It appears to be La Nina's turn to stir things up this winter, as her meteorological brother El Nino has finished up a three-year run.

Climate scientists agree that the phenomenon known as La Nina - "the little girl" - has settled back in after being last seen in 2007-08. As with its more-publicized partner El Nino - "the Christ child", La Nina affects everything from snowfall across the United States to hurricanes in the Atlantic Ocean to monsoons in India. The water temperatures in the equatorial Pacific have dropped steadily since last April, according to the Climate Prediction Center of the National Weather Service, meaning La Nina is indeed on her way.

So if past is prologue, skiers and snowboarders in the Northwest and Northern Rockies should get ready for some epic powder days. During the last episode, Mt. Baker received a record 1,100 inches of snowfall, while Mt. Hood got more than 800 inches.

"Stay north," scientist Jeff Weber of the National Center for Atmospheric Research in Boulder, Colo., told OnTheSnow. " La Nina is like a fire hose of moisture right on Banff and Washington state."

The intermountain region, including the Sierra Nevadas and Southern Rockies, will be "snow challenged," said Weber, himself a lifelong skier. Summit County will likely be drier than normal, but Steamboat Springs has been the exception in the Central Rockies because of the northwest-facing aspect of its mountains and basin, he said. Indeed, during the last La Nina in 2007-2008, residents on the northern Colorado town reported sheer exhaustion after shoveling snow off roofs daily during January and February.   

Skiers and riders in the upper Midwest won't likely see much difference, either in temperature or snowfall, and the Northeast will be colder but not necessarily any deeper in snow, Weber said.

La Nina periodically powers up as a result of colder-than-normal sea surface temperatures around the equator in the Pacific Ocean. The climatic anomaly pushes the moisture-laden Pacific jet stream farther north than normal and creates a persistent high-pressure system off the West Coast of the United States for most of the winter. This circumstance typically reduces precipitation and raises temperatures below the jet stream, which includes much of the Central and Southern tier of the United States.

Both La Nina and El Nino tend to dissipate as the season progresses, so Southern-tier residents may still get their powder jones fed in March and April, he said.

A recent study by the National Weather Service in Utah found precipitation levels reacted much more strongly to La Nina than to El Nino, with drier weather during the winter. Weber agrees, saying that high-desert states such as Utah and New Mexico experience the greatest range of change in snow conditions with these two anomalies.

In Europe, a similar oscillation in the Atlantic Ocean has been blocking and slowing storms for a number of years, Weber said, producing more snow in the Alps. This season should be much of the same, although it may ease a bit to produce a more normal snow year there.

Weber said he feels confident with his predictions because the La Nina-El Nino effect, also known as the El Nino Southern Oscillation, is an oceanic "signal" that is much more grounded and predictable than atmospheric counterparts.

"I'm not saying there will be a dirth of snow outside the Northwest and Canada, but those who need powder should head north," he said.

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