New England's new-found active pattern will roll on right through Thanksgiving week with two systems moving through the region. The first will come Monday night through Tuesday and the second will come Thursday through Friday. The two storms will have very different setups from each other.
MONDAY NIGHT-TUESDAY
The setup for this system will involve a primary low pressure diving out of the Great Lakes to the north of New England with a surface low forming over New England. This will bring a period of rain showers to southern New England with the potential for some freezing rain and snow showers across the north.
This system will likely enter into western New England in the early morning hours Tuesday and spread precipitation west to east through the day Tuesday, reaching eastern Maine by the early afternoon. This storm will feature warm air advection, so low temperatures Monday night will likely be reached earlier in the night with rising temperatures after midnight. This will set up a situation with mixed precipitation.
GFS showing potential weather in the early afternoon Tuesday:
Precipitation type will be determined by how far temperatures at the surface can drop Monday night before beginning to rise again along with how quickly precipitation can begin to fall Tuesday morning. With warm air advecting into the region early in the morning with temperatures below freezing at the surface, it's a recipe for some freezing rain across interior northern New England.
Areas that can't drop below freezing prior to arrival (southern New England, coastal plain and maybe Champlain Valley, namely) will see a plain rain event from start to finish. The northern woods of New Hampshire and Maine may be able to see a period of snow. The strength and timing of the surface low will determine the extent of snowfall across Maine. An earlier development of the low with more time to strengthen would result in snowfall being pulled farther south in Maine. Maine's coastal plain is looking at a mainly rain event.
There will be modest moisture with the system and favorable dynamics for forcing precipitation. Despite this, total precipitation amounts continue to look to be on the lower end, mainly due to the storm's fast moving nature. As of now, it looks like a quarter to half inch of rain for southern New England and the lower elevations of northern New England.
Total ice accumulations across the higher elevations of northern New England appear to be very light, with no more than a tenth of an inch currently expected. The amount of ice will be determined by how quickly temperatures can rise above freezing and switch things over to plain rain. The far northern woods of New Hampshire and Maine could see a few inches of snow.
The quick-hitting nature of this system means it will be in and out within a day. The storm moves into western New England early in the morning and exits eastern Maine by Wednesday morning. Much of the daylight hours Tuesday will be wet for most of New England, though the western half should begin to dry out by the second half of the day.
GFS showing potential weather Tuesday evening:
THURSDAY-FRIDAY
The preceding storm earlier in the week will set up colder air for the rest of week, which leads into the second storm system of the week. This storm will be forming, but its track, unfortunately, remains up in the air. The system will involve a southern stream piece of energy moving across the country during the week and a northern stream piece of energy diving into the Great Lakes. The level of interaction between these two will determine much about New England's impacts.
First and foremost, recent trends over the last 24 hours or so have pushed the storm back to an earlier time frame. This means the storm could enter New England during the daylight hours of Thanksgiving. Consistency on where the storm will track has not yet occurred among individual model runs or among the different models.
There remain two basic outcomes being shown. One outcome involves the main storm system tracking near or inside the benchmark while interacting with the northern stream energy. This would bring widespread storm impacts to New England with rain along the coast plain of southern New England and widespread winter weather across interior New England. The closer to land the storm tracks in this outcome, the farther north and inland rain would be pushed over snowfall.
Below: Euro 06z (1st image) and CMC 00z (2nd image) model runs from Sunday morning, favoring the scenario above. These runs show potential weather Thanksgiving evening:
The second outcome revolves around less interaction with the northern stream system. This would help keep the system well to the south of New England. This would favor a weaker and faster moving system. This would result in a colder storm for all of New England, but with much lighter precipitation rates. The storm would also be much weaker in this outcome.
GFS (1st image) and EC-AIFS (2nd image) model runs from Sunday morning, favoring a scenario with less interaction and therefore a much farther south storm:
As of right now, overall guidance seems to be favoring the first scenario with a track inside the benchmark. With that said, there's still way too much of a spread to rule anything out at this time. If the storm tracks over southern New England or Cape Cod, it would result in a mainly rain event for southern New England and the northern New England coastal plain with impactful snow across the interior of northern New England and possibly the Berkshires.
Below: Current weather map from the Weather Prediction Center for Friday morning, showing the system tracking over Cape Cod:
Another big factor to keep in mind is the potential lack of deep cold air. While colder air will filter into New England after the early seek storm, temperatures are still looking marginal with this system. Without a deep, cold high pressure system to New England's north to funnel polar or Arctic air into New England, a deep layer of very cold air is unlikely. Also, ocean temperatures remain relatively mild here very early in the winter season.
A mild northeast flow off the ocean will make frozen precipitation difficult, especially near the coastal plain. This lack of deep cold air could result in a rainier storm regardless of the final track, which will be something to watch. This would be especially true for southern New England and their lower elevations.
Potential flow Thursday evening. This would be a milder flow off the ocean:
Timing has again shifted to an earlier start time with Thursday afternoon to Friday afternoon when the bulk of the storm may move through. There is a spread on when the storm moves through, so nothing is locked in with timing. The timing will also play a role in precipitation type. If the bulk of the storm moves through overnight, more widespread wintry precipitation will be possible. We realize it can be frustrating trying to plan around this potential storm and we can't wait for more clarity to come into view as well.
No matter where the storm ultimately tracks near New England, it will likely wrap up to the north of New England, toward the St. Lawrence Valley/Quebec next weekend, allowing for wrap-around precipitation into the weekend. What is far more certain than the storm's impacts is the cold air that will wrap into New England after it pulls away.
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