The frontal boundary to our north has dropped south and moved across northeast Massachusetts this morning. There is a wide temperature difference with daybreak temperatures in the upper 30s and low 40s north of Boston to the 50s to near 60 along the South Shore and generally in the 50s southwest and west of the city. Communities north and northwest of Boston have seen as much as a 15 degree temperature drop since midnight with the passage of the front.
Although the forecast was for this frontal boundary to remain north of our area through the weekend there was a hint by some models that it might push as far south as southeast New Hampshire by Sunday morning. It has now pushed even further south than expected and this changes everything from the temperatures to the possibility of frozen precipitation in some areas.
The thought of temperatures well into the 50s north of Boston is no longer a reality today. For you readers that visit this page regularly you know that my focus is on the immediate Boston area, North Shore and western suburbs. With that in mind it is our forecast area that will see the greatest impacts from the frontal passage this morning. Also, showers have been far and few between overnight, generally drying out as they attempted to progress eastward and that will probably be the trend through at least midday. We will be stuck in the low clouds, patchy fog and mist for today with a few showers through the afternoon.
The bigger concern are those areas along the Merrimack Valley and central Essex County where temperatures could inch down to around the freezing point. This would change any plain rain showers to freezing rain and or freezing drizzle in those locations. This is being monitored closely and the National Weather Service may issue Freezing Rain Advisories for portions of Essex and Middlesex Counties later today. They have already expanded the Freezing Rain Advisory just over the New Hampshire border in Hillsborough County.
The front should stall south of Boston and then retreat as a warm front later tonight and early on Monday, although how far north it gets remains a question. Also, low pressure will ripple along the front later tonight and Monday and this will enhance the opportunity for rain showers tonight and through the day on Monday. Once the low pulls away skies gradually improve as much colder air overspreads the area Tuesday and Christmas Day.
72 Hour Outlook:
Sunday: Turning much cooler with temperatures falling into the mid and upper 30s, perhaps low 30s across northern areas of the forecast area. Mist and fog this morning, a few showers included for this afternoon. Chance of freezing rain and freezing drizzle this afternoon across northern tier communities. Northeast winds 5 to 15 mph.
Tonight: Much of same. Temperatures could rise slowly toward morning. Otherwise temperatures in the 30s with periods of showers. Freezing rain possible across Merrimack Valley. Areas of fog. Northeast winds may become southwest toward morning, especially southern portions of forecast area.
Monday: Showers likely. Patchy fog. Milder, highs in the mid to upper 40s. Winds shifting to northwest 5 to 10 mph.
Monday night: Considerable cloudiness with a chance of showers, possibly mixing with snow before ending. Turning much cooler. Lows in the upper 20s. Northwest winds 10 to 20 mph, possibly gusting to 25 mph.
Tuesday: Early clouds followed by partial clearing. Much colder and breezy. Highs in the low 30s.
Christmas Eve: Fair skies and much colder. Lows in the low to mid teens.