The National Weather Service issued a storm warning at 11:38 a.m. Thursday, effective Friday between 7 a.m. and 7 p.m. for Essex, Plymouth, Barnstable and Nantucket counties.

“Large breakers are expected in the surf zone,” the weather service said. “The greatest risk of moderate flooding is along the Plymouth coast, including the north shore of Cape Cod (bay side), from Sandwich to Dennis.”

“Some coastal roads will become impassable at high tide. Flooding of 12 to 24 inches will affect roads on the North Shore from Salem and Marblehead through Gloucester to Newburyport. Heavy surf will cause beach erosion and throw debris onto coastal roads. Many roads near Nantucket Harbor will become impassable at 12 to 24 inches of water, affecting access to ferry terminals. These include Easy Street, South Beach Street, Easton Street, Walsh Street, Willard Street and Straight Wharf. Roads will remain passable. Shallow flooding of less than 12 inches will affect low-lying areas in Provincetown, primarily near the airport and Race Point Road. In Truro, flooding of up to 12 inches will affect low-lying areas near Pamet Harbor and along the Pamet River. Hazardous conditions for swimming and surfing and localized beach erosion,” the weather service explains. “If you must travel, allow extra time as some roads may be closed. Do not drive around barriers or through waters of unknown depth. Take necessary steps to protect property at risk of flooding. Inexperienced swimmers should not enter the water due to dangerous surf conditions.”

Advance Local Weather Alerts is a service from United Robots that uses machine learning to compile the latest data from the National Weather Service.