Editor's note: This updates with word that the Glacier Point Road will open Friday.

You can add another iconic national park road that won't be open for travel this Memorial Day Weekend: the Tioga Road in Yosemite National Park.

The same incredible Sierra snowpack that has the park's waterwalls plunging into the Yosemite Valley at full throttle also has clogged the high country through which the Tioga Road runs and made the chore of clearing the snow quite the burden this year. Also slow to open this year will be the Glacier Point Road, park officials note.

While officials said earlier this week that they had no estimated opening date for either road, late Wednesday they announced that the Glacier Point Road would open at noon Friday for traffic.

"There will be limited visitor services available at Glacier Point. Vault toilets will be available, and there will be no running water. There is no projected opening date for the Bridalveil Creek Campground," a park statement said. "The roadway may be wet due to melting snow and wildlife may be present on or near the road. Visitors are urged to drive with caution while in the park. The Glacier Point Road is subject to unexpected and temporary closures due to unpredictable spring storms that may produce snow at the
higher elevations of the park."

For some reference, last year the Tioga Road opened June 5 and the Glacier Point Road on May 29, according to park records. Back in 1998 neither road was ready for traffic until July 1.

As of last Sunday, park crews had plowed from May Lake to May Lake Pit on the Tiogra Road, where snow drifts are 15 feet and deeper. "Additionally, as of May 20, Mono County Public Works and Mammoth Mountain crews have plowed to 3.8 miles from Tioga Pass," the park's website noted. "Mammoth Mountain is using snowcats to expedite the process."

Once plowing of the Tioga Road is completed, additional work must be completed before the road can safely be opened.

Factors affecting plowing operations:

• Avalanche zones (26 potential areas). The Olmsted Point avalanche
  zone requires a lot of work, including application of charcoal over the
  snow to help with melting and blasting the snow slab to make it safer
  for personnel.
• Heavy snow pack slows the whole operation.
• Trees that have fallen across the road and been buried in the snow.
  These can cause substantial damage to the equipment and result in a stop
  to all operations until they're cleared.
• Rock slides buried by the snow. These can cause substantial damage to the equipment and result in a stop to all operations.
• Snow storms during the opening require a stop to Tioga Road operations and in order to plow and sand the park roads.
• Road repairs and ditching and brushing operations once snow has melted back enough.

  
Other iconic national park roads that won't be open end-to-end in time for Memorial Day Weekend include the Trail Ridge Road in Rocky Mountain National Park and the Going-to-the-Sun Road in Glacier National Park.