Pulkovo 612 tried to intentionally exceed their service ceiling to go over weather. Stall-spin to the ground.
Yes, that certainly was a major contributor, however, encountering the 16,000 fpm updraft in the thunderstorm is what got them in the end. They were flying too close to the edge, otherwise, they might have gotten away with it.
In any event, it was a loss in a severe thunderstorm, which is what the OP was asking for.