Area Forecast Discussion
Issued by NWS Boston, MA

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179 FXUS61 KBOX 011401 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1001 AM EDT FRI JUL 1 2016 .SYNOPSIS... An approaching cold front will bring numerous showers and scattered thunderstorms this evening, and a few of them may become strong to severe with locally heavy rainfall. High pressure builds in behind the front and prevails through much of next week, resulting in warming temperatures and dry weather. && .NEAR TERM /UNTIL 5 PM THIS AFTERNOON/... 10 AM update... SPC mesoanalysis shows environment is destabilizing with SBCAPES 500-1000 J/kg south of the Pike. However, deep layer moisture is lacking as shown by lower KI values and MLCAPES are still nil. As deeper moisture increases this afternoon, expect a few widely scattered showers and thunderstorms to develop across SNE per hi- res guidance, but do not expect much organization. Main show will occur this evening as mid level trof and increasing shear move in from the west and some of the hi-res guidance is suggesting an organized line of showers/t-storms will move across the region. With sunshine through early afternoon, temps will reach the low to mid 80s away from the south coast. It will be humid as dewpoints rise well into the 60s by later this afternoon. && .SHORT TERM /5 PM THIS AFTERNOON THROUGH 6 AM SATURDAY/... ***High confidence in numerous showers and scattered thunderstorms with locally heavy rainfall roughly between 5 pm this evening and 2 am Saturday morning*** ***Low confidence on whether some storms become strong to severe*** Tonight... Shortwave and impressive height falls will sweep across New England this evening. Strong forcing noted as 0 to 6 km shear values increase to between 35 and 45 knots. Despite the loss of daytime heating, instability may actually increase during the evening as mid level lapse rates steepen with the height falls. Models show 500 to 1000 J/kg of CAPE persisting through 06z tonight. As a result we are fairly confident in numerous showers and scattered thunderstorms, with locally heavy rainfall this evening. Brief poor drainage street flooding is possible. In addition, dangerous cloud to ground lightning is a big concern given its the start of the holiday weekend. The biggest uncertainty is if some of these storms become strong to severe. As usual this is not clear cut since instability is marginal, but strong forcing will try to make up for it. It is a very delicate balance, but there certainly is some potential for some strong to severe thunderstorms. Highest risk is across western MA/northern CT where better instability is expected, but cannot be ruled out across the rest of the region given the strong dynamics. If any storms are able to become strong to severe, biggest threat will be for localized wind damage, but there is a secondary concern for hail given cooling aloft. Lastly, a low risk exists for an isolated tornado given SREF/NCAR ensembles showing pretty good probabilities for 0 to 1 km helicity of 150+ and LCL/s below 800 meters. So to summarize, high confidence in showers and scattered t-storms this evening with localized heavy rainfall and dangerous cloud to ground lightning. Confidence is low on whether some storms become strong to severe since instability is marginal, but it is certainly something to watch closely given strong dynamics. && .LONG TERM /SATURDAY THROUGH THURSDAY/... * Cooler temps Saturday, then increasing temps through next week * High pressure brings dry weather for much of next week Overview...Quiet pattern continues through next week starting with upper level ridging in the center of the country and an upper trough in the NE. The upper level pattern flattens out a bit by Monday with weak ridging continuing across the middle of the country. Models are in good agreement on the synoptic pattern and will use a blend of available guidance for this forecast. High pressure builds into the region Sunday and continues through much of next week. Temperatures...Aside from slightly cooler temperatures Saturday, behind the cold front, temperatures will gradually warm into next week. By the middle of next week, temperatures will be in the upper 80s to lower 90s. Precipitation...Dry weather continues throughout southern New England through next week. No precipitation is expected from Saturday onwards. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... FORECASTER CONFIDENCE LEVELS... LOW...LESS THAN 30 PERCENT MODERATE...30 PERCENT TO 60 PERCENT HIGH...GREATER THAN 60 PERCENT Short Term /through Tonight/... Mainly VFR conditions expected through mid afternoon. MVFR to IFR conditions in low clouds/fog patches will likely develop late this afternoon/early this evening south of the MA pike and may affect all areas for a time this evening. Otherwise, main concern will be scattered thunderstorms mainly between 21z and 06z, resulting in briefly lower conditions. A few may become strong to severe. Low cigs/vsbys may linger across southeast New England after 06z, with patchy fog possible elsewhere. Improvement expected by 12z in most locations. KBOS TAF...Moderate confidence in TAF. Main thunderstorm risk between 01z and 06z. KBDL TAF...Moderate confidence in TAF. Main thunderstorm risk between 22z and 04z. Outlook /Saturday through Tuesday/... Saturday...High confidence. Any lingering MVFR conditions will improve to VFR quickly Saturday morning. Sunday through Tuesday...High confidence. VFR. Low probability of sea breezes developing each afternoon. && .MARINE... Low level jet will result in southerly wind gusts increasing to between 20 and 25 knots this afternoon and evening. We did issue a small craft advisory for our northeastern waters, where 4 to 5 foot seas should develop. Across the rest of the region, think wind gusts will be just below criteria but close enough to monitor closely. Biggest concern for mariners is the risk for a few strong thunderstorms this evening, with 40+ knot wind gusts possible. Outlook /Saturday through Tuesday/... High confidence. Mainly quiet boating weather expected. Winds and seas remain below SCA criteria throughout the period. && .FIRE WEATHER... Hit or miss showers and thunderstorms are possible this afternoon and tonight. However, widespread precipitation looks to be nil over the next 7 days. High pressure and dry conditions appear to take hold of the region Saturday, lasting through the much of next week. Much of this time will be less humid with RH values dropping close to 30 percent for much of this time. Winds overall appear to be light during this period. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 2 PM this afternoon to 4 AM EDT Saturday for ANZ250. && $$ SYNOPSIS...Frank/RLG NEAR TERM...KJC SHORT TERM...Frank LONG TERM...RLG AVIATION...Frank/RLG MARINE...Frank/RLG FIRE WEATHER... is the U.S. government's official web portal to all federal, state and local government web resources and services.