The fog typically begins forming around the area of the Columbia River .
The fog typically expands , sometimes covering the land to distances as far away as LaPine , Oregon , almost 150 miles ( 240 km ) due south of the river and into south central Washington .
The fog typically begins forming around the area of the Columbia River and expands , sometimes covering the land to distances as far away as LaPine , Oregon , almost 150 miles ( 240 km ) due south of the river and into south central Washington .