Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 150715 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 215 AM EST Sun Jan 15 2017 .SYNOPSIS...
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High pressure maintains dry and seasonable conditions today and Monday. Low pressure from the Plains approaches Southern New England with rain and mild air for Tuesday and Wednesday. This low pressure then redevelops to our east, and moves off Wednesday night. High pressure then builds in with dry and continued mild weather for the end of the week.
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&& .NEAR TERM /THROUGH TODAY/...
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High pressure should move east from the Great Lakes during the day. This will mean another shot of cold air from northwest winds. Expecting increased mixing over the coastal waters, along with a brief pressure gradient increase along the leading edge of the colder air. This will result in gusty winds, particularly across the coastal waters. Mainly clear skies through the day across southern New England. Would not be surprised for some lake-effect clouds to linger around the east slopes of the Berkshires. Near normal temperatures anticipated, with dry weather.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
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HIgh pressure over New England tonight, before moving south to a location just off the Mid Atlantic coast Monday. Mainly clear skies through this period. Near ideal radiational cooling conditions tonight, so favored the coldest guidance for temperatures. Temperatures Monday should be slightly above normal with plenty of sunshine and a light southwest wind.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Big Picture... Hudson Bay upper low retreats north, leaving a large-scale zonal flow for much of the long term. Toward next weekend the large scale a developing Pacific Coast trough and West Atlantic Ridge. In the shortwave scale, Baja California upper low ejects through the Southern Plains Monday and Great Lakes Tuesday, then New England Wednesday. East Coast ridge then builds late week. Contour heights are mostly forecast to be above the climatological average. GFS does show heights briefly near normal Wednesday as the upper trough moves past, but the ECMWF and GGEM are much warmer. Overall this looks like a dry mild week, punctuated by a period of rain Tuesday-Wednesday. Model mass fields are similar through Wednesday morning, then diverge in handling the midweek weather system. They then show a general agreement on high pressure arriving for Friday and Saturday. Confidence for the long term is moderate. Details... Monday Night... Some increase in cirrus, especially across CT and RI, but otherwise fair skies and light winds. This will allow radiational cooling for a portion of the night. Dew points 15 to 30 should allow min temps mainly 20-30. Tuesday-Wednesday... Models are trending slower with the onset of clouds and precipitation. The lower airmass remains dry through midday while mid and high clouds are on the increase. Low level ageostropic flow turns from the north but remains 20 knots or less. Meanwhile temps will have time to climb above freezing in most places. If cold air does linger, it would be most likely in some of the East Slope communities of Northwest MA. There also remains a chance that the combination of slightly stronger drainage flow and evening evaporative cooling could bring a period of freezing rain in Northwest MA. This will need to be monitored. Aside from that potential icing scenario, temperature profiles suggest rain for our area from onset to finish. Models are showing a coastal redevelopment of the system on Wednesday, but disagree on the location. The GFS says Gulf of Maine while the ECMWF says Long Island. The GGEM tries to do a little of both. Still plenty of time for these details to sort out. Thursday through Saturday... The ECMWF shows a second shortwave sweeping down from Canada Thursday while the GFS shows, at best, a very shallow version of one. This may be good for snow showers in the hills, but moisture profiles are sufficiently dry to maintain a dry forecast. High pressure then builds in for Friday and Saturday. Temps in the projected mixed layer support max sfc temps in the 40s. Dew points are projected in the upper 20s and 30s, supporting lows in the 30s.
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&& .AVIATION /07Z SUNDAY THROUGH THURSDAY/...
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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 Monday/... Today...High confidence. VFR. NW winds gusting to 20-25 kt along the immediate east coast, Cape Cod, and the islands, through early afternoon, then diminishing. Tonight and Monday...High confidence. VFR. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Monday Night through Thursday/... Tuesday-Wednesday...Moderate confidence. VFR Tuesday morning, lowering to MVFR cigs/vsbys in rain Tuesday afternoon/evening, then IFR in rain and fog Tuesday night and Wednesday. Conditions may improve Wednesday afternoon. Variable winds Tuesday becoming S-SE Tuesday night, S-SW Wednesday, and West by Wednesday afternoon. Thursday...Moderate 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 Monday/...High Confidence. Gusty NW winds up to 25 kt, mainly across the eastern MA waters. Seas may approach 5 ft there as well, but not really a long fetch. Expanded a marginal Small Craft Advisory into Cape Cod Bay for today. Winds should diminish on the near shore waters around midday, but will linger on the outer waters through the day. Relatively light winds and seas tonight and Monday, as a high pressure moves through New England. Northwest winds diminish this evening, then gradually shift southwest by Monday afternoon. Outlook /Monday Night through Thursday/...Moderate confidence. Monday-Tuesday...Winds less than 20 knots and seas less than 5 feet. Tuesday night-Wednesday...Southeast winds reach 25 knots on the outer waters and possibly RI Sound, with seas building to 5-7 feet. Best chance is on the southern outer waters. Small Craft Advisory may be needed on these waters. Visibility will be reduced in periods of rain Tuesday night, with rain tapering off as winds shift from the West Wednesday afternoon. Thursday...Northwest winds will gust to 25 knots on some of the waters. Seas of 5-7 feet will slowly diminish during the afternoon.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 6 AM this morning to 9 PM EST this evening for ANZ250-254. Small Craft Advisory from 6 AM this morning to 1 PM EST this afternoon for ANZ251.
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&& $$ SYNOPSIS...WTB/Belk NEAR TERM...Belk SHORT TERM...Belk LONG TERM...WTB AVIATION...WTB/Belk MARINE...WTB/Belk

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