Daytime heat, evening wind drive fires’ growth
Wind and unusually dry fuels — mainly plants — are contributing to the Methow Valley fires’ progressions according to fire behavior and weather analysts.
Scott McDonald, fire behavior analyst with the Northwest Incident Management Team 8, which was managing the Cedar Creek Fire through Monday (July 26), said the extreme heat wave in late June contributed to the fire season we’re having now.
“Even though the snow pack wasn’t too bad out here, it went away really quick,” he said during a community fire meeting July 21 at Mack Lloyd Park in Winthrop. “It was here and then it was gone and that kind of started setting our fuels up in a position that put us about four weeks ahead of where we should be.”
The topography of the area is also complicating firefighting efforts, McDonald said, but he told residents Wednesday that the area needs rain to feel real relief.
“Our fuels are dry and without any relief from the weather, they’re going to stay dry, and fire behavior is going to stay fairly active,” he said.
With no precipitation in the forecast, firefighters hope for some humidity recovery in the evening — when plants and soil release some of their retained moisture. However, crews for both fires have noted in their briefings little humidity recovery overnight.
“Part of it is the ongoing drought,” said Greg Koch, a forecaster with the National Weather Service’s Spokane office, on Monday. Plants and soil don’t have much residual moisture to give up, he said.
“We’ve also had a pretty persistent westerly flow pattern for wind, and that wind coming up and over the Cascades and then coming back down again, that action of descending air dries the air,” Koch said.
Unpredictable fire behavior due to later afternoon and evening winds has been a common lament during briefings from fire officials on both the Cub Creek and Cedar Creek fires. Increased fire behavior in the evening due to wind has led to a handful of late-night evacuations in the past week, including one for an area around Sun Mountain Lodge and another Sunday night for the Pine Forest development.
“Our goal is, we don’t evacuate anyone after the hours of darkness,” Maurice Goodall, Okanogan Emergency Management director, said at the July 21 community fire meeting at Mack Lloyd Park. The goal means Emergency Management has been proactive with evacuations — asking people to leave before their homes are in imminent danger — to avoid a last-minute dash to safety if the wind shifts.
On Sunday (July 25), Team 8 crews were conducting back burning operations south of Sun Mountain in an effort to slow the fire’s progression. Later that evening, crews encountered what Mark Rapp, of Team 8 operations, called “squirrelly winds.”
“We got some spots outside the line,” he said.
Four type 1 helicopters worked until dark Sunday to control the spot fires. Some fire got into residential areas that were evacuated in the Wolf Creek area, but Rapp said no structures were believed to be lost.
That weather pattern — warm during the day with wind coming through the valleys in the evening — is common this time of year in the Methow Valley.
“Unfortunately that’s not good for your air quality, because that wind is pushing smoke from upstream and into your region,” Koch said. “When it cools down in the evening, that smoke gets trapped under the inversion.”
The National Weather Service has issued an air quality alert for all of Okanogan County until further notice.
Some of the flare-ups have been causing large pyrocumulus clouds, Rapp said in a briefing Monday morning, which have been visible across the valley.
“If you are observing a fire and you see a smoke column rising from that fire, a pyrocumulus cloud is cloud development on the top of that smoke column,” Koch said.
The cloud is generated by heat and moisture from the fire. In some extreme cases, the clouds can produce precipitation and lightning, though the Methow hasn’t seen that yet this year.
Forecast: more heat
Todd Carter of the National Weather Service’s Spokane office, is working with the incident management teams to evaluate the weather. He spoke to residents at Wednesday’s fire meeting in Winthrop.
“Generally the forecast in the future … we’re going to go through these patterns where we warm up a little bit for a few days and we cool down a little bit. I don’t see any record heat coming. It seems that we’re kind of locked in this pattern,” he said.
On Monday, Koch said the updated forecast for the valley includes hot temperatures, likely reaching triple digits by Thursday and lasting through the weekend.
“Some areas that have thick smoke may not get to a 100 degrees but we’re expecting it to get quite hot again,” Koch said.
While warmer temperatures may lead to drier fuels for the fire, they could also mean less wind in the evenings.
“The hotter temperatures that we may have or that we’re expecting toward the end of the week and into the weekend, may interrupt that wind cycle a little bit,” Koch said. “There may be a little bit less of that evening drainage wind once we get toward Thursday, Friday and Saturday, but … we’re just going to continue to be hot and dry with no improvement in the fuel conditions.”
While the weather is being fairly predictable, the forecast doesn’t include any precipitation, both Carter and Koch reported. Carter said Wednesday that average precipitation levels for the Mazama area are about a ½ inch in August, ¾ of an inch in September and 2 or more inches in October.
“All of you probably know that we’ve gotten more than ¾ of an inch of rain for the valley in August before. We’ve also had events in September where we’ve got more than ¾ of an inch in a month,” Carter said, adding that we’re in a La Niña year, meaning more precipitation than normal is possible. “What we’re looking for is to identify a pattern that might be conducive to bringing one of those storms to give us a little relief. … I’m not convinced we’re going to stay in the hot and dry forever — I don’t think you should be either,” Carter said.