One More Damp Day Before New England Gets Another Break

New England has one more cool, cloudy and showery day to go before a brief break. Scattered showers will continue to swing through the region throughout the day as a warm front lifts through New England. This front will bring dew points up a notch, setting up a rather clammy day. As the cold front pushes through New England later this afternoon and evening, a line of thunderstorms may develop and push eastward.

Moisture will once again be on the rise heading into Tuesday, with precipitable water values (which measures the amount of water vapor in the atmosphere) highly elevated. Values will likely be in the 1.5-2 inch range for southern and central New England. This indicates a highly moisture-rich atmosphere that will be supportive of downpours and a few thunderstorms embedded within the showers. With that said, downpours will likely be brief and quite scattered around, so the flash flooding threat remains low. 

Late this afternoon, a line of broken thunderstorms will likely develop ahead of a cold front. These storms will likely enter westernmost New England late this afternoon or early this evening. Since this line is set to form after peak daytime heating, it will more than likely fall apart as it pushes eastward. The line will weaken after sunset with chances of evening storms gradually diminishing moving east of the Connecticut River. 

Below: HRRR showing potential weather this evening (1st image) and nearing midnight (2nd image):

There is a low risk for a few strong to severe storms within this line west of the Connecticut River. The line will be strongest in this area and some ingredients for severe weather will be in place. Moisture will be increasing within the warm sector of the storm. The incoming cold front will provide the lift. Effective shear is likely as well, which would help storms develop and strengthen. 

The big question will be instability. Areas west of the Connecticut River in southern New England could see some drier air move in, allowing for a few breaks of sun in the afternoon. Should this occur, CAPE values may build into the 500-1,000 joules/kilogram range, which would support a couple stronger storms. Severe storms remain a lower chance and only a couple isolated instances of strong storms is likely, should any be able to form at all. 

Generally speaking, surface ridging looks to be in control for much of the second half of the week. This will bring drier and warmer weather with more sunshine. This change in pace will be aided by a switch to a more westerly flow, allowing for warm, downsloping winds and dry air to enter New England. This will bring widespread 70s north to 80s south back to the region on Wednesday. On Thursday, a cold front will drop through New England with little fanfare. Dry air in the mid-levels with ridging aloft will greatly limit precipitation chances with this front. 

The northern third of New England will have the best chance at some showers. With continued (partial) sunshine and westerly winds, temperatures will remain up for most. The northern tier and high elevations will be a touch cooler with more clouds and an earlier arrival of the cold front.

Below: AIFS showing temperature departure from average Thursday afternoon:

Heading into the late week and weekend, that cold front looks to stall just south of New England. This will lead to increased precipitation chances, though forecast confidence is very low at the moment for Friday and Saturday. These days will see high pressure and low pressure facing off over New England. Guidance is still at odds on which one will generally win out. While low pressure tracks along the stalled front to the south, high pressure will build to the north and west. The main question will be how far south does the front get pushed and likewise how far south are showers suppressed. 

For this reason, the farther south you go in New England, the higher the shower chances are on Saturday with higher chances of the high pressure winning out farther to the north. Where exactly the line sets up between drier weather and high pressure and wetter weather and low pressure across New England remains to be seen. Either way, the weekend will be another cool one for New England. This coolness will come whether the low pressure brings clouds and showers or whether the high pressure brings a cooling northerly flow.