Lexington, Massachusetts, USA
000 FXUS61 KBOX 161900 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 300 PM EDT Thu May 16 2024 .SYNOPSIS... Moderate to heavy rainfall gradually wanes this afternoon giving way to a dry end to the week. Onshore flow will keep temperatures in check along the coast. The weekend features generally dry weather and onshore breezes, but still a good amount of cloud cover. Warming trend then develops Monday through Wednesday, and we could see a couple days of high temperatures in the low 80s over interior sections of Southern New England. After today, our next chance for rains may not develop until later next week. && .NEAR TERM /THROUGH TONIGHT/... * Rain tapering off from NW to SE as low pressure slides further offshore. * Marine stratus/fog possibly dense at times spreading into central MA/RI eastward tonight. A cutoff low will meander from south of southern New England late tonight to the southeast of our region by early Fri. Behind the cutoff a ridge slides from the Mid Atlantic/eastern Great Lakes into western New England by early Fri. Low pressure south of Long Island late today will rotate southeastward tonight, while high pressure nudges in from Upstate NY. Main change to the forecast was slightly slow down precipitation tapering off from the low meandering offshore. Think for the MA-Pike northward things should end by this evening, but may not be until 10 PM to midnight for precip to cease for the MA-Pike southward. This will take the longest for MVY/ACK. Fortunately the heaviest precipitation is over with as the mesoscale band that set up is falling apart. This axis of precip will slide southeastward. Leaned pretty heavily on the previous ARW and current NSSL WRF as it is handling this band quite well based on observations. The other main concern to the forecast for tonight is given the onshore flow am anticipating marine stratus/fog along with some drizzle to spread into southern New England. This has been hinted at by the past two cycles of the HREF and several GLAMP runs. Have trended the forecast in this direction tonight for central MA/RI eastward. Not out of the question there could be some spots where the fog is dense, but not completely certain on this risk at this junction as guidance is all over the place. Something we will need to monitor given the prolonged ENE to NE flow as it could linger into the Fri AM commute. Cloud cover will be slow to clear for most other than portions of western MA/CT as this is closer to the high nudging its way in. Not expecting much radiational cooling and think the 50th percentile of guidance looks reasonable at this point. Lows in the low/mid 50s. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... Highlights * Any stratus/fog anticipated to erode Fri AM. Mix of sun and clouds through Fri. * Increasing clouds Fri Night into early Sat. Could see the stratus/fog returning to portions of eastern MA. Ridge axis over western New England early on Fri builds over southern New England and into the Gulf of ME by late in the day. The ridge essentially remains in place as we head into Fri Night, but may flatten out a bit as a shortwave lifts across the eastern Great Lakes into northern New England. A weak high nudges into New England on Fri and Fri Night. Dry and quiet weather anticipated on Fri with high pressure in control. Should see any of the lingering stratus/fog burning off by mid to perhaps late AM. Will still have prolonged ENE to NE winds, but think given the breaks of May sun we should warm up quite nicely. Should see 925 hPa temps of 11-15 Celsius. The result should be widespread highs in the 60s with some mid 70s across the CT River Valley. Still may struggle to hit 60 degrees for portions of the east coast given the onshore winds, but will still have roughly 15-30 kt ENE to NE LLJ at 925. Should result in a fairly well mixed boundary layer, which should keep our temps up. It will be a bit breezy into the afternoon. Still anticipating dry and quiet weather to persist as we head into Fri Night/Sat AM. Though we will see increasing cloudiness as the ridge axis gets shunted to the south due to the shortwave lifting in. Not a whole lot of moisture to work with in the mid levels, but there is increasing low level moisture per 1000-850 hPa RH fields. Should have PWATs of 0.75 to roughly 1 inch. At this point leaning on a dry forecast, but the ECMWF does eek out some spotty showers across the interior. Think there is a better shot given prolonged ENE to NE winds that we see another round of marine stratus/fog/drizzle across eastern areas heading into Sat AM. