La Nina keeps Sierra snowless
Bill Lindelof
Sacramento Bee
12/19/2011
After a big snowfall year in 2010, snowboarders and skiers are still waiting for big storms this year.
National Weather Service forecasters say don't give up on the snow season yet. Snow could come anytime, but probably not this week.
Forecaster Brooke Bingaman, with the National Weather Service's Sacramento office, explained that a La Nina weather pattern is influencing the north state's weather. A La Nina event pushes the polar jet stream far north of the west coast while the Pacific jet stream, although it can vary, usually is aimed for the Pacific Northwest.
"Think of the jet stream as the general pathway for our winter storms," said Bingaman in an e-mail. "The reason the Sierra has remained fairly dry for all of November and thus far in December is due to the fact that the storms and associated moisture that have developed in the past 1-plus months have been guided up and over the general high pressure ridge that has lingered over the eastern Pacific Ocean."
Bingaman noted that recent windy storms in Sacramento developed far North near Alaska, then traveled inland into Canada before dropping southwestward back towards the west coast.
When a storm drops south like that from Canada, it is traveling over land, Bingaman said. As a result it is dry -- and that means no Sierra snow with those systems, just colder temperatures and the winds.
"Typically, our winter storms drop south from the Gulf of Alaska, continue to pick up moisture from the ocean before finally moving inland into California bringing snow to the mountains," she said.
As many weather watchers know La Nina can be tricky. Northern California is along the southern border of the "wet" area. Over the entire winter, some of the storms will travel south enough to bring the Northern -- and even Central Sierra -- some decent snow events, Bingaman said.
