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Prolonged Stretch of Rainy Weather Incoming to New England

A cold front associated with an area of low pressure moving well to New England's north will very slowly move into New England over the next 24 hours. At the same time, a coastal low pressure system will move up offshore. The timing and interaction between these two features will determine how much rain is able to fall from tonight through Friday.



Friday night will likely see some backside snow develop across eastern Maine. This is a long-duration system that will begin today for New England and won't shut down until Friday night.


NAM showing potential weather from 8pm tonight through Friday. Remember this is just one model's interpretation:


TONIGHT


After another day of sporadic showers, steadier rain will begin to become more widespread starting tonight as the area of low pressure begins working up the coast. This system will be moisture-rich as it transports sub-tropical moisture into New England amid a strong jet. This will allow rainfall rates to become steadier as the night goes on for eastern New England.


Expected weather Wednesday night:




THURSDAY


The day Thursday will be a washout for most with a steady rain continuing all day long. The heaviest of the rain will occur across areas closest to the coast. The rain will become lighter and showers will be less numerous as you work north and west until there are just a few scattered showers in the Champlain Valley.


Expected weather Thursday morning:


There remains uncertainty in where exactly the heaviest rain will set up. This is due to the fact that the slow-moving cold front will be progressing east during the day Thursday. As of now, it does look like this front will be able to push the coastal system far enough offshore to keep the heaviest rain over coastal areas of New England.


If this cold front fails to get moving along in time, it would allow the coastal system to get closer to New England, pushing the axis of heaviest rain farther inland while areas closer to the coast get into a dry slot, which would reduce rainfall there. Either way, this is a very moisture-rich system that will be bringing a large portion of New England a soaking.


There may be a lull in the rainfall around midday for southern New England before filling back in later in the afternoon and heading for the evening.


Expected weather Thursday afternoon:


THURSDAY NIGHT


Rain will continue across eastern New England into Thursday night as the frontal system very slowly chugs along. The axis of steady rain will continue to very slowly push eastward as we head toward Friday morning. Eastern Maine may see their heaviest precipitation Thursday night into Friday.



Expected weather early Friday morning:



FRIDAY


Friday will likely start off as more of the same for eastern New England as waves of rain continue to move along the frontal boundary. The axis of rainfall will continue to slowly move eastward as Friday morning goes on. Higher elevations of New Hampshire and Maine will try to flip to snow on Friday as the coastal low begins to deepen and eventually pull away.


Expected weather Friday morning:


Clearing will occur slowly from west to east Friday afternoon. Much of New England will be done with the steady rain by Friday afternoon, though scattered showers may linger for much of the day, especially for the Massachusetts South shore and Cape Cod. Winds will become gusty on the backside of the system.


FRIDAY NIGHT


At this point, the big question will be how quickly the rain can transition to snow for the higher elevations of New Hampshire and northern Maine. This will come down to the amount of cold air filtering into the backside of the system as well as how strong the system is able to get as it lifts into Nova Scotia Friday night. The other part of this will be how much moisture lingers over the area at this point.


It is becoming increasingly likely that rain will transition to snow from west to east at the tail end of the system for Maine. There remains a spread in how quickly this is able to happen. As of now, we're leaning toward the lower end of the spectrum of snowfall with no more than a few inches in northern Maine.


Two models showing potential weather around 8pm Friday. The first is NAM, showing a stronger system and more widespread snow amid a quicker transition. The second is the CMC, showing a weaker system and not as much snowfall:


This system will finally kick away by Saturday morning, although some snow showers may be lingering across eastern Maine still. Easter weekend is looking mainly dry and quiet with seasonable temperatures, though Saturday will likely continue to be gusty.



RAINFALL/FLOODING


When all is said and done by Friday night, much of eastern New England will likely have seen 1-3 inches of rain, with most falling closer to the coast. Amounts will likely drop off steadily and quickly heading farther west, especially when getting west of the Connecticut River. There is a chance for amounts to possibly reach over three inches across downeast Maine. Exactly where the rainfall drops off inland will be determined by the position of the cold front.



This rain will be falling over the course of 36+ hours, so flash flooding is not much of a concern. While the prolonged nature of the event does help limit flooding, rivers are running high and soils are saturated. Groundwater is also running high across southern New England. Overall, minor flooding issues may come to be in southern New England, but widespread issues are unlikely. Some rivers will likely rise once again.


Northern New England will see the added water of snowmelt from the widespread 1 to nearly 3 of snow that fell over the weekend. As the snow ripens from the above freezing weather, snowmelt will accelerate. This will be exasperated by the rainfall coming Thursday and Friday. The snow is unlikely to completely melt out across the north, but areas along Maine's coastal plain and central New England will likely see all snow gone by Friday.


The amount of water estimated to be in the snowpack (in inches):


Overall, northern New England may see some standing water issues as well as river rises reaching minor flood stage. Basement flooding could also be an issue for those in eastern Maine as well as eastern Massachusetts.




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