(The gray areas are states that haven't voted yet. Last night, West Virginia filled in nearly of its counties with purple, and Kentucky is expected to do likewise next week.)
The working theory here, of course, isn't that Appalachians love Hillary so much, but that Appalachians are uniquely uncomfortable voting for a black guy. Josh Marshall chalks this up to history: "Each of these regions was fiercely anti-Slavery. And most ended up raising regiments that fought in the Union Army. But they were as anti-slave as they were anti-slavery, both of which they viewed as the linchpins of the aristocratic and inegalitarian society they loathed."
This stuff is way, way outside my wheelhouse, so there's nothing much I can add. But the concentration of those purple dots is really striking. It's not clear if this really means much for the general election, but it might. Feel free to speculate in comments.