How is the amount and location of burning determined each day?
Open burning in the Willamette Valley is limited by frequent atmospheric inversions and prevailing northerly winds that tend to inhibit the escape of smoke from the area. Open burning is allowed when the smoke can be expected to rise to a satisfactory height and be carried away from the Willamette Valley on the shortest possible trajectory. Field burning is typically done in areas along the west side of the state, (Washington, Polk, Yamhill, Benton and Lane Counties) when the smoke will drift to the west and typically done in the central and eastern counties, (Clackamas, Marion and Linn) when the smoke will drift to the east. Since much of the Valley’s acreage is concentrated in these central and eastern areas, the heaviest burning is done under west-to-east wind conditions. This often occurs in advance of a storm when winds are strong, there are no inversions, and the atmosphere is turbulent and capable of dispersing field burning smoke.
