Occurrence
The aircraft departed at about 0835. At 0953, the pilot contacted Flight Watch and was advised of a convective SIGMET indicating embedded thunderstorms. At 1001, the pilot requested and was cleared to flight level 190. This was the last radio contact with the aircraft. In flight, separation of the wings, vertical stabilizer, and horizontal stabilizer occurred.
Weather Environment
The aircraft penetrated a dense area of thunderstorms with activity rated up to intense (level 5). It probably encountered severe turbulence. Additionally, there would probably have been moderate to severe icing in rain shafts within the thunderstorms at the aircraft's flight altitude.
Weather Briefing
Before departure, a company pilot received two weather briefings from the San Antonio Flight Service Station, one at about 1700 the day before the accident and another on the day of the accident. After each briefing, the company pilot briefed the accident pilot. The 0817 weather briefing was inadequate because the area forecast, which warned of thunderstorm activity en route, was not utilized.