Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 242011 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 411 PM EDT TUE MAY 24 2016 .SYNOPSIS... Scattered showers and isolated embedded thunderstorms over Western portions of MA and CT will continue into early this evening. Scattered showers may also develop across portions of Southern RI and southeast MA early this evening as low pressure slowly moves across southeastern New England. An upper level high pressure ridge will then bring very warm to hot weather to most of the region Wednesday through Saturday, except for cooler temperatures at times on the immediate coast. A few showers and thunderstorms are possible Thursday night into Friday, but a better chance exists Saturday afternoon and evening ahead of a backdoor cold front. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... 400 PM Update ... Vertically stacked low over the region with -19c air at 500 mb. This cold air aloft combined with cyclonic flow is resulting in scattered showers and embedded thunder. The convection is focused on the western side of the low where SPC mesoanalysis indicates some baroclinicity at 850 mb and 925 mb along with some breaks of sunshine yielding 250-500 j/kg of SB cape per mesoanalysis. This will continue to be the theme thru sunset with convection focused across this region. A second area of showers may develop over Southern-Southeastern RI into Southeast MA as plume of deeper moisture pivots northeast off the ocean into that area. This is supported by multi model K indices and latest trends seen on water vapor satellite imagery. Already seeing the first signs of this with light showers developing over Marthas Vineyard and Elizabeth Islands. However these showers should be weak/low top with not a lot of impact. Thus not a washout expected this evening. Otherwise drying trend second half of the night as vertically stacked low moves offshore by sunrise. Temps seasonably cool tonight with lows in the upper 40s to low 50s. && .SHORT TERM /8 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... *** Summer-like Temperatures Arrive Wednesday *** 4 pm update ... Wednesday ... Vertically stacked low just east of Cape Cod at 12z/8am but ejects seaward quickly with rising heights and northwest flow aloft by midday. Thus any cloudiness across Eastern MA at sunrise quickly erodes and/or moves offshore with abundant sunshine for the afternoon. Warming temps aloft to +14c at 850 mb and +21c at 925 mb yields surface temps at least 30C/86F. Although with boundary layer mixing beyond 850 mb highs will make a run at 90 in many locations. However humidity will be low with dew pts only in the mid to upper 40s. Not as warm along the South Coast including Cape Cod and the Islands...where winds will bend to the southwest off the cooler ocean waters. Wed night ... Dry, tranquil weather with mid level ridge and associated anticyclonic flow continuing to build across the region from the west. Dry airmass in place along with diminishing winds and mostly clear skies will allow temps to fall into the 50s...except 60-65 in the urban areas. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Very warm Wed/Thu/Fri with highs well up into the 80s except cooler immediate coast at times * Hot Saturday afternoon w/highs mainly upper 80s to the lower 90s * A few showers/t-storms possible Thu night/Fri but best chance Sat afternoon/evening ahead of cold front * Turning much cooler Sun and especially Mon along the coast Details... Wednesday night...Other than a low risk for a spot shower/t-storm across the interior during the evening dry weather is expected behind a weak cold front. Low temps will only fall back into the 50s in most locations with 60 to 65 in some of the urban centers. A touch of patchy fog may develop in the typically prone locations toward daybreak. Thursday...Upper level ridging across the Southeast U.S. continues to nose into southern New England. This will result in plenty of sunshine and with warm mid level temps, highs again should reach well into the 80s in most locations. However, gradient will be weaker allowing for sea breezes to develop on the immediate Eastern MA coast including Boston by early afternoon. High temps will still likely reach well up into the 70s to near 80 in this region before sea breezes develop and temps fall a bit. Should remain dry given lack of forcing and upper level ridging nosing into this region. Thursday night and Friday...A shortwave will lift northeast into northern New England Thu night/Fri. While the best forcing will to our north, a few showers/t-storms are possible with the best chance across western and northern MA. Certainly not expecting a washout though and the majority of the Thu night/Fri will be dry. Still looks like a warm afternoon with temps into the 80s, but it may be cooler across Northeast MA depending on location