The adjective that might best describe the snow, based on the connotations of the words in the final stanza ("It ruffles wrists of posts, / As ankles of a queen, -- / Then stills its artisans like ghosts, / Denying they have been"), is delicate.
The imagery of ruffling and comparing the snow to the ankles of a queen suggests a sense of grace and gentleness, which aligns with the connotation of "delicate."