Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 260718 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 318 AM EDT FRI AUG 26 2016 .SYNOPSIS... A cold front swings through our region today, bringing some showers and a few thunderstorms. Seasonable and dry for this weekend. Chance of scattered showers and thunderstorms for Monday. Dry weather Tuesday into Wednesday. Wet weather possible late next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Continuing to monitor the progress of showers over central and upstate NY. So far, still not seeing much lightning, at the time of this writing. Latest mesoanalysis showed marginal lapse rates and meager instability. Thinking it will take some sunshine this morning to really pose a threat of thunderstorms. It will be a race for the clouds to depart the coastal plain of southeast New England, but this is the most likely area for thunderstorms given the later timing of this cold front. Should we not get enough sunshine, then the risk for thunderstorms will be diminished. Most of the guidance, and especially the last few runs of the HRRR, hinted at the idea of showers across southeast MA early this morning. Latest radar data bearing that idea out, although the guidance likely too bullish on measurable rainfall chances. However, this does give confidence in the timing presented by the guidance this morning. Expecting a cold front to cross the CT River around noon, then reach the east coast of MA toward 8 PM. Very warm start to the day, with overnight low temperatures not too much below the normal high temperatures. It will not take much sunshine to boost temperatures into the 80s, with some locations even approaching 90 degrees. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Tonight... Cold front moves offshore by around midnight. Humidity levels diminish noticeably. Expecting clearing skies and winds shifting from the northwest. Seasonable temperatures. Saturday... High pressure starts to build in from the Great Lakes. Plenty of sunshine and light north winds to start. Seabreezes likely to develop along both coasts. even so, still expecting max temperatures to be at or slightly above normal. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... */ Highlights... - Seasonable and dry weekend, fantastic weather! - Shower and thunderstorm chances for Monday - Banking dry weather for early-mid week, wet-weather mid-late week - Low confidence forecast for next week especially with Invest-99L */ Discussion... Forecast hinges upon the morphology of synoptic features towards the later-half of the week into Labor Day Weekend with respect to Invest- 99L (AL99). Continued struggles with forecast model performance in handling N/E Pacific disturbances into the W CONUS is subsequently leading to alterations in the ridge-trough-ridge pattern extending from the Gulf of Alaska region into the Central and E CONUS. Notably atmospheric teleconnections have exhibited some waffling within the last few model runs, especially into the beginning of September. Do still believe through the complications that the H5 High presently across S/E CONUS and Mid-Atlantic will only shift and perhaps weaken with the presence of AL99. This yields the opportunity for pacific- origin energy through the consensus forecast of near-zonal flow for the early- to mid-week period to have a greater influence S across the N CONUS as AL99 makes its approach. Then it becomes a question of how such energy from the N interacts with the consensus forecast of AL99 into the SE CONUS towards the Mid-Atlantic. After a certainly pleasant, comfortable weekend with seasonably dry weather with likely onshore influences, looking at wet-weather for Monday with scattered showers and thunderstorms. Not overwhelming confident. Timing of associated cold frontal passage in question as is both the availability of moisture and instability. Weak shear profiles as lapse rates are poor. Seemingly still dealing with the lingering influence of high pressure. But if synoptic forcing can come together along with a destabilizing boundary-layer, outcomes are plausible, especially Monday afternoon. Will hold with chance PoPs over much of S New England. Continued low confidence forecast hereafter as deterministic models struggle with individual waves and accompanying influences through the ensemble-weighted near-zonal flow with favorable troughing in the vicinity of the W CONUS. Content with earlier thinking that beyond Monday will be a brief period of high pressure followed by periods of disturbed weather for the mid-late week period. Crucial is whether AL99 is wrapped into expected disturbed weather and N- stream energy late week into Labor Day Weekend to which the majority of guidance keeps offshore. But with some ensemble members that is not the case, and the consensus forecast has exhibited some wobbling as of late, so overall forecast outcomes remain uncertain. && .AVIATION /07Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/... Today...Moderate Confidence, mainly due to timing issues. SCT SHRA/TSRA, with higher confidence over S/E interior S New England terminals. S/SW winds continue with gusts up to 20 kts before shifting out of the NW late. Low-end VFR cigs where cigs develop. However, can not rule out MVFR, with TEMPO MVFR-IFR conditions, within any TSRA and/or +SHRA. Tonight...Moderate Confidence. SW winds shifting out of the W/NW, 10 kts or less. VFR with the possibility of IFR conditions prior to the wind shift over S/E coastal terminals. Will also need to monitor whether light winds and radiational cooling can yield interior fog issues. Saturday...High Confidence. VFR. Light north winds, with seabreezes likely to develop along both coasts. KBOS Terminal...prevail -SHRA overnight. Towards 15z onwards will be closely watching areas S/W for TSRA development. SW winds overall with gusts around 20 kts during midday Friday into afternoon. KBDL Terminal...low-end VFR to MVFR possible overnight. Clearing into Friday morning, potentially, will be monitoring for TSRA development around and E of the terminal midday into afternoon. Outlook /Saturday Night through Tuesday/... Saturday night into Sunday...High Confidence. VFR. Winds turning E/SE Sunday, potentially breezy late with SCT mid-high cloud. Monday...Moderate Confidence. Chance of SHRA/TSRA. Timing of outcomes remains unclear at this time, could see some morning activity followed by afternoon storm development. S/SW winds, breezy with gusts up to 20 kts, backing out of the W/NW towards morning. Tuesday...Moderate Confidence. Will prevail VFR with winds turning out of the W/NW. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/...High confidence. Winds and seas expected to remain below small craft advisory thresholds through Saturday. Gusty southwest winds today shift northwest tonight, then become light north Saturday. Local seabreezes likely Saturday near shore. Outlook /Saturday Night through Tuesday/... Saturday night into Sunday...High Confidence. High pressure. Winds gradually veering out of the S/SE into Sunday, becoming breezy late. Waves remaining below 5 feet. Monday...Moderate Confidence. Winds turning out of the S/SW ahead of a sweeping cold front. There is the potential for gusts up to 20 kts. This in addition to shower and thunderstorm activity, mainly considering the near-shore waters. Expect the cold front to sweep the waters towards the later half of the day, into evening, at latest overnight. Wave influence per weather may be minimal, but of greater concern is swell associated with Gaston. Waves in excess of 5 feet by evening. Tuesday...Moderate Confidence. Cold front pushing out to sea as winds back W/NW. Swell continuing from Gaston with wave heights up to 6 feet on the outer waters. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Sipprell NEAR TERM...Belk SHORT TERM...Belk LONG TERM...Sipprell AVIATION...Belk/Sipprell MARINE...Belk/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.