Cherokee Princess, a flowering dogwood cultivar.

Said to be the industry standard for white blooms. Ours are more cream than white. We have many wild dogwoods, but none are blooming yet. This one came from a nursery a few years ago, replacing the gorgeous weeping cherry felled on this spot by the snow. (But a week later they seemed white enough.  Below I added a few more pictures taken Saturday 16 April, just as the rain began.)

Wikipedia reference: Cornus florida