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One-year anniversary of destructive downslope Utah windstorm

Downed tree on the west side of the Utah State Capitol building after a massive downslope windstorm blew through Salt Lake County on Sept 8, 2020. (Nick Wyatt, KSL Newsradio)

SALT LAKE CITY — Today marks one year since an early-morning downslope Utah windstorm wreaked havoc in Weber, Davis, and Salt Lake Counties

Many people woke up on Sept 8, 2020, to find their power was out. As they drove into work, they noticed countless trees ripped from the ground at their roots. Closed roads made the commute a nightmare. 

Approximately 4,500 trees were uprooted by the 99 mile-per-hour winds. Close to 200,000 people were without power. The devastation closed several major roadways. 


Former Utah Gov. Gary Herbert declared a state of emergency for Utah on September 10 and many mayors did the same for their cities. 

What’s a downslope windstorm? 

Downslope windstorms are an uncommon phenomenon. Essentially, it starts when cold air accumulates in Wyoming and pushes over the Uinta Mountains. 

“The Uinta Mountains help to focus those strong winds from that cold air over the Wasatch and down into Weber, Davis, and Salt Lake counties,” said Christine Kruse, lead meteorologist with the National Weather Service Salt Lake City.

Those strong winds combined with the existing wind along the Wasatch Front. This combination created a windstorm of the likes we have not seen since 2011

Complicating matters further, the windstorm hit early in the year. Many of the big trees which later ended up on their side still had most of their leaves. 

“If you think about those strong winds hitting those trees with those leaves, it’s like a sail. It’s going to pull even more trees down,” Kruse said. 

What about this year? 

Christine Kruse said weather patterns are very different this year. She explained we are not getting any early cold fronts. In fact, another period of excessive heat is here for the next several days. 

Fortunately, the National Weather Service is skilled at predicting such weather events. 

“You can see those ingredients sometimes 2, 3, even 4 days out. You can start to say ‘there’s a threat of this coming, get prepared,” said Kruse. 

She said downslope windstorms are possible again this year. However, the strength of last year’s is very unlikely.