Snow from this morning's Alberta Clipper will continue to wind down from west to east through the early afternoon hours. Most will be just about done with the snow by midday, but Maine will naturally be in it a bit longer being the farthest east. The big question this afternoon will be cloud cover. Typically, systems that see a westerly flow post-storm see rapid clearing, however, a temperature inversion may trap moisture in the low-levels, causing a slower than usual clearing. The afternoon may be stubbornly cloudy if this inversion holds.
Below: HRRR showing potential weather around midday:
After this clipper moves through the region, high pressure will take over for the remainder of the week, leading to calm and mostly dry conditions for New England. The only real precipitation chance will be some ocean-effect snow/rain showers across southeast Massachusetts on Christmas Day. Christmas itself will be a quiet, calm and seasonable day with variable clouds. For many, the day may have just the right amount of chill in the air without escalating to a biting or bitter cold.
Below: Weather across the country for Christmas Day/start of Hanukkah:
With dry and calm conditions for the remainder of the week, the focus will be on temperatures. The week will feature a gradual warming trend, with each day likely a bit warmer than the last through the rest of the week. This warm-up will be subdued initially for New England. An expansive mild air mass will build over the central United States and much of Canada and begin to push eastward.
New England, however, will likely miss a bulk of this warmth initially as a nearly stationary surface high pressure just to the north of the region will continue to filter colder air into the region at the surface. It will warm-up compared to the beginning of the week, but this warm-up will likely be around seasonable to slightly above average levels rather than well above average like areas farther west.
Below: CMC showing temperature departure from average on Thursday afternoon. You can see wide swaths of well above average warmth across North America, but locally, it is much more subdued:
This surface high pressure will allow for New England's generally cold nights to continue over the next few nights, with lows in the single digits north to upper teens south through late week. These cold starts will be harder to recover from during the day with a weak sun angle, keeping high temperatures capped to around seasonable levels rather than shooting well above average.
Below: Euro showing temperature departure from average Thursday morning. You can see a blob of cold air over New England, which represents the continued cold nights while areas to the north and west will see much milder morning lows:
The inversion that will be in place may limit radiational cooling to an extent with cloud cover hanging around through Thursday morning, but it will still get cold overnight. Overall, temperatures will be tricky this week as the cold surface high pressure likely helps create that inversion, which is when there is a layer of warm air aloft, trapping colder air at the surface in the mountain valleys and lower elevations.
This inversion may lead to colder temperatures relative to average within the mountain valleys and lower elevations of New England while the mountains see more mild conditions (again, relative to average, it won't actually be "warm" in the mountains). This temperature inversion may be most noticeable on Thursday afternoon.
Below: CMC showing temperature departure from average on Thursday afternoon. This is the same graphic as the one showing Thursday afternoon for all of North America above, just zoomed in on the northeast. You can see milder conditions relative to average in higher elevation areas with cooler conditions in the lower elevations:
With all of that said, the week will see a gradual warming trend, with each day likely getting a notch warmer than the last, as stated in the beginning. By the weekend, more warmth will likely make it into the region as the milder air mass continues to spread eastward. This will come as New England's next system approaches from the Great Lakes. With a warming trend leading up to the event, it's currently poised to be a rainfall-dominated event for many.
Depending on the timing of both the arrival of the storm and the departure of the stubborn surface high pressure, there could be a period of freezing rain, sleet or snow across New England before the colder air at the surface erodes away. As of now, the timing of the start of precipitation is leaning toward Sunday afternoon or evening, but the strong and stubborn ridging could delay the arrival. More details on timing and precipitation type will come as the week goes on.
Below: Current weather map for Monday morning (December 30):
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