textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast.

KEY MESSAGES

- Pleasant conditions through tomorrow as the region sits under high pressure. Lows tonight dip into the 40s and 50s.

- Showers, and possibly a few thunderstorms, with brief torrential rainfall possible late Sat night into the first half of Sun. Low probability for localized flash flooding.

- Dry and seasonable Mon-Tue but a brief bout of summer warmth and humidity possible Wed and/or Thu ahead of a cold front.

DISCUSSION

KEY MESSAGE 1...Pleasant conditions through tomorrow as the region sits under high pressure. Lows tonight dip into the 40s and 50s.

Large high pressure continues to make its way over southern New England through the rest of today, ending up directly overhead tonight. With clear skies and light to calm winds overnight, radiational cooling is expected to take control, allowing low temperatures to fall into the 40s and 50s tonight. Areas that radiate well should drop into the mid 40s while areas closer to the coasts and don't radiate as well will fall into the mid to low 50s overnight.

High pressure remains affixed over the region into tomorrow, then shifts off the east coast heading into the evening hours. 850 mb temperatures remain around 10-14C in the afternoon hours, and highs top out in the upper 70s, with areas closer to the coasts in the low 70s with local seabreezes.

KEY MESSAGE 2...Showers, and possibly a few thunderstorms, with brief torrential rainfall possible late Sat night into the first half of Sun. Low probability for localized flash flooding.

High pressure moves off the coast Saturday night, clearing the path for a low pressure to pass through Sunday. A larger high pressure over central Canada and the Northern Plains should drive a cold front well offshore by Monday morning. This will result in a rather brief period of rainfall across southern New England. The timing for the most likely period of rainfall has slowed slightly. It no appears to be some time from late Saturday night into Sunday morning. Rainfall should end from west to east Sunday afternoon. Low risk for thunderstorms as well, but not expecting severe weather.

The most likely outcome is one half to one inch of rainfall for most. However, there is a 35-50% chance for more than one inch of rainfall, especially across portions of eastern CT into RI. Regardless, it will be quite humid. Thus, localized downpours are possible. Will need to continue to monitor the flooding risk this weekend.

KEY MESSAGE 3...Dry and seasonable Mon-Tue. A brief bout of summer warmth and humidity possible Wed into Thu ahead of a cold front.

High pressure builds back into the region Mon and Tue,returning dry and seasonable weather. This high pressure system moves east of the region by the middle of next week. This may allow for a brief return of summerlike warmth/humidity some time Wed into Thu. There is a fair amount of uncertainty on the timing of another cold front Wed night into Thu. With a high pressure over the North Atlantic, would not be overly surprised if this timing winds up being slower with later forecasts. Until this front passes us by, expecting above normal temperatures for Wed into Thu.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

Rest of Today...High confidence.

VFR. NW winds 5-10 kt with occasional gusts to around 18 kt possible until around 22z this evening. Winds shift more SW after 20z towards the Cape and Islands.

Tonight...High confidence.

VFR. Calm/light NNW winds, with light onshore winds starting to come in during the early morning hours Saturday as high pressure moves in directly overhead.

Saturday...High confidence.

VFR. S winds 5-10 knots, except for sea breezes along much of the coast.

Saturday Night...Moderate confidence.

Generally VFR with MVFR/IFR moving in from W to E starting around 08z Sun. Chances for SHRA increase from W to E with these lower ceilings, especially through Sunday morning.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday through Wednesday/...

Sunday: MVFR/IFR conditions possible. SHRA, slight chance TSRA.

Sunday Night: VFR. Breezy.

Monday: VFR.

Monday Night: VFR. Breezy.

Tuesday through Wednesday: VFR.

MARINE

Forecaster Confidence Levels...

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

Through Saturday...High confidence.

Large high pressure continues building over the waters through Saturday, keeping winds and seas below Small Craft Advisory criteria. Visibilities should also remain high through this period. Seas 2-3 ft; winds shifting more NE tonight remaining generally at or below 10 kt, then shifting more SE Saturday.

Saturday Night...High confidence.

High pressure shifts further E out to sea Saturday night. Higher confidence that winds and seas remain below Small Craft Advisory criteria, though chances for showers and some embedded thunderstorms increase greatly heading into Sunday morning from W to E. Visibilities may diminish, especially in heavier rainfall.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain showers, slight chance of thunderstorms.

Sunday Night through Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

Tuesday through Wednesday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...None.