Lexington, Massachusetts, USA
000 FXUS61 KBOX 040000 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 800 PM EDT Sat Jun 3 2023 .SYNOPSIS... Unseasonably cool weather will prevail this weekend with gusty northeast winds and periods of rain or drizzle, especially in eastern Massachusetts Sunday and Sunday night. Unsettled weather may linger into early next week, depending on the location of where low pressure sets up. A drying trend with moderating temperatures are possible mid to late next week. && .NEAR TERM /THROUGH SUNDAY/... Not much reason to change the forecast much this evening. Did tweak temperatures to reflect observed trends into the overnight. Thinking temperatures remain nearly steady across the eastern half of southern New England, with temperatures dropping about 5-10 degrees farther west. Greatest rainfall chances and strongest winds remain across the eastern half of southern New England overnight. Previous Discussion... Continuing with a persistence forecast. Upper low over northern New England slowly drops south to Stellwagen Bank overnight, keeping our area under moist N/NE flow which will keep cloudiness locked in along with patchy rain/drizzle, especially closer to coast. Strongest winds should be focused near Cape Cod and Islands through early tonight where we see steeper lapse rates combined with strong winds in lower levels, resulting in better mixing. Tough to time best window for steadier rainfall but 12z HREF seems to have a good idea, indicating one area moving down coast (which can already be seen on radar) toward evening. High Surf Advisory remains posted for eastern MA through Sunday. Obviously very poor beach days but dangerous conditions for anyone observing the rough surf from jetties given large breaking waves onto rocks and other nearshore structures. Always observe from a distance! && .SHORT TERM /SUNDAY NIGHT/... Upper low slowly drifts south to Cape Cod Sunday and eventually south of New England Sunday night. Looks like a better chance of steadier rain by Sunday afternoon, especially near E MA coast, as inverted trough rotates westward toward our area and nose of northerly LLJ brings additional low level convergence. This LLJ will also bring potential for another round of 30-40 mph gusts with focus near Cape Ann. Farther inland, some uncertainty as to how far west rain will make it. We followed depiction shown by HREF which keeps most of activity to east of Worcester, so dry weather is favored in CT Valley and east slopes of Berkshires. Unseasonably cold temperatures will be the big story and we have the potential to break record cold highs for Sunday (see records below). Cold air is focused in lower levels with 925 mph temps cooling to 2-3C across central/eastern MA and RI in heart of cold pool. We nudged highs downward a bit with lower 50s in these areas but it's certainly possible that some locations don't even break 50 degrees! Milder temperatures are expected farther inland where highs should reach 60 in the CT Valley. && .LONG TERM /MONDAY THROUGH SATURDAY/... Latest guidance suite remained rather consistent with the overall synoptic pattern for this portion of the forecast. While still some detail differences remain, they have narrowed to some extent. That said, still favored an ensemble mean/consensus approach with this update. The main weather feature will be a mid level cutoff that is expected to linger between the Maritimes and New England through most of next week. This should also keep a surface low pressure stuck beneath it to our east as well. The risk for showers will wax and wane relative to our proximity to these features. A high pressure moving into the northern central USA for the second half of next week may provided just enough dry air, or nudge that offshore surface low, just far enough east to result in a drier forecast. For now, decided to only trend the forecast drier towards Friday and Saturday. Despite the prolonged risk for showers and possible thunderstorms, still not thinking it will be a total washout. Showers and thunderstorms would be most favored during the afternoon and evening hours most days. Temperatures should be near to slightly below normal through most of this period. Slight warmup anticipated to begin Monday, then be closer to normal by Tuesday. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Moderate confidence. Ceilings should improve to VFR inland tonight but remain MVFR closer to coast. Main change with this update was to keep ceilings mainly MVFR this evening. Thinking there will be a drop to IFR towards the east coast near daybreak. Previous Discussion... Widespread MVFR cigs Sunday with local IFR and light rain across eastern MA, especially in the afternoon, and possibly reaching central MA and RI. Mainly VFR CT Valley. Similar conditions persist Sunday night. N/NE winds prevail through Sunday, gusting to 20-30kt with strongest winds near coast. KBOS Terminal...Moderate confidence in TAF. Forecast is based on persistence with ceilings hanging 010-015, but could briefly drop to IFR at times. KBDL Terminal...High confidence in TAF. Outlook /Monday through Thursday/... Sunday Night: Mainly VFR, with areas IFR possible. Windy with gusts up to 30 kt. Chance RA, chance SHRA, patchy BR. Monday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA. Monday Night: VFR. Chance SHRA. Tuesday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, isolated TSRA. Tuesday Night: VFR. Breezy. Chance SHRA. Wednesday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. * Period of gale force winds near and south of Islands * Rough seas on MA/RI waters due to strong NE winds this weekend Gale Warnings remain posted for waters near and south of Islands. Expecting frequent gusts just over 35kt through early tonight before gusts settle back a bit to 25-30 kt and persist through Sunday night, including the rest of the MA and RI coastal waters. Another surge of wind is expected Sunday afternoon on waters off Cape Ann but at this point it looks marginal to upgrade to Gale Warnings. Main point is strong N/NE winds will continue to produce rough seas on coastal waters through weekend which may make conditions difficult to navigate for less experienced boaters. Seas should average 3-6 feet nearshore and up to 10 feet offshore. Patchy light rain/drizzle expected at times tonight with more widespread light rain Sunday and Sunday night, especially on eastern MA waters. Outlook /Monday through Thursday/... Monday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Chance of rain showers. Monday Night: Winds less than 25 kt. Local rough seas. Chance of rain showers. Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers. Tuesday Night through Wednesday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers. && .TIDES/COASTAL FLOODING... Key Points: * Splashover possible tonight along E MA coast - little impact * Better chance of widespread minor flooding Sunday night and Monday night Combination of high astro tides (11+ ft MLLW for Boston) combined with strong NE flow may result in minor coastal flooding along eastern MA coast. Our main tides of concern are the Sunday night and possibly Monday night high tide cycles. For high tide late tonight, we are only expecting a surge of up to 1 foot which is only expected to result in some splashover of the most vulnerable shore roads with little impact, mostly as a result of wave action. The Sunday night high tide looks to have a higher risk of minor flooding since the tide is a little higher and the surge may reach 1.0 to 1.5 feet along with continued wave action. Thus, we may need to issue a Coastal Flood Advisory in later forecasts since more of the E MA coastline, including Cape Cod and the Islands, would be impacted. There is also a risk of minor flooding during the Mon night high tide. Along the South Coast, surge values will be lower due to offshore flow (NE winds). Locations such as Providence are forecast to remain well below flood stage. There is also a risk of minor flooding during the Mon night high tide. && .CLIMATE... Record Low Max Temps for Sunday June 4th. BOS...52/1891 PVD...55/2012 BDL...59/2018 ORH...51/2018 && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...High Surf Advisory until 8 PM EDT Sunday for MAZ007-015-016- 019-022-024. RI...None. MARINE...Small Craft Advisory until 8 AM EDT Monday for ANZ230-231-237- 250-251-254. Gale Warning until midnight EDT tonight for ANZ232>235-255-256. Small Craft Advisory until 2 AM EDT Monday for ANZ236. && $$ SYNOPSIS...Belk/JWD NEAR TERM...Belk/JWD SHORT TERM...JWD LONG TERM...Belk AVIATION...Belk/JWD MARINE...Belk/JWD TIDES/COASTAL FLOODING...Staff CLIMATE...Staff
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