In the simplest terms, a La Niņa season -- which we're currently experiencing -- means changing ocean temperatures near the equator, which should bring more precipitation to the northwestern U.S. and a drier winter to the southwestern states. La Niņa doesn't affect the East Coast of the U.S. as significantly as the West.
And although this winter has brought some of what was expected, it's also brought a fair share of surprises. "La Niņa and El Niņo shift the odds but they don't guarantee an outcome," says Robert Henson, Colorado-based meteorologist and editor with the University of Atmospheric Research. "There are unusual aspects of this season, like the fact that southern California, which shouldn't get a lot of snow in a La Niņa year, has had good snow conditions. There's no real explanation for that, it's just where the jet stream set up."
Central California's Mammoth Mountain, which averages 342 inches annually, already has a whopping 454 inches this season. And southern California's Bear Mountain and Snow Summit recently got a four-foot dump and they're reporting a 36- to 60-inch base.
But other areas of the southwest haven't been so lucky. New Mexico's Taos Ski Valley is reporting a total snowfall of 131 inches, about half what they normally have this time of year. "It has totally been a La Niņa season down here," says Taos Ski Valley's Adriana Blake. "Luckily we had super cold temps that allowed snowmaking to get us open and the snow we have gotten has been both timely and wet which means the skiing is surprisingly good. We're glad we only have 25 days of this season left."
As predicted during a La Niņa, in Colorado, the ski areas in the northern part of the state -- Steamboat and Summit County -- have experienced plentiful snowfall. But in the southern half of the state -- resorts in the San Juan range like Silverton and Wolf Creek -- have had less-than-average storms.
In Washington, where a La Niņa winter once dropped a world-record setting snowfall of 1,140 inches on Mt. Baker, the season has been both good and bad. "Historically La Niņa winters have been very good to us in Washington," says Stevens Pass' marketing manager Chris Rudolph. "It hasn't been super good this year but March is coming in strong. What this La Niņa cycle has taught us is that the only thing that holds true is patience. A season is a whole season long. It's not about a single day."
As for next year, UCAR's Henson says it's hard to tell definitively what next winter will bring, but he says it's looking like it's going to be neutral -- neither La Niņa nor El Niņo. "Half the time it's neutral. Sometimes, La Niņas do go through a second year, but it's looking less likely that this one will," Henson says. "Computer models are showing that next year will most likely be neutral. We'll know for sure in October or November."