SALT LAKE CITY — Those notorious lake-effect snowstorms that delight winter revelers in the Salt Lake Valley could appropriately be called mountain-effect storms.
A study published Tuesday in the American Meteorological Society Journal's Monthly Weather Review shows the interplay of winds and mountains — particularly the Wasatch Front and Oquirrh ranges — are critical actors that enhance these events.
“It is going to help us with weather prediction — helping forecasters recognize that in some lake-effect events, the mountains or hills can play an important role in triggering lake-effect snow bands” over large bodies of water, said the study's senior author, Jim Steenburgh.
Steenburgh is a professor of atmospheric sciences at the University of Utah who partnered with a doctoral student, Trevor Alcott, who now works at the National Weather Service in Salt Lake City.
The lake effect occurs when a cold mass of air moves over a large body of warmer water, picking up moisture and heat to make the air mass rise and cool, ultimately dumping snow downwind. Steenburgh said it already was known that lake-effect snowfall increases as the moist air rises over mountains. But the latest study shows something new and different: Mountains sometimes are essential to triggering the lake-effect over the lakes themselves.
"You take the mountains out and take the lake out, you get rid of any snow at all," he said.
Weather forecast models now fail to adequately include the Wasatch Range, which runs north-to-south directly east of the Great Salt Lake and the Ogden-Salt Lake City-Provo metropolitan area. Forecast models also don’t include northern mountains along the Nevada-Idaho-Utah border, located northwest and north of the Great Salt Lake, Salt Lake metropolitan area and Wasatch Range.
“That may be one of the reasons we struggle” in forecasting lake-effect storms in Utah’s major cities, he said.
This particular study looked at the moderate lake-effect snowstorm that hit metropolitan Salt Lake City and the Wasatch Range on Oct. 26-27, 2010.
While some cities in the Salt Lake Valley had no snow, the Alta Ski Area got pounded with 13 inches.
Research showed three distinct elements at work because of the interaction between the Great Salt Lake and the surrounding mountains:
• Winds become warmer as it moves over mountains and flows south and southeast toward the Great Salt Lake, moderating the strength of a lake-effect storm.
• Northern mountain ranges deflect cold air masses as they converge over the Great Salt Lake and the air picks up heat and moisture from the lake. But the convergence of air from the northeast and west makes it rise and cool, producing lake-effect snow bands over the lake.
• The Wasatch and Oquirrh ranges that form the boundaries of the Salt Lake Valley act as a funnel, forcing air flowing south off the Great Salt Lake to move directly into the valley, giving a boost to more snowfall.
Since 1998, the Great Salt Lake has helped generate from three to 20 lake-effect snowstorms each winter, most of them relatively small and affecting some areas but not others. The average is about a dozen lake-effect storms each winter, Steenburgh said.
“There is a rich spectrum of lake-effect snowstorms,” Steenburgh says. “Some cover a wide area with light snowfall. Some organize into more intense snow bands that produce heavier snow over a smaller area. Over the Great Salt Lake, 20 percent of our lake-effect events are these narrow intense bands.”
The research was funded by the National Science Foundation and the National Oceanic and Atmospheric Administration’s National Weather Service.
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