Looking at the ADS-B track, the groundspeed during climbout was very slow (low 70s dipping to the low 60s) with strong (mostly) crosswinds predicted aloft. There was an AIRMET for icing and turbulence. The bulk of the storm had passed, but the aircraft flew right into a radar-indicated, fairly light precip cell near Oak Ridge and departed controlled flight just a few moments later. It would have been about -6°C at that altitude.
If you look closely at the ADS-B, at about the time the aircraft entered the cell, it resumed a climb and slowed down even more, then suddenly turned left, gained a bit of speed and descended (looks a lot like a stall), then climbed again for a moment until what may have been a secondary stall, followed by a very rapid descending right spiral with ground speeds reaching at least 250 knots. The ADS-B track ends at about 6,700’ MSL.
