From the National Weather Service:
Flood Watch National Weather Service Taunton MA 418 PM EDT Mon Sep 18 2017 MAZ022-024-190430- /O.NEW.KBOX.FF.A.0007.170919T2200Z-170920T2200Z/ /00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/ Barnstable MA-Nantucket MA- Including the cities of Chatham, Falmouth, Provincetown, and Nantucket 418 PM EDT Mon Sep 18 2017 ...FLASH FLOOD WATCH IN EFFECT FROM TUESDAY EVENING THROUGH WEDNESDAY AFTERNOON... The National Weather Service in Taunton has issued a * Flash Flood Watch for Barnstable County and Nantucket. * From Tuesday evening through Wednesday afternoon * Jose, currently sitting well south of Nantucket will shift north, then eastward through Wednesday. This will bring bands of heavy rain mainly to Nantucket and Cape Cod as it makes its closest pass late tomorrow into early Wednesday. Continued bands of heavy rain could lead to localized flash flooding, exacerbated by the inability of each high tide cycle to fully drain. As much as 3 to 6 inches of rainfall is expected. PRECAUTIONARY/PREPAREDNESS ACTIONS... A Flash Flood Watch means that conditions may develop that lead to flash flooding. Flash flooding is a very dangerous situation. You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued.