* WHAT...Visibility 1/4 mile or less in dense fog. * WHERE...San Francisco, Coastal North Bay Including Point Reyes National Seashore, San Francisco Peninsula Coast, Northern Monterey Bay, Southern Monterey Bay, and Northern Salinas Valley/Hollister Valley and Carmel Valley. * WHEN...Until 9 AM PDT this morning. * IMPACTS...Low visibility could make driving conditions hazardous.