Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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074 FXUS61 KBOX 111446 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1046 AM EDT Tue Jun 11 2024 .SYNOPSIS... Pleasant temperatures again today and tomorrow with a low chance for an isolated shower. High pressure moving off the coast will allow warmer temperatures for Thursday and humidity by Friday. An approaching cold front will bring the risk for scattered showers and thunderstorms Friday afternoon and evening. High pressure builds in for the weekend bringing beautiful dry weather with pleasant temperatures and low humidity. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1030 AM Update: Forecast in general is holding up pretty well; only real noticeable change was to change the wording of showers from probability wording (slight chance) to areal coverage wording (isolated). As temps are nearing convective temperatures given the cool pocket of air aloft associated with upper level trough in proximity to Southern New England, we`re starting to see an increasing coverage of cumulus develop per visible satellite and METARs. It still looks as though areas around or west of I-495 in MA into interior CT/MA/NW RI has the better chance at a diurnally-driven hit-or-miss shower, although drier weather prevails much of the time. Highs in the lower to mid 70s still look on track, with temps in the upper 60s near the coastlines as seabreezes develop over the next hour or so. Previous discussion: * Diurnal clouds developing later this morning & afternoon, but with nothing more than a few brief spot showers later today * Highs mainly in the lower to middle 70s Previous forecast is on track. Plenty of diurnal CU develop later this morning and afternoon underneath cold pool aloft...but with nothing more than a few spot showers. Earlier discussion below. Upper level closed low remains centered over Southern New England today with high pressure building in from the west. Diurnal cumulus will quickly form this morning with 850mb temps around +8C leading to convective temps only around 70F. With diurnal cumulus forming in the early to mid morning, high temperatures will likely be cooler then yesterday, only reaching the low to mid 70s. Closer to the coasts, sea breezes should form in the mid to late morning capping high temps in the upper 60s to low 70s. Dewpoints remain in the lower to middle 50s today making it feel very comfortable outside. Despite the clouds...dry weather dominates but do expect a few diurnally driven spot showers during the afternoon/early evening. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Tonight: Diurnal cumulus will dissipate quickly with sunset allowing for mainly clear skies overnight. Winds will also remain light overnight allowing for good radiational cooling. Overnight lows drop into the mid to upper 50s again. Tomorrow: Upper level closed low begins to move NE, but remaining under cyclonic flow for much of the day. Wednesday will ultimately be very similar to Tuesday with diurnal cumulus forming mid to late morning and low chance for isolated low topped showers. Thinking the best chance for these showers on Wednesday will be near the sea breeze front providing a little bit extra convergence and forcing. High temps look to be just a bit warmer Wednesday in the mid to upper 70s with WSW flow. Dewpoints begin to climb into the upper 50s making it feel a bit more humid then Tuesday. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Key Points... * Dry but warm Thu with highs mainly middle to upper 80s * Warm & Humid Fri with afternoon/eve scattered showers & t-storms * Beautiful next weekend with low humidity & temps a tad below normal Details... Thursday... Ridge of high pressure slides off the coast allowing warmer southwest flow of air to develop across the region by Thu. 850T warming to between +14C/+15C should allow afternoon highs to reach the middle to upper 80s in many locations. Southwest winds will result in somewhat cooler temps near the south coast...where 70s to lower 80s will be more common. Humidity looks to remain in check Thu and given mid level ridge axis crossing the region...dry weather will prevail. Friday... Shortwave trough and an associated cold front will approach from the west on Friday. Timing still somewhat uncertain...but expect humidity to return ahead of an approaching shortwave/cold front. Highs should reach well into the 80s to near 90 as long as we receive enough solar insolation with dewpoints climbing into the 60s. Thinking at least some modest instability with 0-6 KM shear increasing to between 40 and 50 knots. Enough forcing with the shortwave should generate the development of scattered showers & t-storms. Timing still uncertain this far out. We can not rule out some elevated activity in the morning...but main risk for scattered showers & thunderstorms will be during the afternoon/evening hours. Given the parameters in place...we will need to watch the risk for severe weather and localized heavy rainfall with the activity. That being said...it is too early to assess at this point but something to watch. This Weekend... Large Canadian high pressure builds in for the weekend. This brings beautiful/dry weather for the weekend with low humidity and temps a tad below normal. Highs will be 70s to near 80 with overnight lows mainly in the 50s with even some upper 40s possible. Monday.... High pressure moves off the coast on Monday...allowing for a return southwest flow of warmer air to begin moving into the region. Upper level ridging building north should result in dry weather continuing too. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 15z TAF Update: High confidence. Today: VFR. Localized sea breezes forming ~15-17z with speeds around 6-18 kt, otherwise light WNW winds. Isolated to widely scattered -SHRA possible but felt it was too low a probability for a TAF mention; if any develop, it wouldn`t be enough to cause restrictions. Tonight: Mainly VFR. Calm/light & variable winds. Patchy ground fog may develop late in the typically prone locations and perhaps parts of the Cape/Islands. Wednesday: VFR. Localized sea breezes form again, otherwise light WSW winds. Low chance for an isolated afternoon shower again. KBOS TAF...High confidence in TAF. SCT-BKN VFR bases. Sea breeze should develop by 15z. Outside shot at a -SHRA 17-22z but too unlikely to mention in TAF. Sea breeze kicks out between 01z-03z with winds coming around to light WNW by pre-dawn. Somewhat better chance at -SHRA on Wed with sea-breezes starting around 15z. KBDL TAF...High confidence in TAF. SCT-BKN VFR bases. Isolated shower possible but too unlikely to mention in TAF. Light WNW winds. Outlook /Wednesday Night through Saturday/... Wednesday Night: VFR. Thursday through Thursday Night: VFR. Breezy. Friday: Mainly VFR, with local IFR possible. Breezy. Scattered SHRA, scattered TSRA. Friday Night: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, isolated TSRA. Saturday: VFR. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today: Tranquil boating weather with light WNW winds turning southerly in the afternoon. Seas 1-3 feet. Tonight: Areas of fog possible especially east of the Cape and Islands. Light southerly winds. Seas 1-2 feet. Tomorrow: Fog may linger east of the Islands, otherwise another pleasant day. Winds remain light and southerly. Seas 1-2 feet. Outlook /Wednesday Night through Saturday/... Wednesday Night through Thursday: Winds less than 25 kt. Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Friday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Scattered rain showers. Friday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Frank/KP NEAR TERM...Frank/Loconto/KP SHORT TERM...KP LONG TERM...Frank AVIATION...Frank/Loconto/KP MARINE...Frank/Loconto/KP