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Spring Nor'Easter Incoming with Snow, Rain, Wind: Impacts, Timing

New England's potent spring storm remains on track this morning as the primary low cuts off and sits near Michigan. Throughout today, this low will spawn a secondary low across the Mid-Atlantic. This low will form into a coastal storm and strengthen as it slowly moves over Cape Cod and into the Gulf of Maine.



ALERTS



TIMING


The initial shield of precipitation will arrive in New England this morning. This shield will work generally northeast as the day goes on. Many areas during the day today will begin as rain or a rain/snow mix. Precipitation for much of today during the daylight hours will generally be on the lighter side.


Expected weather around midday:


Heading into Wednesday evening, rain and snow showers will fill in, become steadier and gradually move northeastward into the northern tier and Maine. At this point, there will likely be snow falling across the Green and White Mountains, sleet across southernmost New Hampshire and northern Massachusetts with plain rain, possibly mixing with sleet across the lower elevations of southern New England.



Throughout Wednesday night, the rain/snow will likely gradually drop southward and from higher elevations to lower elevations. By Wednesday night, the secondary low will have become the primary low and will be strengthening. This will allow snowfall rates of 1-2 inches an hour where snow is falling. Where rain is falling, this will allow for periods of moderate to heavy rainfall. Wednesday night will be the bulk of the storm.


Expected weather Wednesday evening (1st image) and early Thursday morning (2nd image):


As the low continues its slow crawl eastward, snow and rain showers will continue through Thursday. Both snowfall and rainfall rates will likely begin to ease up, but accumulations will still continue. The storm has been taking a northward trend as of late, this may allow a dry slot to get into southern and central New England for the afternoon. This would lead to very light snowfall and rainfall rates in these areas on Thursday. How far north a potential dry slot gets will be dependent on the final track.


Expected weather around midday Thursday:


Rain and snow showers will likely persist through Thursday night as the low meanders around in the Gulf of Maine. The snow showers will generally become lighter and more scattered as Friday goes on, with the most activity by Friday afternoon limited to the Green and White Mountains as well as Maine.


Expected weather around mid-morning Friday:


SNOWFALL


As mentioned in the "timing" section, intense snowfall rates of 1-2 inches an hour will be possible Wednesday night from the foothills of northern New England through the mountains. While there is no cold air for the system ahead of it, the storm will strengthen in the Gulf of Maine, allowing the storm to undergo dynamic cooling, which is a process that essentially allows the storm to create its own cold air. This occurs during heavy precipitation, which is expected Wednesday night.


A majority of the accumulations will likely occur overnight Wednesday into Thursday morning. This is when the heaviest snowfall rates are expected for New Hampshire and Maine. This will aid in the higher snowfall totals occurring as daytime accumulations can be hard to come by with the strong sun angle. At Night, this feature is naturally lost.



With that said, the jackpot zone with this storm continues to look like it will be across the White and Maine mountains, with the border between New Hampshire and Maine, along with northern York County seeing the most. A wide swath of a foot or more of snow is looking likely in these areas.



Snow consistency will start off very wet and heavy for most, but snow may become drier as the night goes on for interior areas. This would help snow loads on trees, but may also introduce whiteout to even blizzard conditions across the interior amid gusty winds. Snow will likely stay the wet and heavy variety closer to the coast of northern New England.


There remains the potential for a sharp cutoff in snow totals across southern New Hampshire. Higher amounts trended a bit farther south during the day yesterday, as seen in winter alerts getting extended southward into Rockingham and northern Worcester Counties.


Probability of at least 4 inches of snow from Wednesday night to Thursday night, showing probabilities drop from near 90% near Manchester to 40% or less near the coast and into Essex County:


Southern New Hampshire and northeast Massachusetts remain the areas of greatest uncertainty. Where this sharp cutoff sets will be crucial. As of now, it does look like mixing and rain will cut down on totals across northern Massachusetts and the New Hampshire seacoast.


Southern New England's snow will likely be highly elevation based with the northern Berkshires and northern Worcester Hills seeing the most snow, which will still be far less than what is seen in northern New England. There is the potential for the northern Worcester Hills to overachieve and pick up 6+ inches.


Bust potential comes from the fact that it is now April. There are a plethora of things working against snowfall including the potential for sleet (the biggest factor; more sleet=lower accumulations), low snow ratios, warm ground conditions and a strengthening sun angle. At this point, heavy snowfall rates do look to overcome much of this, but there are limiting factors that could bust snowfall amounts. The area with the greatest potential to underachieve will be the New Hampshire Lakes Region.


RAINFALL


This storm will be moisture-loaded. While this moisture is wrung out as snow in the north, it will be wrung out as a soaking rain for much of southern New England. A widespread 1-2 inches of rain is likely across all of southern New England. With this rain expected to fall over the course of 24+ hours, flash flooding is not much of a concern.


Flood watches have been issued for the Pawtuxet, Pawcatuck, Wood, Charles and Taunton Rivers in Rhode Island and Massachusetts. These rivers will likely reach minor flood stage with low-end moderate flood stage possible, mainly for the Pawtuxet and Wood Rivers.


Current flood watches:


WIND


With a strengthening storm passing into the Gulf of Maine, winds will become gusty. Winds will pick up as Wednesday goes on and likely peak overnight Wednesday into Thursday morning for most. Winds will remain gusty all day Thursday. A low-level jet with winds of 70-90mph will cross southern and central New England. As always, the question becomes how much of this can reach the ground?



Just about all of New England will have a chance to see at least 40mph gusts with the coast seeing gusts up to 50mph with some gusts over 50mph. Some of the higher elevations of southern New England could see some gusts over 50mph.



A downslope wind event is expected in the Berkshires and along the spine of the Green Mountains. A narrow corridor of 60+mph gusts are possible in these areas as a strong low-level jet looks to develop over this area overnight Wednesday to Thursday. High wind watches are in effect for these areas. These winds will likely cause whiteout conditions at times.


850mb (about 4,700 feet above sea level) winds early Thursday. You can see the core of the strongest winds over the Green Mountains, western New Hampshire, higher elevations of southern New England and near the coast:


POWER OUTAGES


Power outages will likely be a big issue with this storm. Snow will be of a heavier and wetter variety for most. This snow will stick to the trees and likely cause broken branches and fallen wires. The one piece of good news here is that areas in the mountains, where the most snow is expected, will likely see a drier snow develop Wednesday night. Still, outages are likely. The gusty winds will only exacerbate the conditions, especially in the Green Mountains, where fluffier snow is expected.


Overall, the extent of power outages is a tricky call, mainly because of snow ratios. Areas that see the most snow may see a drier snow, leading to less outage problems in areas that see less snow, but a heavier, wetter snow. Snow ratios will also likely change during the event, with heavy, wet snow at the start and gradually becoming drier as Wednesday night goes on from north to south. Wind will be the primary cause of any outages in the Green Mountains and along the southern New England coast.



COASTAL FLOODING


Eastern Massachusetts will face the highest coastal flooding threat. A prolonged period of easterly winds and building waves in the Gulf of Maine will likely result in widespread minor coastal flooding with some pockets of moderate flooding possible. This comes amid a general 2 to 3 foot surge. New England's south coast will also face a coastal flooding threat, but there remains considerable uncertainty in just how extensive it will be.


Minor coastal flooding and moderate splash over will be possible across the entire New England coastline. Tides are not astronomically high, which will help the situation. Generally, the coastal flood threat lessens as you move farther north in New England. Coastal flood watches extend from New England's south coast through Cumberland County, Maine.


Wind direction and speed around the Thursday morning high tide:


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