Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 151808 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 208 PM EDT Fri Sep 15 2017 .SYNOPSIS... Scattered showers and a few isolated thunderstorms are possible today into this evening. Generally dry and seasonable weather is expected this weekend. Hurricane Jose will likely bring high surf and dangerous rip currents this weekend into the middle of next week. Some wind and rain effects are possible, especially across Cape Cod and the Islands. But the full extent of those impacts remains dependent on the uncertain storm track. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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205 pm update... This afternoon southern New England was under a broad mid level trough, and cyclonic flow with a cold pool aloft. Diurnal cumulus development was well underway, with a mix of clouds and sun over the interior and along east coastal MA from Boston to the North Shore. South coastal MA/RI had minimal clouds, although of note was the fog/stratus bank right along the south coastal MA/RI shoreline, as well as around Martha`s Vineyard and Nantucket. This fog/stratus bank is expected to persist thru the afternoon, and some fog with reduced vsbys may drift on land at times thru the remainder of this afternoon. Also seeing isolated to widely scattered showers developing within the area. SPC Mesoanalysis page shows surface-based CAPE of 1000+ J/kg for much of our area. Anticipating further development of scattered showers and isolated t-storms as the afternoon progresses. Precipitable water is around 1.6 inches, not extraordinarily high but could allow for a few brief downpours in any convection that develops. Will also be rather sultry with dewpts in the mid- upper 60s across most areas. Noted at 2 pm dew point at ACK was 70. Temps expected to peak out in the upper 70s to mid 80s for most locales, although some locales impacted by sea breezes may end up somewhat less warm.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Tonight... Some leftover showers/isolated thunderstorms should diminish this evening around or after sunset. Light/variable or calm winds continue so will see set up for development of areas of fog, some of which could be dense especially if there are any breaks in the cloud deck. Saturday... The last of the mid level long wave trough lingers across S coastal areas during the day. May see another round of scattered showers/isolated thunderstorms once again during the afternoon. This will again be dependent upon how quickly the fog and low clouds breaks during the morning. Noting a suppressed area of instability in the vicinity of the leftover mid level trough, with CAPE up to around 800 or so j/kg across N CT into W RI possibly a bit further S. Still have light surface winds. PWATs are forecasted to be lower, however, so not quite as much of a threat for heavy rainfall at this point. Temps look to be a bit milder, mainly in the lower 80s away from the upper 70s to lower 80s away from the S coast. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... 15/00Z guidance suite continues the trend of a more westward track with Jose, even with the ensembles. Still lots of disagreement regarding the timing and strength of Jose among the deterministic runs, especially after Sunday. With the westward shift in track, the threat of a more direct impact from Jose is increasing. Prudence dictates that people in southern New England should pay close attention to later forecasts regarding Jose this weekend. Confidence is high through this weekend, falling to low by Monday night due to uncertainty in the track of Jose. High pressure Sunday starts to break down across our region Sunday night into Monday morning. This could permit some showers to develop Monday afternoon into Monday night. The most likely period of any wind and precipitation impacts from Jose, as of this writing, looks to be sometime Tuesday into Wednesday. These sorts of details will likely change with time through this weekend. Have low confidence in the forecast for next Thursday, which will greatly depend on the exact track and timing of Jose. One thing is known with certainty: our region will be at a moderate to high risk for dangerous rip currents later this weekend into early next week. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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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 Saturday/... 18Z Update... Through This afternoon...High confidence. Along the Cape and Islands, VFR except periods of IFR cigs possible at times due to a fog/stratus bank that is in place along the south coastline. For the remainder of the area, VFR with localized MVFR cigs/vsbys possible in scattered showers. Isolated t-storms possible thru sunset that may produce brief heavy rainfall. Sea breezes remain in place thru the remainder of the afternoon. Tonight...Moderate confidence. Any leftover showers end this evening. Diurnal clouds dissipate leaving a period of mostly clear to partly cloudy skies. However areas of MVFR/IFR conditions in low clouds and fog should develop during the overnight. Best chance for IFR conditions would be Cape and Islands. Local LIFR CIGS/VSBYS are also possible if fog becomes dense around or after 06Z. Saturday...Moderate confidence. MVFR/IFR conditions in low clouds/fog early, then lifting/dissipating during the morning. Then VFR thru the afternoon with diurnal cumulus. Low risk for scattered showers during the afternoon, mainly across the interior. KBOS Terminal...Moderate confidence in TAF. Sea breezes expected this afternoon, and again during Saturday. Chance for scattered showers and perhaps an isolated thunderstorm within vicinity of the terminal this afternoon and early evening. KBDL Terminal...Moderate confidence in TAF. Scattered showers and perhaps an isolated thunderstorm approach the terminal this afternoon into early evening. Outlook /Saturday Night through Tuesday/... Sunday and Monday...High confidence. VFR. Patchy MVFR/IFR in fog and low clouds each early morning. Chance of MVFR cigs reaching the South Coast late Monday, depending on the track and speed of Jose. Tuesday...Low confidence. MVFR with areas of IFR in low clouds/rain/fog. Northeast winds with potential for 35 knot speeds. Poor visibility on Cape and Islands in rain and fog.
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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 Saturday/... Today through Saturday...High confidence. Expect winds to remain below 15 kt through the period. Seas 4 ft or less. During this afternoon, fog/stratus bank lingers nearshore and south of south coastal RI/MA, including Cape Cod, Martha`s Vineyard and Nantucket. Chance showers/thunderstorms this afternoon/evening. Then for tonight/Saturday morning and Saturday night, visibility will be reduced in areas of fog, locally dense at times. Outlook /Saturday Night through Tuesday/... As Jose moves north, increasing swell also moves northward into the southern New England waters this weekend and early next week. Much of this is focused along the South coasts of RI and MA, but spreads to the east coast of Cape Cod Tuesday. Mariners are strongly urged to monitor the latest forecasts regarding Jose this weekend into early next week.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/EVT NEAR TERM...Belk/EVT/NMB SHORT TERM...EVT LONG TERM...Belk AVIATION...Belk/EVT/NMB MARINE...Belk/EVT

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