Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 150829 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 429 AM EDT Fri Sep 15 2017 .SYNOPSIS...
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Scattered showers and a few isolated thunderstorms are possible this afternoon into early evening, with mainly dry conditions during the remainder of today. 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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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***Scattered showers and isolated thunderstorms return later this morning and afternoon*** A few bands of showers continue to linger across portions of the region as seen on latest NE regional 88D radar loop early this morning. Since 06Z, low clouds have moved in and visibility has lowered 2 miles or less mainly along the S coast and islands, higher inland terrain and normally prone valley locations. Expect temps to bottom out in the 60s, mildest along the immediate coast. Once the low clouds and fog break this morning, will see a bit of sun through mid and high clouds. With broad mid level trough lingering across the region, with cyclonic flow and cold pool aloft, should see some convection fire up during the max heating of the day. CAPE values to reach up to around 1000 j/kg across inland areas but will be in a window from mid to late afternoon. PWATs will be about 1.5 to 1.6 inches, not extraordinarily high but could see a few brief downpours in any convection that develops. Will also be rather sultry with dewpts in the mid- upper 60s across most areas. Depending upon the amount of cloudiness will reflect how high temps get. At this point, should reach up to the 70s to lower 80s, warmest across E interior Mass and the lower CT valley, rather close to where the higher CAPE values are forecast. Something to keep an eye on.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
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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.
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&& .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Big Picture... Longwave pattern shows upper ridge in place over the Eastern USA with a trough over the Western USA. There is general agreement among the model mass fields that this pattern lingers through the 7-day period. Weak southern stream shortwave over the Gulf Coast, best seen at 250 mb, amplifies as it moves east. This generates a weak southerly channel that moves Jose northward over the weekend. Model mass fields are similar through Sunday. The GGEM jumps faster to the north and east by Monday while the ECMWF is somewhat slower. Meanwhile, the projected track of the eye combined with an uncertainty of 250 miles either side of the track means the eye could travel to anywhere between the DELMARVA Peninsula and a point 240 miles NW of Bermuda by Tuesday afternoon. Great uncertainty and low confidence. Confidence is high through the weekend, falling to low by Tuesday due to uncertainty in the track of Jose. Details... Saturday through Monday... High pressure in place over the weekend with a stalled front northeast over Maine. Light flow over the region Saturday and Sunday, then light east flow on Monday. RH cross sections show a layer of moist air between 800 and 900 mb Saturday and Sunday but no deep layer moisture. Monday is a transition day, but still shows no deep layer moisture. Precipitable water values are on the low side of 1.5 inches. So scattered or widely scattered showers possible, with most of the day dry. Humidity levels remain noticeable with dew points around 60 or in the lower 60s. Mixing is forecast to reach 850 mb each day, supporting max temps around 80 or in the lower 80s. The increased east flow Monday may suppress temps into the 70s. Dew points suggest min temps around 60 or in the lower 60s. Tuesday through Thursday... Much uncertainty in the track of Jose, and on that track hangs much of our expected weather and timing. Given a northward track as noted above, we would expect at a minimum rough surf along the South Coast and the Islands. A track farther offshore might still bring strong gusty Northeast wind to the Islands and Outer Cape as well as a few showers. A track closer to shore would mean greater wind and rain impacts covering a broader part of Southern New England. Also timing uncertainty, as shown by the faster GGEM and slower ECMWF. Current forecast expects Jose to pass offshore near 40N/70W on Wednesday. Wind and rain effects from Jose are possible Tuesday and Wednesday, with locally heavy downpours favored on Cape Cod and Islands. Fair weather Thursday. We will mention chance pops Tuesday and Wednesday except likely pops on Cape Cod and Islands. && .AVIATION /09Z FRIDAY THROUGH TUESDAY/...
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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/... Through Today...Moderate confidence. MVFR-IFR conditions in the morning should improve to mainly VFR by midday. May see some low clouds, patchy fog and MVFR conditions linger along the S coast into the afternoon. Will also see briefly lower conditions in scattered showers/isolated thunderstorms with brief heavy rainfall possible. Tonight...Moderate confidence. Any leftover showers end this evening. Otherwise, will see return of MVFR-IFR conditions in low clouds and fog. Local LIFR CIGS/VSBYS are also possible if fog becomes dense around or after 06Z. Saturday...Moderate confidence. Again, will see MVFR-IFR conditions in low clouds/fog early, then dissipating by around mid morning to midday, except may linger along the immediate S coast into the afternoon. Low risk for scattered showers/isolated thunderstorms mainly across N CT/RI possibly into S coastal Mass Sat afternoon. KBOS Terminal...Moderate confidence in TAF. 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/... Saturday through Tuesday... 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. Visibility will be reduced in areas of fog, locally dense at times, mainly during the nighttime and early morning hours each day. Chance of a few near shore thunderstorms this afternoon/evening. Outlook /Saturday Night through Tuesday/... As Jose moves north, he will transmit increasing swell northward into the Southern New England waters this weekend and early next week. Swell values reach 3-5 feet Saturday and 5-7 feet Sunday to Tuesday. Much of this is focused along the South Coasts of RI and Mass, but spreads to the east coast of Cape Cod Tuesday. Seas 5-6 feet arrive on the southern outer waters Saturday and build to 10-16 feet on the outer waters Tuesday. Seas closer to shore will trend to 5-10 feet toward Tuesday. East to northeast winds will increase early next week with 35-40 knots between 850 and 1000 mb on the ECMWF and 35-50 knots on the GFS. We will show light winds over the weekend, trending to 25-34 knots on Tuesday. Much of this depends on the track of Jose, which has plenty of time to change over the next several days.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/EVT NEAR TERM...EVT SHORT TERM...EVT LONG TERM...Belk AVIATION...Belk/EVT MARINE...Belk/EVT

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