Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 021512 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1012 AM EST Fri Dec 2 2016 .SYNOPSIS... Cooler temperatures are expected as we head into the weekend. Other than scattered light snow showers or flurries over the northern and western higher terrain areas, it should remain mainly dry through most of the weekend. A few brief snow or rain showers are possible Sunday night into early Monday. Otherwise, high pressure will provide dry weather Monday afternoon through midday Tuesday. Low pressure moving out of the Ohio valley to the mid Atlantic states may bring some mixed precipitation as far north as southern New England late Tuesday night through Wednesday, but timing and track remain uncertain. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1012 AM Update... No major changes to the ongoing forecast. Clouds were more prevalent across the western half of MA, as well as portions of northern CT. Expecting more diurnal clouds, again, this afternoon. Should be mainly dry across southern New England, too. Brought the forecast back in line with observed trends. 645 AM Update... Noting clear skies across central and eastern areas per latest OBS and IR satellite imagery as of 10Z. Bands of low and mid level clouds moving E out of NY state across W MA into N CT, which will tend to thin out somewhat as it works eastward this morning. Another band of high clouds starting to slide E across central CT into W RI, which will push across remainder of RI and SE Mass through midday or so. The lower clouds should tend to dissipate as they slide E with downsloping winds off the Berkshires in place. Westerly winds will pick up by mid morning, gusting up to around 20-25 kt along coastal areas as well as across the higher inland terrain. Early morning forecast pretty much on track, but have updated to bring conditions current. Made adjustments to cloud cover based on current conditions. Remainder of forecast in pretty good shape. Previous Discussion... Downsloping westerly winds should help keep southern New England dry today. Temperatures will be a little cooler than yesterday thanks to some modest cold advection. High temperatures are expected to range from the mid 40s across the higher terrain to near 50 across the southeast coastal plain. A fair amount of cloudiness will probably persist today near the crest of the Berkshires but considerable sunshine everywhere to the east. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... Tonight...All models depict a short wave trough and some pooling of deeper moisture passing across our area tonight. Looks to be enough there to support scattered snow showers over the Berkshires spilling onto the east slopes, especially in Franklin County. Can not rule out a very minor accumulation of say a half inch or so in the higher elevations of northwest Franklin County tonight. May also see a few flurries tonight over the northern Worcester hills. We may also experience a period of gusty winds as well tonight as the short wave trough aloft and leading edge of a pulse of cold air advection moves through. Temperatures will drop with the cold advection, but mixing from the wind and at least partial cloud cover will tend to brake the temperature drop. Saturday...Looks to be dry with mostly sunny skies across most of the area. As the surface wind becomes more northerly later in the day, ocean effect clouds may impact the outer Cape with a slight chance of showers grazing the very outer Cape. H85 temperatures dropping a few degrees Celsius will translate to surface high temperatures 4 or 5 degrees cooler Saturday afternoon than Friday afternoon. Nonetheless, highs in the lower to mid 40s are not too far off our climatological normals, perhaps just a degree or two below average. Winds will again be fairly gusty, reaching 20 to 25 mph during much of the day. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Highlights... * Temperatures running a bit below seasonal normals through at least Tuesday * Low pressure developing across the mid Atlantic states may push some mixed precipitation into the region Tuesday night and Wednesday, but confidence remains low Saturday night and Sunday...High confidence. Lower clouds and spotty ocean effect rain showers may continue Saturday night into Sunday morning across outer Cape Cod as colder air moves across the milder waters on strong N-NW winds. Not expecting much in the way of QPF, however. Otherwise, expect mainly dry conditions elsewhere across the region. Winds will be gusty, up to 25-30 kt across the higher inland terrain as well as along the coast Saturday night, then will diminish during Sunday. After overnight lows mainly in the 20s inland ranging to the lower-mid 30s along the shore Sat night, temps on Sunday only rebound to the mid and upper 30s across the higher inland terrain up to around 40 across the coastal plain as colder air continues to filter in. Sunday night through Monday night...Moderate confidence. Will see a band of clouds approach with a weak H5 short wave that works toward the region Sun night into Monday. Not great model agreement with this feature, with the 00Z ECMWF being the most robust in keeping an area of precipitation overspreading the region by 12Z Monday. Both the 00Z GFS and GGEM tend to dry out the moisture with this feature, which appears most reasonable considering the NW flow in place aloft and not a lot of low level moisture inflow off the ocean. Still