000 FXUS61 KBOX 081120 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 720 AM EDT Mon Aug 8 2022 .SYNOPSIS... Heat and humidity will continue to be the main weather story early this week. Heat Advisories continue through Tuesday. A cold front will bring a better chance of showers and thunderstorms Tuesday. A slow-moving front will favor several opportunities for showers and thunderstorms Tuesday night through Thursday. Cooler temperatures, but still quite humid until this front clears into the coastal waters Thursday night into Friday. Seasonable, with much lower humidity Friday into next weekend, with dry weather returning. && .NEAR TERM /THROUGH TONIGHT/... 710 AM Update: Updated PoP/Wx in a nowcast sense for the southern nearshore waters from Block Island to Buzzards Bay. Radar and satellite shows slowly-developing showers with recent KBOX radar scans and some in-cloud glaciation on GOES satellite day cloud phase RGB implying the potential for lightning in some of these cores. Seems to be developing in area of appoximately 1000 J/kg of most- unstable CAPE. MWS in effect for these until 800 AM from Block Island to Buzzards Bay/Vineyard Sound as they move ENE. Also updated PoP/Wx for the rest of the afternoon; still a bit of an unclear outlook for this afternoon as there isn't any apparent or obvious surface convergence zones to support SHRA/TSRA development. Mixed signals in guidance and weakly forced setup also renders a lower-confidence convective forecast. If we do see storms they may be of less coverage than yesterday given the lack of any forcing, at least until later in the day/tonight when there's an approaching pre- frontal trough that could spark some activity. Otherwise, stifling heat and humidity to continue again today with current temps already into the mid to upper 70s. Heat indices again to reach into the mid/upper 90s and low 100s. Previous discussion: Expecting today to essentially be a repeat of the past few days. More heat and oppressive humidity, with a risk for afternoon showers and thunderstorms. Still dealing with relatively weak winds for organizing stronger thunderstorms. However, with 1,000-2,000 J/kg most unstable CAPE values, cannot completely rule out the idea for isolated strong to severe thunderstorms. High temperatures in the lower to mid 90s for most, with the coolest spots being the highest terrain of north central and western MA, the south coast of New England, and the islands. && .SHORT TERM /TUESDAY/... Any lingering showers and thunderstorms should dissipate after sunset. Although with a stalled frontal boundary a little closer to our region, this could take a few more hours than previous evenings, especially across the western half of southern New England. This front will be even closer Tuesday, especially once a frontal wave passes by to the east and gets this front moving south. Expecting a greater chance for some much-needed rain Tuesday. Given the tropical humidity, local downpours will be possible. Have some concerns that some locations towards northern New England may not quite reach the Heat Advisory threshold due to increased clouds and a possible earlier start to precipitation. That said, do not have enough confidence in this timing to adjust the ongoing Heat Advisories at this time. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Highlights... * Quasi-stationary front Tue night thru Thurs will focus periods of cloudiness and a few opportunities for welcomed rains. Best chance at widespread rains Wed night into early Thu. Temps cooler than normal but still quite humid. * Cooler and much more comfortable humidity levels Fri into the weekend. * Need to track position of surface cold front offshore but odds favor dry weather for the weekend. Details: Tuesday Night through Thursday: Quasi-stationary, slowly-southward-sagging frontal boundary in vicinity of SNE will combine with roughly front-parallel 700-500 mb flow and continued influx of tropical moisture to focus several opportunities for welcomed rains through showers and embedded t- storms. Though it's likely it won't be raining for the whole stretch, continued differences in frontal position and more specifically its southward egress through SNE supported PoP of at least lower Chance level for most of this period. Overall severe weather risk appears low to nil given abundant cloud cover, some onshore wind component and cooler surface temps. It looks like the period which harbors the best chance at welcomed rains is later Wed/Wed night into the early Thurs AM period, as subtle vort maxima induces weak surface low development on the frontal boundary and bringing with it a slug of beneficial rain, especially near/south of the Mass Pike into southeast New England. Seems to be reasonably good consensus in this outcome, in spite of how dry we've been, and also supported by EPS, GEFS and GEPS 24-hour QPF probs of at least 0.5 inches that are as much as 70% in the EPS. Lower probs of 24-hr