Snow

For those with a lexical deficiency (and have an aversion to dictionaries - apologies to anyone else!) here's a definition of "accretion" - "an increase by natural growth or by gradual external addition; growth in size or extent."  Sounds a bit like what happens when snow falls!

For those lacking in poetic theory - a poem should "suggest" - not specify or overtly dictate (having said that, this piece pretty much spells out the suggestion by an explicit simile !)