Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 311102 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 702 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/...
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7 AM Update...Increased cloud cover over the area due to the latest satellite trends. Otherwise, the forecast is on track so only minor changes were made. 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.
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&& .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... * Showers and thunderstorms ending Thursday night * Dry weather and seasonable temps going into the holiday weekend * Rough surf and rip currents likely due to swells from distant tropical systems * Potential impacts to southern New England with TD 9 Model update...Unlike the agreement shown by Monday night`s model runs, the 31/00Z models show much less agreement, not just with each other, but with previous runs of the models. The greatest concern is with TD 9 and its track of course and there is a definite westward shift in all of the models and ensemble runs. This shift would bring TD 9 closer to the southern New England coast. Will have more on this below. Otherwise, there are some very minor timing differences on the cold front moving offshore Thursday night and discrepancies in the strength and extent of high pressure building into the NE US into the beginning of the weekend. Thursday night through Saturday...Could see a few lingering showers and thunderstorms, particularly across eastern MA and RI Thursday evening as the cold front moves offshore. These should come to an end fairly quickly. High pressure starts to build in from the Great Lakes and continues to build into the weekend. GFS/NAM runs indicate we may see a few diurnal showers along the E coast of MA on Friday, ECMWF keeps the region dry. Mostly quiet weather during this time with seasonable temperatures. Rough surf and rip currents are expected on all southern New England beaches, thanks to swells from Gaston, TD 8, and TD 9. Sunday through Tuesday...The main concern here will be the progression and track of what is currently known as TD 9. It is expected to become a named storm (likely Hermine) early this morning. Currently it is over the Gulf of Mexico and forecast to cross northern Florida and move back into the Atlantic in the next 2- 3 days. Models, including the 00Z runs of the ECMWF and GFS as well as their respective ensembles, have trended with a more westward track for TD 9. The overall consensus still keeps the system just offshore of southern New England, bringing a glancing blow. However, the current set up of a building upper level ridge into the east coast and another upper level ridge over the Atlantic are making this a complicated forecast for the models and thus for the forecasters as well. Despite the general consensus track, individual models and ensemble members do vary quite a bit with the track with some bringing it much too close to southern New England for comfort and others taking it off safely to the south and east. Bottom line: Watch TD 9, official NHC forecasts, and forecasts from this office through the end of this week and into the holiday weekend to be prepared. But, nothing is set in stone at this point and forecasts will change between now and the weekend. && .AVIATION /12Z 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 night...High confidence. Mainly VFR conditions. Low probability of SCT -SHRA/ISOLD TSRA across E MA/RI, resulting in brief MVFR conditions. Friday...High confidence. VFR. Saturday and Sunday...Low confidence. Likely VFR conditions, but much will depend on the eventual track of TD 9. && .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 continue 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/... Thursday night...High confidence. Winds and seas remain below SCA criteria for the most part. There is a possibility of a few 5 foot seas on the outer waters. There is also a low probability of a few scattered showers and thunderstorms over the waters. Friday...Moderate confidence. Winds and seas will begin to increase in response to swell from the many tropical systems that will be in the Atlantic by Friday. Winds should remain below SCA criteria, but advisories will likely be needed for higher seas and rough surf. Saturday and Sunday...Low confidence. Lots of uncertainty for this time period as forecast will depend largely on track of TD 9. This portion of the forecast is worth monitoring through the holiday weekend as confidence is highest in some impact on the waters from this storm. && .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 5 AM EDT Thursday for ANZ250-254. && $$ SYNOPSIS...WTB/RLG NEAR TERM...WTB/RLG SHORT TERM...WTB LONG TERM...RLG AVIATION...WTB/RLG MARINE...WTB/RLG

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