Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 300557 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 155 AM EDT THU JUN 30 2016 .SYNOPSIS...
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Dry and warm weather is on tap for the region today. A cold front moves over the region on Friday into early Saturday, a few thunderstorms are possible. High pressure builds in behind the front and prevails through early next week.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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155 am update... Cold front still hung up along the southeast New England coast. This has allowed areas of fog to develop across portions of southern RI/SE MA, which was locally dense in spots. Widespread dense fog continued to affect MVY and ACK, where a dense fog advisory is in effect through 6 am. Should see conditions improve near daybreak, as cold front slowly pushes southeast allowing somewhat drier air to work in from the northwest. Other areas of very localized ground fog may develop in the typically prone locations toward daybreak, but will be short-lived. Low temps will mainly be in upper 50s to the lower 60s, except middle 60s in the urban heat island of Boston.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/... Dry weather expected through this period, although our region will only be on the edge of a high pressure to our south. The main limitation will be the lack of moisture. Seasonable temperatures expected. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... HIGHLIGHTS... * Scattered showers and thunder Friday/Saturday from passing front * Cooler and less humid for Sunday into July 4th Holiday * Summer heat is possible by mid next-week OVERVIEW... The 12Z guidance is in good agreement for the medium range, however, it has begun to diverge beginning on Monday into next week. Upper low south of Hudson Bay will rotate through the mean trough and pass through eastern Canada by the close of the weekend. The latter of which will send a cold front across the area Friday into Saturday morning. Behind this low, the GFS continues to keep stationary front south of the region, whereas the EC less amplified allowing for mid- level ridge to build over southern New England. This difference has resulted in a wide temperatures spread amongst the guidance. Otherwise GFS bring stationary front well north of the Mid-Atlantic and with riding low pressure could see widespread rainfall. This seems to progressive compared to UKMET and CMC so have continued the trend with the EC keeping front and thus precip chances south of the region. DAILIES... Friday into early Saturday... Interesting weather set-up for Friday for southern New England. Potent low south of Hudson Bay will drag a cold front across the Northeast. Appears that the front will move through during the overnight hours with the a prefrontal trough approaching during the day on Friday. Guidance shows good southerly flow out ahead of approaching systems which help increase the moisture potential. CAPE values are over 1000 J/KG per the GFS and its even shown on the conservative EC. 0-6 KM shear values are also on the increase to 40 kts by late Friday afternoon. So with this amount of instability, shear and moisture with approaching pre-frontal trough cannot rule some strong thunderstorms across southern New England. This is also supported by mid-level lapse rates near 6 C/KM and High K and TT levels. Expect precip to develop from west and move eastward through the day. Anticipate showers and thunderstorms to be able to maintain themselves during the overnight hours as cold front approaches. Guidance still shows a good amount of elevated instability per MUCAPES near 700 J/KG at 06z as well as steepening lapse rapes as 850 mb temps continue to fall during the overnight hours. PWAT values will be near 1.3-1.5 inches which is 1 to 2 standard deviations above normal. Therefore believe the main threat will be heavy rain within any of the stronger storm. Still cannot rule out gusty wind and small hail. This timeframe is something to watch over the next few guidance cycles. Saturday into 4th of July... Cold frontal system will be offshore by Saturday allowing for a pleasant weekend. Still could see an isolated showers across the eastern half, especially if the front slows down. However most of the guidance shows very little mid-level moisture by 12z. Temperatures on both days will be in the low to mid 80s with very low humidity. Monday temperatures looks to be a bit tricky as EC still show mid- level ridge over the region with southwesterly flow. The GFS is still showing a more northwest flow keeping 850mb temps cooler. Because of the spread in the guidance, decided to use a model blend to split the difference. Temps on July 4th could reach into the mid to upper 80s. Luckily the humidity will be low keeping it a comfortable holiday. Tuesday and beyond... Still a spread in the guidance for Tuesday. The GFS continues to push stationary front north of the Mid-Atlantic bringing precip to the region. This is not wholly supported by the ensembles both the GEFS and EC. Will keep a slight chance for now but believe that Tuesday will remain generally dry. Appears that temperatures will begin to increase on the Tuesday into Wednesday as 850mb temps increase ahead of next approaching system. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/... Today...High confidence. IFR-LIFR conditions across the Cape/Islands should burn off between 8z and 11z, but may persist a bit longer across the ACK terminal. Otherwise, VFR today with sea breezes developing by early afternoon along the immediate eastern MA coast by afternoon. Tonight...High confidence in VFR conditions. May see some localized patchy fog develop late in the typically prone locations. Friday...Moderate confidence. A broken deck of clouds should overspread the region from southwest to northeast. Greatest risk for MVFR CIGS will be south of the MA turnpike. Potential for scattered showers and thunderstorms should increase as the day wears on, but uncertainty on timing and locations. KBOS Terminal...High confidence in TAF today and tonight. ESE sea breeze should kick in by early afternoon. KBDL Terminal...High confidence in TAF today and tonight. Outlook /Friday Night through Monday/... Saturday into Monday...High confidence. VFR.
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&& .MARINE...
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Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/...High confidence. Winds and seas will remain below small craft advisory thresholds through this period. Main concern will be for areas of fog, which may be locally dense at times tonight across the southern waters. Outlook /Friday Night through Monday/... High confidence. Quiet boating weather expected. Winds and seas should 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. Seas may reach 5 feet but low confidence at this time. This front will result in showers and thunderstorms, which will reduce visibilities at times. Nearshore waters on Saturday and Sunday may be a bit gusty.
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&& .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 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...
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CT...None. MA...Dense Fog Advisory until 6 AM EDT early this morning for MAZ023-024. RI...None. MARINE...None.
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&& $$ SYNOPSIS...Belk/Dunten NEAR TERM...Frank SHORT TERM...Belk LONG TERM...Dunten AVIATION...Frank/Dunten MARINE...Frank/Dunten FIRE WEATHER...Staff

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