textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast.

KEY MESSAGES

- A few rounds of scattered showers and t-storms possible each afternoon. Best chance is Thursday evening, then Saturday.

- Fall-like feel for Sunday, then more seasonable for Labor Day. A gradual warm-up throughout the week with continued dry weather through at least Wednesday or Thursday.

- Elevated risk for dangerous rip currents through the Holiday Weekend, especially Sunday into Labor Day.

DISCUSSION

KEY MESSAGE 1...A few rounds of scattered showers and t-storms possible each afternoon. Best chance is Thursday evening, then Saturday.

The frontal wave has brought a good amount of dry mid-level air in its wake allowing for plenty of breaks of sun, especially for western SNE. Mesoanalysis indicates about 1500 J/kg of surface based CAPE. High-resolution guidance has backed off on the coverage of convection with this second wave of precip chances for the afternoon and evening likely owing to the lingering cloudy skies/morning rain showers resulting in a less favorable environment. Even the latest HRRR is not initializing well, showing widespread convection at 19z while the radar remains nearly bare. Even so, as the front drops south it may kick off some isolated convection, expected to be sub severe with frequent lightning the main threat. The greatest threat will be along and south of the frontal boundary, mainly south of the MA pike.

Looking toward the Friday-Saturday period, drier NW flow kicks in with PWATs dropping down to around an inch or less. Expecting this to result in a mostly dry stretch with a mix of clouds and sun. Even so, with a mid level trough and low pressure just offshore we'll still see periodic diurnal shower chances. Certainly not a washout, but keeping low probability rain chances in the forecast, mainly for Saturday afternoon.

Friday will be the warmest day of the whole forecast as a slightly warmer airmass pushes in; 850 mb temps briefly reach ~15C Friday before dropping to ~8C Saturday resulting in high temperatures in the low to mid 80s and low to mid 70s respectively.

KEY MESSAGE 2...Fall-like feel for Sunday, then more seasonable for Labor Day. A gradual warm-up throughout the week with continued dry weather through at least Wednesday or Thursday.

Saturday night through the middle of the upcoming week features fairly benign conditions, with little in the way of rainfall chances. The 500mb forecast map shows somewhat of an omega ridge centered across the middle of the country, with a closed mid-level low centered over Nova Scotia Sunday afternoon. The omega ridge flattens out, with semi-zonal flow developing across the coast by Tuesday and then shortwave troughing for late week across the northeastern states, likely leading to the next chance for active weather for southern New England. At the surface, high pressure builds in from the northwest Sunday, with its origins in northern Canada. Surface high pressure remains the dominant weather feature throughout the majority of the forecast period, leading to a stretch of dry weather.

Temperatures aloft are cooler Sunday, associated with that mid-level low east of New England. 925mb temperatures are only around +8C to +10C, which with boundary layer mixing supports highs in the upper 60s to low 70s. Thus, Sunday will feel very much like autumn, with a blend of sun and clouds, northerly winds and dew points in the low 50s. While winds won't be overly strong, the combination of cooler temperatures and lower dew points will make for a rather crisp day. Sunday night could feature some decent radiational cooling as high pressure settles across the region, though this will depend on how quickly winds diminish. If winds become light enough, NBM guidance may be too warm across the typically cooler, effective radiators. For example, the NBM has KOWD around 54F, while the cooler CONSMOS guidance suggests temperatures could fall as low as the mid to upper 40s. Otherwise, lows are generally expected in the 50s.

Good news if you aren't ready for pumpkin spice weather, as temperatures will trend warmer throughout the week from WAA aloft. 925mb temperatures climb +14C to +18C, supporting near-seasonable highs in the upper 70s for Labor Day, then upper 70s to lower 80s Tuesday into the middle part of next week. Humidity remains tolerable as well, with dew points generally in the upper 50s to around 60F. Labor Day itself looks quiet and dry, though there will be a high risk for rip currents along the ocean beaches.

KEY MESSAGE 3...Elevated risk for dangerous rip currents through the Holiday Weekend, especially Sunday into Labor Day.

Persistent northeast flow, long-period swell, and offshore seas of 4- 7 feet will continue to support an elevated risk for dangerous rip currents through the Holiday Weekend, especially Sunday into Labor Day for east-facing ocean beaches. With otherwise quiet weather expected, those heading to the beach should be mindful that ocean conditions may still be hazardous. Be sure to check with local beach staff or lifeguards regarding ocean conditions before entering the water.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

This afternoon: Moderate confidence in coverage of TSRA.

Mix of MVFR- VFR for most. Risk for widely SCT SHRA/TS between 20-02z from central MA to the eastern MA coast. Other than BOS, SW/W winds 5-10 kt this afternoon for most.

Tonight: Moderate confidence.

SHRA/TS moves offshore, with brief period of VFR except MVFR-IFR holding on for Cape and Islands. Winds turn N/NE after 03z in NE MA, light and variable some spots. This brings the return of MVFR stratus from the waters/coastal ME/NH. Uncertain on the timing and how far west the low clouds could make it, but seems ORH eastward has the best shot.

Friday: Moderate confidence.

VFR west of ORH, MVFR-IFR for ORH south and east with stratus to start. Should see SCT-BKN VFR/MVFR decks with MVFR more likely for the Cape and Islands rest of the day. N/NE winds 5-10 kt, decreasing to light and could be variable directions by afternoon.

Friday night: High confidence.

VFR. NW winds 5-10 kts.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Friday Night through Tuesday/...

Saturday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, slight chance TSRA.

Saturday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA.

Sunday: VFR. Breezy.

Sunday Night through Tuesday: VFR.

MARINE

Forecaster Confidence Levels...

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

Today through Friday Night...

Winds shift to the west/northwest through Thursday night into Friday morning before shifting to the S/SW late Friday. A few showers and t-storms may move over the southern waters this evening then tranquil weather persists. Seas 2-3 ft.

Outlook /Friday Night through Tuesday/...

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

Saturday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas.

Sunday Night through Labor Day: Winds less than 25 kt. Local rough seas.

Monday Night through Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

BOX WATCHES/WARNINGS/ADVISORIES

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