Freezing Fog Advisory- Issued when fog may reduce visibilities to less than 1/4 mile. In addition, the fog will freeze on exposed surfaces and cause black ice formation on roadways, bridges and sidewalks. Action: Drivers should slow down and use their headlights.
Freezing fog - A suspension of numerous minute ice crystals in the air, or water droplets at temperatures below 0 Celsius, based at the Earth's surface, which reduces horizontal visibility; also called ice fog.
Used to describe the phenomena when fog is present and the air temperature is below 0ºC. It is reported as "FZFG" in an observation and on the METAR.
FREEZING POINT/FREEZE ...
Freezing fog occurs when liquid fog droplets freeze to surfaces, forming white rime ice. This is very common on mountaintops which are exposed to low cloud.
Freezing FogA fog the droplets of which freeze upon contact with exposed objects and form a coating of rime and/or glaze. Freezing LevelThe altitude at which the air temperature first drops below freezing.
According to the National Weather Service, some of the obstructions to visibility include blowing and widespread dust, fog (including ~ and patchy fog) haze, mist, sand and blowing sand smoke, blowing spray, and volcanic ash. It is reported as "X" in an observation and on the METAR.
Hoar frost must not be confused with rime, which derives from ~ or glaze which forms as a continuos thick layer of ice, rather than individual frozen droplets.
Weather Facts ...
NOAA National Weather Service - Cite This Source - This Definition
Browse Related Terms: Aerosol, Dense Fog Advisory, Evaporation-mixing Fog, ~, GF, Ground Fog, Ice Fog, Nieve Penitente, Rain Induced Fog, Shallow Fog, Steam Fog, Tule Fog, Upslope Fog ...
See also: What is the meaning of Freezing, Water, Fog, Surface, Temperature?