Dense fog and air stagnation advisories remain in effect into this morning.
High pressure over the area is keeping conditions stagnant for an extended period in the Mid-Columbia, according to the National Weather Service's Pendleton office. That means a dense fog advisory will be in effect until 10 a.m. Monday, while an air stagnation advisory is in place until noon.
Residents can expect periods of dense fog throughout the morning, with visibility reduced to less than a quarter mile overnight. Freezing fog could create poor road conditions, while the stagnation could lead to poor air quality, which could be a health issue.
The air stagnation advisory is caused by a limited movement of an air mass across the affected areas of Washington and Oregon. The weather service said this causes pollution to increase.
Drivers should slow down, use their headlights and allow plenty of distance between themselves and the cars in front of them, the weather service said.
The weather service called for an overnight low of 26 degrees Sunday into Monday, with calm wind. Patchy fog is predicted between 10 a.m. and 4 p.m. today, with areas of dense freezing fog. A high temperature of 33 degrees is predicted for Monday, with calm wind.
The weather service predicts the fog will lift by New Year's Day, when a high of 37 degrees and mostly sunny skies are predicted.