textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes but temperatures trending cooler for next week.

KEY MESSAGES

- Cooler tomorrow with continued dry conditions.

- Some snow showers remain possible Sunday night into Monday morning. Minor accumulations with little to no impacts expected.

- Mostly seasonable temps Tue through Sat but becoming more unsettled for the middle of the week into next weekend. Low confidence on details and timing.

DISCUSSION

Key Message 1...Cooler tomorrow with continued dry conditions.

A front slated to move through the region tonight will aid in bringing slightly cooler temperatures for Sunday as winds shift more N and E during the day. 925 mb temperatures approach -10C heading into Sunday morning, and generally settle around -5C with high pressure. Winds remain light through the day as well. Highs generally in the 30s can be expected across the region, with spots closer to the coast staying mostly in the lower 30s.

Key Message 2...Some snow showers remain possible Sunday night into Monday morning. Minor accumulations with little to no impacts expected.

The chance for a significant coastal storm at the start of the week is highly unlikely. However, a period of some light snow remains possible, particularly towards the south coast. Some showers in westernmost parts of the interior cannot be ruled out as well.

Guidance has continued to trend the possible coastal storm south of southern New England. A positively tilted trough tracking through the south central US today will continue east, reaching the east coast Sunday night. Its surface low will track off the coast of the Carolinas Sunday night into Monday, shifting out to sea and most likely missing southern New England. A northern-stream shortwave moving across the Great Lakes is also expected to track east at roughly the same time, and this northern stream energy could produce more snow showers in the interior. Guidance still doesn't have this feature and the southern shortwave phasing together until later Monday well offshore and away from southern New England. We may still see impacts from the coastal storm though, mostly in the way of light snow along the south coast. In terms of accumulations, no more than a trace to a few tenths of an inch are expected. And with daytime highs Monday getting into the mid to upper 30s (some spots may reach the low 40s), the light accumulations that we could pick up overnight will likely melt away during the day. On the higher end (75th percentile NBM 4.3), 1" to around 1.5" could fall over the Islands, but elsewhere, less than an inch can be expected across the south coast. The NBM 5.0 has even lower accumulations, with the 75th percentile only getting to 0.5" on the Islands with a few tenths along the south coast and up into the interior. Continued to go with "slight chance" PoPs (15-25 percent chance) for much of the region for light snow showers and "chance" (25-40 percent chance in this forecast) for parts of the south coast and islands.

Key Message 3...Mostly seasonable temps Tue through Sat but becoming more unsettled for the middle of the week into next weekend. Low confidence on details and timing.

We have an active jet setting up from the midweek period into next weekend as Pacific energy traverses the CONUS with multiple shortwaves moving through from the Gt Lakes into New Eng. It's a chaotic -NAO/-PNA pattern with low predictability on details as sensible weather will depend on the timing and placement of these shortwaves and how they interact with each other and with a piece of the TPV moving into the Maritimes. It will become more unsettled with multiple periods of precip possible from the midweek period into next Saturday, but low forecast confidence on timing and details. We will also have a frontal boundary nearby with cold air to the north and milder air to the south which will play havok with temps and ptype. There may be periods of snow, rain and/or mixed wintry precip at times.

On Tue, high pres will be moving offshore with warm advection developing wthin SW flow ahead of a warm front. Expect a lot of cloud cover in the morning and can't rule out a few flurries, then partial sunshine developing in the afternoon. Warm front remains to the SW and BL flow is light so significantly milder air will stay well to the south and west Tue with temps near or slightly above normal, mostly in the upper 30s to lower 40s. The boundary initially stalls near the south coast around Wed before waffling back to the north and south through the week. With a series of shortwaves and surface waves riding along the boundary, expect periods of precip although there will be dry periods as well. The location and placement of the boundary will determine ptype and temps, but there is a chance for one or 2 wintry events through next weekend.

Temps will be mostly seasonable with any mild temps suppressed well to the south and west through the end of the week and into the weekend. Periods of below normal temps likely with precip and the boundary to the south.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Forecaster Confidence Levels...

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

15z TAF Update:

Through 00z Sunday: High confidence.

BKN/OVC mainly VFR ceilings, though hovering around lower- VFR/MVFR bases for BDL and the Berkshires. General west to east decreasing cloudiness west to east after 20z. WSW/W winds around 5-10 kt.

Tonight: High confidence.

VFR. Winds become NW around 5 kt overnight.

Sunday: High confidence.

VFR, with lowering mid/high clouds SW to NE after 18z. NW to N winds 5 kt or less, which could become light/variable late.

Sunday Night: High confidence overall, though moderate to high for PVD, Cape and Islands.

Lowering mainly VFR ceilings, with winds becoming N to NE around 5-10 kt with dry weather for most terminals. Possible MVFR ceilings PVD- Cape airports with light SHSN possible after 08z - visbys in SHSN could be as low as IFR but think 3-6 SM visbys are more likely.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

VFR, briefly lowering to MVFR between 12-14z.

Outlook /Monday through Thursday/...

Washingtons Birthday: Mainly VFR, with local MVFR possible. Breezy. Slight chance SN.

Monday Night: VFR.

Tuesday: Mainly VFR, with local MVFR possible.

Tuesday Night: VFR.

Wednesday: Mainly VFR, with local MVFR possible. Chance RA.

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

Thursday: Mainly VFR, with areas IFR possible. Chance RA.

MARINE

Forecaster Confidence Levels...

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

Through Sunday...High confidence.

A cold front moving over the waters tonight into Sunday morning will bring a period of slightly elevated NW winds over the northern waters. Occasional gusts to 25 kt are a possibility, but are not expected to be very widespread. Seas 2-3 ft are still expected with the outermost areas of the northern waters seeing some pockets of 4 ft seas as that front pushes through. Some light freezing spray is possible for the northeastern waters as well. High pressure takes control once more for the rest of the weekend, keeping seas and winds calmer for Sunday.

Sunday night through Monday...Moderate to high confidence.

Some light snow showers may impact the southern coastal waters Sunday night into Monday. Seas should still remain around 2-3 ft at least through much of Monday, with winds becoming slightly gustier around 20 kt heading into Monday morning.

Outlook /Monday through Thursday/...

Washingtons Birthday: Winds less than 25 kt. Slight chance of snow.

Monday Night through Tuesday: Winds less than 25 kt. Local rough seas.

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

Wednesday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain.

Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Rain likely.

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...None.