494 FXUS61 KBOX 270358 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1058 PM EST Tue Jan 26 2021 .SYNOPSIS... Light snow or a wintry mix will continue tonight into Wednesday, and may change to light rain near the coast Wednesday afternoon. The coldest air of the season arrives Thursday and lasts through Saturday with bands of ocean effect snow possible near Cape Cod and Plymouth County. Temperatures should moderate early next week, but a low pressure system tracking south of New England should bring snow and rain. && .NEAR TERM /THROUGH WEDNESDAY/... 1045 PM Update... * Scattered snow showers overnight. * Areas of patchy freezing drizzle and freezing fog may develop across parts of the interior overnight. We are now seeing the tail end of the snow that brought much of our area 2-4 inches of snow moving off the Cape and Islands. As the snow growth region dries out, there may be periods of freezing drizzle. The NBM shows the best chance towards the S coast, but we received a mPING report of FZDZ near Framingham roughly an hour ago. So it could just happen about anywhere across interior MA and CT. Also, there may be areas of patchy freezing fog across the interior valley locations where winds become light and from leftover low-level moisture. So will keep the existing Winter Weather Advisories going to account for the possibility of light icing. If you are out and about tonight, be sure to use caution on the roads. 625 PM Update... Going to expand the Winter Weather Advisory to include central/ southern RI and south coastal MA where we expect to see some spotty light freezing rain later this evening. Already seeing reports of light icing across parts of southern CT and this is expected to head along the coast tonight. Forecast soundings for New Bedford show loss of ice nucleation near -20C which is supportive of freezing drizzle/light freezing rain. Not looking for a lot of icing but enough for slippery travel. So far seeing a lot of 1-2" snowfall reports with a report of 3" in western MA. Last band of more organized snow was moving through central MA and RI and will exit the coast by 8 PM or so. Only expecting patchy light snow or wintry mix tonight as we lose what lift there was from mid level frontogenesis. New accumulations overnight should not be more than an inch or two, which will result in storm totals of 2-4" for most of area in the Winter Weather Advisory and 1-3" outside of that. Should end up with a few 4-5" totals in the higher terrain of western and north central MA - we noticed Fitchburg, MA had a few hours of moderate to heavy snow. && .SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/... Highlights * Winter Weather Advisory in effect through 1PM Wednesday has been expanded to include all of MA west of I-95 as well as northern CT and RI for light accumulating snowfall this evening into Wednesday morning. Moderate snowfall Tuesday night will transition to light ocean-effect snow Wednesday morning. * Ocean-effect snow-showers likely to see some rain mix in during the afternoon hours on Wednesday before transitioning back to snow Wednesday night into Thursday morning. A deamplifying wave propagates eastward Wednesday evening producing areas of moderate snowfall ahead of a surface warm front. Antecedent dry air has made it challenging for this system to reach it's full potential in terms of accumulating snowfall. Nonetheless, forecasting 3-5" of accumulating snow across the interior with 1-3" across the coastal plain. As this wave slides east, a secondary-low pressure system which has developed off the east coast will merge with the surface low to our west and result in a persistent northeasterly flow over southern New England through Thursday morning. This will allow for ocean- effect snow showers to occur intermittently through early Thursday afternoon. Residual warm air from the surface warm- front will result in periods of light rain mixing into this ocean-effect precipitation tomorrow afternoon. As temperatures drop overnight Wednesday into Thursday morning, expecting a transition back to light ocean-effect snow showers during this time period. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... * Shot of Arctic air Thursday - Saturday * Next storm system brings snow or rain early next week Ocean storm still expected to pass well SE of New England Thursday, but NE flow combined with favorable low level temperature profile will support bands of ocean effect snow on Cape Cod and Plymouth County, perhaps onto Islands as well. Accumulation may be limited by surface temps in mid to upper 30s, but an inch is possible in more persistent bands. Our first shot of true Arctic air arrives Thursday night and lasts into Saturday as, dare we sat it, a piece of the polar vortex dives SE across New England. Coldest of airmass affects area Friday and Friday night, when highs only top out in teens and lower 20s and lows Friday night fall back into single numbers and teens, with sub zero readings possible near Berkshires. Gusty NW winds (mainly during daytime) will send wind chills to between zero and 10 below zero, possibly as cold as 15 below near Berkshires and in Worcester County where Wind Chill Advisories may eventually be needed. Upper flow remains fairly progressive so our shot of Arctic air will be relatively short lived. Pattern becomes more amplified early next week as southern stream short wave closes off over mid Atlantic region beneath weak ridging over Great Lakes. Depending upon your model of choice, closed low is forecast to track over (GFS) or just south of New England (ECMWF) sometime between Monday and Tuesday. At this point have to think the slower ECMWF solution is more reasonable since amplified patterns tend to lead to a slower systems. Will leave PoPs in for later Sunday into Tuesday, however main time frame may very well end up being later Monday into Tuesday. At this point, warming low level temps may come into play and result in a transition to rain across SE MA and RI, but it's certainly too soon to make a call on that. Ensemble members from both models show low tracks show 2 camps: one clustered near south coast and another farther offshore. Seeing a lot more spread among EC ensembles, which isn't surprising for nearly a week out in time. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00Z TAF Update: Moderate confidence, mainly due to timing. Expecting conditions to become IFR throughout during evening as ceiling steadily lower and remain that way through Wed night. Light snow should become more intermittent as night progresses and should mix with -FZDZ at times across CT, RI, and SE MA, especially near coast. Any light snow Wed may change to rain across RI and SE MA by Wed afternoon. KBOS TAF...Moderate confidence in TAF. Timing of flight category changes may be off by a few hours. KBDL TAF...Moderate confidence in TAF. Timing of flight category changes may be off by a few hours. Outlook /Wednesday Night through Sunday/... Thursday: Mainly VFR, with local IFR possible. Breezy. Slight chance SHSN. Thursday Night: VFR. Breezy. Friday: VFR. Windy with local gusts up to 30 kt. Friday Night through Saturday Night: VFR. Breezy. Sunday: VFR. Slight chance SN. && .MARINE... Weak low-pressure system passes southeast of New England overnight tonight. This will bring with it periods of snow/rain showers over the coastal waters. Persistent northeasterly flow through Thursday will allow these showers to continue intermittently near the coast. Another system forms along the Carolina coast Thursday and moves out to sea south of the waters. This system will create gusty north- northwest winds that will draw much colder air across the waters. This may bring gales to the waters on Friday as well as moderate to heavy freezing spray. Outlook /Wednesday Night through Sunday/... Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, chance of snow showers. Local visibility 1 to 3 nm. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of snow showers. Thursday Night: Strong winds with local gusts up to 30 kt. Rough seas up to 10 ft. Slight chance of snow showers. Friday: Strong winds with gusts up to 30 kt. Rough seas up to 11 ft. Chance of snow showers. Friday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 11 ft. Saturday: Winds less than 25 kt. Areas of rough seas. Saturday Night: Winds less than 25 kt. Local rough seas. Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of snow. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory until 1 PM EST Wednesday for CTZ003- 004. Winter Weather Advisory until 10 AM EST Wednesday for CTZ002. MA...Winter Weather Advisory until 5 AM EST Wednesday for MAZ020- 021. Winter Weather Advisory until 1 PM EST Wednesday for MAZ003>005-010>013-017-026. Winter Weather Advisory until 10 AM EST Wednesday for MAZ002- 008-009. RI...Winter Weather Advisory until 5 AM EST Wednesday for RIZ003>007. Winter Weather Advisory until 1 PM EST Wednesday for RIZ001- 002. MARINE...None. && $$ SYNOPSIS...BL/RM/JWD NEAR TERM...Chai/JWD SHORT TERM...RM LONG TERM...JWD AVIATION...RM/JWD MARINE...RM/JWD