My guess is that it is a sargent cherry that has escaped cultivation.
http://www.shuttermoments.ca/articles/sakura/cherryguide.htm
Sargent Cherry -- Prunus 'sargentii'
One of the tallest flowering cherries, growing as high as 24 meters, it produces delicate light pink, single 5-petal flowers up to 4cm wide with deeper pink stamens and bronze-red foliage each spring. The bark is a shining polished brown.
The sargentii is one of the few that will not stand pollution.
Can grow to 3.0 - 5.0 meters wide at maturity.
Prunus sargentii 'Rancho' is an upright, vase-shaped tree sometimes described as being columnar. This habit is the shape of the younger tree, but broadens somewhat as the tree ages. The coppery bronze leaves open just as the flowers begin to fade.
In the late 1800s Professor Sargent of the Arnold Arboretum, among others, collected seeds from the mountain slopes of Japan. The Japanese name for this rather large deciduous tree means "great mountain cherry."