“Accumulation is expected to be swift, heavy, and dangerous,” Patrick said.
Nonessential state employees have been asked to work from home Friday, and Patrick urged private companies to do the same.
The predicted 2 to 3 feet of snow will be lashed by winds gusting up to 65 miles per hour into drifts as deep as 5 feet, the National Weather Service said Thursday.
The Weather Service warned that the storm would pose a threat to people’s lives and property and that conditions would deteriorate quickly as the storm develops Friday. Travel will become nearly impossible by the Friday evening commute into Saturday.
“The sooner you can be off the roads the better,” said Weather Service meteorologist William Babcock. “You want to give yourself some time to be at your safe spot before the storm hits its strongest.” The Weather Service issued blizzard warnings for all of Eastern and Southeastern Massachusetts.
The MBTA, buses, and commuter rail will stop running at 3:30 p.m. Friday, ahead of the worst of the storm. Officials hope to have the T up and running again by Monday.
Residents’ rush to stock up caused its own problems Thursday. In what appeared to be the epitome of the frenzy to prepare, so many people were shopping that the Salem Fire Department responded to the Market Basket supermarket for overcrowding, a fire official said.
Declaring that Boston is ready for what may be a historic blizzard, Mayor Thomas M. Menino canceled school in the city for Friday and urged people to stay off roads and out of downtown.
“We haven’t had a snowstorm of this size in many years,” Menino said. “We are hardy New Englanders used to these storms, but we want people to use common sense and stay off the streets.”
Before dawn Friday, 200 plows and salt spreaders will be crisscrossing roads in Boston, Menino said. By 9 a.m., officials plan to increase the number of plows and salt spreaders to 600. Boston will increase the number of public safety officials on the streets as well, he said.
A snow emergency will take effect at noon Friday, which bans parking on major thoroughfares. Roughly 15,000 parking spaces will be available at discounted rates at dozens of private and municipal garages. Friday trash pickup will be moved up to 6 a.m. in an effort to get garbage trucks off streets early.
At a State House press conference, Transportation Secretary Richard A. Davey said crews would pre-treat roads with salt Thursday night.
Patrick said he hopes residents will heed warnings to stay home and allow plows free range, but, he said, “if I have to order the roads to be cleared, I will.”
By Thursday morning, the MBTA said, crews had covered exposed electrical connections on Green Line cars to prevent freezing and damage from snow and inspected sleet scrapers on subway cars.
T officials decided to keep the system running until 3:30 p.m. Friday to allow first responders and hospital workers to get to their evening shifts and home from day shifts.
Several trains will be run slowly along the lines throughout Friday night to keep the rails clear of snow, though those trains will not be accepting passengers.
This is the third time the T has shut down service in the past 18 months due to weather concerns, Davey said.
Beverly A. Scott, the general manager of the MBTA, said she and Davey decided to halt service after forecasts reported an increased severity of the storm.
“There is nothing heroic about pushing the envelope beyond which you know you should,” Scott said. “It does no one any good to have 40-foot or 60-foot buses stuck all over the streets.”
As soon as it is safe, Scott said, T staff will attempt to restore service to trains and buses.
“We will do everything we reasonably can and possibly can to minimize the downtime,” Scott said.
“The good news is that we have two days to get ready for Monday morning rush hour,” Davey said.
Those planning to get out of town this weekend may find themselves stranded.
Airlines are planning to halt operations at Logan International Airport early Friday afternoon until Saturday afternoon, and possibly until Sunday, Massachusetts Port Authority officials said. Some airlines are offering refunds for flights canceled due to the storm or are waiving change fees for travel scheduled for Friday and Saturday.
With the exception of the Japan Airlines flight to Tokyo, which leaves at noon, there will be no international flights Friday. Airport officials expect Friday morning to be busier than normal as passengers try to get out before the storm hits, and then – nothing.
“It’s going to be a ghost town,” said Edward Freni, director of aviation at Massport, which runs Logan.
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. Affected passengers can get a refund or a voucher for future travel.
As people begin to hunker down in their homes, the governor outlined a number of safety measures, including obeying any evacuation orders, having plenty of food and water on hand, and getting a full tank of gas before the storm hits.
Officials said they are working with the Red Cross to open warming centers throughout the state for all affected residents, who can dial 211 on their phones for more information.
All four major utilities that supply the state have begun extensive preparation, and at least one of them, NStar, has canceled workers’ vacations and ordered all workers to be available, according to Energy and Environmental Affairs Secretary Richard K. Sullivan Jr.
He said the utilities are bringing in outside resources to assist with repairing power lines and restoring electricity.
Deborah Drew, a spokeswoman for National Grid, said about 600 crew members are ready to begin power restoration efforts, as soon as it is safe outside.
“This is supposed to be quite a damaging storm,” Drew said. “It’s very important for customers to be prepared for widespread, prolonged power outages.”
Around the state, residents sought to prepare their homes for the coming storm.
By Thursday morning, more than 300 people had visited Kevin Cunningham’s Model Hardware store in Allston.
The store’s shelves were stocked with 900 shovels and about 73,000 pounds of rock salt, he said, with more on order for Monday.
“This is our Christmas,” Cunningham said.
Employees at the Wine Emporium on Tremont Street in the South End were getting ready for a “busy evening” of people stocking up on distilled essentials ahead of the storm, said clerk Robert Walton.
An employee at the South Bay Home Depot said by phone that customer traffic was higher than usual throughout the day Thursday.
“Shovels, salt, we’ve got lines hanging out,” said one employee. “They’re buying.”
Many aisles were elbow-to-elbow with shoppers Thursday night at the South Bay Stop & Shop, and backed-up checkout lines moved at a snail’s pace.
“Seven o’clock this morning it started,” an employee stocking shelves told a passing customer.
Tisha Williams, 33, of Newton was stocking up on water and canned goods.
“I hope it lives up to all the hype,” she said of the expected storm. “You’ve got to be prepared. Better safe than sorry.”
Traffic was backed up around the state Thursday evening — the evening commute paired with people making last-minute storm preparations lead to the difficult driving conditions, according to the State Police.
After Patrick’s announcement that public transportation would shutter at 3:30 p.m. Friday, frazzled commuters on Twitter frantically tried to organize how they would get home from their jobs, or if they would be going to work at all.
One commuter waiting at Park Street Station, Deborah Reed-Coplin, 51, said she had anticipated the tumult.
“I’m not going to work, I took the day off. I heard about the storm and put in to take the day off,” the Dorchester resident said. “I’m going to just lay low and relax.”Travis Andersen, Katie Johnston, Andrew Ryan, Erin Ailworth, and Martin Finucane of the Globe staff and Globe correspondents Colin A. Young, Haven Orecchio-Egresitz, and Lauren Dezenski contributed to this report. Martine Powers can be reached at mpowers@