I'm not certain and just guessing on this one - going to say Washington Hawthorn or a similar wild Hawthorn species. When those blooms open up in a few days it will be very apparent whether or not I'm right. Get a good picture of them when they open on up.
& I look different from Bill, plants are like people, they differ a bit in the wild. tag it with some marking tape, and check it in a few weeks, should have grape sized fruit with veins visible