textproduct: Boston / Norton

WHAT HAS CHANGED

Small Craft Advisories start 8 PM Sunday evening for the southern waters. Potential for rain to last a bit longer Monday, especially across the south coast, Cape and Islands.

KEY MESSAGES

- Pleasant conditions through Sunday morning. Rain arrives Sunday afternoon and lasts through the night.

- Becoming drier Monday. Round of showers Tuesday into Wednesday morning, then dry through Thursday night. Another round of showers possible some time Friday into Saturday.

- Quick round of rain around mid week, then dry weather returns by Thursday.

DISCUSSION

KEY MESSAGE 1...Pleasant conditions through Sunday morning. Rain arrives Sunday afternoon and lasts through the night.

Pleasant and dry conditions continue through a good portion of Sunday, with partly cloudy skies and low winds through tonight. Expecting to see some radiational cooling tonight with calm winds, but light cloud cover will limit just how far temperatures will drop. Overnight lows likely bottom out in lower 40s for most, upper 30s in the higher elevations.

Attention then turns to Sunday afternoon and evening as the remnants of Hurricane Isaias make their way north and east with the jet stream. As it exits off the DelMarVa coast and enter our waters south of the Islands, it's expected to strengthen and pass north of the 40/70 benchmark. PWATs will likely surge to near 2.0", mostly along the south coast, Cape, and Islands. With rain arriving Sunday afternoon (early PM for the interior, later PM for RI and eastern MA) and lingering into Monday, rainfall totals will likely be in the 0.75 inch to 1.0 inch range. It's possible some heavier rain bands set up, but confidence is low on where or when exactly those could develop; therefore, some areas could see local higher rainfall totals... possibly up to 1.5 inches across the south coast, Cape, and Islands. Thankfully, the bulk of the LLJ will be kept aloft and offshore, so the worst of the winds will be kept offshore and on the order of 23 to 30 knots.

KEY MESSAGE 2...The next quick moving round of rain comes Sunday afternoon and evening, continuing overnight and exiting Monday morning.

Low pressure slowly moves away from southern New England Monday. This will gradually bring an end to our showers from northwest to southeast. Still some disagreement on how quickly it all ends. The GFS remains on the more progressive side of the solution envelope. The most likely area for showers to linger longer will be towards the Cape and islands. Further adjustments to the timing are possible with later forecasts.

Our region then has a brief drier period Monday night into Tuesday morning.

KEY MESSAGE 3...Quick round of rain around mid week, then dry weather returns by Thursday.

Our region should then get clipped by a pair of low pressures, each taking a different track. The first should pass from the Great Lakes across northern New England Tuesday into Tuesday night. The risk for showers arrives across northern MA during the morning, then gradually moves south Tuesday night as the associated cold front approaches. Drying out Wednesday as this front finally moves farther offshore during the day.

High pressure over eastern Canada should briefly take over our weather Wednesday night into Thursday night.

The forecast for next Friday and Saturday is uncertain. A low pressure moving east across Canada could swing its associated fronts across our region during this time. The issue continues to be one of timing. This low pressure is quite distant from southern New England. Thinking a slower onset timing is more likely to develop with later forecasts given a high pressure over the North Atlantic. Then there is the question of how quickly it dries out on Saturday. We should see a period of showers some time Friday into Saturday.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Forecaster Confidence Levels...

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

Tonight: High confidence.

VFR. Light N to NE winds become light and variable by 04Z Sunday for most. Winds like become light S/SSE by 04Z across the Cape and islands.

Sunday and Sunday Night: High confidence.

VFR. S/SE winds 5-10 kts with RA arriving from west to east generally between 16Z-20Z. MVFR ceilings and -SHRA overspread the region from west to east 21z-24z.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Monday through Thursday/...

Columbus Day: Mainly VFR, with local IFR possible. Breezy.

Monday Night: Mainly VFR, with local MVFR possible.

Tuesday: Mainly VFR, with areas MVFR possible. Slight chance SHRA.

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

Wednesday: VFR. Breezy. Slight chance SHRA.

Wednesday Night through Thursday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Through Sunday Night: High confidence.

Winds 10-15 kt today become light northeasterly late this evening into tonight as high pressure approaches. Seas 3 ft or less all waters. Sunday winds increase again ahead of approaching low pressure, S/SW 10-15 kts gusting 15-20 kts. The remnants of Hurricane Isaias arrive Sunday PM, building seas 5 to 10 ft and wind gusts 23 to 30 knots by Sunday night. SCAs have been issued starting 8PM Sunday evening for the southern waters, including coastal RI waters.

Outlook /Monday through Thursday/...

Columbus Day: Winds less than 25 kt. Rough seas up to 9 ft. Slight chance of rain showers.

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

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

Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Chance of rain showers.

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

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 8 PM Sunday to 8 PM EDT Monday for ANZ235-237-254>256.