Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 010750 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 250 AM EST Thu Dec 1 2016 .SYNOPSIS... Showers over southern New England during the predawn hours will exit the region at or shortly before sunrise...followed by dry...breezy and mild conditions later this morning and afternoon. Other than the risk of a few snow showers or flurries Friday night...mainly dry conditions continue into much of the weekend, with a trend toward cooler temperatures. For early next week, an uncertain forecast but cool weather is expected with some potential for wintry precipitation sometime Sunday night into Tuesday. && .NEAR TERM /THROUGH TODAY/... 300 am Update... *** Dry weather and sunshine return later this morning *** At 3 am surface analysis has parent low pressure over northern NY state with its attending warm front along the south coast of MA and RI. Temperatures north of the front are in the 40s while 50s to near 60 are being observed from Block Island to Marthas Vineyard to Nantucket. Welcome to December 1st! Strong pressure falls over southern New England at 3 am on the order of 5 to 6 mbs in the past 3 hrs suggest triple point low beginning to form and will track across the region. This will advect warm sector farther north into RI and southeast MA thru sunrise. So expect a mild start to the day across this region. Meanwhile water imagery shows leading edge of dry slot beginning to overspread southern New England. As a result rain shield has moved offshore and has been replaced by low top showers...as cyclonic branch of the warm conveyor belt becomes the main lifting mechanism for precip now thru 09z west...12z east. Lead short wave and associated triple point low move offshore around sunrise with rapid clearing/drying from west to east. This will be accompanied by a wind shift to the west. Winds will immediately become gusty after sunrise as modest pressure-rise fall couplet enhances wind gusts potential. Model soundings supports west winds gusting up to 35-40 mph after sunrise...then settling back to 20 to 30 mph this afternoon. Sunshine returns later this morning and this coupled with a mild start and CAA delayed to later today...highs of 55-60 will be common across RI and eastern MA...50-55 elsewhere with coolest readings over the high terrain. Normal high for Dec 1st is 42F-48F for southern New England. Not as much sunshine across the hilly terrain as strato- cu overspreads this area later this morning and continues thru the afternoon. This cloudiness holds off until mid to late afternoon farther east across RI and eastern MA. So overall not very winter-like for the 1st day of Dec. && .SHORT TERM /TONIGHT THROUGH 6 PM FRIDAY/... Tonight... Dry but cooler with 850 temps falling to about -3C. This combined with a modest west wind will make it feel noticeably cooler. Temps will fall back into the 30s but still running 5-8 degs above normal for early Dec. Some cloudiness expected across northwest MA as lake effect clouds spill up and over the Berkshires. However mainly dry conditions should prevail. Friday... CAA continues and low level flow veers more to the west. This trajectory may be more favorable for lake effect clouds to impact northern MA and possibly farther southward. Both NAM and GFS have increasing low level lapse rates of 6.5C/km to 7.0C/km in the 925-700 mb layer. Given this layer is nearly saturated along with cyclonic flow aloft...could see some lake effect streamers make it over the Berkshires into northern MA. Thus have including very low probs of light showers/sprinkles with snow showers/flurries for the high terrain. Otherwise a typical early Dec day with highs in the mid to upper 40s along with a chilly west wind of 15 to 25 mph. More clouds across northern MA with some partial sunshine expected over CT/RI and southeast MA. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... * Dry with cooling temperatures through the weekend * Low confidence in wintry precip Sun. night into Mon. There is continued uncertainty with regards to precipitation in the mid range models. The Canadian, GFS, and GEFS members all keep southern New England dry throughout the long term period. The EPS members have two low pressures approaching southern New England sometime Sunday night into Monday, one from the north and the other from the south. However, the members are well spread out as far as path and timing. The operational ECMWF indicates a similar solution but slower, delayed until Tuesday into Wednesday. Reading previous