307 FXUS61 KBOX 192319 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 719 PM EDT Tue Jul 19 2022 .SYNOPSIS... Heat and humidity will persist through the week and into next weekend with the most oppressive conditions Wednesday and Thursday. A cold front may bring another shot of showers and thunderstorms on Thursday, otherwise mainly dry weather into next weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 7:30 PM Update: After the temperate, and dry, start to summer we have had, tonight is one of the first nights to have that "summer feeling" in the air. Temperatures remain quite mild at this hour, with many locations clocking in between 85 and 90F. While temperatures will drop overnight, they will be limited by oppressive dewpoints in the upper 60s and low 70s, which means lows will struggle to drop out of the low and mid 70s; the exception being far northwest MA where a few readings in the upper 60s may occur. The most significant change to the forecast with this update was to increase wind gusts through the first half of the evening. Current observations show that gusts continue to exceed 20kt at some locations; gusts are still expected to die back overnight as we decouple. Otherwise, some high clouds will continue to stream through southern New England overnight before clearing out by sunrise. Overall, the forecast remains on track. With this update, a high rip risk was issued for Martha's Vineyard and Nantucket from 8 AM to 8PM on Wednesday. While small craft conditions are expected to diminish, there is enough remnant swell that rips could develop on south facing beaches. 355 PM Update: Been a hot and breezy day today across most of SNE. Aside from the southern coastline, many sites are currently in the upper 80s to low 90s! Hasn't been as humid though with dewpoints in the low to mid 60s for most of the interior and coastal plain, though more oppressive values in the upper 60s to low 70s can be found near the South Coast, Cape and Islands. Radar and satellite imagery show dry weather across SNE with shallow Cu fields common; there have been some somewhat deeper Cu/isolated convection in central NH/VT along a very weak/subtle convergence boundary and a jetstreak seen on midlevel WV imagery moving through interior New England. While steering flow is toward the SE, do have to keep some watch on this activity (best chance along/north of Route 2) but anticipate mainly dry weather to prevail with the risk ending by sundown. Otherwise, for tonight expect a mild night with winds becoming light for most, though will still be around the 10-15 mph range Cape and Islands. High clouds may increase for the second half of the night with lows mid 60s to lower-mid 70s. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... 355 PM Update: Wednesday: Peak of the heat still looks to be primarily centered on Wednesday, as 925 mb temps reach to around 26-28C in the interior and coastal plain and 850 mb temps 19 to 21C. Unlike today, winds will be on the lighter side out of the south/southwest which will also translate to higher dewpoints in the mid to upper 60s (locally lower 70s especially Cape and Islands). Have highs in the upper 80s Cape and Islands, and the mid to upper 90s across the interior and coastal plain. Will point out that sea-breezes look to develop near the eastern and southern coastlines during the late morning; this could keep notably Boston and part of the eastern coast from reaching the 90 degree mark until winds turn back to an onshore/SW component. Heat Advisories remain valid with no changes in time or space with this package. Heat indices in the 95-100F range still appear valid with the higher values in the Springfield/Hartford I-91 corridor, Merrimack Valleys and the I-95 corridor. Latest guidance was a little slower with bringing in the mid-level height rises to suppress convective chances. Most of SNE looks hot, humid but dry tomorrow with no evident or apparent sources of lift. A few the convective-permitting solutions from the 12z runs, including the WRF windows and more notably the NSSL WRF, do generate isolated to widely scattered SHRA/TSRA near the North Shore, part of Metrowest and near Boston acting on weak convergence on the sea- breeze boundary. I'm not optimistic much of anything develops, but some loose consensus in the noted CAMs left me to include around a 20% PoP for the northern part of the I-95 corridor. Not expecting anything strong with this activity despite the very warm and humid conditions with CAPEs only around 1000-1500 J/kg. Wednesday Night: A warm and muggy night in store with southerly winds around 5 to 10 mph. Southerly flow will transport higher dewpoints northward, into the lower to mid 70s. Model soundings at New Bedford, Cape Cod and the Islands show conditions favorable for areas of fog development toward Thurs AM, which could become locally dense in spots. Have lows in the low to mid 70s for most except upper 60s in the higher terrain in northern Worcester County and the Berkshires. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Heat persists through the weekend. Dewpoints will vary between oppressive and comfortable. * Convection likely Thursday afternoon and evening, though models remain varied regarding the exact timing and coverage of storms. * Slightly cooler conditions develop by early next week, but temperatures will remain above average. Details... Thursday... The above normal temperatures that have been impacting southern New England will continue into Thursday, though guidance remains varied on how high temperatures will climb before afternoon convection develops. Cooler temperature aloft in combination with increased cloud coverage ahead of the approaching shortwave and cold front may limit daytime heating. Some guidance hints that temperatures may struggle to hit 90 degrees in many locations, including the city of Boston, with 925mb temperatures only climbing to between 24 and 26C. Other guidance, namely the GFS with it's known heat bias, suggests much warmer temperatures aloft (between 26 and 28C). In general, highs are expected to be in the 80s along the