That is weird since my country is on the same latitude as Alaska and we don´t have anything relating to rain forest. 
The southeastern Alaskan coast benefits from the aptly-named Alaskan Current, a warm, low-saline current that helps to moderate the temperatures there. It's also shielded by a mountain range ten to twenty miles inland; the narrow coastal band is warm and rainy, but the weather on the other side of the mountains is decidedly different. (The difference is easily noticeable over the course of an hour or so drive inland from, say, Skagway; it's super humid when you start out, but once you cross the Canadian border things start to dry out.)
Characterizing the Alaskan coast as "rain forest" might lead to some false impressions, though. Technically, a rain forest is any forested area with 250-450 cm of annual rainfall. Although the Alaskan coast is relatively warm and very wet, most of the precipitation there comes in fall and winter. Temperatures in Juneau often hover juuuuuust above the freezing point and result in lots of cold rain.
The actual rain forest areas are concentrated in the Tongass National Forest, along the panhandle (the Juneau-Skagway-Sitka area) and in the Chugach National Forest (the Kenai Peninsula, around Anchorage). A little more than half of the national forests are actually covered in trees, mostly conifers (especially spruce). Much of the remainder is rocky areas or glaciers, such as the Mendenhall Glacier just outside of Juneau:

Although the Alaskan temperate rainforests are, indeed, rainforests, they don't bear much resemblance to the Arbor Wilds. The Wilder trees are generally the wrong kind, and the forest doesn't benefit from a warm coastal current like the Pacific Northwest does. It's also probably on the wrong side of the Frostbacks to benefit from relief rain; the warm, wet air ought to be coming in from the ocean and dumping its precipitation in western Ferelden, which would put eastern Orlais into a rain shadow.
So yeah: the simplest explanation is probably magic.