Weather for New England and the Northeast

Area Forecast Discussion, National Weather Service Boston/Norton MA, 729 PM EDT
Sat Sep 19 2026

**WHAT HAS CHANGED**

No significant changes.

**KEY MESSAGES**

1. Quiet through the rest of today, cooler tonight, with clouds returning before sunrise.

2. Briefly dry early to mid morning, then beneficial rain overspreads southern New England and continues through the evening and overnight hours. Flooding concerns remain low.

3. High pressure Tuesday gives way to a coastal system for the second half of the week.

**DISCUSSION**

**KEY MESSAGE 1, Quiet through the rest of today, cooler tonight, with clouds returning before sunrise**

A 1020 to 1025 mb high pressure system responsible for todays gorgeous weather drifts offshore tonight ahead of the next system arriving Sunday. Before that happens, continued fall-like weather is expected this afternoon and overnight.

Winds will weaken overnight, becoming fairly light or calm in some areas. Cloud cover should be slower to arrive than initially expected. Clouds will push in from the west overnight, but they should initially be mainly high clouds. This means there should still be a period of good radiational cooling during the first part of the night, while eastern areas of southern New England may remain mostly clear for much of the night before clouds fully arrive.

As is typical with this type of setup, the NBM, or National Blend of Models, appears too mild, so cooler MOS, MET, and MAV guidance has been incorporated. This highlights the colder pockets along the I-495 corridor, the hollows of northern Massachusetts, and Martha’s Vineyard. These areas should fall well into the lower 40s tonight, although an isolated upper 30s reading is possible.

Urban centers such as Boston, Providence, and Hartford should remain in the upper 40s to lower 50s. Worcester should stay relatively mild because of its elevation and location near the top of the nighttime temperature inversion, a layer where temperatures can behave differently with height.

**KEY MESSAGE 2, Briefly dry early to mid morning, then beneficial rain overspreads southern New England and continues through the evening and overnight hours. Flooding concerns remain low**

Conditions Sunday will not be ideal for outdoor activities, with a raw, cool, and rainy day expected. High temperatures should reach mainly the lower to middle 60s across the coastal plain, with middle to upper 50s across the higher elevations of southern New England.

A subtle mid-level northern stream trough, an area of lower atmospheric pressure aloft, arrives from the west early Sunday morning. It will be accompanied by a modest 850 mb jet, meaning a stronger current of wind about 5,000 feet above the ground. The jet weakens as it moves east, but it should provide enough lift to take advantage of PWATs, or precipitable water values, ranging from 1.4 to 1.9 inches. That is roughly 150 to 200 percent of normal.

Despite the unusually high moisture content, there is not much concern for impacts similar to last Sundays heavy rainfall and flooding. Last Sundays event was considerably more convective, meaning showers and thunderstorms produced more concentrated and intense rainfall. Sundays rainfall should be predominantly stratiform, meaning widespread and steadier rain. This should result in lower rainfall rates and greatly reduce the potential for localized torrential downpours.

Widespread rain should develop during the mid to late morning and persist well into the evening. There is good agreement among the 19/12Z high-resolution guidance suite. By 2 PM EDT, rain should be widespread across much of the region. The exception will be the outer Cape and Nantucket, which may remain dry for another hour or two.

There is some limited instability near the south coast, so a rumble of thunder and briefly heavier rainfall cannot be ruled out. Another area to monitor is near the Massachusetts Turnpike and the transition from the coastal plain into the higher terrain of central Massachusetts. High-resolution guidance shows a convergence boundary developing in this area, where winds come together and air is forced upward. This could produce a corridor of enhanced rainfall.

Overall, rainfall amounts of 0.5 to 1.0 inch are expected, although amounts will vary from town to town, especially near areas of enhanced rainfall. The HREF, or High-Resolution Ensemble Forecast system, shows localized amounts approaching 2 inches. This represents the upper end of the guidance range, but confidence in amounts this high is quite low.

Given the generally lower rainfall rates, the risk of flooding remains low. Some minor ponding is possible where leaves or other debris clog storm drains, but otherwise this should be beneficial rainfall for the region.

With plenty of cloud cover overnight and a breezy northerly wind, there are no concerns for an especially chilly night. It will remain raw and wet, with lows in the upper 40s to lower 50s. Rain will shift offshore with the front early Monday morning, ending by or before daybreak.

**KEY MESSAGE 3, High pressure Tuesday gives way to a coastal system for the second half of the week**

Ensemble guidance remains in good agreement that an anomalously strong high pressure system will develop over Quebec Tuesday and linger into Wednesday and Thursday. This system will likely keep temperatures across New England cooler than normal, with highs in the low to middle 60s.

Both deterministic guidance, which uses individual model forecasts, and ensemble guidance, which uses multiple model forecasts to show the range of possibilities, continue to indicate the potential for a coastal low to form sometime Thursday into Friday.

There is still a large amount of uncertainty in the forecast at this time. However, the unusually strong high pressure system to our north and a low offshore could produce a tight pressure gradient, meaning a larger difference in air pressure over a relatively short distance. This could lead to strong winds during the week, especially along the south coast, Cape Cod, the Islands, and the coastal waters.

Depending on how close the low tracks to the region, there is also potential for a few periods of rain.