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Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
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938 FXUS61 KBOX 131917 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 317 PM EDT Tue Aug 13 2024 .SYNOPSIS... Dry and very pleasant weather continues into Wednesday. Another round of scattered showers, and perhaps a few thunderstorms, is expected Thursday. Dry weather likely returns Friday and may linger into Saturday, especially across RI and eastern MA. Then a frontal system may bring scattered showers and thunderstorms Sunday through Tuesday. Probably not a washout, with periods of dry weather too during this time. Meanwhile, Ernesto will track well southeast of New England, but it will bring rough surf and strong rip currents to south facing ocean beaches of RI and MA this weekend. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Model soundings show a shallow layer of moisture around 5,000 ft which is creating diurnal cumulus over much of the region...otherwise full sun under the influence of high pressure to our west. With the loss of heating after sunset these clouds will clear and overnight we`ll see a good setup for radiational cooling. Light winds and clear skies allow temps to dip into the 50s away from the coasts. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Wednesday will feature more of the same weather from today as the high nudges further east over New England. It once again leads to mostly clear skies to start with light winds. Our closer proximity to the high also means less wind and sea breezes setting up along the coast keeping the immediate shore in the mid 70s (with mid 80s inland). Diurnal cumulus will be more numerous on Wednesday thanks to moisture below 800 mb. The one wrinkle is a small disturbance rotating around the exiting mid level trough, but lack of moisture above 800 mb, weak forcing, and surface high pressure will help keep the majority of locations dry. Even so, can`t rule out a smattering of isolated showers and even a thunderstorm in the afternoon. Diurnal clouds and any showers will dissipate after sundown but more cloudcover will move in from the north thanks to a weak shortwave overhead. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights * Scattered showers and thunderstorms Thursday followed by dry and seasonably warm conditions Friday * Trending unsettled weather this weekend, with Sunday appearing wetter than Sat, although periods of dry weather too * Ernesto likely tracks well southeast of New England, but will bring rough surf and rip currents this weekend to south facing ocean beaches of MA/RI Thursday and Friday... Closed low forms over the maritimes Wed night, then retrogrades toward New England Thu. Increasing cyclonic flow and cold pool aloft combined with mid level moisture, will yield scattered showers and isolated thunderstorms Thursday. Similar type day to what we observed yesterday/Monday. -14C temps at 500 mb will yield steep mid and low level lapse rates, supporting a low probability of an isolated gusty thunderstorm with small hail. 12z CSU machine learning probs reinforce this idea. Drier and sunnier Friday, as short wave ridging advects across the region, along with warming temps aloft. Seasonably warm and somewhat humid both days, with highs upper 70s to lower 80s, mid 80s possible Fri and dew pts in the 60s both days. Typical August weather. Light and variable winds each day, along with afternoon seabreezes keeping the coastline a few degs cooler. The Weekend... Next short wave trough exits the Great Lakes and approaches New England. Although, there may be sufficient short wave ridging over SNE between Ernesto tracking southeast of New England and approaching Great Lakes trough, for mainly dry weather to prevail across RI and eastern MA. Higher probs of showers and thunderstorms would exist each day across CT into western-central MA. Although, too far out in time to say with much certainty, but something to keep in mind as we approach the weekend. As PWATs increase to above normal this weekend, any convection will have the potential for brief heavy rain. Not expecting a washout as there will be periods of dry weather too. Seasonably warm both days with highs in the upper 70s and lower 80s. As southwest flow strengthens Sunday, humidity increases with dew pts rising from the 60s Sat into the low 70s Sunday. As for Ernesto, above average forecast confidence in storm track, with all guidance tracking this system well southeast of New England. Thus, no impacts expected. However, large/rough surf and dangerous rip currents from Ernesto arrive this weekend, especially at south facing ocean beaches. See the latest tropical forecast and updates from The National Hurricane Center at nhc.noaa.gov. Early Next Week... Great Lakes trough finally advects across the region, with scattered showers and thunderstorms possible both days, especially Mon with some improvement possible Tue, pending exact trough departure time. For what it`s worth at this time range, 00z CSU machine learning probs do offer low chance of strong thunderstorm winds both days. Warm and humid with highs in the upper 70s and lower 80s. It will feel quite warm, with dew pts in the low 70s. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 18Z TAF Update This afternoon...High Confidence. VFR. NW winds 5 to 10 knots. Tonight...High Confidence. VFR. Low probability of localized fog developing toward daybreak in the typically lowest lying locations. Calm/Light NW winds. Wednesday...High Confidence. VFR. Light north winds, with seabreezes likely to develop along the immediate coasts. Wednesday night...High Confidence. VFR. Winds light and variable. KBOS TAF...High Confidence. Low chance for a sea-breeze after 19Z this afternoon through 23z. KBDL TAF...High Confidence. Outlook /Thursday through Sunday/... Thursday: VFR. Chance SHRA, isolated TSRA. Thursday Night through Friday Night: VFR. Saturday: VFR. Breezy. Slight chance SHRA. Saturday Night: Mainly VFR, with areas MVFR possible. Chance SHRA, isolated TSRA. Sunday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, isolated TSRA. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Wednesday night...High Confidence. A ridge of high pressure to our west will result in pleasant boating weather winds/seas below Small Craft Advisory thresholds through Wednesday night. Visibility should be quite good as well. Outlook /Thursday through Sunday/... Thursday through Friday: Winds less than 25 kt. Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Saturday: Winds less than 25 kt. Areas of seas approaching 5 ft. Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. Sunday: Winds less than 25 kt. Local rough seas. Chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...BW/Nocera NEAR TERM...BW SHORT TERM...BW LONG TERM...Nocera AVIATION...BW/Nocera MARINE...BW/Nocera