Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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069 FXUS61 KBOX 070742 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 342 AM EDT Sun Jul 7 2024 .SYNOPSIS... Very warm and humid weather conditions continue into next week. Overcast conditions this morning gives way to partly to mostly sunny skies today, except for the south coast. Other than a hit or miss thunderstorm or two near Interstate 95 today, dry weather is expected. Still fairly humid late week, though temperatures are slightly less hot, along with better rain and thunderstorm chances late week as the remnants of Beryl moves towards the northeast. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 335 AM Update: Another pea-soupy early morning across Southern New England, and with few exceptions (northeast MA), most of the area is blanketed in low clouds and/or fog. Fog is most persistent and locally dense along the immediate coastline, with visbys elsewhere in the 1 to 5 mile range. Not really seeing widespread dense fog so SPS for fog issued early in the overnight still looks valid. Otherwise, we`re stuck in a weak sea-level pressure pattern with surface trough axis from coastal ME/NH SSW through the North Shore into northeast NJ. A rogue shower was near New Bedford, but it is largely dry otherwise with scattered heavier showers well south of the Islands. Current temps were in the low to mid 70s. Similar dewpoints were observed as well, although they were falling into the mid to upper 60s in the Berkshires and eastern NY. For today, we should see low clouds and fog gradually scattering out, soonest in northern MA, and around mid to late morning to the I-95 corridor. For the South Coast, Cape and Islands, there looks to be little if any substantial improvement in lower clouds; given those expectations, high temperatures are expected to be cooler there in the upper 70s to lower 80s. However dewpoints should be the highest for those locations today in the low to mid 70s with southerly winds. Skies should trend toward partly to mostly sunny conditions north and west of I-95 once stratus erodes, with a drop in dewpoints into the mid to upper 60s and a lighter WSW flow. Highs elsewhere should reach into the mid 80s to low 90s, though seabreezes keep the eastern coastline on the cooler end of that range. Generally dry for the vast majority of the area. But some mesoscale signals of isolated to widely scattered thunderstorms developing along a weak windshift boundary within the I-95 corridor, produced between the WSW winds in the interior and the SSW winds in southeast New England. After low clouds dissipate and heating gets going, NAM/RAP instability profiles near this boundary are significant, to around 2000-3000 J/kg of surface based CAPE. It may only be a couple storms if they develop at all, but felt it was enough to sketch an area of isolated thunderstorms around 1-8 PM from roughly northern portions of Windham, Providence, southern Worcester, southern Norfolk and northern parts of Bristol and Plymouth counties. That`s where there is some loose consensus on where that boundary sets up. These storms could produce lightning and heavy downpours, but severe weather at the moment seems unlikely from these storms. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... 335 AM Update: Tonight: Lather, rinse and repeat: another very warm and muggy night for Southern New England. Low clouds and fog over the south coast are also expected to return back northward at least into the southern roughly third of Southern New England. The exact northward extent is in some question but could make it as far north as the Mass Pike. Lows in the upper 60s to mid 70s. Monday: Low clouds and fog scatter out and/or retreat into the waters again during the morning hours, giving way to mostly sunny conditions for most of the area. The Cape and Islands should still see periods of low clouds around, but there should be a few more hours of sunny breaks. Monday is very warm to hot and humid, with highs in the upper 80s to low 90s away from the southern coast, bringing heat indices into the lower to mid 90s. Along the south coast, Cape and Islands, highs should reach into the upper 70s to mid 80s. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights: * Hot and humid conditions Tuesday and Wednesday, turning seasonably warm and still quite humid towards later in the week. * Daily shower chances Tuesday and Wednesday, potentially widespread rainfall late in week with the arrival of the remnants of Beryl. Little change to the forecast with the synoptic pattern featuring a mid-level ridge of high pressure centered over Bermuda. This type of setup continues the persistent southwest flow, which funnels higher than normal moisture into southern New England. Additionally, 850mb temperatures Monday through Friday do stay above normal, which boils down to a warm/hot and humid week ahead. Getting caught up in this deep southwest flow are bursts of shortwave energy that will ride the outer periphery of the subtropical ridge, leading to periods of rain and