Round of Storms Sunday Morning as Heat Dome Begins to Set Up for New England

A ridge of high pressure will begin to build to the south and west of New England. New England will be located right on the northern edge of this ridge. This will allow for a wave of energy to ride over the top of the ridge and through New England this weekend. This looks to impact New England with a round of showers and thunderstorms from north to south Saturday night into Sunday morning.

This complex of storms will very likely be decaying as it enters New England Saturday night, and will continue to weaken as it pushes southward through the region. One of the biggest uncertainties will be just how well it can hold together as it moves south Sunday morning. With that said, chances are increasing that the system will hold together into southern New England. With a favorable setup, thunderstorms will be possible through the overnight and early morning hours Saturday into Sunday, including the potential for strong to severe storms.

Below: HRRR showing hourly weather from midnight to noon Sunday:

While the overnight and early morning hours aren't normally conducive to strong to severe storms, the setup will be supportive of at least a few stronger storms. A mesoscale convective system will be moving north of New England, parallel to its warm front. This system will be sustained through the night by a moderately fast flow aloft, which will help it move through quickly without completely falling apart as well as it feed it energy. The warm front will also advect instability into the region. While this still isn't overly favorable for severe weather, it wouldn't be surprising to see at least a couple storms become stronger.

The ridge of high pressure that this system will be working around will form into a heat dome, with temperatures and humidity on the rise Sunday afternoon, after that system clears out. The heat dome will continue to establish itself to New England's southwest. This is a favorable position to pump nearly the full intensity of the heat dome into New England. Sunday has generally trended warmer as the ridge of high pressure looks to win out in the afternoon, leading to mostly dry weather and sunshine. Some guidance still hints at some re-development of storms in the afternoon, but this is quickly becoming the less likely outcome.

This ridge is currently advertised with a height of 590-594 decameters extending into New England (the higher the decameters, the stronger the ridge and therefore, the higher the temperature potential). Though not quite as strong, this ridge is reminiscent of last June's heat dome. Temperatures at the 850mb level (about 4,700 feet above sea level) are poised to rise into the 65-75° range, highest over southern New England. This would support widespread 90s at the surface with a shot at 100° for warm spots of southern New England on Monday and Tuesday.

On Monday, a couple factors may come into play that keeps temperatures and humidity from reaching their full potential. First, a weak area of high pressure may build offshore, which would allow for a weak sea-breeze. This would keep the coastal plain from pushing well into the 90s. This could potentially keep eastern Massachusetts from reaching the 90° mark. Areas away from the coast (outside of the mountains and northern Maine) will likely surge well into the 90s.

The other factor will be the atmosphere's ability to mix down drier air aloft. This would cap dew points in the 60s to low 70s. While still humid, this could prevent humidity from reaching their highest possible levels. It will still be a hot and humid day, but extreme heat is not a lock for Monday.

Below: Euro showing potential temperatures Monday afternoon:

On Tuesday, the heat will likely peak for most in central and southern New England. Temperatures aloft will peak and a sea-breeze similar to Monday will be less likely. With nearly full sun, high temperatures will once again be well into the 90s with some spots potentially reaching the 100° mark. High humidity will bring feels-like temperatures into the 105-110° range.

Overnight lows may only drop into the low to mid 70s as well. For the northern tier of New England, a cold front will approach and, depending on the timing, could bring relief later Tuesday afternoon. As we hinted at in yesterday's article, extreme heat watches and warnings have been posted for a good chunk of southern and central New England.

All big heat in New England must end eventually, and a cold front looks to drop through New England around midweek next week, bringing this heat wave to an end. There's uncertainty in the exact timing, but late next week looks much cooler than the start of next week as a frontal boundary sets up, bringing clouds and showers.