The pounding winds that raked the Front Range on Saturday and Monday were unseasonal, coincidental and unlikely to repeat themselves right away, weather experts said.
The 70-mph gusts and sustained winds of up to 45 mph mowed down trees and blew down branches, peeled off part of the roof at Aurora’s Range view High School, and caused numerous flight cancellations and delays at Denver International Airport.
Eastbound Interstate 70 outside Aurora was closed for a time because of the winds. Four semi-trucks and one RV blew over on I-70 between Watkins and Limon on Monday afternoon, but only minor injuries were reported.
The winds were partly caused by strong low-pressure systems in Wyoming, according to the National Weather Service. At the same time, there was a great pressure difference between the cold, damp Western Slope and the hot, dry Eastern Plains.
As a result, the Front Range, caught in the middle, became a wind tunnel, said Jim Kalina, a meteorologist at the National Weather Service in Boulder.
“This is not completely uncommon, but it’s a little out of season,” he said. “Usually, the strongest winds we get in Colorado come in January from the chinook winds. That’s our windy season.”
Kalina said the dynamic stems from bora winds, a downslope similar to the chinooks, but colder and drier. Bora winds originate from inland areas of Canada and the Arctic, rather than from the Pacific Ocean.
Bora winds usually pass over Colorado in late winter or earlier in the spring, he said.
And such winds don’t stick around. By midnight Monday, the gusts that rocked the Rockies were expected to be in eastern Montana, he said.
High-wind warnings for the Front Range expired at 7 p.m.
The Front Range will remain breezy for a few days. Wind gusts are expected to hit 25 mph through Wednesday, with 37-mph gusts Thursday. High temperatures in the 80s are expected all week, with little chance of rain.
While the winds have brought down a number of limbs across the Denver-metro region, any future damage depends on the trees’ health long before the recent winds, said Jill McGranahan, spokeswoman for the Denver Parks and Recreation Department, which oversees the city’s trees.
Trees most likely to come down in strong winds are those with shallow roots, such as evergreens, she said. Also, most big limbs that fall were sickly before.
The city doesn’t require residents to hire a tree service to inspect damage, but it’s recommended to check and trim limbs that might have cracked, McGranahan said.
“This is one of those situations where an ounce of prevention really is worth a pound of cure,” she said. “It’s best to stay on top of it before you get the high winds that will eventually bring a limb down.”
Monday’s blow was, at times, chaotic and violent, prying up a 50-foot-square portion of roof at Rangeview High. No one was injured. School is out for the summer, and the few students on campus for activities were not threatened, according to a school spokesperson.
DIA’s largest carrier, United, canceled more than four dozen flights, and delays of more than 30 minutes were common.
Xcel Energy spokesman Mark Stutz said the wind caused several dozen small outages, “galloping wires and some snap-offs” of lines. Several thousand customers were temporarily without power Monday.
A 3,200-acre fire near Telluride, which was fortunately tamped down by overnight rain and snow, remained under control Monday.
In Agate, northwest of Limon, the post office branch closed after the postmistress spotted cracks in the building from the wind, and an attached building collapsed.
Staff writers Kieran Nicholson, Howard Pankratz and Ann Schrader contributed to this report.
Joey Bunch: 303-954-1174 or jbunch@denverpost.com