of backdoor cold front. Saturday...A hot day with westerly flow and 850T near 16c. This should yield highs in the upper 80s to lower 90s for most locations. Dewpoints into the 60s will make it feel somewhat muggy. Pre-frontal trough ahead of an approaching cold front may trigger scattered showers/thunderstorms mainly Saturday afternoon and evening. Sunday and Monday...High pressure over the Canadian Maritimes will build south into New England. So despite rather high height fields, northeast low level flow will result in much cooler temps Sun and especially Mon particularly along the coast. && .AVIATION /20Z TUESDAY THROUGH SUNDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Some improvement in vsbys observed over past 1 to 2 hours but cigs slow to rise in onshore flow across much of the area. Believe will begin to rise into the VFR range across the CT River Valley by mid afternoon. Rest of the area should see very slow improvement into at least low MVFR cig range, although there could be a few holdouts below one thousand feet in SE coastal areas. Scattered showers and even isolated thunderstorm or two could develop late this afternoon/evening over portions of RI and SE MA. There could also be scattered showers/isolated thunderstorms that develop during the late afternoon near the Berkshire Crest. Tonight ... Moderate confidence with uncertainty centered around except timing of improving conditions overnight. Showers with isolated thunder focused across Western portions of MA and CT. Isolated lighter showers elsewhere. Mainly MVFR all terminals except Coastal MA. Showers dissipate with sunset and cigs and vsby improve after 06z. Wed ... high confidence. Any leftover MVFR cigs at sunrise will be across Eastern MA but quickly lifting to VFR by 15z or sooner. Dry weather and west winds except southwest along the coast. Wed night ... high confidence. VFR/DRY and light sw winds becoming west. KBOS TAF ... Moderate confidence. Some uncertainty on exact timing of improvement but should take place around 06z. KBDL TAF ... Moderate confidence. Some uncertainty on exact timing of improvement but should take place around 03z-06z. Showers should stay west of BDL airspace but will be close and need to watch early this evening. Outlook /Thursday through Sunday/... Thursday...High confidence. VFR conditions other than a few hours of patchy ground fog possible toward daybreak Thu in the typically prone locations. Thursday night and Friday...Moderate confidence. VFR conditions likely dominate but some brief MVFR conditions possible in a few showers/t-storms mainly across the interior. Saturday...Moderate confidence. Mainly VFR conditions but brief MVFR- IFR conditions possible Saturday afternoon/evening in scattered showers and thunderstorms. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 4 pm update ... Tonight ... high confidence except uncertainty on areal coverage of showers and exact timing. Vertically stacked low over the RI waters will slowly drift to Cape Cod by morning. Few light rain showers will accompany this low along with patchy fog. Leftover southeast swell of 3-6 ft continue across the Southeast MA ocean waters. Wed ... high confidence on all weather parameters. Low pressure near Cape Cod at sunrise moves east/offshore by midday with a drying trend and vsby improving to the horizon. Winds become southwest by midday. Wed night ... high confidence. Light southwest winds become westerly. Dry weather and vsby continue. Outlook /Thursday through Sunday/...High Confidence. Winds and seas will remain below Small Craft Advisory thresholds the majority of the period with the exception being Wednesday night. Some brief near shore southwest wind gusts of 20 to 25 knots are likely Wed afternoon...which will result in some choppy seas. In addition, long southwest fetch may bring a period of 5 foot seas across our southern waters Wednesday night which may require headlines. && .FIRE WEATHER... 4 pm update ... Wednesday ... High temperatures soaring well into the 80s to near 90 in most locations will result in minimum afternoon RH values dropping to between 20 and 30 percent. A few hours of westerly wind gusts of 20 to 25 mph are anticipated. Given this morning`s rainfall and marginal criteria, will probably fall short on the need for fire weather headlines especially given many locations are near full green-up. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Air Quality Alert from 11 AM to 11 PM EDT Wednesday for MAZ020>024. RI...Air Quality Alert from 11 AM to 11 PM EDT Wednesday for RIZ003- 004-006>008. MARINE...Small Craft Advisory for hazardous seas until 4 AM EDT Wednesday for ANZ254-255. && $$ SYNOPSIS...Nocera NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...Frank AVIATION...Frank/Nocera MARINE...Frank/Nocera FIRE WEATHER...Nocera

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