Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 281351 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 951 AM 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 PM THIS EVENING/... 950 AM Update... A few showers remain across southern New England during the mid morning. These will remain hit-and-miss, so will only keep fairly low rainfall chances through the rest of today. Still evaluating thunderstorm potential for later today. Latest mesoanalysis continues to show poor instability across southern New England, with less than 300 J/kg of CAPE. Where the clouds have broken out ahead of a cold front, CAPE values have increased to 500-1000 J/kg. While this is well west of our region, it does indicate the potential which could develop if we can break out from beneath our present cloud deck. Will continue to monitor this aspect. Otherwise, the forecast was mostly on track. Made minor tweaks to reflect observed trends. Previous discussion... While warm advection will continue to result in the risk for a few spot showers, dry weather will dominate the rest of today with bulk of forcing/instability well to our northwest ahead of a cold front. Deep low level moisture will also result in considerable cloudiness at times, but still expect peeks of sunshine especially across southeast New England. High temps will mainly be in the upper 70s to lower 80s, but a few locales may reach into the middle 80s. It will also feel somewhat humid outside with dewpoints well into the 60s, something we have not seen much of so far this month. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... ***Scattered showers/thunderstorms with brief localized heavy rainfall possible between 9 pm tonight and 5 am Wednesday morning but severe weather threat is rather low*** Tonight... Showers and thunderstorms will be on going across Eastern NY early this evening. This activity will attempt to work into western MA/Northern CT by mid to late evening, but should weaken with diminishing instability/poor mid level lapse rates. Still may see some thunder and brief locally heavy rainfall in these locations. Greater threat for scattered showers/thunderstorms with brief locally heavy rainfall may set up across Eastern MA/Eastern CT and RI near or after midnight. This on the nose of a 30 to 40 knot southerly low level jet, MUcapes between 200 and 500 J/kg, and PWATS between 1.5 and 2 inches. Guidance not completely sold on where and if this sets up, but given the above parameters certainly a possibility. Severe weather threat looks rather low given limited instability/timing. Bulk of the activity should be offshore near daybreak. Low temps will mainly be in the 60s and may see some patchy fog develop. Wednesday... The actual surface cold front will sweep across the region on Wednesday. While the vast majority of the day will be dry, there is a low risk for a few strong thunderstorms developing Wed afternoon ahead of the front. Whether or not this activity develops hinges on if enough mid level moisture remains. While this is uncertain, the highest risk is across Eastern MA/RI where moisture will be a bit deeper. We should see 1000+ j/kg of Cape develop across Eastern New England ahead of the front along with 0 to 6 km shear values of 30 to 40 knots. Colder air moving in aloft will result in somewhat steeper mid level lapse rates, but nothing too extreme. The above parameters are supportive for the possibility of a few strong thunderstorms Wed afternoon. However, mid levels of the atmosphere will be drying out and may limit or prevent convection. So in a nutshell, there is a low risk for a few strong thunderstorms Wednesday afternoon with an isolated strong wind/hail threat if dry mid level air can be overcome. Highest risk across Eastern MA/RI between noon and 6 pm. High temps should generally reach into the lower to middle 80s away from the immediate coast. Still somewhat humid with dewpoints in the 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... 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. A cold front will move offshore Wednesday night bringing in slightly cooler but quiet weather for Thursday. Another cold front will move through southern New England Friday or Saturday (ECMWF is a bit faster than the GFS), bringing showers and potentially thunderstorms to the area. High pressure builds into New England from the Great Lakes for the remainder of the holiday weekend. Temperatures...After slightly cooler temperatures Thursday, temperatures will warm into the weekend. The cold front will bring another slightly cooler day Sunday before temperatures warm once again. Overall, temperatures will be right around to a few degrees above normal with highs generally in the 80s and lows in the upper 50s to lower 60s. Precipitation...The only shot of rain in the long term forecast is showers and possibly thunderstorms with the cold front Friday or Saturday. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... Today...Moderate confidence. A mix of IFR and MVFR conditions in low clouds this morning will probably improve to mainly VFR by afternoon. Bulk of scattered showers should also come to an end by mid to late morning. Otherwise, mainly VFR conditions expected the rest of the day. 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 01z and 09z. Wednesday...Moderate to high 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. KBOS TAF...Moderate to high confidence in TAF. KBDL TAF...Moderate confidence in TAF. Outlook /Wednesday Night through Saturday/... Wednesday night and Thursday...High confidence. Mainly VFR conditions. Any lingering MVFR conditions Wednesday night will improve quickly to VFR. Light and variable winds. Friday and Saturday...Moderate confidence. Mainly VFR conditions and dry weather. Scattered showers and thunderstorms may result in brief periods of MVFR conditions. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/...High confidence. Winds and seas will generally remain below small craft advisory thresholds through Wednesday afternoon. South to southwest wind gusts of 20 knots are expected at times with 2 to 4 foot seas across the open waters. Main concern is for areas of fog tonight into Wed am across the southern waters. May also see a few thunderstorms with brief heavy rain overnight. Outlook /Wednesday Night through Saturday/... 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. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/RLG NEAR TERM...Belk/Frank/RLG SHORT TERM...Frank LONG TERM...RLG AVIATION...Frank/RLG MARINE...Frank/RLG is the U.S. government's official web portal to all federal, state and local government web resources and services.