Plain English Meaning
A weather product that shows where volcanic ash from an eruption is expected to travel and spread through the sky over the next several hours, so flights can be routed clear of it.
Full Definition
A computer-generated forecast model produced by the National Weather Service that predicts the movement and dispersion of volcanic ash in the atmosphere following an eruption. The VAFTAD model forecasts ash concentrations at multiple flight levels over time, showing where ash clouds are expected to drift and how they will spread, allowing pilots and dispatchers to plan routes that avoid contaminated airspace.