textproduct: Boston / Norton

WHAT HAS CHANGED

Confidence continues to increase in southern New England seeing a prolonged period of high heat and humidity through the second half of the week and into the weekend.

KEY MESSAGES

- Generally dry today with increasing humidity. Low risk for early morning showers across the Islands.

- Summer heat and humidity returns Thursday through the weekend with chances for diurnal scattered thunderstorms possible each day.

DISCUSSION

KEY MESSAGE 1...Generally dry today with increasing humidity. Low risk for early morning showers across the Islands.

A weak high pressure over western CT has brought mostly clear skies and calm winds to southern New England, leading to a little bit of river valley fog and dropping temperatures to around 60 across the usual radiator sites. A weak low pressure system has spun up over our southern waters tonight, leading to some scattered showers forming over the far southeastern waters, and there remains a low chance for those showers to push inland towards Nantucket through the early morning hours.

The high pressure should linger near NYC today, leading to generally dry conditions for most of southern New England. The low will slowly meander further east and offshore today as well. Once the low moves out to sea, winds will become predominately southerly, pushing warm, moist air onshore and dewpoints will begin to slowly tick up throughout today... likely approaching 70 by this evening. Otherwise, temperatures today remain in the mid to upper 80s with plenty of sunshine.

KEY MESSAGE 2...Summer heat and humidity returns Thursday through the weekend with chances for diurnal scattered thunderstorms possible each day.

A Bermuda high will begin to build in across the western Atlantic Ocean and as southerly flow continues through the night, dew points begin to surge into the mid to upper 70s by Thursday. 925 mb temps surge to near +22C each afternoon this week, leading to high temps near 90 Thursday through Saturday. Combined with near oppressive dew points of 72-76, "feels like" temperatures will climb to the upper 90s, possibly near 100 at times. Heat headlines are being considered through the second half of the week and possibly into the weekend; however, some uncertainty remains in exactly how hot southern New England could get with daily threats for diurnal thunderstorms.

Regarding the thunderstorm potential later in the week... a few weak, upper level disturbances passing through New England combining with the high heat/humidity and just enough instability will likely be enough to pop a few diurnal showers/thunderstorms each day Thursday through the weekend, with greatest chances across the interior on Thursday. Any thunderstorms that do pop have the potential to produce frequent lightning, gusty winds, and torrential downpours as PWATs will likely be around 2.0". Given the amount of rain southern New England has seen over the last week or so, any heavy downpours could lead to localized flooding.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

12z TAF Update:

Today...High Confidence.

VFR. Westerly winds this morning 5-7kts becomes SE.

Tonight...High Confidence.

Generally VFR. Increasing moisture tonight should result in MVFR/IFR CIGS, especially across the southern coastal areas. May also see a few -SHRA develop prior to 12z Thursday across CT.

Thurday...High Confidence.

Mix of VFR with MVFRcigs for western terminals early, becoming VFR. SW winds 5-10 kts.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Thursday Night through Sunday/...

Thursday Night: VFR.

Friday: VFR. Breezy. Chance SHRA, slight chance TSRA.

Friday Night: VFR. Chance SHRA, slight chance TSRA.

Saturday: VFR. Breezy. Chance SHRA, chance TSRA.

Saturday Night: VFR. Breezy. Slight chance SHRA, slight chance TSRA.

Sunday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Through Thursday... High Confidence.

Conditions generally below SCA levels through Thursday as a broad high pressure system sets up over the western Atlantic. A few periods of gusty SW winds near 20 kts are possible tonight across the northeastern waters and Thursday across the southern waters.

Outlook /Thursday Night through Sunday/...

Thursday Night through Friday: Winds less than 25 kt. Seas locally approaching 5 ft.

Friday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

Saturday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

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

BOX WATCHES/WARNINGS/ADVISORIES

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