Plain English Meaning
A forecast that tells pilots what the wind and air temperature are expected to be at different altitudes above various points across the country, at specific times.
Full Definition
A forecast product that predicts wind direction, wind speed, and air temperature at specified altitudes above selected reporting locations, valid for set times during the forecast period. Winds are given in true direction (not magnetic) and in knots; temperatures are given in degrees Celsius. The forecast is issued for standard altitudes such as 3,000, 6,000, 9,000, 12,000, 18,000, 24,000, 30,000, 34,000, and 39,000 feet, with temperatures omitted for the level closest to the station and for altitudes within 2,500 feet of station elevation.