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Winter snowpack growth stalls following dry spell

February 11, 2013

Although the Mammoth area is at about 75 percent of its normal snowpack for the year, much of the rest of the Sierra is barely above 50 percent of normal, due to a dry January and, so far, dry February. These two months are normally the Sierra’s wettest months. Photo by Sterling Schat

This winter started off with a big, snowy bang and raised hopes that it would compensate for last year’s drought conditions, but a dry January and a so-far dry February are tempering expectations for this winter’s snowpack.
The first snowpack survey of the Sierra was completed at the beginning of the month and it puts the Sierra at about 55 percent of normal for the whole winter, according to state data.
In other words, if it did not snow another flake between now and the end of the winter snowpack measuring season (April 1) the Sierra, overall, would only have about half (55 percent) of the normal amount of snow.
February is considered to be one of the Sierra’s wettest months (January is the wettest), but February is looking dry and January provided only about 13 percent of the amount of snow it normally does.
Predictions for the rest of the month, just released by the national Climate Prediction Center, estimate the region will be drier than normal.
“We could still have a miracle March, and I hope we do, but if not, we are probably looking at a winter at about 60 to 75 percent of normal for the Eastern Sierra,” said Paul Scantlin, aqueduct manager for the Los Angeles Department of Water and Power.
“That’s not great, but it’s a lot better than last year’s winter, which ended at about 44 percent of normal.”
The Mammoth region is one of the Sierra’s successes, insofar as the snowpack is concerned. Mammoth Pass is at between about 113 percent and 122 percent of normal for this date, or at about 75 percent of normal for the whole year.
If the Mammoth area doesn’t receive any more snow, it would still have about three-quarters of the amount of snow it normally gets in a year.
Several other regions near Mammoth, such as Rush Creek near Mono Lake, are also doing well, at about 110 percent of average for the date and about 69 percent for April 1, according to data taken at Gem Pass by Southern California Edison.
But the Southern Sierra, near Cottonwood Lakes, Rock Creek Lake and Bishop Creek are lower, coming in between 57 percent (Cottonwood) and 74 (Rock Creek) percent of normal for the date and 37 percent and 55 percent of normal for April 1.
The only reason water managers across the state are not deeply worried yet is because November and December were so wet, they provided a buffer against the recent spate of dry weather.
But if it does not snow again soon, it will be increasingly hard to catch up. Moisture that comes after April 1 usually melts as fast as it falls, providing little benefit to the snowpack and water managers.
“While not yet a warning of drought conditions or water shortages to come, that could change if the balance of the winter is also dry,” said state Department of Water Resources Director Mark Cowin in a news release after the state’s snowpack survey results were in at the end of January.
“Relatively dry weather this month is once again a reminder that the weather is unpredictable and we must always practice conservation.”
But DWP’s public affairs specialist Chris Plakos was optimistic, noting how quickly numbers can change in the Sierra – in either direction.
“All it would take for Mammoth to reach normal is another two or three good storms,” he said. “Mammoth Pass already has about 32 inches of moisture and the 50-year average is about 42 inches. That’s just a few more several-foot storms.”

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