I'm investigating the feasibility of a world where there are taiga forests located far enough north to experience a significant polar night, say, no civil twilight for at least a few months. Inside the polar circle, at the latitude of Ny-Alesund in Svalbard or higher. The planet would be the same as earth in size, rotation, axis, and so on. For landmasses, I'm imagining something similar to the coast of Alaska or British Columbia, but mirrored to fit the prevailing polar easterlies: a mountainous coastline facing an eastern sea. If I can get a temperate rainforest going in addition to taiga, I'd be thrilled, as long as cloud cover doesn't keep the inhabitants from being able to see the stars and moon during the long night.
I know that a forest once existed in West Antarctica, but I don't have access to details regarding the climate, weather, flora, and fauna. I believe it was estimated to have existed in the Late Cretaceous, and if I understand correctly, West Antarctica would not have been within the polar circle at that time. I'm not terribly interested in what the rest of this world looks like, so I'm willing to wave my hand and say that this planet meets whatever global climate conditions are necessary to make a polar forest possible, so long as that doesn't make the world too alien or uninhabitable. I'd like the plants, animals, and ecosystems to be similar to the ones we know in the subarctic today, just farther north than we can get them in our world.
What I'm interested in knowing is what would the weather be like in such a forest, and how would seasons be affected by a multi-month night in winter and a multi-month day in summer? How cold could the nights get? How hot could the summers get? Is heavy precipitation possible, and if so, could you still have clear night skies in winter? Could there be thunderstorms? Or would the polar easterlies limit precipitation too much, even in a coastal area?
I have a basic understanding of atmospheric circulation as it pertains to worldbuilding, but I've been out of the game for a while and am not confident in my ability to project high-latitude weather patterns. I'd love any feedback that could either help me make my polar forest plausible or convince me to give it up and move on to a more feasible idea.