MEDFORD, Ore. – Dense valley fog is expected to blanket portions of southwest Oregon and far northern California tonight into Friday morning, creating hazardous travel conditions with visibility dropping to a quarter mile or less. The National Weather Service in Medford has issued a Dense Fog Advisory for the Rogue Valley, Umpqua Basin, Illinois Valley, and Applegate Valley in Oregon, as well as the Klamath River, Scott, and Shasta Valleys across the California border.
According to the NWS, fog formation will begin shortly after sunset as clear skies and calm winds allow temperatures to cool rapidly, trapping moisture in valley locations. Drivers traveling along I-5 between Grants Pass and Yreka, as well as Highway 199 through Cave Junction, should prepare for sudden drops in visibility and slick pavement from moisture condensation.
Forecasters advise motorists to slow down, use low-beam headlights, and allow extra travel time for morning commutes. Fog is expected to persist through late Friday morning before gradually lifting as daytime heating improves visibility.
Calm and cool conditions will continue into the weekend, with valley fog likely to redevelop during the overnight hours Saturday and Sunday. Afternoon highs will remain mild in the upper 50s to low 60s under mostly sunny skies once fog clears.