can not rule out a few rain and/or snow showers overnight into Monday morning as the short wave passes. Clouds should start to move out by midday Monday, though may linger through the day along the coast. Tuesday...High confidence. Dry conditions will continue on Tuesday as high pressure ridge remains across the northeast into Quebec. Mostly sunny skies to start, then will start to see mid and high clouds work in from the SW during the afternoon. Expect temps to top off in the 35-40 degree range across the higher inland terrain, and in the lower 40s across the coastal plain and lower CT valley. Tuesday night and Wednesday...Low confidence. Elongated precip shield lies to the S and W of the region as high pressure shifts E of the region Tuesday night. Big question will be the timing as the high exits, if it does. Also, as mid level ridge builds N into Hudson Bay, H5 short wave will ride NE in the developing SW flow. Timing issues also exist amongst the model suite with the movement of this short wave. Noting two surface low pressure centers develop, one associated with the short wave near the eastern Great Lakes while a second forms off the mid Atlantic coast by 12Z Wednesday. Again, model and ensemble solution spread lending to lower than average confidence, with the 00Z GFS appearing to be the most robust and furthest NE with the precip shield while the GGEM keeps what is left of the H5 system further S and weaker. Also noting a pretty good easterly low level jet in place helping to feed moisture into the system on the GFS. Both the 00Z GGEM and 12Z ECMWF tend to dry the system out as the high pressure remains stronger as it extends S out of Quebec across eastern New England through Wed. Will continue to lean toward a model blend at this point due to the remaining uncertainty. Will keep chance POPs going for now during this timeframe. Thursday...Low confidence. Timing and track issues continue with the passing system across the region, mainly due to how the mid level development takes place. The GFS does not develop the mid level long wave trough nearly as much as the ECMWF, which allows the H5 cutoff low to shift NE faster than the ECMWF. This produces wide surface solution spread, along with issues with how the sensible weather evolves. Also, with EC keeping the strong system further W, will see PTYPE issues. Overall, low confidence continues. Will keep chance POPs going, but go no higher than 40 percent for now. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/... High confidence. BKN-OVC clouds at 2500-3000 ft at times near the crests of the Berkshires today through Saturday. There could also be a band of clouds near or a little under 3000 feet across the outer Cape during mid to late Saturday afternoon. Otherwise, VFR conditions should prevail. West winds today and NW winds Saturday at the surface may gust to 20 knots at times. Scattered snow showers tonight over the Berkshires could locally lower the visibility to 5 or 6 miles. KBOS TAF...High confidence in overall TAF. VFR. West wind may gust between 20 and 25 knots this afternoon into this evening. KBDL TAF...High confidence in overall TAF. Outlook /Saturday Night through Tuesday/... Saturday night and Sunday...High confidence. Mainly VFR. May see some spotty light -SHRA Saturday night into Sunday morning across outer Cape Cod. NW wind gusts up to 25-30 kt, especially in the higher terrain and along the south and east coasts then should diminish Sunday afternoon. Sunday night and Monday...Low confidence. May see patchy MVFR conditions in spotty -SHRA/-SHSN Sunday night into Monday morning, then should be mainly VFR by Monday afternoon. Monday night...Moderate confidence. VFR. Tuesday...Moderate confidence for overall trends, lower on exact timing. Mainly VFR. May see MVFR CIGS/VSBYS move into central and western areas Tuesday afternoon in mainly -RA, but may see mixed precipitation toward Tuesday evening. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Saturday/... Moderate confidence for this period. Gusty winds will persist from the west today and northwest Saturday. Will keep Small Craft Advisories up for most waters through at least daybreak Saturday. Our mixing height tool suggests increasing gusts over Boston Harbor and Narragansett Bay as well toward evening and have Small Craft Advisories going into effect again at 3 PM today. That may be a few hours early but believe it wise to have a small buffer in the event the timing is off some. Anticipate west wind gusts between 25 and 30 knots across most of the coastal waters this evening. Outlook /Saturday Night through Tuesday/...Moderate confidence. Saturday night...NW winds gusting up to 25-30 kt, highest over the outer waters. Seas will range up to 5-7 ft over the outer waters. Winds should diminish over Boston Harbor and Narragansett Bay after midnight Saturday night. Sunday and Monday...Expect winds and seas to diminish below small craft criteria during Sunday, then should remain below small craft Sunday night and Monday. Monday night and Tuesday...Winds and seas remain below small craft criteria. N-NE winds gusting up to 20 kt during Tuesday on the outer waters south of Block Island. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 AM EST Saturday for ANZ231>235- 237-250-251-254>256. Small Craft Advisory from 3 PM this afternoon to 7 AM EST Saturday for ANZ230-236. && $$ SYNOPSIS...EVT/Thompson NEAR TERM...Belk/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.