textproduct: Boston / Norton

WHAT HAS CHANGED

No major changes to the forecast. The coastal storm will pass well south of the region Sunday night into Monday with little if any impact in southern New England. Next chance for more unsettled weather is mid and late next week.

KEY MESSAGES

- Dry with seasonable high temps in the 30s to near 40 this weekend outside of a brief passing flurry late tonight-Sat am.

- Coastal Storm will pass well south of the region Sunday night into Monday with little if any impact. Next chance for more unsettled weather is mid and late next week.

- Seasonable temperatures much of next week with Tuesday being the potential above normal day...perhaps 50+ in some spots.

DISCUSSION

KEY MESSAGE 1...Dry with seasonable high temps in the 30s to near 40 this weekend outside of a brief passing flurry late tonight-Sat am.

A moisture starved shortwave dropping down in northwest flow will bring mainly just clouds to the region later tonight into Sat morning with nothing more than a brief passing flurry or two. Otherwise...a ridge of high pressure builds into the region this weekend bringing dry weather with seasonable temperatures. Highs will mainly be in the 30s...but some locations may reach 40 Sat afternoon. Overnight low temps will mainly be in the teens with some single digits possible in the outlying locations particularly Sat night with less clouds. Meanwhile the urban heat island of Boston as well as the outer-Cape/Nantucket will only see low temps bottom out in the lower to middle 20s.

Key Message 2...Coastal storm will pass well south of the region Sunday night into Monday with little if any impact. Next chance for more unsettled weather is mid and late week.

Guidance has continued to trend the possible coastal storm well south of southern New England. A positively tilted trough tracking through the SW US today and through the weekend 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. At most, some showers could clip parts of the south coast and the Islands, but most members across ensembles have continued to center around the offshore pass. The northern stream shortwave moving across the Great Lakes is still expected to be the primary driver for keeping this system offshore. With this expected to be a less impactful event, our attention turns more towards another possible system midweek.

Another system tracks across the central US and towards the eastern US midweek, possibly impacting southern New England sometime Wednesday into Thursday. Guidance is indicating some shallow cold air, which could lead to some mixed precipitation issues as 850 mb temperatures just above that later climb to around 0C and slightly above it. Ptype issues could come up again for the system following this one towards the end of the week depending on how it tracks. One thing to continue monitoring for it would be the development of high pressure over Quebec in that timeframe that would likely impact that system. Much is still unknown this far out in the forecast, so stay tuned for updates.

Key Message 3...Seasonable temperatures much of next week with Tuesday being the potential above normal day...perhaps 50+ in some locations.

Mid-level heights rise going into Tuesday afternoon and ahead of the possible Wednesday/Thursday system, and winds shift more SW in the lower levels (more W as you go higher up), advecting in warmer and more moist air. Ensemble probabilities are quite high across southern New England for high temperatures Tuesday reaching 40F or higher. GEPS guidance even has low probs for spots in CT reaching 50F, and if we do get those SW winds with good mixing, the chance for highs hitting 50F there could be higher. Generally, we get back to more seasonably normal temperatures in the mid 30s and low 40s through Wednesday before slightly colder air could make its way into the region towards the end of the week. Lows remain seasonable in the 20s and 30s as well during this warmer period until the end of the week.

AVIATION /19Z FRIDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

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

18z TAF Update...

High confidence in the TAF through Sunday. VFR conditions persist through the weekend with dry weather outside a brief spot flurry or two late tonight into Sat morning. Light winds generally 10 knots or less through the weekend decoupling in the typical spots during the overnight/early morning hours.

KBOS Terminal...High Confidence in TAF.

KBDL Terminal...High Confidence in TAF.

Outlook /Sunday Night through Wednesday/...

Sunday: VFR. Breezy.

Sunday Night: VFR.

Washingtons Birthday through Monday Night: Mainly VFR, with local MVFR possible.

Tuesday through Tuesday Night: VFR.

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

MARINE

Forecaster Confidence Levels...

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

Tonight through Sunday...High confidence.

The main concern will be a cold frontal passage with a surge of NW wind gusts of 25 to 30 knots and choppy seas across our northern waters Sat night into mid morning Sun. We have issued a small craft advisory these locations where some light freezing spray is expected too. Otherwise...a ridge of high pressure will keep winds/seas below small craft advisory across the rest of the waters through the weekend.

Outlook /Sunday Night through Wednesday/...

Sunday Night through Monday Night: Winds less than 25 kt.

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

Tuesday Night: Winds less than 25 kt.

Wednesday: Winds less than 25 kt. Chance of rain.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 9 PM Saturday to 9 AM EST Sunday for ANZ231-251. Small Craft Advisory from 7 PM Saturday to noon EST Sunday for ANZ250-254.