Replying to the post saying "An updraft will not in itself reduce airspeed. Updrafts add energy, not reduce it. The first reaction by the autopilot (or PF) would be to try to maintain altitude by putting forward pressure on the stick. This will in effect increase the speed because of the updraft wind vector":
There is something simple that can be calculated for the angle of attack instantaneous change due to hitting a sudden upcurrent such as in an active Cb. If the current airspeed is say 500kt and the aircraft is flying horizontally, then if a 50kt updraft is suddenly encountered then there will be an instantaneous change of AoA by an angle equal to arctan(50/500) which is about 5.7 degrees. It the aircraft was flying within a couple of degrees of the stalling angle of attack and encounters a transient strong upcurrent then there is a good chance of reaching the stalling AoA very rapidly. What the aircraft control response to that is will depend on how the fly-by-wire system has been coded to react, or how the pilot will respond if he/she recognises what has happened is not clear despite the various postulated scenarios already discussed. Equally there will be a reverse change to the AoA on exit from the same updraft so the net result will depend on how long the aircraft flies within updraft conditions and the velocity of the air within it. Is that not basic physics?