114 FXUS61 KBOX 052038 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 438 PM EDT Sat Sep 5 2020 .SYNOPSIS... High pressure will build into the waters south of Southern New England through the holiday weekend, with mainly dry weather, seasonable temperatures and low humidity levels. Warm and increasingly humid conditions will return Tuesday through the end of next week. Our weather pattern will turn unsettled with scattered showers and isolated thunderstorms possible at times during the middle and end of next week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Beautiful early-September afternoon in progress across Southern New England, with a ridge of high pressure to our south and deep dry air aloft leading to clear skies and comfortable humidity levels, along with modest W to NW breezes. While the forecast for tonight remains tranquil, satellite imagery to our west reveals a field of mid-level cloudiness over the lower Great Lakes, associated with a weak warm front tied to a 500 mb shortwave/vort maxima rippling through the northern Great Lakes region. This feature is progged to pass through northern New England, with the only notable effect in Southern New England being an increase in mid-level cloudiness, starting around mid-evening in the Berkshires/CT Valley and into the overnight for most N/W of I- 95. Probably could best describe it as variably cloudy with more clouds further N/W one goes. Possible some sprinkles could fall out in NW MA and the Berkshires overnight, but kept any PoPs at below mentionable as I do note it's falling out of a mid-level deck and there's about a 4000' deep sub-cloud dry layer. Returning light SSW winds will also bring about a minor increase in moisture level/dewpoints into the mid to upper 50s. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... Sunday through Sunday Night: Passage of initial shortwave trough/vort max in northern New England from overnight should lead to decreasing cloudiness early Sunday morning. However mean cyclonic flow appears to be maintained across the Northeast as another subtle 500 mb trough moves from the Great Lakes into the northern mid-Atlantic region. Though many are dry on Sunday, one potential fly in the ointment is a subtle SW to NE oriented convergence boundary that appears to set up in the afternoon nearby or along the I-84/Mass Pike/I-95 corridors. Actually is fairly good consistency across coarser-res and convective-allowing models in developing some QPF along the extent. Nearby soundings support idea of cumulus with shallow convective depth (small amount of CAPE below -10C) with a well mixed sub-cloud layer. Despite the good model agreement, given the dry air I'm dubious much develops and it is possible the QPF models show could just be cumulus. Have increased clouds along this area and carried isolated showers with PoPs no higher than 20%. Many however will stay dry and if any showers develop, not looking at a washout in any one area. Highs mainly in the 70s to low 80s, and while dewpoints will be higher than today, still comfortable. For Sunday night tranquil weather returns with clearing skies and light southerly winds allowing for upper 50s to lower 60s dewpoints to return to the region. Could have to watch for some patchy fog or mist as moisture levels start to rise especially favored South Coast/Cape Cod. Lows mid to upper 50s in the interior, with upper 50s to low 60s near the coasts and urban centers. && .LONG TERM /MONDAY THOUGHT SUNDAY/... Highlights * Sunny and fall-like weather continues Monday, but gives way to summery conditions Tuesday & Wednesday. Becoming more muggy heading into late week. * Unorganized showers develop mid-week as a cut-off low moves into the midwest. Unsettled and wet conditions into next weekend. Monday through Tuesday... Quiet and dry weather spills over into the start of next week thanks to a 1030mb high sitting off of the Canadian maritime. Fall-like temperatures will remain on Monday, generally afternoon highs reach the upper 70s to 80 degrees. The exception, the Cape and Island will remain in the low and middle 70s. Dew points are still refreshing in the 50s. Like Monday, Tuesday will be sunny and dry. The biggest difference will be temperatures. Monday the 850mb temperatures range between +11C and +14C. Compare that to Tuesday, 850mb temperatures are +14C to +17C. That likely yields afternoon highs in the mid-80s away from the coast. Additionally, dew points return to the mid 60s. Wednesday through Friday... Southern New England becomes squished between the coast high and an approaching cut-off low to the west. This will be our transition period as clouds increase, but it does appear for now it will remain dry as there isn't much moisture aloft. Chances for precip will rise heading into the second half of the week. The cut-off low get's hung- up over the Great Lakes, giving CT, RI, MA chances for a few unorganized showers Thursday into Friday. As for temperatures Wednesday should be the warmest day next week with highs in the middle 80s and dew points in the low and middle 60s. Thursday into Friday cloud cover likely will knock those temperatures back to the middle and upper 70s - though it will still be muggy as dew points will remain in the upper 60s and low 70s. Next Weekend... The surface low sits to our west over the Great Lakes and guidance suggests a period of rain along a warm front. WPC suggests it could develop across New York through southern New England. The surface low and trailing cold front pushes through Sunday before clearing out the following week. && .AVIATION /21Z SATURDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 18Z TAF Update: Rest of Today: High confidence. VFR. NW/WNW winds 6-12 kt gradually back to SW/SSW and lighten as they do so. Tonight: High confidence. Continued VFR tonight, though mid-level clouds increase late tonight into overnight especially N/W. Light S winds. Sunday: High confidence. VFR most of the day. Though not indicated in the TAFs due to low confidence, may have isolated showers after 17z between BOS- PVD-ORH-BDL along subtle convergence zone. S winds 5-10 kt, strongest near Cape Cod, with better chance at sea-breezes at BOS. Sunday Night: High confidence. VFR with light S winds. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Monday through Thursday/... Labor Day through Wednesday: VFR. Wednesday Night: Mainly VFR, with local IFR possible. Chance SHRA, patchy BR. Thursday: MVFR/IFR conditions possible. Chance SHRA, chance TSRA, patchy BR. && .MARINE... Tonight through Sunday Night: High confidence. Winds and seas to remain below small craft advisory levels through the period. High pressure will build into the southern waters through Sunday night. Light S winds tonight will become SW/S 10 kt with gusts in the upper teens kt range thru Sunday night. While seas mainly 3' or less, given the SW winds, locally choppy conditions possible after high tide near Buzzards Bay and Vineyard Sound on Sunday. Outlook /Monday through Thursday/... Labor Day: Winds less than 25 kt. Monday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Tuesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Wednesday Night through Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers, slight chance of thunderstorms, patchy fog. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Loconto/Gaucher NEAR TERM...Loconto SHORT TERM...Loconto LONG TERM...Gaucher AVIATION...Loconto/Gaucher MARINE...Loconto/Gaucher