Area Forecast Discussion
Issued by NWS Boston, MA

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737 FXUS61 KBOX 220521 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 121 AM EDT Sun Sep 22 2024 .SYNOPSIS...
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Rain near the coast will slowly come to an end today as low pressure southeast of New England will moves farther out to sea. Weak high pressure will build over the region Monday and Tuesday but continued onshore winds should keep cloudiness over southern New England, especially near the coast. Rain chances increase again around midweek as a front approaches from the Great Lakes.
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&& .NEAR TERM /THROUGH TODAY/...
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Slow improvement is the theme for today`s forecast as offshore low takes its time heading farther out to sea. Radar trends continue to show erosion of its rain shield over eastern MA as drier air aloft is working into region from north, and as surface ridging continues to take hold today, we should see rain continue to diminish, but probably not until around sunrise in most of eastern MA and later this morning near Cape Cod and Islands. It`s possible we even see some breaks of sunshine this afternoon. Farther west, there`s still enough low level moisture present to maintain at least some cloudiness today, but certainly better chances of seeing sun break out as you head toward the CT River Valley and east slopes of the Berkshires. Still a windy day across SE MA, especially on Cape Cod and Islands where 25-35 mph gusts are expected most of the day.
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&& .SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
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Ridging at surface and aloft begins to take hold tonight and Monday leading to drier weather overall. Model cross sections still show plenty of lower level moisture, however, especially near coast tonight which should result in low clouds and possibly some drizzle as well. Clouds should dominate Monday but expect breaks of sun, especially inland.
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&& .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights... * Onshore surface flow much of the week will yield generally dreary conditions * Frontal system sometime mid to late week brings another chance for rain Low pressure that brought much needed rainfall to eastern southern New England over the weekend will continue to shift to our southeast, out into the more open Atlantic, early next week. While the low wont have a dominant effect on our weather for next work week, it will meander around the Bermuda area for a good portion of the week. For Tuesday and Wednesday, mid level ridging will build across the mid-Atlantic, leaving us in the northern fringes of the ridge, but onshore surface flow will counteract any expected warming effects from the ridge. Given onshore flow, expecting considerable cloudiness much of the week. Mid level cutoff low begins to develop mid week and its associated trough will cut south into southern Quebec and northern New England on Wednesday and Thursday. Front associated with this cutoff will bring our next best chance for rain. Trough remains draped over southern New England through at least Saturday, which will support unsettled, showery conditions to round out the work week and start the weekend. Temperatures look to respect the page turn from astronomical Summer to astronomical Fall, which occurs on Sunday the 21st. Highs will be below normal to start the week ranging from the upper 50s in the high terrain of western and central MA to the mid 60s to low 70s elsewhere the first half of the week. Gradual warming trend is possible late week, with widespread highs in the 70s expected Friday and Saturday. As mentioned by the previous forecaster, persistent onshore flow will lead to a continued risk for rip currents and high surf through at least Tuesday. With the Harvest Moon waning, coastal flooding concerns will decrease each day, though it is possible some splashover occurs during the Monday daylight high tide. && .AVIATION /06Z SUNDAY THROUGH THURSDAY/...
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Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06Z Update: Moderate confidence (40%) due to timing of ceilings. Rain and IFR ceilings near Cape Cod and Islands will linger through sunrise before rain tapers off and ceilings improve to MVFR where they should remain all day with NE winds gusting to 25-30kt. Rain will diminish before sunrise in much of RI and eastern MA where MVFR ceilings should lift to VFR for a few hours before returning 12-14z, then improving to VFR again during afternoon. Farther west, VFR ceilings prevail except near KORH where IFR ceilings improve to MVFR this morning and to VFR this afternoon. VFR tonight, but coastal areas should see MVFR ceilings with possible drizzle at times. Improvement to VFR Monday, but probably not until early afternoon near coast with continued NE winds, although lighter. BOS TAF...Moderate confidence due to timing of ceiling changes. MVFR ceilings may not return as quickly as forecast this morning and again tonight. BDL TAF... High Confidence. Outlook /Monday Night through Thursday/... Monday Night: Mainly VFR, with local MVFR possible. Breezy. Tuesday: Mainly VFR, with areas MVFR possible. Tuesday Night: Mainly VFR, with local IFR possible. Wednesday: Mainly VFR, with local IFR possible. Slight chance SHRA. Wednesday Night through Thursday: Mainly VFR, with areas IFR possible. Chance SHRA.
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&& .MARINE...
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Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Overall high confidence through Monday. Maintaining SCA headlines for all waters except Boston Harbor and Narragansett Bay. Low pressure offshore remains close enough today to maintain strong NE winds gusting to 25-30kt, with strongest gusts around Cape Cod and Islands where some marginal Gales are possible at times today. NE winds gradually subside tonight and Monday as low heads farther SE away from region but rough seas should persist, especially on open waters. Rain gradually diminishes today but may linger most of day on waters south and east of Cape Cod. Outlook /Monday Night through Thursday/... Monday Night: Winds less than 25 kt. Rough seas up to 9 ft. Tuesday through Tuesday Night: Winds less than 25 kt. Rough seas up to 8 ft. Wednesday: Winds less than 25 kt. Areas of rough seas. Wednesday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. Thursday: Winds less than 25 kt. Areas of rough seas. Chance of rain showers.
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&& .TIDES/COASTAL FLOODING...
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Coastal Flood Advisory remains in effect for afternoon high tide today. While astronomical tides remain elevated, the tides are slowly coming down from the peak Fri and Sat. Still expecting a surge of 1-1.5 ft which will result in shallow flooding less than one foot deep of more vulnerable locations. High Surf Advisory remains posted due to high seas and rough surf which will continue today.
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&& .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None. MA...High Surf Advisory until 8 PM EDT this evening for MAZ007-019- 020-022>024. Coastal Flood Advisory from noon today to 6 PM EDT this evening for MAZ007-015-016-019-022>024. RI...High Surf Advisory until 8 PM EDT this evening for RIZ006>008. MARINE...Small Craft Advisory until 8 AM EDT Monday for ANZ231-232-250- 251-254>256. Small Craft Advisory until 2 AM EDT Monday for ANZ233>235-237.
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&& $$ SYNOPSIS...Belk/JWD NEAR TERM...JWD SHORT TERM...JWD LONG TERM...KS AVIATION...Belk/JWD MARINE...Belk/JWD TIDES/COASTAL FLOODING...JWD