This umbral shadow will be rather small, so as far as eclipses go, totality won't be particularly under clear skies – if you're standing at the centerline, it should still be quite bright around the entire horizon. As a rule, the eclipsed sun's corona is roughly as bright as the full moon. Overcast and a full moon would be navigable if your eyes are well adjusted to the dark, but with the light-switch action of totality, yeah... would be difficult to see.