Weather for New England and the Northeast

**Area Forecast Discussion, National Weather Service Gray ME, 310 PM EDT
Sun Aug 16 2026**

**What Has Changed**

Model guidance remains consistent in keeping most of tonight rainfall north of the mountains. Some high-resolution models, known as CAMs or convection-allowing models, show the possibility of showers developing and repeatedly moving into far northern New Hampshire and northwestern Maine. Rainfall amounts have been adjusted to account for these changes. Otherwise, the forecast remains on track.

**Key Messages**

1. Rain accompanies a passing system tonight into Monday morning. A period of moderate to heavy rainfall after midnight and early Monday morning could result in nuisance flooding or ponding in poor drainage areas for the morning commute.

2. Low-impact weather is expected mid to late week, with a couple chances for light rain.

**Discussion**

**Key Message 1**

This evening, an area of low pressure will move in from the Great Lakes, bringing an increasing chance for showers overnight. The atmosphere will contain a great deal of moisture, with precipitable water values, or PWATs, between 1.5 and 1.8 inches. These values are near the 90th percentile, meaning the atmosphere has an unusually large amount of moisture available for rainfall. This could allow showers to produce rain very efficiently.

The atmosphere does not appear especially favorable for strong thunderstorms, with poor temperature changes through the atmosphere and very little CAPE, which is the measure of atmospheric instability available to fuel thunderstorms. A few rumbles of thunder cannot be ruled out, but heavy showers are expected to be the main concern.

High-resolution CAM guidance has consistently shown the most numerous and heaviest showers north of the mountains. Strong winds higher in the atmosphere, with more than 70 knots of effective wind shear, should help showers move across the region fairly quickly. However, some showers may develop repeatedly over the same northern areas. This backbuilding, meaning new showers forming upstream and moving over the same area, could increase the potential for localized flooding.

Showers should be most numerous across northern New Hampshire and northwestern Maine. Three-hour Flash Flood Guidance in this area is relatively low, between 1.80 and 2.50 inches. Flash Flood Guidance is an estimate of how much rainfall over a given period could cause flooding. Because the guidance is relatively low, it will not take an extreme amount of rain to produce nuisance flooding in vulnerable locations.

Rainfall amounts are expected to vary considerably. Areas north of the mountains will likely receive at least one-half inch, with locally higher totals of 1.5 to 2.5 inches possible. Showers are also possible south of the mountains, but they should be more isolated as some of the available moisture is drawn toward another area of low pressure near the Mid-Atlantic. Even so, beneficial wetting rainfall is likely across southern areas.

The low pressure system will exit Monday morning. Moisture will remain in place, with dewpoints in the upper 60s. Daytime heating could produce enough instability for a few isolated showers and thunderstorms near the Connecticut River Monday afternoon. Fog and low clouds are also likely to move onshore, producing gloomy and foggy conditions through the second half of Monday and into Tuesday morning.

**Key Message 2**

Tuesday, low-level moisture may remain trapped along the coast and across parts of the interior. Conditions will depend partly on the position of a low pressure system as it moves away from southern New England and pivots toward or just outside the Gulf of Maine.

Northerly winds behind the low should gradually remove the moisture, but winds of only about 10 knots at 850 millibars, roughly 5,000 feet above the ground, will make this process fairly slow.

Forecast guidance shows the possibility of isolated afternoon showers or thunderstorms Tuesday across portions of the interior where remaining moisture combines with daytime heating. The lower atmosphere will remain moist, while the middle and upper levels of the atmosphere become much drier. Warmer air moving in aloft could also create a cap, which is a layer that limits rising air and prevents thunderstorms from becoming more widespread.

Because of these limitations, precipitation chances have been kept relatively low. Showers and thunderstorms cannot be ruled out, but they are expected to remain isolated because of the dry air aloft and limited instability.

**Wednesday**

Warmer weather is expected Wednesday as southerly winds develop ahead of an elongated cold front. High temperatures should reach the lower 80s, a few degrees warmer than Tuesday.

The approaching front will bring precipitation, but the amount of lift available to generate widespread showers is uncertain because the main low pressure system will remain well to the north and east near Hudson Bay. As a result, precipitation across New England may depend largely on how much daytime instability develops and whether the timing of the front coincides with that instability.

**Thursday and Late Week**

A disturbance moving through the southern part of the jet stream may pass just south of the region Thursday before moving across the Gulf of Maine or the open Atlantic. This could bring a few showers, mainly across the northwest side of the disturbance. However, a sufficiently dry layer in the atmosphere could limit rainfall.

High pressure then appears likely to return late in the week, potentially bringing improving weather and a sunny start to next weekend.