QPF in the 1" range in this same corridor. In a convective pattern and given the coarser horizontal res of these global models can't take QPF at face value but nonetheless favorable probs for welcomed rains exist. Given the above, and synoptic pattern recognition looking similar to that of the Maddox frontal rain regime, opted to increase PoP into the higher Likely to Categorical range for Wed night into early Thurs, with PoP then diminishing a bit into Thurs aftn. Elevated PWAT values could support local downpours. Anticipate seasonable to cooler than normal high temps in this period, with lows around seasonable levels as well. Highs mainly mid/upper 70s to lower 80s, lows in the 60s to near 70. However it still will be quite muggy until the front sags southward into the coastal waters. Friday into the Weekend: Amplification of the western CONUS mid-level ridge is expected to dig a longwave trough southward from east-central Canada into the Ohio Valley/northern Appalachians vicinity. This should bring a much more refreshing air mass to SNE with lower humidity levels and temperatures around seasonable levels. PoP/rain chances continue to carry some level of uncertainty, but did note a rather remarkable flip-flop back towards drier weather for this period in both global ensemble means and the 00z deterministic guidance. Though it really didn't have much 12z ensemble membership support, the 12z ECMWF/GFS counterparts showed a closing-off mid-level trough with developing low pressure on the front near Bermuda then pivoting NNW toward coastal New England Fri- Sat with a decent slug of rain. The 00z suite of guidance however came in with a weaker and more progressive trough, which shifts the front well offshore into the western Atlc and keeps SNE dry with NWly flow. Something to monitor, but as NBM is too slow in reducing PoP given what's transpired in the 00z guidance, lowered PoP toward borderline slight chance/sub- mentionable levels in case today's 12z guidance comes back in wetter. Key in that evolution is the strength of the trough and if it closes off. Keeping outcomes open but given lack of ensemble support for a wetter outcome, thinking odds favor drier weather for this weekend. && .AVIATION /11Z MONDAY THROUGH FRIDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 12z TAF Update: Today: Moderate Confidence. Mainly VFR. Brief periods of MVFR in any afternoon showers or thunderstorms. SW winds 5-10 kt with gusts up to 20 kt. Tonight...High Confidence. VFR. SW winds 5-15 kts gusting to 25 kts for southeast MA. Tuesday...High Confidence. VFR. Areas MVFR in showers and scattered thunderstorms. SW winds 5-10 kts gusting to 20 kts for southeast MA. KBOS...Moderate confidence in TAF due to uncertainty as to whether any TSRA makes it to the terminal this afternoon. KBDL...Moderate confidence in TAF due to uncertainty as to whether any TSRA makes it to the terminal this afternoon. Outlook /Tuesday Night through Friday/... Tuesday Night: MVFR/IFR conditions possible. Breezy. Chance SHRA, slight chance TSRA. Wednesday: Mainly MVFR, with areas IFR possible. Chance SHRA, isolated TSRA. Wednesday Night: Mainly MVFR, with areas IFR possible. SHRA likely, chance TSRA. Thursday: Mainly MVFR, with local IFR possible. Chance SHRA, slight chance TSRA. Thursday Night: Mainly VFR, with areas MVFR possible. Chance SHRA, isolated TSRA. Friday: Mainly VFR, with areas MVFR possible. Chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Tuesday...High Confidence. SW winds 10-20 kt with gusts up to 25 kt. Winds and seas briefly diminish early this morning, before picking right back up later today into tonight. Winds diminish more from N to S Tuesday, as a cold front slowly approaches from the N. Outlook /Tuesday Night through Friday/... Tuesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, isolated thunderstorms. Wednesday: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms. Wednesday Night: Winds less than 25 kt. Rain showers, chance of thunderstorms. Thursday: Winds less than 25 kt. Chance of rain showers, slight chance of thunderstorms. Thursday Night: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms. Friday: Winds less than 25 kt. Chance of rain showers. && .CLIMATE... Record Maximum Temperatures August 8th: BOS 96F  ORH 94F  PVD 95F  BDL 98F  && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory until 8 PM EDT Tuesday for CTZ002>004. MA...Heat Advisory until 8 PM EDT Tuesday for MAZ002>023-026. RI...Heat Advisory until 8 PM EDT Tuesday for RIZ001>007. MARINE...Small Craft Advisory until 11 AM EDT Tuesday for ANZ231>235- 237. Small Craft Advisory from 2 PM this afternoon to 7 AM EDT Tuesday for ANZ236. Small Craft Advisory from 2 PM this afternoon to 11 AM EDT Tuesday for ANZ250. Small Craft Advisory until 8 PM EDT Tuesday for ANZ254>256. && $$ SYNOPSIS...Belk/Loconto NEAR TERM...Belk/Loconto SHORT TERM...Belk LONG TERM...Loconto AVIATION...Belk/Loconto MARINE...Belk/Loconto CLIMATE...