National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Boston, MA

-- Highlight Changed Discussion --

-- Discussion containing changed information from previous version are highlighted. --738FXUS61 KBOX 110453AFDBOXArea Forecast DiscussionNational Weather Service Boston/Norton MA1253 AM EDT Tue Jun 11 2024.SYNOPSIS...The weather theme through Tuesday will be mild days and cool nights,along with an isolated/spot shower during the afternoon. A warmingand drying trend Wednesday and Thursday will lead to increasing heatand humidity on Friday. An approaching cold front will bring anincreasing risk for showers and thunderstorms Friday, followed bydrier and more seasonable temperatures next weekend.&&.NEAR TERM /UNTIL 6 AM THIS MORNING/...10 PM update...* Very pleasant/tranquil weather persist into the overnightGusty winds have quickly dropped off with sunset allowing forcalm conditions the rest of tonight. Temps are already fallingthrough the 60s and into the 50s given the dry airmass in placeand diminishing winds. This will also set the stage for anotherseasonably cool night, with lows in the 50s, few upper 40s highterrain of northwest MA. Given a dry airmass, partly cloudyconditions and diminishing winds, derived mins overnight fromthe cooler MOS guidance.&&.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...320 PM update...Tuesday...* A cool morning followed by a mild afternoon* Other than a spot shower, dry weather prevailsAlmost a rinse and repeat scenario for tomorrow. Prettysimilar conditions to today, except slightly more cyclonic flowand colder temps aloft. This will lead to steeper mid levellapse rates more diurnal clouds than today. Can`t rule out anisolated, brief, light shower, but otherwise a dry day.Not much change in low level thermal profiles, with 925 mb tempsaround +14C to +15C, which will yield highs in the mid to upper70s. Cooler along the coast as seabreezes develop in theafternoon.Tuesday night...Diurnal clouds dissipate with sunset given loss of daytimeheating. This will yield mostly clear/partly cloudy conditionsalong with light winds, setting the stage for another cool nightwith lows in the 50s.&&.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...320 PM update...Key Points:* Early summer warmth Thursday and Friday could affect those most sensitive to heat* Scattered thunderstorms, some possibly strong, late Friday.Overall no dramatic changes in the forecast from what was offered bythe midnight shift. Some of the details...Wednesday: a mid level trough and associated cold pool aloft willswing across the region during the day. Right now the timingsuggested by the models would have this feature offshore byafternoon. However the cold pool combined with daytime heatingshould generate a little bit of instability, albeit rather meagerwith CAPE values less than 100 J/kg. We should have rather weak windfields in place, so expect sea breeze development. This should beenough forcing to allow a few showers to develop, especially acrossthe eastern half of the region. Don`t think shower coverage will beall that high, so kept PoPs in the 20-30% range for the noon-5pmtimeframe.Thursday: Southwest winds will bring in a warmer airmass. With 925mbtemperatures in the 18-20C range, this will support highs solidly inthe mid 80s across much of the region (except Cape and Islands).Winds should be strong enough to keep any sea breeze from moving toofar inland. Dewpoints won`t be too high -- upper 50s to lower 60s,but this could still give those at risk from hotter temperaturesand/or without air conditioning a few problemsFriday: Still southwest flow across the area, with 925mbtemperatures up a few degrees to the 19-23C range. That wouldsupport high temperatures into the upper 80s, especially inland fromthe south coast which will have some cooling effect from the windoff the water. Dewpoints will also rise a few degrees, so it willdefinitely have the mid-summer feel. Of more note is an approachingcold front and supporting upper level trough. Still uncertainty inthe timing, but it looks like these features would approach theregion late in the afternoon through Friday evening. Models suggestmore robust surface instability than Wednesday (which makes sensegiven higher temperatures and dewpoints), with CAPE values over 500J/kg. Not extreme, but enough to take note. Bulk 0-6km shear is also40-50kts during the afternoon, suggesting organized convection whichwould support strong, if not a few, severe thunderstorms. Timing isof course a big key as to whether convection lines up best with peakinstability. Right now it looks like timing will be a little on thelate side. Stuck with the NBM 40-50% PoPs, primarily focused on the5pm to midnight timeframe.Saturday/Sunday: Ridging and NW flow aloft would point to dryconditions with near normal temperatures.Monday and early next week: Some suggestions that we should have areturn to warming conditions and could see several days oftemperatures into the 90s.&&.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Forecast Confidence Levels:Low - less than 30 percent.Moderate - 30 to 60 percent.High - greater than 60 percent.Tuesday: VFR. Localized sea breezes forming mid morning,otherwise light WNW winds. Low chance an isolated shower in theafternoon.Tuesday night: VFR. Light and variable winds. IFR fog possiblefor the Cape and Islands.Wednesday: VFR. Localized sea breezes form again, otherwiselight WSW winds. Low chance for an isolated afternoon showeragain.KBOS TAF...High confidence in TAF.VFR. Sea breeze should develop by 14-15z. Sea breeze kicks out21-22z.KBDL TAF...High confidence in TAF.VFR. Light WNW winds.Outlook /Wednesday Night through Saturday/...Wednesday: VFR. Slight chance SHRA.Wednesday Night through Thursday: VFR.Thursday Night: VFR. Breezy.Friday: VFR. Breezy. Chance SHRA, isolated TSRA.Friday Night: Mainly VFR, with local MVFR possible. Breezy.Chance SHRA, isolated TSRA.Saturday: VFR.
-- End Changed Discussion --&&.MARINE...
-- Changed Discussion --
Forecaster Confidence Levels:Low - less than 30 percent.Medium - 30 to 60 percent.High - greater than 60 percent.320 PM update...High confidence through at least Tuesday night.WSW winds 10-15 kt, gusting up to 20 kt at times, thendiminishing after sunset. Tranquil boating conditions tonightand Tue with light winds and seas. Winds shift to NW latertonight behind a weak front, then becoming SE-SW Tue afternoonas sea- breezes develop. Winds then become light and variableafter sunset Tue evening. Dry weather and good vsby through atleast Tue night.Outlook /Wednesday Night through Saturday/...Wednesday through Thursday: Winds less than 25 kt.Thursday Night: Winds less than 25 kt. Areas of seasapproaching 5 ft.Friday: Low risk for Small Craft Advisory winds with gusts upto 20 kt. Seas up to 5 ft. Slight chance of rain showers,isolated thunderstorms.Friday Night: Winds less than 25 kt. Areas of seas approaching5 ft. Chance of rain showers, isolated thunderstorms.Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.Slight chance of rain showers.
-- End Changed Discussion --&&.BOX WATCHES/WARNINGS/ADVISORIES...CT...None.MA...None.RI...None.MARINE...None.&&$$SYNOPSIS...Nocera/NashNEAR TERM...Nocera/KPSHORT TERM...NoceraLONG TERM...NashAVIATION...KPMARINE...Nocera/Nash