The value in forecasting "lake effect" storms is immense, as these disturbances are some of the most destructive weather phenomena in Utah. They ice up freeways, dump feet of snow onto city streets, snap tree branches and drag down power lines.
The more planners know about them -- when, where and how much snow to expect -- the better their response can be. They could rush snowplows to the right places, issue advisories about avoiding certain traffic routes, know whether to halt airplane traffic.William J. Alder, meteorologist in charge of the National Weather Service's regional headquarters in Salt Lake City, said lake effect storms are most likely in the fall and early winter and sometimes may strike in the spring. They are triggered by the difference in temperature between the lake and the air masses sweeping into the state.
"As you go into the fall, the lake is relatively warm," Alder explained. Cold winds flow across the lake, and if they are in the right pattern -- say to the northwest or northerly -- and if the temperature differential is right, the result is a lake effect storm.
The temperature difference needs to be 15 or 20 degrees to cause the unsettled conditions of a lake effect. That's why these storms almost never happen in the dead of winter. By then the lake has cooled enough that it's close to the prevailing air temperature.
But when the lake is warming the air, the air masses become unstable.
John D. Horel, meteorology professor at the University of Utah, noted that air masses can drain out of valleys and down mountains, converging on the lake. The masses that pool above the Great Salt Lake help to organize weather into bands that develop and become stronger as the storms build.
Warm air rises, cold air flows. Lines of squalls set up across the lake. The pattern can channel the energy of a ferocious storm into what Alder called a "narrow hose" aimed off the Great Salt Lake.
Suddenly, the storms hurtle ashore along the narrow corridor. As the air masses hit the Wasatch Mountains they are forced upward. The air cools as it rises.
Cold air can hold less moisture than warmer air, so as the updraft gets colder it dumps its precipitation. The result: a lake effect snowstorm.
A new weather station suspended in the lake, providing continuously updated data, will help with predictions, Alder said. "Any more pieces of real-time data we can get as forecasters, that's tremendous."