How would a 45% chance of thunderstorms and heavy rain be reported in a TAF for a specific timeframe?

The correct answer involves the use of the "PROB" prefix, which is specifically designated for indicating the probability of certain weather phenomena occurring within a forecast period in a Terminal Aerodrome Forecast (TAF). In this case, a 45% chance of thunderstorms and heavy rain is reported as "PROB40", meaning there is a 40-49% likelihood of the event occurring during the specified timeframe of 1402 to 1405 UTC.

This is important in TAFs as it accurately conveys uncertainty to pilots and air traffic control, allowing for better planning and safety measures. The inclusion of "+TSRA" further specifies that heavy thunderstorms and rain are expected if the probability is realized.

Other choices do not properly reflect the probability of occurrence. Some options imply specific occurrences without mentioning the probability, which does not provide the necessary context of uncertainty that is crucial in aviation forecasts.