coast in in the higher terrain, and the low 90s across metro west and the CT River Valley. Places like Lawrence, Lowell, Bedford, and Norwood will likely see the warmest readings of the day. Instability will likely be affected by how temperatures trend on Thursday, which may affect the potency of convection associated with a frontal passage late Thursday afternoon and evening. At present, there are many components that support convection, with forecast MU CAPE values between 1500 and 2000 J/kg. The NAM is forecasting anomolously high instability, but the aforementioned values should be ample to fuel convection. Mid level lapse rates are looking increasingly supportive of convection as well, climbing to between 6 and 7 C/km. With forecast dewpoints in the upper 60s and low 70s, and PWATS at about 140% of normal, there will be abundant moisture. K indicies climb into the upper 30s as well. The primary threat for severe weather on Thursday looks to be damaging winds, with modeled DCAPE values approaching the benchmark of 1000J/kg. Small hail is also possible, and an isolated tornado cannot be ruled out with bulk effective shear values exceeding 40 kt in portions of our CWA. SPC is also on board with the threat for severe weather on Thursday, placing much of our CWA in the slight risk category. Timing of the storms on Thursday will be one of the trickier things to forecast as guidance remains split on how early convection will get going. Model soundings indicate that there will be a capping inversion in place, that may not erode until early afternoon. Models indicate that convection may begin to fire in western portions of our CWA as early as 17Z (the WRF-FV3) and as late as 21Z (the GFS). Outside of the severe weather threat on Thursday, a low level jet will develop across eastern MA and RI, with 925mb winds forecast to be between 30 and 35 kt. These winds should mix down once the capping inversion erodes, and may prompt a small craft advisory for our eastern coastal waters. Friday through Monday... Persistent zonal, progressive flow will keep temperatures quite toasty through the weekend, though we may see some relief from the humidity starting Friday behind the departing cold front early Friday morning. While it doesnt seem significant, a drop in dewpoints in the low 70s to the low 60s by Friday afternoon will certainly be noticeable. Dry weather extends from Friday morning through much of the day Saturday as an isolated chance for a thunderstorm looks to stay to our northwest. There are signals from both the GFS and ECMWF that showers will develop late in the day Sunday into early Monday morning. Dewpoints build back towards 70 on Sunday as shower chances increase on Sunday. Guidance remains varied on the coverage and amount of precipitation expected on Sunday, but a signal is present in both the GFS and ECMWF and bears keeping an eye on. Some relief from the oppressive temperatures may be felt by early next week, but at present, it appears that temperatures will remain above normal. To note, the 10 day period between now and late July is climatologically the warmest of the year. && .AVIATION /23Z TUESDAY THROUGH SUNDAY/... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 00Z Update... Tonight: High confidence. VFR. W winds around 8-15 kt, strongest eastern coast where gusts in the 20-28 kt range. Wednesday: High confidence. Mainly VFR, though an isolated shower or t-storm could develop around the eastern MA sea breeze near or around BOS/BED 19-00z. Confidence too low to include in the TAF. WSW winds 6-9 kt, with local sea-breezes around 15-16z for BOS. Wednesday Night: High confidence. Generally VFR, though increasing moisture and lighter S/SW winds could support IFR- VLIFR fog for the Cape airports and ACK after 06z. KBOS...High confidence in TAF. KBDL...High confidence in TAF. Outlook /Thursday through Sunday/... Thursday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, isolated TSRA, patchy FG. Thursday Night: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA, isolated TSRA. Friday through Friday Night: VFR. Saturday through Saturday Night: VFR. Breezy. Sunday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Overall high confidence. SCAs continue on most of the southern waters due to higher seas and gusts in the 25-kt range through tonight. A Rip Current Statement remains in effect until 8 PM Tuesday for the Islands; as the rip current risk is progged at moderate to high levels on Wednesday as well, an updated Rip Current Statement will likely be needed for Wednesday. Winds around 20-25 kt tonight from the W/WSW, diminishing below SCA levels late in the overnight. Seas around 4 to 6 ft initially diminish to 2-4 ft Wednesday into Wednesday evening. Dry weather prevails on all waters through Wednesday early evening, then the risk for areas of fog develops on the southern waters overnight Wednesday night into early Thursday AM. Locally dense fog is possible. Outlook /Thursday through Sunday/... Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Patchy fog. Local visibility 1 nm or less. Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Slight chance of rain showers, isolated thunderstorms. Friday: Winds less than 25 kt. Local rough seas. Friday Night through Saturday: Winds less than 25 kt. Areas of seas approaching 5 ft. Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Sunday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory from 11 AM to 8 PM EDT Wednesday for CTZ002>004. MA...Heat Advisory from 11 AM to 8 PM EDT Wednesday for MAZ003-005- 006-010>021-026. Air Quality Alert from 11 AM to 11 PM EDT Wednesday for MAZ007- 020-022>024. High Rip Current Risk from Wednesday morning through Wednesday evening for MAZ023-024. RI...Heat Advisory from 11 AM to 8 PM EDT Wednesday for RIZ001>006. MARINE...Small Craft Advisory until 2 AM EDT Wednesday for ANZ232>234. Small Craft Advisory until 4 AM EDT Wednesday for ANZ235-237. Small Craft Advisory until 8 AM EDT Wednesday for ANZ254>256. && $$ SYNOPSIS...Loconto/KS NEAR TERM...Loconto/KS SHORT TERM...Loconto LONG TERM...KS AVIATION...Loconto/KS MARINE...Loconto/KS