Relying solely on NextGen weather radar (Nexrad) for up-to-the-minute weather information could prove risky according to a June 20, 2012 National Transportation Safety Board safety alert.  According to the alert, “weather conditions depicted on the mosaic image will always be older than the age indicated on the display.”  The NTSB cautions that “in extreme latency and mosaic-creation scenarios, the actual age of the oldest Nexrad data in the mosaic can exceed the age indication in the cockpit by 15 to 20 minutes.”

FAR 91.103 (42 U.S.C. 91.103) requires that for flights under IFR or a flight not in the vicinity of an airport, each pilot in command shall become familiar with “weather reports and forecasts.”  Reliance on in-cockpit Nexrad images alone might not satisfy this legal requirement, and is surely risky if operating a high-performance aircraft in and around significant weather systems.  As the NTSB alert cautions, “get your preflight weather briefing! Having in-cockpit weather capabilities does not circumvent the need for a complete weather briefing before takeoff.”