textproduct: Boston / Norton

WHAT HAS CHANGED

No major changes to the forecast.

KEY MESSAGES

- Showers this morning dissipate heading into midday, then isolated thunderstorms possible in the afternoon/evening hours.

- Showers Saturday followed by a warming and drying trend that carries into next week.

- Warm and humid midweek, along with a risk of showers towards the second half of next week.

DISCUSSION

KEY MESSAGE 1...Dry weather for much of today before the risk for scattered showers and a few thunderstorms returns tonight into Friday.

Showers are crossing southern New England this morning as a warm front lifted north into southern NH and VT. There has not been much in the way of lightning flashes with these showers this morning, though some areas could see some locally heavy rainfall. Winds have shifted more southerly as a result of the warm front and dewpoints will continue to climb into the 60s heading through today. As a result, it may feel more humid outside today outside of showers/storms. The main concern remains focused on the possible storms this afternoon/evening. A stronger surface low secondary to the primary one shifting into Quebec will have its cold front approach southern New England today. Guidance has continued to favor strong effective bulk shear between 40-50 kt through this afternoon. For instability, generally around 1000-1500 J/kg of MLCAPE is favored among the CAMs for this afternoon (MUCAPE reaches ~2000 J/kg in some spots over central and western MA). This shear and marginal instability combined with the forcing that will come with the aforementioned low's cold front could aid in the development of isolated storms. CAMs have somewhat favoring central into eastern MA more regarding some storms developing, but exact areas cannot be nailed down as these are likely to be very scattered in coverage. The risk for them turning severe has trended down slightly over the latest updates, with the majority of the region now no longer under a Marginal (1/5) risk. However, given the strong wind field aloft, some storms developing damaging winds gusts cannot be completely ruled out.

KEY MESSAGE 2...Showers Saturday followed by a warming and drying trend that carries into next week.

Low pressure moving along a cold front is expected to track to our south Saturday. However, guidance continues to show some discrepancies regarding how far north any showers may reach. Some showers associated with this wave are more likely to scrape along the south coast into the Cape and Islands, but they are not expected to be very significant at this time. 00z NAM guidance pulled back and trended showers well south of the region, though Canadian and ECMWF guidance still indicates some showers reaching well into RI and CT to I-90. NAEFS guidance has also trended more anomalous PWATs north to the south coast along with ample midlevel moisture. Aside from these showers, though, dry weather is expected to return heading into the start of next week as high pressure associated with an amplified upper level ridge moves into southern New England. A warming trend also kicks off for the start of the work week, continuing into midweek. However, details on just how warm it may get are still uncertain at this time. The outlook for hazardous temperatures next week has shifted more of a slight (20-40 percent) to moderate (40-60 percent) for southern New England, which will be something we continue to monitor.

KEY MESSAGE 3...Warm and humid midweek, along with a risk of showers towards the second half of next week.

As noted in the previous message, the risk for hazardous temperatures over southern New England has trended up a bit for midweek next week. Humidity ticks up as a warm and more humid airmass moves in. A shortwave or two may "roll" along the eastern side of the upper level ridge, which may bring some unsettled weather for midweek. Location-specific and refined timing details are not yet known, though latest guidance is pointing towards sometime between Wednesday and Thursday.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

Through This Afternoon...Moderate confidence.

Showers continue to track from west to east this morning and will likely be free of all inland terminals by 14z. Showers likely continue thru 15z across the Cape and Islands before rapidly dissipating. Otherwise, mostly VFR outside of showers and storms today, though areas of MVFR and even some IFR are possible this morning in wake of showers. Fog continues at ACK thru 14z this morning.

The risk for isolated thunderstorms, some of which may turn severe, returns in the afternoon primarily after 21z. PROB30s were included at most terminals to account for this risk. Periods of MVFR visibilities and ceilings possible with any afternoon showers and storms. Uncertainty remains in exact location/overall coverage.

Tonight...Moderate confidence.

Showers and storms should clear the region by midnight. Patchy fog leading to areas of MVFR/IFR may develop overnight across much of SE MA, Cape Cod, and the Islands. Low stratus also a possibility, particularly towards the Cape and Islands. Winds shift more W and go light to calm overnight.

Saturday...Moderate confidence.

Mostly lower end VFR with areas of MVFR. Showers mostly scraping along the south coast are favored; lower confidence in those going much further north than that. These may also approach later in the day than expected. Light winds.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night through Monday Night: VFR.

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

MARINE

Forecaster Confidence Levels...

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

Through Saturday...High confidence.

Southerly winds continue into this morning and shift more SW tonight, then S to SE for Saturday. Occasional gusts to 20 kt over the waters this afternoon are not out of the question, then these should diminish tonight and remain low tomorrow. Seas should remain 2 to 3 ft. Showers and thunderstorms impact the waters today and possibly into early tonight. Showers associated with another low passing to our south will likely impact the southern waters Saturday.

Outlook /Saturday Night through Tuesday/...

Saturday Night: Winds less than 25 kt. Chance of rain showers.

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

Sunday Night through Monday Night: Winds less than 25 kt.

Tuesday: Winds less than 25 kt. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

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