Rounds of Showers and Storms to Move Through New England Amid Stalled Front

For the daytime Friday, much of New England will be within a frontal system's warm sector as a warm front steadily moves through the region. This will set up a standard "warm sector afternoon" with mild temperatures, increasing dew points and the potential for scattered showers and thunderstorms. With the dry air and weak forcing, the afternoon does appear to be mostly dry, but some instability will build, which will likely result in at least a few pop-up showers/storms throughout the day.

Below: FV3 showing potential weather later this afternoon:

As usual in this setup, there is a question as to how much clearing of the clouds will occur. With that said, it does look like clouds will steadily break from south to north through the morning and into the afternoon. The breaks in the clouds will allow more instability to build and more pop-up activity in the afternoon. Clouds scouring out will also allow rapid warming with widespread highs in the 60s north and 70s south. Much of Maine will be cooler as the warm front and clouds take the longest to move through the state.

The system’s cold front will move into New England later Friday, but likely get hung up and stall out right across the region.This front will provide the basis for multiple rounds of showers and thunderstorms through the weekend as waves of low pressure ride up along it. Showers will be most numerous near the boundary, which currently looks to stall right across interior New England.

Trends have continued to point toward the main round of precipitation moving through New England later in the afternoon through the overnight hours into Sunday morning. The first half of Saturday continues to look mostly dry. By the afternoon, the ingredients will begin to come together for the development of scattered thunderstorms, mostly across southern and central New England. Scattered storms will likely begin to pop up around early to mid-afternoon. There remains a chance for a steadier shield of rain across northern New England as the cold front moves in.

Below: FV3 showing potential weather around mid-afternoon Saturday:

Heading later into Saturday afternoon and evening (as well as the overnight hours), a wave of low pressure will ride along the cold front, allowing for more widespread rain chances. Exactly when the main round of rain moves through remains a point of contention among guidance. This will come down to the timing of the wave of low pressure riding along the stalled out front. Guidance is also struggling to agree on just how widespread rainfall will be.

The ingredients for strong to severe storms will generally be in place, though not strong enough for widespread severe weather. The stalled cold front will provide the lift, shear and forcing for scattered storms to develop. Areas that remain south of the cold front will see somewhat higher dew points, allowing for moisture to build for storms to feed off. The main limiting factor will be instability. While some instability will build with CAPE values likely reaching at least 500 j/kg, this is unlikely to be enough over a wide area to produce widespread strong to severe storms.

A widespread half inch to inch or more of rain is likely through Sunday. Amounts will taper off moving south and east of the stalled front. The rainfall will be most persistent along and north of the stalled cold front with more sporadic activity to the south of it, so where the front ends up stalling will determine where in New England only sees a few scattered showers/storms and where will see more persistent rain. As of now, the chances for more rain will be across northern and western New England.

Sunday remains on the uncertain side, but trends are heading toward a wetter day Sunday as the cold front continues to very slowly push through the region. As of now, it looks like Sunday morning will be the wettest with potentially some improvement in the afternoon. Whether or not this happens will all come down to the evolution and position of the front. Some areas will likely see improvement while others get stuck with persistent showers all day.

RGEM showing potential weather Sunday morning:

Early next week, an Omega Block type pattern will set up across the United States with a ridge of high pressure over the central Plains and cutoff lows over the southwest and northeast United States. The issue for New England will be the placement of the low over the northeast. Guidance shows the low ranging from offshore to as far south and west as the Ohio or Tennessee Valley. Current trends are heading in a more unsettled and wet direction for Monday to Wednesday for New England.

Regardless of where the cutoff low sets up, a more prolonged period of an onshore flow will develop for much of next week, leading to cooler temperatures, especially along the coastal plain. A ribbon of deeper moisture and persistent showers will likely set up across the eastern United States, the question is exactly where this will occur. Again, trends are pointing toward wetter weather for New England.