Update, 12:15 p.m. Wednesday, June 28: One of Yosemite National Park's iconic byways -- the Tioga Road, aka Highway 120 across Tioga Pass -- will reopen Thursday after crews cleared it of monumental volumes of snow and ice left over from one of the snowiest California winters in decades.

Yosemite officials say the high-country road will be open to pedestrians and all vehicular traffic, including bicycles, at 8 a.m. Thursday.

But the opening comes with a long series of caveats. In addition to being alert to water, mud, debris and maintenance vehicles along the road, park administrators said in a press release, visitors should be aware "there will be minimal services available along the Tioga Road for several weeks."

To wit:

• There will be no drinking water.
• There will be no lodging or food service.
• There will be no mobile phone service, and 911 emergency calls "will not be operational."
• There's no gasoline available along the road. The nearest fuel will be to the east in Lee Vining, on U.S. 395, and to the west at Crane Flat.
• Sanitation facilities are limited, and visitors are urged to use the vault and portable toilets located along the roadway to help protect water quality in the Tuolumne River watershed.
• Tamarack Flat Campground is the only campground that is currently open along Tioga Road. This campground is first come, first served and fills early in the day.

Yosemite is also advising those planning to travel in the park's back country from the Tioga Road that they'll experience conditions that are anything but summerlike:

"Anyone planning to hike or backpack near Tuolumne Meadows and in all high elevation areas of Yosemite should be prepared for winter hiking and camping conditions. Trails are still impacted by snow and ice. River crossings are high and swift moving. There are several high water areas currently impacting the Pacific Crest Trail (PCT) and the John Muir Trail (JMT) in Yosemite National Park. Trail conditions may vary at any time."

This year's opening is the latest since 1998, when travelers were barred until July 1. The latest opening ever? July 8, 1933 -- before the road was paved.

At 9,943 feet above sea level, Tioga is the highest of the half-dozen or so principal highway routes across the Sierra (from north to south, they include Donner, on Interstate 80; Echo Summit, on U.S. 50; Carson, on Highway 88; Monitor, on Highway 89; Ebbetts, on Highway 4; and Sonora, on Highway 108).

Original post, June 15:

Rich Pedroncelli and Brian Melley
Associated Press

YOSEMITE NATIONAL PARK — There may be no more potent reminder of this year's humongous snowfall than the plows still clearing roads that snake across California's highest mountains as summer approaches.

Crews have been digging, plowing and blasting for months — and the work is not finished, though an approaching heat wave could speed up the process.

"We're almost at the middle of June and we still have lots of passes that aren't open," said Florene Trainor, a spokeswoman for Caltrans.

Few roads traverse the Sierra Nevada, and mountain passes are typically open by Memorial Day.

The road that crosses the Sierra through Yosemite, Highway 120, remained closed this week as crews dig out from snows that topped 20 feet and drifted well over 50 feet.

On a recent day, the park's entrance station at 9,945-foot-high Tioga Pass was buried in snow.

But the serenity of the Sierra Nevada, with birds chirping beneath snow-crested peaks that tower above 13,000 feet, was shaken by the roar and beep of plows, excavators and massive machines carving through 15-foot snowbanks and moving giant blocks of snow. Big snow blowers sent plumes arcing through the air and off the side of the road.

The air is clean and views are stunning, but working here is not for the faint of heart as drivers maneuver large machines along narrow ribbons that appear to be suspended above an abyss. Helicopter footage shot this spring for Caltrans showed the small margin for error in places where the road clings to cliffs and then vanishes under a white blanket where the path is obscured.

"It's spooky, it's nerve-wracking ... especially when you can't see the road. You're on a big sled," said Clint Weier, a maintenance superintendent with Caltrans. "Some of our operators up here have had some wow factors."

Avalanches stampede down granite walls, taking trees and rocks with them. In one section of the highway, tree trunks and branches protrude from the snow, evidence of a previous snowslide. Once workers have set off explosive charges to deal with the avalanche danger, rockslides remain a threat.

On the steep section of Highway 120 east of the park entrance, slides and the sheer weight of the snowpack have crushed guardrails that are the only barrier between motorists and a canyon that drops hundreds of feet off the edge of the road.

A Yosemite plow driver was killed by an avalanche in 1995, and now maintenance workers in the park complete avalanche safety courses to work on the road, park spokesman Scott Gediman said.

The park's official advisory on Tioga Pass notes that the road is typically closed through May, but it usually opens later after a snowy winter. With no date set for the road to be completely cleared, this year's opening is likely to be the latest since at least 1998, when the pass opened July 1.

Just to the north of the park, Highway 108 across Sonora Pass opened Tuesday. Highway 4, the narrow ribbon of pavement that mounts Ebbetts Pass south of Markleeville, remains closed for post-winter repairs. And much farther north, in Lassen Volcanic National Park, deep snow still buries Highway 89.

The snowpack presented an additional challenge this year because it was heavily saturated with water. The dense and frozen snow was harder to cut through, heavier to move and broke equipment, said Paul Jensen, a Caltrans plow driver.

Jensen has been working overtime all spring to get the road into Yosemite open and hasn't minded working weekends. He considers it a labor of love.

"Twenty years and I'm still not tired of it," Jensen said. "It's my favorite time of the year."