000 FXUS61 KBOX 042345 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 745 PM EDT Thu Aug 4 2022 .SYNOPSIS... Heat and humidity will be the main weather story right into early next week. The hot stretch continues Friday with even higher humidity. The greatest potential for showers and thunderstorms will be Friday into Saturday, with localized heavy rainfall possible at times. It may be Tuesday or later before this heat and oppressive humidity finally breaks in a significant way. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 740 PM UPDATE... Forecast remains largely on track. A new daily max temperature record of 98F was set at Boston while 96F was enough to tie for Hartford. A few strong to severe thunderstorms have mostly missed our CWA to the north and west. Besides the negligible shear to sustain updrafts, SPC mesoanalysis shows a steep K index gradient northwest of our area. So while places like Bennington received reports of localized damaging wind gusts and the Albany area reported up to 3 inches of rain, there was simply too much dry air aloft to deal with to even organize updrafts. The only exception was across far northwest Franklin county where part of a decaying thunderstorm spilled over the Berkshires but nothing severe. Otherwise, a quiet night of weather with muggy and uncomfortable conditions. The marine layer or fog bank that has been draped over Nantucket the whole day would move slightly north overnight, possibly resulting in reduced visibility across the south coast into Cape Cod. PREVIOUS DISCUSSION... Well, it's hot out. Boston is sitting two degrees above the record for the day, at 98F. Importantly, the "feels like" temperature (heat index) has risen to 100 and above for many locations across southern New England. As the heat increases instability has risen with it; SPC mesoanalysis shows surface based CAPE values increasing to 1,500- 2,000 J/kg. Shear is extremely weak to nil, however, so while scattered showers and thunderstorms are possible in northwest MA this afternoon/evening they should be of the garden variety (non- severe). The showers and thunderstorms come to an end in the hours just after sunset with loss of daytime heating leaving a quiet night with a mix of mid/high clouds to the northwest and low stratus and fog over southeast MA thanks to that increased low level moisture. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... We end the week with more of the same: heat and humidity. The humidity, though, will be markedly higher tomorrow as dewpoints surge into the mid 70s on SW flow. Thus, while actual temperatures should be a few degrees cooler, the heat index will once again reach over 100 F. The bullseye of highest heat index Friday will be over southeast MA rather than northeast MA thanks to the higher dewpoints. All that to say, another day of dangerous heat is in store, so take the proper precautions ahead of time to limit your time outside. Heat Advisories continue for all of southern New England. Showers and thunderstorms will be more likely on Friday thanks to some better forcing from an approaching cool front and weak mid level shortwave. As it moves in it will take advantage of strong instability (CAPE 1000-1500 J/kg) and deep moisture (PWATs ~2 inches) initiate a round of showers and thunderstorms generally between noon and 8 PM. Like today, the thinking is that these will be sub-severe owing to the non-existent bulk shear for organizing and sustaining convection. Given the instability and steep low level lapse rates, though, can't rule out some localized damaging winds. More likely would be the an isolated threat of some urban and poor drainage flooding given weak steering flow and deep moisture. Showers and storms come to an end after sunset but with the stalled front draped across northern areas this may be enough to kick off some scattered showers overnight. Lows will be very warm, in the 70s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Highlights... * Oppressive heat and humidity continues through early next week. There is the chance for isolated showers and thunderstorms daily. * A slow-moving cold front could bring much needed rainfall to portions of the region by later next week, but timing and areal coverage remain uncertain at this time. Details... Saturday into Sunday... Bermuda High continues to hold strong this weekend and support a deep southwest flow pattern into southern New England. As a result, above normal temperatures and humid conditions will persist. Whether individual locations meet the criteria for