TRUTH IN SYMBOLS...

Any graduating meteorology student will tell you that one of the hardest forecast parameters is the "sky condition". Forecasting the difference between "partly cloudy" or "mostly cloudy" can be rather tricky, especially during a day when the weather is active or rapidly changing. And remember- like most topics in meteorology, sky conditions are defined by a very specific set of guidelines.

Officially, a "partly cloudy" sky condition is defined by a concentration of opaque clouds covering between 3/8 and 5/8 of the sky. This seems to be the most commonly reported sky condition in the coastal Carolinas, especially during the summer months. "Partly sunny" is used interchangeably for the same conditions.

A "mostly cloudy" day is defined by 6/8 to 7/8 cloud cover. Conversely, a mostly sunny day is defined by 1/8 to 2/8 cloud cover. Obviously, a "clear" day is defined (more or less) by total sunshine, and a cloudy day is defined by total cloud cover.

Naturally, our sky conditions are subject to rapid changes on active weather days. For example, cold fronts may bring a sudden chance of rain to an otherwise dry afternoon. Sometimes, a meteorologist may forecast "variably cloudy" skies if rapidly changing conditions are anticipated.

Like all things in meteorology, cloud forecasting is an inexact science. Sometimes, we simply have to take our best guess.