What happened
Prior to the flight, the pilot attended a morning outlook briefing that highlighted the presence of scattered rain showers and thunderstorms along the intended path. During the flight, air traffic control (ATC) notified the pilot of an active convective SIGMET affecting the route. While several other aircraft in the area were actively maneuvering to avoid weather, the pilot initially declined an offer from ATC to deviate from the planned course before later agreeing to a change in heading.
During the flight, the aircraft was cruising at 28,000 feet MSL. The pilot subsequently lost the ability to maintain this assigned altitude, resulting in a vertical descent that ended in a terrain impact. No mechanical failures were identified through the examination of the wreckage prior to the crash.
Findings
At the time of the incident, weather radar indicated weak to moderate echoes at the aircraft's cruising altitude. However, much more intense weather echoes were present at approximately 20,000 feet MSL. The ATC controller's NEXRAD display was configured to monitor altitudes above 24,000 feet, meaning the controller did not see the more severe weather activity occurring at the lower altitude.
Discrepancies between the aircraft's onboard radar and the ATC weather radar were noted, as the pilot's equipment may have been displaying more detailed information than the controller's display. It remains undetermined whether the pilot was aware of the intense convective activity at the lower altitude or if the onboard radar was specifically highlighting those stronger echoes.