Less than a Week to Go

I wonder what it will be like as the sun is gradually eclipsed by the moon and then enters the phase of totality. Will it get gradually dim, but suddenly a great dark shadow will descend upon us? Will the total darkness come quickly? All of the continental U.S. will be able to see the eclipse, but only a narrow band about 70 miles wide from Oregon to South Carolina will be in the path of totality.