A storm packing heavy, wet snow moved across Maine on Friday, sending hundreds of drivers spinning off roads and carrying with it the gloomy prospect of adding to the deep snowpack in parts of the state, increasing worries of spring flooding.

A winter storm warning was posted for much of Maine, with up to 16 inches of snow expected in higher elevations. Lesser accumulations of 3 to 6 inches were expected along the coast, where there was a mixture of snow and rain. The storm was expected to continue today.

In one of the worst road situations, the storm forced police to stop traffic on Route 1A, the main road between Ellsworth and Bangor. Ellsworth police closed the road in both directions at about 6 p.m. after traffic backed up behind tractor-trailers that were unable to make it up McGowan’s Hill north of the city.

The snowfall created slippery roads throughout Hancock County late Friday afternoon, resulting in numerous accidents, including one rollover on Route 1A in Ellsworth. Most accidents resulted only in property damage, although several people from separate accidents were taken to the hospital with minor injuries.

Maine State Police were investigating an accident on Interstate 95 south in Old Town, just below Exit 53, where a motorist was reported ejected from the car. The vehicle rolled over, landing on its roof. No information was immediately available about the driver.

Several other vehicles were off the interstate, keeping road crews, police, ambulance crews and towing services extremely busy.

Dispatchers at state police headquarters in Orono, Augusta and at the Somerset County Communications Center were swamped with accident reports for most of Friday afternoon.

In Somerset County, dispatchers said more than 15 accidents were reported in a two-hour span at midafternoon.

In Augusta, dispatchers reported being “very busy” handling dozens of calls from the coast to central Maine.

At one point in the afternoon, three separate rollovers were reported simultaneously in eastern Somerset County, on Interstate 95 in Palmyra and on Route 220 in Detroit.

No serious injuries were reported as a result of the Somerset County accidents.

The snow seemed to catch people off guard in southern Maine as well, where many were expecting mostly rain, said Trooper John Hainey.

On the Maine Turnpike alone, several hundred cars and trucks slid off the highway during the course of the day. During the evening commute, tow trucks were scrambling to retrieve 50 cars that were off the road, he said.

“It’s nasty out there,” he said. No serious injuries were reported.

The snowstorm was bad enough that Delta Air Lines canceled all of its flights Friday evening to and from the Portland International Jetport. The jetport itself remained open, despite the snowy conditions. Bangor International Airport also remained open.

The fresh snow only added to the deep snowpack, which, combined with the expected rain and higher temperatures on Sunday, could provide the necessary ingredients for spring floods next week, officials said.

“We don’t want to be panicmongers, but what I’m hearing is the potential for significant flooding,” said Joseph Tinkham, commissioner of the Department of Defense, Veterans and Emergency Management.

The River Flow Advisory Commission met earlier in the week to discuss the likelihood of flooding over the next three weeks or so.

River flooding rarely occurs from snowmelt alone, but severe floods can result from the combination of snowmelt, a string of warm days and normal to above-normal rainfall.

Gov. Angus King on Thursday issued a flood advisory to Mainers living along the Kennebec, Androscoggin, Piscataquis and Penobscot rivers.

The advisory said residents and businesses in those areas should monitor weather conditions closely and devise a response plan.

“While it’s important that no one panic over the possibility of flooding, it’s equally crucial that we keep an eye on Mother Nature and be prepared to respond if flooding does occur,” King said in the flood advisory.