The National Weather Service is keeping an eye on a strong storm system that is expected to move up the eastern seaboard Sunday, prompting a blizzard watch through Monday afternoon.

Accumulating snowfall will enter southern Maine early Sunday evening, and will continue, becoming heavy at times, into Monday afternoon.

In addition to snow, storm force winds over the coastal waters are expected to build large waves along shorelines, according to the NWS. Winds are predicted to be strongest early Monday morning.

Snow accumulation of 12 inches or more are possible, with the highest accumulations likely to be in coastal communities. Roads are expected to become snow covered and slippery. Temperatures are expected in the upper 20s inland to lower 30s along the immediate coast. North winds of 20 to 30 mph with gusts of 45 mph possible.

According to the NWS, there is potential for high impact, with heavy snow and strong winds creating very hazardous travel conditions. In addition, blowing and drifting snow could cause poor visibility and whiteout conditions at times.

The extended forecast, as of 3 p.m. on Dec. 25, follows.

Saturday night: Increasing clouds, with a low around 16 F. North wind between 3 and 5 mph.

Sunday: A chance of snow after 1 p.m. Cloudy, with a high near 32 F. North wind between 5 and 11 mph. Chance of precipitation is 40 percent. Little or no snow accumulation expected.

Sunday night: Snow and areas of blowing snow. Low around 27 F. Windy, with a northeast wind 15 to 18 mph increasing to between 27 and 30 mph. Winds could gust as high as 45 mph. Chance of precipitation is 100 percent. New snow accumulation of 6 to 10 inches possible.

Monday: Snow and areas of blowing snow before 1pm, then a chance of snow after 1 p.m. The snow could be heavy at times. High near 28 F. Windy, with a north wind between 21 and 26 mph, with gusts as high as 36 mph. Chance of precipitation is 90 percent.

Monday night: Mostly clear with a low around 12 F.Blustery, with a northwest wind between 15 and 20 mph.