You have probably heard or read about the fatal plane crash at Spa last weekend.
The combination of the geographical location of the airport (SW/NE) and the meteo of the day (SE wind) created turbulent flying conditions at Spa.
InfoMeteo.be wrote an interesting (French) article on the dangers of the föhn effect.
Important to remember: even when the weather looks nice, it is important to consult all meteo carefully and extensively each time. You can’t be informed enough!