Editor's note: This updates with plans to close all roads leading into Yosemite Valley at 5 p.m. local time Friday and to halt most visitor services during the duration of the storm. The roads are not expected to reopen before Monday.

Heavy storms this weekend could generate flooding that approaches the January 1997 flood that turned Cook's Meadow in the Yosemite Valley into a shallow lake/NPS Video

A major storm taking aim at Yosemite National Park is forecast to dump enough rain and snow to raise the Merced River through the park's iconic valley nearly 6 feet above flood stage by Sunday afternoon. Park officials announced that all roads leading into the Yosemite Valley would close at 5 p.m. Friday and remain closed through Sunday at least.

If the weather forecast proves true, it would be the highest river flow through the valley since 1997, when storms pushed the Merced more than 13 feet above flood stage and generated flooding that washed away campgrounds and caused significant infrastructure damage. That flooding pushed the water volume of the Merced River to 24,600 cubic feet per second, the highest flow in 80 years of recording, the National Park Service noted.

"The flood severely damaged a whole range of facilities from miles of roads, bridges and trails, to utility systems, to several hundred units of guest lodging, campsites, and employee housing," Yosemite officials said in a 2013 report that detailed the recovery effort following that event.

Park officials this week have urged visitors to realize significant flooding could lead to park closure this weekend. The weather forecast issued Thursday afternoon for the park predicted heavy snows above 7,500 this weekend and  rains at the lower elevations, following by a warming trend that could bring the temperature at 8,000 to 46 degrees. A flash flood watch for the area was to be in effect from Friday night into Monday afternoon.

"Another atmospheric river is expected to move in on Saturday with a prolonged period of heavy rainfall possible through Monday," the National Weather Service reported. "This will likely result in rapid rises along small streams and rivers and the threat of flash flooding." 

At midday Friday the park issued a release in which it said, "(V)isitors intending to visit Yosemite National Park are highly encouraged to monitor weather reports and check road conditions before departing."

The following areas were expected to remain open and operational:

* Hetch Hetchy via Evergreen Road will remain open daily from 9 a.m. - 5 p.m.

* Along Big Oak Flat Road (Hwy 120 West): Hodgdon Meadow Campground will remain open on a first come, first served basis, Tuolumne Grove and Merced Grove will remain open, and Crane Flat Gas Station is open (credit cards only).  The Big Oak Flat Road will be closed at the junction to Foresta.

* Along the Wawona Road (Hwy 41): Wawona Campground will remain open on a first come, first served basis. Visitors will have access to the Redwoods Guest Cottages. There will be access to Yosemite West.  The Wawona Road will be closed at Chinquapin (no access will be available to the Glacier Point Road).

* The El Portal Road (Hwy 140) will be closed at the park line in El Portal. Businesses along Hwy 140 outside of the park are anticipated to remain open.   

With the storm expected to reach its peak at midday Sunday, roads leading into the valley were expected to remain closed until Monday at the earliest. At that time park crews would inspect the valley for damage.

Here's a look back at the January 1997 flooding, courtesy of the National Park Service: