218 FXUS61 KBOX 250631 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 231 AM EDT Fri Jul 25 2025 .SYNOPSIS... Peak of heat expected Friday with elevated humidity resulting in impactful heat, potentially dangerous if precautions not taken. Highs expected in low-mid 90s, but will feel more like upper 90s to low 100s. Showers and thunderstorms possible later Friday with a cold front. Cooler and mainly dry Saturday with showers and thunderstorms returning for Sunday. Outlook for early next week shows summerlike warmth and humidity, with generally dry weather for the majority of the time. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Wonderful summer afternoon across southern New England under a bit of fair weather clouds. Temperatures are seasonable in the mid to upper 80s and increasing dew points in the mid 60s. Over all there are no weather concerns this afternoon or tonight. Overnight surface high will shift further off shore. Clear skies tonight with a steady southwest wind keep the boundary layer well-mixed and should limit the development of coastal fog/stratus, despite increasing low-level moisture. Temperatures dip into the low 70s and upper 60s overnight with dew points in the upper 60s. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM SATURDAY/... Key Messages: * Dangerous heat and humidity for communities away from coastal RI and southern coast of MA. * Isolated to scattered thunderstorms Friday afternoon which could be strong to severe - with damaging wind gusts as the primary threat. A secondary threat, locally heavy rainfall may lead to isolated flash flooding. Friday will be the warmest and most humid day of the stretch. 925mb temperatures reach the mid 20s Celsius and with a well-mixed BL will have maximum temperatures in the lower to middle 90s. It is less hot near the south coast (due to SW flow off the water) with a maximum temperature in the middle to upper 80s. Heat Advisory remains in effect for southern New England, excluding Cape Cod, islands, south coast of MA & RI, and the Berkshires. Dews increase to the low 70s but not out of the question we near 75F, this is tropical-like feel and leads to heat incites in the upper 90s to lower 100s. Storms are possible during the afternoon ahead of a 500mb trough and surface cold front. Timing has come into better agreement for storm development between 2pm and 8pm, the NSSL would be the only outlier with an earlier initialization around noon in far northwest MA. And storms clear the Cape and Islands by 10pm/midnight. There are good ingredients for a few strong to severe thunderstorms, HREF mean CAPE are ~1,800J/kg, steep low- level lapse rates of ~9C/km, and modest effective shear of 30 to 35 knots. We are lacking mid-level lapse rates, as we move past sunset and lose that daytime heating, storms will begin to fade. A few of these storms may pack a punch, SPC has upgraded parts of southern New England to a slight risk, so a level 2 out of 5. Thinking the main concerns are damaging straight line winds and locally heavy rainfall within any convective storm. A friendly reminder if you can hear thunder, move indoors, because you are close enough to be struck by lightning! As mentioned above, heavy rainfall rates may pose a risk for isolated flash flooding. PWATs are near the daily climatological records with forecast values near 2.3", couple this with deep warm cloud layer of 12,000 ft and potential for slow moving storms. HREF probability of the 6-hour precipitation exceeding the 10 year ARI across eastern CT and western RI at 15% to 25% - will need to be mindful of those areas prone to flash flooding, but do not feel this is a widespread flash flooding event. But would not be surprised if someone were to pick up a quick 1-3 inches under one of these heavier downpours. Did collaborate those concerns with WPC and have expanded the marginal risk into southern New England for Friday. Friday night the cold front moves off shore and high pressure moves down from Canada. Will lead to clearing skies and lowering humidity. Wind shifts from the SSW to WSW during the evening, but will become more NNW after midnight. Temperatures settle into the low and middle 60s across the Berkshires and northern Worcester Hills, elsewhere will have lows in the upper 60s to low 70s. