Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 241320 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 920 AM EDT TUE MAY 24 2016 .SYNOPSIS... Scattered showers and few embedded thunderstorms will focus primarily across Western portions of MA and CT this afternoon as low pressure slowly moves across southeastern New England. An upper level high pressure ridge will then bring very warm to borderline hot weather to most of the region Wednesday through Saturday, except for times of cooler temperatures 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 the cold front. && .NEAR TERM /UNTIL 8 PM THIS EVENING/... 915 am update... Not much change from previous forecast. Showers and isolated thunder focused across northern and western MA including western CT. This convection is on the nose of a short wave trough moving across the region. On the backside of this feature drier mid level air is beginning to overspread the area and is supporting more low top showers and drizzle moving onshore to RI and Eastern MA. Moving forward into the afternoon...northeast winds and low clouds will contiue across RI and Eastern MA leading to mist/drizzle and scattered low top showers. Thus not a washout but damp and dreary. Farther west into CT and Western-Central MA...away from the northeast onshore flow low clouds give way to higher ceilings along with a few breaks of sunshine and scattered showers. All model guid including the SSEO and NCAR ensembles suggest any limited instability /250-750 j-kg/ will be confined to Western portions of CT and MA. This is where showers will be most numerous this afternoon and early evening along with the risk of a few thunderstorms. Although NOT expecting any strong storms given lack of instability and shear. Cool temps today especially along the coast given northeast winds...clouds and light precip. Milder inland away from the onshore flow along with a few breaks of sunshine. Previous forecast on track so no major changes with this update. Earlier discussion below. ==================================================================== Bulk of scattered showers with brief heavy rain and were mainly to the northwest of a Boston to Providence line with the steadiest of activity in Western MA. Will see a brief break in the action except for a few showers lingering through late morning. Then activity looks to start firing up again later today, with another round of sct showers/isold thunderstorms develop mainly across W MA and N CT this afternoon, but not much in Eastern MA/RI given cool stabilizing marine layer. 00Z short range model suite continue to signal the instability remaining across the region, with total totals up to the lower to mid 50s /more robust on the NAM/, surface based LIs down to zero to -2 and K indices to the lower 30s. Also noted CAPES on order of 400-500 J/kg this afternoon across this area so, along with H5 temps down to -18C to -19C in the core of the cold pool as it crosses the region, so there is a low risk for isolated small hail reports in Western MA/Northern CT. Convection should begin to wane toward sunset, but will linger across N and W MA into N central CT into the evening. With the onshore winds continuing, albeit light, temps will only rise to around 60 along the immediate coast, but look to reach to the upper 60s to near 70 across the CT valley. && .SHORT TERM /8 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... Tonight... As the H5 upper low and the associated surface reflection continue to move slowly NE tonight, will see some leftover isolated showers/thunderstorms into this evening before finally ending. With light and variable winds in place along with wet ground in many places, will likely see patchy fog redevelop overnight. Also, cooler, drier air will not rush in with light pres gradient in place, so temps will not fall back too far tonight. Expect lows in the 50-55 degree range. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... 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...Closed upper level low lifts northeast of our region allowing for rising heights/warmer mid level temps. More importantly, surface winds will turn to the west which makes a huge difference in afternoon high temps this time of year. Given 850T between 13c/14c and plenty of late May sunshine, high temps should be in the mid to upper 80s for most including Boston, as any sea breezes that develop along the Eastern MA coast will be overcome by increasing gradient by afternoon. A few locations may even touch 90. It will be a bit cooler on the south coast/Cape/Islands, but still should see highs well into the 70s to near 80. Dry weather will dominate Wednesday, but there is a low risk of a spot shower/t-storm during the afternoon/early evening across the interior. Limiting factors though will be dry mid levels and lack of low level forcing. 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 /13Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 920 am update ... no major changes from 12z TAFs. Lowest cigs/vsbys will be over RI and Eastern MA along with mist/drizzle and a few showers. Inland across CT and Western-Central MA cigs/vsbys in the MVFR range but showers will be more numerous across this area along with low risk of a few afternoon thunderstorms. Earlier discussion below. ==================================================================== Today...Moderate confidence. Mainly IFR conditions along the coastal plain this morning in low clouds and patchy fog. These conditions will likely improve to low end MVFR this afternoon, except for the Cape and Islands. Across the interior...much of the region will see ceilings lower to MVFR levels by mid to late morning and these conditions mainly continuing through the afternoon. Scattered showers/isolated thunderstorms shifting focus to mainly Western MA and Northern CT by afternoon. Tonight...Moderate confidence. Isolated SHRA/TSRA lingers across central and N MA through this evening, then ending. Patchy fog lingers along E coastal MA with MVFR-IFR VSBYS, while fog redevelops away from the coast with areas of MVFR VSBYS. Light/vrbl winds. KBOS TAF...Moderate confidence. IFR conditions this morning probably improve to low end MVFR this afternoon. Scattered showers mainly northwest of the terminal most of the day. KBDL TAF...Moderate confidence. Conditions will lower to MVFR this morning and persist into the afternoon. Scattered showers at times with a low risk of an embedded t-storm this afternoon/early evening. Outlook /Wednesday through Saturday/... Wednesday and 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. Through 12Z...Moderate confidence. Expect E-NE winds less than 15 kt and seas below 5 ft. Visibility reductions in showers, widely scattered thunderstorms and patchy fog. Today...Moderate Confidence. E-NE winds less than 15 kt. Seas will build up to 5-6 ft across the outer waters from Cape Cod southward, mainly in S-SE swells this afternoon. Local visibility restrictions in scattered showers, isolated thunderstorms and patchy fog. Winds will back to N during the afternoon. Small crafts have been issued for portions of the outer waters. Tonight...Moderate Confidence. N-NW winds as low pressure moves offshore, but remaining light. E-SE swells will remain at 5-6 ft through around midnight, then will slowly subside toward daybreak. Small crafts will continue for portions of the outer waters. May see local visibility restrictions in patchy fog. Low risk of isolated showers early. Outlook /Wednesday through Saturday/...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... Wednesday...High temperatures soaring well into the 80s 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. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas from 1 PM this afternoon to 4 AM EDT Wednesday for ANZ254-255. Small Craft Advisory for hazardous seas from 3 PM this afternoon to 1 AM EDT Wednesday for ANZ256. && $$ SYNOPSIS...Frank/EVT NEAR TERM...Frank/Nocera/EVT SHORT TERM...EVT LONG TERM...Frank AVIATION...Frank/Nocera/EVT MARINE...Frank/Nocera/EVT FIRE WEATHER... is the U.S. government's official web portal to all federal, state and local government web resources and services.