UPDATED 6:30pm | Evening updates are in bold.
A coastal storm will be moving over New England beginning late Monday night through Tuesday evening. The storm's center will pass near the 40/70 benchmark. The storm will rapidly strengthen as it passes New England. Explosive cyclogenesis is certainly possible. The storm's central pressure will likely be in the 970-980mb range.
The overall setup for the storm will involve a primary low tracking up the Appalachian Mountains and into the Mid-Atlantic early Tuesday morning. As it does so, a secondary low will form off the Mid-Atlantic coast and strengthen as the primary low weakens. This all supports a colder storm with mostly snow falling across New England.
ALERTS
TIMING
All of Monday during the day will be dry. It'll be another mild day, however, colder air will be filtering into the region by Monday evening. Precipitation will likely enter into southwest Connecticut by late Monday evening. Precipitation will likely start as a mix or rain in Connecticut, Rhode Island and southern Massachusetts. This should switch to a wet snow by the overnight hours.
Expected weather Monday night:
With a track near the 40/70 benchmark, the storm will be primarily snow. Areas that begin as a mix or rain should changeover rather quickly Tuesday morning. The one exception will be Cape Cod, where mixing will hold on the longest. Everyone else will likely be seeing snow a majority of the time.
By Tuesday morning, snow will likely have spread across all of southern New England as well as southern Vermont and New Hampshire. The storm will be moving rather quickly, so the snow shield will overspread New England quickly. There will likely be a sharp northern cutoff once north of Lake Winnipesaukee.
Expected weather Tuesday morning around sunrise:
The peak of the storm with the most intense snowfall rates will likely be sometime from mid-morning to early-afternoon. The storm will continue through the afternoon, but will gradually wind down in intensity from west to east. Accumulations should largely be done by Tuesday evening.
Expected weather Tuesday early afternoon:
SNOWFALL
The jackpot zone will likely see snowfall up to, or over, a foot as the storm strengthens rapidly. This jackpot zone will likely be set up in interior Massachusetts with an emphasis on the Worcester Hills and Berkshires. Where the heaviest snow bands set up will be dependent on the final track.
The most intense part of the storm could produce snowfall rates of 1-2 inches an hour, potentially going up to 3 inches an hour at times. From mid-morning through early afternoon, whiteout conditions will be possible across much of southern and central New England.
Heading southward into Connecticut, Rhode Island and the south shore of Massachusetts, amounts will likely be lower here as marginal temperatures and initial mixing eat away at some of the accumulation at the onset. There will likely be a situation where it's snowing, but it's not quite sticking at the beginning.
A big question will be how quickly can the storm overcome marginal air temperatures near the coast. When a storm strengthens quickly, it can generate its own cold air, which is a big reason this will be a mainly snow event despite no cold air in place at the start. We stated this morning that we would likely need to expand our 8-12 inch zone in all directions. We've done just that this evening. A 12-18 inch zone may be needed tomorrow morning, we haven't added one this evening as probabilities of at least 12 inches currently tops out at 50%.
Probability of at least 12 inches of snow by Wednesday morning:
Heading into northern New England, there will likely be a sharp cutoff from the steady snow to just some light snow showers. Exactly how far north the steady snow gets will be dependent on the final track.
The main bust potential with this storm will come from potential track issues. A more northerly track will lead to less snowfall in southern New England. Also, if the storm isn't able to strengthen as quickly as anticipated due to a lack of interaction with the northern stream, snowfall rates will not get as intense.
POWER OUTAGES
With marginal temperatures hovering around the freezing mark, this will likely be a heavy, wet snow for most. This is the kind of snow that sticks to everything. When you begin talking about the potential for 6-12 inches of this type of snow, some tree branches and power lines may come down.
At this point, we don't anticipate a widespread outage event, but scattered outages are becoming increasingly likely. Continued upward trends in snowfall would lead to a higher risk of increased outages. The threat of scattered power outages may need to be expanded further if snowfall trends higher. A period of high winds may cause some issues on Cape Cod and the Islands.
WIND
Widespread strong winds will not be a major concern with this storm. Gusts may reach 50+mph on Cape Cod for a couple hours on Tuesday. Elsewhere, gusts will remain below impactful levels. The only caveat is that heavy, wet snow sticking to the branches will only be stressed further by any gusts.
COASTAL FLOODING
The main threat of coastal flooding will be along the eastern Massachusetts coast through Portland, Maine. While astronomical high tides will be on the downward trend, they will still be high on Tuesday. Combine this with a 2-3 feet surge and widespread minor coastal flooding is likely. Pockets of moderate coastal flooding will be possible.
As usual, the extent of coastal flooding will come down to precise timing between when the maximum surge will be and high tide. The Tuesday afternoon high tide is the biggest concern. Beach erosion will be a large concern as New England's coast has taken a beating this winter.
Wind direction expected Tuesday afternoon:
