What does "PROB30" in a TAF indicate?

The term "PROB30" in a Terminal Aerodrome Forecast (TAF) signifies a 30% chance of specific weather conditions occurring within a designated time period. This notation is used to convey uncertainty regarding particular weather events that might be expected at the airport. Weather forecasts often include probabilities to indicate the level of confidence in potential changes or events, and "PROB30" clearly reflects a specific 30% probability, allowing pilots and meteorologists to prepare accordingly.

In TAFs, this type of probability helps users understand that while there is a chance for the indicated weather phenomenon—such as storms, precipitation, or other significant conditions—there is also a 70% chance that these conditions may not occur. This allows for more informed decision-making in relation to flight planning and operations.