Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 240742 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 342 AM EDT Tue Apr 24 2018 .SYNOPSIS...
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High pressure in control today will result in plenty of sunshine and another mild afternoon. Low pressure approaching from the southwest will bring a soaking rain to the region very late tonight and Wednesday with localized heavy downpours. This may result in some brief nuisance poor drainage street flooding. Seasonable temperatures follow Thursday through Saturday with mainly dry weather other than a few brief showers possible. A brief cool down expected on Sunday, but this will be short-lived as unseasonably warm temperatures are possible by the middle of next week.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/... 150 AM Update... Other than patchy low clouds and fog reported from KMVY over the last several hours, skies were partly cloudy on average, with more high clouds moving in across the region from the SW as seen on latest GOES-East Night Fog and RBG Nighttime Microphysics products. Noting mainly light southerly or calm winds at most locations as high pressure ridge keeps low pres gradient across NE CT/RI/SE Mass, though a few spots still reporting SW winds up to 10 kt at 05Z. Dewpts were mainly in the 20s, except mid-upper 30s along the S coast, Cape Cod and the islands. Only exception was at KMVY where T/Td down to 26 degrees, the coldest spot across the region at 05Z. Will continue to see high clouds stream across the region from low pressure across E TN/KY as seen on latest satellite trends. Will continue to monitor for more patchy fog along the immediate S coast as T/Td spreads lower especially across the outer Cape and islands. Will also continue to monitor temp trends across SE Mass with the onshore winds off the milder ocean waters. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/... Today... As the surface high moves further offshore, Tuesday will bring developing S to SW wind. A sea breeze is possible along east coastal MA for part of the day, however as the SW flow increases some during the afternoon, the east coastal sea breeze should come to an end. Mostly sunny skies expected for much of the day, with increasing clouds during the afternoon. A slightly warmer day with highs in the 60s across much of the area, some locales may reach 70 degrees. The cooler area will be the immediate south coast of MA/RI, where the persistent S wind will keep highs in the upper 50s to near 60. Tonight... Models show mid level ridging moving east of our area while deep trough currently over the lower Ohio/Mississippi Valleys works its way eastward. This pattern shift prompts a moisture-rich low pressure system to track eastward towards the Delmarva coastline. Moisture well ahead of this system will result in skies becoming cloudy during the evening, but it will take some time to moisten the column with respect to any precipitation. Expecting rain to become likely after midnight. PWATs during the overnight increase to 1 to 1.3 inches, so some moderate rainfall possible but generally thinking rainfall of a tenth to half inch prior to 12Z Wed. Cloud cover and increasing dew points will keep overnight lows somewhat milder, lows in the low to mid 40s for much of the area. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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Highlights... * Scattered showers Wed night with an isolated t-storm possible * Mainly dry+seasonable Thu/Fri/Sat other than a few brief showers * Dry and a bit cooler Sun with moderating temperatures by Mon * Unseasonably warm temps may arrive by the middle of next week Details... Wednesday night... The deeper moisture and forcing will push east of the region Wednesday evening, bringing an end to the widespread rain. However, upper level energy remaining west of the region coupled with surface boundary will result in scattered showers persisting well into the night. In fact...there is enough elevated instability for an isolated thunderstorm or two. Low temps will drop mainly into the upper 40s to around 50 and areas of fog are also anticipated. Thursday... Drier mid level air will be working into the region from the west allowing for partial sunshine. Given the mild start high temps should reach well into the 60s in most locales. Mainly dry weather anticipated...but shortwave/cold pool aloft will move across central and northern New England. We should be on the southern fringe of its main impacts...but given cold pool aloft a few brief showers are possible with the greatest risk north of MA turnpike. Friday and Saturday... Overall...seasonable weather continues for late April. While most of this period will feature dry weather, it is possible a wave of low pressure brings a brief period of showers late Friday if it tracks close enough to the coast. Greatest risk for this will be across southeast New England. As for Sat...while most of the time will be dry a cold front may bring a few passing showers Sat afternoon and evening. Highs Fri and Sat will mainly be in the 60s. Sunday and Monday... Dry weather behind the cold front with somewhat cooler weather Sun. Still a pleasant day though with highs mainly in the 50s to perhaps a few locales near 60 across southeast New England. After a cool start early Monday morning with many locales dipping down into the 30s...highs should recover into the 60s Monday afternoon as rising height fields begin the warming trend. In fact...much of our long range guidance is showing the potential for unseasonable warmth by the middle of next week with upper level ridging building over the eastern U.S.
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&& .AVIATION /08Z TUESDAY THROUGH SATURDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/...High confidence. Overnight...VFR with SCT-BKN high clouds streaming in. Light S-SW or calm winds. Low to moderate risk of MVFR VSBYS in patchy fog across outer Cape Cod, KMVY and KACK. Today...VFR. Prevailing wind from the S-SW, increasing to around 10 kt by midday. Tonight...Mainly VFR. Patches of MVFR conditions after midnight, with local IFR possible towards daybreak across CT valley. -RA moving across the area by around midnight across the CT valley, then shifting E after midnight. Wednesday...Conditions lower to IFR from W-E by midday, with local LIFR possible along S coastal terminals. SE wind gusts up to 25-30 kt across Cape Cod and the islands Wed afternoon. Isolated TSRA. KBOS Terminal...High confidence in TAF. Low risk for possible brief sea breeze late morning to midday today before S-SW winds increase. KBDL Terminal...High confidence in TAF. Outlook /Wednesday Night through Saturday/...Moderate to High confidence. Wednesday Night: MVFR/IFR conditions possible. Windy with local gusts to 30 kt across southeast New England coast during the evening with some LLWS. SCT SHRA, areas BR, isolated TSRA. Thursday: VFR. Slight chance SHRA. Thursday Night: VFR. Friday: VFR. Slight chance SHRA. Friday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Saturday: VFR. Breezy. Slight chance SHRA.
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&& .MARINE...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/...High confidence. Overnight... High pressure across the waters with southerly winds 10 kt or less, seas 1 to 2 feet on the outer coastal waters. Good visibility. Today... S-SW wind increasing over the course of the day to 10-20 kts. Sea breeze along east coastal MA possible late morning or midday, then S winds should prevail as they strengthen. Seas 1 to 3 feet. Tonight... SE winds less than 25 kt. Seas locally approaching 5 ft, especially on the southern outer coastal waters. SCA headlines may be needed. Rain showers becoming likely towards daybreak. Outlook /Wednesday Night through Saturday/...Moderate to High confidence. Wednesday Night: Small Craft Advisory winds with gusts up to 30 kt and a low risk for a few 35 knot gusts early in the evening across the southeast waters. Rough seas up to 13 ft. Chance of rain showers, areas fog, isolated thunderstorms. Visibility 1 to 3 nm. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Slight chance of rain showers. Thursday Night: Winds less than 25 kt. Rough seas up to 9 ft. Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. Friday Night: Winds less than 25 kt. Local rough seas. Chance of rain showers. Saturday: Winds less than 25 kt. Seas up to 5 ft.
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&& .EQUIPMENT... The NOAA Weather Radio transmitter serving Providence is out of service due to phone line problems. The phone company has prioritized the issues and is working to get the weather broadcast back on the air as soon as possible. The transmitter serving Hyannis is back in service. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank NEAR TERM...Belk/EVT SHORT TERM...NMB LONG TERM...Frank AVIATION...EVT/Frank MARINE...EVT/Frank EQUIPMENT...Staff

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