Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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561 FXUS61 KBOX 072348 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 748 PM EDT Fri Jun 7 2024 .SYNOPSIS... Cooler tonight, then mainly dry and seasonable conditions Saturday. Scattered showers on Sunday with diminishing rain chances through Tuesday. Warming and drying trend Wednesday and Thursday, before unsettled conditions return to round out the weekend. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 8PM Update... Hi-res guidance overestimated both the coverage and intensity of shower activity this evening, with just some isolated downpours popping up along the waning sea breeze boundary and some more stratiform shower activity across central and western MA. With poor lapse rates, storms weren`t really able to grow taller than 18k ft so it`s no surprise that lightning was unable to develop with the -10C altitude somewhere around 24k ft. Cold front dropping southeast was able to generate some interesting looking cloud features, with a few photos streaming into the office of what appears to be a roll cloud, but overall, it was a pretty low impact evening across SNE. With winds becoming W behind the weak frontal boundary, fog should be much less widespread than last night, with no further impacts expected for the interior or Boston metro area. Fog will hang on across the Cape this evening and early tonight, through about 06/08Z before winds shift to the west and dewpoints fall. southwest flow will keep dewpoints elevated for the Cape into tomorrow morning, which will impact how quickly fog dissipates. Previous update... Some pop-up showers developed beneath a cold pool aloft. These were mainly across NY state and northern New England. Another band of showers developed across portions of RI and eastern MA, but required help from seabreeze boundaries to overcome the less favorable instability towards the coast. While these showers were locally heavy, they were still not tall enough to be concerned about thunderstorms. These showers are expected to dissipate as they move onto the ocean side of the seabreeze boundaries. The risk for showers should continue through midnight. Main concern tonight will be the return of stratus and fog along portions of the coast. Drier air will try to push SE across southern New England overnight, but it will take time to reach the coast. The most likely areas will be the Cape and islands again. An east wind this afternoon also brought some stratus and fog into portions of the east coast of MA. As long as the wind remains from the east, it is unlikely this will dissipate or move out. Currently thinking winds become southerly towards sunset, which will begin that process. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Trending less humid for Saturday, but still the low risk for a spot afternoon shower. The greater risk will be towards northern New England. A stronger west wind should keep the seabreeze at bay, meaning high temperatures along the immediate east coast. Clearing for a brief time Saturday night. More clouds and a risk for showers could arrive late Saturday night ahead of another weak low pressure. Above normal temperatures continue. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Highlights * A mix of showers and sunshine on Sunday * Some spot showers possible Monday/Tuesday before what looks to be a drying trend mid week * Unsettled conditions possibly return late next week with trough developing in the vicinity of the northeast Sunday... Sunday is shaping up to be the wettest day of the long term period with cutoff low quasistationary in southern/central Quebec. Southwest surface to 925mb flow will allow PWATs/dewpoints to surge back above 1.25"/mid 60s. More robust shortwave, at least compared to what we`ve seen the last few days, will scoop across the northeast beginning Sunday morning, but is rather slow to move seaward so should produce showers for the better part of the day. Still, the day doesn`t look like a washout, but anyone with outdoor plans may want to pack an umbrella. Thunderstorm potential remains low on Sunday with modest CAPE, between 400-600J`kg, but as is often the case here in SNE, mid level lapse rates are lackluster, perhaps just touching 6.5C/km. So, while we can`t rule out a few rumbles of thunder in the strongest cold pool convective showers, we do not anticipate severe weather. Monday and Tuesday... Upper level cutoff shifts northeast of the region to start the work week, but lagging shortwave trough will yield scattered shower activity for Monday and Tuesday, particularly across northern Massachusetts, with lingering cold pool aloft (850mb temps may drop as low as 0C across upstate NY late Monday). Cold pool showers will be fighting against a drying column as PWATs again drop to 0.75", so overall expect shower activity to be much more sparse compared to Sunday. Expecting more sun than clouds both days with diurnal cumulus developing each afternoon. Even with cold pool aloft, W/NW downsloping should support temperatures slightly above to near normal, in the mid to upper 70s, perhaps touching 80F in the warmest locations. Mid to Late Week... Very persistent trough/cutoff upper low finally relinquishes its grasp on southern New England by Wednesday as ridging builds in from the southwest. There remains uncertainty in how strong ridging will be, but it should provide a brief lull in unsettled conditions as high pressure settles in the vicinity of the region through Thursday. Temperatures also look to trend in a warmer direction as we progress through the week as southwest winds develop behind the departing trough. Global guidance shows another trough sliding southeast from the Great Lakes/southern Ontario to round out the work week/start next weekend, but remains varied in timing and strength of the feature. So, while it looks like unsettled conditions will return by Friday/Saturday, specific details won`t be sussed out for several days. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Some isolated showers and downpours possible through the midnight hour tonight, but generally VFR away from the Cape and Islands. Winds generally light becoming west behind passing weak frontal boundary. IFR/LIFR in stratus and fog near ACK and along portions of the east coast of MA should become more widespread this evening, at least until winds turn SW to W and drier air overspreads our region. The most likely impacted region will be across Cape Cod and perhaps the south coast. Mainly VFR Saturday and Saturday Night. Can`t rule out brief MVFR in spotty showers Saturday afternoon. KBOS TAF...Moderate confidence. Fog bank just to the east of the terminal will threaten the field with LIFR conditions as long as there is an E wind. Still expecting winds to turn S this evening, but current timing in the TAF may be too fast. KBDL TAF...High confidence. Outlook /Sunday through Wednesday/... Sunday: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA. Sunday Night: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA. Monday: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA. Monday Night: VFR. Tuesday: Mainly VFR, with areas MVFR possible. Slight chance SHRA. Tuesday Night: VFR. Wednesday: Mainly VFR, with local MVFR possible. Slight chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. High confidence through Saturday. SW to W winds develop overnight. Before that happens, areas of poor visibility in fog around the Cape and islands. Improving visibility late tonight through Saturday night. A few gusts up to 25 kt possible Saturday afternoon. Otherwise, expecting seas to gradually subside tonight. Small Craft Advisory continues for marginal 5-foot seas across the outer southern coastal waters. Outlook /Sunday through Wednesday/... Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers. Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Monday Night: Winds less than 25 kt. Tuesday: Winds less than 25 kt. Slight chance of rain showers. Tuesday Night through Wednesday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 5 AM EDT Saturday for ANZ255. Small Craft Advisory until 10 PM EDT this evening for ANZ256. && $$ SYNOPSIS...Belk/KS NEAR TERM...Belk/KS SHORT TERM...Belk LONG TERM...KS AVIATION...Belk/KS MARINE...Belk/KS