Natchez Trace Parkway will remain open along its 444 miles between Natchez, Mississippi, and Nashville, Tennessee. But park visitor centers, campgrounds, and interpretive pullouts would be closed.

Additionally, the Blue Ridge Parkway between Shenandoah National Park in Virginia and Great Smoky Mountains National Park in North Carolina would be remain open to traffic, though Parkway facilities, campgrounds and overlooks would be closed to traffic.

At Death Valley National Park in California and Nevada, California 190 would remain open across the park, as would the road to Scotty's Castle, as it's a through-road in the park. But most other roads and park facilities would be closed, said Abby Wines, the park's acting public information officer.

The Furnace Creek Ranch and Furnace Creek Inn both would remain open, as they sit on private property, as does the Panamint Springs Resort, she said. The facilities at Stovepipe Wells are owned by the Park Service, and so would be closed in the event of a government shutdown, said Ms. Wines.

At Grand Teton National Park in Wyoming, while the main highway through the park -- U.S. 89/26/191 -- would remain open between the south entrance 4 miles north of Jackson and the east entrance 2 miles east of Moran Junction, all other park roads would be closed.

What was uncertain Monday, though, was the fate of any backcountry travelers in the parks.

"At this point in the season, we have limited backcountry use, so that's not expected to be a significant challenge," said Grand Teton spokeswoman Jenny Anzelmo-Sarles. She didn't know, however, whether rangers would head into the backcountry to escort out any permitted backcountry travelers.

Officials with the Appalachian National Scenic Trail could not immediately be reached to explain what they might do with thru-hikers on the trail. In Alaska, the farflung nature of the parks in that state made it impossible to shutter all the Park Service landscape, agency officials said.

"There’s a recognition, with millions of acres up there and more access points than we could count, that it’s not a hard closure," Park Service spokesman Mike Litterest said from the agency's Washington, D.C., headquarters.

On the National Mall in Washington, the various national memorials would be closed to visitors, he said, though access to the sprawling greenway would remain open.

National seashores, said Mr. Litterest, also would lower their gates across entry points.

Across the park system, law enforcement rangers were expected to remain on duty and patrol the roads. However, even that could be a challenge in parks such as Death Valley, where there are just nine law enforcement rangers for the park's 3.3 million acres.

Lodging concessionaires were watching the situation, but not ready to say how they would handle a shutdown that could require thousands of guests and concessions employees to leave the parks.

"We are still hopeful the situation will be resolved, and we are monitoring it closely. The national parks at which Delaware North Companies Parks & Resorts operates remain fully open today," company spokesman Glen White told the Traveler in an email. "In the event of closures, we will provide more information regarding our plans."

Officials with the Coalition of National Park Service Retirees decried the possible government shutdown, condemning the "partisan politics currently risking a government shutdown, and jeopardizing the livelihood of nearly one million public servants, including thouands of National Park Service employees."

“The term 'non-essential' has been connected to National Park Service employees in many national news stories lately in the run-up to the government shutdown," said Coalition spokeswoman Joan Anzelmo. "Therefore, we want to take this opportunity to remind every American that if the potential shutdown occurs, it will require furloughing people who fight explosive wildfires, save lives in outdoor accidents, rescue injured climbers on mountain peaks, search for lost children, respond to terrorist threats, protect U.S. borders, and rush into places devastated by hurricanes, tornadoes, earthquakes, fires and floods to help their fellow man. NPS does this vital work and so much more day in and day out, year-round."

The closure of the park system would throw more than 21,000 employees out of work, and cost gateway communities as much as $30 million a day in lost revenues, according to estimates from the National Parks Conservation Association.

Across the country, a government shutdown would interrupt, if not cancel, vacations, and halt hunting in national preserves, while agencies like the Park Service would spend millions of dollars, collectively, to wind down and shutter operations.

"The exercise federal agencies must go through, first to gear up for a shutdown – and the costs to actually shut agencies and facilities down is estimated at more than one billion dollars," the retirees coalition said. "Then there is the gearing back up to restore the services and facilities to operational levels. This is a huge waste of taxpayer money and staff time."