Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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739 FXUS61 KBOX 250641 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 241 AM EDT Tue Jun 25 2024 .SYNOPSIS... A disturbance aloft over the Northern Adirondacks moves southeastward tonight, bringing evening cloudiness, northwest breezes and a drier air mass to Southern New England. Warmer temperatures then return for Tuesday but humidity levels remain comfortable. Increasing humidity levels on Wednesday with the risk for showers and thunderstorms, and some could become strong. Drier and less humid to end the workweek, although summerlike warmth and humidity return by this weekend. && .NEAR TERM /THROUGH TODAY/... 220 AM Update... Forecast remains on track. No changes in the latest update. 11 PM Update... Have added likely showers across eastern MA. Latest NSSL WRF handling activity associated with the upper trough swinging through quite well. Should see these showers through roughly 1-3 AM as they diminish with the upper wave lifting offshore. Otherwise forecast generally on track at this point with only minor adjustments. Previous discussion... So for tonight, shortwave disturbance aloft and its cool pocket of air aloft will be moving through the interior Northeast and offshore through midnight. The approach of this disturbance should at least maintain cloud cover if not increase it a bit. Think cloud cover should trend more partial to mostly cloudy. An outside chance (20% or less) of a sprinkle or light shower as the shortwave moves through. Am a little skeptical the coverage will be as numerous as some of the high res models indicate with drier air moving into the lowest hundred or so mb of atmosphere. Carried a mention of isolated showers but with nil QPF over northern and northeast portions of Southern New England, but many areas however stay dry. Should also see more northwesterly breezes for the evening and overnight, which will continue to usher in lowering dewpoints and a more comfortable air mass. Humidity levels should be low enough tonight to give fans/ACs a break for more open-windows. Lows tonight in the mid 50s to lower 60s, with mid 60s out over Cape Cod. && .SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/... Brief shortwave ridge and weak high pressure will bring very pleasant weather again tomorrow. Mid level winds turn SW Tuesday afternoon allowing for 850mb temps to warm from +13C to +17C. This will bring high temperatures back into the upper 80s to low 90s. With westerly surface winds, dewpoints will remain in a comfortable range in the upper 50s. Skies should remain mostly sunny through the day with subsidence aloft helping suppress diurnal cumulus. Late in the day, mid to high level cirrus clouds may bring some filtered sunshine ahead of a weak shortwave moving through overnight. Surface winds turn southwest overnight, brining moisture rich flow into the region. This will bring dewpoints back into the low to mid 60s. Winds overnight also turn gusty at 15-20mph as the pressure gradient tightens ahead of the next system for Wednesday. This will keep overnight temps quite warm in the upper 60s to low 70s near urban centers. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights: * Wednesday is hot, muggy, and late day thunderstorms. A few showers could linger into Thursday morning across southeastern parts of southern New England. * A post-frontal airmass provides relief from the heat and muggies late this week, along with drier conditions. * Upcoming weekend looks splits, with the unsettled conditions likely on Sunday. Rain and thunderstorm chances increase the second-half of Wednesday with a mid-level trough and shortwave passage. For now, most of the daylight hours Wednesday appear dry. Deep southwest flow ahead of the approaching front advects a warm/moist airmass into southern New England. Likely a hot and muggy day with highs in the upper 80 to lower 90s, with dew points near 70F, courtesy of PWATs nearing the two inch mark. Combination of heat and humidity provides instability for storms late day. Best forcing at this time comes around late afternoon and evening and exits during the overnight hours. The discussion earlier stated a remnant EML from the upper Midwest could be in the vicinity late in the day, 21z-ish, but latest 12z model guidance suggests this feature could be over us by 12z/15z. There is still some uncertainty with how strong and widespread these storms could become. But there are signs for a few stronger storms, SREF has surface based CAPE around 1,000 to 1,500 