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Tahoe Nugget #217:

La Niña Takes Aim at Tahoe
October 10, 2011

The first winter-like storm for the 2012 season barreled into the Tahoe region in early October and dumped nearly two feet of snow at several major resorts. The early shot of white stuff inspired the spokeswoman at Squaw Valley USA to predict another historic snowfall season for 2012, while Boreal Mountain Resort promised to fire up their snow guns in anticipation of an early opening before Halloween.

October is often considered a relatively benign weather month in our region, the last days of autumn before the onset of winter. Statistically the tenth month delivers about three inches of precipitation to the Central Sierra Snow Laboratory near Donner Pass, which includes about 10 inches of snow. These average precipitation statistics represent only a small fraction of the annual rain and snow the lab receives in a normal water year, but history shows us that October is actually a potentially volatile month for rain and snow.

The most infamous October storm may be the heavy snowfall late in the month that trapped the Donner Party in 1846, which doomed nearly half of them to starvation. Other notable October snowfalls include 1899 when 56 inches buried Tahoe City; 7.4 feet were measured on the Summit.

More recently, 50 inches of snow fell at the Snow Lab in October 2004, the greatest amount for that month since the lab was established in 1946 and a solid 500 percent more snowfall than average.

Last week's storm event may seem unusual, but consider that in both 2009 and 2010 the Tahoe-Truckee region was hammered early in the season. In mid-month October 2009 an unseasonably powerful jet stream drove a surge of subtropical moisture from a former super typhoon into the mountains, which started off a wet winter pattern that led to an above average water year.

Nearly the same thing happened in October 2010 when a dying Asian typhoon became entrained in the jet stream and smacked the Tahoe region with heavy rain. Squaw Valley was drenched with nearly 7.5 inches of water in a pattern that quickly segued into a cold, stormy November. Ultimately winter 2010 would set new snowfall records at several major ski resorts. 

These significant October events pale in comparison to the Columbus Day Storm in 1962, when a potent tropical storm containing abundant moisture from Typhoon Freda crashed into the West Coast with gale force winds and heavy rain. In the Sierra the deluge set precipitation records at Blue Canyon where nearly 10 inches of rain fell in 24 hours. Nearby Lake Spaulding set a separate record with 23 inches of rain in three days. In San Francisco the storm delayed and then nearly washed out the World Series competition between the Giants and the New York Yankees. (See Tahoe Nugget #151)

The 2011 water year recently ended on Sept. 30 with impressive rain and snowfall totals. Last year's 643 inches of snow at the Snow Lab ranks fourth greatest since 1946, just behind the legendary winter of 1983. A precipitation total of 84.5 inches made 2011 the eighth wettest since 1946, right behind  the El Niño-influenced winter of 1998.

Last year's moderate to strong La Niña event consistently delivered enough snowfall to produce some of the best skiing and snowboarding conditions in years. Warming sea surface temperatures in the Pacific Ocean temporarily dissipated the La Niña conditions this summer, but the water has cooled again and the Climate Prediction Center has issued a new La Niña advisory for this winter.

For the Truckee-Tahoe region of the central Sierra Nevada, La Niña-influenced winters are difficult to forecast. The Climate Prediction Center's official long range winter outlook for our area indicates equal chances for average precipitation and temperatures. Similar to the past two winters, we're off to a good start.