A fire weather watch has been declared in the foothills of the Colorado Rockies, where relative humidity could plummet to below 10 percent Thursday as southwesterly winds gust over 40 mph. While the fire burns, Denver is awaiting its first measurable snowfall of the season and is approaching a record-late start to the snowy season.
Much of Colorado is gripped by a moderate-to-severe drought, according to the U.S. Drought Monitor, a byproduct of unusually warm and dry weather that has prevailed since early summer. Seven percent of the state remains in “extreme” drought, and although there has been a marked improvement year over year, the lingering effects are still manifesting themselves in a continued fire danger.
On Wednesday, Denver was forecast to experience afternoon highs approaching 40 degrees Fahrenheit, with lows dropping to near 20 on Wednesday night. Highs will rise into the 50s on Thursday and the 60s by Friday, but with little moisture in the air, relative humidity will dwindle. It will hit rock bottom in the lee of the mountains, where “mountain waves” and strong downslope winds could gust above 50 mph.
That could affect efforts to combat the Kruger Rock Fire, which has prompted evacuations near Estes Park. Highway 36 has been shut down, with a mandatory evacuation order in effect for Meadowdale and south to the Boulder County line. That order includes Big Elk Meadows and Pinewood Springs.
“Evacuate the area immediately and as quickly as possible,” wrote the Larimer County Sheriff’s Office around noon Tuesday. “Do not delay leaving to gather belongings or make efforts to protect your home or business.”
Strong winds and low humidity will combine to worsen already hazardous conditions and create an environment that could support additional fire spread, perhaps requiring more evacuations. Estes Park is not directly affected by the fire, but since the main road into town from Denver and Boulder has been closed, motorists are required to take Big Thompson Canyon Road or Highway 7.
Estes Park was fringed by the East Troublesome Fire last year, which was first reported Oct. 14. It ultimately went on to prompt evacuation orders for 35,000 people, burn 193,812 acres and even hop the continental divide and reach western Estes Park. Widespread drought and a littering of dead trees toppled by bark beetles catalyzed the fire’s growth and spread. Estes Park had already been threatened by the Cameron Peak Fire, which torched 208,913 acres and became the state’s largest wildfire on record. All 20 of Colorado’s largest wildfires on record have occurred in the past 20 years.
Inveterate drought and rising temperatures, linked in large part to human-induced climate change, have been amplifying fire conditions in a state known for its meteorological caprice. This year’s recent drought and lack of snowfall is particularly problematic as it extends into the windy season.
“For Denver, the latest [first] measurable snowfall on record was November 21, 1934,” said Zach Hiris, a meteorologist at the National Weather Service in Boulder. “There’s a few snow showers around [Wednesday], doesn’t look like we’ll have any accumulation at the airport. It looks like we’ll likely surpass that record date.”
Denver has also now gone without measurable snow for 209 straight days, the third-longest streak on record, which would be broken on Friday.
There is some snowpack in the mountains, but Denver has recorded only 0.14 inches of precipitation since the start of October. Temperatures running 3 to 5 degrees above average in the same span have helped spur evaporation of what little moisture remains in vegetation and dry the ground even more. June through September 2021 was the warmest such four-month span on record in Colorado.
Bob Henson, a meteorologist and science writer based in Boulder, tweeted that Denver is having its fifth-driest and fifth-warmest fall on record.
“We’ve been dealing with drought sort of all year in the Denver area,” said Hiris. “But especially speaking to this year, the lack of snow has really been an issue for most of our high country. We just issued a fire weather watch for most of our foothills. Any time we’re not getting the early-season snowfalls, you’re letting those fuels dry out for longer and longer.”
Hiris described 2020 as “interesting.” Even though snow fell during Labor Day weekend, the pattern flipped back to hot and dry, allowing last year’s fierce blazes to continue into the fall.
“Basically anywhere that hasn’t seen snow, the fuels are ready to burn” this year, Hiris said. “The lack of precipitation in the past few months is really playing a role.”
High pressure is in control over the Four Corners region (the junction of Utah, Arizona, New Mexico and Colorado), which will keep Denver dry for the foreseeable future.
What is more, jet stream winds out of the west have been amplifying “mountain waves,” which bring stronger winds in the higher terrain.
Hiris noted that human-induced climate change is playing a role in a trend for fire seasons to extend further into autumn.
“There’s always going to be some variability, but from what we’ve seen from the Colorado Climate Center, the trend is drier summers and drier falls and later and later snowfalls,” he said. “Our snowpack season is getting trimmed down, too.”