Need advice for outdoor finish (on signs)

I've just routed some pine for trail markers, I'd like to stain them a darker brown and paint in the lettering with yellow. Much like a state park sign would look. What would be a good finish for outdoors that will help them to last? I live in the north east, so we'll be getting bitter cold, snow, rain, some sun on occasion.....

Any advice would be appreciated, I don't do much outdoor work. I know in the photo that they are painted, (maybe I'd be better off painting them(?), but I'd like to stain them.