WEATHER
How does lake effect snow work? A primer
Feb 3, 2020, 10:37 AM | Updated: 11:20 am
Lezlee Huff's pickup truck is buried under lake effect snow in Millcreek, Feb. 3, 2020.
SALT LAKE CITY — Lake effect snow buried communities across the Wasatch Front on Monday and forced schools to cancel as a winter storm swept into the region.
But what is the lake effect, and why does it mean more snow for some spots and not others? Here’s a guide.
How lake effect snow happens
According to meteorologists, lake effect snow occurs when cold, dry air sweeps over a body of water like the Great Salt Lake, picking up warmth and moisture in the process.
Lake effect snow does not tend to be a factor when a storm system passes over a frozen body of water. The Great Salt Lake, which is much saltier than the ocean, does not typically freeze.
Photo illustration: The National Weather Service
But the lake effect needs more than water. The wind speeds must also be just right. National Weather Service forecaster Brian Donegan wrote in 2016 that when the winds are too strong, the air mass cannot pick up the necessary amount of moisture to create a lake effect.
Temperatures also play a role in triggering lake effect snow. That’s why you’re less likely to see this type of storm in the fall or spring.
How do you know where the snow will go?
Trent Bassett snapped this photo of tables at the University of Utah Orthopedic Hospital on Monday, Feb. 3, 2020.
Wind direction and geography combine to determine what happens with all the excess moisture picked up after the system passes over a lake.
In Utah, because the Great Salt Lake is surrounded by tall mountains to the east, the moisture gets “wrung out” like a sponge as the air mass encounters those hills.
Depending on which direction the wind is coming from, that could mean the lake effect is strongest to the north, south or east of the Great Salt Lake. The larger the surface area of the lake is covered by that wind, the more moisture it will sop up.
The greatest snow on Earth
All of those factors combine to create spectacular snowfall amounts every year in Big and Little Cottonwood Canyons, east of Salt Lake City. The road through Little Cottonwood Canyon gets more fresh powder every year than any other year-round road in the lower 48 states.
Ski resorts are the main beneficiary: Alta and Snowbird average more than 500 inches of snow every year. Other resorts in the area also pick up snow in the hundreds of inches annually.
The conditions keep Utah Department of Transportation crews busy. It takes a small army of UDOT plow drivers to keep Little Cottonwood Canyon – and all the other roads in the region – clear after a snow storm.
