PATCHY DENSE FOG DEVELOPING OVERNIGHT... Widespread fog with visibilities 1 mile or less developing across coastal areas overnight. The fog will be locally dense at times, with reduced visibilities as low as 1/4 mile or less. A Dense Fog Advisory may be needed if widespread dense fog develops. Motorists should be prepared for sudden changes in visibility. Use low beam headlights and keep a safe distance between your vehicle and the one ahead of you.