outdoor growing in pacific northwest: greenhouse?

anybody have any ecperience with greenhouse growing? i'm thinking it could work in a wet NW climate

I haven't brought a cannabis crop through harvest in a greenhouse but have worked in them before, growing other crops. Humidity and the diseases that follow it are the main problem. You will want a way to exhaust all air and moisture when the outdoor weather is fair, and then be able to protect your crop against heavy rain when it's not.
You may have to install sulfur burners to keep rot down, but again, I'm not an expert so if I were you, I'd head over to a larger site (ICMag) that has a greenhouse-specific forum and look at the logs of people who are growing in your area.

You shouldn't need a greenhouse. Folks here in Oregon grow outdoors all the time.
In fact, as stinky said, greenhouses can prevent good airflow.
Most folks here just use clear plastic tarps on poles to create an open sided rain cover.

I live in Seattle, and I intend to do a little outdoor growing this year. I'm in the middle of a move right now (suuuuucks), but when I'm done, I'm gonna start scouting for places to plant.

I suggest indicas, myself. Most don't need more than about 4 - 4 1/2 month grow period. And on the west side of the Cascades, rain provides most of the watering, so you won't get busted making a lot of return trips, and the first frost doesn't hit until late October/early November, because we're on the coast.

As long as you're not doing any crazy-ass large scale grows (I don't plan on growing more than 2 females), you should be fine just growing in the ground somewhere.