Maps of Hurricane Lee in New England: Flooding, wind speeds, rainfall

Post-Tropical Cyclone Lee churned over the western Atlantic on Saturday with maximum sustained winds of 80 miles per hour toward southern New England and Atlantic Canada, prompting a hurricane watch for parts of Canada and a tropical storm warning for areas along the Massachusetts coast, forecasters said.

Lee is approaching the Canadian province of Nova Scotia,, and brought tropical storm conditions to parts of coastal New England and Atlantic Canada on Saturday, the National Hurricane Center said in a 5 a.m. advisory. These conditions are likely to lead to downed trees and potential power outages.

Lee became the season’s first Category 5 storm last Friday before gradually weakening this week. While the storm is expected to lose strength on Saturday, forecasters cautioned that Lee was still expected to be a “large and dangerous” storm when it hit eastern New England and Atlantic Canada.

Hurricane-force winds extend as much as 115 miles from the center and tropical storm-force winds extend outward by three times that distance.

A hurricane watch is in effect for New Brunswick from the Canadian Border to Point Lepreau; and Nova Scotia from Digby to Medway Harbour. Hurricane conditions are possible in these areas Saturday.

A tropical storm warning has been issued for Westport, Mass., to the Canadian border; Martha’s Vineyard and Nantucket; New Brunswick from the Canadian border to Fort Lawrence, including Grand Manan Island; New Brunswick from Shediac to Tidnishand, and Nova Scotia from Fort Lawrence to Point Tupper.

In Massachusetts, warnings are in effect for Nantucket, Chatham, Falmouth, Provincetown, Gloucester, Quincy, Brockton, Vineyard Haven, Mattapoisett, Boston, Plymouth, Fall River, and New Bedford.

Forecasters saidthat the storm had been moving north , and predicted it would continue in a northward motion, with the center of Lee completing its approach toward western Nova Scotia around midday. “Lee is then expected to turn toward the north-northeast and northeast and move across Atlantic Canada tonight and Sunday,” they said.

The National Weather Service reported Saturday that winds should peak in the morning before diminishing throughout the day. Rain across eastern Massachusetts was forecast to end by early Saturday afternoon.

Weather forecast, Sept. 16-18.NWS Boston

Maximum Wind Gust Forecast, Sept. 16-18.NWS Boston

From Friday through Saturday night, Lee is forecast to bring 1 to 4 inches of rain across far eastern Massachusetts and eastern Maine into portions of Canada. This may produce localized urban and small stream flooding, forecasters said.

Swells generated by Lee were affecting the US Virgin Islands, Puerto Rico, Hispaniola, the Turks and Caicos Islands, the Bahamas, Bermuda, the east coast of the United States, and Atlantic Canada on Saturday morning. Forecasters expected surge flooding to depend on surge timing but warned that the risk of rough surf, coastal erosion, and life-threatening rip currents remain possible. Rivers could quickly rise with swifter currents and small streams may overflow. Flood waters may enter a few structures, and brief road and bridge closures are possible.

Concerns are elevated for flooding across Cape Cod Bay and on Nantucket. Elsewhere along the coast and on Martha’s Vineyard, the risk of coastal flooding is lower but still present, forecasters said. Water could reach between 1 and 3 feet in Cape Cod, Martha’s Vineyard and Nantucket, and Boston Harbor if peak surge occurred simultaneously with high tide.