Jackson County health officials hope today's storm front will crack a pesky air inversion that has caused the Rogue Valley to flirt with violating federal clean-air standards for the first time in six years.

Jackson County health officials hope today's storm front will crack a pesky air inversion that has caused the Rogue Valley to flirt with violating federal clean-air standards for the first time in six years.

Slipping over the federal standards for particulate matter could do more than cause health problems for residents suffering from asthma and other ailments.

It also could force the county to redraw plans to deal with pollution from wood smoke, and noncompliance could even lead to the withholding of federal road money, county officials said.

"We haven't exceeded the standard since 2003, and finding ourselves out of compliance now could lead to sanctions," said Gary Stevens, manager of the county's environmental health department.

Stevens and others are banking on today's forecast for a new storm front to whisk the bad air away before federal Environmental Protection Agency standards for particulate matter are breached.

"That's our hope," Stevens said. "It may save us all a lot of time and money down the road, and save some of our neighbors some health problems."

The problems stem from an unusually prolonged stagnant weather pattern that has hovered over the valley like a lid since Jan. 9, creating an air inversion that traps pollution.

The accumulation of small particles in wood smoke reached unhealthy levels Jan. 16, when county health officials ordered a "red day" that banned wood burning in all but certified stoves within the Air-Quality Maintenance Area, which covers the heart of the county's developed areas of the valley floor and surrounding hills.

Since then, regular measurements at a test site at the intersection of Grant Avenue and Belmont Street show daily average readings hovering right around the EPA threshold of 35 micrograms per cubic liter of air.

"We've been really, really close," Stevens said.

Typically, fronts move in and cleanse the valley, but this prolonged inversion has caused particulate matter to accumulate longer than in recent winters.

"The weather's been different," Stevens said. "That's why we really need people to use their alternate heat source."

Wednesday's storm front that dropped a trace of rain on Medford weakened the inversion some but did not break it, said meteorologist Megan Woodhead of the National Weather Service office in Medford.

But it was strong enough to mix the low-lying valley air and sluice enough particulates to break the six-day-old "red day" ban on wood burning in fireplaces and non-certified woodstoves.

However, state Department of Environmental Quality records show Thursday's particulate measurements rose in the morning and fell in the afternoon similarly to readings earlier in the week.

Woodhead said a new front expected today should bring enough unstable weather to break the inversion sometime this afternoon.

"We won't be in a stagnant weather pattern any more," Woodhead said. "It will be more of that unsettled weather coming back."

Exceeding the standard could lead to the EPA listing the county as "non-attainment," which would force officials to craft a plan for attainment, Stevens said.

County officials have no idea how many non-certified woodstoves remain along the valley floor. But a requirement that they get removed upon the residents' next sale systematically will remove them, Stevens said.

"We'll see the benefits of that as time goes," he said.

Reach reporter Mark Freeman at 776-4470, or e-mail mfreeman@mailtribune.com.