textproduct: Boston / Norton

SYNOPSIS

Scattered light snow showers possible through the evening with little accumulation (if any). Gusty winds continue overnight, although not as strong as during the day today. Still on the cold side for Saturday, but not as windy compared to Friday. Low pressure passes to our north and west Sunday afternoon and night bringing a period of rain with it. Cooling down again for Monday as a cold front passes through. Monitoring possible storminess around Tuesday and/or into Wednesday which could bring wintry weather or rain to Southern New England.

NEAR TERM /THROUGH TODAY/

Key Messages:

* Scattered light snow showers possible through early evening. Impacts to travel are minor to none.

* Gusty westerly winds continue tonight, although not as strong as daytime Friday.

Radar data continue to show lake effect snow bands diminishing across southern New England with the loss of daytime heating. Expecting this trend to continue as an inversion lowers and closes the window for the majority of the lake effect snow bands to make it east of the Berkshires. It will take a little more time for that to happen though. Until then, still the possibility of light snowfall, mainly across the grassy surfaces, this evening.

Previous Discussion...

Radar this afternoon shows scattered light snow showers across southern New England. This activity is expected to continue late this afternoon and into the early evening before dissipating. No impacts to travel are expected. The highest chance of seeing any trace to very light accumulation will be for the high terrain spots along the interior, but should be limited to grassy or elevated surfaces.

Winds will likely remain fairly gusty this evening and tonight as a tightened pressure gradient continues across the region. Although the peak gusts will be likely behind us, gusts 20-30 mph are likely in the evening with some gusts up to 30-40 mph still possible for the isolated higher terrain spots and Cape/Islands. Winds will gradually trend downward overnight as the pressure gradient slowly weakens as low pressure moves further east and surface high pressure works in from the southwest. It will be a chilly night overall, but elevated winds overnight should keep temperatures from tanking as much as they could given the mainly clear skies. Lows should drop into the low to mid 20s for the interior and upper 20s to low 30s closer to the coast. With the added wind factor this will bring wind chills into the teens to 20s overnight.

SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/

Key Messages:

* Gusty winds gradually decrease through the day.

Brief mid-level ridging expected on Saturday with flow turning toward the NW. Surface high pressure will continue to build in from the south through the day. This will continue to support the downward trend in wind magnitude over the course of the day. It will start on the breezier side with model soundings showing sufficient mixing in the boundary layer. Although winds will be weaker than Friday with gusts 20-30 mph. It will be another cooler day with slightly below normal 850mb temperature anomaly over the region still. This will yield high temperatures in the low to mid 30s for the high terrain and upper 30s to low 40s elsewhere. Breezy conditions will make temperatures feel closer to upper 20s/low 30s at times.

Winds will weaken further into Saturday evening/night. Clouds gradually increase through the overnight ahead of the next weather system. Despite increasing clouds, it will still be a chilly night with lows dropping into 20s for most places and low 30s for the immediate coastal areas.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/

Key Messages:

* Low pressure brings rain later Sunday into Sunday night; drying out Monday to go along with cooler temperatures.

* An interior-SNE wintry weather and coastal-plain rain or wet snow-to-rain event remains on the table Tue into early on Wed. Confidence remains low on the details. Best chance for accumulations of snow and possible impacts is in interior Southern New England.

* Drying out for Wed through Fri with below normal temperatures favored.

Details:

Increasing clouds early on Sunday with warm-frontal / isentropically-forced rains breaking out Sun aftn into the evening. This occurs as a rather progressive area of low pressure tracks from southern Ontario ENE along the US/Canada international border. Cloudy but generally dry conditions prevail during the Sunday morning hours, with rain breaking out by Sun aftn. Precip type should be largely as a plain rain but could mix over to wet snowflakes as the storm system exits into early Mon morning. Rain amts around a quarter- inch or less in all areas, ending as back-end snowflakes with nil accum in the higher terrain Sun night.

