Western Mountaineering, among the finest down bags made anywhere, this from actually owning and using one and the others, Feathered Friends, original Marmot Mtn. Works, Integral Designs, Fairydown, Caravan, Valandre and some others,US, Canadian and "Yurp" made, has a few models that will meet your specs.
Choose among them according to your size and if you look after one of these, it will last many years. These are made in California and they use the finest materials and care in assembly.
The synthetics, mine are now exclusively Integral, are not as light and will not wear as long. A first class bag is one expenditure in outdoor life that is really worth spending the bux on and is one of life's simple pleasures to use.
We have four of the Kifaru 0 degree slick bags, standard length and width.
They did lose some loft in the first year so I wouldn't rate it at 0 anymore, more like 20 now.
That was my experiance with the 3 I had and why I do not own any of them anymore. I got fed up with freezing my a$$ off after they were used a season. They are great bags if you don't use them very much or can afford to buy a new one every year or two.
Down is the way to go, even in the PNW. If your really worried about them getting wet get one of those 6 oz bivy covers. I would look at Western Mountaineering, Montbell, Zpacks, Feathered Friends, Enlightened equipment just to name a few.
Check out the Marmot Plasma 30. It is 900 fill down, and weighs 1lb 7oz. I have no experience with his exact bag, but am pleased with my other Marmot products, including sleeping bags. Good luck, and happy shopping.
If you want a 30deg bag then consider a WM Megalite. Good shoulder girth and it can easily go to 20deg if you wear good base-layers and have a good pad in a tent.
Wait for a sale, I bought my Megalite new for around $250 a couple years ago. (also picked up a used once WM Badger for about $350)
Hard to beat down for compression, warmth and longevity. If you are worried about wetness, just get a good DWR coating, or use a bivy when conditions merit it, use either a VB or insulated bivy for long term use where temperatures are below freezing,. Another option is the dry down. I posted details a while back on insulation and wetness and synthetics loose some, but they loose a lot of loft over the years as well, The main advantage with synthetics is they don't clump and thus dry faster. They are less expensive as well. However for pure performance vs weight down is the clear winner.
