Weather Window: Winter wrap up
July 5, 2010
TAHOE/TRUCKEE and#8212; The cool, damp spring weather has segued into summer and the prolonged winter of 2010 has finally bit the dust. Well, almost. Officially, the 2010 water year ended on June 30 for Californiaand#8217;s coastal regions and interior valleys. The lowlands calculate annual precipitation based on a July 1 to June 30 cycle. In the Sierra, however, our water year runs from Oct. 1 to Sept. 30. Early October is traditionally the time of year when reservoir storage and stream flow are at their lowest of the year. So technically, any precipitation that falls into a mountain rain gage during the next three months will be added to the 2010 winter season.
Last winterand#8217;s El Nino event in the Pacific Ocean was no barn burner when it came to Californiaand#8217;s winter precipitation, but the influence of warmer ocean water in the tropics did work some magic and produced above average rain and snowfall for much of the Sierra range. The water was desperately needed after three consecutive years with below normal precipitation. El Nino-influenced winters generally bring enhanced moisture to the central and southern parts of the Golden State and last year was no exception. The town of Redding in the north picked up 91 percent of their average rainfall, but central and southern California trended from slightly above normal to well above average at locations like Santa Barbara (123 percent) and Palm Springs (127 percent).
Seasonal precipitation was above average, but donand#8217;t forget the Columbus Day Storm in October 2009 drenched much of central and southern California with heavy rain and started the season off with a bang. The San Francisco Bay Area received more than 200 percent of their normal monthly rainfall, while Sacramento surged to 364 percent of average and Los Angeles was doused with a phenomenal 559 percent of normal for October. Here in the mountains, the storm dumped more than 3.5 inches of rain on Oct. 13 at the Central Sierra Snow Laboratory on Donner Pass. That 24-hour storm represented more rain than is usually received in all of October, but the moisture was rapidly absorbed by the desiccated soil conditions.
The 8-Station Index for the Northern Sierra, which includes precipitation gages from Mount Shasta City south through Blue Canyon (Interstate 80) and Pacific House (Highway 50), is currently at 109 percent of normal for the date. That nine percent represents only about three inches of water for the season, but you wouldnand#8217;t know it looking at current stream and river flows throughout the Sierra. High water on the Truckee River has precluded any significant release from Lake Tahoe into the system and squelched what is usually the busiest weekend for Tahoe City river rafting companies. The exceptional late season runoff is less predicated on the above average precipitation this winter than the very cool spring temperatures. The months of April, May and June were all below normal in temperature and that delayed the snow melt significantly.
The cool spring put a damper on some outdoor activities, but diehard skiers and snowboarders milked the slopes for every last run of the season. Enough snow remains in the mountains that Kirkwood Mountain Resort (which received nearly 45 feet of snow last winter) opened up for the Independence Day Weekend with chair lift rides up the mountain to access skiing, snowboarding and mountain biking (or all three). Not to be outdone, Boreal Mountain Resort is planning on opening up a full terrain park on July 10 and 11, in what theyand#8217;re calling a July Shred Fest.
So while youand#8217;re waiting for the upper elevation snowpack to melt and a chance to see the alpine wildflowers bloom, grab your skis or board and get in one last shot at your favorite winter sport.
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and#8212; Tahoe historian Mark McLaughlin is a nationally published author and professional speaker. His award-winning books are available at local stores or at http://www.thestormking.com. You can reach him at firstname.lastname@example.org
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