(CNN)Hundreds of homes have been lost after two wildfires started and grew quickly Thursday as high winds whipped through the Front Range in Colorado, forcing tens of thousands of residents from their homes, the Boulder County sheriff said.
Sheriff Joe Pelle estimated 580 homes or other structures in and around Superior may have been lost.
A shopping center and a hotel in Superior also were engulfed by the flames.
"Historic" 80-100 mph winds, with gusts in the state as high as 115 mph, fed the wildfires that injured at least six people, prompted a hospital to send patients elsewhere and forced the evacuation of Superior and Louisville near Boulder.
The Marshall Fire had burned at least 1,600 acres and had spread east across Superior and Louisville, the sheriff said. The other fire is known as the Middle Fork Fire, but Pelle said it was attacked quickly and "laid down." Authorities were keeping an eye on it, the sheriff added.
Two homes burn in Louisville, Colorado, on Thursday.
There were no immediate reports of civilian casualties or missing people, Pelle said. One law enforcement officer suffered a minor eye injury from blowing debris.
"I'd like to emphasize that due to the magnitude of this fire, the intensity of this fire and its presence in such a heavily populated area, we would not be surprised if there are injuries or fatalities."
The sheriff said any evacuees who have Covid-19 should go to a recovery center at the Mount Calvary Lutheran Church in Boulder.
Gov. Jared Polis, who declared a state of emergency for the area, said the flames were traveling the length of a football field in just seconds.
Firefighters battle a structure fire in Superior on Thursday.
"Very little time to get out, very little time to even get the most important parts of your life and, yes, it'll be a difficult process for Colorado families who are directly affected to rebuild their lives," he said.
Louisville and Superior are about 4 miles apart, not far from Boulder.
At least six people are being treated for injuries related to one of the fires, a spokesperson for UCHealth told CNN. Kelli Christensen said no more information was available for the patients, who are at UCHealth Broomfield Hospital.
Another hospital, Avista Adventist Hospital, was prompted to evacuate its patients and employees. The facility has 114 beds, according to its website. Authorities said hospital officials were more concerned about smoke than the flames that were only a few blocks from the facility.
"If you're in the area, please act quickly," the Boulder County Office of Emergency Management tweeted to Louisville residents.
Video from CNN affiliate KUSA showed several homes in Louisville on fire.
Heavy smoke made visibility difficult in Louisville, Colorado.
The US Census Bureau says Louisville has about 21,000 residents and Superior has 13,000.
"We are in the midst of a truly historic windstorm across the front range, foothills and urban corridor," the National Weather Service office in Boulder said Thursday afternoon.
Widespread wind gusts of 80-100 mph have been observed, the weather service said, and "a handful of sites in Rocky Flats have seen several hours worth of gusts 100-115 mph."
Combined with relative humidity below 20% and ongoing drought conditions, the extreme winds were fueling rapid fire spread.
County residents were asked not to waste time if they see flames.
"Boulder OEM is getting many calls about residents seeing fire. IF YOU SEE FIRE, EVACUATE. Go east, go north, but leave immediately," the office tweeted.
The hurricane-force wind gusts were attributed to "exceptional mountain wave amplification," which is a major increase in wind speed as air flows over and down the mountains into the lower elevations that can occur under very specific atmospheric conditions.
Strong, sustained winds of 20 to 40 mph with gusts between 40 to 80 mph were still occurring across the Colorado foothills Thursday evening. A high-wind warning was extended across this region until 8 p.m. MST.
Winds should gradually weaken through the evening hours and should diminish by the morning, meteorologists said.
By morning, the region will experience "weather whiplash," going "from fire to snow," according to the weather service. An advancing cold front will push into the area and bring snow showers to foothills and front range by sunrise.
A winter storm warning is in effect for the region beginning at 5 a.m. MT Friday and calls for 5-10 inches of snow by Saturday. The combination of heavy snow and winds associated with the front and terrain will create treacherous travel conditions at time.
