Autumn weather that careened between extremes has had a profound effect on prescribed burning plans on public lands in Northeastern Oregon.
“It was a different sort of fall,” said Steve Hawkins, fuels program manager for the Wallowa-Whitman National Forest.
The season swapped the typical sequence, starting with temperatures more typical of winter, then transitioning to a long spell of abnormally warm and dry weather.
Crews ended up burning about 2,500 acres, mostly in three areas — Goose Creek about 20 miles northeast of Baker City; near Unity Reservoir; and in the Wolf Creek area northwest of North Powder.
That’s more acreage than Hawkins expected would be burned back in early October, after a series of Pacific storms doused the region with rain and snow.
During that time, the grass and pine needles that carry flames across the ground were too wet to sustain blazes.
The 2,500 acres burned is about one-third of the area that’s typically treated during the fall, Hawkins said.
Forest officials use prescribed fire to accomplish a variety of tasks, including reducing the amount of combustible material on the ground, and spurring the growth of forage for wildlife and livestock.
Although the weather changed dramatically after the middle of October — 30 days in a row passed without measurable rain at the Baker City Airport, and the high temperature was above average on each of the first 20 days of November — two factors conspired to make burning conditions marginal, he said.
First, as the period of daylight shrinks with the approach of the winter solstice, the burning “window” — when conditions are conducive to a fire that spreads at a reasonably rapid rate — is confined to three or four hours during the afternoon, Hawkins said.
Second, the long dry spell that stretched from Oct. 20 through Nov. 18 was caused in large part by a persistent high pressure ridge that created a temperature inversion and resulted in gentle winds.
In such conditions cooler air is trapped in valleys, and smoke from prescribed fires tends to settle rather than disperse, Hawkins said.
Even though some areas slated for prescribed burning dried sufficiently, the stagnant conditions made it difficult to burn without violating smoke guidelines, he said.
The potential for smoke was one reason that prescribed burning proposed for the Washington Gulch area near Baker City was canceled for this fall, Hawkins said.
The situation was somewhat different when it comes to burning piles of slash.
During the early autumn, when soggy ground rendered widespread underburning impractical, conditions were better suited to burning piles, he said.
But the dry spell lasted so long that eventually officials had to postpone some pile-burning due to the potential for flames to spread from the piles, Hawkins said.
“We didn’t want them creeping onto private land,” he said.
With wintry weather forecasted to return late this weekend and continue through Thanksgiving, Hawkins said Thursday that it’s likely that there won’t be any more widespread prescribed burning this fall.
Pile-burning, which can be done even with snow on the ground, will continue.
An interactive map of prescribed burning on the Wallowa-Whitman is available online at https://go.usa.gov/xVseH