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Highlights: * Other than a spot shower, mainly dry weather prevails with partly to mostly cloudy conditions, along with onshore breezes this weekend. * Warming trend Mon through Wed, with less cloud cover. Could see a couple days of highs in the lower 80s inland. Details: Today's global model ensembles from the 00z cycle have trended the forecast in a more optimistic direction, as a closed upper level circulation initially over the western Appalachians becomes parked over the mid-Atlantic/Chesapeake Bay vicinity this weekend. Surface ridge stretching from Nova Scotia southwestward through Southern New England is progged to remain in place for several days, at least into the early to midweek timeframe. In addition, there continues to be indications of a warming trend to temperatures by the early to mid next week period as 500 mb shortwave ridge extends into Southern New England. These were trends noted over the last day or two and there is now a greater degree of agreement on this anticipated warming trend Monday thru Wednesday. Other than a couple hit or miss showers, drier weather looks to predominate; we may not see widespread rains develop until late next week. The Weekend: Surface ridge of high pressure extending in from Atlantic Canada will maintain onshore breezes. While generally dry, there should be still a good amt of cloud cover around with partly to mostly cloudy sky conditions. Expect high temperatures to be coolest near the coast given the cooler onshore flow, in the upper 50s to lower 60s. High temperatures further inland still project considerably warmer, but how warm they get will depend on if we can see any cloudy breaks/stronger heating; offered highs well into the 60s to the lower 70s, but there is room for warmer temperatures if we see less cloud cover than anticipated. Monday through Wednesday: High pressure still governs at the surface, but we'll be adding 500 mb height rises. 850 mb temps warm to the +10 to +12C neighborhood and with less cloud cover, highs inland could be pushing into the lower 80s, with mid 60s to mid 70s in the coasts and the immediate coastal plain with potential for seabreezes to develop. && .AVIATION /18Z THURSDAY THROUGH MONDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through 00Z...High confidence. MVFR to IFR conditions with rain tapering off from NW to SE for most. Though spotty rain may continue across portions of the south coast into this evening. Winds out of the ENE to NE at 10-20 kts with gusts of 20 to 35 kts. Should see those strongest speeds/gusts along the immediate south coast. Tonight...Moderate confidence. Western interior terminals may briefly improve to VFR this evening before lowering to MVFR/IFR as stratus spreads in. Leaned more pessimistic for central MA/RI eastward due to prolonged ENE to NE winds (onshore flow). Anticipating that the marine stratus/fog layer spreads in lowering us to IFR and LIFR conditions. Could even see some dense fog in spots, especially across portions of Cape/Islands. For now kept things no worse than 1/2 SM, but may need to be adjusted in future updates. Winds out of the ENE to NE at 5-15 kts. Still could see 20-30 kt gusts across MVY/ACK. Friday...High confidence in trends, moderate in timing. Widespread VFR after any stratus/fog burns off by roughly mid to late AM. Though may not be until the afternoon for ACK. Winds out of the ENE to NE at 5-15 kts with gusts of 20-25 kts across the Cape/Islands. Friday Night...Moderate confidence. VFR for most with increasing mid/high clouds. The only exception is across eastern MA, but especially SE MA where MVFR/IFR stratus/fog spreads in late. NE winds at 5-15 kts. KBOS TAF...High confidence through 00Z, moderate afterward. MVFR conditions persist with light rain gradually tapering off. Gusty NE to ENE winds continue through roughly 01Z. Prolonged onshore flow will advect IFR to LIFR stratus onshore tonight along with some spotty drizzle. Uncertainty highest in the visby as there are some indications that the fog could be dense for a few hours 04-09Z window. May not be until 13-15Z where the stratus/fog burns off due to the prolonged onshore flow. KBDL TAF...High confidence in TAF. Rains tapering off with MVFR persisting into the evening. Could have brief improvement to VFR this evening before borderline MVFR/VFR ceilings spread in late. Should see this lift to VFR early on Fri as the boundary layer grows. Outlook /Saturday through Monday/... Saturday through Sunday: VFR. Sunday Night: Mainly VFR, with local IFR possible. Monday: VFR. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight...High confidence. Rain tapering off across the southern waters north to south for most before midnight, though the far outer southern waters may not be until daybreak. Winds ENE to NE at 10-20 kts with gusts 20-30 kts gradually easing heading into Fri AM. Patchy to areas of stratus/fog with visibility's of 1/2 to 4 SM. Could even see some spot where fog is dense at times. Friday... High Confidence. Any pockets of fog burning off by mid to late Fri AM. E/ENE winds 15-20 kt with 20-25 kt gusts. Seas remain elevated across the outer waters, so the SCA remains. Friday Night...High confidence. Winds remain out of the NE at 10-20 kts. Could see a return of stratus/fog across the waters late. Visibilities of 1-4 SM with the lowest across the eastern waters. Seas remain elevated so have extended the SCA through the period. Outlook /Saturday through Monday/... Saturday through Monday: Winds less than 25 kt. Seas up to 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ231- 233-234. Small Craft Advisory until 11 PM EDT this evening for ANZ232- 236. Small Craft Advisory until 2 AM EDT Friday for ANZ235-237. Small Craft Advisory from 7 PM this evening to 8 AM EDT Saturday for ANZ250. Small Craft Advisory until 8 AM EDT Saturday for ANZ254>256. && $$ SYNOPSIS...Loconto/BL NEAR TERM...BL SHORT TERM...BL LONG TERM...Loconto AVIATION...BW/BL MARINE...BW/BL
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