what I find unreal is the temps to go from -46 to -18c in fell swoop
It is not as unreal as it sounds. Last year on an A340, while flying through what was probably the remains of previous days CBs, we had some spectacular St. Elmos fire. The whole airframe was glowing, lightning coming out of the radom etc. Also the TAT increased dramatically, from -30 to almost 0° within approx. 5 minutes. I was sure this was caused by the electric discharges heating up the TAT probe, but nevertheless the upper and lower limits on the the speedtape came uncomfortably close.
As we did not want to find out what would happen if the apparent temperature pushed as out of the envelope (overspeed and stall protections at the same time?), we were about to start an immediate descent when we suddenly left the area and the TAT fell back to -30° within seconds.
There was nothing on the wx-radar and the turbulences were only light to moderate.
I would not completely rule out something like this happened to AF447, but I think it is very unlikely and other theories seem more plausible.
Just my 2 cents
Thomas