textproduct: Boston / Norton

WHAT HAS CHANGED

Special Weather Statement continues for possible freezing drizzle for early this morning but impact should be minimal, if any develops at all. Watching the chance for a period of snow or mixed precipitation late this week but confidence is low at this time.

KEY MESSAGES

- Weak low pressure moving across northern New England could produce patchy freezing drizzle or flurries, but little if any impact given spotty anticipated coverage.

- Accumulating snow expected across portions of southern New England Wednesday afternoon into Wednesday evening.

- Active and unsettled pattern continues late week into this weekend with multiple chances for wintry weather. Details to be determined, but increasing confidence in at least some impacts for the region.

DISCUSSION

KEY MESSAGE 1...Weak low pressure moving across northern New England could produce patchy freezing drizzle or flurries, but little if any impact given spotty anticipated coverage.

Still seeing signs for the possibility of freezing drizzle, mainly in the high resolution guidance. There is a lack of strong forcing and deep humidity, so not expecting much more than that this morning.

Although we only need a trace of icing to trigger Winter Weather Advisories, given that the majority of road surfaces have been well treated, and the spotty anticipated coverage, will instead continue to message this risk via a Special Weather Statement. Even then, any icing impacts would be on untreated surfaces or elevated bridges.

Otherwise, expecting a cloudy and pretty dreary/raw day despite southwest winds. Continued to undercut the deterministic high temperatures today but not by much. Temperatures this morning were already a few degrees lower already, especially across eastern MA.

KEY MESSAGE 2...Accumulating snow expected across portions of southern New England Wednesday afternoon into Wednesday evening.

Difficult snow forecast as uncertainty remains with the axis of heaviest precipitation and how low in elevation the snow line will get across our region. Continue to have the greatest confidence, not that it is much, for snowfall across the higher terrain from the northern Worcester Hills along the Route 2 corridor into Franklin County. Much will depend on timing, as snowfall is more likely during the nighttime hours.

Snowfall amounts continue to fluctuate between the guidance. Latest NationalBlend data showed only about a 50-60% chance for more than 3" of snow across far northern MA, practically into NH and VT. It was about a 50% chance for 2 inches of snow along and north of the Mass Pike. Will continue to evaluate the need for any headlines with later forecasts.

This system pulls away Wednesday night and we have high confidence of dry conditions Thursday with temperatures mostly in the 30s, to perhaps lower 40s in spots, as high pres builds in from the north.

KEY MESSAGE 3...Active and unsettled pattern continues late week into this weekend with multiple chances for wintry weather. Details to be determined, but increasing confidence in at least some impacts for the region.

Complex and amplified upper air pattern evolves later this week with an anomalously strong and zonal Pacific jet pushing numerous shortwaves across the CONUS. There remains significant disagreement between global guidance with respect to how the shortwaves interact with each other and so confidence remains low at this time. The first potential for wintry weather is slated to arrive later Friday into Saturday. Guidance currently depicts a broad swath of precipitation along a northward moving warm front extending from an area of low pressure centered over the Great Lakes. There are a myriad of potential solutions and numerous sources of error with this feature that will ultimately determine the timing amounts and intensity of any liquid or frozen precipitation that falls. It's common to see mixed precipitation and icing with these overrunning events so future forecasts may have to hone in on freezing rain and mixed precipitation but we are still 4+ days away from the event. After the Friday- Saturday event, Sunday- Monday will need to be monitored for the next threat for impactful period of weather. Guidance is offering a wide variety of solutions from a deep coastal low to a more progressive system that mainly passes out to sea. Impacts from this system will ultimately be governed by the eventual track and intensity of the low.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

Forecaster Confidence Levels...

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

Through Today: Moderate confidence.

BKN/OVC VFR thru 06-09z then deteriorating to at least widespread MVFR 09-12z as weak wave of low pressure passes to our north. MVFR to borderline IFR ceilings for Tue, which could be accompanied by scattered flurries or patchy freezing drizzle/sprinkles, but either type too spotty to mention in TAF given expected nil accums. Best chance would be between 11-18z west to east. It remains uncertain if ceilings improve thereafter, and MVFR-IFR ceilings could linger into Tue night. Winds become S/SW 5-10 kt.

Tonight through Wednesday Night: Moderate confidence.

A slow-moving front approaches our region from the north late tonight into Wednesday, then possibly reaches the south coast of New England by Wednesday night. A mix of VFR and MVFR for most of the time tonight into Wednesday morning. Another round of low-end MVFR or IFR expected Wednesday afternoon into Wednesday night. Relatively light winds shifting N to NE Wednesday afternoon into Wednesday night.

KBOS Terminal...Moderate confidence in TAF. VFR/MVFR ceilings thru tonight, then increasing clouds with ceilings dropping to widespread MVFR/borderline IFR. Low chance of flurries or freezing drizzle but accums are nil given spotty coverage.

KBDL Terminal...Moderate confidence in TAF. VFR ceilings thru tonight, then increasing clouds with ceilings dropping to widespread MVFR/borderline IFR. Low chance of flurries or freezing drizzle but accums are nil given spotty coverage.

Outlook /Thursday through Saturday/...

Thursday: VFR.

Thursday Night: VFR. Slight chance SN.

Friday through Friday Night: Mainly VFR, with local IFR possible. Chance SN, chance RA.

Saturday: Mainly VFR, with local IFR possible. Chance RA, chance SN.

MARINE

Forecaster Confidence Levels...

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

Through Wednesday Night: High confidence.

Low pressure continues to pull away from the southeast waters today. Seas will remain elevated on the outer waters into Wednesday night. Mainly dry weather should prevail, though can't rule out a flurry or sprinkle this morning but not enough to restrict visibility.

Outlook /Thursday through Saturday/...

Thursday: Winds less than 25 kt. Seas up to 5 ft.

Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

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

Friday Night: Winds less than 25 kt. Local rough seas. Chance of rain, chance of snow. Areas of visibility 1 to 3 nm.

Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain, chance of snow.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 AM EST Thursday for ANZ250-254. Small Craft Advisory until 7 AM EST Thursday for ANZ255-256.