Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 230703 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 303 AM EDT MON MAY 23 2016 .SYNOPSIS... We are in between weather systems today, with fair dry weather during much of the daylight hours. Coastal low pressure moves up the coast this evening through Tuesday bringing showers and thunderstorms. A significant warmup will occur Wednesday, continuing into next weekend. Scattered showers or thunderstorms are possible from Thursday into next weekend, especially over western sections. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Closed upper low is in place along the Northeast and Mid Atlantic coasts, although the most significant instability remains from PA to North Carolina through the day before moving into Southern New England this evening. Heating by the sun will create sufficient mixing to reach near 800 mb, where temps will support max surface values in the mid to upper 70s. A light northeast surface wind will keep temperatures near the Mass East Coast in the upper 50s and 60s. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... Tonight... Instability moving up from Eastern PA may reach western CT this evening and bring a few showers. The more significant feature will be low pressure surface and aloft that will move north toward New England. This feature will bring colder temps aloft over our area, supporting greater instability. Upper jet moving around the low will be just east of MA with the lift-supporting left exit region over RI and eastern MA. For both reasons, expect showers moving up from the south tonight with sufficient instability for a couple of thunderstorms too. Will use likely POPs, but on the lower side of this range. Clouds and the northeast flow off the water point to min sfc temps near the dew point, in the lower 50s. Tuesday... Core of the upper low moves over RI and Eastern MA. Similarity among the models gives some confidence to this positioning. Core of the cold pool aloft also moves over our area, so instability will linger through the day. Concern remains for the chance of a couple of thunderstorms due to the unstable airmass. We will mention slight chance of thunder. POPs will be at high-end chance or low-end likely much of the day. Tuesday will be much cloudier than today so more limited mixing, probably to 925 mb or 900 mb. Temps at these levels would support max surface temps in the 60s. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Highlights... * Significantly warmer Wednesday into next weekend * Scattered showers and thunderstorms Thursday into next weekend, especially over western sections. Overview and Model Preferences... Very good agreement in the latest guidance suite in moving a persistent upper low toward the Maritimes by late Wednesday afternoon. Strong ridging over the north Atlantic edges west over the southeast USA late this week. This will mean more summer-like conditions late this week into next weekend. With the increasing heat and humidity, also expecting the possibility for diurnal showers and thunderstorms, each day. Subtle, but significant, differences in the details Friday into next weekend. The predictability of these details is rather low, so will favor a consensus approach, for now. Details... Wednesday... Brief ridge of high pressure to our south takes over, leading to downslope air flow, drier conditions, and more summer-like temperatures away from the coast. There could be seabreezes, but it appears the synoptic flow could be just strong enough to prevent lower temperatures along parts of the MA east coast. Cape Cod and the islands, as well as Cape Ann, however, will likely remain as cool as the south coast of New England, where southwest winds should prevail. Thursday through Sunday... This still appears to be a prolonged period of summer-like heat and humidity, especially away from the coasts. The questions to be answered during this portion of the forecast are: where will a frontal boundary be between Thursday and Friday, and how quickly will it move? A scenario can be seen where we wind up on the cold side Friday, which would mean lower temperatures and a greater risk for showers. Diurnal showers, and perhaps some thunderstorms, are expected through most of this period. The position of this front will have a large impact on chances, and is one of the more uncertain aspects of this forecast. Will keep a chance for showers in the forecast until this critical detail can be better worked out. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday/... Today...Moderate-High Confidence. VFR most of the day. Areas of IFR ceilings/vsbys in patchy early morning fog, especially in Greater Springfield and in the lowlands of Southeast MA. Showers may develop late in the day in CT, and toward evening along the South Coast. This could bring local MVFR vsbys at that time. Tonight...Moderate Confidence. Showers and widely scattered thunderstorms move across Southern New England. This will bring a few periods of MVFR cigs and vsbys. Also MVFR/IFR cigs/vsbys in fog especially in RI and SE Mass. Tuesday...Moderate Confidence. Showers and widely scattered thunder will continue. Areas of MVFR/IFR in showers and fog areas. Conditions may improve to mainly VFR especially in CT and Western MA late in the day. KBOS TAF...Greatest uncertainty is in timing of showers for this evening and tonight. Because of this any mention of showers has been tagged as vicinity rather than directly mentioned. KBDL TAF...Greatest uncertainty is in timing of showers for this evening and tonight. A couple of showers could reach the airport between 5 PM and 8 PM, but more likely to occur after 8 PM. Outlook /Tuesday Night through Friday/... Wednesday...High Confidence. Mainly VFR. Thursday...Moderate Confidence. Mainly VFR. Scattered MVFR in scattered showers and thunderstorms, mainly west of KLWM-KORH-KIJD. Friday...Moderate Confidence. Mainly VFR. Scattered MVFR in scattered showers and thunderstorms. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today...Moderate Confidence. Low pressure moves up the coast from Virginia and the Carolinas. Most of the day will be fair with North winds turning from the Northeast. Speeds will be 15 knots or less. Seas will slowly subside through the day with lingering 5 to 7 foot seas subsiding through the day. Small craft advisory for hazardous seas is in effect, mostly for the outer waters, through the day. Tonight and Tuesday...Moderate Confidence. Coastal low pressure moves across the waters. This will bring showers and widely scattered thunder with lower visibility in showers and fog. Winds will remain 15 knots or less, and seas will mostly be less than 5 feet. A few 5 foot readings could show up on the southern outer waters Tuesday. Outlook /Tuesday Night through Friday/... Wednesday into Friday...High Confidence. High pressure briefly builds over the waters. Mainly quiet boating weather is expected with winds and seas below Small Craft Advisory levels. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas until noon EDT today for ANZ231-251. Small Craft Advisory for hazardous seas until 11 PM EDT this evening for ANZ250-254-255. Small Craft Advisory for hazardous seas until 8 AM EDT this morning for ANZ256. && $$ SYNOPSIS...WTB/Belk NEAR TERM...WTB SHORT TERM...WTB LONG TERM...Belk AVIATION...WTB/Belk MARINE...WTB/Belk is the U.S. government's official web portal to all federal, state and local government web resources and services.