CA Snowpack's 'Big Melt' Brings Floodwaters, Park Closure

CALIFORNIA — Fast-warming temperatures across the Golden State are kicking off the "Big Melt" in the Sierra Nevada, where the snowpack is two to three times higher than average with May on the doorstep.

With abundant sunshine and temps forecast to keep climbing heading into the weekend, the National Park Service on Tuesday announced it would close most of the Yosemite Valley on Friday evening, citing likely flooding.

Parts of the Bay Area are forecast to hit 90 degrees, with much of Southern California poised to follow suit and the deserts looking at triple digits.

In Yosemite Valley, dorecasters expect the Merced River will run 2 to 3 feet above flood stage by Monday. While the initial closure will be in place until next Wednesday, it could be extended further if floodwaters continue to roar.

"While visiting Yosemite Valley with high water is an amazing experience, Yosemite Valley closes once the Merced River at Pohono Bridge is forecast to exceed 10 feet," the National Park Service explains. "At flood stage, roads and other critical infrastructure begin flooding, making it unsafe for visitors to be in Yosemite Valley. It is very likely the Merced River will reach flood stage off and on from late April through early July."

Park officials said reservations for lodging and campgrounds in the eastern Yosemite Valley would be canceled and refunded, with wilderness permits rescheduled to alternate trailheads as possible. A few areas of the park will remain open during the larger closure, including Wawona, Tunnel View, Crane Flat, Hetch Hetchy, and the furthest west areas of the valley.

Yosemite is far from alone in its flood concerns.

As The Mercury News reports, roughly 60,000 acres of farmland in Tulare and Kings counties are already under several feet of water from last month's atmospheric rivers. The warm weather ahead will add to growing concerns in the San Joaquin Valley as some Southern Sierra rivers double their flow rate, and the risks only build heading into next month.

"Eventually there is a risk that reservoir releases will exceed channel capacity," Michael Anderson, a state climatologist, told the newspaper. "The problem is there's nowhere else for this water to go in the Tulare Lake Basin. It's just going to fill up like a bathtub."

The level of flooding that California can expect in the coming months is highly dependent on the weather. If the melt is slow and steady, officials expect the impacts will be less dramatic, but heat waves or warm "Pineapple Express" systems can make quick work of the snowpack and spell trouble.

Officials from California State Parks, the Department of Water Sources and CalFire also urge residents to take extra precautions around rivers and streams this spring, as they run much faster and colder than usual.

"This year is very different from the last several years, in that excessive snowpack and rain will continue to create challenges for us in the weeks and months ahead," said Joe Tyler, the CalFire chief. "Rising water levels in rivers and streams will be very cold, very fast and can easily overwhelm those that aren't prepared or don't heed warnings. Our teams will continue to focus on localized flooding risks, potential for major flooding, water rescues and our operational capabilities to support our communities moving into the spring and summer months."

With just a few days of April left, California's statewide snowpack was sitting at 256 percent of normal on Tuesday, reaching as high as 324 percent in the Southern Sierra.