5 freeway through Grapevine and Tehachapi were placed under a dense fog advisory by the National Weather Service on Wednesday at 10:03 a.m. “Visibility one quarter mile or less in dense fog. Have an alternate plans if you will traveling during this time.”Guidance from the NWS for navigating foggy conditionsIf a dense fog advisory is issued for your area, it means that widespread dense fog has developed and visibility often drops to just a quarter-mile or less. If you have fog lights, use them. For more local weather alerts, visit our Weather Advisory page