Unsettled Weather & Cold Air Remain the Name of the Game for New England

Tonight into early Sunday will see a cold front push through New England. This front is unlikely to completely clear New England, so high temperatures on Sunday will be similar to this afternoon. This afternoon will also see any spotty snow shower activity from a coastal storm passing well to our south come to an end. The passage of this cold front will allow for another cold night, with lows in the low teens north to low 20s south.

The next quick-hitting system will zip through Sunday night into Monday morning. This clipper-system will likely dive through the middle of northern New England Sunday evening, and exit into the Gulf of Maine during the pre-dawn hours Monday. This system will likely deliver a quick shot of some snow, mainly across northern New England, Sunday night. 1-2 inches appears to be the most likely outcome for areas that see more persistent snow showers.

It will be northern New England that will have the best chance for light accumulations with this one as these clipper-type systems tend to deposit their most snow on the northern side of the center of the low pressure system. With that said, the exact track of the system through New England will determine where the band of more widespread snow sets up. This storm will push through quickly during the overnight hours.

Below: HRRR showing potential weather around midnight Sunday night:

Earlier, it looked possible that the low would deepen in the Gulf of Maine and potentially bring several inches of snow to a portion of the region. Guidance has since backed off of that scenario, with probabilities of even 2 inches of snow having fallen to 30% for northern Vermont and New Hampshire. With that said, there is the potential for an inverted trough to develop, which occurs when pressure increases from south to north, which is typically the opposite of mid-level troughs. Normally, the lowest pressure and heights are located on the south side of the trough, not the north side.

These troughs can create enhanced precipitation rates on the northwest side of the system. This development could push the coastal plain of northern New England, particularly Maine's coast, toward that 2 inch mark. The main issue for the storm is that it's moving so fast, no matter how it develops, it will swing through in the span of a few hours, significantly limiting this system's potential.

Below: Current probability of at least 1 inch of snow Sunday night to Monday morning. Note the higher probabilities just off the coast of Maine. That is a symptom of the potential for an inverted trough and enhanced precipitation rates to develop:

These clipper systems often swing the door wide open for blasts of cold air, and this one is no exception. An Arctic air mass will advect into New England once the system, and its cold front, exit the region. Temperatures at the low-levels will once again drop to around 0°, supporting surface temperatures in the teens and 20s region-wide once again for Monday. Wind chills will likely hover in the single digits, on either side of 0, for much of the day.

Another clipper system will likely skirt to the north of New England later Tuesday into Wednesday morning. With this system passing farther north, there is a lower chance of any appreciable activity in New England. Should it cross near the Canadian border, light snow showers may be on tap. If it crosses farther north, drier weather would likely win out.

The next, more organized, system looks to follow quickly behind this one. At this point, this system will likely involve an area of low pressure moving out of the Great Lakes and through western New England. As always, how this system plays out will come down to the track. Whether or not a secondary low can form will also affect precipitation type across New England. Temperatures also look to become more mild as we head toward midweek next week.

Early trends favor an inside runner with the potential for mixing and plain rainfall across southern and coastal areas. More wintry precipitation would remain possible well north and west in the region. The farther north and west this system tracks, the warmer and wetter the system would be across the board and vice versa. If a secondary low can form offshore, the system would trend colder. Being a week out with a large range in outcomes, we'll leave this one at that for now.

Below: Current probability of impactful winter weather next Wednesday to Thursday:

Looking at the longer-range picture, the ridge-in-the-west-trough-in-the-east pattern is expected to remain stubbornly in place. This pattern will likely remain very pronounced through the end of next week (December 12-13). This will keep the northeast generally on the colder side. This will also keep the door open for unsettled weather to continue after midweek next week. It should be noted that the 6-10 day outlook below has a rare 5 out of 5 confidence rating by the Climate Prediction Center, indicating much above average confidence in the outlook.

An established cross-polar flow will keep a cold northwesterly surface flow around. Whenever surface flow favors winds out of the northwest through the middle of December, New England will be susceptible to Arctic air (winds won't always be out of the northwest, which will allow for moderation between cold snaps).

A cross-polar flow often involves a highly amplified ridge in the west and another ridge farther east extending toward the North Pole. General troughing between these two ridges sees a corridor open up, allowing flow from across the Polar-region into the central and eastern United States. This type of setup can bring the United States its coldest Arctic Blasts of the season, if other factors line up correctly as well.

Below: 500mb height anomaly early next week, during the cold snap expected around December 8-9. You can see what's described in the paragraph above setting up: