A frontal boundary just southeast of New England will act as a running board for a wave of low pressure, which will move up and across extreme southeastern New England (center probably passing just south of Cape Cod) during Wednesday afternoon. This will send a shield of light to moderate precipitation across southeastern New England on Wednesday. Milder ocean air will become involved with this system especially since we are really not that deep into the cold air mass which is just trying to push into the region at this time.
Precipitation time-table and type: Expect the edge of the precipitation to be moving across the region from southwest to northeast during the overnight hours (midnight to 6AM). Snow will break out in most areas except mixed rain and snow over Cape Cod and the Islands. During the morning hours up through noon or shortly after will be when the steadiest precipitation occurs. This will be in the form of mix to mainly rain Cape Cod and Islands into southern RI and the South Shore of MA, but as you move inland mix will become snow and it may stay all snow or at least mostly snow mainly north of the Mass Pike and from just west of I-95 west and north. Enough mild air may finally reach into some of these areas during the afternoon for it to become too warm for snow, but by then the vast majority of the precipitation will have fallen and there will be only spotty mix/mist left. All precipitation will be over by early evening.
Snow Accumulation: Nothing over Cape Cod and the Islands, slushy coatings at most then melting in coastal RI and the MA South Shore, building rapidly up to 2-6 inches elsewhere with the highest amounts in the highest elevations of north central MA.
Beyond the Wednesday event…
Cold front slices through the region Thursday with nothing more than a rain or snow shower, but introduces a short-lived shot of cold air for Friday (a hint of things to come). Moderating temperatures Saturday into Sunday as the Polar Vortex wobbles about and pulls back slightly, allowing surface low pressure to cut northwest of New England. This low will drag an arctic cold front across New England Sunday, which may be accompanied by a few snow showers/squalls. This will introduce what is expected to be the first in a series of very cold blasts of air, the first arriving Sunday night (during the Patriots/Ravens game) through Monday (MLK Jr. Day). More of these will follow next week as a very cold pattern settles in.
Storminess next week? It remains to be seen how things will work out, but this looks like a largely cold/dry pattern coming. However, with pieces of energy rotating around a wobbly Polar Vortex, we cannot rule out a few threats of snow (watching Tuesday & Friday of next week as potential threat days, of course timing subject to change).
Reeling things back in, details for the next 7 days for eastern MA, RI, and southern NH…
OVERNIGHT: Clouds thicken. Snow/mix/rain (details above) developing southwest to northeast from around midnight to dawn. Lows from the upper 20s south central NH to lower 30s most other areas, some middle 30s Cape Cod. Wind near calm.
WEDNESDAY: Overcast. Snow north and west, mix/rain southeast (details above), steadiest in the morning, with a slight shift northwestward of the rain/snow line before precipitation tapers in the afternoon. For accumulations, see details above. Highs from around 32 north and west of Boston to the lower 40s Cape Cod and the Islands. Wind E to NE up to 10 MPH.
WEDNESDAY NIGHT: Clearing west to east before midnight then some clouds returning after midnight. Lows in the 20s to around 30, mildest Cape Cod. Wind shifting to W up to 10 MPH. Watch for icy spots on untreated surfaces!
THURSDAY: Mostly cloudy to partly sunny. Chance of passing rain or snow showers. Highs around 40. Wind W 10-20 MPH with higher gusts, shifting to NW by late day.
THURSDAY NIGHT: Mostly clear. Lows around 10. Wind NW 10-20 MPH and gusty. Wind chill around zero at times.
FRIDAY: Mostly sunny. Highs around 30. Wind NW 10-20 MPH and gusty.
SATURDAY: Partly cloudy. Low 17. High 40.
SUNDAY: Variably cloudy. Chance of snow showers. Low 20. High 38 then falling late.
MONDAY – MLK JR DAY: Mostly sunny. Low 5. High 20.