forecast discussions, this time period has been very uncertain with models flip flopping, so will keep with a blend of the models for the forecast. Friday through Sunday...High confidence. The upper level low and its surface reflections will move into the Maritimes, leaving southern New England in a tight pressure gradient between the departing low and a strong high pressure across the southeastern CONUS. This will result in rather blustery weather, in addition to temperatures returning to near normal or just below normal. Friday will be the warmest day with temperatures diminishing through the weekend. Sunday night through Wednesday...Low confidence. As stated above, there is quite a bit of spread in the models and the ensembles, leaving a lot of uncertainty for this period of the forecast. Option one - a continuation of the weekend - seasonable temperatures and dry. Option two - a period of wintry precipitation Sunday night and Monday. Option three - a period of wintry precipitation, but not until Tuesday and Wednesday. Which one it will be remains to be seen. Will need to keep an eye on the models over the next few days. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 120 am update... Short Term /through Friday/... Thru 12z...high confidence in trends but lower in exact timing. IFR and MVFR in periods of heavy rain will begin to improve from 07z west to 09z east as back edge of rain sweeps across the area. Additional improvement from 09z to 12z with conditions lifting to VFR west to IFR-MVFR RI and eastern MA. Also expect a wind shift to the SW between 09z to 12z. After 12z...high confidence but slightly lower on exact timing this morning. West winds increase to 25 to 35 kt around or shortly after sunrise. Then wind gusts not quite as strong in the afternoon...closer to 25 kt. Any leftover showers in MVFR-IFR over RI and eastern MA at 12z quickly improves to VFR. Across CT and western-central MA...should be VFR at 12z however marginal MVFR- VFR cigs quickly move back into the area and will overspread RI and eastern MA during the afternoon. Tonight...high confidence. VFR but areas of MVFR cigs across the higher terrain. West winds 5 to 10 kt except 15 to 25 mph along the coast and especially Cape Cod and the Islands. Friday...moderate confidence with some uncertainty on extent of lake effect snow/rain showers entering MA/RI/CT. Marginal VFR-MVFR cigs as lake effect rain/snow showers spilling over the Berkshires into northern MA and eventually CT/RI and southeast MA later in the day. West winds somewhat gusty up to 25 kt. KBOS TAF...rain shield moving rapidly eastward with dry weather and IFR cigs improving to MVFR by 09z-11z. Moderate confidence. KBDL TAF...rain shield moving rapidly eastward with dry weather and IFR cigs improving to MVFR by 08z-10z. Moderate confidence. Outlook /Friday Night through Monday/... Friday night through Sunday...High confidence. Mainly VFR. Blustery W-NW winds expected. Sunday night and Monday...Low confidence. As stated in the long term section there is much uncertainty. Could be VFR and dry or a mix of MVFR/IFR and wintry precip especially across the interior. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/... Today... Triple point low moves across southern New England at sunrise and then into the Gulf of ME. S-SE winds 20-30 kt during the predawn hours shift to the SW at sunrise and then west later this morning at 20-30 kt. A few gusts to 35 kt possible near shore. Showers and fog move offshore and improve with the wind shift around sunrise. Tonight... West winds 20-25 kt. Mainly dry weather and good vsby. Friday... More of the same...west winds 20-25 kt along with mainly dry weather and good vsby. Outlook /Friday Night through Monday/... Moderate confidence. Small craft conditions to start. Then winds and seas gradually diminish throughout the period, falling below small craft criteria for a period Sunday. Then there is a possibility that a low pressure system approaches the waters with a resulting increase in seas and wind. There is also a possibility that high pressure builds into the region and winds and seas remain below small craft criteria. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ231>235-237-251-256. Small Craft Advisory from 8 AM this morning to 5 PM EST this afternoon for ANZ230-236. Gale Warning until noon EST today for ANZ250-254-255. && $$ SYNOPSIS...Nocera NEAR TERM...Nocera SHORT TERM...Nocera LONG TERM...RLG AVIATION...Nocera/RLG MARINE...Nocera/RLG

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