Area Forecast Discussion
Issued by NWS Boston, MA

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611 FXUS61 KBOX 100857 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 357 AM EST Sat Dec 10 2016 .SYNOPSIS... Mainly dry, but unseasonably cold temperatures are on tap for our region through mid afternoon Sunday. Low pressure will bring accumulating snow to much of the region Sunday night and Monday morning, which will likely change to rain on the coastal plain. Unsettled and uncertain weather continues through much of the rest of the week. Regardless, a shot of arctic air appears to close out next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Southern New England will remain between two surface systems, a low pressure over the Maritimes, and a high pressure over the central USA, for one more day. Expecting another day of gusty west-northwest winds, but not quite as strong as Friday. One more mid level shortwave will also pass us by. However, there is not a lot of moisture for it to work with. Expecting another day of diurnal clouds, but not much more than that. The greatest risk for any showers will be offshore, where the humidity will be higher. Max temperatures should be 5-10 degrees lower than Friday. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... High pressure reaches the mid Atlantic coast late tonight, then moves offshore Sunday. Winds will diminish, setting the stage for another cold night. Winds become light southwest during Sunday, which will help to boost temperatures slightly. Dry weather prevails. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... ***Accumulating snow Sunday night into Monday will pose a significant impact to the Monday morning commute north and west of the Boston/Providence corridor*** * Snowfall estimates unchanged from previous forecasts * Unsettled weather continues through the middle of the week * Another round of arctic air late in the week Sunday night and Monday...High confidence in snow event occurring, lower confidence in details. Models are in much better agreement than in previous days on this event. That being said, there is still a decent amount of uncertainty. Minor changes in the path and timing of both the main low and the secondary low could result in significant changes to the timing and amount of snow. Low pressure in the Great Lakes will move through Quebec and into the Maritimes. One of the things models differ on is the development of a secondary low and its timing and location. The GFS and its ensembles are in excellent agreement, developing a secondary low somewhere in the tri-state region early Monday morning. The ECMWF and its ensembles are also in great agreement, developing the secondary low in the Gulf of Maine Monday afternoon. This system will bring a period of accumulating snow to much of southern New England. Light snow will begin Sunday evening as warm air starts moving in over the arctic air at the surface. With very cold air in place over the region, everyone should start as snow. As the low level jet increases in response to the low pressure system in the Great Lakes late Sunday night, snow will intensify. At this point, it appears the heaviest snow will coincide with the Monday morning commute. While everyone will start as snow, expect a quick change to rain particularly along the south coast, Cape, and Islands. Elsewhere, snow will gradually change to rain through Monday morning. The speed at which this occurs and the extent of the rain will depend on when and where the secondary low develops and how quickly the warmer air moves into the region. Tuesday and Wednesday...Low confidence. While there continue to be discrepancies in the models, this looks to be the driest, quietest period of the long term forecast with temperatures starting to cool but still near normal. Previous models have indicated another storm system affecting southern New England. The 00Z model runs show a coastal storm, but keeps it far enough offshore to not affect southern New England. Thursday and Friday...Low confidence. Another shot of arctic air moves into southern New England as high pressure builds into the region. Temperatures will be well below normal. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/...High confidence. VFR through this period. Low risk of MVFR cigs across the outer Cape today. Northwest wind gusts of 20 to 25 knots at times today, especially across the higher elevations. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Sunday Night through Wednesday/... Sunday night through Monday...Moderate confidence. MVFR/IFR conditions develop in snow Sunday night. Snow may change to rain across portions of the coastal plain early Monday. Accumulating snow is likely across the interior. Some improvement is likely late Monday as precipitation comes to an end. Monday night through Wednesday...Low confidence. Improving conditions. Mainly VFR. Low probability of a precip event with MVFR/IFR conditions sometime late Tuesday or Wednesday. && .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. Gusty northwest winds will diminish from west to east this afternoon into this evening. Rough seas will also subside overnight. Will stagger the expiration of Small Craft Advisories into tonight. Outlook /Sunday Night through Wednesday/... Sunday night and Monday...Moderate confidence. Seas below 5 feet will increase from the south as low pressure approaches the waters. Winds increase as well and small craft advisories will be necessary. There is a moderate probability of a period of westerly gales. Tuesday...Moderate confidence. Westerly to southwesterly winds and seas slowly diminish. Small craft advisories will likely continue through much of Tuesday. Wednesday...Low confidence. Southwesterly winds shift to the northwest and increase, along with the seas. Small craft advisories are likely. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ232>235-237-256. Small Craft Advisory until 8 AM EST this morning for ANZ230. Small Craft Advisory until 8 PM EST this evening for ANZ231. Small Craft Advisory until midnight EST tonight for ANZ250-255. Small Craft Advisory until 11 AM EST this morning for ANZ251. Small Craft Advisory until 3 AM EST Sunday for ANZ254. && $$ SYNOPSIS...Belk/RLG NEAR TERM...Belk SHORT TERM...Belk LONG TERM...RLG AVIATION...Belk/RLG MARINE...Belk/RLG

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