A doozy of a December storm played havoc Sunday with holiday travel plans across the region and threatened Monday commutes as two systems tangoed over Massachusetts, potentially dumping as much as a foot and a half of snow in some areas.
Most of the state — except for Plymouth and Bristol counties, and the Cape and Islands — is under either a winter weather warning or advisory through 7 a.m. Tuesday in the region’s first significant snowstorm this year, according to the National Weather Service.
By Sunday evening, poor weather conditions were already resulting in motor vehicle accidents, including a five-car crash on Route 16 in Medford and two crashes on the Braga Bridge in Somerset. No life-threatening injuries were reported in any of the incidents, police said.
“We are responding to numerous crashes and spinouts on roads across the state,” State Police spokesman David Procopio said in an e-mail around 8 p.m. “No serious injuries, thankfully.”
Governor Charlie Baker and other state officials held a Sunday night press conference at the Department of Transportation operations center in South Boston, where they said crews were working to get the state’s streets and public transit ready for the storm. They urged commuters to be careful and allow extra time for the next few days, while encouraging the use of public transportation.
“We’re no strangers to winter weather around here, that’s obvious, but folks should plan ahead and anticipate that their commute may be impacted” Monday morning and night, as well as Tuesday morning, Baker said.
Baker said he would not issue a delayed start for state workers Monday, however, as he sometimes does during powerful storms.
The state DOT put into effect a speed restriction to 40 miles per hour from the New York border to East Boston.
The Massachusetts Bay Transportation Authority said in a statement that regularly scheduled service is expected Monday. The agency encouraged riders to get the latest updates by visiting https://mbta.com/winter-weather.
The crews will also be available to respond to incidents during the storm, such as fallen trees, and be stationed near switches, signals, and other facilities to help maintain normal operations, the statement said.
Amtrak officials said they did not expect the storm to affect service, according to a spokeswoman.
The storm began in Massachusetts early Sunday afternoon, when snow began falling in the Westfield area shortly before 2 p.m., according to Bill Simpson, a weather service meteorologist.
Snow was expected to continue in coastal areas, including Boston, until around 8 p.m., then gradually transition to rain, he said. Snowfall in the central and western parts of the state was expected to change over to a wintry mix of snow, sleet, and rain later in the evening.
Those conditions will continue into the Monday morning commute, and travelers in central and western parts of the state could face particularly hazardous travel conditions, he said. Another round of snowfall will hit in time for the Monday afternoon commute, he said.
In addition to the snow, a coastal flood advisory will be in effect between 2 p.m. and 5 p.m. for parts of Essex and Plymouth Counties and Nantucket on Monday, when a surge at high tide could result in minor flooding, according to the weather service.
Boston’s public schools and other offices will be open Monday despite the storm, according to Mayor Martin J. Walsh. School custodians, with the help of Public Works Department crews, will work to clear snow two hours before school begins.
“We are encouraging residents to use caution when traveling, assist older neighbors and those who are disabled, and keep up with the shoveling of their property throughout the storm,” Walsh said.
Some schools in the state’s central and western areas —- where snow totals are expected to be higher than the Boston area — did announce closures for Monday, including public schools in Worcester, Fitchburg, and Leominster, as well as the University of Massachusetts-Lowell and the College of the Holy Cross in Worcester.
The storm, which arrived during one of the busiest travel days of the year, had officials urging travelers leave for home early following the Thanksgiving holiday.
Christy Colburn, of Somerville, took officials’ warning seriously, and ended her family’s weekend trip to New York City early so they could return before the storm struck.
Colburn and her two children got on a bus at 10:30 a.m., but were quickly caught up in bumper-to-bumper traffic.
The trip, which was due to end in Boston at 2:45 p.m., took more than six hours, she said. As they sat in traffic, she reached out to friends online.
“Please keep me & the kids in your thoughts as our bus slowly crawls from NYC to Boston in thick holiday traffic,” Colburn wrote on Twitter at one point, “with a massive storm chasing our tails and a dwindling supply of pre-downloaded video.”
For some travelers trying to get home by air, the path was no easier: At Logan International Airport Sunday, more than 100 flights were canceled, and hundreds more delayed, according to FlightAware.com.
But the scene inside Terminal A Sunday afternoon was relatively calm, as security lines moved quickly, and travelers took inconveniences in stride.
Oscar Sun, an Ohio State student stranded in Boston by a canceled flight, sat on a bench next to his girlfriend, Boston University student Jade Gu. Sun got another flight to Columbus, but not until Monday afternoon. He would have to miss a music class Monday.
“I’m probably just going to book another hotel,” he said.
John O’Brien of Scituate was at Logan trying to get his son Patrick back to school at Ohio State after the younger O’Brien’s flight Sunday had been canceled.
The O’Briens found a workaround: Instead of flying direct, Patrick would go from Boston to Tampa to Atlanta — and then to Columbus.
After his son boarded, John O’Brien sat down in Terminal A with a book until the plane took off, just in case something went awry. If all else failed, O’Brien said, he would drive to Ohio: 13 hours, 802 miles, “driveway to driveway.”
“It’s the first time he’s come home for Thanksgiving,” O’Brien said. “I’m wishing he stayed now; it would have been easier for us.”
Globe correspondent Lucas Phillips contributed to this report. Gal Tziperman Lotan can be reached at email@example.com. John Hilliard can be reached at firstname.lastname@example.org. Contact Abigail Feldman at email@example.com.