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Key Messages: * Dry and cooler on Saturday. * Showers and thunderstorms around Sunday. * High temps mainly in the 80s next week with a few shower/storm chances but mostly dry. Saturday and Sunday... A drier post frontal airmass works its way into southern New England on NW flow as surface high pressure drifts overhead beneath mid level ridging. This will make for a nice, dry day for the first half of the weekend featuring plenty of sun, light winds, and seasonable temperatures. Inland locations will reach into the 80s while an easterly onshore flow keeps the immediate east coast closer to the upper 70s. Sunday is more active as a subtle shortwave slides overhead through the quasi-zonal flow and dewpoints increase with backing surface winds. Thus, can expect increasing clouds and rain/thunderstorm chances through the day on Sunday, though timing is uncertain; some locations (especially east) may see more rain late Sunday into the overnight hours. Next week... Beyond Sunday`s disturbance the region remains under generally NW steering flow with a series of weak shortwaves moving through and bringing periodic chances for unsettled weather. No strong signals at this point for a large/organized system, and majority of the week should be dry. As we get toward the latter half of the week guidance suggests a building surface high which would keep things quiet into the weekend. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06Z update... Through 12z Thursday: High Confidence. VFR. SSW to SW winds 8-12 kts. Low chance of patchy fog/low stratus to develop across the southern waters, impacting terminals across southern Rhode Island and the southern coast of Massachusetts. With lower confidence in this, opt`d to exclude from TAF issuance. Friday: Moderate in timing of storms, but high confidence in trends. VFR. SSW/SW winds at 8-14 kts with occasional gusts up to 22 kts in the afternoon. Isolated to scattered TSRA possible. Best timeframe between 18z through 02z as storms develop in northwest MA and move southeast. Due to low coverage of storms, kept the PROB30 for TSRA at most terminals per latest CAMS. Within storms can expect brief MVFR conditions, gusty winds, torrential rain, and frequent lightning. Friday Night: High Confidence. Any lingering storms exit the coastal waters/islands by 06z. Cold front drops from NW to SE early evening, shifting winds from SW to NW speeds at 8-12 kts. Ceilings are generally VFR with lingering MVFR possible for the outer Cape and Islands. There is potential for a period of FG/BR for the Cape and Islands after 00-02z after the cold front moves through. Saturday: High Confidence. VFR. Northeast winds 5-8 kts for the interior and 6-12 kts closer to the coast. KBOS terminal...High confidence trends, moderate confidence in timing for KBOS TAF. Exact timing of line of storms lower confidence. Storms are expected to be scattered in coverage making it more difficult to pin point exact timing. Kept as a PROB30 group. KBDL terminal...High confidence trends, moderate confidence in timing for KBDL TAF. Outlook /Saturday Night through Tuesday/... Saturday Night: VFR. Sunday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, chance TSRA. Sunday Night: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, slight chance TSRA. Monday through Monday Night: VFR. Tuesday: Breezy. Slight chance SHRA, slight chance TSRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Tonight...High Confidence. Winds S to SW 10-20 kts. Gusts to 25 kts. Up to 30 kts possible over the northern outer waters with sustained winds around 25 kts. Seas 3 to 5 ft possible in the northern waters, only to 3 ft everywhere else. A Small Craft Advisory is in effect over the outer northern waters from 20z Thursday through 12z Friday. Friday and Friday Night...High Confidence. SW winds 10-15 kts, closer to 20 kts for the southern waters. Gusts 20-25 kts. Borderline criteria for SCAs for southern waters, Cape Cod Bay, Nantucket Sound and Buzzards Bay. Storms develop late afternoon into early evening as a cold front slides from the northwest to southeast, then pushing south of the waters by early Saturday morning. This does shift the wind to the NNW. Outlook /Saturday Night through Tuesday/... Saturday Night: Winds less than 25 kt. Sunday: Winds less than 25 kt. Slight chance of rain showers. Sunday Night: Winds less than 25 kt. Chance of rain showers, chance of thunderstorms. Monday through Tuesday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory until 8 PM EDT this evening for CTZ002>004. MA...Heat Advisory until 8 PM EDT this evening for MAZ003>007- 010>019-026. RI...Heat Advisory until 8 PM EDT this evening for RIZ001>004. MARINE...Small Craft Advisory until 8 AM EDT this morning for ANZ250. && $$ SYNOPSIS...BW/Dooley NEAR TERM...Dooley SHORT TERM...Dooley LONG TERM...BW AVIATION...Mensch MARINE...BW/Dooley