A frontal system will traverse New England today, with a warm front lifting into southern New England by this afternoon and a cold front crossing later in the day. These fronts will create an unsettled and a bit of a stormy day. Once the cold front crosses, it will stall to the south of New England, keeping the clouds and showers around for the rest of the week.
The first batch of showers is working through western New England right now and will continue to push eastward through the morning. With plenty of moisture in place ahead of the front, there will be some heavier downpours and rumbles of thunder embedded within the showers. This round of wet weather will clear New England east of Maine by early this afternoon.
HRRR showing expected weather later this morning:
Once the warm front crosses southern New England, the area will get into a dry slot. This slot will not be completely dry, however, as isolated showers will continue through the afternoon. Maine will see their most widespread rain activity in the afternoon as the system continues to push eastward.
By mid-afternoon, some thunderstorms will try to develop across interior portions of southern and central New England. There will be factors working for and against thunderstorm development. Thunderstorms have four main ingredients needed to form: shear, lift, instability and moisture. There will be ample shear and lift. Instability will depend upon the amount of sun that can break through the clouds in the afternoon. If the sun can break out, chances for storms will be higher.
As for moisture, trends have been toward a drier environment. While a drier environment may lead to more breaks in the sun, if it is too dry, storms will have a difficult time developing and holding together. With all that said, storm chances this afternoon will be more isolated, with more areas likely not seeing a storm than areas that will see a storm.
HRRR showing expected weather around mid-afternoon, showing the widespread rain having moved into Maine while thunderstorms try to develop in southern New England:
Should storms be able to develop, a couple could become strong to severe. This comes as CAPE (convective available potential energy) values head for 500 to potentially over 1,000 joules/kilogram. A value of several hundred supports thunderstorms while getting over 1,000 can support strong to severe storms.
Euro showing CAPE values around mid-afternoon today:
The overall threat of severe storms is low, and a vast majority of the region will not see a strong storm, but one or two isolated storms could produce gusty winds and hail. This threat is greatest over interior southern New England. The Storm Prediction Center does have all of southern and central New England in the "marginal" category (level 1 of 5) for severe thunderstorms, but the threat is very low heading closer to the coast.
After Wednesday, the system's cold front will stall to the south of the region, leading to a rather prolonged period of cloudy, showery weather. This happens every single spring at some point, and this year is no exception. An area of low pressure will develop and move along the stalled front Thursday evening. This will bring the next round of showers through Thursday evening. Much of Thursday will be dry, but some showers will likely pop up, especially toward the evening.
GFS showing expected weather Thursday evening:
The rather dreary weather hangs around for Friday and into Saturday, though the moisture with this system has trended farther south, pushing the most widespread precipitation farther south with it. With that said, there is still a spread and some uncertainty as to the extent of showers on Friday. No matter what, showers would be lighter and unimpactful. The question remains as to how much of the day will be wet vs dry. The idea is that clouds and periodic showers will continue through Saturday morning.
CMC showing potential weather Friday afternoon:
The stalled front, and associated low are looking to move well east of New England by Saturday afternoon, however, the region will likely remain under broad cyclonic flow. This would lead to plenty of clouds hanging around (though not totally overcast) and spot showers. Mother's Day may see another low traverse New England, bringing another round of showers.
Weather map for Sunday morning:
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