El Niño will utterly ruin the coming ski season, leaving Sun Valley hanging high and dry with warm temperatures and a meager snowpack.
Or not.
"You might as well toss a coin in the middle of the floor," Gary Wicklund, a meteorologist for the National Weather Service in Pocatello, said about the impact of the weather phenomenon. "You really don't know what you're gonna get."
Contrary to popular belief, El Niño, which is forecast to be moderately strong this year, doesn't always produce warm, dry winters in southern Idaho.
In fact, Sun Valley's snowiest winter on record—1982-1983—was during a particularly strong El Niño episode. El Niño events in 1994-1995 and 1997-1998 also produced above-average winters in terms of snowfall.
Meanwhile, the three driest winters in the last 35 years—1976-1977, 1986-1987 and 1987-1988—were all spawned during El Niño events.
Occurring on average every three to five years, El Niño refers to a warming of the sea-surface temperatures along the equator in the central and eastern Pacific Ocean.
Peruvian fishermen in the 19th century used the term to refer to the annual flow of warm equatorial waters southward during Christmas time. El Niño is a derivation of the Spanish phrase for "Christ Child," or baby Jesus. It was later adopted by the scientific community and used only for those years that displayed abnormally warm conditions in the equatorial Pacific.
The event can alter global weather patterns, causing droughts in some areas and abnormally high precipitation in others.
In the United States, El Niño events typically result in cooler and wetter-than-normal conditions in the southern states and warmer and drier weather in the north.
Contrarily, La Niña, which refers to a cooling of the equatorial Pacific, produces cool, very wet winters in the Northwest. The La Niña event of 1998-1999 season buried Mt. Baker Ski Area, in northern Washington, under a world record 1,140 inches of snow.
"If it's a strong El Niño there's no doubt the Northwest stays dry," Wicklund said. "High pressure controls the direction of storms and if it doesn't move everything has to go above it or below it."
During strong El Niño events, a stubborn high-pressure zone often develops over the Northwest, causing storms to bounce north into Canada, or south into California, Arizona, New Mexico and southern Colorado.
But while the Pacific Northwest stays dry, storms that hammer central and northern California can slip up to the north and slam southern Idaho. Those storms, which are fueled by a southwest flow, are usually warm but intense and can produce whopper snow events in Sun Valley.
"I would almost bet that a moderate type of El Niño would produce more precipitation in the central mountains," Wicklund said.
Of the 10 wettest years on record in Ketchum since 1971, three were El Niños, two were La Niñas, and five were neutral—also known as "El Neither."
Last year's mammoth winter in Ketchum, which was an El Neither, produced 146 inches in Ketchum—as measured by the Ketchum Ranger District in downtown Ketchum. That's the seventh snowiest winter since 1971. A staggering 54 inches of snow fell in January 2006, which was just shy of the record 56.5 inches that fell in January 1993. If temperatures had been cooler last winter, the snow totals would have been significantly higher.
The Climate Prediction Center, a branch of the National Weather Service that specializes in long-range forecasting, is calling for cool and wet conditions to persist over southern Idaho into early December. But that's expected to change by mid-December, with slightly below-normal precipitation forecast through February.
"Last year the (Climate Prediction) Center came out and said, 'We're really going to be dry,' and we had a bumper crop of snow," Wicklund said. "For us, we're lucky if we nail the forecasts a week at a time."
Sometimes, the most accurate long-range forecasts come from longtime locals. Willy Cook, a 30-year Ketchum resident, moved to town in the winter of 1976-1977, which was one of the driest ever. Only 36.5 inches of snow fell in Ketchum that winter.
"My first winter here there was no snow and no mullein," Cook said.
Mullein is a hardy weed with a firm stalk that, according to Cook, is a very accurate predictor of the coming winter.
"It's like a snow stake," he said. "However tall the mullein gets, that's how much snow we'll get."
The problem is the mullein this year ranged from just a couple feet high to above the chest.
Cook said he also looks at cycles, specifically the seven-year cycle—seven years of dry followed by seven years of wet—that's treated as gospel in ski-bum circles.
Last winter's bountiful snows came on the heels of a six-year drought. In the seven years preceding that drought, only one winter (1993-1994) produced below-average snowfall.
"After all that, a prayer or two to the snow gods on a full moon seems to help," Cook said.
Two skiers make their way through Warm Springs Village during one of the many snowstorms that hit the Ketchum-Sun Valley area last winter. Photo by Willy Cook
