Heat Briefly Relents Before Rebuilding Next Week for New England

A seasonably strong frontal system continues to pass to New England's north this morning. This system will continue to drag its cold front across the region, bringing in a much drier air mass. Dew points will be dropping back into the 50s with lower air temperatures as well. Since this is a strong system given the time of year, this change in air mass will come with wind. A large swath of New England is under a wind advisory today for gusts up to 50mph.

Moving into this weekend, 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. While placement and timing remains low confidence, it looks like a round of showers and thunderstorms will move into northern New England late Saturday or early Sunday morning and continue to dive southward through Sunday morning.

This complex of storms will very likely be decaying as it enters New England Saturday night, and will continue to weaken and fizzle 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 a favorable setup, thunderstorms will be possible through the overnight and early morning hours, including the potential for strong to severe storms.

Below: RGEM showing potential weather from midnight through noon Sunday morning. While this particular model shows the system completely dying before reaching southern New England, it's still possible it holds together longer:

The uncertainty in just how this system will behave and move through the region is reflected in the Storm Prediction Center's thunderstorm outlook. Both Saturday and Sunday have the western half of New England in a "marginal" risk (level 1 of 5) for severe thunderstorms. While both days look mostly dry with very limited to no thunderstorm activity, that overnight/Sunday morning system still has a lot of questions surrounding it.

Below: Storm Prediction Center thunderstorm outlook for Sunday (mainly for the morning):

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 will act as a transition day into the heat dome before the heat really ramps up Monday and peaks on Tuesday.

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.

Below: Euro showing potential heights early next week, showcasing a heat down with a height of 590-598 decameters across New England:

With high humidity, overnight lows will remain in the 70s and heat index values could top 100° across much of southern and central New England. This heat dome isn't favored to bring quite the level of heat as the June 2024 one and the northern tier of New England, particularly Maine, will be slightly "cooler" than what's being shown for central and southern New England. It wouldn't be surprising to see extreme heat watches issued for southern New England over the next 24-36 hours. These alerts have been posted for the Great Lakes and Pennsylvania as of Friday morning.

Earlier this week, there was uncertainty about whether or not waves of energy would ride over the top of the ridge and into New England, bringing the chance for thunderstorms each day. This is looking increasingly unlikely as trends are heading in the direction of the ridge having firm control over 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.

Below: Current weather map for next Wednesday (June 25):