There are many misconceptions swirling around about the mechanism and role of Utah's lake effect storms in the creation of our legendary powder snow. Keep in mind, many a wayward skier or shredder has returned home from a Utah trip after a particularly deep or memorable lake effect storm only to sell a good number of their worldly possessions, quit their job and move to Utah. In fact, many of my own friends and even my roommate has succumbed to this level of lake effect adoration. It's...kind of a big deal.
We'll summarize the lake effect phenomenon for you utilizing the expertise of famed University of Utah meteorologist and 'Professor Powder,' Jim Steenburgh. Steenburg is the author of an excellent book titled 'Secrets of the Greatest Snow on Earth.' It is mandatory reading for anyone remotely interested in Utah's incredible snow and can be found here!
THE GREAT SALT LAKE
Meteorologists lament the difficulty of accurately predicting lake effect storms and their storm totals. It's a puzzling enterprise, thanks to the unusual qualities of the Great Salt Lake. This saline body of water runs north to south and is the largest body of water in the Western United States. The lake itself is not very deep and because of this, the surface area of the lake fluctuates wildly depending on the water table and storm frequency. For example, at its average size, the average lake depth is only around 16 feet! Steenburgh refers to the lake as more of a 'massive puddle.'
The Great Salt Lake is, unsurprisingly, one of the saltiest bodies of water in the world with salinity levels fluctuating around the lake between 12% and 27% salinity. If you'll travel in time back to your high school science course, you'll recall that saltwater lowers the freezing point of water. Thanks to the heavy salt load, the majority of the Great Salt Lake never freezes, allowing it to interface directly with the surrounding atmosphere.
WEATHER PATTERNS
According to Steenburgh, our lake effect storms occur when fairly cold westerly, northwesterly, or northerly storms move across the lake toward the Wasatch Mountains. When the cooler air moves atop the warmer (unfrozen) surface of the lake, heat and moisture saturate the atmosphere. The final ingredient is upstream moisture, meaning the air mass moving in must have a relative humidity content of at least 60%. This produces strong updrafts which results in a more intense lake effect phenomenon.
The final ingredient is convergence, when air streams collide over the surface of the lake resulting in lift which assists the lake effect mechanism. Around sunset, the air surrounding the lake cools faster than the air above the relatively warm lake water. The difference in temperature triggers a land-breeze convergence which has been known to trigger snowfall rates of nearly three inches per hour! For this reason, lake effect snow tends to occur more frequently at night or in the morning.
GEOGRAPHY
Thanks to the Great Salt Lake's north to south orientation, the greatest impacts of lake effect storms occur to the south and east of the lake. That puts the Cottonwood Canyon resorts, Solitude Mountain Resort, Brighton, Snowbird, and Alta Ski Area in the hot seat. Storms traveling across the Great Basin slam into the Wasatch Mountain range, which abruptly transitions from around 4,300 feet to 11,000-foot peaks. Resorts in the Wasatch Back can also be affected, though the results aren't quite as deep at Park City Mountain and Deer Valley. If the flow of the weather pattern arrives from the west or southwest, Powder Mountain and Snowbasin may see a little lake effect action.
In an average year, the Great Salt Lake is responsible for 5-10% of the snow that falls in the Cottonwoods—most are surprised to learn this!
TIMING
As with all good things, timing is everything. Lake effect storms are most common between October and December. After a lull in January and February, lake effect storms often build momentum once again in March and April. Lake effect storms tend to work in a positive feedback cycle. Frequent lake effect events begat more lake effect events. During dryer periods, lake effect storms are less common.
LAKE EFFECT MYTHS
Much of the hype surrounding lake effect storms includes many misconceptions. One of the largest is that it is not actually moisture from the Great Salt Lake that is increasing the snow totals. The lake itself is a mechanism for enhancing the atmospheric conditions that result in deeper dumps. Despite the romance of imagining saltier snow, the salt from the lake is too heavy to climb into the upper atmosphere and fall back to earth in flake form. Though there have been incidents where salt was detected in the snowpack, these are related to dust storms or wind events.
If you want to learn more, you'll need to check out Jim's book, 'Secrets of the Greatest Snow on Earth.' It's a delightful read that includes fascinating info, folklore and secrets of the beloved Wasatch Mountains.
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