textproduct: Boston / Norton

WHAT HAS CHANGED

Small Craft Advisory canceled.

KEY MESSAGES

- Mostly quiet through Wednesday night with a stray shower or t-storm Tuesday afternoon.

- A round or two of scattered showers & thunderstorms possible Thu afternoon into Fri along with summerlike humidity as well.

- Mainly dry and seasonable weather follows for the weekend. Temps may trend above normal early next week.

DISCUSSION

KEY MESSAGE 1...Mostly quiet through Wednesday night with a stray shower or t-storm Tuesday afternoon.

Surface high pressure continues to influence southern New England's weather as it builds in from the Ohio valley this afternoon. Even so, a lingering mid level trough/cold pool aloft is leading to a smattering of diurnal cumulus and hit-and-miss showers over western/central areas. Mesoanalysis shows ~1000 J/kg of CAPE which, in the absence of any real bulk shear may lead to a stray thunderstorm or two at most. With sunset these showers will dissipate and cloudcover quickly recede. Tonight expect clear skies with light winds and patchy fog in the interior where dewpoint depressions may be near 0. Wednesday is dry and sunny with mid level ridging building in. As this happens, the low/mid level flow backs to the SW 850mb temps bump up from ~11C to 12-13C pushing high temperatures a few degrees warmer on Wednesday, into the upper 70s/low 80s with cooler temps along the coast.

KEY MESSAGE 2...A round or two of scattered showers & thunderstorms possible Thu afternoon into Fri along with summerlike humidity as well.

The model guidance is in fairly good agreement in an approaching shortwave trough/cold front late in the work week. Out ahead of this disturbance...S-SW flow will result in the return of low level moisture and summerlike humidity. While specific timing remains uncertain...the potential exists for a round or two of scattered showers and thunderstorms sometime Thu afternoon/night into Fri. The CSU machine learning probabilities also indicate a low risk for severe weather/heavy rainfall. That is basically climatology for an approaching shortwave this time of year. But the question remains does the forcing/instability lineup favorably for that potential to be realized along with various mesoscale processes. It is just too early to determine that at this time. Nonetheless...certainly something to watch over the next day or two.

KEY MESSAGE 3...Mainly dry and seasonable weather follows for the weekend. Temps may trend above normal early next week.

High pressure builds in behind the departing shortwave/cold front for the upcoming weekend. The result will be mainly dry and seasonable weather Sat into Sun. Ensembles indicating upper level flow may become more westerly early next week allowing for temps to trend above normal.

AVIATION /19Z TUESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

18Z Update...

This afternoon...High confidence.

VFR. Mostly dry with a few spot showers during the afternoon. W winds 6-12 knots, except some 20+ knot gusts possible towards the upper Cape.

Tonight...High confidence.

VFR. Calm/Light WNW winds. Patchy fog possible.

Wednesday...High confidence.

VFR. Light west winds, with local seabreezes towards the coast.

Wednesday night...High confidence.

VFR. Winds light and variable. Patchy fog possible.

KBOS Terminal...High confidence in TAF.

We think pressure gradient remains just strong enough to result in mainly W winds today. However, the low probability exists for a few hours of sea breeze. This risk/duration too limited to insert into the TAF at this time.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday Night through Sunday/...

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

Thursday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA, slight chance TSRA.

Friday: VFR. Chance SHRA, chance TSRA.

Friday Night: Mainly VFR, with local IFR possible. Chance SHRA.

Saturday through Sunday: VFR.

MARINE

Forecaster Confidence Levels...

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

Through Wednesday night...High confidence.

Fairly quiet boating conditions through the first half of this week as high pressure develops across the Midwest before expanding toward the waters off the coast of southern New England. Gusty southwest flow develops today, with gusts around 20 kt. Conditions improve overnight into early Wednesday morning as winds shift to the northwest.

Outlook /Wednesday Night through Sunday/...

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

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers, slight chance of thunderstorms.

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

Saturday Night through Sunday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

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