Weather for New England and the Northeast

Area Forecast Discussion

National Weather Service Gray ME
Issued 628 AM EDT Sunday, May 31, 2026

**What Has Changed**

The Small Craft Advisory was allowed to expire on schedule for most coastal waters. The exception is the southern coastal waters where wave heights are hovering around 5 feet and are expected to remain near that level through the morning.

The Frost Advisory will expire on schedule at 7 AM as temperatures begin to rebound quickly after a very cold start to the day.

The aviation discussion has also been updated to reflect the 8 AM EDT TAF forecast package.

**Key Messages**

1. A cool air mass brings the chance for frost across the north and parts of the interior this morning.

2. A shortwave brings scattered showers and thunderstorms this afternoon. A few additional showers are possible Monday.

3. Seasonable temperatures and mostly dry weather are expected for the remainder of the week.

**Discussion**

**Key Message 1 Description**

Light winds and clearing skies allowed temperatures to fall significantly overnight across much of the region. Morning lows ranged from the lower to middle 30s across northern areas and parts of the interior, while southern locations and the coast generally remained in the upper 30s to lower 40s.

These conditions supported areas of frost across northern New England and portions of the interior. The Frost Advisory remains well placed for the affected areas.

**Key Message 2 Description**

An upper level disturbance, known as a shortwave, is moving south through a highly amplified weather pattern over eastern North America. Embedded areas of spin in the atmosphere, known as vorticity, are expected to cross the region from late morning through early evening.

This disturbance, combined with a weak area of low pressure at the surface, will help generate scattered showers and thunderstorms across much of Maine and New Hampshire today.

Afternoon temperatures will generally reach the upper 50s to upper 60s, while dew points remain in the 40s. Even though moisture levels are relatively modest, very cold air higher in the atmosphere will create enough instability for thunderstorm development.

Forecast instability values, measured by MUCAPE (Most Unstable Convective Available Potential Energy), are expected to range between 300 and 600 J/kg. Wind shear, which measures how wind speed and direction change with height, will generally remain weak but could reach 35 to 40 knots across southern New Hampshire.

While severe thunderstorms are not expected, the strongest storms could produce gusty winds and small hail because of the unusually cold air aloft. Thunderstorm activity should decrease after sunset, although a few showers may linger overnight.

By Monday, the main upper level disturbance will move east and south of the region. However, lingering counterclockwise flow around the departing system, known as cyclonic flow, may still generate a few daytime showers. Coverage should be much lower than today.

Forecast guidance also suggests enough instability may remain for an isolated thunderstorm Monday afternoon. High temperatures will range from the upper 50s to middle 60s. Overnight lows Monday night will generally fall into the lower to middle 40s.

**Key Message 3 Description**

The persistent upper level trough that has dominated New England weather will finally begin to weaken and move away by Tuesday.

This change occurs as an omega block pattern, a large scale atmospheric traffic jam that slows weather systems, begins to break down. At the same time, a stronger ridge of high pressure over Canada will shift southeastward into the northeastern United States.

For New England, this means several days of generally quiet weather with temperatures returning to near seasonal averages. A 1025 millibar high pressure system is expected to build across the region.

Winds will remain light, allowing afternoon sea breezes to develop along the coast on many days. Inland areas will generally see highs in the 60s and 70s through the week. Temperatures could climb above 80 degrees by Thursday and Friday as warmer air gradually moves into the region.

The overall pattern appears largely rain free. The two periods worth watching are Tuesday and next weekend.

On Tuesday, leftover cold air aloft from the current weather pattern could still trigger a few isolated daytime showers. By next weekend, some forecast models suggest another upper level disturbance may approach the region. However, confidence remains low regarding the timing and strength of any system this far in advance.