Thanks, Howard. I left a little bit out, actually. CAVOK means "cloud
AND visibility OK" which means vis greater than 10 km as well as no cloud below
5000 ft. In practice it often means no cloud at all - one just has to guess.
If the vis is below 10 km and the sky clear then the term SKC is used.
I don't think raw METARs (or SYNOPs) should be posted. I've done it
myself in the past but it's a bit offhand, even if there's a link to an
explanatory page.

Tudor Hughes.