Small snake approx 40cm seen on Round Mountain trail on a sunny day .... ?baby eastern brown or ?baby copperhead or some other species? Unusual for a brown to be at this altitude?
Blurred image and head obscured. You haven't given us much to go on. Could be any of those. If juvenile Brown, did you notice if the head was black with another black band on the nape? If not, then possibly Drysdalia. I don't think it is a Copperhead.
Looks most like and most likely to be Drysdalia coronoides at that altitude*. I can see the head and it lacks the black cap and nape of a juvenile Eastern Brown, but has the characteristic, continuous white upper lip stripe of D. coronoides. *alt. =~1680m