Dense Fog Again Tonight and Friday Night, Be prepared for sudden drops in visibility if traveling, What To Expect: Areas of dense fog resulting in sudden changes in visibility, with visibility less than 1/4 mile in some places., When: 10PM tonight thru 10AM Fri, then from 10PM Fri thru 10AM Sat., Safety: Slow down & increase following distance. Use low-beam headlights. Consider delaying travel until visibility improves.