What does "PROB" indicate in a TAF?

In Terminal Aerodrome Forecasts (TAF), "PROB" is used to indicate the probability of a significant weather phenomenon occurring within a specified time frame. This coding provides forecasters the ability to communicate the likelihood of events such as thunderstorms, heavy precipitation, or other significant weather that may impact aviation operations. For instance, a forecast might state "PROB30" which translates to a 30% chance of the specified weather occurring during that forecast period. This way, pilots and flight operations can prepare appropriately for potentially hazardous weather conditions.

The focus of "PROB" is specifically on the likelihood of important weather events rather than complete weather changes, flight delays, or visibility issues. Therefore, it is directly connected to assessing risks associated with flight safety and operational planning.