Plain English Meaning
It's the weather picture you build before you fly — what the weather is doing now and what it's expected to do, everywhere you plan to go.
Full Definition
The collection of weather data a pilot reviews before a flight to evaluate conditions along the planned route, at the destination, and at alternates. It typically includes current observations, forecasts, winds and temperatures aloft, hazardous weather advisories (AIRMETs, SIGMETs, convective SIGMETs), PIREPs, NOTAMs related to weather, and any relevant to , , and airports.