On May 25, 2000, about 1045 eastern daylight time, a Piper PA-28-161, N47561, registered to the Chapel Hill Flying Club, Inc., operating as a Title 14 CFR Part 91 instructional flight, crashed 1/2 mile short of the runway at the Horace Williams Airport, (KIGX) Chapel Hill, North Carolina. Visual meteorological conditions prevailed and no flight plan was filed. The CFI and a student pilot sustained minor injuries and the airplane was destroyed by postcrash fire. The flight originated from the Raleigh-Durham International Airport, (KRDU) about 30 minutes before the accident. According to the CFI, the flight was the second leg of a two-leg flight from KIGX to KRDU back to KIGX. While on final approach to KIGX's runway 27, at about 300 to 400 feet agl, and 1/4 to 1/2 mile from the runway threshold, they encountered winds that caused a severe left roll of about 60 to 90 degrees. The CFI applied sufficient control correction to level the airplane, but it's direction of flight continued in a left turn and it continued to descend until collision with a stand of trees and the terrain. Examination of the wreckage path revealed the airplane's initial collision with the ground was on a heading of about 180 degrees. The CFI further stated that he used the Raleigh-Durham ATIS and the KIGX automated surface observing system, (ASOS) for weather information prior to their encounter with the adverse winds. According to a sequence of weather radar images from the Raleigh-Durham WSR-88D Doppler Radar facility, for the time frame, 1004 to 1102 on May 25, 2000, the line of thunderstorms can be seen west of the KIGX airport, moving to the east. At the time of the accident, VIP level 5 radar echoes, (intense precipitation) can be seen abeam and adjacent to the KIGX airport. See the Weather Radar Images report, an attachment to this report. Another flight instructor and his student, waiting to fly at 0930, from Chapel Hill, were given a Raleigh-Durham FSS weather brief stating no significant weather could be expected until the mid to later afternoon; however, the FSS did call back to the FBO a few minutes later advising that a line of thunderstorms was fast approaching from the west, and to reconsider flying at that time. Subsequent local TV news accounts of the results of the weather system that transited the area at the time of N47561's approach for landing at KIGX stated that numerous trees and power lines were down as a result of winds that reached 50 to 60 miles an hour. According to an FAA inspector, the CFI and student obtained their preflight weather brief from the Chapel Hill flight school computer using the CIRRUS WX software, supplemented by reviewing a WSI weather terminal. The forecast indicated that storms and severe weather may occur later in the day. According to an automated weather observation taken for the Horace Williams Airport 8 minutes before the accident, surface winds were from 310 degrees at 21 knots, gusting to 39 knots. Peak winds were from 300 degrees at 39 knots. Lightning observed in the distance from west of the airport through northeast. Thunderstorm activity began at 1031, and rain began at 1036. According to the Airman's Information Manual, Chapter 7, section 7-1-26, "Thunderstorm Flying", article (1), the following warning is stated: "Don't land or takeoff in the face of an approaching thunderstorm. A sudden gust front of low level turbulence could cause loss of control".