textproduct: Boston / Norton

WHAT HAS CHANGED

Reissued Small Craft Advisories to account for lingering 4-6 foot seas across the southern outer waters. Otherwise, increased the chance for rain overnight across southeastern portions of Massachusetts.

KEY MESSAGES

- Isolated showers and storms this afternoon and evening give way to a dry and cool stretch through the first half of the workweek.

- Widespread showers developing late Wednesday into Thursday with a few showers lingering into Friday. Then drier and trending warmer next weekend.

DISCUSSION

KEY MESSAGE 1...Isolated showers and storms this afternoon and evening give way to a dry and cool stretch through the first half of the workweek.

Any shower and thunderstorm activity diminishes in coverage after sunset as we lose daytime heating and marginal instability. Greatest chance for lingering shower or thunderstorm activity will be well NW of I-95. An additional round showers are possible after midnight mainly SE of I-95 as a weak disturbance provides additional lift along a departing cold front. The bulk of the shower activity should be offshore by Monday morning with lingering showers possible across the Cape and Island around sunrise. Looking at a cool night tonight behind the front. Temperatures will be in the lower 40s across the interior, with a few upper 30s possible at elevation. Elsewhere, lows will be near 50 near the coast where the front likely wont pass through until Monday morning.

Temperatures Monday afternoon trend 8 to 12 degrees cooler as 850 mb temps crash to near 0C, resulting in a noticeably cooler feel. Highs will be in the lower to perhaps mid 60s across the region. Heights build Tuesday as a mid level ridge builds over the region. At the surface, high pressure sets us up for a dry day. Deep Northwest flow should lead to a mostly cloudless sky. Despite full sun, a reinforcing shot of colder mid-level air arrives as 850 mb temps fall to around -1C, or about 10-15 degrees below average. Highs will generally be in the lower 60s across the coastal plain with upper 50s possible at higher elevations.

KEY MESSAGE 2...Widespread showers developing late Wednesday into Thursday with a few showers lingering into Friday. Then drier and trending warmer next weekend.

Fairly robust mid level trough moves across the Gt Lakes Wed then into the NE and New Eng Thu into Fri. This will bring a period of unsettled conditions to SNE for the middle and end of the week. Modest low level jet ahead of the trough will increase moisture transport as shortwave energy rotates around the base of the trough and approaches the region. This should result in a period of widespread showers Wed night into Thu with embedded thunder possible as marginal elevated instability develops at the nose of the LLJ. While bulk of rainfall should be Wed night into Thu, showers may begin to overspread the region Wed afternoon from the west but timing onset is somewhat uncertain. Not expecting heavy rainfall amounts but should be a beneficial soaking rain with amounts averaging 0.50"-1.00". It begins to dry out by Thu night but upper trough and cold pool lingers on Fri which will keep the threat of a few showers but not a washout. Temps will average below climatological normals Wed and Thu recovering to near normal by Fri.

Warming trend is expected next weekend as the upper trough moves out and height rise. We are expecting above normal temps with highs into the 70s but lower confidence in sensible weather as there may be a few quick moving shortwaves to contend with. Overall, looks mostly dry but can't rule out a few showers.

AVIATION /18Z SUNDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

Tonight: Moderate confidence in the northward extent of -RA.

Frontal boundary links up with coastal moisture and brings MVFR ceilings and off-and-on periods of -RA to PVD/UUU and southeast MA. -RA could be possible as far north and west as BED to ORH but is viewed as unlikely, with mainly VFR ceilings for these and the rest of the interior airports. Rain should continue into most of the evening. SW/W winds around 5-10 kt to turn to NW winds around 10 kt late tonight/overnight.

Monday...High confidence.

VFR. Cannot rule out SHRA mainly across southern RI, the south coast of MA, Cape Cod, and the Islands. WNW winds less than 10 kt.

KBOS Terminal...Moderate confidence in TAF.

Introduced a PROB30 for -SHRA from 21-00z this afternoon. Otherwise VFR for tonight with W to NW winds around 10 kt.

KBDL Terminal...Moderate confidence in TAF.

Conditions trend dry but with VFR cloudiness tonight, as winds become NW around 10 kt.

Outlook /Monday Night through Friday/...

Tuesday through Tuesday Night: VFR.

Wednesday: VFR. Breezy. Chance SHRA.

Wednesday Night: Mainly VFR, with local IFR possible. Breezy. SHRA, slight chance TSRA.

Thursday: Mainly VFR, with local MVFR possible. Breezy. SHRA, slight chance TSRA.

Thursday Night: VFR. Slight chance SHRA.

Friday: VFR. Chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Today through Tuesday...Moderate confidence.

Swells between 4 and 6 feet continue through Monday morning with an SCA in effect through 8am Monday morning. Winds N-NW tonight, continuing into Monday, with wind speeds less than 15 kt. Showers are possible late tonight into Monday across the southern waters from Block Island to Nantucket. High pressure brings calmer winds and seas Tuesday.

Outlook /Monday Night through Friday/...

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

Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

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

Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Rain showers.

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers.

Friday: 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...Small Craft Advisory until 8 AM EDT Monday for ANZ254>256.