Focus for the long-term portion of the forecast continues to be a potential storm system centered around Tue into Tue night. This occurs as an open-wave/progressive mid-level shortwave disturbance and its sfc cyclone moves ENE from the southern Plains to near or south of Southern New England/adjacent waters. There remain uncertainties in the system's track, in which there are differences which have unfortunately grown today between the northernmost GFS (a track inside of 40N/70W) with the more offshore ECMWF (a track outside of 40N/70W), with today's Canadian splitting the difference over 40N/70W. Ensemble means and AI guidance support their parent modeling systems. An interior/higher-elevation mainly snow with lower- elevation/coastal plain wet, gloppy snow-to-rain scenario remains a best guess as to precipitation types; but if a warmer, more northern solution like the GFS bears itself out then we could introduce some wintry mixture into the equation. There is also the local nuances inherent to early-season wintry events, in which accumulations are dependent on time-of-day (can be too warm to accumulate on pavement during the day) and the influence mild water temps around 50 degrees would have near the coastal plain given the expectation of sustained onshore flow. The wetter, moisture-laden nature of the system combined with some of the above factors would favor positive-snow-depth-change snow accumulation methodologies vs simple 10:1 snowfall accumulations. For now, there are too many uncertainties as alluded to advertise specific snowfall or rain amounts as of yet, with optimism that some of these details will avail themselves over the coming days. Taking a probabilistic approach for now..,in the area where rain may predominate, NBM-based 24-hour probabilities of 2 or more inches of snow are in the low to nil level (less than 30%) for the coastal plain and most of eastern MA, central CT and much of RI excluding the northwestern hills. For interior Southern New England, 24-hr NBM probabilities of 2 or more inches of snow are in the moderate to high (40-60%) range, and are low to moderate (25-40%) for 4 or more inches. Thus potential for somewhat greater impacts over interior Southern New England where colder air may be more entrenched and lesser as one moves closer to I-95.

Drying out in the wake of the Tue system for Wed, with another dump of colder than normal temperatures as we move toward late in the upcoming workweek, in what could be the coldest air yet seen to this point in the early-winter 2025-2026.

AVIATION /06Z SATURDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

06Z update...

Through 12Z...High Confidence.

VFR. Winds gradually diminish overnight, but remain gusty. W winds 10-15 kts gusting 20-30 kts, decreasing further after 06Z.

Today and Tonight...High Confidence.

VFR. W wind becoming more NW. Winds 8-12 kts gusting to 20-25 kts. Winds diminish Saturday night.

Sunday...High Confidence.

VFR to start, cigs decreasing to MVFR/IFR in -RA. Light SE winds increase becoming S 10-15 kts with gusts 15-25 kts.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday Night through Wednesday/...

Sunday: Mainly MVFR, with local IFR possible. Windy with local gusts up to 30 kt. Chance RA.

Sunday Night: Mainly VFR, with areas MVFR possible. Windy with local gusts up to 30 kt. Chance RA.

Monday: VFR. Breezy.

Monday Night: VFR.

Tuesday: MVFR/IFR conditions possible. RA likely, chance SN.

Tuesday Night: MVFR/IFR conditions possible. Breezy. RA likely, chance SN.

Wednesday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

Tonight through Sunday... High confidence.

* Gale Warning through early Saturday across all waters.

Winds and seas slowly decrease overnight into early Saturday. The bays and harbors will be solidly below Gale criteria this evening and by early Saturday morning the remaining marine zones will be also. These will be likely replaced with SCAs once the Gale Warning expires.

Seas 6-10 ft for the southern outer waters tonight, decreasing Saturday morning.

Outlook /Sunday Night through Wednesday/...

Sunday: Moderate risk for Small Craft Advisory winds with areas of gusts up to 30 kt. Local rough seas. Chance of rain.

Sunday Night: Strong winds with gusts up to 30 kt. Areas of rough seas. Rain.

Monday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.

Monday Night: Winds less than 25 kt.

Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain. Local visibility 1 to 3 nm.

Tuesday Night: Moderate risk for Small Craft Advisory winds with areas of gusts up to 30 kt. Rough seas up to 13 ft. Chance of rain. Local visibility 1 to 3 nm.

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 11 ft. Chance of rain.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 AM EST early this morning for ANZ230-236. Gale Warning until 7 AM EST this morning for ANZ231>235-237- 250-251-254>256.