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FOG




There are six different types of Fog, all having unique characteristics. Fog is another type of cloud that is on or near the surface. It can be difficult for pilots by causing icing or IFR conditions. Fog is formed when the air temperature near the ground is cooled to its dew point causing the water vapor in the air to condense becoming fog.


Simply put, when its foggy out don't fly!


The six types of fog are classified by the way it they are formed:


Radiation Fog

Radiation fog is totally safe, no need for a lead suit. Usually, a shallow fog forming in low-lying areas, also known as Ground fog. This fog is formed on clear nights, with no wind present, and doesn't dissipate until after sunrise. When the ground cools due to terrestrial radiation, the ground cools the air, and the air temperature reaches the dew point fog is formed.

This fog usually buns off quickly after sunrise. Light winds of 5 knots or greater will most likely make the fog lift and disappear.



Advection Fog

Advection fog moves sideways. (don't get it confused with convection which moves up and down.) Advection fog forms when warm moist air moves over a cold surface, usually found around coastal areas. Winds up to 15 knots is required to form advection fog. If the winds are above 15 knots the fog usually lifts and forms as low stratus clouds.



Upslope Fog

Moist stable warm air is forced up the slope of a mountain. Wind is required to move the air up slope. This type of fog, along with Advection fog may not burn off with the morning sun and can last for days.



Frontal Fog

Frontal Fog or precipitation-induced fog forms when warm moist air raises above a front. When warm rain falls through the cold air below the air becomes saturated with moisture forming fog. Frontal Fog can be very dense and hang around for a long period of time. This type is most common with warm fronts but can be found with other fronts.


Steam Fog

Forms when cold dry air moves over warm water. When the water evaporates and rises, it resembles smoke. Common over water during the coldest times of the year. Steam fog can create Low-level turbulence and icing are common.



Ice Fog

Ice fog is formed when the weather is below freezing and water vapor forms directly into ice crystals. Mostly found in colder or arctic regions where temperatures are -25⁰F or colder but can occur in middle latitudes during winter months.



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