Average snowpack a good sign
And weekend big storms and all of February and March still to come!
Sometimes being average is really good news.
California’s statewide Sierra Nevada snowpack was exactly 100 percent of its historical average Thursday — precisely normal for this date, with roughly two months left in the winter snow season.
While that might sound me-
diocre, it’s a big jump from a month ago. On Jan. 1, the snowpack was just 69 percent of its historical average. And a year ago on Jan. 31, it was only 18 percent of normal.
How much snow falls every winter is critical to California’s water picture. The snow, which forms a vast “frozen reservoir” over the state’s 400-mile- long Sierra mountain range, provides nearly one-third of the water supply for cities and farms as it slowly melts in the spring and summer, sending billions of gallons of fresh water flowing down dozens of rivers and streams into reservoirs.
It also is key to the state’s ski industry, which suffered significantly during the 2012-16 drought. That event also increased wildfire risks, caused agricultural losses and triggered residential water cutbacks from San Diego to the Bay Area.
“Being at the historical average is good,” said Chris Orrock, a spokesman for the state Department of Water Resources, on Thursday. “We just had a 10- day dry spell, and we’re basically right where we should be, with more snow coming in this weekend.”
Widespread rain and mountain snow are forecast to begin today, with the heaviest precipitation tonight and Saturday.
The National Weather Service on Thursday issued a winter storm watch for the Sierra Nevada this weekend. Forecasters are projecting that 1 to 3 feet of new snow will fall across the Sierra. Some areas — Carson Pass, Ebbetts Pass and Sonora Pass — might get as much as 5 feet by Monday, the weather service said, with poor visibility expected on Interstate 80 and Highway 50 and chain controls likely.
Up to 4 feet of new snow is expected at Donner Summit near Lake Tahoe and along the Tioga Road in Yosemite National Park by Monday.
Every winter, at the beginning of each month, state water officials and other government scientists fan out to take snow measurements at more than 260 sites, with electronic sensors and manual readings. The oldest snow survey location dates back to 1906. One, at Phillips Station in El Dorado County off Highway 50, south of Lake Tahoe, is regularly done with TV cameras and journalists in tow.
On Thursday, the monthly reading at that location, which is near Sierra- at-Tahoe ski resort, showed 98 percent of the historical average. There were 50 inches of snow on the ground — double what there was there a month ago.
“It’s comforting to finally have an average year,” said John Paasch, chief of hydrology and flood control for the Department of Water Resources.
Already, by Thursday, water content of the Sierra Nevada snow across the state was 61 percent of the April 1 historical aver- age. In other words, California so far this winter has received almost two-thirds of a full winter’s Sierra snowfall, with this weekend’s big storms and all of February and March still to come.
The storms of January also have increased rainfall totals around the state. As of Wednesday evening, Sacramento was at 93 percent of its historical average rainfall for this date, while San Francisco was at 80 percent, Oakland and San Jose were at 76 percent, Los Angeles 139 percent and San Diego 131 percent.
The wet January conditions have caused reservoirs all over the state to rise significantly. Thursday, most of the state’s largest reser- voirs were at or above their historical averages for this date. The largest, Shasta, near Redding, was 65 percent full, or 95 percent of normal for this date, while Folsom, near Sacramento, was 53 percent full or 102 percent of normal; and San Luis Reservoir, between Gilroy and Los Banos, was 86 percent full or 109 percent of normal.
The weekend storms will bring more than new snowdrifts to the Sierra. They’ll also soak the Bay Area with rain.
Meteorologists with the weather service expect the storm to deliver 1 to 2 inches of rain across the Bay Area from tonight into the weekend. They issued a flash flood watch for tonight from Sonoma County to Big Sur.
“We expect local flooding along the roads and in small creeks,” said Steve Anderson, a meteorologist with the weather service in Monterey. “Downed trees and power outages. Pretty much a carbon copy of the previous big storm.”