Definition
A category of significant weather forecast covering the airspace from 25,000 feet to 60,000 feet (FL250 to FL600). It depicts hazards relevant to high-altitude flight, including thunderstorms, turbulence, icing, jet streams, tropopause heights, and volcanic activity, and is presented on a dedicated High-Level Significant Weather Prognostic Chart.
Plain English
A weather forecast made specifically for the part of the sky used by jets and other high-flying aircraft, showing the hazards expected up there.
Context Anchor
Seen in weather chart discussions, especially when reading significant weather prognostic charts before a high-altitude flight.
Why Pilots Care
Allows pilots to anticipate and avoid turbulence, icing, and other hazards along their route before departure.
Grounding Statement
It is the high-altitude weather picture for conditions that matter to flight safety and planning.
Intuition Check
High-level does not mean “more important” here; it means weather at high altitudes. Significant does not mean merely interesting; it means important enough to affect flight operations.
Example Sentence 1
Before dispatching the jet to FL380, the crew reviewed the high-level significant weather chart for forecast turbulence along the route.
Example Sentence 2
Strong jet stream winds appeared on the high-level significant weather forecast, prompting a route change.