AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 236 PM EST Sat Dec 27 2025 .WHAT HAS CHANGED... Confidence in a period of freezing rain continues to increase for Sunday night into early Monday morning, especially northwest of the I-95 corridor. Greatest impacts from ice accretion combined with snow covered trees, will be in the CT River Valley of western MA and the Merrimack River Valley of northeast MA. Freezing rain will transition to a light to moderate rain late Sunday night into Monday morning. Confidence continues to increase in the potential for strong gusty winds on Tuesday. Wind Advisories may be needed for at least the high terrain and Cape/Islands. && .KEY MESSAGES... - Patchy black ice possible tonight, otherwise dry but cold through Sunday, with lows in the single digits and teens tonight. - Period of freezing rain Sunday night, before transitioning to rain late Sunday night into Monday morning. Best chance for ice accumulation greater than a trace is across western MA in the CT river valley and in the Merrimack River Valley of northeast MA. - Strong gusty winds and cold Tuesday with a few snow showers or flurries possible. - Below normal temperatures continue through late week. Periods of light snow possible late week. && .DISCUSSION... KEY MESSAGE 1...Patchy black ice possible tonight, otherwise dry but cold through Sunday. Fresh snowpack of mainly 3-6", with up to 8" across CT, combined with high pressure advecting into SNE will yield ideal radiational cooling conditions. Given this, we will follow the colder guidance, supporting most locations with low temps in the single digits and teens tonight. Also, any residual moisture/melting from the daylight hours, will likely refreeze tonight, especially on untreated surfaces yielding black ice. Thus, exercise caution if out tonight. A tranquil winter day Sunday, with light winds and sunshine thru increasing mid/high clouds, but cold with highs in 30s. KEY MESSAGE 2...Period of freezing rain Sunday night, before transitioning to rain late Sunday night into Monday morning. Best chance for ice accumulation greater than a trace is across western MA in the CT river valley and in the Merrimack River Valley of northeast MA. Rapidly intensifying low (sub 980 mb) enters the Great Lakes Sunday night, with its attending warm front into New England. Shallow cold air currently over SNE, combined with strong WAA and a pronounced mid level warm nose of +9C around 850 mb, will yield a ptype of FZRA for most of SNE Sunday night. Model soundings indicate freezing rain will be extremely brief southeast of I-95, with mainly a plain rain event. However, northwest of I-95, soundings indicate shallow cold air will take sometime to erode/dislodge, which makes sense given the fresh 3-6" snowcover. Given this, we incorporated some of the colder guidance into the forecast, specifically, the NBM 10 percentile temps. 12z model guidance may not have captured this fresh snowcover from last night. Therefore, later model runs may trend colder with the current shallow cold airmass over SNE. Thus, advisories may have to be expanded southeast into Boston, southeast MA and the PVD area. For now, we issued a winter weather advisory along and northwest of I-95 Sunday night, given this is the area of greatest confidence. Greatest impacts will likely be across western MA in the CT River Valley and the Merrimack River Valley of northeast MA, where duration of freezing rain will be longest. Flat ice accretion of up to two tenths is possible in this area. This combined with 3-6" of snow cover on trees will yield potential power outages in this region. The 12z HREF run Freezing Rain Accumulation Model (FRAM), a far more reliable method than standard model ice accretion, generates 0.25 to 0.50 inch accretion in western MA northeast into the Merrimack River Valley. Thus, this is our greatest area of concern for impacts Sunday night into very early Monday morning. Rain tapers off to drizzle Monday morning as dry slot races eastward. Chance of showers with the cold front in the afternoon. Temps rise above freezing Monday morning with the passage of the warm front and into the 40s to near 50 in the afternoon. Therefore, threat of icing ends after 09z Monday most locals, after 12z northwest of I495. KEY MESSAGE 3...Strong gusty winds and cold Tuesday with a few snow showers or flurries possible. A fairly strong mid-level trough shifts and cold front shift across southern New England early Tuesday. Strong CAA paired with a moderate LLJ jet raises the concern for efficient mixing of gusty winds down to the surface. Latest guidance hasn`t changed much still showing small differences in the strength of the LLJ. Most global guidance shows 30-40 kts while GFS remains a bit more robust at 40- 50 kts. Model soundings are supportive of the higher gust potential showing a decent mixing depth from around 850 mb. The max gusts will come