textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

- Passing light rain showers early Saturday morning from interior Southern New England to the coastal plain, but better chances for steady light rain for southeast New England later Saturday afternoon through Sunday morning.

- Sunny and dry with above normal temperatures Monday and Tuesday, with southwesterly breezes.

- Turning more unsettled mid to late next week with showers and possible thunderstorms.

DISCUSSION

KEY MESSAGE 1...Passing light rain showers early Saturday morning from interior Southern New England to the coastal plain, but better chances for steady light rain for southeast New England later Saturday afternoon through Sunday morning.

Although dry weather prevails today and most of tonight, monitoring a couple of periods of showers for Saturday into part of Sunday.

The first of these shower chances is with a lead 500 mb shortwave disturbance now over eastern OH, which is bringing clouds and rain showers to western NY and northwest PA as of Friday afternoon. Expect increasing clouds and passing light rain showers to move into western MA and CT closer to the pre- dawn hours Saturday, then steadily moving eastward into central and eastern MA around mid to late Saturday morning. These are really light passing showers, perhaps enough to wet pavement but nothing more. QPF amts with this round of showers should be less than a tenth of an inch.

A more robust system coming out of the Gulf Coast states tonight into early on Saturday then deepens to a sub-990 mb cyclone as it takes a track NE to a path east of the 40N/70W benchmark for late Saturday/Saturday night and continuing northward into Sunday. The western extent of this system's rain shield is still in some question, with the 12z GFS in particular being quite a bit drier than most other guidance. Advancing drier air into interior Southern New England on NW winds should mitigate rain chances there, but the western edge of steadier rains looks to be into the MA/RI coastal plain to around I-495, where rain totals are up to a quarter to third of an inch. Strongest chances for steadier light rain and mist would be across the South Coast, Cape Cod and the Islands starting later Saturday afternoon, with wrap- around rain continuing into early Sunday before pulling away Sunday afternoon. Rain totals for these southeastern areas Saturday and Sunday around a half to three- quarters of an inch.

All told, not really a great weekend if your plans bring you to Cape Cod or eastern MA and RI, but conditions in CT and western MA should be quite a bit better. Highs mainly in the 50s on Saturday with clouds and periods of showers, cooler lower 50s in southeast New England; on Sunday, highs have a decent shot at reaching the low 60s in western interior Southern New England, but are in the mid 50s near the eastern coast as it will take quite a bit longer before we can see peeks of sun develop.

KEY MESSAGE 2...Sunny and dry with above normal temperatures Monday and Tuesday, with southwesterly breezes.

We get into a warming trend toward above normal temperatures for early next week with SWly breezes for Monday and Tuesday. Highs in the 60s to lower 70s on Monday, but diurnal mixing of lower dewpoints (RHs down to around 30 percent) to go along with breezy southwest winds could warrant fire weather concerns on Monday. Temperatures are even warmer with most areas away from the southeast coast well into the 70s, except SW winds look to be a little lighter and relative humidities aren't quite as low. Will assess how much rain actually falls and then consider fire weather partner input before weighing a decision on fire weather headlines, but they could be possible on Monday and possibly Tuesday.

KEY MESSAGE 3...Turning more unsettled mid to late next week with showers and possible thunderstorms.

500 mb pattern amplifies by midweek, with a pronounced upper trough over the nation's midsection and an amplifying ridge associated with above normal temperatures over the eastern and southeast US into the western Atlantic. A slow-moving frontal boundary will be progressing eastward with low pressure developing along it at some point late in the week - guidance varies on when this happens but loose consensus around Thursday. Pretty robust dynamics and decent moisture plume could favor several opportunities for showers and even a few thunderstorms around late in the week. We do need the rain so this should be more beneficial than necessarily hazardous, but either way, expect temperatures to remain slightly above normal but with chances for rain on the increase.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

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

Through Tonight: High confidence.

Gusty winds become light W by 01Z, then gradually shift more SW to S overnight. VFR generally governs, though risk for -SHRA and low-end VFR/MVFR ceilings at BDL and ORH after 06z Sat.

Saturday: Moderate confidence.

OVC low-end VFR/MVFR ceilings with passing -SHRA over interior CT/western MA advancing east through 17z to BOS. Although SHRA comes to an end for interior Southern New England airports by afternoon with VFR ceilings and NW winds around 5-10 kt, better chance for 4-6 SM -RA and MVFR ceilings comes in after 20z for BOS, PVD and the Cape airports as coastal low pressure begins to approach. S winds become SE/ESE Sat afternoon for eastern airports around 5-10 kt.

Saturday Night: Moderate confidence.

VFR from ORH westward, but MVFR ceilings and steadier -RA continues for PVD, BOS, and the Cape airports. Winds come around to NW around 10 kt Sat night.

KBOS Terminal...High confidence in TAF. Winds to go light late in the day, around 22-04z, which could allow for a period of light onshore winds to develop before becoming S around 5 kt.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday Night through Wednesday/...

Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance RA.

Sunday Night through Tuesday: VFR. Breezy.

Tuesday Night: VFR. Breezy. Slight chance SHRA.

Wednesday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Overall high confidence.

Winds and seas should remain below small craft advisory levels through Saturday night. NW winds around 15-20 kt slacken and become southerly tonight and into Saturday around 10-15 kt, with seas 4 ft or less all waters. Mainly dry weather, though rain begins to increase on the southern waters later Saturday and continues into Saturday night.

Winds and seas then become closer to small craft advisory levels Sunday as winds turn NW with gusts 20-25 kt and seas building to 4-6 ft on the outer waters. Possible need for SCAs on the eastern outer waters for Sunday. Rain could also locally reduce visibility.

Outlook /Saturday Night through Wednesday/...

Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Rain.

Sunday Night: Winds less than 25 kt. Areas of rough seas.

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

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

Tuesday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas.

Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas.

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

BOX WATCHES/WARNINGS/ADVISORIES

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