Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 282324 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 724 PM EDT TUE JUN 28 2016 .SYNOPSIS... A slow moving cold front will bring scattered showers and a few thunderstorms into Wednesday, with the bulk of the activity occurring tonight. This front will push offshore Wednesday night. High pressure then brings dry seasonable weather for Thursday. Another cold front may bring more showers and thunderstorms Friday or Saturday. Dry weather returns for the remainder of the holiday weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Showers and thunderstorms remain to our west this evening. Latest Hi-Res guidance as well as 18z GFS/NAM show precip moving into the area by 03z lasting into the overnight hours. Still cannot rule out the potential for thunder as showalters are below 0 combined with TT above 48. Limiting factor could be that MUCAPE values are barely reaching above 150 J/Kg during the overnight hours. However as we approach closer to 12z, then begin to rise quickly to 300 J/Kg. PWAT values remain high over the region, close to 1.5 inches. So within any stronger storm could see heavy downpours. Insert heavy rain into the forecast as there is good convergence within the boundary layer. This appears to stay fast and true this evening. Still modest moisture convergence at the 925 mb level but not as strong as out west. Therefore will continue to hold off on any watch product. May need to watch the second half of the region tonight as LLJ begins to increase. This may sprout more showers across the region between 09-12z then what guidance is currently showing. Otherwise southerly flow will continue to increase dewpoints tonight. This will keep the muggy conditions going which may result in widespread fog across the area. Uncertain on how low vsbys will get due to the approaching precip and mixing aloft as LLJ begins to increase. So will hold off on any dense fog product. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Wednesday...A surface cold front will sweep across the region later in the day. While the vast majority of the day will be dry for most locations, there is a low risk for a few strong thunderstorms developing in the afternoon ahead of this front. Strong thunderstorms will be dependent upon getting enough sunshine to increase instability, and having enough mid level moisture lingering to permit storms to develop. While thunderstorms remain uncertain, the highest risk will be across Eastern MA/RI where moisture will be a bit deeper. Wednesday night...Drier weather develops behind a departing cool front. Humidity drops to more comfortable levels, but not by a lot. Seasonable temperatures through this period. && .LONG TERM /THURSDAY THROUGH TUESDAY/... HIGHLIGHTS... * Dry with seasonable conditions on Thursday * Scattered showers and thunder Friday/Saturday from passing front * Cooler and less humid for Sunday into July 4th Holiday OVERVIEW... The 12Z guidance is in good agreement for both the medium and long range. Still a few minor issues because of timing but overall have a high confidence in forecast trends. Upper level trough will remain the dominate features across the Northeast as a subtropical ridge builds across the Southeast, while a moderate upper ridge continues over the West. Trended the overall pattern towards a blend of the guidance as well as the ensemble means, which has remained consistent over the past few runs. DAILIES... Thursday... Cold front will move offshore on Thursday resulting in high pressure pushing into the region. A few sct cu will develop as there will be some left over mid-level moisture but overall a pleasant day is on tap. Sea breeze development will keep coastal conditions cooler but temps will be in the 80s across the interior. Friday into Saturday... Cold frontal system will approach from the west late Friday into Saturday. Return flow across will help pool in higher dewpoints, especially Friday night. So cannot rule out the potential for fog development. Otherwise sct showers with isolated thunderstorms are possible on Friday. The attention is more towards Friday night into Saturday. Still a timing difference as the GFS is faster pushing the front through by 12z Saturday. However the EC is about 12 hours slower, which could result in more widespread thunderstorms. In fact, the conservative EC show surface based CAPEs around 1000 j/kg, with increasing 0-6km shear and steepening mid-level lapse rates. This may result in a few strong storms Sat morning. Something to continue to watch in case guidance slows down the timing of the frontal passage. Sunday and beyond... Cold frontal system will be offshore by Saturday night allowing a pleasant Sunday. Potent shortwave will move through the flow on Sunday which will keep upper level trough over the region and cool down temps aloft. 700 mb temps are near 1 to 2 standard deviations below normal, indicating the cooler air aloft. Stationary front will stall across the Ohio valley and into the Mid-Atlantic keeping Southern New England on the dry, relatively cooler side. Less muggy conditions will prevail as the hot, muggy conditions will stay south of the front. These conditions will prevail into Tuesday. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... Tonight...Moderate confidence. Conditions lower to MVFR-IFR thresholds as boundary layer cools with an abundance of low level moisture. Scattered showers and thunderstorms also expected with main risk between 03z and 12z. Wednesday...Moderate confidence. MVFR-IFR conditions should improve to mainly VFR by afternoon as low clouds/fog patches dissipate. Low risk for a few strong thunderstorms Wed afternoon, mainly Eastern MA/RI. Wednesday night...High confidence. Mainly VFR conditions. Low risk for MVFR conditions in patchy fog. Light and variable winds. KBOS TAF...High confidence in TAF trends. Moderate confidence in timing. KBDL TAF...High confidence in TAF trends. Moderate confidence in timing. Outlook /Thursday through Sunday/... Thursday...High confidence. Mainly VFR conditions. Sea breeze for the coastlines. Friday and Saturday...Moderate confidence. Mainly VFR conditions and dry weather. Scattered showers and thunderstorms may result in brief periods of MVFR conditions especially Fri night into Sat. Sunday...High confidence. VFR conditions will prevail. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/...High confidence. Winds and seas will generally remain below small craft advisory thresholds through this portion of the forecast. South to southwest wind gusts of 20 knots are expected at times with 2 to 4 foot seas across the open waters. Southeast swell may increase seas to near 5 feet Wednesday night across the outermost coastal waters south and east of Nantucket. Low confidence in this happening. Main concern is for areas of fog tonight into Wed morning across the southern waters. May also see a few thunderstorms with brief heavy rain overnight tonight. Outlook /Thursday through Sunday/... High confidence. Quiet boating weather expected. Winds and seas remain below SCA criteria throughout the period. Could see a few gusts near 20 kts on friday ahead of an approaching cold front. This front should cross waters by Saturday. This will result in showers and thunderstorms, which will reduce visibilities at times. && .FIRE WEATHER... This Weekend into Next Week... Hit or miss showers and thunderstorms will occur tonight into Wednesday, with another shot for thunderstorms on Friday night. However, widespread perception looks to be nil over the next 7 days. High pressure and dry conditions appear to take hold of the region late Saturday lasting into next week. Specifics are still to hard to nail down, but it looks like the area will be less humid and a bit cooler but dry during this time frame. RH values could drop close to 30 percent between Sun into Wed. Winds overall appear to be light during this period. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...Air Quality Alert from 11 AM to 11 PM EDT Wednesday for RIZ006>008. MARINE...None. && $$ SYNOPSIS...Belk/Dunten NEAR TERM...Belk/Dunten SHORT TERM...Belk LONG TERM...Dunten AVIATION...Belk/Dunten MARINE...Belk/Dunten FIRE WEATHER...Dunten

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