This storm will involve an area of low pressure moving to the north of New England with secondary low development off New England's coast. The strength and timing of the secondary low will be the main driver of precipitation types. This low will be weaker initially, allowing warm air into the region aloft. This will transition snow to a mix across southern and central New England. As the low strengthens, it will keep colder air around for eastern and northern Maine and northern New Hampshire, allowing for mostly snow. Heavy snowfall rates are possible across northern Maine.
ALERTS
TIMING
Scattered snow showers will likely break out across western New England through the evening. These snow showers will fill in and move eastward throughout the early morning hours Thursday. By the pre-dawn hours, snow will likely be falling across much of New England as the leading edge of the storm makes it into eastern Maine. Snow will likely already be switching over to a mix across southernmost New England as warmer air works in aloft.
Below: HRRR showing potential weather around midnight tonight (1st image) and the pre-dawn hours Thursday (2nd image):
Throughout the morning hours, a warm air nose will continue to work both north and east, switching the initial burst of snow over to a wintry and eventually plain rain for some. The speed of this transition will be determined by the rate of strengthening of the secondary low as well as its exact track. Widespread warm air advection is expected to be able to occur through much of New England, Even areas that are labeled as "mainly snow" on the precipitation trend graphic below may see a period of mixing in the afternoon.
Below HRRR showing potential weather late Thursday morning:
A dry slot will likely work into New England outside of Maine. This will transition widespread precipitation to scattered showers. Much of New England may just see mainly drizzle/freezing drizzle through the afternoon. Across Maine, the strengthening storm system will allow for steady to, at times, heavy snowfall rates across interior eastern Maine Thursday afternoon. Snow will shut down rather quickly through the evening for northern Maine as the storm quickly moves away.
Below: HRRR showing potential weather early afternoon Thursday (1st image) and early evening Thursday (2nd image):
SNOWFALL
The storm will begin as a burst of snow for all of New England. As the primary low brings warmer air into the region, the snow will likely quickly begin to change over to a mix from south to north and west to east. This will yield minor snowfall for much of New England. Snow totals will gradually increase working northward as the changeover gradually works northward.
A majority of New England will likely end up with 1-4 inches of snow with 3-5 inches in areas that see snow through the entire morning (mainly interior Maine and north of the NH lakes region). The initial burst of snow may be briefly steady to even heavy before the changeover, allowing for these accumulations.
As the storm strengthens in the Gulf of Maine, it will lock colder air across eastern Maine (away from the coast). It will also allow for heavier snowfall rates Thursday afternoon. This will make for the potential for several hours of heavy snow through the afternoon. While the storm is progressive, this should be enough for 6-10 inches of snow to fall across northern Maine, with some communities possibly seeing up to 12 inches.
There will likely be a decently sharp cutoff from areas that have the potential for up to 6 inches and areas that only see a few across eastern Maine. The big question will be how far inland can the mix line push? An onshore flow amid the strengthening system should allow for a period of mixing and rain across coastal Downeast areas. There will likely be a sharp cutoff in snow totals between the areas where mixing occurs and just north of that where all snow occurs.
Below: Current probability of at least six inches of snow:
Across northern Maine, an area of frontogenesis is likely to develop along the system's warm front as it strengthens. With thermal profiles supporting all snow in this area, this could set up a period of 1-2 inch an hour snowfall rates from mid-morning through mid-afternoon for northern Maine. Mesoscale banding will come into play. Where these bands set up will see a decent thump of snow. It's always difficult to pinpoint exactly where these bands will set up, but they will be likely across northern Maine.
BUST POTENTIAL
The main bust potential for northern Maine will come from the speed of the storm. The quick-moving nature will only provide a window of a few hours to really get snowfall rates cranking. Elsewhere in New England, snowfall could end up less than forecast if the secondary low is very slow to form and strengthen. If this occurs, the changeover to a mix and rain will happen very quickly.
MIXING
The setup for this storm is a perfect recipe for a period of mixed precipitation across much of New England. With cold air getting locked at the surface by the secondary low and a warm front rising over the dome of cold air, a period of sleet and freezing rain is likely. As stated before, the changeover from snow to a mix will steadily occur from southwest to northeast, stalling near the New Hampshire mountains and northern Maine, where it will remain mostly snow.
With widespread warm air working in aloft, it will likely set up a deeper layer of warm air with a shallower layer of colder air for southern New England, as well as Vermont and southern New Hampshire. This would likely result in a period of sleet at the onset of the changeover followed by freezing rain/drizzle. The snow to mixing area across Maine (seen on the map above) may feature more sleet, but exactly what falls here is more uncertain.
Light freezing rain/drizzle may last for several hours across interior Massachusetts, southern Vermont and southern New Hampshire. With that said, drier air will work into the snow growth zone Thursday morning. This should lead to lighter precipitation rates during freezing rain. This will keep icing amounts on the lighter side, with no more than a tenth of an inch expected. This is not enough to impact trees and infrastructure, but it's plenty to create very slippery surfaces.
The entire coastal plain of New England will likely see a switch of mixed precipitation to plain rain showers by the late morning to afternoon as the warmer air manages to erode the cold air dome. By this time, however, a dry slot will likely take over, leading to patchy showers or drizzle.
THE NEXT STORM
It seems a track inside the benchmark is becoming more favored at this point. This will create another situation with a snow/mix/rain line across southern and coastal New England. Areas inland will likely see mainly snow. The exact track of the system will determine how far inland the mixing line is pushed.
There remains sharp disagreements on exactly where the storm will track. The Euro has been more consistent with a more inland track, spreading mixed precipitation well inland while the GFS and CMC depict a flatter storm closer to the coast. The latter solutions would result in more widespread snowfall, but the storm would not be as strong. The ensembles generally remain colder than what operational models are depicting. Current trends point toward an initial burst of snow for everyone followed by mixing taking over from south to north.
Areas that do see all snow from this storm will have the chance to see a significant accumulation. This comes as the pattern will begin to shift from a more zonal flow to a more amplified one late this week and into the weekend. This would support a stronger and longer-duration storm than what New England has been seeing over the past week and a half under the less-impactful zonal flow. The storm would likely last from Saturday afternoon through all of Sunday.
Below: Current probability of impactful winter weather later Saturday into Sunday morning (1st image) and throughout Sunday (2nd image):
The storm will likely swing the door wide open for an Arctic blast early next week. This will occur regardless of exactly how this storm plays out. Much of next week will likely run cold with the beginning of the week very cold.
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