The messy winter storm that began yesterday afternoon in the mountains and last night closer to the coast will continue throughout the day today as waves of low pressure move along the frontal boundary currently racing south over Southern New England. The airmass battle lines are drawn fairly clearly this morning with the mountains and most of the foothills experiencing pure snow while the coastal plain sees a mix of sleet and freezing rain thanks to a layer of warm air aloft. At this point, nobody is reporting a temperature above freezing and that will remain the case through the rest of the day.
The gradual trend today will be towards cooling of the middle atmosphere, albeit slowly. As a result, look for the sleet/snow line to gradually work its way southeast throughout the day. It should be out of the Lewiston area in the next couple hours, while Portland and Rockland may have to wait until the early afternoon to change over to snow. Around a half-inch of liquid is expected to pile up between now and the middle of the afternoon which should translate to another 4-6″ of snow inland (on top of what you measure walking out the door this morning) and 1-2″ of sleet along the coast.
Another wave of low pressure will pass by during the late afternoon/early evening hours, finally dragging the warm layer aloft offshore. It will bring another ~quarter inch of liquid which will fall as 1-3″ of snow across the entire area. For spots south of Portland especially, that’s most if not all of the snow you’re going to get out of this, though you’ll end up with a nice 4-6″ glacier of extremely heavy/dense snow/sleet mix.
Most of the area has been lucky enough to avoid major ice issues, the exception being far southern NH as expected. Freezing rain will continue mainly south of 101 through the next few hours with up to a quarter inch of accretion possible. That’s enough to cause some problems, especially up on the hills where amounts may be a bit higher, but a changeover to sleet midday should prevent the worst power outage impacts.
Precipitation will wind down from west to east between 7 and 10 PM though flurries may linger into tomorrow morning especially up in the mountains.
Temps today will fall from the mid 10s up north and mid 20s down south this morning to the mid 0s up north and mid 10s down south by this evening.