Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261850 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 250 PM EDT FRI AUG 26 2016 .SYNOPSIS...
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A cold front moves off the New England coast this evening. High pressure then builds over Northern New England, bringing dry weather for much of the weekend. Another cold front sweeps across New England Sunday night and Monday. 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 /THROUGH TONIGHT/...
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Through this evening... A cold front is moving through our area with scattered showers found south and east of a Boston-Hartford line. CAPE on the southern/warm side of the front reached 1500-2000 J/Kg. Other stability parameters are more marginal. This suggests a limited potential for thunder in RI and SE Mass until the front moves through. Tonight... Cold front should move offshore by midnight. Dew points are in the 70s ahead of the front and mid 60s behind, so expect the air to become a little more comfortable. Clearing skies already in Western MA will spread across all of Southern New England early tonight. Also expect winds to become light in the interior. Clear skies and light winds and dew points in the mid 60s should allow min temps to reach the mid and upper 60s most places, and low 70s Cape/Islands and urban spots.
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&& .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
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High pressure builds over New England with center along the Canadian border. This will bring a light wind inland and sea breezes along the coast. Dew points will continue to lower with readings near 60. Temps at 850 mb will be in the mid teens, so max sfc temps should reach the mid to upper 80s, with coolest temps along the coastline. The center of high pressure shifts east a little Saturday night, but fair skies and light winds remain in place over Southern New England through the night. With light wind and dew points lingering near 60, expect min temps roughly 60 to 65.
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&& .LONG TERM /SUNDAY THROUGH FRIDAY/...
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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... 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.
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&& .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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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 Night/... Through this evening... High Confidence. A cold front moves across the region. Scattered showers will affect RI and SE Mass with brief MVFR cigs near 2500 feet and vsbys near 4 miles. But most of the time will be VFR. Winds will be southwest ahead of the cold front and northwest behind. Gusts near 20 knots ahead of the cold front and 15 knots behind. Tonight...Moderate-High Confidence. Generally VFR with clearing skies and northwest winds becoming light. Radiational cooling will allow the more prone areas to develop fog patches with IFR/LIFR cigs and vsbys after midnight. Saturday...High Confidence. VFR. Light north winds, with seabreezes developing along both coasts. Saturday night...High Confidence. VFR. Light variable wind. Patchy fog after midnight in the usual prone locations with IFR/LIFR cigs/vsbys through sunrise. KBOS Terminal...VFR. Sea breeze likely around 15Z Saturday. High confidence in TAF. KBDL Terminal...VFR. High confidence in TAF. Outlook /Sunday through Wednesday/... Sunday...High Confidence. VFR. E-SE wind up to 10-15 kt at the NE Mass coastal terminals Sunday afternoon. Patchy fog 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 Night/...High confidence. Cold front moves across the waters early tonight. High pressure builds over New England Saturday. Winds and seas expected to remain below small craft advisory thresholds through Saturday night. Gusty southwest winds early tonight shift northwest, then become light north Saturday. Local seabreezes likely Saturday near shore. Light variable wind Saturday night. Seas 4 feet or less through the period. Outlook /Sunday through Wednesday/... Saturday night and Sunday...High Confidence. Winds 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...WTB/EVT NEAR TERM...WTB/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/EVT MARINE...WTB/EVT

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