In the Seattle area, now is still a great time to repot conifers (
Douglas fir, junipers,
lodgepole pines, mugo pine, p. thunbergii, p. sylvestris, p. nigra, p. strobus, true fir, and spruce). It is also a great time for quince,
zelkova, rose, and certainly more.
With regard to thunbergii and tsuga, though, I've run into problems bare rooting from nursery mix, regardless of timing. Half bare rooting, however, works, be it spring or after the summer solstice. I think this more productive than just slipping into a bigger pot or grow box (loosen roots all around and under; gently wash and comb out one side of the root mass; pot the works surrounded on all sides by a good bonsai substrate; repeat next year to complete the job).
Of course, there is the option of doing noting other than fertilizing which, since
@Maloghurst's tree has relatively little foliage now, is not a bad idea. Good nitrogen nutrition is required for budding; more foliage is more 'horsepower' to recover roots from future work.
Personally, I would do the half bare root, if anybody is asking; but it isn't my tree.