I have just been asked how snippets (result descriptions) in the Google SERP work, so here is the answer. Google tries to decide what text is best to display as a snippet based on the text of the search phrase.

1) The site:websitename.com view defaults the to the meta description becuase it has nothing else to go on.

However when we mimic a normal search it's more variable.

2) First when the search string is matched in the description, that's what you get:

"US west coast hit by storms flights"
http://tinyurl.com/qcr3w

3) When it is partially matched in the description and body you get a mix of both seperated by three full stops ... :

"barrage of storms flights"
http://tinyurl.com/qel9u

4) When it is matched only in the body copy, that's where the description comes from:

"barrage of storms over the past few days"
http://tinyurl.com/qujst

Overall I think it's a pretty good system.