As I left work a huge wall of dark clouds were coming from the North, and when they were overhead the clouds in the north were incredibly black, clouds as dark as I've ever seen. Quarter of an hour later the downdraught came, and the lightning began. Luckily it didn't rain till just as I got home: by then the lightning was right overhead.

Some sun
-> 8 Sc
1200 SHOWER
1600 6
Huge Cu seen approaching from N
1700 8 very dark
⚡ THUNDERSTORM