So far, forecasts show Matthew will miss Florida, although it's likely to clip Jamaica, cross eastern Cuba, wreck the Bahamas, and march up the eastern seaboard, perhaps going into New England (Connecticut, Rhode Island, Massachusetts). It's possible it might trigger a huge rain event extending from Ohio to Nova Scotia, even in areas very far away from the storm itself.
According to the models, the storm should start executing a 90 degree turn (which storms rarely do) right now. The storm is very far south, though. It's almost scraping the coast of Venezuela, where easterly winds are usually stronger and southerly winds are usually weaker. The longer it takes to make this turn, the more likely a direct hit on Jamaica becomes, as well as a direct hit on Florida. It's a real test in the reliability of the models.
So, we'll see.