This might be an exciting find for Seattle. A friend travelling with me happened to need to visit the people living in this house at 6552 36th Ave NE, where there was this cherry that still had a lot of white blossoms. They're on long stems like Shogetsu and Shirofugen, the two late bloomers that I know. Unlike Shogetsu and Shirofugen though, which have hardly any stamens, these double white blossoms have lots of stamens. In the first photo, you can see several phylloid structures that are about the size of the leaves, but they have phylloid-pattern veining that's very different from the leaf veining. I've only seen this on Shirfugens. But the leaves are quite small, much smaller than Shogetsu or Shirofugen, with very different leaf margins. And the stems look hairier. The people living in the house say that it also blooms in December. I have a magazine photo of 'Nido-zakura', which means "blooming two times", which shows white blossoms with stamens on long stems. Our scout Mariko says the Nido-zakura first bloom is single and the next one double. I didn't ask her if the first bloom is in the winter. I could ask the residents to pay attention and take photos next year.