textproduct: Gray - Portland

WHAT HAS CHANGED

Minimal changes have been made to the ongoing forecast at this time.

KEY MESSAGES

1. A weak frontal passage this afternoon will allow for the potential to see a few scattered thunderstorms, mainly across the interior. Nearly widespread patchy fog will develop behind the front. Some very weak instability tomorrow could also lead to an isolated shower or storm across the interior on Tuesday as well.

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

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

A cloudy, but very humid day has unfolded across northern New England. Thick cloud cover overhead should thin out through the afternoon, as low stratus progressively mixes out across the area. Less cloud cover later in the day will also allow for a marginal convective environment to set up ahead of a very weak cold front. CAPE of 300-500J and low low-level wind shear should allow for slower-moving thunderstorms. A couple wind gusts can not be ruled out with some of the stronger storms that develop. Despite the storms being slower-moving, storms will not move slowly enough to cause a flooding threat of any kind. The front is poised to stall over interior NH and ME tomorrow morning, allowing for showers to continue across the interior.

Scattered showers and thunderstorms continue tomorrow afternoon as the aforementioned front becomes quasi-stationary. Showers are storms should still be pretty scattered, as low stratus and fog overnight tonight should somewhat limit shower and storm development on Tuesday. Showers become more isolated Tuesday night and more patchy fog could develop along the CT river valley and along the coastal plain, likely lasting until sunrise Wednesday morning.

KEY MESSAGE 2 DESCRIPTION...

A cold front will approach New England Wednesday. While SW flow ahead of it will bring warming temps into the lower 80s for the day, the front moves overhead with little fanfare as forcing weakens and moisture is inconsistent through the atmospheric column. Sharpening of the trough looks to take place downstream, with smoothing of the embedded wave that will pass through northern New England. Expect much of the precipitation to dissipate to the west, but some moisture could build on the windward side of the Whites, resulting in isolated showers or sprinkles through the late afternoon and evening.

If the front continues to slow as the parent low occludes east of Hudson Bay, then it may wind up draped across the forecast area or just to the east. This would be the eventual pathway for low pressure across the Ohio Valley to track into the latter half of the week. Thus precip chances Thursday and Friday could eventually be in flux.

High pressure should be nearing the region come the weekend, but there will be the complicating factor of the slow moving boundary exiting, mentioned above, and a potential cut off low or trough arriving from the west. The combination of the low and return flow could spell for a damp period across much of the Northeast, but anticipate some slowing of the low's transit east which could help the first half of the weekend remain dry.

AVIATION /18Z MONDAY THROUGH SATURDAY/

THIS AFTERNOON THROUGH 12Z WEDNESDAY...Conditions could degrade down to IFR as showers move in and fog builds this evening. Although showers and storms look to generally become more isolated by Monday evening, restrictions will stay down as fog continues to spread across NH and western Maine. Fog looks to mix out with diurnal heating Tuesday morning.

MVFR is expected along the interior through the day Tuesday as isolated to scattered showers remain over the area. Coastal sites should stay dry, and potentially remain VFR during the day. Fog builds back in Tuesday night, with lower restrictions along the coast and across the CT river valley sites. Fog mixes out Wednesday morning.

Outlook...

Wednesday and Thursday: Mostly VFR. Some low ceilings are possible NW of the mountains for terminals such as HIE with SHRA. Also can't rule out lower ceilings or fog towards Penobscot Bay.

Thursday night and Friday: VFR, no sig wx.

Saturday: VFR likely, no sig wx.

MARINE

Winds and seas likely remain below SCA levels through the rest of the week. Areas of fog will be possible through Thursday. A cold front approaches the waters midweek, as a wave of low pressure passes south of New England and into the Gulf of Maine or open Atlantic. High pressure could return for the first half of the weekend.

GYX WATCHES/WARNINGS/ADVISORIES

ME...None. NH...None. MARINE...None.