Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261204 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 804 AM EDT FRI AUG 26 2016 .SYNOPSIS...
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A cold front swings through the region today, bringing some showers and a few thunderstorms. Dry and warm conditions through this weekend. There may be some widely scattered showers and thunderstorms late Sunday night into Monday as a cold front crosses the region. Some showers and thunderstorms may linger Tuesday and Wednesday before another front clears through. High pressure noses across the northeast late next week with dry and mild conditions.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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740 AM Update... Area of showers that moved across N central and NW Mass has pushed into S NH as the area moves just N of due E over the last couple of hours as seen on NE mosaic radar imagery. Also noted a few spotty showers that developed across N CT into N RI and S coastal Mass since 11Z. Still not seeing any lightning at this point across northern New England into E NY state. Noting line of showers developing ahead of the cold front lining up from SW of KGFL to N of KBGM to NE of KELM, steadily moving SE since 10Z. Will see more scattered showers/isolated thunderstorms develop with high PWAT line (1.9 to 2 inches) that will push across the region through midday. Noting high launching pad in the temperature department this morning, as overnight lows only dropped to 70 to 75 along the coastal plain, and the mid 60s to near 70 inland. With a lot of mid and high level clouds crossing the region, may delay the warming but think the clouds will tend to thin out by mid to late morning. Something to monitor. Have updated to bring near term conditions current, especially for the timing of the precip into the region later this morning. Previous Discussion... Marginal lapse rates and meager instability continues at 11Z. 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.
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&& .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... * Mild and dry conditions through the remainder of the weekend * Scattered showers and thunderstorms late Sunday night and Monday * A few showers and thunderstorms may linger Tuesday and Wednesday before another front sweeps across * Looking dry and mild late next week Overview and model preferences... Continued summer pattern across North America and beyond with E-W elongated Bermuda-Azores high from the mid Atlantic and SE states over the subtropical Atlantic, stretching further across the southern tier states to off the California coast, while the northern stream steering currents have remain shunted into the northern Plains states to Quebec around 00Z Sunday. H5 heights increase further Saturday night into Sunday as closed high pres builds across with H5 ridging into eastern Quebec. Noting an H5 short wave in the flow trying to push SE into northern New England Monday, bringing a weak cold front with it. Should clear the region Monday night. Models get a bit messy with the evolution of slowly lowering mid level heights around Tuesday-Wednesday timeframe. Appears the 00Z GFS is a bit stronger with another H5 short wave in the steering flow, but the GGEM and ECMWF do show a weaker wave. May see isolated convection mainly around max heating both days, with the better shot on Tuesday. A lot of questions beyond late Wednesday with timing of features in the northern stream flow, but looks like it should be dry and a bit cooler for Thursday. Continue to monitor a tropical wave (99L) as it moves near or N of Cuba. At this point, looks like it will remain out of the northern stream weather picture. Will continue to monitor. Leaned toward a blend of available guidance through Tuesday, then went closer to ensemble guidance for Wednesday-Thursday. This gave good continuity to the previous forecast. Details... Saturday night-Sunday...Looks dry as high pressure crosses New England, heading for the Maritimes late Sunday. Expect highs on Sunday to run 5-10 degrees above seasonal normals for late August, though will be cooler along the immediate E coast with onshore winds. Some clouds will begin to approach the Route 2 area of N Mass during Sunday afternoon. Sunday night-Monday...Cold front slowly approaches in the W-NW upper flow. Most of the energy with the associated N5 short wave remains across northern New England Monday, but could see enough to kick off some isolated showers/thunderstorms mainly during max heating. Noting a thin band of 1.7 to 1.8 inch PWATs cross with this front Monday afternoon/ evening, along with some marginal instability (LIs around zero to -1, Showalter around zero, TQs at 17-18 for elevated convection). Have kept only slight chance POPs going for very spotty convection. Front should push offshore Monday evening. Tuesday-Wednesday...With a weak H5 short wave moving across on Tuesday, along with some marginal instability remaining across the region both days and dewpts mainly in the 60s to around 70 on the S coast, may see some diurnal convection try to develop but will remain spotty both days. Better shot for thunder on Tuesday, but even weaker on Wednesday near the S coast so left thunder mention out for now. Appears another front will cross the region later Wednesday or Wednesday night. Thursday...Not a lot of confidence for this timeframe, though models and ensembles are tending to signal more dry conditions with slightly cooler temperatures. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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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 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 and Sunday...High Confidence. VFR. Light/variable winds Saturday night become E-SE up to 10-15 kt at the NE Mass coastal terminals Sunday afternoon. Patchy fog after 05Z-06Z across normally prone valley locations may bring MVFR-IFR conditions. Should improve by 12Z-13Z. Sunday night-Monday...Moderate Confidence. Mainly VFR. May see widely scattered SHRA/TSRA late Sunday night through Monday with brief local MVFR conditions. S-SW winds may gust up to 20 kt across coastal NE Mass Sunday evening, then diminish. Winds shift to W-NW late Monday/Monday night but remain light. Tuesday...Moderate Confidence. Mainly VFR. May see a few isolated SHRA/TSRA across interior Tuesday afternoon/evening. Light N-NE winds shift to S-SW late in the day.
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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 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 and Sunday...High Confidence. Expect light E-SE winds Saturday night increase to up to 15 kt late Sunday into Sunday evening. May see gusts up to 20 kt on the waters east of Cape Ann. Seas remain below 5 ft. Monday...Moderate Confidence. Winds become S-SW ahead of an approaching cold front. Low risk of gusts up to 20 kt on the southern near shore waters Monday afternoon/evening. May see some showers/thunderstorms with brief visibility restrictions into Monday evening as the cold front pushes across. SE swells from TS Gaston may build to 5 ft on the eastern outer waters Monday night. Tuesday...Moderate Confidence. Winds veer to N-NW but remain light during the day, then shift back to S-SW again Tuesday night ahead of another front. Swells up to 5 or 6 ft across the outer waters from distant TS Gaston.
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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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