Area Forecast Discussion
Issued by NWS Boston, MA

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369 FXUS61 KBOX 231150 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 750 AM EDT TUE AUG 23 2016 .SYNOPSIS...
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High pressure will bring beautiful late summer weather today with low humidity. Warmer and more humid conditions will return Wednesday through Friday. There will be a low risk for showers and thunderstorms Thursday night and Friday as a weak front passes. Another high will bring dry and less humid weather next weekend.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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730 AM Update... Other than some patchy low clouds and brief fog mainly across portions of the CT Valley and central Berkshires, skies dawned mainly clear across the region this morning. With light/variable or calm winds, temps dropped to the mid and upper 40s in the normally cooler valley locations of the CT Valley and interior E Mass, with readings in the 50s at most other locations except the lower 60s on the outer Cape and Nantucket. Any leftover patchy fog will dissipate by 13Z, with mainly clear skies continuing through the day with high pressure ridge from northern Maine through the Appalachians to the SE states. With light W-NW winds, it is possible that sea breezes may try to kick in around midday or early this afternoon. Near term forecast was in good shape, but have updated to bring conditions current. Still expect temps to reach the upper 70s to lower 80s. Previous Discussion... High pressure remains in control of our weather, although it will gradually move offshore through the Delmarva Peninsula. With plenty of sunshine, expecting temperatures to be similar to slightly higher than Monday. Weak seabreezes may develop, but not a lot of confidence owing to persistent north to northwest winds toward the top of the boundary layer. Much more comfortable humidity levels continue.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Dry weather continues. Expecting winds to be either southwest or south during this time. This should result in a warming trend during this time. Low confidence in some patchy fog late tonight. Most likely area where fog might develop would be across portions of western MA, particularly in the CT River valley. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights... * Warmer and more humid Wednesday night through Friday * Dry conditions much of this week, except a risk of showers/ T-storms Thursday night, then again Friday afternoon/evening * Dry and less humid weather returns next weekend Overview and model preferences... Medium range models and ensembles continue signal the typical subtropical ridge across the southern tier, which will build northward around mid to late this week. With increasing H5 heights as the high builds across the SE U.S., will see increasing temperatures and humidity through the end of the week. As the ridge tries to flatten out across the northeast, noting an H5 short wave in the W-SW wind flow aloft. This may signal the chance for showers/thunderstorms across western areas Thursday night as a weak surface front/reflection approaches. Marginal support seen with this feature, so precip looks to weaken overnight, but could fire up again during Friday afternoon/evening as the front continues to shift slowly east. As the weak system/front moves offshore, it eventually washes out by next weekend as the nearly zonal upper flow returns, while some models rebuild the ridge around the mid Atlantic and SE states. Large surface high pressure moves across New England, bringing more dry, less humid conditions for next weekend. As the high settles toward the Maritimes early next week, another front may approach but timing is in question. Details... Wednesday night and Thursday... Will see mostly clear skies Wednesday night with temps falling back to the upper 50s to lower 60s across the inland valleys, ranging to the mid-upper 60s along the immediate coast as SW winds continue to stir. May see some brief patchy fog if winds diminish during the early morning hours. As high pressure settles off the New England coast, H85 temps will rise up to +15C to +16C during Thursday, which will translate to highs in the lower-mid 80s. It will remain cooler along the S coast as SW winds gust up to around 25 mph or so. Thursday night and Friday... H5 short wave moves along in the W-SW flow aloft, with surface reflection/weak cold front works slowly SE out of NY state. Big question is whether there will be enough instability to kick off scattered showers/thunderstorms ahead of approaching front. Looks like it may occur across W Mass mainly east of the Berkshires by around midnight, but do not last long. Might see a few brief downpours as PWATs increase to around 1.9 to 2 inches. Noting only marginal instability during Friday as front slowly crosses. Noting SB LIs around zero, CAPEs around 500 or so J/kg, though decent TQ /18-19/ for possible elevated convection. Will see higher dewpoints pooling ahead of the front on SW winds, so may be just enough to see scattered afternoon/evening showers/ thunderstorms from Cape Ann across E and SE Mass/RI into E CT. Temps do rise to the mid-upper 80s so that may be enough to trigger convection. Saturday and Sunday... As the cold front pushes offshore by Saturday morning, much drier air works in from the Great Lakes and central Canada. Large high pressure builds east during the weekend, with more dry weather in place. H85 temps lower to +11C to +13C by Saturday night, so another batch of comfortable temperatures, especially Saturday night. As the high builds over northern New England on Sunday, will see temps a few degrees cooler as winds shift to E-NE during the day. Monday... As high pressure settles over the Maritimes, question will be the timing of another frontal system out of the Great Lakes. Models try to bring moisture into northern/western areas during the day, but timing remains in question. Carried only slight chance POPs in those areas for now. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/...
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Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... High confidence for mainly VFR conditions through Wednesday. Low risk for some patchy late night/early morning radiation fog at the typical fog prone locations. KBOS Terminal...High confidence in TAF. Low confidence sea breeze may develop this afternoon. It will need to be watched closely. KBDL Terminal...High confidence in TAF. Outlook /Wednesday Night through Saturday/... High confidence through the period. Wednesday night-Thursday...Mainly VFR. May see local MVFR-IFR conditions in patchy late night/early morning fog in normally prone valleys, depending upon whether SW winds diminish. Thursday night-Friday...Mainly VFR. Low risk for scattered showers/isolated thunderstorms Thu night over W Mass/N central CT, then Friday afternoon/evening across S coastal areas. Brief local MVFR conditions possible. SW winds gusting up to around 20 kt along the south coast Friday afternoon. Saturday...VFR. Sea breezes possible.
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&& .MARINE...
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Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... Today through Wednesday...High confidence. Expect winds and seas below small craft as high pressure moves offshore from the Delmarva Peninsula. Outlook /Wednesday Night through Saturday/... High confidence through the period. Wednesday night...Winds and seas below small craft criteria. Thursday and Friday...Small crafts may be needed for a time along the near shore waters. S-SW winds gust up to 20-25 kt mainly during the afternoon/evening hours, highest around Cape Cod and the islands. Seas building to around 5 ft on the southern outer waters Friday afternoon/evening. May see brief visibility restrictions in scattered showers/thunderstorms Friday afternoon/evening mainly on the southern waters. Saturday...Winds shift to N-NW and may gust up to 20 kt through midday from Cape Cod to the southern waters, then will diminish as high pressure builds in.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/EVT NEAR TERM...Belk/EVT SHORT TERM...Belk LONG TERM...EVT AVIATION...Belk/EVT MARINE...Belk/EVT

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