"Firstly the top of the fog bank/orographic cloud is the boundary between airmasses.
Sometimes it is just a small temperature inversion, but occasionally there is a large shift of temperature and a massive change of wind direction and strength - I've witnessed 160 degrees and 25 knots.
This can lead to a destabilization of the aircraft".
But the obs. have several chunks of low St at various heights: not a typical fog top inversion situation.