Thom Browne’s forecast for spring doesn’t just call for rain, as implied by the umbrellas toted by his models, but also a flood of plaids. Not just any plaids. These were plaids so bright, so pastel, so surreal, so layered, so clashing, so foppish that they’d make Dorian Gray blush. He put them on everything from shrunken coats and shirts to preppy clamdiggers and knee socks, and the umbrellas. Sea creatures appeared as a lobster print and a friendly whale—as stylized as Twitter’s fail whale, and just as recurring…