down to how strong the jet ends up being. Ensembles have a range of 35-50 mph gusts with the higher gusts over the higher terrain and near the Cape/Islands. NBM probabilities have been consistently in the 60-80% range for gusts greater than 45 mph (advisory criteria) for the high terrain (Berkshires, Worcester Hills) and near the Cape/Islands. The NBM also displays low probabilities (< 35%) for max gusts greater than 55 mph confined to the Berkshires/immediate east slope of Berkshires. This seems reasonable given the westerly component flow may support downslope enhancement. Wind Advisories are looking more likely for the high terrain/Cape & Islands, but we`ll need a bit more confidence for other areas in future guidance. For timing, winds increase early Tuesday morning, with the highest gusts late AM through early evening. Temperatures will also be below normal Tuesday and with the added wind gusts would suggest wind chills in the single digits to teens during the day. Mid-level moisture will be present on Tuesday with steep lapse rates/marginal instability. Combined with enhanced westerly flow, this should be enough to bring a streamer/showers from the Great Lakes into western MA. Isolated snow showers or flurries are also possible for southern New England within the cold advective regime. KEY MESSAGE 4...Below normal temperatures continue through late week. Periods of light snow possible late week. There is good agreement among ensemble guidance for continued mid- level troughing across the northeast through late week. Accompanied by cold temperatures aloft, this will support below normal temperatures in the 20s to low 30s. There is a signal for another shot of colder air for Thursday and especially Friday with high potentially struggling to hit 30 Friday. There may be a few systems that move through the flow later in the week; however, confidence is low for precipitation chances/timing. This may bring a period or two of light snow fall late Wednesday through Friday. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today: Moderate Confidence Snow is wrapping up and should be offshore between 13-15z this morning. CIGS around the region are already improving to VFR with the exception of coastal terminals where MVFR CIGS will linger into the afternoon. There may be some gusty NNW winds this morning that could blow snow around, but winds this afternoon become light at 5-10 knots. Tonight: High Confidence VFR. Light NW winds under 5 knots. Sunday: High Confidence VFR. Light WSW winds at 5-10 knots KBOS Terminal...Moderate Confidence Light snow could linger until about 13z with MVFR CIGS lingering until 17z. Otherwise VFR with NNW winds around 10 knots for the afternoon KBDL Terminal...High Confidence VFR. Light NNW winds at 5-10 knots. Outlook /Monday Night through Thursday/... Monday: Mainly IFR, with areas MVFR possible. Breezy. RA, FZRA, patchy FG. Monday Night: VFR. Windy with gusts up to 35 kt. Chance RA, slight chance FZRA. Tuesday: Mainly VFR, with local MVFR possible. Strong winds with local gusts up to 40 kt. Tuesday Night: Mainly VFR, with local MVFR possible. Windy with gusts up to 35 kt. Wednesday: VFR. Breezy. Wednesday Night: VFR. Breezy. Slight chance SN. New Years Day: VFR. Breezy. Chance SN. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through Monday: N-NE winds up to 20 kt across the eastern MA waters yielding SCA seas up to 7 ft. We will continue the SCA headline this evening and overnight. Otherwise, high pressure advects from west to east across SNE tonight and Sunday, yielding tranquil marine conditions by late Dec standards. Powerful low pressure (sub 980 mb) enters the Great Lakes Sunday night into Mon, yielding SW winds up to 25 kt. Stronger winds aloft, but probably of gales holds off until late Monday night/early Tuesday. Outlook /Monday Night through Thursday/... Monday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Rain, patchy fog. Areas of visibility 1 to 3 nm. Monday Night: Strong winds with gusts up to 40 kt. Rough seas up to 17 ft. Chance of rain. Tuesday: gale force winds with local gusts up to 45 kt. Rough seas up to 17 ft. Slight chance of snow. Tuesday Night: Strong winds with gusts up to 40 kt. Rough seas up to 15 ft. Chance of freezing spray. Wednesday: Strong winds with gusts up to 30 kt. Areas of rough seas. Wednesday Night: Strong winds with gusts up to 35 kt. Areas of rough seas. Slight chance of snow. New Years Day: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Chance of snow, chance of rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory from 7 PM Sunday to 6 AM EST Monday for CTZ002>004. MA...Winter Weather Advisory from 7 PM Sunday to 6 AM EST Monday for MAZ002>006-008>014-026. RI...Winter Weather Advisory from 7 PM Sunday to 6 AM EST Monday for RIZ001. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ250- 256. Small Craft Advisory until 1 AM EST Sunday for ANZ254-255. && $$