New England's weather pattern slowly evolves over the next few days

New England's weather pattern will slowly be evolving over the next few days. For much of this past week, New England's basic weather setup has involved an expansive upper level low hanging around eastern Canada with high pressure at the surface. This has led to unsettled weather at times, but also long bouts of very nice weather. Through this weekend, this rather stagnant setup will be changing.

There are four main weather features around the northeast, all of which are slow-moving, so the evolution of the pattern will be very gradual through the middle of next week. These four features are an expansive upper-level low over the Canadian Maritimes (which has been responsible for rotating weak disturbances into New England this week), surface high pressure (responsible for the longer bouts of pleasant weather), a frontal system to the west and Hurricane Ernesto well offshore.

Photo byNew England Storm Center

For Saturday, this setup will lead to most of New England remaining dry, albeit with a lot of cloud cover. The exception will be far western New England, where isolated showers could pop up. Scattered showers will continue to pinwheel around the frontal system to the west, but the log jam of features to the east will prevent much progress into New England. In addition, the high pressure remains generally in control, keeping drier air over much of New England.

HRRR showing potential weather Saturday mid-afternoon:

Photo byHRRR/Tropical Tidbits

Heading into Sunday, the high pressure to the east of New England will begin to give way to the low pressure to the west. This will gradually increase shower chances from west to east starting tonight and heading into the day Sunday. Still, the day will not be washed out and there will be more dry times than wet times.

HRRR showing potential weather Sunday afternoon:

Photo byHRRR/Tropical Tidbits

After this weekend is when the log jam preventing the frontal system from making eastward progress clears, allowing the system to move through New England Monday into Tuesday. This time period is when New England will see the most widespread, steady rain from the system. Much of Monday has the potential to be washed out as the system interacts with an increasingly moisture-rich atmosphere over New England.

Photo byNew England Storm Center

Forcing from the frontal system combined with the increasing moisture in the atmosphere will allow for a period of steadier rain. Within this rain, enough instability may build to allow for some rumbles of thunder. The highest rainfall amounts through Tuesday morning will be centered over western New England with amounts gradually dropping heading east. A widespread quarter inch to inch and a half of rain is possible, with the lower amounts near the coast and the higher amounts over western New England.

Weather Prediction Center forecast rainfall through Tuesday morning:

Photo byWeather Prediction Center

The front will clear the region by Tuesday. This will usher in a fall-like air mass with cool temperatures and no humidity. Highs on Tuesday may struggle to get out of the 60s for most of the region. Showers may linger on Tuesday depending on how far offshore the cold front manages to get.

For the rest of next week, high pressure looks to gradually build back in as the low pressure continues to pull away. Temperatures will likely begin to climb after Tuesday, but this will be gradual and temperatures remain below average for much of next week before getting back to seasonable (mainly in the low 80s) by late in the week. This will depend on the timing of the departure of the low pressure system.

Weather map for next Thursday (August 22):

Photo byWeather Prediction Center