textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

- Warm and pleasant stretch of weather arrives later this afternoon through Friday evening.

- Next chance for showers arrives Friday evening along and ahead of a rather strong cold front.

- Dry and seasonable this weekend, but with more clouds on Sunday.

- Much cooler autumn airmass settles over Southern New England early to middle of next week.

DISCUSSION

KEY MESSAGE 1...Warm and pleasant stretch of weather arrives later this afternoon through Friday evening.

Still have high confidence in improving weather conditions this afternoon through Friday as a mid-level ridge builds in over the region. At present, lingering low clouds and drizzle persist across eastern Massachusetts and Rhode Island. High res guidance shows this stubborn low cloud/drizzle layer mixing out in the next several hours and giving way to improving conditions. Could see some patchy fog overnight in the interior given abundant moisture and weak winds as the boundary layer decouples. Temps this afternoon will be quite a bit warmer than they have been in recent days. Highs today rise into the upper 60s to low 70s, then into the mid 70s and perhaps lower 80s Thursday and Friday.

KEY MESSAGE 2...Next chance for showers arrives Friday evening along and ahead of a rather strong cold front.

The next round of showers arrives after sunset Friday as a low pressure system moves across Ontario and Quebec and a cold front extends over the region. Guidance has trended later and weaker with the precip with the highest POPs (30-50%) occurring after sunset Friday. Regardless, not expecting much QPF out of this... less than a quarter inch likely. Most guidance is showing the front stalling out somewhere south of our waters,

Once the low moves through Quebec, a rather strong continental high pressure system will build over Ontario, sinking those +4C to +6C 850mb temperatures down into New England and sharply dropping surface temperatures through the weekend... overnight temps likely drop into the upper 30s to low 40s and daytime highs in the mid 60s.

KEY MESSAGE 3...Dry and seasonable this weekend, but with more clouds on Sunday.

Forecast outlook for this weekend now looks than it was looking 24 hours ago. The last couple cycles of deterministic and ensemble guidance now conveys the idea that the strong high pressure which builds in on Saturday remains strong enough through Sunday to suppress rain showers lurching northward from the southern waters away from land. Sunday still features a considerable amount of cloud cover but dry weather looks to prevail, even as a pretty potent 500 mb shortwave in the northern stream treks eastward along the US/Canada border Sunday night, draping a dry cold front southward into the Sunday night/early Monday timeframe.

Saturday looks to be the pick of the weekend with mostly sunny skies and highs in the mid to upper 60s, but lower 60s along the eastern/southeast coast due to NEly onshore breezes. Highs Sunday should be a couple degrees cooler with more cloud cover.

KEY MESSAGE 4...Much cooler autumn airmass settles over Southern New England early to middle of next week.

Model guidance remains consistent on a dry, blustery and a much cooler autumn airmass for early to mid next week. This occurs in response to a strong upper trough establishing itself over the Northeast, with a sfc 1030 mb anticyclone over the Gt Lakes settling over New England by Tue night. Strong cold advection begins Monday afternoon with 925 mb temps dropping to as low as -2C by 12z Tue!

Expect full sunshine and dry weather, but rather breezy on Monday with a tight northwesterly pressure gradient, with highs in the low to mid 60s and lows in the upper 30s to middle 40s. Even cooler weather arrives by Tue, with highs only in the mid 50s. Depending on how quickly winds slacken Tue night, some areas could have their first frost since last Spring, with lows in the low to mid 30s interior, upper 30s/mid 40s for the cities and low to mid 40s near the eastern/southeast coast.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

00z TAF Update:

Tonight: High confidence.

Mainly VFR. There is still a risk for patchy fog/mist at MVFR- IFR levels across interior Southern New England airports, but development is now more uncertain with a canopy of high clouds much of the night. Light S winds through midnight, becoming SW and increasing to around 5-8 kt.

Thursday: High confidence.

Multi-layered VFR decks. SW winds increase to around 8-12 kt with gusts in the low 20s-kt range, perhaps mid 20s-kt range over the Cape and Islands. Low level wind shear could develop very late Thursday afternoon, but more likely after 00z Friday.

Thursday Night: High confidence.

Multi-layered VFR decks continue. SW winds decrease to around 5-10 kt, but SWly low-level jet of 35 kt could support low level shear/turbulence for eastern TAFs.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...Moderate confidence in TAF. Fog development overnight tonight is now more uncertain with canopy of high clouds.

Outlook /Thursday Night through Monday/...

Friday through Friday Night: VFR. Breezy. Chance SHRA.

Saturday: VFR. Breezy.

Saturday Night through Sunday Night: VFR.

Monday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Overall high confidence.

Fairly tranquil conditions through Friday with light SW winds and seas below 5 feet. Seas build towards 5 feet by late Thursday/early Friday across the southern waters due to the sustained southwest winds.

Outlook /Thursday Night through Monday/...

Friday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

Friday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.

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

Saturday Night through Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers.

Monday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

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