Gov. Maura Healey declared a state of emergency Sunday, advising people to “stay indoors” and forecasting whiteout conditions, coastal flooding and power outages from heavy, wind-whipped snow overnight and through Monday.

“People do need to be off the roads during the duration of this storm. That’s what I’m asking the public to do,” Healey said during a 1 p.m. press conference when she announced the emergency declaration and said she activated 200 National Guard members to help with rescue response and debris removal.

Describing the system as a “serious nor’easter” and a “serious blizzard,” Healey said heavy snowfall will begin around 10 p.m. Sunday and continue throughout Monday. Expected snow totals range from 12 to 18 inches across the state, with up to two feet in parts of the Greater Boston area.

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Winds on the coast will gust to 75 miles per hour and wind-chill temperatures Monday will be in the low teens, according to Healey, who declared a “strong likelihood of power outages and downed trees.”

“We are expecting significant power outages,” Healey said. “If you do lose power, please call 211. Call 211 and you will find out where the nearest warming center is and get assistance getting there.”

Healey and legislative leaders instructed employees to work remotely if they can Monday; House and Senate sessions planned for Monday were canceled, and the branches will be closed Monday. Healey called it a “remote telework day” for non-emergency executive branch employees and urged private employers to take the same approach, which would help keep vehicles off the roads so plow operators can clear the streets.

Without power, remote work efforts might also run into trouble. Energy Secretary Rebecca Tepper said she has been in touch with utilities “constantly” over the last two days and will stay in communication with them.

“Their teams are prepared and activated ahead of this storm,” Tepper said. “As others have said, we are expecting windy conditions and wet snow, and there is already snow on the trees. These conditions increase the likelihood of power outages due to the risk of falling trees. We are expecting significant outages in this storm, and it may take multiple days to restore power. Utilities have pre-staged additional line and tree crews on the Cape, Martha’s Vineyard, Nantucket and other areas expected to receive the greatest impact.”

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Snow management and removal is also shaping up as an extra challenge since much of the snow that was dumped across the state during a late-January storm has stuck around during the cold weeks since then.

Healey on Sunday ordered the activation of the state emergency response center in Framingham, and regional centers in Agawam, Franklin and Tewksbury will be activated at 7 a.m. Monday. State emergency management officials are also sending a local coordinator to Barnstable County since Cape Cod is expected to be hit hard.

Transportation Secretary Phil Eng said air travelers should check with their airlines about flights. “Most likely, many of them, if not all, will be canceled tomorrow,” he said.

Eng called it “a blizzard-type storm” with “strong, sustained winds throughout the storm” and snowfall rates that he said could exceed the forecast of one to three inches per hour.

“That is poor to zero visibility, possibly whiteout conditions,” he said. “We strongly encourage do not travel unless you have to and you have no choice. If it’s essential travel, check to see if perhaps you could reschedule. We really recommend people stay home during the snow event.”

Highway Administrator Jonathan Gulliver said salt supplies are full and the state expects a “full callout for the duration,” which means about 3,000 pieces of snow and ice-fighting equipment will be deployed.

“We expect that gradual improvements will happen late tomorrow afternoon and as the snowfall tapers off,” Gulliver said. “But this is also the kind of storm where you’re going to have a long cleanup period. So highways will be down to pavement, I expect, about three or four hours after the storm ends, and certainly be ready for the Tuesday commute. But there is significant cleanup that’s going to be required throughout the week on secondary roads, and especially local roads.”

A commercial vehicle restriction went into effect at 5 p.m. Sunday, which means tractor trailers, tandems, box trucks and special permit trucks will be restricted from traveling until the storm is over, Gulliver said. Truck deliveries of food, fuel and medical supplies will not be subject to the restrictions.

Michael P. Norton is the editor of State House News Service and State Affairs Pro Massachusetts. Reach him at mnorton@stateaffairs.com.