Creating a sticky nav css and jquery

[basemjok]

I am working on a sticky nav for a website currently, and I am running into a few problems, when the nav becomes \[code\]position:fixed\[/code\] it seems to jump and it looks "clunky", here is a fiddle of what I am trying to do, http://jsfiddle.net/DKtLR/Ideally the outcome would be the user scrolls and the nav is not in a fixed position until it is scrolled out of the viewport it then becomes fixed and and slides back into view.