There is a plethora of marine finishes out there that would hold up well to the weather. For a really tough, long lasting fiish, I'd sugest the two part, clear marine epoxy finish. This stuff is used on strip made canoes and kayaks, and is tough as nails. I've used the epoxy marine paint, and it held up on a wood hull for over 10 years with virtually no deterioration.
The clear stuff on this site says it can't be used over a stain, but I'd bet you could use it over an analine dye with no problem, as the stain deposits colored particles on the surface and the dyes actually infuse the wood with color.
http://gregboats.com/pages/finishes.html
Only one thing.....this stuff ain't cheap. I think you may find this in quart sized quantities if you look around a bit.
Al