Dense Fog and Poor Air Quality Continue in Oregon While Home Heating Fires Rise
Fire safety is a burning issue this week as the National Weather Service (NWS) predicts that a stubborn high-pressure inversion is locking in repeated rounds of dense valley fog with near-zero visibility at times and sunshine and warmer temps at higher elevations, keeping Oregon dry into early next week. But this is also the season for increased house fires as temperatures stay low.
Oregon Weather For The Week Ahead
A strong high-pressure “inversion” pattern prevails over the Pacific Northwest, keeping Oregon dry through at least Jan 20-21 while trapping dense valley fog and pollution near the ground.
The NWS issued a stagnant air alert, predicting that light winds and limited air movement will lead to a period of stagnant air.
The high-pressure cell remains over the Pacific Northwest into next week with a 90% chance of continued dry weather through at least Jan. 20-21st. In valleys below roughly 1000 ft, fog and low clouds continue into Thursday, while areas above 1000 ft will remain much warmer and drier, with clear skies.
But as offshore flow strengthens on Friday, breezy or gusty east winds are expected to impact the Cascades gaps/foothills, western Columbia River Gorge, and parts of Portland, bringing an end to the prolific fog and low clouds in the lowlands that the easterly winds reach. More protected areas, such as the southern Willamette Valley, may still see fog linger overnight.
There’s a 70-95% chance of visibility below 0.25 miles for much of the I-5 corridor (including Portland-Vancouver) through Thursday morning, and stagnant air could degrade air quality. Central Oregon will experience cold overnight lows (Bend lows are forecast around 19-22°F), even while days stay sunny.
The NWS also issued an urgent dense fog advisory early this morning for Tualatin Valley-Portland West Hills and Chehalem Mountain, including the cities of Hillsboro, Beaverton, Skyline Drive, Forest Grove, Sherwood, Tigard, Tualatin, The Oregon Zoo, Sylvan Hill, Farmington, Chehalem Mountain, Sylvan, Rockcreek, and Aloha.
The dense fog advisory is effective until noon today, while the air stagnation advisory remains in effect until 4 AM PST on Friday.
| Advisory | Trigger | Primary risk | Examples of impacted areas | Timing in this forecast |
|---|---|---|---|---|
| Dense Fog Advisory | Visibility around 0.25 miles or less | Driving hazards and near zero visibility | Tualatin Valley / Portland West Hills / Chehalem Mountain | Until noon PST today |
| Air Stagnation Advisory | Light winds and limited air movement | Pollution trapped near the surface / air quality degradation | Inner Portland Metro / Inner Vancouver Metro | Until 4 AM PST Friday |
Oregon Home Heating Fire Safety
The Oregon State Fire Marshal (OSF) reminded Oregonians yesterday that, with overnight temperatures below freezing and recent home-heating-related fires, fire safety is paramount. The agency has investigated 10 home fires across the state, with various causes, and three fire-related deaths were reported to OSF in the first two weeks of this year.
In Portland, a 64-year-old woman died after being taken to the hospital after a house fire on Monday morning. Investigators suspect the cause of this fire is the use of an extension cord on an auxiliary space heater. Last weekend, the Baker City Fire Department responded to two home fires related to fireplaces and chimneys.
According to the National Fire Protection Association, nearly half of heating equipment fires (46%) occurred in the three months from December through February.