What was shaping up as a historic two-day winter storm hit southern Maine a little earlier and more intensely than expected Friday, forcing schools and businesses to close and prompting Gov. Paul LePage to declare a limited state of emergency.

Steady snowfall snarled Friday morning’s commute, especially on Interstate 295 southbound, where a 19-car pileup occurred about 7:30 a.m. near Exit 11 in Falmouth.

Only minor injuries were reported, but traffic was at a near standstill for more than an hour, said emergency officials. Maine Turnpike officials cautioned drivers to avoid any unnecessary travel.

The storm dumped 12.3 inches of snow in Portland by 12:20 a.m., and forecasters expected the heaviest snowfall overnight and early Saturday morning.

Temperatures never rose above the teens Friday, and weren’t expected to rise above the low 20s Saturday, with snow continuing for most of the day.

“We’re still going to be measuring this in feet, not inches, by the time it’s over,” said Mike Cempa with the National Weather Service in Gray.

The weather service said it expected the storm to bring the biggest snowfall to Maine since 1979. The forecast called for about 28 inches in Portland — the total from the 1979 storm was 27.9 inches — by the time the storm winds down late Saturday.

Overnight winds were expected to gust to 50 to 60 mph, so significant drifts were expected to form.

With that forecast, the U.S. Postal Service took the rare step – possibly unprecedented – of announcing that post offices in Maine, New Hampshire and Vermont will be closed Saturday and no mail will be delivered.

“This weather event is an extreme circumstance and it has the potential to be unprecedented,” said Tom Rizzo, a spokesman for the Postal Service in Maine.

He said the Postal Service has, in a few cases, allowed offices to close early or pulled in carriers early, but in 20 years in Maine he can’t remember officials deciding a day in advance not to deliver mail or open post offices.

Cempa said the snowfall was heavier than expected Friday, especially in coastal areas, because of cold air over warm water. Early forecasts called for 1 to 2 inches of snow to fall early Friday, with the storm gathering intensity Friday afternoon.

Cempa said the snow was expected to be relatively light and fluffy, reducing the possibility of widespread power outages.

“We’ll have high winds, which can be a problem, but it won’t be complicated by heavy, wet snow weighing down trees and power lines,” he said.

The governor’s office said it was in contact with Central Maine Power Co. and Bangor Hydro Electric officials, who had utility trucks ready to provide storm response.

Both utilities have coordinated storm preparation efforts, lining up contract crews to assist local crews if the storm causes widespread damage.

By midnight, CMP was reporting 775 customers without power, all in Saco, but the number was expected to grow as the winds increased overnight.

LePage’s emergency declaration, issued around 3 p.m. Friday, allows extended hours for utility workers and allows crews from Canada to assist with any needed repairs.

“The ability to have electrical service repaired quickly is critical to protect public health and safety of Mainers,” LePage said. “It takes a tremendous amount of effort to prepare for and clean up these winter storms, but we are well-equipped.”

Flooding remained a concern for coastal areas, with high tide around 9 a.m. Saturday expected to be exceptionally high.

The Portland International Jetport was mostly empty by about 10 a.m. Friday. Dozens of flights had been canceled. The last flight to leave the airport departed shortly before 1 p.m. and nearly every flight in or out of the Jetport until late afternoon Saturday had already been cancelled Friday.

Travelers were advised to check the airport’s website, www.portlandjetport.org, or their airlines before driving to the airport for flights Saturday and Sunday. Dozens of Saturday morning flights had been canceled by midday Friday.

The Amtrak Downeaster halted its train service Friday between Brunswick and Portland, and between Portland and Boston.

Patricia Quinn, executive director of the Northern New England Passenger Rail Authority, said the first two trains out of Maine on Friday, a 5:45 a.m. departure from Portland and a 7:05 a.m. departure from Brunswick, left on schedule. All other runs were canceled.

A return train left Boston for Portland at 1 p.m. before service was shut down for the day.

The first two southbound runs Saturday, scheduled to leave at 5:35 a.m. from Portland and 7:05 a.m. from Brunswick, were canceled, as were the first two northbound runs of the day, scheduled to leave Boston at 9:05 and 11:35 a.m.

A decision on the rest of Saturday’s schedule was expected to be made Saturday morning.

Quinn said passengers should check Amtrak’s website regularly. “We have crews standing by. We’re not going to compromise safety,” she said.

Most bus routes in Greater Portland were altered Friday and canceled for Saturday, as was bus service from Portland to Boston and beyond.

LePage announced shortly before 2 p.m. that all state offices would close by 3 p.m. Friday.

Most schools and colleges across Maine canceled classes Friday, and most events planned for Friday and Saturday were canceled or postponed.

The South Portland Public Library announced that it was canceling its “Winter Celebration” scheduled for Saturday because of “too much winter, all of a sudden.”

The event has been rescheduled for Feb. 16.

All Disney On Ice performances scheduled Friday at the Cumberland County Civic Center were canceled, as were two Saturday shows. A performance was added at 7 p.m. Sunday.

Ticket holders for the three canceled performances can exchange their tickets at the Civic Center box office.

– Staff Writers Edward D. Murphy, Noel K. Gallagher, Eric Russell and David Hench contributed to this report.