California started 2017 off with an extremely active weather pattern. Since January 3rd, an “atmospheric river” has brought heavy rain and snow to much of the state. Ski areas within the Sierra Nevada mountain range are reporting close to record snow totals (Mammoth Mountain 101″ of snowfall, Heavenly 114″ and Squaw Valley 94″).
The lower elevations are receiving significant rainfall as well, causing some rivers to overflow. Area lakes are nearing capacity, prompting officials to expel extra water in preparation for runoff from higher elevations. Though Southern California has not received as much rainfall as the Northern portions of the state, they continue to see rainfall totals in the .5″ to 1.0″ range per storm. Winter storms have now accounted for 5 deaths in Northern California. The forecast calls for January 10th and 11th to be the heaviest snow and rainfall period of the recent storms.
Since January 1st, officials in Lake Tahoe are reporting a rise in water level of roughly 1 foot, which is equal to about 33.6 billion gallons of water. Down in the Sacramento Valley, the state Water Resources Division had to open the gates of a 100-year-old levee in order to alleviate rising water levels. This was no small task, as each of the dam’s 48 doors had to be opened up manually.
Officials are expecting numerous avalanches in prone areas due to new snowfall on an already heavy snowpack. Avalanche warnings currently extend from as far north as Mt. Shasta to as far south as Mt. Whitney. Mammoth Mountain Ski area had to stop operations over the weekend due to blizzard conditions and thunderstorms over the ski resort which could have put patrons at risk.
What is and Atmospheric River?
Sounding like something out of a science fiction novel about time travel, an atmospheric river is a narrow corridor or filament of concentrated moisture in the atmosphere. When these “rivers in the sky” make landfall, they often release this water vapor in the form of heavy rain or snow. The most common of such meteorological phenomena is a Pineapple Express, the name given to the warm water vapor plumes that originate over Hawaii and follow the jet stream northeast toward California. Many of California’s major flooding events have historically been a product of an atmospheric river.