Black areas - they turned out heavily for Obama and helped him carry VA twice.
Hillary isn’t getting anywhere near the turnout numbers Obama got.
I live in the Richmond area. There are limited ways that you can vote early in Virginia, there has to be a designated reason, such as you are not in town for business, or are out of state on election day for some other valid reason.
The areas that Cook cites are heavily Democrat areas. Petersburg is almost completely AA, and Norfolk and Newport News have heavy African-American populations.
If Hillary cannot reassemble the Obama coalition of high minority and youth turnout, she is vulnerable in Virginia. Southwest Virginia and the Shenandoah Valley will be strong for Trump.