Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 291420 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1020 AM EDT WED JUN 29 2016 .SYNOPSIS... Scattered showers will come to an end early this morning, followed by a warm and humid afternoon with the low risk of a few strong thunderstorms across eastern New England. Dry and seasonable weather follows tonight and 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 PM THIS EVENING/... ***Low risk for a few strong thunderstorms across eastern New England this afternoon*** 1020 AM Update... CAPE values were generally 500-1000 J/kg this morning, and will only increase now that the clouds were not as extensive over the western half of southern New England. Some cumulus clouds already starting to form, a sign that scattered showers are not far behind. Expecting clouds over eastern MA and RI to dissipate some between now and noon. Made a few updates to the forecast, mainly to the PoP and sky forecasts for the next few hours. Otherwise, the forecast is on track. For the rest of this morning and into this afternoon, mainly dry weather will prevail. Surface winds turning west southwest should allow skies to become partly sunny allowing highs to recover into the lower to middle 80s away from the immediate coast. Dewpoints in the 60s will also make it feel rather humid today, so a summerlike day is on tap. While the vast majority of the day will be dry, the main uncertainty is if we are able to generate a few thunderstorms this afternoon across eastern New England as a cold front crosses the region. The highest risk for this will be across eastern MA, where sea breeze interaction might assist in development. We should see 1000+ j/kg of Cape develop across eastern New England with mid level lapse rates increasing to between 6 and 6.5 c/km. In addition, 0 to 6 km shear values will be on the order of 40 knots. These are all favorable parameters for a few strong to marginally severe thunderstorms. However, there is one big negative factor which is an abundance of mid level dry air. This may prevent any convection from developing and its possible we end up with just low topped showers. So to sum up, there is a low risk for a few strong to marginally severe thunderstorms across eastern New England this afternoon, but too much mid level dry air may prevent this from occurring. Highest risk might be on a subtle sea breeze front, which may allow for a bit better moisture to pool. Something will certainly have to keep a close eye on today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... Tonight... If any isolated showers/t-storms are able to develop across eastern New England this afternoon, they should quickly diminish early this evening with the loss of daytime heating. Skies should become mostly clear allowing low temps to drop into the upper 50s to lower 60s in most locations. Light winds will likely allow for patchy ground fog to develop in the typically prone locations overnight, which may be locally dense. && .LONG TERM /THURSDAY THROUGH TUESDAY/... HIGHLIGHTS... * High pressure brings dry weather Thursday * A cold front brings showers and thunderstorms Friday/Saturday * High pressure brings dry weather for the remainder of the holiday weekend Overview...Relatively quiet pattern continues with broad upper level ridge over the western U.S. and broad upper troughing over the eastern U.S. The ridging pushes into the center of the country by early next week. Models are in good agreement on the synoptic pattern and will use a blend of available guidance for this forecast. Low pressure in Ontario moves into Quebec, pulling a cold front from the Great Lakes through southern New England Friday or Saturday (consensus is a bit faster than the ECMWF). This will bring another chance of showers and thunderstorms to the area. High pressure builds into New England from the Great Lakes for the remainder of the holiday weekend, before moving offshore Tuesday. Temperatures...Aside from slightly cooler temperatures Thursday and Saturday, behind two cold fronts, temperatures will gradually warm into early next week. By Tuesday, temperatures could be reaching into the upper 80s to lower 90s. Precipitation...The only shot of rain in the long term forecast is showers and thunderstorms with the cold front Friday or Saturday. Timing looks to be late Friday into Saturday morning but there are still some differences in the timing. This will ultimately determine how widespread showers and thunderstorms are and the severity of those storms. Models are indicating quite a bit of instability, despite the timing. The GFS is more unstable, but has earlier timing, with showers and thunderstorms occurring during the late afternoon and evening on Friday. The ECMWF is overall less unstable, but shows a burst of instability early Saturday morning. Will include thunder in the forecast for this time period. This period also bears watching for the potential for severe weather, again depending on timing. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/... Today...Moderate to high confidence. MVFR-IFR conditions should improve to VFR by afternoon in most locations, but lower Cigs/Vsbys may linger across the islands. Sct showers should come to an end early this morning. This will be followed by mainly dry weather, but there is the low risk for a few strong thunderstorms this afternoon across eastern MA. Tonight...Moderate to high confidence. Mainly VFR early this evening except for this risk for low clouds/fog patches across the Cape/Islands. Across the rest of the region, will likely see localized patchy ground fog develop late in the typically prone locations. Meanwhile, other locations may see conditions remain VFR. KBOS Terminal...Moderate confidence. Periods of MVFR CIGS is possible through mid morning otherwise, mainly VFR. May see a sea breeze for a few hours later this morning and into the afternoon, but timing and duration is uncertain. Lastly, there is a low risk of a t-storm in the vicinity of the terminal this afternoon. KBDL Terminal...Moderate to high confidence. Outlook /Thursday through Sunday/... Thursday...High confidence. Mainly VFR conditions. Any lingering MVFR conditions Wednesday night will improve quickly to VFR. Light and variable winds will result in sea breezes developing on both coasts. Friday and Saturday...Moderate confidence. Mainly VFR conditions and dry weather. Scattered showers and thunderstorms may result in brief periods of MVFR conditions. Sunday...High confidence. VFR. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tonight/...High confidence. Winds and seas will remain below small craft advisory thresholds. Main concern will be for areas of fog, which may be locally dense at times this morning and again this evening across our southern waters. Also, there is a low risk for an isolated strong thunderstorm this afternoon near the adjacent coastal waters. Outlook /Thursday through Sunday/... High confidence. Mainly quiet boating weather expected. Winds and seas remain below SCA criteria throughout the period. However, they will increase as a cold front approaches and then crosses over the coastal waters sometime late Friday to Saturday. This will result in showers and thunderstorms, which will reduce visibilities at times. && .FIRE WEATHER... Hit or miss showers and thunderstorms will occur today, with another shot for thunderstorms Friday and 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 too 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 until 11 PM EDT this evening for RIZ006>008. MARINE...None. && $$ SYNOPSIS...Frank/RLG NEAR TERM...Belk/Frank/RLG SHORT TERM...Frank LONG TERM...RLG AVIATION...Frank/RLG MARINE...Frank/RLG FIRE WEATHER...Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.