textproduct: Gray - Portland

WHAT HAS CHANGED

No major changes were needed for this update. The chance for strong to severe storms has all but diminished. Still should have a few more hours of showers, but thunder will be limited.

KEY MESSAGES

1. Low pressure and an approaching cold front will bring rounds of showers through this evening.

2. Potential for widespread downpours/thunderstorms Tuesday- Wednesday. Locally heavy rainfall possible.

DISCUSSION

KEY MESSAGE 1 DESCRIPTION...

Forcing has been effective in producing rain with embedded thunder late this morning through the afternoon hours. While this was expected, the overall coverage and duration has been greater than forecast. As a result, the window to increase instability for possible strong to severe thunderstorms this afternoon into evening has become more slim.

Kinematics remain strong through this evening, and should storms find instability to initiate or hold strength into western portions of the forecast area, gusty to damaging winds remain possible. However, amid a push of low level smoke and substantial convective cloud debris, any daytime instability recovery is slim. There will be some degree of elevated instability as moisture profiles continue to saturate this evening, but would still be an uphill battle for the reasons outlined above. As a result, have kept enhanced wording out of the forecast and limited thunder timing and coverage.

Low level smoke will continue to reduce vis 2 to 5 miles through mid evening before being lifted northward ahead of the cold front. Visibility should improve shortly after midnight across much of the area.

It will remain breezy this afternoon into the evening hours, with a NW wind shift after midnight. Winds increase into Sunday morning, with gusts to 30 mph likely. There should also be clearing of clouds along the coast and interior, but upslope clouds may linger NW of the mountains. This will lead to a much more pleasant Sunday with highs in the 70s to around 80 along the coast...and dew point temps in the 40s to around 50.

KEY MESSAGE 2 DESCRIPTION...

Dry weather for Monday with SFC high pressure moving well to our southeast. As such, this will set up a southerly return flow regime with warmer temperatures and slightly more humidity.

A fairly deep short wave trough will approach Tuesday and Wednesday. This will bring increasing chances for widespread showers and perhaps a few thunderstorms Tuesday through Wednesday evening due to the slow-moving nature of the trough. Heavy downpours will be possible as PWATs rise to above 1.5, even as high as 1.75 inches. A few strong to severe thunderstorms will be possible as well depending on the eventual disposition of a warm front and any potential sunny breaks.

Canadian wildfires are expected to continue burning for the foreseeable future bringing the potential for continued decreased air quality from time to time.

Drier weather arrives for Thu and Fri. However, temperatures will be well into the 80s most folks as summer rolls on.

AVIATION /TONIGHT THROUGH THURSDAY/

Through Sunday night...HZ will be the main vis restriction through this evening, with areas of SHRA also bringing lower vis. Periods of MVFR/IFR vis likely until this area of smoke moves northeast after midnight local. A trend to VFR is likely at most terminals late tonight, with a NW wind shift behind a cold front. Winds become gusty late through Sunday morning, up to 30 kts. This should prevent BR/FG overnight, and wick smoke northeast. IFR/MVFR cigs may remain at HIE through the morning in upslope clouds. VFR conditions generally prevail on Sunday with gusty northwest winds continuing through the afternoon. MVFR ceilings and -SHRA may linger over HIE.

Outlook...

Monday: VFR expected.

Tuesday-Wednesday: MVFR to IFR possible with increasing chances for SHRA and a few TSRA.

Thursday: Becoming VFR after some morning showers.

MARINE

A cold front will approach the waters this evening, passing overnight. This should feature increasing southerly to southwesterly winds 25 to 30 kts, with occasional gusts to Gale through midnight local. Most of the gusts to Gale will be on the outer waters, but can't rule out some towards the Maine Midcoast this evening.

Winds shift offshore Sunday morning, remaining gusty but mostly falling below SCA levels. While wave heights will have built 5 to 8 ft, the NW winds should knock these down to 3 to 4 ft by mid Sunday morning.

High pressure builds in Monday, keeping conditions under SCA levels, and then the next front brings another chance at SCA conditions toward the middle of next week.

GYX WATCHES/WARNINGS/ADVISORIES

ME...Air Quality Alert until midnight EDT tonight for MEZ007>009- 012>014-018>028-033. NH...Air Quality Alert until 11 PM EDT this evening for NHZ001>015. MARINE...Small Craft Advisory until 8 AM EDT Sunday for ANZ150-152-154. Small Craft Advisory until 2 AM EDT Sunday for ANZ151-153. Gale Warning until 2 AM EDT Sunday for ANZ180-182.