Stalled Front, Cutoff Low to Make New England's Weather Tricky in Coming Days

New England's next frontal system will be entering the picture just in time for this weekend. After another very quiet and seasonable day on Thursday, a warm front will lift through New England through the day on Friday. The forcing from the warm air advection will allow for a period of showers to break out from southwest to northeast overnight tonight through Friday morning.

Below: HRRR showing potential weather during the pre-dawn hours Friday:

For the daytime Friday, much of New England will be within the system's warm sector. Once the warm front passes, the shield of rain will move on and drier air will work in behind it. 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.

As usual in this setup, there is a question as to how much clearing of the clouds will occur. As of now, it looks 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.

The general trend has been for the main round of rain to move through New England from southwest to northeast from Saturday afternoon through Sunday morning. The first half of Saturday has been trending drier. 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.

Below: Euro showing potential weather Saturday late-afternoon or early evening:

A widespread half inch to inch of rain is likely from Friday through Sunday morning. 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 and where will see a near washout. As of now, the chances for more rain will be across northern and western New England with areas south of the Mass Pike with the best chance to see only spottier activity.

Sunday remains on the uncertain side, but current trends are heading toward a Sunday similar to this past Sunday with cooler temps, plenty of clouds and scattered showers continuing as the cold front very slowly pushes 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.

Early next week remains under a cloud of uncertainty as well. 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.

Below: Upper-level flow pattern early next week:

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. Possibilities in New England range from the low being far enough away to allow for ridging and dry weather to the ribbon of moisture leading to a prolonged period of soggy weather.