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Snowfall could be measured in feet across Sierra during ‘miracle March’ storms

After a paltry February, snow is coming back to the Sierra mountains. Forecast models suggest snowfall totals could exceed five feet over the next two weeks. ( <a href="http://squawalpine.com/">Squaw Valley/Alpine Meadows</a> )
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A series of Pacific storms are lined up in the forecast for California over the next week with the potential to dump a truckload of snow on the Sierra mountains. Over the next two weeks, forecast models are suggesting the potential for more than five feet of snow across the Sierra crest — much-needed precipitation at the end of a winter that has not lived up to El Niño hype.

The weather pattern has shifted significantly since February, when record high temperatures were set across Southern California and rainfall totals were well below average. While high pressure dominated the West Coast weather last month, low-pressure systems with strong connections to tropical Pacific moisture appear to be the norm for March. Models are now forecasting this to remain in place through at least mid-month.

After February’s abysmal precipitation, Californians are calling this month “miracle March,” with fingers crossed that forecasts prove right.

Pacific moisture will stream into the West this weekend and continue through next week. An atmospheric river of moisture — meteorologists call it the “pineapple express” — will extend from the central Pacific Ocean, near Hawaii, all the way to the West Coast. For the lower elevations, the storms that tap into this river could dump up to 11 inches of rain on Northern California over the next week. For the higher elevations, snowfall totals will be measured in feet.

Exactly how much snow the Sierra collects will be determined by how warm the storms are as they come ashore. Though pineapple express systems usually contain boatloads of moisture, they also tend to be on the warm side, which means precipitation will begin as rain everywhere but the very highest elevations before colder air moves in.

For this weekend’s storm, the snow level around Lake Tahoe is expected to remain around 8,000 feet through much of Saturday, which means everything below 8,000 feet will fall as rain. This includes Donner Pass, where Interstate 80 crosses the Sierra at a peak elevation of around 7,000 feet. Once the cold front sweeps though, snow levels could drop to around 6,000 feet — or lake-level — on Sunday or Monday.

As much as two to three feet of snow could fall along the Sierra crest through Monday morning alone. But over the next two weeks, models are forecasting the the possibility of up to six feet in the highest elevations. In its long-range outlook, the National Weather Service is forecasting “heavy snow” in the northern and central Sierra Mountains every day from Saturday through the following Monday, March 14. That’s 10 days in a row with heavy snow in the forecast.

Sierra snowfall is just as important for drought conditions as the rain that runs off into reservoirs. Snow pack serves as secondary reservoirs for the state, holding water in the form of snow until the spring months when it can replenish lakes. The water that flows through reservoir dams also enables utilities to generate hydroelectric power, instead of relying on greenhouse gas-emitting coal or gas.

California is in basically the exact same drought situation that it was in one year ago, despite a winter’s worth of strong El Niño conditions and wild forecasts. As of Thursday, a little more than 38 percent of the state was in “exceptional drought” — the most severe category on the U.S. Drought Monitor scale. That’s only down from around 40 percent at this time last year.

Though very strong El Niño years have a history of big Sierra snow pack, this season has been running close to average — far from the snowiest season on record back in 1982-1983, but much better than last year’s paltry winter. On Feb. 1, snow water equivalent, or how much water is contained in the snow pack, was estimated at over 100 percent of normal for the date in the north, central and southern Sierra.

That changed after a month of warm and dry conditions. As of March 3, central Sierra snow water equivalent was down to 82 percent of normal for the date — about six inches less than what is measured at this point in an average year. The region would need around eight additional inches of snow water equivalent to stay in place through April 1 to call this an average year. Although it’s the best precipitation the state has seen in half a decade, what California really needs is an above-average year.

A late winter snowfall is predicted throughout the D.C. area Thursday night into Friday morning. (Video: Erin Patrick O'Connor, Jason Samenow/The Washington Post)
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