Added on: July 12, 2011
Radiation fog is the most common form of fog. While it usually develops in the overnight hours, a widespread radiation fog event can occur anytime of the year anywhere in the U.S. Radiation fog can easily bring the ground visibility to below one-half of a statute mile leaving most pilots grounded. The basic requirements for radiation fog are well-known. Advisory Circular 00-6A (Aviation Weather) says that, “Conditions favorable for radiation fog are clear sky, little or no wind, and small temperature-dew point spread (high relative humidity).” While this explanation is technically correct, it is very much incomplete and ignores other factors that occur in the potential fog layer. In this workshop, we’ll use the Skew-T log (p) diagram to understand what might wreck a perfectly good radiation fog event even when those favorable conditions exist.