Definition
A map-based display of weather radar information from the NEXRAD (Next Generation Radar) network, showing precipitation intensity and coverage as colored areas overlaid on a moving map in the cockpit, typically delivered via satellite or ADS-B datalink.
Plain English
A picture of where it's raining or storming, drawn on the cockpit map in colors that show how heavy the precipitation is. The image comes from a network of ground-based weather radars and is sent to the aircraft through a datalink.
Context Anchor
Seen on a multi-function display when viewing in-flight weather information.
Derivation
Graphical means shown as a picture rather than text. NEXRAD stands for Next Generation Radar, the U.S. national network of Doppler weather radars run by the National Weather Service. So 'graphical NEXRAD data' is simply the radar network's output presented visually on a map.
Why Pilots Care
It provides pilots with a real-time view of convective weather along their route, allowing them to avoid thunderstorms and areas of heavy precipitation.
Analogy
It is like looking at a traffic map that was updated a few minutes ago. It is useful for seeing the overall problem areas, but it may not show exactly where every car is right now.
Intuition Check
Do not assume graphical NEXRAD data is a live radar view from your airplane. It is a delayed weather picture sent to the aircraft from ground radar information.
Example Sentence 1
Before crossing the front, the pilot checked the graphical NEXRAD data on the MFD and chose a route through a gap between two cells.
Example Sentence 2
Before takeoff the instructor showed the student how to interpret the latest graphical NEXRAD data for the planned cross-country route.