Area Forecast Discussion
Issued by NWS Boston, MA

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562 FXUS61 KBOX 301209 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 809 AM EDT SAT JUL 30 2016 .SYNOPSIS... Most of today will be dry across the area, with increasing clouds west to east during the afternoon. A series of weak low pressure areas will bring periods of showers across southern New England tonight into early Tuesday, bringing scattered showers. A few thunderstorms are also possible each afternoon and evening. The low will move offshore during Tuesday. High pressure will build out of northern New England, with a return to dry conditions for the middle and latter portion of next week. Temperatures will warm up toward the end of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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750 AM Update... Area of dense fog along the S coast of Mass, Cape Cod and the islands has tended to dissipate after sunrise, except for some low clouds lingering around the mid and outer Cape as well as Nantucket at 12Z. Elsewhere, skies were mainly mostly sunny with some high clouds moving across. Temps have risen to the mid 60s to mid 70s at 12Z. Noting some patchy showers moving slowly E-NE in the mid level flow across S central NY into NE PA as seen on latest NE regional 88D radar imagery. Also noting area of mid and high clouds across central and western NY/PA that will slide slowly E toward the region, probably pushing into western areas by midday or early this afternoon. This is in good agreement with the previous forecast. Have updated near term forecast to bring conditions current. Previous Discussion... Believe nearly entire forecast area will remain dry through the daylight hours today, although clouds will be on the increase from west to east during the afternoon. Slight chance of showers developing along and west of the CT river valley during the late afternoon. Max temperatures under partial sunshine will likely reach near to slightly above normal. Have gone with a model blend for the dewpoint, which lowers values about 5 to 8 degrees from Friday across most of the region outside the south coast zones where dewpoints may only drop one or two degrees.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... What looks to be a series of short wave trofs moving about a slowly progressive long wave upper trof will initiate a series of weak waves along the front stalled south of the area for tonight through Sunday. The pattern looks conducive to at least modest overrunning in an environment depicted with deep moisture from Bufkit soundings and precipitable waters around 1.5 inches. Due to at least some of the area in a drought, we are taking a conservative approach on both POPs and QPF forecasts. Also, models appear to be influenced by some convective feedback. The focus for showers is expected to be across the western half of the area tonight. For Sunday, have the POPs highest north and west where the models suggest the better forcing. With K indices in the lower 30s, cannot rule out isolated thunder this evening and again Sunday late afternoon and evening. Clouds will keep temperatures elevated some tonight with lows in the mid to upper 60s across most of the region. The combination of clouds and generally onshore flow is expected to keep temperatures in the mid to upper 70s on Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Highlights... * Unsettled Sunday night through early Tuesday with scattered showers, mainly in northern and western areas * Isolated thunderstorms possible across central and western areas Monday afternoon/evening * Dry weather expected Tuesday afternoon through Friday, with a warming trend toward the end of next week Overview and model preferences... 00Z model suite showing a bit better agreement through a good portion of the long term forecast period, but do note timing differences toward the end of next week as one would expect that far out in the forecast. GFS/ECMWF ensembles also showing pretty good continuity through most of the period. Models maintain a slow moving open H5 trough across the northeast Monday into Tuesday, with weak low pressure waves moving along a stalled front just off the southern New England coast. The trough will finally push seaward on Tuesday, with a slow improving trend during the day. Large high pressure will build out of southern Ontario to the Great Lakes later Tuesday, slowly pressing eastward with dry conditions Wednesday and Thursday. The high will work offshore on Friday, with an approaching cold front late in the day. There are some timing differences amongst the model suite with this approaching front, so lower confidence with that portion of the forecast. Used a blend of available model and ensemble guidance for this portion of the forecast. Details... Sunday night through early Tuesday... Expect a couple of low pressure waves to slowly ride along a stalled front just off the southern New England coast into early Tuesday. This will keep a good low to mid level moisture feed across the region thanks to an E-SE wind flow that will slowly back to NE late Monday night into Tuesday as the