From 90 degrees to snow in 36 hours: Wild weather expected in Denver

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It’s popular in many regions to joke about how rapidly the weather can change. But few cities have as much right to complain about Mother Nature’s meteorological caprice as Denver, where summerlike temperatures, dangerous fire conditions and a full-fledged snowstorm are all possible in 36 hours’ time.

From September 2019: Denver hit 83 degrees. Eight hours later, it was snowing.

The Mile-High City and its surroundings, including Boulder, are set to endure a major dose of weather whiplash in the next few days, with highs projected to peak around 90 degrees on Thursday before a blast of snow and cold Friday night. On Thursday, a red-flag warning is in effect for “critical” wildfire concerns stemming from recently abnormally hot and dry conditions. A winter storm watch is in effect from Friday afternoon to Saturday morning for the likelihood of accumulating snowfall.

A major concern is the potential for power outages on Friday night when the heavy, wet snow may cling to trees and power lines. The outage risk is particularly acute because “leaf out” has already occurred on trees in the region, meaning branches will be more prone to snapping. Winds gusting up to 35 mph won’t help matters.

The National Weather Service in Boulder tweeted that “downed tree-branches and power outages will be a significant threat.”

In the higher elevations west of Denver, the potential exists for more than two feet of snow. The same fast-moving cold front bringing the crashing temperatures and snow to Colorado is also sparking severe weather from the Upper Midwest to the southern Plains. Ahead of the front, record heat is surging toward the East Coast.

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Snow in Denver in mid- to late May isn’t unprecedented, but the predicted accumulations of 4 to 12 inches in the greater region mean this event could be historically significant.

“Basically, the last time we’ve had significant snow in May, we had 5.1 [inches] in 2019 on the 21st,” said Frank Cooper, a meteorologist at the Weather Service in Boulder. “And before that it goes into the 1930s and 1940s.”

He noted that Denver’s biggest late-season snowfall, 11.5 inches, occurred on May 20, 1931. Confidence was still moderate regarding how much snow would fall in the city this time, but winter storm watches had already been upgraded to warnings in the high terrain west of Denver.

“Areas west of I-25 could see … quite a bit more snow,” Cooper said. “In Denver we’re looking at that 3-to-5-inch range.”

The Weather Service’s forecast discussion for the region stressed that the accumulation forecast in Denver is “complicated” because of uncertainty over how fast cold air will arrive, how hard the snow will fall and how much of it will stick.

Fire threat and heat first

Before the first flakes fall, however, other hazards face the city, including the risk of wildfires.

The National Weather Service Storm Prediction Center has drawn a critical fire weather zone that encompasses much of the Southwest, including Denver, Las Vegas, Albuquerque and Colorado Springs. Developing low pressure in Colorado will induce westerly winds of 20 to 30 mph across the southern and central Rockies that, when added to relative humidity values below 25 percent, will turn the ambient environment into a tinder box.

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“Rapid fire spread is possible on any existing fires and from any new fire starts,” the Storm Prediction Center wrote.

Temperatures will be unseasonably high, peaking around 90 degrees Thursday. The average high this time of year is 72 or 73. If Denver manages to surpass 92 degrees, it will set a record for May 19.

By Thursday night, that same low-pressure system will tug a strong cold front through the Rockies; it will push through Colorado late Thursday night, turning winds northerly and allowing temperatures to plummet. Lows will dip into the lower 40s by early Friday morning, and readings will struggle to climb during the day. In fact, highs will end up just shy of 50 degrees. Light rain should arrive by early evening.

Frigid air pouring into the Centennial State will flip rain over to snow in Denver by Friday night, with a few hours of moderate snow likely overnight. Most of the precipitation should wrap up by Saturday morning, but not before garnishing the High Plains with some flakes and shrouding areas in the Denver-to-Boulder metro area beneath a blanket of white.

Colorado Springs, about 70 miles south of Denver on Interstate 25, could also see 3 to 5 inches of snow. If that occurs, it will mark the city’s latest 3-inch-plus snowfall ever observed, beating out the current record by five days.

Chilly weather will stick around in Denver through the weekend, with a gradual return to highs in the 80s by the middle of next week.

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