Lake-effect snow sometimes needs mountains

Feb 19, 2013
This map shows how mountains surrounding Utah's Great Salt Lake interact with the lake to cause some "lake-effect" snowstorms. Air masses from the north-northwest are channeled by mountains north of the lake so they converge above the lake. The air picks up heat and moisture from the lake, so it rises, cools and produces snow as it is funneled into the Salt Lake Valley by surrounding mountains. Credit: Jim Steenburgh, University of Utah

University of Utah researchers ran computer simulations to show that the snow-producing "lake effect" isn't always enough to cause heavy snowfall, but that mountains or other surrounding topography sometimes are necessary too.

The study is relevant not only to forecasting lake-effect storms near the Great , Sea of Japan, Black Sea and other mountainous regions, but also sheds light on how even gentle topography near the Great Lakes helps enhance lake-effect snowstorms, says the study's senior author, Jim Steenburgh, a professor of atmospheric sciences.

"It is going to help us with – helping recognize that in some lake-effect events, the or hills can play an important role in triggering lake-effect snow bands" over large bodies of water, Steenburgh says.

The new study was published today in the American Meteorological Society journal Monthly Weather Review. Steenburgh co-authored the study with first author and University of Utah Ph.D. student Trevor Alcott, now at the in Salt Lake City.

The research was funded by the National Science Foundation and the National Oceanic and Atmospheric Administration's National Weather Service.

Lake-effect snow's "negative impacts are in terms of snarling traffic and potentially closing schools," Steenburgh says, "And then there is the positive benefit for Utah skiers, which is a deep powder day that boosts our winter sports economy."

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. It already was known that lake-effect snowfall increases as the moist air rises over mountains. But the new study shows something new and different: mountains sometimes are essential to triggering the lake-effect over the lakes themselves.

"Most people recognize that mountains get more precipitation than lowlands because of moist air being lifted over the mountains," Steenburgh says. "Everybody recognizes that it plays a role in lake-effect storms. What we're showing here is a situation where the terrain is complicated – there are multiple mountain barriers, not just one, and they affect the air flow in a way that influences the development of the lake-effect storm over the lake and lowlands, rather than just over the mountains."

He says 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, Steenburgh says.

Indeed, the new study shows that without the northern mountains, more cold and moist air would flow south from Idaho's Snake River Plain, pass over Utah's Great Salt Lake and drop much more snow on the Salt Lake City area and Wasatch Range than real lake-effect storms.

How Mountains Can Contribute to the Lake Effect

The new study examined a moderate lake-effect snowstorm that hit metropolitan Salt Lake City and the Wasatch Range on Oct. 26-27, 2010. Some Salt Lake Valley cities had no snow, while others got up to 6 inches. The Alta Ski Area in the Wasatch Range got 13 inches of fresh snow, although it hadn't yet opened for the season.

The researchers found three key mountain-related or "orographic" factors were necessary to produce the October 2010 lake-effect storm, and that in this storm, the lake-effect occurred only because of the interaction between the Great Salt Lake and surrounding mountains:

  • Air moving over northern-northwestern Utah's mountains warms and dries as it flows downslope to the south and southeast toward the Great Salt Lake. Without this warming and drying, the lake-effect from the Great Salt Lake would be even stronger, the study found. This warm, dry downslope flow is similar to what are known as Chinook winds on the east slope of the Rocky Mountains or foehn winds flowing off the Alps.
  • The northern mountain ranges deflect the south- and southeast-flowing cold air masses so they converge over the Great Salt Lake. As the air picks up heat and moisture from the lake, it warms, making land breezes blow onto the lake from its western and eastern shores. The convergence of air from the north, east and west makes the air rise and cool, producing lake-effect snow bands over the lake.
  • The Wasatch and Oquirrh ranges, which respectively form the east and west boundaries of the Salt Lake Valley, act as a big funnel, forcing air flowing south off the Great Salt Lake to move directly into the valley, further enhancing air convergence and snowfall.

Simulating the Lake Effect

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 says. Lake-effect storms account for about 5 percent to 8 percent of the precipitation south and east of the Great Salt Lake from mid-September to mid-May.

"There is a rich spectrum of lake-effect ," 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 Oct. 26-27, 2010 weather event "wasn't a huge snowstorm," but fell between the two extremes, he adds.

An earlier study by Steenburgh showed that a Great Salt Lake-effect storm on Dec. 7, 1998 really was the result of the lake effect alone, like many storms from the Great Lakes. But the new study showed that during the lake-effect storm on Oct. 26-27, 2010, something quite different happened: Lake-effect snows fell only because of a synergistic interaction among the Great Salt Lake and mountains downstream.

Alcott and Steenburgh used weather data and existing weather research software to construct a "control" computer simulation that closely mimicked the real 2010 storm by incorporating the effects of the Great Salt Lake and surrounding mountains. Then they reran the simulation multiple times, but with various aspects missing.

"We can play God with this model," Steenburgh says. "We can see what happens if the upstream terrain wasn't there, if the lake wasn't there, if the Wasatch Range wasn't there."

The simulations showed that the lake effect would not have happened in the storm were it not for both the lake and downstream mountains:

Explore further: Deforestation could intensify climate change in Congo Basin by half

Related Stories

What happened to Lake Champlain's native trout?

Dec 06, 2012

Scientists identify it as Salvelinus namaycush. Other names include mackinaw, lake char, touladi, togue, siscowet, and paperbelly. Lots of people call it, simply, a lake trout. It's a freshwater fish found in many northern ...

Recommended for you

Predicting bioavailable cadmium levels in soils

17 hours ago

New Zealand's pastoral landscapes are some of the loveliest in the world, but they also contain a hidden threat. Many of the country's pasture soils have become enriched in cadmium. Grasses take up this toxic heavy metal, ...

Oil drilling possible 'trigger' for deadly Italy quakes

21 hours ago

Italy's Emilia-Romagna region on Tuesday suspended new drilling as it published a report that warned that hydrocarbon exploitation may have acted as a "trigger" in twin earthquakes that killed 26 people in ...

Snow is largely a no-show for Iditarod Trail Sled Dog Race

21 hours ago

On March 1, 65 mushers and their teams of dogs left Anchorage, Alaska, on a quest to win the Iditarod—a race covering 1,000 miles of mountain ranges, frozen rivers, dense forest, tundra and coastline. According ...

UN weather agency warns of 'El Nino' this year

21 hours ago

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

Study shows less snowpack will harm ecosystem

22 hours ago

(Phys.org) —A new study by CAS Professor of Biology Pamela Templer shows that milder winters can have a negative impact both on trees and on the water quality of nearby aquatic ecosystems, far into the warm growing season.

User comments : 0

More news stories

Warm US West, cold East: A 4,000-year pattern

Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, ...

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

ESO image: A study in scarlet

This new image from ESO's La Silla Observatory in Chile reveals a cloud of hydrogen called Gum 41. In the middle of this little-known nebula, brilliant hot young stars are giving off energetic radiation that ...

First direct observations of excitons in motion achieved

A quasiparticle called an exciton—responsible for the transfer of energy within devices such as solar cells, LEDs, and semiconductor circuits—has been understood theoretically for decades. But exciton movement within ...

Patent talk: Google sharpens contact lens vision

(Phys.org) —A report from Patent Bolt brings us one step closer to what Google may have in mind in developing smart contact lenses. According to the discussion Google is interested in the concept of contact ...

Tech giants look to skies to spread Internet

The shortest path to the Internet for some remote corners of the world may be through the skies. That is the message from US tech giants seeking to spread the online gospel to hard-to-reach regions.