In case you are wondering, I just came from the Copley Market and a few of the vendors did show up, despite the storm. Missing are Atlas, Stillman's (in case you were going for meat) Hamilton, Keown and a few more.
Siena, Old Friends, Iggy's, McArthur's, Dick's, and Crystal Brook were all there with plenty of stock.
Siena had cookbook author Amelia Saltsman signing her Santa Monica Farmers' Market Cookbook while I was there. But, they are going to move her to Sofra in Cambridge (where it is dry) for the rest of the afternoon.
She's great, loved chatting about food with her.