How many seconds did it take for the weather to go from CAVOK to completely ****ty?
That's like asking how long is a piece of string. I don't know, I wasn't flying it.
Weather deterioration can happen very quickly in hilly or mountainous terrain with updraughts, or in this case, downdraughts, dragging the cloud down the hill and into the narrow valley they were flying along - it happens and isn't forecastable in such localised conditions.
Some need to get over the idea that the video was as a result of a pre-planned scenario.
Route planned, weather checked, launch on navex, encounter rapid localised weather deterioration en route, go down, slow down, turn round when safe to do so, escape bad weather and continue navex. What more do some of you want?
I know military low flying isn't something everyone here has done but surely everyone has had an aviation plan turn out differently to the way it was intended and had to divert/replan/land/turn round - exactly like this crew did. Not rocket science and no-one would have planned to end up in those conditions but sometimes it just happens and you have to deal with it - calmly, professionally and as safely as possible ie exactly what this crew did. Just because they ended up on someone's dashcam doesn't make them naughty, unsafe or unprofessional.
Plenty here want to criticise but no-one has said what they would do in the same situation - so sh*t or get off the pot. (we have already discounted reversion to IFR for fuel and terrain reasons) Anyone fancy going IMC in a steep narrow valley with cumulo-granitus on all sides???