Atmospheric River Batters Sierra With Hurricane-Force 130 MPH Winds

TRUCKEE (CBS SF) -- Winds topped 130 mph Wednesday as a potent atmospheric river brought rain, sleet and snow to the Sierra -- the latest weather woes for a region where several feet of snow has fallen over the last two weeks.

According to the National Weather Service, by the time the river heads east on Friday it will dump as much as four feet of new snow at Donner Pass on I-80 and three feet of new snow on Echo Pass on Highway 50.

Caltrans said chain control were in place in I-80 from Nyack to Truckee in both directions and on Highway 50 from Twin Bridges to Meyers.

The weather service said as of 9 a.m. Wednesday winds as high as 136 mph had been clocked at White Mountain Peak, 127 mph at Squaw, 122 mph at Alpine Meadows and 120 at Mammoth Mountain.

The river, which is slamming into Northern California from the warm tropics near Hawaii, has elevated the snow levels to above 8,000 feet with rain or sleet falling at the lower elevations.

"Around Lake Tahoe, we have seen a mix of rain and snow this morning, but snow continues above 7000 feet," the weather service. "Just over the past hour, the snow level at Oroville jumped from near 4000 feet to over 8000 feet... By this afternoon, we should see snow levels rise to around 7500-8500 feet."

Forecasters also warned of "roof-alanches" because of the rain-snow mix.

"Another concern will be roof-alanches -- snow falling off of roofs," the weather service said "Rain on snow will make snow on roofs more susceptible to rapidly sliding of roofs. The heavy dense snow is capable of killing and people have died for such events."

After the first pulse of the storm passes, it will be followed by a much colder front that will drop snow to lower elevations.

"After the rain changes back to snow in Tahoe/Truckee/Mammoth Lakes elevations, we could see snowfall accumulations of 1 to 2 feet, or more, with the highest accumulations expected around the Tahoe region," the weather service said.