The general pattern across the United States that began this train of storms last week will remain in place for much of this week. This will continue to support storms being near New England every 2-3 days. This means that three storms will be passing the region over the next week. With that said, the pattern remains one that isn't favorable for all snow everywhere for the entire region and this pattern will begin to shift as the week progresses.
This pattern continues to involve a large ridge near Alaska. This opens the jet stream up to a mostly zonal flow across the United States. This flow occurs when the jet stream lays flatter across the country rather than having large troughs and ridges. This supports storm systems being pushed across the country at a quick clip. It also supports these storms not becoming overly powerful as they quickly slide across the country without getting hung up.
The next large-scale storm in this pattern will be passing well to New England's south tonight into Wednesday morning. This storm will bring several inches of snow to portions of the Mid-Atlantic today, with the northernmost bands maybe being able to scrape southernmost New England with an inch or two of snow tonight.
Helping to suppress this storm to the south will be a cold front dropping into New England later today. This front is poised to set off a line of scattered snow showers this afternoon across the northern tier. Snow showers will likely enter into northernmost areas by 1-2pm and push south and eastward through the afternoon. This line will dry up quickly as it moves south with southern and central New England likely not seeing anything.
Below: HRRR showing potential weather around mid-afternoon today:
There will be a chance for scattered snow squalls across northernmost areas this afternoon. Steep lapse rates will help set up sufficient instability to produce potentially heavy snow showers. With cold temperatures, a quick inch of snow is possible anywhere a squall sets up, along with reduced visibility and briefly strong winds.
The one big limiting factor for squalls will be rather weak forcing overall, but the cold front should provide the lift for snow showers to get going. Snow squall parameter values range from 1 to about 3 across much of the northern tier. Anything over 1 is supportive of at least scattered squalls. Values are highest across interior Maine.
Below: Snow squall parameter values this afternoon:
The next large-scale storm to move through New England will come Wednesday night to Thursday, bringing much more widespread precipitation than what's coming today. This storm will involve an area of low pressure moving to the north of New England with possible secondary low development off New England's coast. The strength and timing of the secondary low will be key when it comes to precipitation types with this system. Trends have continued toward a weaker secondary low (or even no development at all).
With a weak, late developing secondary low, this will allow the primary low, which will pass well inland (likely to New England's north and west), to drag its warm front across the region. This will introduce warmer air aloft from south to north Thursday morning across the region. With that said, the air mass will be cold enough to support all snow everywhere at the start of the event Wednesday night, prior to the front's arrival.
With cold air hanging around at the surface and warmer air working in aloft, it is a prime setup for a wintry mix to take over from south to north through Thursday morning. Both sleet and freezing rain will be possible during the changeover. With a weak secondary low, the warmer air aloft will have an easier time making it to the surface (especially across southern New England) to change the wintry mix over to plain rain.
There's high confidence in this storm starting off as a burst of snow for everyone. There's also decently high confidence in a gradual changeover to a mix from south to north as the event goes on Thursday morning. Where guidance begins to diverge is in the timing of the potential switch from mixing to plain rain, as well as how far north that mixing and rainfall gets. This has to do with how the secondary low is being handled.
Should the secondary low be able to develop quickly and become a bit stronger (some guidance is still holding onto this idea), more wintry precipitation may be able to hang on longer with a slower transition to a mix/plain rain. This would happen as the secondary low would help trap a shallow layer of cold air at the surface while the warmer air works into the region aloft. Again, trends are continuing down the road of a weaker secondary low, but this development will be something to watch as the storm actually gets underway.
Even with the trends toward a warmer solution, this will still likely be a mainly snow event across the northern tier of the region. These areas (northern Vermont, northern New Hampshire and particularly northern Maine) will have the best chance to see several inches of accumulation, possibly in the 3-6 inch range. Northernmost Maine could stand to see upwards of 6-10 inches. Southern and central New England will likely see around 1-3 inches with the initial burst Wednesday night. This is based on current trends, and with the complex nature of the storm, could stand to change.
Heading into the weekend, a potent system will likely eject out of the west and track near southern New England as it strengthens. Depending on the exact track, this storm will have the chance to produce a decent thump of snow for a portion of New England along with a potential switch to a wintry mix for southern and central areas.
There remains a large split in how this storm will unfold. Operational models have generally been pointing toward a milder solution as of late with more mixing and rainfall for southern and central New England. The GFS is currently running the coldest of the operational models while the Euro is running the warmest. As for ensembles, many of them are running cooler, so a trend toward a colder solution may come within the operational models, which occurred through last week with last weekend's storm, but only time will tell on whether that happens again or not.
Below: Current probability of impactful winter weather later Saturday into Sunday morning (1st image) and throughout Sunday (2nd image):
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.
Below: Flow pattern this weekend, showing a more amplified flow over the east:
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