Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 310727 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 327 AM EDT WED AUG 31 2016 .SYNOPSIS... Offshore high pressure will draw warmer and more humid weather into New England today. A cold front over the Great Lakes sweeps across New England tonight and Thursday. This will bring scattered showers and a few thunderstorms. High pressure will bring dry and seasonable weather Friday, then we will have to closely monitor a tropical system which will likely be lifting north along the eastern Seaboard this weekend into early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Offshore high pressure will bring a southwest surface flow to New England. Dew points will be on the rise, but limited cloud moisture until late in the day so clouds should mostly be mid and high-level. Stability parameters are marginal and synoptic forcing weak. Expect sunshine through increasing mid and high clouds, rain-free most of the day. Best chance for showers will be after 4 pm in areas west of Worcester. Temps at 850 mb will be 15-17C which would support max sfc temps in the mid to upper 80s. With enough sun these temps can be realized, but the increasing clouds may limit max temps to the low to mid 80s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Shortwave trough over the Great Lakes with a 90-knot jet across Nrn New York and Northern New England. This trough will swing southeast across the St Lawrence Valley tonight and into New England Thursday. The right entrance region of the jet will supply synoptic support as it moves overhead later tonight and Thursday. Precipitable water values will climb to 1.75 inches, while stability parameters remain marginal. All of this may be enough to generate scattered showers and a few thunderstorms. By Thursday the focus for these showers and storms will be in RI/SE Mass where the upper jet forcing is strongest. Dew points in the mid to upper 60s should hold min temps tonight in the mid 60s to lower 70s. Cloud cover and scattered showers/tstms will hold max temps lower than their full potential. Max temps of 75 to 80 seem reasonable. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... HIGHLIGHTS... * Scattered showers and thunderstorms into Thursday * Dry weather and seasonable temps into the Holiday weekend * Rough surf and rip currents could be an issue through the period due to swells from distant TD eight and TD nine OVERVIEW... The 12z guidance is in overall agreement synoptically, still some issues with timing from Thursday cold front. Also we continue to watch TD nine as the latest GFS brings it just a bit to close for comfort. Focusing on the cold front, guidance continues to slow down the frontal passage compared to yesterdays run pushing the front through late Thursday rather than Thursday morning. This lines up better with the ensembles. High pressure then builds late Friday into Saturday. Uncertainty then increases for Sunday into Tuesday with TD nine. The 12z GFS still keeps TD nine a contender for SNE. The CMC and UKMET also keeps it around, however both indicate that it is a very diffused/weak system. The 12z EC pushes it out to sea, but because of the strong block it retrogrades back to SNE on Labor day. Most of these solutions indicate just tropical rains for SNE, where the GFS could bring some wind issues. Still a large spread in all of the guidance so will continue to trend with ensembles and keep a close eye on this system. DETAILS... Friday into Saturday...High Confidence. Upper level trough axis will remain over the region on Friday resulting in a cold pool aloft moving overhead. 500 mb temps near - 14 to -16C would result in another round of showers with possible thunder. The GFS is a bit more aggressive on the convection potential than the EC, as it is indicates steep lapse rates and MU CAPE values over 500 J/KG. Believe this is something to watch in the coming days. Within any strong storm, hail would be the main issue. High pressure will move in behind the upper level trough. This will allow for sunny skies and dry weather. Temperatures on each day will be near average for this time of year with highs in the upper 70s to low 80s. Sunday into Tuesday...Low confidence. Initially thinking is that high pressure and mainly dry weather will prevail for this time period. As mentioned above, we`ll have to continue to watch TD nine as it develops and move into the Eastern Seaboard. Some of the deterministic models have shifted the system west and north keeping it a player for southern New England. The latest ensembles are indicating a very low risk. We`ll have to see how the high pressure over the region and upper level ridge will drive this upcoming tropical system in the upcoming days. Right now, where the system is progged to develop and move, anticipate in another round of rough surf and rip current issues for the beaches Labor day weekend. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through Thursday...Moderate to high confidence. Today...High confidence. Mainly VFR. A few showers or a t-storm possible in the interior during the late afternoon with brief MVFR conditions. Southwest winds below 20 knots. Tonight and Thursday...Moderate confidence. Mainly VFR cigs but with scattered showers/t-storms will may briefly lower cigs/vsbys to MVFR. A cold front moves through the region during Thursday with southwest winds shift out of the northwest behind the front. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Thursday Night through Sunday/... Thursday...High confidence. Mainly VFR conditions. Low probability of SCT -SHRA/ISOLD TSRA, resulting in brief MVFR conditions. Friday into Sunday...High confidence. VFR. May need to watch TD nine for aviation impacts across the Islands. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday/...High confidence. SE swell will conitnue to bring 4-5 ft seas to the outer waters through the period with highest swell across eastern waters where we have SCA for hazardous seas. Winds will gust to 20 knots today, but remain below 25 knots through the period. Outlook /Thursday Night through Sunday/... Moderate confidence through the period as there is a large uncertainty on TD eight and nine`s impact for southern New England waters. Conditions should be below SCA for Thursday however increasing southerly swell from TD eight may impact the southern waters into Friday. Saturday into Sunday, seas will begin to increase as TD nine will approach the Eastern Seaboard. Right now appears seas will build to at least 8 feet by Sunday, resulting in rough surf for the Holiday weekend. There is a low potential that seas could build 15 feet. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert from 11 AM this morning to 11 PM EDT this evening for CTZ002. MA...None. RI...None. MARINE...Small Craft Advisory for hazardous seas until 4 PM EDT this afternoon for ANZ250-254. && $$ SYNOPSIS...WTB/Dunten NEAR TERM...WTB/Dunten SHORT TERM...WTB LONG TERM...Dunten AVIATION...WTB/Dunten MARINE...WTB/Dunten is the U.S. government's official web portal to all federal, state and local government web resources and services.