AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 629 PM EST Fri Dec 26 2025 .WHAT HAS CHANGED... Winter Weather Advisories have been expanded north and east as confidence for 3-6 inches of snow increases. Confidence in 6+ inches outside of SW CT remains low. Gaining confidence in the risk for a period of freezing rain Sunday night into Monday. && .KEY MESSAGES... - Clipper system will bring snow accumulations between 6-8" for parts of western MA and down into central CT. Highest totals remain over SW CT and into SE NY. - Storm system expected to bring accumulating ice Sunday night to rain Monday && .DISCUSSION... KEY MESSAGE 1...Clipper system will bring snow accumulations between 6-8" for parts of western MA and down into central CT. Highest totals remain over SW CT and into SE NY. A clipper system arrives tonight, bringing with it dry snow across southern New England. The latest NBM 5.0 totals trended up along with the latest HREF and high-resolution guidance, notably for our area over central CT and into parts of the east slopes of the Berkshires. The highest totals with this system are still expected to be in SW CT and SE NY. The heaviest band and the associated 700 mb frontogenesis band are expected to set up across those areas and progress east, weakening approaching eastern MA. Snowfall rates of 1" per hour and up to 2-3" per hour are possible within the strongest bands. Considering the latest trends, we opted to upgrade Hartford County and western Hampden county to a Winter Storm Warning, as those would be the most likely places at this time that could see the elevated totals associated with the heavier bands of snow. However, if this band sets up slightly more north or south of what is forecast, snow totals could noticeably change. We also opted to expand the Winter Weather Advisory east, which was mainly fueled by an increased chance in some ocean effect enhancement along the south shore in MA and into the coastal plain that could increase snow totals to between 3-6". Some uncertainty remains regarding how far inland this enhancement could increase totals, though. On the lower end, southern and SE MA can expect totals in the 2-4" range. Southern RI into eastern CT and central MA can expect totals between 3-6". Regarding timing, this remains unchanged from the previous forecast. Snow will move in to southern New England tonight from west to east between 7-9 PM, except in NE MA where snow is not expected to arrive until midnight. Latest guidance also shows the heaviest snow bands moving in between 8 pm and midnight across western and central CT, down into southern CT and southern RI. HREF probabilities indicate +2" an hour rates are most likely over CT. Snow should be exiting the region between 4-7 AM with some lingering snow showers possible through mid-morning for the east coast. Ocean effect enhancement could keep them there slightly longer as some of the CAMs indicate, but uncertainty remains. Lows tonight are expected to be in the teens and low 20s as this system pushes through. Post-storm, drier conditions return ahead of the next system arriving Sunday night. Highs Saturday are not expected to climb out of the upper 20s/low 30s across southern New England, with 925 mb temperatures around -10C in the afternoon. KEY MESSAGE 2...Storm system expected to bring accumulating ice Sunday night to rain Monday. Latest guidance suite has increased confidence in a period of freezing rain Sunday night for most of southern New England. There should then be a transition to plain rain for Monday. Still some questions on the duration of freezing rain, which will then lead directly to total ice accumulations. In particular, the 26/12Z NAM has gone way warm with the warm nose, peaking at +6-9C with about a rather deep subfreezing layer beneath it. Thinking this cold layer is too shallow for sleet, but should be sufficient for freezing rain. Much will also depend on how warm the ground gets Sunday. Expecting increasing clouds during the day with highs only in the 30s. Probabilities continue to favor less than one tenth inch of flat ice accumulation. Across portions of western MA, there is possibility for a little more ice accumulation. Will continue to monitor this potential over the coming day. Timing-wise, the most likely period for freezing rain would be Sunday evening into early Monday morning. Winter headlines will likely be needed for this event, but will hold off until after the snowfall tonight ends. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight...Moderate Confidence. VFR falling to MVFR/IFR with areas of -SN to SN. Areas with the greatest chance of impactful snow accumulation are western MA and central/western CT. Snow moves in from west to east between 00z and 04z. Light E/NE winds. Saturday...Moderate Confidence Snow showers may linger through about 18z for eastern MA into the Cape and Islands. Otherwise turning VFR with NNE winds at 10-15 knots. KBOS Terminal...Moderate confidence VFR. Light snow moves in between 03-05z tonight. Confidence in CIGS is on the lower side as guidance wants to keep CIGS MVFR, but with snow and light NNE winds, CIGS could easily go IFR. KBDL Terminal...High confidence in TAF. MVFR tonight. Snow moves in by 00z tonight and could become moderate to heavy at times between 01-04z. Steady light snow should continue though about 09-12z before moving off to the east. MVFR CIGS tonight in light snow, IFR/LIFR CIGS in moderate to heavy snow. Outlook /Saturday Night through Wednesday/... Sunday: VFR. Sunday Night: MVFR/IFR conditions possible. Breezy. RA, chance FZRA. Monday: Mainly MVFR, with areas IFR possible. Breezy. RA, FZRA. Monday Night: Mainly VFR, with local MVFR possible. Windy with gusts up to 35 kt. Chance RA, slight chance SN. Tuesday: Mainly VFR, with local MVFR possible. Windy with gusts up to 35 kt. Tuesday Night: VFR. Windy with gusts up to 35 kt. Wednesday: Mainly VFR, with local MVFR possible. Windy with local gusts up to 30 kt. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight & Saturday Winds turn NE around 20 knots as a clipper system brings moderate snow to the southern waters, with light snow in the northern waters tonight into Saturday morning. Seas between 2-5 ft. Outlook /Saturday Night through Wednesday/... Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Sunday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Rain, slight chance of freezing rain. Monday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Rain. Monday Night: Moderate risk for gale force winds with gusts up to 45 kt. Rough seas up to 17 ft. Rain likely. Tuesday: gale force winds with gusts up to 40 kt. Rough seas up to 17 ft. Slight chance of snow. Tuesday Night: Strong winds with gusts up to 45 kt. Rough seas up to 14 ft. Wednesday: Strong winds with gusts up to 35 kt. Rough seas up to 12 ft. Slight chance of rain, slight chance of snow. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Storm Warning until 10 AM EST Saturday for CTZ002. Winter Weather Advisory until 10 AM EST Saturday for CTZ003- 004. MA...Winter Storm Warning until 10 AM EST Saturday for MAZ009. Winter Weather Advisory until 10 AM EST Saturday for MAZ002>004-008-010>012-016>021. RI...Winter Weather Advisory until 10 AM EST Saturday for RIZ001>008. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ250. Small Craft Advisory until 7 AM EST Saturday for ANZ254-255. && $$