Weather Window: Tahoe Truckee winter wrap
Special to the Sun
TAHOE/TRUCKEE and#8212; The 2011 water year for the Sierra Nevada won’t officially end until Sept. 30, but for all intents and purposes our exceptional winter is over. April added an above average monthly quota for snow and precipitation in the Central Sierra, which helped advance 2011 in regional snowfall rankings at the Central Sierra Snow Laboratory (CSSL). For those keeping track, 2011 is currently the sixth snowiest since the end of World War II, and ranks 12th since snowfall measurements began near Donner Summit in 1878. For some of us locals who have lived here for more than 30 years, we’ve seen our share of epic winters. Counting all winters since 1946, fully half of the top 10 snowiest at the CSSL have occurred since 1980.
Relative to snowfall statistics, precipitation (rain and melted snow combined) lagged a bit in the all time rankings list, but the 75 inches of water measured so far at the Lab places 2011 in a virtual tie with 1984 for 19th wettest since 1899. Due to climate change, there has been a discernible trend for increasing amounts of winter precipitation near Donner Pass since World War II. Again, for anyone who has lived in the area since 1980, you have experienced seven out of the top 10 wettest years since 1946. Although any future precipitation this year is statistically unlikely to be a major game changer, since there are still nearly five months left in the water year the potential exists for 2011 to advance further in both snowfall and precipitation rankings.
The month of April was wet and cool which delayed snowmelt, so it was no surprise the May snow survey indicated a phenomenal double normal snowpack in the Lake Tahoe-Truckee region. At this point Lake Tahoe as a reservoir is storing about 50 percent of its capacity, which is 92 percent of average for this time of year. In direct benefit from this winter’s prodigious storm production, Tahoe’s surface level has increased dramatically since last year and is projected to rise another 2 feet or more, an estimate that puts the lake’s high point less than 12 inches from its federally-mandated maximum of 6,229.1 feet.
Water levels in reservoirs on the Truckee River system are excellent at 126 percent of average, and stream flow for the Truckee River during the May-July forecast period is expected to be nearly double normal. Cold, swift water this year requires more caution than usual for people and pets interacting with our regional streams and rivers. Despite the heightened flood potential through June, risks are lower on the Truckee River main stem due to available flood control storage in the reservoirs.
The La Nina-influenced storm patterns this winter blasted the Sierra with epic amounts of snow as a hyperactive jet stream drove cyclonic dynamos into the West Coast. The Storm King blessed the mountains with enough moisture this year that Lake Tahoe will rise nearly 5 feet. That huge amount of water is an incredible gift that historically has often come with adverse regional economic impacts due to floods or storm damage. Most of us are glad this winter is just about done, but we’ll be reaping the hydrological benefits for many months to come.
and#8212; Tahoe weather 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 email@example.com