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Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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026 FXUS61 KBOX 181117 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 717 AM EDT Wed Sep 18 2024 .SYNOPSIS... High pressure continues to support warm and mainly dry weather through this afternoon. We`ll have our next chance for measurable precipitation later tonight. Greatest chances should be confined to Cape Cod and the Islands. Otherwise, mainly dry with mostly cloudy conditions and blustery NE winds this weekend into early next week. && .NEAR TERM /THROUGH TONIGHT/... Mainly tweaks to the forecast this morning. Low clouds and fog should dissipate rather quickly this morning across interior southern New England, but take longer across the Cape and islands. Brought temperatures back in line with observed trends. 3 AM Update Dense fog advisory in effect through 14Z. Areas of dense fog in the CT River Valley and across southeastern MA and RI will slowly mix out by late morning and perhaps as late as early afternoon over The Cape Islands. This will be followed by another mild say with highs in the upper 70s to low 80s and increasing mid-high clouds south of I-90. Expect more sun than clouds for areas north of I-90 away from the coast. Winds become more easterly during the afternoon which should support cloudiness along the east coastline. Some patchy areas of drizzle possibly this morning as well. An area of low- pressure moving north along the mid- Atlantic coast will result in increased rain chances this evening over the south coast Cape and Islands, but showers likely don`t move over the region until the overnight hours. && .SHORT TERM /THURSDAY/... Tonight and Tomorrow Aforementioned area of low pressure slowly moves north and east overnight into tomorrow morning, but eventually begins to meander in response to blocking high pressure over The Canadian Maritimes. Expect showers to develop over the south coast, Cape, Islands, and southeastern MA overnight into tomorrow morning. Winds become northeasterly tomorrow afternoon supporting overcast skies across the region. High temps will be much cooler on THursday in the upper 60s to low 70s, but elevated dewpoints in the mid 60s will support a muggy feel to the atmosphere tomorrow. Some uncertainty in how much rainfall will accumulate, but latest HREF run supports 0.5 to 1 inch of rain across southeastern MA and The Cape with as much as 1.5 inches over The Islands. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... Not much change in the latest guidance suite compared to the past couple of days. Broad agreement continued, but there also remained significant uncertainty in the details. Trended the forecast with this update towards the consensus solution, without making large changes just yet. Overall, expecting a mid level trough to be nearby late this week into early this weekend. At the surface, southern New England should be between two features; a large high pressure to the north, and a low pressure approaching from the south. Ensembles showed most of the uncertainty was more east-west in nature rather than north- south. Thus, still have the greatest confidence in this low pressure center passing near or just SE of the 40N/70W benchmark Thursday night into Friday. This timing is highly uncertain, and could change with later forecasts, even at this relatively closer time range. Another aspect which will need to be monitored closely with this low pressure is coastal flooding. Astronomical tides are rather high later this week. A slow-moving low pressure with persistent winds with at least some onshore component for the south coast of New England may result in pockets of coastal flooding issues late this week. High pressure should then build into our region from the N this weekend into early next week, leading to more dry weather. Temperatures anticipated to trend below normal by this weekend, and continue into early next week. && .AVIATION /11Z WEDNESDAY THROUGH SUNDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today...High Confidence in trends, moderate on timing LIFR ceilings/vsbys improve to VFR between 13-17Z as fog slowly mixes out after sunrise. Winds becoming easterly by the afternoon with shower chances increasing over the south coast by 00Z. Tonight...High Confidence in trends Winds become more northeasterly overnight with showers overspreading southeastern MA, RI, and The Cape/Islands. This will be accompanied by IFR/MVFR ceilings that will persist into Thursday. Tomorrow...High Confidence Showers over southeastern MA, RI, and The Cape/Islands will result in MVFR/IFR conditions with ceilings near 1000 feet. Northeast winds 5 to 10 knots. KBOS TAF...Moderate Confidence VFR with winds becoming onshore by mid morning. MVFR ceilings return overnight with shower chances increasing Thursday morning. KBDL TAF...High confidence in TAF. Outlook /Thursday Night through Sunday/... Thursday Night: Mainly VFR, with local IFR possible. Windy with local gusts up to 30 kt. Chance SHRA. Friday: Mainly VFR, with local IFR possible. Breezy. Slight chance SHRA. Friday Night: Mainly VFR, with areas IFR possible. Breezy. Slight chance SHRA. Saturday: Mainly VFR, with local IFR possible. Windy with local gusts up to 30 kt. Slight chance SHRA. Saturday Night through Sunday: Mainly VFR, with local MVFR possible. Breezy. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Marine Today through Tomorrow Low-pressure approaches the coastal waters this evening and overnight. This result in winds increasing out of the northeast into tomorrow morning when 25+ knot wind gusts will be possible over the coastal waters. Seas will build as well with wave heights rising to 4 to 6 feet over the outer marine zones. A Small Craft Advisory remains in effect for the the south coastal waters through Thursday. Outlook /Thursday Night through Sunday/... Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 8 ft. Chance of rain showers. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 8 ft. Chance of rain showers. Friday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 9 ft. Slight chance of rain showers. Saturday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Slight chance of rain showers. Saturday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Slight chance of rain showers. Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Dense Fog Advisory until 10 AM EDT this morning for MAZ013- 016>024. RI...Dense Fog Advisory until 10 AM EDT this morning for RIZ001>008. MARINE...Small Craft Advisory from 8 AM to 8 PM EDT Thursday for ANZ232>235-237. Small Craft Advisory from 5 PM this afternoon to 8 PM EDT Thursday for ANZ254>256. && $$ SYNOPSIS...Belk/RM NEAR TERM...Belk/RM SHORT TERM...RM LONG TERM...Belk AVIATION...RM MARINE...Belk/RM