This is true that each aircraft has a max speed in turbulent air but I have never heard of slowing down due to air temperature. If the updrafts were as strong as they are suggesting then it doesnt matter how fast they were going because their is now way an airframe can withstand that kind of load. Its also possible for the engines to flameout in severe turbulence.
Whether you've heard of it or not, this is what's happening with automated flights now.
Actually the updrafts and even the storm conditions are very debatable, might not have been that bad actually.
The problem seems to be that the sensors told the plane to fly too fast for those conditions, thereby tearing the plane apart. At 35000 feet going over 500 mph the plane will in fact vanish as far as radar, as it quickly comes apart.
