Weather for New England and the Northeast

**Area Forecast Discussion, National Weather Service Boston/Norton MA**
**406 AM EDT Tuesday, July 21, 2026**

**What Has Changed**

The Gale Watch has been downgraded to Small Craft Advisories because confidence has decreased that gale force winds will be widespread or persistent tonight and Wednesday.

**Key Messages**

* Scattered showers and thunderstorms return this evening through Wednesday morning. Risk for a few strong to severe storms and heavy downpours. Localized flash flooding possible in poor drainage areas.

* Scattered thunderstorms possible later Wednesday, but will be dependent on the degree of clearing during the day.

* Drying out Thursday into the latter part of the week with seasonable temperatures and lower humidity into the weekend.

**Discussion**

**Key Message 1, Scattered showers and thunderstorms return this evening through Wednesday morning. Risk for a few strong to severe storms and heavy downpours. Localized flash flooding possible in poor drainage areas.**

An upper level trough, an elongated area of lower pressure in the atmosphere, will slowly move across the eastern United States and Canada today through Thursday. Several shortwave disturbances, smaller areas of energy rotating through the larger weather pattern, will move through the region. At the surface, several frontal boundaries will cross the Northeast as an area of low pressure tracks across Quebec.

This weather pattern will bring back unsettled conditions with the potential for strong thunderstorms and localized flash flooding tonight into Wednesday.

A strong low level jet, a corridor of fast moving winds a few thousand feet above the ground, with winds of 40 to 50 knots will transport much richer moisture into southern New England. Dewpoints will climb to around 70 degrees, while atmospheric moisture levels increase to between 1.5 and over 2.0 inches. This combination will provide plenty of fuel for heavy rainfall.

Forecast guidance suggests enough instability, atmospheric energy needed for thunderstorms, to support storm development if one of the approaching disturbances arrives at the right time. Wind profiles also indicate increasing wind shear and helicity, a measure of how winds change with height and how much the atmosphere can rotate. This could allow one or two storms to become strong or severe with damaging wind gusts. There is also a very low risk of a brief rotating storm developing.

Very high atmospheric moisture combined with deep warm cloud layers will make rainfall very efficient. Forecast precipitation estimates have decreased slightly from previous model runs, but there is still a strong signal that many locations could receive over 1 inch of rain, especially along the South Coast, Cape Cod, and the Islands. Some locations in those areas could receive over 2 inches.

How quickly this rain falls will determine the flood risk. Thunderstorms embedded within larger areas of rain could produce localized flash flooding. While storms should move steadily because of stronger winds aloft, the persistent flow of moisture from the southwest may allow multiple storms to track over the same locations, a process known as training. This increases the risk for localized flooding.

The greatest concern remains urban locations and poor drainage areas, including cities such as Providence and Hartford. Current guidance suggests flash flooding will remain localized rather than widespread, so a Flood Watch is not expected at this time.

The highest chance for showers and thunderstorms will be from this evening through the overnight hours and into early Wednesday morning. While a few storms could develop late this afternoon, coverage should increase significantly this evening.

**Key Message 2, Scattered thunderstorms possible later Wednesday, but will be dependent on the degree of clearing during the day.**

Rain should gradually taper off Wednesday morning. Most forecast guidance moves the bulk of the rainfall out of the region by late morning, but there remains uncertainty about how much sunshine develops during the afternoon.

If clouds linger or additional showers persist, daytime heating will be limited and thunderstorm development would be less likely. If skies partially clear, enough instability could develop for scattered thunderstorms to form ahead of an approaching cold front during the afternoon and evening.

Atmospheric moisture will not be quite as high as Tuesday night, but another increase in humidity is possible ahead of the front. Forecast models continue to differ on the timing, coverage, and strength of any thunderstorms. Western and central southern New England have the greatest chance of seeing stronger storms because they are more likely to experience earlier clearing and additional daytime heating.

If thunderstorms do develop, one or two could once again become strong or severe.

**Key Message 3, Drying out Thursday into the latter part of the week with seasonable temperatures and lower humidity into the weekend.**

The cold front moves east of the region by Thursday morning, allowing drier air to move into southern New England. The upper level trough also shifts into eastern Canada while high pressure builds eastward from the Great Lakes.

This pattern will bring several days of dry weather with comfortable humidity levels through much of the weekend.

Temperatures a few thousand feet above the ground will cool enough to allow overnight lows across the interior to fall into the lower 50s Wednesday night. Despite the cooler air aloft, the strong late July sun will keep afternoon temperatures close to normal for this time of year.

Humidity may begin to increase again by Sunday as winds turn back to the south. A coastal area of low pressure could pass offshore, but any impacts remain uncertain at this time.