Warm spring temperatures are heating up Tahoe's mountainsides, bringing increased avalanche danger to backcountry skiers and hikers.
Within the last few days, the south face of Mount Tallac saw three massive wet slides. Snow to the left of the "Cross" let loose and plowed down the mountain for more than 1,000 feet.
Avalanche swaths and debris piles are visible on slopes throughout the basin as the large accumulation of snow from this winter turns to slush and gives in to gravity.
"We're into our spring scenario. During the day when we get rapid warming, we get point releases, which will result in wet slides," said Bob Moore, winter sports specialist with the Truckee Ranger Station of the U.S. Forest Service. Moore works with the Central Sierra Avalanche Advisory Web site at Avalanche.org.
In warm conditions, avalanche danger increases as the day wears on, starting with "low" rating in the early morning and growing to "moderate" in the late afternoon around 3 or 4 p.m.
"Ski stuff early on sunny, warm days," said Jay Sells, manager at Sports Ltd. at the "Y" and an avid backcountry skier. "You shouldn't be skiing stuff at noon. You should be back at the car at 10:30, 11:30 at the very latest."
Sells said a friend recently was beaten up pretty badly by an avalanche while skiing the Emerald Bay Shoots, which tower to the north of the bay.
Max Stevenson, a hydrologist from Davis who comes up every weekend to ski Tahoe's backcountry, planned an early start on Tallac on Sunday morning, but was soon deterred by skiers already hiking out.
"They had started at 6 a.m., got halfway up, and their poles were sinking in all the way to the hilt," said Stevenson.
He noted that the temperature was 41 degrees in Christmas Valley at 6 a.m., meaning snow on the slopes probably did not freeze. If temperatures don't reach freezing at night, that's a recipe for wet slides.
Stevenson had been skiing the previous weekend near Echo Peak when the first skier in his party to descend set off a 400-foot avalanche. The skier quickly skied aside to a rocky area.
"We know we had people all over the backcountry this last weekend," said Moore. "Nice weather, great snow. Velvet corn snow, this is what California spring skiing is all about."
Corn snow is created by the repeated melting and refreezing of the snowpack. Warm it up a little, and corn turns to slush, the stuff of wet slides.