On February 19, 2002, about 1830 central standard time, a Boeing 737-724, N24736, operated by Continental Airlines, Inc., as flight 1558, encountered turbulence near Beaumont, Texas. One flight attendant was seriously injured. There were no injuries to the 2 certificated airline transport pilots, 2 other flight attendants, or 70 passengers. The airplane was not damaged. Instrument meteorological conditions prevailed at the time of occurrence, for the flight that departed George Bush Intercontinental Airport (IAH), Houston, Texas, destined for Ronald Regan Washington National Airport (DCA), Washington, DC. Flight 1558 was being operated on a instrument flight rules (IFR) flight plan, and conducted under 14 CFR Part 121. The captain stated: "...The briefing [to the flight attendants] was standard...The takeoff and climb out were uneventful. While being vectored by ATC, we climbed to 15,000 ft. ATC then cleared us to BPT (Beaumont). I cannot recall how far from BPT the incident occurred. Radar was showing no significant weather in front of us. Still at 15,000 feet, I was flying in and out of thin stratus clouds. I broke out to find a cumulus cloud in front of the AC. I immediately started a right turn, but it was too close and the AC went through the top of the cloud. At this point we encountered the turbulence...." The first officer stated: "...The weather was windy with multiple cloud layers and no defined ceiling; but for the most part was overcast. The climb-out was bumpy with continuous chop, as we popped in and out of the cloud layers. The injured flight attendant stated: "...Takeoff was normal as we left Houston. After getting the recycle seat belt signal...I started with my aft galley position. I pulled out the beverage cart and parked it on aircraft right in the galley and set the brake. I turned and faced the front of the aircraft (I was going to go into the lave to get some paper towels for the beverage cart) as I was standing there, the aircraft seemed to suddenly drop out from under my feet and I went up into the air. Then as I was coming back down, the aircraft seemed to snap back up, at which time my left leg hit the floor first, and then I ended up on my tail bone on the floor..." A non-duty status flight attendant assumed the duties of the injured flight attendant. The injured flight attendant told the cockpit crew that he could wait until arrival at Washington to receive medical attention. The captain had briefed the flight crew prior to departure. According to Continental Airlines procedures, the captain will conduct a crew briefing each day or when there was a crew change. The brief should include: "...an introduction of crewmembers, departure, en route and destination weather, appropriate open logbook write-ups and other pertinent information the captain considers necessary for the safe conduct of the flight." There was no specific direction for the flight crew to brief the flight attendants on when they could begin cabin service. When asked, what specific direction Continental Airlines used to indicate when flight attendants could leave their seats to begin cabin service, the Director of Safety Investigations for Continental Airlines, reported there was no specific written direction. However, he added the usual practice was for flight attendants to use the illumination of the sterile cockpit light as an indication to remain seated, and once the sterile cockpit light was extinguished, it was alright to begin cabin service, unless otherwise instructed. According to flight recorder data from Continental Airlines, while at 15,000 feet, and an indicated airspeed of 326 knots, the airplane encountered a peak g load of + 2.575, which decreased to + 0.631, and then eventually returned to 1.0 g. The pitch attitude which had been 1.58 degrees nose up, momentarily increased to 1.76 degrees nose up, the decreased to -1.05 degrees down before stabilizing. According to the weather contained in the flight release for flight 1558, the significant weather portion for eastern Texas included scattered to occasional broken lines of thunderstorms, moving slowly eastward. The 1800 and 1900 NEXRAD radar returns showed areas of precipitation in the Beaumont area. A special weather observation, at 1843, from the Beaumont/Port Arthur Airport, Beaumont, Texas, included winds from 200 degrees at 12 knots, with gusts to 20 knots, visibility 6 statue miles, light rain and mist, a few clouds at 900 feet, broken clouds at 2,900 feet, overcast clouds at 3,700 feet, and the rain began at 31 minutes past the hour.