


Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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712 FXUS61 KBOX 151144 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 744 AM EDT Tue Jul 15 2025 .SYNOPSIS... Heat and humidity will build once again this week, peaking on Wednesday, but possibly lasting into Thursday or Friday as high pressure remains offshore. A cold front should bring showers and thunderstorms Thursday and Friday before relief from the heat arrives this weekend. && .NEAR TERM /THROUGH TONIGHT/... Key Messages: * Heat and humidity begin to build today. * Heat Advisory remains posted today through Thu. Upper ridge builds off East Coast over next several days which will pump increasing heat and humidity into region starting today. Prior to that, a band of light rain showers (more like sprinkles) was working through SNE early this morning. This activity is remains of yesterday`s convection to our west and was located ahead of weakening cold front that will essentially wash out over region today. Once this activity heads out to sea, ridging and daytime heating will help erode low cloud cover in place, though with persistent SW flow that will be tougher to happen near Cape Cod and Islands. Not seeing a lot of signals for showers/storms to develop this afternoon despite decent surface-based instability up to 2500 J/kg. Aside from terrain or perhaps south coastal sea breeze, there isn`t a good lifting mechanism available to generate convection, so the thought it we could see a lone shower/storm try to develop, but not much more than that especially given rising heights aloft and axis of higher K-indices being displaced offshore. CAMs seem to follow this thinking, even more robust EMC RRFS. If anything does manage to develop, main threat would be localized flooding rain given weak winds aloft and plentiful moisture, but even that seems to be a stretch. We should see another night of low clouds and patchy fog tonight, especially near South Coast with persistent SW flow. Certainly looks to be a warm and muggy night, especially within urban centers. && .SHORT TERM /WEDNESDAY/... Key Messages: * Peak of heat and humidity Wed. Upper ridge crests over SNE Wed with 590+ heights over region. Looks to be peak of heat and humidity with heat index (what it feels like) reaching 100F in many areas outside of higher elevations and locations near South Coast. Despite heat and humidity, we do not expect any showers or storms given strong mid level cap shown on forecast soundings which will suppress convective development. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Key Messages: * Heat and humidity persists into Thu or Fri with increasing chances of showers/storms. * Relief arrives this weekend. We remain in hot/humid airmass through end of the week, awaiting approach of mid level short wave and fairly strong cold front which will eventually bring relief from the heat and humidity this weekend. Seeing some timing differences among models with respect to how quickly both of thee features come through. Slower solutions would keep the heat and humidity going into Fri, although more in way of cloud cover could keep us just shy of Heat Advisory criteria. Faster approach means Thu would be focus for showers/storms and most of the ML guidance supports this idea with main risk of severe storms on that day (wind damage). For what it`s worth, 00z GFS is even a little faster than that and brings upper trough/front through Thu AM followed by drying in afternoon. For now, forecast will show chances of showers/storms in Thu/Fri timeframe and we will be able to nail down timing better in later forecasts. Front may eventually stall just south of New England later in weekend and possibly return north again early next week, setting stage for more showers/storms, but there`s more uncertainty in how things play out. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 12z TAFs: Moderate confidence due to timing of low ceilings. Improvement to VFR continuing this morning across the mainland terminals, aside from the Cape where ceilings are still IFR. Expected to continue improving this morning, but Cape Cod and Island terminals may not reach VFR until 17-20z. IFR to LIFR returns there around sunset this evening. VFR Wed. S/SW winds 10kt or less through Wed, although sea breezes could develop along E MA coast later this morning. KBOS Terminal...Moderate confidence in TAF due to timing of seabreeze. KBDL Terminal...High confidence. Outlook /Wednesday Night through Saturday/... Wednesday Night: VFR. Chance SHRA, slight chance TSRA. Thursday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, chance TSRA. Thursday Night: VFR. Breezy. Slight chance SHRA. Friday: VFR. Slight chance SHRA, slight chance TSRA. Friday Night: VFR. Slight chance SHRA. Saturday: VFR. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. High confidence through end of the week. Winds and seas stay below SCA through at least Wed as light SW flow persists with high pressure building offshore. Approaching cold front sometime Thu/Fri will bring tightening gradient which could bring 25kt winds and/or 5 ft seas to at least waters E and S of Cape Cod. Main concern will be areas of fog, especially at night and into morning, due to persistent SW winds through end of week. Outlook /Wednesday Night through Saturday/... Wednesday Night: Winds less than 25 kt. Slight chance of rain showers, slight chance of thunderstorms. Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers, slight chance of thunderstorms. Thursday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers, slight chance of thunderstorms. Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers, slight chance of thunderstorms. Saturday: Winds less than 25 kt. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for CTZ002>004. MA...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for MAZ003>007-010>021-026. RI...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for RIZ001>007. MARINE...None. && $$ SYNOPSIS...JWD NEAR TERM...JWD SHORT TERM...JWD LONG TERM...JWD AVIATION...Hrencecin/JWD MARINE...JWD