893 FXUS61 KBOX 260555 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 155 AM EDT Sat Jul 26 2025 .SYNOPSIS... Showers and areas of severe thunderstorms continue this afternoon 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. Showers and thunderstorms return for Sunday. Outlook for early next week shows summerlike warmth and humidity, with generally dry weather interrupted by a few shots at scattered showers and thunderstorms, mainly Tuesday and late Wednesday into Thursday. Trending drier and cooler Friday into the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... 7 PM update... The bulk of the showers and thunderstorms have moved offshore, and the severe weather threat has ended for the evening. As such, the Severe Thunderstorm Watch was cancelled. Previous Discussion... ** Severe Thunderstorm Watch for scattered damaging wind gusts in effect for much of the forecast area through 9pm this evening. * Dangerous heat and humidity through early evening * Drier and calmer conditions Saturday as high pressure builds in overhead. THIS AFTERNOON: Convection has begun to blossom mainly south of the Mass Pike as a prefrontal trough pushes southeast. Storms have thus far taken on multicellular characteristics but will begin to consolidate into more of a linear mode as they push south and east. Current mesoanalysis shows that the storms will be moving into a somewhat robust environment for maintenance and even growth. Instability-wise, RAP mesoanalysis shows a band of MLCAPE values between 1500 and 2000 J/kg across much of central and eastern CT and MA. Lower values exist SE of I-84 where a seabreeze has made some decent headway. Mid level lapse rates are meager, but low level lapse rates have increased to between 8.5 and 9 C/km ahead of convection. The steep lapse rates and high temp dewpoint spreads will help storms produce damaging winds as updrafts collapse. Enhanced outflow from initial convection and 25-30kts of effective 0-6 km shear will help storms organize into more of a linear mode with isolated bowing segments and pockets of damaging winds becoming more likely as the complex moves to the southeast. Outside of damaging winds, there is plenty of moisture available for heavy rain and isolated of flash/poor drainage flooding with any storm activity. Precipitable water values have risen to between 1.9 and 2.1 inches ahead of the trough. Model soundings show sufficient warm cloud depths as well for efficient rain processes. This together will support thunderstorms capable of locally heavy rain fall rates, and thus an isolated flash flood risk. The 12z runs have backed off some from previous runs with regards to HREF probabilities for 6-hour precipitation exceeding 5 or 10 year ARIs. However, there is a 5-15% probability for 6 hr precip exceeding the 2 year ARI across northern RI and east/southeast MA. The HREF PMM 3- hr QPF highlights similar areas with higher probabilities for > 1". This provides context that a few storms may be capable of causing localized flash flood impacts to areas especially flood prone ones (low lying, poor drainage, urban). However, a widespread flash flood risk is not likely. Additionally, winds aloft should keep storms moving which will prevent a storm from sitting over an area dropping heavy rain. Finally, high heat and humidity values will continue through the remainder of the afternoon. A current look at dewpoints shows widespread high humidity with dewpoint values ranging from 70 to 75 degrees! Actual air temperatures in the 90s have resulted in heat index values in the 95-103 degree range, especially in the interior. The good news is that improvement will follow quickly behind storm activity as it pushes offshore early this evening. TONIGHT: Any lingering shower or thunderstorm activity will quickly wane with the loss of daytime heating. Otherwise, the surface cold front pushes through from northwest to southeast overnight resulting in slowly improving temperature and dewpoint values. High pressure builds in from the northwest as the night progresses. .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... Key Messages: * Drier and cooler Saturday Saturday and Saturday Night: A much drier airmass follows on Saturday behind the cold front. Temperatures will be considerably cooler as 850 temps fall to + 12- 15C. Low level easterly flow will keep the coolest conditions across eastern MA and the Islands while areas in the interior may still see temperatures rise into the middle and upper 80s. Seasonably cool lows and clear conditions for the first part of Saturday night before an approaching warm front brings an increasing chance for showers and elevated thunderstorms by daybreak Sunday. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Key Messages: Key Messages... * Showers and thunderstorms return on Sunday. Severe weather is not expected at this time. * Temps warm up into the 90s through mid week but cooler weather arrives late week into the weekend. * Mostly dry this week with a chance of showers and t-storms around Tuesday and late Wed/Thu. Sunday... Sunday unsettled weather returns to the region thanks to a weak mid level shortwave sliding through the quasi-zonal flow with a weak surface trough replacing Saturday`s high pressure. This brings with it increasing moisture in the form of cloudcover and humidity, adding fuel for showers and garden variety thunderstorms. Limited lift and marginal lapse rates/instability should preclude any severe weather. Arrival of shower activity may be as early as the overnight hours Saturday night into Sunday morning. Increased cloudcover as well as lingering cooler air in the low/mid levels keep highs in the upper 70s to low 80s. Next week... 500 mb heights will be on the rise to start next week keeping things dry and kicking off some warm advection which pushes 850 mb temps closer to 18-20 C resulting in highs in the upper 80s and 90s Mon - Wed. Then, a cooler mid level airmass pushes in from the north as 850 mb temps drop to 8-9C by Friday! This should bring high temperatures back down to the 70s to low 80s and lows back into the 50s. Mostly dry next week save for a few disturbances that move through; a weaker one on Tuesday and a potentially more robust one around mid week. Timing on these features, though is less certain; can expect scattered showers and potential for thunderstorms with each of these. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06Z Update: Through 12z: High Confidence. Ceilings are generally VFR. Still can`t rule out a brief period of BR for the Cape and Islands early this morning as there is still some residual moisture/clouds lingering. Dry air should clear any residual patchy fog by 12z. Saturday: High Confidence. VFR with upper level clouds arriving throughout the afternoon. Winds start NNE this morning then turning more easterly in the early-late afternoon. Speeds 5-8 kts for the interior and 6-12 kts closer to the coast. There may be a brief period of light VRB winds at the interior terminals (BDL, BAF, ORH) early afternoon. Saturday Night: High Confidence VFR. Light SE at 5-8 kts winds early evening become light SSW by midnight. Rain should begin to move in across southern New England from west to east after 08z. Mid-level ceilings push across region ahead of the showers. Sunday: Mainly mix of low end VFR to MVFR as rain moves across southern New England on Sunday. S/SSW winds 8-13 kts. KBOS terminal...High confidence. KBDL terminal...High confidence. Outlook /Sunday Night through Wednesday/... Sunday Night: VFR. Slight chance SHRA. Monday through Monday Night: VFR. Tuesday: VFR. Breezy. Slight chance SHRA, slight chance TSRA. Tuesday Night: VFR. Wednesday: 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. Through Saturday Night...High Confidence. SW winds 10-15 kts, closer to 20 kts for the southern waters with 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 and shifting wind to the NNW. Winds veer SSW Saturday evening. Outlook /Sunday Night through Wednesday/... Sunday Night: Winds less than 25 kt. Slight chance of rain showers. Monday through Wednesday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...BW/FT NEAR TERM...McMinn/FT SHORT TERM...McMinn/FT LONG TERM...BW AVIATION...Mensch MARINE...McMinn