OAKLEY (CBS SF) – A dense fog advisory covering areas of Contra Costa County east of the Willow Pass has been called by the National Weather Service in San Francisco.

The advisory, which covers the cities of Pittsburg, Antioch, Brentwood and Oakley and adjacent communities and rural areas, is in effect until 11 a.m. Sunday.

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Visibility in affected areas could drop to a quarter mile at times, National Weather Service Meteorologist Scott Rowe said tonight. That fog could make driving difficult at times, he added.

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The fog, Rowe said, is a result of moisture from recent rains, along with nighttime cooling and slight or nonexistent winds combine for such fog events, Rowe said.

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These conditions are ripe in both the Sacramento and San Joaquin valleys, where widespread dense fog is expected, Rowe said. Far eastern Contra Costa is close enough to the northern San Joaquin Valley to be on the edge of that activity, he said.