636 FXUS61 KBOX 010132 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 930 PM EDT Mon Jul 31 2017 .SYNOPSIS... High pressure moving east of the region will result in warm and humid weather for the second half of the week. Diurnally driven scattered showers/thunderstorms are possible Wednesday through Friday, mainly inland from the southeast New England coast. Perhaps a better chance for more organized precipitation sometime on Saturday as a cold front crosses the region. A bit cooler and less humid weather should follow Sunday and Monday. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 930 pm update... Showers have quickly dissipated across far northeast MA over the past hour. Otherwise, mainly clear skies overnight with light winds. Dewpoints somewhat higher than last night, so it will not be a cool. Expect overnight lows to bottom out in the upper 50s to lower 60s in many locations. Patchy ground fog should develop late in the typically prone areas. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Tuesday into Tuesday night... Risk of a daytime spot shower, potentially lingering overnight. Indications of a mid-level feature presently over the NE CONUS along with collocated low-level moisture confluence and K-indices around 30 sags S roughly W to E across S New England. Weak lifting and forcing mechanisms in play, thinking that any activity that emerges is a result in combination with onshore sea- breezes, terrain influences, and/or boundary layer destabilization. Mainly thinking airmass thunderstorms, isolated to widely scattered. Weak shear, nothing should get too organized unless anchored to a boundary or along a ridge. Any cold pools could become a focus or any additional convection. However, no certainty on where and when these would develop, model forecast guidance is all over the place. Still dry air to contend with and marginal lapse rates. Will hold off from mentioning any slight chance PoPs for now given low risk threats and uncertainty. Worst case scenario, as mean winds are light, should storms develop and hang over a particular locale, localized flooding is possible. But again, low confidence. Otherwise dry with highs getting up to near 90 degrees. Can't rule out the risk of shower activity into evening, overnight as the mid-level feature pushes back N with return S flow, but again will hold off from mentioning slight chance PoPs. Much of the activity presently forecast is primarily diurnally-driven. Indications from the 31.12z NAM of higher dewpoint air beneath an inversion aloft as the boundary layer decouples. Perhaps some low cloud and fog issues, however confidence is low given the uncertainty of potential scattered to broken cloud decks remnant with any wet- weather activity, and the NAM can be a bit over- done on low-level moisture. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Highlights... * Typical summer warmth and humidity this week * Mainly diurnally driven scattered showers/t-storms Wed/Thu/Fri * Perhaps more organized showers/t-storms with a cold front Sat * A bit cooler and less humid Sun and Mon Details... The overall pattern will feature an anomalous upper level trough getting carved out across the Great Lakes. This will result in southwest flow aloft across southern New England and slightly above normal temps for the remainder of the work week. Highs will mainly be well up into the 80s and it will feel a bit muggy with dewpoints in the 60s. Nothing too unusual though for early August. Precipitation chances and timing are always difficult in the extended forecast, but particularly this time of year. Subtle shortwaves coupled with enough moisture/instability will likely trigger diurnally driven scattered showers and thunderstorms Wed/Thu/Fri, mainly away from the marine influence of the southeast New England coast. The overall severe weather threat remains quite low over this time, given weak wind fields. However, this will bring the potential for any thunderstorm that develop to move extremely slow and result in a very localized heavy rain/urban street flooding threat. Current guidance suggests that the cold front will cross the region Sat or Sat night. This may end up being our best chance for more organized showers and thunderstorms, but it is way too early to say that with any confidence. Behind the cold front, it does appear that cooler and less humid weather arrives by next Sun/Mon. && .AVIATION /23Z MONDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...Moderate confidence. Tonight... VFR. Light winds. Localized IFR with patchy ground fog, mainly for typically prone locations such as sheltered, low-lying valleys near bodies of water (i.e., CT River Valley). Tuesday... Low risk of a spot SHRA/TSRA. Otherwise continued light winds. VFR. Sea-breezes developing once again around late-morning into midday. Tuesday night... VFR. SCT-BKN mid to high CIGs possible. Light winds becoming S. Low risk SHRA. KBOS Terminal...VFR. Another sea-breeze expected around late- morning into midday Tuesday. KBDL Terminal...VFR. Low risk of a spot SHRA/TSRA Tuesday. Outlook /Wednesday through Saturday/... Mainly VFR other than a few hours of late night/early morning patchy fog possible at times in the typically prone locations. Also, a few mainly diurnally driven showers/thunderstorms may result in localized lower conditions Wed through Fri. Perhaps a period of more organized showers/thunderstorms sometime, but that is highly uncertain at this point. && .MARINE... FORECASTER CONFIDENCE LEVELS... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...High confidence. Tranquil boating weather throughout. Seas below 4 feet as winds remain light with sea-breezes along the shores. Will see light winds turn S going into Wednesday morning. Outlook /Wednesday through Saturday/...High confidence. Weak pressure gradient will keep winds and seas below small craft advisory thresholds. Southerly flow and good mixing over the land should generate a few hours of afternoon wind gusts around 20 knots across our near shore waters. This will result in a period of some choppy seas for the typically vulnerable Harbors and Bays. Diurnally driven isolated thunderstorms possible Wed through Fri, mainly near shore. Perhaps a few more thunderstorms sometime on Sat. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Sipprell/Frank NEAR TERM...Frank SHORT TERM...Sipprell LONG TERM...Frank AVIATION...Sipprell/Frank MARINE...Sipprell/Frank