Updated: 635 PM EST Sat Dec 13 2025
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A fast-moving low pressure will bring accumulating snow overnight into Sunday morning, especially south of the Mass Pike. Ocean effect snow showers will linger into Sunday afternoon towards the Cape and Islands. A brief shot of arctic air follows Sunday night into Monday, with wind chill values dropping to between 0 to 10 below zero. It remains cold Tuesday, but a pattern change with a significant warming trend is likely Wednesday into Thursday. The milder conditions will likely be accompanied by a period of gusty winds and showers sometime in the late Thursday into Friday time frame.
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THROUGH SUNDAY
Key Messages...
* Accumulating snow very late tonight-Sun morning, especially south of I-90. Highest accumulations near the south coast.
* Advisory level snowfall expected across much of southeast MA and southern RI.
The latest guidance suite continued to narrow the focus on some of the critical details for this portion of the forecast. That said, some uncertainty remains. For example, at what temperature does the snow start accumulating on untreated paved surfaces? Even a 1F degree change could expand the accumulating snow window by a few hours. That could make a big difference in impacts across our region.
The main concern is with the majority of the snowfall occurring at night, accumulations are a little more likely to occur than at the same temperature during the daytime.
Some of the higher resolution guidance with his last suite exhibited a notable uptick in banding within the dendritic growth zone. Have some confidence the heaviest snowfall will be towards the south coast of MA and RI, but still do not know with certainty exactly where the heaviest band will finally set up.
Based on this subtle shift farther north and slightly better dynamics, the Winter Weather Advisory was expanded into northern Bristol as well as Eastern and Northern Plymouth Counties in MA. Still kept the goal posts wide with respect to the timing. Thinking that most areas away from the Cape and islands will likely be able to have the advisory cancelled earlier than the 7 PM timing.
Steadiest snow will quickly end from west to east through mid morning Sunday.
Expecting ocean effect snow showers to linger across the outer Cape Sunday afternoon and night as arctic air pours into our region on NNW-NW flow. Ocean induced CAPE values expected to increase to 500-600 J/kg. An additional 1-2" is possible on the outer Cape, but boundary layer temperature profiles may be a bit warm for additional accumulations during the afternoon..
SUNDAY NIGHT
Key Messages...
* Very cold with wind chill values near or below zero
The coldest airmass of the season thus far will move in behind the snow for Monday night as 850mb temps crash into the -15C to -20C range. This will result in overnight low temperatures bottoming out in the single digits across the interior, to the low teens near the coastal plain. A strong pressure gradient will result in gusty winds overnight, around 20-30mph. This will bring the windchill index/feels-like temperatures down to the 0F to -5F range, with -5F to -15F in the high terrain. Cold weather advisories may be needed in the northern Berkshires for Monday morning..
MONDAY THROUGH SATURDAY
Key Messages...
* Remaining Cold Monday and Tuesday. Light snow showers are possible Monday night
* Rapid warming trend Wednesday through Friday
* Late week system looks to bring rain and gusty winds to the region.
The Arctic air mass remains in place through Tuesday as GFS and Euro ensembles keep temperature anomalies near 10 degrees colder than normal. While it wont be as cold as Monday morning, high temps will remain in the 20s for Monday, and struggle to top freezing on Tuesday. Tuesday morning lows drop into the teens across the region, but with calm winds, the wind chill index also remains in the teens. A weak shortwave passes through the region Monday night and could bring some light snow showers to the region.
With a lack of strong forcing and marginal moisture, QPF will be light, on the order of a trace to 0.05 inches. Any snow that falls will also be light, under a half inch.
An upper-level ridge originating from milder maritime air over the Pacific Ocean will reach the region by Wednesday, with 850 mb temps rising to +2C. Surface high temps on Wednesday jump into the low to mid 40s, with upper 40s to low 50s possible for Thursday and Friday. Guidance has been relatively consistent in showing a strong shortwave trough dropping out of the Great Lakes on Friday. Temps by Friday will be warm enough to keep precipitation as all rain. Given the strong WAA, there could be some gusty winds associated with this system on Friday, but it is far too early to speculate on potential wind impacts at this time..
Forecaster Confidence Levels...
Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.
Tonight...High confidence.
VFR conditions dominate during the first half of this evening. MVFR-IFR conditions in light snow arrives in the 14/03z to 14/07z time frame. Expecting mainly snow, but a few hours of rain or mixed rain/snow are possible near the Cape and Islands. Steadiest snow south of I-90, and especially towards the south coast where brief LIFR conditions are possible in snow.
Sunday... Moderate Confidence
Snow expected to linger a few hours longer than the last update. Expecting snow to end between 15/16z and 16/18z from northwest to southeast, but lingers to around 21z towards the southeast New England coast. Otherwise, improvement to VFR conditions expected. Light SW winds tonight shift to the NW at 5 to 10 kt Sunday. Could become gusty towards the Sunday evening push.
Sunday night...High Confidence.
VFR outside the the outer-Cape/Nantucket where ocean effect snow showers may persist Sunday evening. This activity should dissipate though after midnight. Otherwise, NW wind gusts of 20 to 25 knots with a few gusts near 30 knots across the high terrain and near the coast develop Sunday night.
KBOS Terminal...High confidence in trends. Moderate confidence in timing. Snow likely develops after 06z, with the bulk of it ending before lunchtime Sunday. Total snow accumulations of 1-2" possible.
KBDL Terminal...Moderate confidence in TAF. Snow develops after 14/03z and ends by mid-late Sunday morning. Total snow accumulations of 1-3" possible.
Outlook /Monday through Thursday/...
Monday: VFR. Breezy.
Monday Night: VFR. Breezy. Slight chance SN.
Tuesday: VFR.
Tuesday Night: VFR. Breezy.
Wednesday: VFR. Windy with local gusts up to 30 kt.
Wednesday Night: VFR. Breezy.
Thursday: VFR. Breezy. Slight chance RA.
Forecaster Confidence Levels...
Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.
Through Sunday Night...High confidence.
Gusty SW winds into this evening ahead of an approaching cold front. Widespread rain/snow moves across the waters late tonight and Sunday morning. Gale Watch Sunday night into Monday as colder air moving over the waters will result in excellent mixing conditions. Areas of very light freezing spray likely Sunday night.
Outlook /Monday through Thursday/...
Monday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Areas of freezing spray likely.
Monday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Slight chance of snow.
Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft.
Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas locally approaching 5 ft.
Wednesday: Strong winds with gusts up to 30 kt. Areas of rough seas.
Wednesday Night: Winds less than 25 kt. Local rough seas.
Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft.