It is also quite feasible for a buildup to go "electrical" quite suddenly. A friend of mine was flying along (in IMC
) and reportedly within a few seconds the whole scope lit up like a xmas tree - all around him. A few seconds later he was in severe turbulence.
This kind of thing -- the whole scope suddenly flaring up -- can happen, but it shouldn't be totally unexpected. That kind of phenomenon arises out of a precondition that should be well known to the briefed pilot.