Definition
A forecast chart depicting the expected significant weather conditions — such as turbulence, icing, freezing levels, IFR and MVFR areas, thunderstorms, and frontal positions — for a specified valid time. Issued in low-level (surface to FL240) and high-level (FL250 to FL630) versions, these charts give pilots a graphical preview of hazardous weather along a planned route.
Plain English
A forecast map showing where bad or hazardous weather is expected at a specific future time, so pilots can see at a glance what to plan around.
Context Anchor
Seen during preflight weather planning when a pilot is checking forecast weather along a route.
Derivation
Prognostic comes from the Greek prognostikos, meaning 'foreknowing' or 'predicting in advance.' In aviation it simply means a forecast — a picture of what the weather is expected to do.
Why Pilots Care
Allows pilots to identify and avoid areas of hazardous weather before departure, directly affecting route selection and safety.
Grounding Statement
You are looking at a future picture of important weather, not a current weather report.
Intuition Check
“Significant” does not mean dramatic or unusual here; it means important enough to affect flight planning or safety. “Prognostic” means forecast, not observed right now.
Example Sentence 1
Before the cross-country flight, she pulled up the low-level significant weather prognostic to check for forecast icing along the route.
Example Sentence 2
Reviewing the significant weather prognostic revealed a line of thunderstorms expected along the planned route.