a heatwave, which is three consecutive days of 90 deg, the combination of air temperature and dew points in the mid 60s to mid 70s will yield heat indices in the mid 90s to low 100s. The elevated dew points also means muggy and uncomfortable nights. Current heat headlines will likely be extended with future forecast packages for this weekend, and perhaps into Cape Cod and the Islands. Precipitation wise, weak upper level short wave will bring some cloudiness and a chance for isolated showers and thunderstorms. While there will be sufficient instability for convection, little to no deep-layer shear will suppress severe thunderstorm development. However, abundant deep layer moisture and weak boundary layer winds could support slower moving thunderstorms with localized, brief heavy downpours. Unfortunately, short of widespread soaking rainfall, there will barely put a dent in the deteriorating drought situation, where the eastern half of our CWA is now in D2 severe drought category according to the US Drought Monitor. Monday into Thursday... No notable air mass change as we enter the new work week so high heat and humidity continues with a trend towards somewhat more seasonable temps later in the work week. For reference, typical highs for the second week of August are in the low to mid 80s. For those tired of the heat and humidity, we may get a reprieve sometime in the mid to late week time frame. But there remains plenty of uncertainty with regards to the timing. CIPS analog indicates that there is a somewhat better chance for stronger thunderstorms in the Tuesday or Wednesday time frame, but that is contingent on the strength and progression of the cold front. Given the plenty of uncertainty, mainly stuck to blended guidance for this part of the forecast. While there may seem to be no end in sight to this heat, the good news is that we are now past the climatologically warmest time of the year and cooler days are not far away. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight...Moderate confidence. Generally VFR except for localized IFR to LIFR for Cape terminals due to fog development. Friday...Moderate confidence. Areas of LIFR to start the day. Sea breeze expected to kick in for BOS around 15-17z time frame. Generally VFR. Greater risk for showers and thunderstorms, especially across the western two-thirds of southern New England. Friday night...Moderate confidence. Mainly VFR. MVFR/IFR CIGS possible for some, mainly along the south coast, Cape, and islands. SHRA and TSRA come to an end after sundown. KBOS...High confidence in TAF. KBDL...High confidence in TAF. Outlook /Saturday through Tuesday/... Saturday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, isolated TSRA. Saturday Night: Mainly VFR, with local MVFR possible. Breezy. Sunday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, isolated TSRA. Sunday Night: Mainly VFR, with local MVFR possible. Breezy. Monday: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA. Monday Night: Mainly MVFR, with local IFR possible. Breezy. Chance SHRA. Tuesday: Mainly MVFR, with areas VFR possible. Breezy. Chance SHRA, isolated TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. High confidence. Winds and seas to remain relatively tranquil through Friday night. Areas of fog tonight into Friday morning for southeast MA including Cape Cod and the islands. Fog should dissipate during Friday morning. Outlook /Saturday through Tuesday/... Saturday: Winds less than 25 kt. Saturday Night through Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Monday Night through Tuesday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, isolated thunderstorms. && .CLIMATE... August 4th daily record maximum high temperatures... BOS - 96F  ORH - 95F  PVD - 98F  BDL - 96F  August 4th daily record maximum low temperatures... BOS - 76F  ORH - 72F  PVD - 74F  BDL - 74F  August 5th daily record maximum high temperatures... BOS - 100F  ORH - 96F  PVD - 100F  BDL - 101F  August 5th daily record maximum low temperatures... BOS - 76F  ORH - 73F  PVD - 77F  BDL - 76F  && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Air Quality Alert until 11 PM EDT this evening for CTZ002. Heat Advisory until 8 PM EDT Friday for CTZ002>004. MA...Air Quality Alert until 11 PM EDT this evening for MAZ005>007- 010>012-014. Heat Advisory until 8 PM EDT Friday for MAZ002>021-026. RI...Heat Advisory until 8 PM EDT Friday for RIZ001>007. MARINE...None. && $$ SYNOPSIS...BW/Chai NEAR TERM...BW/Chai SHORT TERM...BW LONG TERM...Chai AVIATION...BW/Chai MARINE...BW/Chai CLIMATE...