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Soaking Rainstorm Incoming to New England: Impacts, Timing

As the main system (from the southern stream) works up the coast in the afternoon, a frontal boundary (from the northern stream) will be working into New England. By Wednesday evening, the systems will begin to converge, which will enhance rainfall rates in areas that are still ahead of the front. There will also be a stronger low-level jet, which will help transport moist air from the south into New England. This will lead to a soaking rain.



ALERTS



TIMING


Moisture from the slow loving cold front will enter into northern areas by this afternoon. This will result in a steady rain, but not soaking, for northern Vermont and New Hampshire. At the same time, rain from the southern system will push into Connecticut. Areas in between will remain mainly dry and mild for much of the afternoon.


Expected weather around mid-afternoon:


By Wednesday evening, convergence between the slow-moving front and the southern storm system will begin. This will begin to enhance rainfall as well as fill in the gap between the front and the system.


Expected weather Wednesday evening:


Moderate to at times heavy rainfall rates will continue throughout Wednesday night into Thursday morning. Drier air will be working into the system behind the front, so the heaviest rain will occur in areas that are still ahead of the front (i.e. Eastern Massachusetts, Rhode Island and southern New Hampshire). Northern Maine and New Hampshire will likely see a switch to snow as cold air continues to filter in behind the front.



Expected weather around midnight:


The heaviest of the rain should begin to wind down by Thursday morning, however, Thursday will remain cloudy, damp and raw with rain showers lingering through the afternoon. Snow showers will likely continue across eastern Maine Thursday afternoon. Precipitation will come to an end from west to east.


Expected weather around noon Thursday:


RAINFALL/FLOODING


A very moisture-rich atmosphere, a converging front and efficient rain-making will lead to a widespread soaking rain across southern and central New England. A widespread 1-3 inches of rain is likely. The axis of heaviest rain continues to look like it will be centered over the Massachusetts South Shore and Rhode Island. These areas stand the best chance at seeing three inches with localized amounts up to four inches.


Amounts will generally taper off as you head north and west in New England, but up to an inch is still possible for all except northern Maine, where a changeover to snow is expected.



Combine all this rain with the rain that fell this past weekend and the rain from yesterday, and there is a chance for minor river flooding with the possibility of moderate flooding, mainly across southern Massachusetts, Rhode Island and Connecticut. It should be noted that the Pawcatuck River is already at minor flood stage and is currently under a flood warning. The Pawtuxet River and Wood River in Rhode Island are currently forecast to reach moderate flood stage.


Rivers in northern New England and western areas of southern New England will likely see swelling, but most are expected to stay within their banks. The mountains will not see as much rain, but will have the added water from continued snowmelt.


Poor drainage/urban flooding is also possible across southern and central New England. The Providence Metro area may be in the center of the heaviest rainfall. Should the city pick up four inches of rain, it could create impacts similar to what the city saw in mid-December.



This rain will fall over a 12-18 hour period, so flash flooding is not an overly high concern. The threshold for flash flooding to occur in southern New England is around two inches in an hour. Rainfall rates likely won't get that heavy, but urban flooding remains a possibility.



SNOWFALL


As stated earlier, colder air will filter into northern areas as the frontal boundary pushes through the area. This will lead to a changeover to a mix and snow for interior Maine and possibly the White Mountains. Snowfall will generally be light, with areas of northern and eastern Maine away from the coast seeing up to three inches with locally higher amounts in the Maine Highlands.



There is decent bust potential with snowfall as there remains some questions as to how far south and how quickly the transition from rain to snow occurs. Some models may be overdone with the speed of the transition, although it's hard to bring up bust potential when we're only talking about a few inches to begin with.


THE NEXT STORM


New England will get another brief break from storms on Friday and Saturday. Models are starting to hone in on this storm coming through Saturday night and lasting through Sunday. Trends continue to point toward a mainly rain event in southern New England with elevation-based snow in northern New England.


The storm will involve the usual: a primary low tracking to the north of New England with a secondary low forming near southern New England. As always with this setup, the track and intensity of this secondary southern low will play a large role in exactly where snowfall sets up. Right now, trends have the secondary low taking a more inland track.



This storm should have ample moisture to work with, so moderate to heavy rainfall rates will once again be possible in southern New England. This could also produce heavier snowfall rates in the higher elevations, with several inches possible. Temperatures will likely be marginal, which will make precipitation types trickier in the foothill and mountains. Being several days out, we need to continue watching the trends, especially where that secondary low tracks.


Sunday is also the day when March's King Tide will take place. This will introduce the possibility of coastal flooding with this system. While the current doesn't really favor a notable coastal flooding event, with the King Tide, it won't take much to push levels into at least minor flood stage.


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