Area Forecast Discussion National Weather Service Boston/Norton MA 156 PM EDT Thu Jul 9 2026 .WHAT HAS CHANGED... No changes to the forecast for this update cycle. .KEY MESSAGES... - Warm with high humidity today and Friday. - Humid with a chance of showers and thunderstorms Friday afternoon and evening. - Dry and seasonably cool for the weekend into early next week. .DISCUSSION... KEY MESSAGE 1...Warm with high humidity today and Friday. A warming trend begins in earnest today as 925mb temperatures rise to near 20C with the full July sun angle. Highs in the upper 80s to near 90 are likely across most of southern New England by the afternoon. Expecting a very humid day with dewpoints increasing to near or just above 70 (at times) this afternoon. A weak cold front brings a chance for widely scattered showers and an isolated storm or two. Weak forcing from a subtle shortwave should prevent a more widespread threat for strong or severe storms. Best chance for showers and thunderstorms will be across northwest Massachusetts. Any storms that do form will have the potential to produce frequent lightning and heavy rain as PWAT values climb above 1.7 inches. KEY MESSAGE 2... Humid with a chance of showers and thunderstorms Friday afternoon and evening. Warm and humid conditions continue Friday although it will likely be few degrees cooler with 925mb temps running about 3-4C cooler than Thursday. Still, dew point temperatures near 70 will keep apparent temperatures in the upper 80s to low 90s. Attention turns to a cold cold front sagging southward from northern New England during the early afternoon in northern MA and reaching the southern CT-RI-MA coastline by early evening. The associated forcing will be greater than Thursday so there will be a greater chance for more widespread shower and thunderstorm activity on Friday. Latest guidance still shows significant differences in the magnitude of instability and thus the eventual convective evolution Friday afternoon. The 00z NAM's CAPE values, while somewhat lower than previous, are still around 1500-2500 J/kg due to its high-dewpoint bias. Meanwhile, the GFS's overmixing bias shows considerably lower values at around 500 J/kg or less. The answer is probably somewhere in the middle with the NBM which has 800-1300 J/kg by Friday afternoon. In any case, the primary risks with any thunderstorm looks to be lightning and slow-moving heavy downpours, which could lead to instances of street flooding in areas that see repeated thunderstorms. Latest guidance indicates 700-500 mb heights which become increasingly parallel to the southward- sagging frontal boundary, which adds to the risk for slower- moving storms and also casts some uncertainty when we clear out, with the Canadian guidance suggesting post-frontal light rains lingering into part of Saturday along the South Coast. KEY MESSAGE 3...Dry and seasonably cool for the weekend into early next week. Trending much drier behind Friday's cold front by Saturday with any lingering moisture pulling away from the region Saturday morning. The 500 mb pattern then transitions to one of cyclonic flow/troughing in the mean, which favors cooler temperatures (low to mid 80s) and lower humidity levels than experienced for late in the week. Weekend appears favorable for outdoor plans with nice summer weather. We'll be on the far western periphery of a pretty impressive upper level ridge which latest guidance still shows reaching to nearly 600 dm building over the northern/central Plains and upper Midwest. We still might need to keep an eye on possible storminess pivoting around the ridge but it looks as though the weekend into early next week ends up drier than not. .AVIATION /18Z THURSDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through Friday...Moderate Confidence. A cumulus field continues to grow across the higher terrain this afternoon. An isolated shower or thunderstorm is possible, mainly west of KBED/KPVD through this evening. VFR conditions are expected to prevail. Ceilings are expected to lower with areas of MVFR advancing northward across CT/RI/southern MA. Confidence is low to moderate if lower ceilings will reach KBED and KBOS after 9z Friday. Low ceilings/vsbys are expected to persist across the southern coast through Friday morning. Flight conditions are expected to improve to VFR by afternoon. Elsewhere, VFR expected Friday. Isolated to widely scattered showers and thunderstorms are possible, with a higher risk by the southern coast. KBOS Terminal...Moderate to high confidence. KBDL Terminal...Moderate to high confidence. Outlook /Friday Night through Tuesday/... Friday Night: Mainly VFR. Slight chance SHRA. Saturday through Tuesday: VFR. .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through Friday Morning...High confidence. Mostly tranquil conditions today as high pressure builds over the region. A weak front approaches the region later this afternoon into the evening with showers and thunderstorms possible over the southern waters. Another tranquil start to the day Friday with showers and thunderstorms developing by the afternoon. Outlook /Friday Night through Tuesday/... Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Saturday: Winds less than 25 kt. Areas of seas approaching 5 ft. Saturday Night through Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Sunday Night through Monday: Winds less than 25 kt. .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. DISCUSSION...FT AVIATION...Guest MARINE...FT