thunderstorms. Temperatures: There is fairly good model agreement that Tuesday and Wednesday will be rather hot, with 925mb temperatures forecast between +24C to +26C and this would lead to surface temperatures between the upper 80s and lower 90s. That said, the southwest winds will lead to slightly `cooler` temperatures along the southern coast of Rhode Island and southeast Massachusetts around the lower 80s. And when you combine the high dew points, it will feel much hotter. Heat Index values on Tuesday are between 95F and 99F for much of the Connecticut River Valley and I-495 corridor. More in the way of clouds on Wednesday will probably result in somewhat lesser values, between 90F and 95F in similar locations. Late week, 925mb settle at +20C to +22C with slightly more seasonable highs in the lower to middle 80s. But will not come with any relief from the high humidity. Precipitation: As we`ve discussed the past couple of days there is no large scale forcing to be had due to vast mid-level/subtropical ridge. There are bursts of shortwave energy on Tuesday and Wednesday that will promote pop-up showers and thunderstorms. Given the high PWATs, localized heavy downpours could be expected with any given cell that develops. Later in the week, PWAT anomaly are 2-3 standard deviation above normal, much of this moisture is from remnant Beryl. At this point in time there is more large scale lift, this should promote more widespread rainfall Thursday into Friday. WPC does highlight our region in a marginal risk for days 4 and 5 for excessive rainfall which is something to monitor as we head late into the week. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06z TAF Update: Through 12z Sunday: High confidence. IFR to LIFR from stratus and fog. These conditions should remain steady thru 12z for most, though we should start to see improvement around after 10z Sunday for the western airports. Light/calm winds north and west of I-95, otherwise southerly winds 5-10 kt. Today: High confidence overall, though moderate on timing sub-VFR improvement. IFR-LIFR to slowly improve to VFR for most thru 15z, with fog retreating into the waters. IFR-LIFR is expected all day for the South Coast, Cape and Islands. A chance for isolated/widely scattered TS after 18z to sundown near I-95 with best chance at PVD, but could slip as far north as ORH and BOS. Sub-VFR stratus then starts to return northward slightly very late in the period. Light W/WNW winds north and west of I-95, with seabreezes at BOS as conditions trend VFR. SSW winds 5-10 kt for PVD, Cape and Islands. Tonight and Monday: Moderate confidence. IFR-LIFR fog and stratus from the daytime hrs over the south coast, Cape and Islands returns northward tonight; best chance for PVD and the Cape/ACK, though it is possible it could slip northward into the BOS-ORH-BDL areas. Where it does develop, improvement should take place Monday morning, soonest north and west and later/afternoon towards the southeast coast. Light winds tonight and Monday, with seabreezes at BOS and PVD. KBOS TAF...High confidence in TAF. IFR-MVFR stratus and fog should improve to VFR by ~12-15z. VFR thereafter with seabreezes likely to develop. Low (< 15%) chance at SHRA/TS after 18z til sundown but best chance to the south. Stratus is possible again after 04z Mon, but better chance southeast. KBDL TAF...High confidence in TAF. IFR to improve to VFR by 10-12z Sunday. Stratus could return after 02z Mon but better chance southeast. Outlook /Monday Night through Thursday/... Monday Night: Mainly VFR, with local MVFR possible. Patchy BR. Tuesday: VFR. Chance SHRA, chance TSRA. Tuesday Night: Mainly VFR, with local MVFR possible. Chance SHRA, slight chance TSRA. Wednesday through Wednesday Night: VFR. Chance SHRA, chance TSRA. Thursday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, chance TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Today through Monday: Still have a couple 5 footers near the southern waters, so will maintain the SCA in effect for the southern outer waters thru early this morning. Otherwise, S winds around 15-20 kt expected today, and around 10-15 kt tonight and Monday. Fog will be persistent over the waters today through Monday, with lowest visbys more likely tonight. Could be a few showers at times too but thunderstorms are not expected. Outlook /Monday Night through Thursday/... Monday Night: Winds less than 25 kt. Patchy fog. Local visibility 1 to 3 nm. Tuesday: Winds less than 25 kt. Tuesday Night: Winds less than 25 kt. Slight chance of rain showers, isolated thunderstorms. Wednesday: Winds less than 25 kt. Slight chance of rain showers, slight chance of thunderstorms. Wednesday Night: Winds less than 25 kt. Chance of rain showers. Thursday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, isolated thunderstorms. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 AM EDT this morning for ANZ254. Small Craft Advisory until 11 AM EDT this morning for ANZ255- 256. && $$ SYNOPSIS...Loconto/Dooley NEAR TERM...Loconto SHORT TERM...Loconto LONG TERM...Dooley AVIATION...Loconto/Dooley MARINE...Loconto/Dooley