An Alberta Clipper system will be moving just to the north of the Great Lakes today as it zips across southern Canada, eventually landing in New England for tonight and Thursday. These kinds of systems tend to bring a widespread few inches of snow to New England, and this one is no exception.
This one will become rather potent by Alberta Clipper standards. The strengthening system will pass to the north of New England with a secondary low possibly forming off the coast, along the system's triple point (where a warm, cold and occluded front meet). This will allow for a decent thump of snow across interior Maine with a secondary jackpot zone over the southern Green Mountains.
ALERTS
TIMING
Scattered snow showers will likely break out across western New England by mid-afternoon today. These snow showers will steadily push eastward through the rest of the afternoon and into the evening. These snow showers will likely be on the lighter side and more scattered around for a while before filling in and picking up intensity.
Below: HRRR showing potential weather this evening:
During the overnight hours is when precipitation will really fill in and become steadier. This will come as the main clipper system approaches New England's north while the secondary low forms over New England, which will strengthen, allowing for more widespread precipitation and heavier rates. By the pre-dawn hours, widespread interior snow with rain at the coast will be falling.
Below: HRRR showing potential weather just after midnight tonight:
The steadiest of the rain and snow will taper off from west to east through Thursday morning as the storm complex begins to lift northeast. Precipitation will revert back to more scattered in nature rather than widespread. By the early afternoon, a strong cold front will dive through New England, allowing for scattered snow squalls to develop. This threat will be greatest across southern and central New England. In the afternoon, snow showers will generally be more numerous across the mountains.
Below: HRRR showing potential weather around mid-morning Thursday (1st image) and early Thursday afternoon (2nd image):
SNOWFALL
While this certainly won't be nor'easter/blizzard level snowfall, it will be a decent thump of snow by clipper standards. Northern Maine will stand to receive the most as the storm will be strongest over the state. A swath of 6-10" is likely across interior Maine, especially over the highlands.
For the rest of New England, the higher snowfall amounts will favor higher terrain with the Greens, Whites and Berkshires seeing more than the lower elevations in the area. The general consensus is for most of New England to see a few inches of snow, with 3-6" readings likely very common by midday Thursday.
A colder air mass has been in place for New England over the past few days, which will allow most of the region to see all snow. With that said, without a reinforcing shot of cold air from the north, the coastal plain will see mixing and rainfall as the mild ocean air over spreads the area. The up to 1" zone below extends all the way to Boston to account for the potential of snow squalls in the afternoon. A general 1-3" is expected for the coastal plain.
While confidence is fairly high in snowfall amounts well inland, there is a strip of higher uncertainty just inland from the coast. As stated before, a cold air mass is in place, but a southerly flow will increase as the storm strengthens, and without a cold high pressure to the north, it may be difficult for the surface cold air to remain in place, allowing for mixing and rainfall to push farther inland.
How far inland is the big question. At this point, the area with the greatest uncertainty is about 25-35 miles from the coast. This uncertainty is highest from southern New Hampshire through central Maine. Confidence is higher that the southern New England coastal plain will be all rain until scattered snow squalls and showers move through Thursday afternoon. That southerly flow will allow for a warming trend overnight. Farther inland than that and confidence increases significantly that this will be an all snow event.
Below: Probability of snow accumulating 2 inches by Thursday evening. Note the sharp cutoff heading to the coast. Probabilities go from 60-70% around Manchester and Augusta to 10-20% very close to the coast:
The stronger the storm gets, the more moisture will get pulled into the system. This would allow for heavier snowfall rates across the interior. This increased moisture would also draw more mild air farther north. So, while a stronger storm would result in heavier snowfall, it would also push the rain/snow line farther north, limiting total snowfall farther inland.
This increased southerly flow will inject more moisture into the system, which will allow for a period of heavier snowfall rates. The rates could reach 1+" an hour for a time just inland from the rain/snow line. The quick moving nature of the system will preclude a major snowfall for most.
Below: Flow pattern around midnight:
This will be a light and fluffy snow across the interior with a wetter and heavier snow closer to the coast. Impacts from the wet and heavy snow will be limited as the coastal plain will only a couple inches anyway. The fluffy snow may reach ratios as high as 20:1, which will accumulate quicker and will likely blow around easier.
WIND
Winds will pick up tonight and remain elevated through Friday. The highest of the winds will occur as the system approaches tonight and as it departs Thursday afternoon. Widespread gusts of 25-40mph. The southern New England coast could see some gusts to 50mph. Friday will remain windy with gusts of 25-35mph likely region-wide.
This wind will help usher in a very cold air mass for the weekend, with widespread 20s to low 30s for highs and teens overnight. Blustery conditions will create a wind chill factor as well, making it feel very cold. Areas that see several inches of light and fluffy snow could see impacts from blowing and drifting snow on Friday.
Below: GFS showing potential wind gusts around midday Friday:
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