J/kg, along with modest wind shear, 30 to 40 knots. Additionally, the 12z CSU machine learning probs for severe weather/winds did back off slightly across the northeast, though maintained the greatest risk for severe weather across the Mid Atlantic states. Did maintain the greatest pops between 00z and 10z, though there could be lingering showers on Thursday morning as the front is slow to exit the coastal waters. Places like Cape Cod and the Island could see a few showers up until lunch before improving. It`s important to note, those seeking a bit of relief from the heat and muggy conditions at the ocean, there is a chance for stronger rip currents. While there are no headlines, yet, future updates may include a statement or advisory for this hazard. Comfortable conditions Thursday with a post-frontal airmass due to surface surface high moving down out of central Canada into northern Great Lakes region. Drier weather to follow the rest of Thursday into Friday, daily highs in the upper 70s and low 80s, dew points are in the low 60s on Thursday and 50s on Friday. Heading into this coming weekend, potentially a split weekend with drier weather on Saturday with showers and thunderstorms on Sunday. Model guidance suggests a system developing across the northern Great Lakes with a trailing cold front. Still too early to get into the details, but looks as if the later half of the weekend could be unsettled. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through 12Z...High confidence. Generally anticipating VFR conditions. Though may take until 08-09Z for the Cape/Islands to see improvement at MVFR/IFR conditions linger as light showers move through. Could perhaps see some patchy fog at prone BED given recent precip and light winds until 11Z. Have handled with tempo given not super confident on the winds completely decoupling. Winds out of the NW at 5-10 kts. Tuesday...High confidence. VFR conditions expected with mid/high clouds beginning to move in late afternoon/evening. Winds shifting from the NW to the W/WSW by the afternoon. Should have speeds of 5-10 kts with gusts of 15-20 kts. Tuesday Night...High confidence. VFR with mid to high clouds continuing to increase. Winds out of the SW at 5-15 kts. Could see some 15-25 kt gusts after 06Z with the highest speeds along the immediate south coast. Wednesday...High confidence in AM. Lowers to moderate for PM. VFR conditions are anticipated for much of the day. Confidence lowers to moderate during the afternoon/evening as a cold front triggers showers and thunderstorms. Not certain at this point on coverage and exact timing, but risk seems highest across CT into interior MA. If individual storm moves over terminal could see brief MVFR to IFR conditions. Not out of the question there are strong to damaging wind gusts if a stronger storm or two can develop. Winds out of the WSW/SW at 10-15 kts with gusts of 20-30 kts. KBOS TAF...High confidence. VFR through the forecast. Winds remain too strong out of the NW to WSW today, which will keep the seabreeze at bay. Could have some 15-20 kt gusts through the afternoon before the boundary layer decouples roughly 23-01Z. KBDL TAF...High confidence in TAF. VFR through the forecast. Could see gusty winds developing around 15-17Z today as the boundary layer deepens. Outlook /Wednesday Night through Saturday/... Wednesday Night: Mainly MVFR, with areas VFR possible. Breezy. SHRA likely, slight chance TSRA. Thursday: VFR. Chance SHRA. Thursday Night through Friday Night: VFR. Saturday: VFR. Breezy. Slight chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight... High pressure begins to move in allowing winds to turn north and weaken to 10-15 knots. Seas also decrease 3-6 feet. Tomorrow... Mainly clear conditions with winds turning SSW. Gusts begin to ramp up again in the southern waters to 20-25 knots. Seas decrease to 2-4 feet Tomorrow night... Southwesterly winds continue to ramp up across all the waters with gusts up to 30 knots again. Seas ramp back up to 3-6 feet. Small Craft Advisories will likely be needed for the this period. Outlook /Wednesday Night through Saturday/... Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. Rain showers likely, isolated thunderstorms. Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Friday through Saturday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 3 AM EDT early this morning for ANZ232>235-237. Small Craft Advisory until 3 PM EDT this afternoon for ANZ254>256. && $$ SYNOPSIS...Loconto/Dooley/KP NEAR TERM...Loconto/BL SHORT TERM...KP LONG TERM...Dooley AVIATION...BL MARINE...Dooley/KP