final low pushes offshore. The best chance for showers will continue Sunday night and Monday across central and western areas. Have kept 50-60 pct chance POPs across western areas, but will still see scattered activity pretty much everywhere. With the onshore flow, albeit light, will tend to hold off any organized instability. However, can not rule out elevated instability that will linger across central and western areas Monday afternoon and evening, so kept mention of isolated thunderstorms there. Will see the final low push offshore early Tuesday as it becomes better organized. The last of the showers should start to dissipate during the morning. With the mainly onshore flow, expect temperatures to run several degrees below seasonal normals. Expect highs mainly in the 70s, though a few spots may touch 80 over the southern CT valley both days. Tuesday afternoon through Friday... Models continue to signal high amplitude H5 ridge building E out of central Canada into Quebec. This will bring large surface high pressure from southern Ontario and the Great Lakes slowly eastward during this timeframe. Will see dry conditions through most if not all of this period. Temperatures will return to seasonal levels on Wednesday, then will warm further as winds become more S-SW as the high crests across the region, then slowly pushes offshore. Expect highs Thu mainly in the 80s, then in the mid 80s to around 90 on Fri. Humidity levels will also slowly increase. Some model solution variance with the approach of a cold front out of the Great Lakes to Hudson Bay later Friday. Have pretty much a dry forecast going, though did mention slight chance POPs late in the day and Fri night mainly near and N of the Mass Pike. && .AVIATION /12Z SATURDAY 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 Sunday/... Today...High confidence. IFR CIGS lingering on the outer Cape and Nantucket, but should move offshore by 15Z. Otherwise mainly VFR. Expect mid to high clouds to increase west to east during the afternoon. Tonight...Moderate confidence. VFR ceilings are expected to prevail with areas of MVFR visibility and ceilings in vicinity of some showers tonight. More widespread MVFR conditions expected in areas of fog along southeast coastal areas. Light winds with sea breezes developing along both the south and east coasts by afternoon. Sunday...Moderate confidence. Becoming mostly VFR ceilings with some MVFR ceilings in vicinity of showers. Pockets of IFR ceilings and visibilities due to morning fog across southeast coastal sections. KBOS TAF...High confidence. Generally VFR conditions expected through the period, although occasional MVFR ceilings possible in vicinity of showers and fog late tonight/early Sunday. KBDL TAF...High confidence. VFR conditions expected through the period except patchy fog may develop late tonight. Outlook /Sunday Night through Wednesday/... Sunday night through Monday night...Moderate confidence. Mainly VFR. Scattered showers possible at any time. Cannot rule out a heavier shower or thunderstorm with local MVFR-IFR conditions, mainly from central Mass into N Connecticut Monday afternoon and evening. Areas of late night/early morning fog with IFR CIGS/VSBYS both nights. Tuesday...Moderate to high confidence. Mainly VFR. Scattered showers across the CT Valley through N central and NE Mass Tuesday morning, then improving. May see brief local MVFR conditions in any showers. Patchy late night/early morning fog with MVFR-IFR conditions Tuesday night in the normally prone areas. Wednesday...High confidence. VFR. Just a few areas of MVFR possible in patchy late night/early morning valley fog and in the usual fog prone locations.
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&& .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. Winds and seas are expected to remain below Small Craft Advisory thresholds through Sunday. Areas of visibilities 1 to 3 nm in areas of late night/early morning fog are expected. Outlook /Sunday Night through Wednesday/...High confidence. Sunday night...Expect light E-SE winds with seas 3 ft or less. Visibility restrictions in scattered showers and late night/early morning fog patches. Monday through Tuesday...Winds will back to E-NE with gusts up to 20 kt, mainly across the eastern waters Monday night/Tuesday. Seas build up to 4 ft over the open waters mainly over the eastern waters to south of Nantucket. Visibility restrictions in patchy late night/early morning fog both night, and in scattered showers Monday and Monday night, slowly improving on Tuesday. Isolated thunderstorms possible off the RI coast Monday into Monday evening. Tuesday night and Wednesday...NE winds continue, gusting up to 20 kt on the open waters Tuesday night. Winds shift to E later Wednesday but remain light. Local visibility restrictions continue Tuesday night in patchy fog, mainly after midnight through mid morning. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...EVT/Thompson NEAR TERM...EVT/Thompson SHORT TERM...Thompson LONG TERM...EVT AVIATION...EVT/Thompson MARINE...EVT/Thompson is the U.S. government's official web portal to all federal, state and local government web resources and services.