Latest Trends on New England's Incoming Weekend System

A large upper-level low pressure system continues to sit around Canada's Hudson Bay. This has rotated yet another shortwave through New England. A clipper-like system will slowly push through northern New England through the day today, bringing continued snow showers and flurries across the north. With generally warming temperatures today, central and southern New England may be more apt to see brief rain showers rather than the flurries that have been seen over the past couple days.

Below: HRRR showing potential weather around mid-afternoon today:

After brief surface ridging between systems on Friday and Saturday, New England's next system will approach later Saturday and Sunday. This will be a frontal system with a primary low lifting well north of New England. A secondary low is poised to lift through northern New England, potentially near the Canadian border, making this system an inside runner. This will lift a warm front into New England, drawing milder air into the region and preventing a widespread snowfall across a large swath of the region.

Trends over the past couple days have pointed to a weaker storm system that is quicker moving. Most guidance agrees that the system will arrive in western New England before midnight on Saturday night. The storm will steadily spread eastward through the rest of Saturday night before peaking for most on Sunday morning. The storm now looks progressive enough to be pushing out of much of New England by Sunday afternoon. Exact timing remains a question, but widespread, steady precipitation will likely transition to more scattered and light showers from west to east through the afternoon.

Below: GFS showing potential weather early Sunday morning (1st image) and early Sunday afternoon (2nd image):

Maine, being the farthest east, will naturally hang onto the storm the longest on Sunday and into Sunday evening. The storm will likely be undergoing some form of cyclogenesis as it moves east of New England. This would allow wrap-around snow to linger longer across eastern Maine. This would keep precipitation going longer in eastern Maine. This precipitation would also be more likely to be snow rather than a mix or rain. The strength and forward movement once the system moves east of New England remains a big question overall.

Below: Euro showing potential weather late Sunday, with a sub-980 storm system wrapping snow into eastern Maine:

Trends have continued to point toward a coastal low developing later occurring around Downeast Maine. This means it will likely be much too late to lock in cold air at the surface for the duration of the storm. This allows for the potential of a widespread wintry mix at the start Saturday night and early Sunday morning before a rain/snow line quickly advances north during the day as milder air gets pushed into New England. At this point, southern New England looks to be mainly rain with the rain/snow line across interior northern New England.

Given the current setup for the remainder of this week, there will likely be plenty of cold air at the surface when precipitation begins to arrive early Sunday morning. This will come as the system lifts its warm front across New England, allowing warmer air to ride over the colder air at the surface. This is a prime setup for a rather messy storm across northern New England with a period of snow, sleet, freezing rain and plain rain all possible. Again, the cold air in southern New England looks marginal at best, which is why the system will likely end up being a majority of rain with only a bit of mixing at the start.

Trends have also pointed toward a slightly weaker storm system overall. This would favor cooler temperatures and lighter precipitation. This trend has come about very recently, but if it were to hold, currently forecast temperatures on Sunday will likely need to be knocked down a few degrees. This is not expected to be enough to change the overall precipitation types of the storm in regards to where rain versus wintry precipitation sets up.

What this may do is allow for a longer period of a wintry mix over interior northern New England. With that said, precipitation would also be generally lighter in this scenario, so this is expected to remain a rather low-impact system for most. A widespread quarter to half inch of precipitation remains likely. This will be pretty much all rain for southern and central New England. Farther north, it will be a mix of plain rain totals and liquid-equivalent ice and snow.

Below: Current probability of impactful winter weather Sunday to Monday morning:

Given the expected setup, the most dominant wintry precipitation looks to be freezing rain rather than sleet. This will come as warm air moves into New England aloft with colder air staying at the surface initially. Given the overall setup, this will likely be a deep layer of warmer air, and with colder air at the surface getting scoured out, freezing rain is expected to win out over sleet. The duration, amount and exact location of freezing rain remains the biggest question as guidance remains split. Once this system comes into view of high-resolution models, this will begin to become more clear.

Below: Current probability of seeing at least a glaze of ice through Sunday morning:

As this system exits, it will drag its cold front across the region, bringing another surge in colder air. This should allow lingering precipitation across the higher terrain to change back to snow. This will set up another chilly week next week. Winds will be elevated after the cold front passage, with gusts of 30-40mph likely later Sunday and Monday for most. High pressure is poised to build back into New England around mid-week.