Hotter and drier than normal weather is exacerbating fire conditions in Southwest Washington and Northwest Oregon, but some relief might come later in the week.
“Big picture: it’ll be getting cooler and we’ll have more a typical marine influence by Thursday afternoon through Friday,” said Andy Bryant, a hydrologist with the National Weather Service. Conditions are going to be hot and dry until then.
The weather service has issued a heat advisory and a red flag warning until 10 p.m. tonight.
Temperatures are excepted to hover between 90 and 95 today, humidity will be between 15 and 30 percent and east and southeast winds will blow around 7 mph.
According to the weather service, the conditions are ideal for plume-dominated fires. A plume dominate fire is one with behaviors governed primarily by local wind circulation above the fire rather than the wind itself.
The U.S. Forest Service documents say fires like that can move uphill quickly in heavy fuels. In light fuels, the fire column can collapse, forcing air to rush toward the ground in every direction, which pushes the fire outward in all directions.
Because of the nearby fires ambient air quality in much of Clark County is unhealthy, according to the Southwest Clean Air Agency. At 1:30 p.m. Tuesday, Vancouver’s air quality measured 110 parts per million, and Yacolt’s was at 85 ppm.
“Rarely in the summertime do we get this kind of bad air quality,” said Uri Papish, executive director of the Clean Air Agency.
These kind of conditions are more typical in the winter when the air is stagnant and lots of people are burning wood stoves.
But Papish said the region’s air quality suffered for several days early last month due to fires burning around the Pacific Northwest.
“This is pretty unprecedented to have this many days with bad air quality,” he said.
Bryant said conditions might improve starting tomorrow night or Thursday morning, as a marine air system begins to push inland.
The weather service is predicting a 15 to 30 percent chance of rain starting Wednesday, but with that comes with a chance for thunderstorms as well. However, what rain does come likely won’t cover the region.
“It’s not going to be widespread where everybody gets soaked. It’s going to be that some places get rain some places don’t,” Bryant said.
As the new air system moves in, it’ll bring with it increased humidity and a shift of the winds.
By mid-day Wednesday, the wind should stop moving west and begin blowing lightly to the east. Gusts are expected to be between 10 and 15 mph.
“The wind is not going to be very strong, but it’s going to be enough to gradually clear the air out,” in Portland and Vancouver Bryant said.
Thursday and Friday high temperatures should reach 78 and 75, respectively.
This is typically the dry season in the Pacific Northwest, but it has been drier and hotter than average since early August.
“Typically we don’t get that much (rain) anyhow,” this time of year Bryant said. “But basically for the past two and a half months we’ve only had one day of rain, and it was a minor amount a few hundredths of an inch.”