Definition
Forecast charts that depict expected significant weather conditions — including areas of IFR and marginal VFR, turbulence, freezing levels, and other hazards — for a future time period. They are issued in low-level (surface to 24,000 feet) and high-level (25,000 to 60,000 feet) versions, and show forecast conditions valid at a specific time, typically 12 and 24 hours ahead.
Plain English
Weather maps that show what the weather is expected to look like at a future time, highlighting the conditions that matter most to pilots — like low ceilings, bumpy air, icing, and storms.
Context Anchor
Seen during preflight weather planning, especially when looking at broad weather patterns before choosing a route or deciding whether to delay a flight.
Derivation
‘Prognostic’ comes from the Greek prognōstikos, meaning ‘foreknowing’ or ‘predicting.’ In aviation, a prognostic chart is a forecast chart — it shows what is predicted, not what is currently observed.
Why Pilots Care
They allow pilots to anticipate and avoid hazardous weather during route planning, directly supporting safer flight decisions.
Intuition Check
Do not read “significant” as meaning only extreme or dangerous weather. Here it means selected weather important enough to affect flight planning. Do not read “prognostic” as a current observation. It means forecast for a stated future time.
Example Sentence 1
During preflight planning, the pilot reviewed the low-level significant weather prognostic chart and noted an area of forecast IFR conditions along the route.
Example Sentence 2
Reviewing the Significant Weather Prognostic Charts showed clear conditions were forecast for the entire route over the next twelve hours.