A powerful blizzard is pummeling Massachusetts tonight with heavy snow and howling winds as residents hunker down in their homes. The potentially historic storm is expected to continue into the morning, dumping more than 2 feet of snow in some areas, whipping winds up to 70 miles per hour, and battering the coast with giant waves.
Utilities reported about 40,000 power outages this evening as winds downed tree limbs and wires.
In Marshfield, officials said they expected to ask shorefront residents to evacuate themselves because of concerns about storm-driven tides tonight and Saturday morning.
Roads emptied out late this afternoon as drivers apparently heeded an extremely rare order issued by Governor Deval Patrick banning driving after 4 p.m.
Patrick announced the travel ban at a news conference this afternoon at the state’s emergency bunker, where he also announced that he was declaring a state of emergency to allow the state to take special steps and mobilize assets to ensure residents’ safety.
The storm, which began at mid-morning in Boston, had dumped up to 7 inches of snow in some areas by mid-evening.
By early evening, the National Weather Service said, winds were gusting to 49 miles per hour in Nantucket, 51 in Martha’s Vineyard, 51 in Hingham, 49 in Scituate, and 46 in Brookline. The Blue Hill Observatory in Milton reported a gust of 53 miles per hour.
The National Weather Service said it had received numerous reports of thunder in the Interstate 95 corridor from Rhode Island to Boston, a phenomenon called thundersnow. Globe reporters in Scituate and downtown Boston reported hearing the booms.
But boston.com weather blogger and meteorologist David Epstein said the storm had plenty more punch. He said the storm would be at its most intense until 5 a.m. Saturday.
National Weather Service meteorologist Bill Simpson said 18 to 24 inches of snow are expected in most areas of the state. Isolated areas could get more, he said. A weather service forecast discussion said some areas could get up to 30 inches, which was down slightly from earlier predictions that the state could see up to 3 feet.
Simpson said it was a good thing that the brunt of the storm is expected to hit from nightfall until Saturday morning so people would be off the streets and cleanup efforts could take place.
The storm was the product of two storms that had merged, one bringing cold air from the north and one moist air from the south, causing a rapidly strengthening storm known in weather jargon as a “meteorological bomb,” forecasters said, saying it was a classic setup for a snowstorm.
Today’s blizzard came a day after the 35th anniversary of the Blizzard of ‘78, an epic storm that is etched in the memories of many Bay State residents.
It also came as a rebuke after a winter and a half of mild weather that made some wonder if New England winters had lost their oomph.
Kurt Schwartz, director of the Massachusetts Emergency Management Agency, said at the news conference that the travel ban announced by Patrick applied to all roads in the state, but there were various exceptions, such as for public safety, media, and vehicles supplying essential businesses like convenience and hardware stores. Violating the travel ban, he said, could incur a penalty of a year in jail and a $500 fine.
Patrick emphasized that the point of the ban, which had not been used since the Blizzard of ‘78, was not to penalize people but “to emphasize how critical it is that nonessential travel on the roads cease.”
State officials also dropped tolls on the Massachusetts Turnpike this afternoon to help speed people to their destinations.
Patrick said 1,000 National Guard members were active today and he expected that as many as 5,000 would be activated this weekend.
State transportation officials said that by 4 p.m. there were 3,464 crews out plowing roads covered with slush and snow.
State and local officials had already decided to shut the MBTA down at 3:30 p.m., close school systems, keep nonessential state workers at home and to urge the private sector to follow suit.
With snow pelting down and wild winds blowing, “whiteout conditions are anticipated as roads become snow covered by this evening commute,’’ the weather service said today in blizzard warnings covering Eastern and Southeastern Massachusetts. Strong north-northeast winds are anticipated blowing 30 to 40 miles per hour and gusting up to 70 miles per hour, while temperatures linger in the upper 20s.
The weather service also issued coastal flood warnings, saying that the storm will produce moderate coastal flooding this evening and moderate to major coastal flooding Saturday morning as large waves, some of them nearly 30 feet high, pound the shore and devour beaches.
Shore roads may be flooded and some shorefront homes may be damaged during the Saturday morning high tide, the forecasters warned.
The state’s court system shut down at noon today, but judges will still be on call to handle emergencies, such as requests for restraining orders, the court system has announced.
The MBTA hopes to resume service by Monday.
Airlines at Logan International Airport will wind down flight operations this afternoon; scheduled flights could resume Saturday afternoon, airport officials said.
Amtrak is canceling service between New York and Boston starting Friday afternoon, and is also suspending trains out of Springfield, Vermont, and Maine. Saturday cancellations have not yet been determined.
All four major utilities prepared extensively and at least one of them, NStar, canceled workers’ vacations and ordered all workers to be available, going on its highest level of alert, officials said.
At a morning news conference, Boston Mayor Thomas M. Menino warned, “This is a very large and powerful storm.”
He said city buildings were closing at noon and urged people to stay at home and let the city’s public works crews “do their job” cleaning up the snow.
Cars parked on central arteries will be towed under the emergency order, officials said.
The largest city in the state will have more than 600 pieces of equipment on the road at the height of the storm, Menino said, and has 34,000 tons of salt ready. Officials urged patience among residents, saying it will take time to clear the roads.
Officials also advised people to call 911 if they see homeless people outside who seem disoriented. “There’s no reason for anyone without a home to be outside during the storm,” said Barbara Ferrer, who directs the city’s health commission.
A few light flakes began dancing aimlessly down from the sky in Boston at mid-morning, in a picturesque prelude to the blizzard blast.
Inside the iconic Charlie’s Sandwich Shoppe in the South End at 9:28 a.m., a cry went out, “Snow!”
The weather service also warned mariners that the storm would bring hurricane force winds to Georges Bank.Globe correspondent Derek Anderson, and Erin Ailworth, Michael Levenson, Carolyn Johnson, Akilah Johnson and Stephen Smith of the Globe staff contributed to this report.