Aviation Weather Issues – Fog – Part 2: Impact of Fog

PT 2 M minute read
Aviation Weather Issues – Fog – Part 2: Impact of Fog

This business aviation blog post continues from our article last week, titled “Aviation Weather Issues – Fog – Part 1: Types of Fog.

Fog conditions have potential to delay a flight or to cause the flight to divert from the planned destination airport. Understanding the impact of this atmospheric condition is important whenever operating to a fog prone area.

The following is an overview of what you need to know:

1. Visibility impact of fog

Fog is the most common visibility limiter in aviation. It has the ability to limit surface visibility to less than 5/8th mile; therefore, the operational impacts of fog can be significant. Fog conditions often reduce aircraft arrival/departure flow rates and can become dense enough to close an airfield. In terms of specific disruption potential, fog has the ability to cause operational delays or to even prevent you from arriving at your destination. When fog is anticipated crews will need to consider airport alternates, or alternate ETPs, and carry additional fuel due to the conditions generated by fog. Fog has potential to rapidly reduce visibility, from visual flight rules (VFR) to instrument flight rules (IFR) within minutes. This rapid reduction in visibility occurs, primarily, with advection types of fog – along coastlines or in upslope conditions. Radiation fog usually occurs more gradually, as temperature lowers over time to the dew point.

2. Common areas for fog

Radiation fog and stratus are common across Europe during long winter nights. Advection fog often affects airfields along coastlines, especially across the U.S. gulf and east coasts, the Canadian Maritimes as well Japan and the Northeast coast of Russia and southern Alaska. Marine layer fog and stratus are often prevalent along the U.S. west coast. Upslope fog, meanwhile, often affects areas along the front range of the Rocky Mountains.

3. Fog is more likely at certain times

Radiation fog is more prevalent during long (winter) nights. Advection fog is most prevalent along coastlines, especially during spring when there are sharp temperature gradients. Delineation between fog types is not always straightforward because, over time, fog formed primarily by radiative processes may be supported by dynamic or advective processes, and vice versa. Time of day also influences occurrence of fog. Radiation fog is generally nocturnal, but advection fog can impact aviation operations any time of day. It’s important for crews to be aware of the particular fog type that may impact their operations.

4. Predicting fog

Fog conditions may be transient, with fog density varying rapidly within a particular airfield. Geography plays a significant role in fog development, making fog density and dissipation difficult to predict. It’s always important that pilots and aviation weather forecasters be aware of geographic makeup of an airfield and local area. Forecasters are usually able to use general synoptic situations to predict fog potential. When it comes to fog’s impact on visibility, however, forecasts can become more challenging.

5. Additional reading: Aviation Weather Issues – Fog Series Index

Note: Links will be updated as articles are published.


There are a number of pre-planning steps that crews should consider whenever fog conditions are anticipated at your destination. If you have any questions regarding fog and its effects on your flight, it’s recommended that you speak to your 3rd-party provider.


If you have any questions about this article, or would like assistance with weather planning, contact me at stevearbogast@univ-wea.com.

Stay tuned for Part 3, which covers more considerations on fog and its effects on business aviation operators.

Got a question for Steve about this article?