Definition
A weather chart that depicts forecast conditions — such as fronts, pressure systems, areas of precipitation, turbulence, icing, and cloud coverage — expected at a specified future time. Prognostic charts are produced for various altitudes and forecast periods and are used by pilots during preflight planning to anticipate the weather they will encounter en route.
Plain English
A weather map that shows what the weather is expected to look like at a future time, not what it looks like right now.
Context Anchor
Pilots see prognostic charts during preflight weather planning, especially when checking expected clouds, precipitation, fronts, and pressure systems along a route.
Derivation
From the Greek prognostikos, meaning 'foreknowing' or 'predicting.' The same root appears in 'prognosis' in medicine. In aviation, it signals that the chart is about prediction, not present conditions.
Why Pilots Care
Allows anticipation of changing weather along a planned route so appropriate decisions can be made before departure.
Intuition Check
Do not read a prognostic chart as a current-weather chart. “Prognostic” means it is showing a forecast for a future time.
Example Sentence 1
Before departing on the cross-country, she reviewed the low-level prognostic chart to see where icing was forecast along her route.
Example Sentence 2
Prognostic charts help determine whether a front will cross the route during the flight.