The Chris Mountain Fire, burning 12 miles west of Pagosa Springs in the San Juan National Forest, had grown to 459 acres and was zero percent contained as of Monday.
Fire officials expect the blaze to grow in size during the next five days.
The fire started June 28 from a lightning strike and quickly grew to 120 acres. It has more than doubled in size since then.
A red flag warning has been issued through the remainder of the week for what is expected to be high winds, dry fuels and low humidity.
“Red flag warning means erratic winds, higher temperatures and higher fire behavior,” said Anne Reid, spokeswoman for the Rocky Mountain Incident Management team.
Archuleta County issued mandatory evacuations for Forest Road 628, which accesses mostly ranches, but no infrastructure had been lost as of Monday.
Reid said firefighters are focused on storm patterns and anticipating which direction winds will blow. If winds and topography align, the size of the fire will significantly increase.
“We are using a lot of aviation resources right now. Aviation is really handy to suppress the fire,” Reid said. “It doesn’t necessarily knock it out, but it slows down the intensity so firefighters are able to work the line.”
Reid said one of the main goals is to prevent the fire from spreading downslope into the Devil Creek drainage.
On Sunday, aviation resources were able to assist in moderating fire behavior along the northern and eastern edges, slowing the fire’s progress. Reid said thunderstorms predicted Tuesday and onward will create unsafe flying conditions.
“The red flag warning means higher wind speeds,” she said. “The aircrafts may not be able to launch, so it takes those valuable resources out of play.”
Higher temperatures and stronger winds will also affect two other wildfires in the southwest corner of Colorado.
The Coal Mine Fire began on June 26 and was 50% contained as of Monday. The 286-acre fire is 18 miles south of Pagosa Springs. The cause has not yet been determined.
Also caused by lightning, the Arkansas Loop Fire reached 127 acres as of Monday and was 50% contained. The fire ignited 21 miles south of Durango on June 27.