Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 141345 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 945 AM EDT Thu Sep 14 2017 .SYNOPSIS...
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The much weakened remnants from Irma will bring scattered showers and a few thunderstorms this afternoon into Friday, but the vast majority of the time will feature dry conditions. Generally dry and seasonable weather expected weekend. Hurricane Jose will likely bring high surf and dangerous rip currents this weekend into the middle of next week, but it is uncertain if it gets close enough for any other impacts.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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***Scattered showers and isolated thunderstorms develop from west to east this afternoon/early evening with the focus northwest of the Boston to Providence corridor*** 945 am update... An abundance of cloudiness covered the region at mid-late morning. We should see enough breaks in the clouds develop for some peeks of sunshine at times. This should allow afternoon highs to reach into the upper 70s to lower 80s in most locations. It will feel a bit humid with dewpoints in the 60s. Approaching shortwave coupled with 500 to 1000 J/KG of Cape should allow for scattered showers and isolated thunderstorms to develop during the afternoon and evening from west to east. Primary focus of the activity should be northwest of the Boston to Providence corridor through early evening. The threat for severe weather looks quite low given very marginal instability and weak wind fields. Brief heavy rain though is possible with any embedded thunderstorm given Pwats in excess of 1.5 inches.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Tonight and Friday...Mid level cutoff low will open up as it slowly shifts E during this timeframe. Will see best instability and moisture tonight associated with the cold pool pushing E. PWAT plume rotates N around the remnant low, with PWAT values increasing to 1.6 to 1.7 inches. May see some heavy downpours in any heavier convection tonight into early Friday. Expect lows tonight in the 60 to 65 degree range. The H5 trough will slowly shift offshore during Friday, but instability aloft holds on so will see more diurnal convection develop with scattered showers and isolated thunderstorms. With more clouds around, temps will be a bit cooler. Expect highs mainly in the 70s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Highlights... * Mainly dry/seasonable this weekend other than a spot shower Sat * Jose brings high surf/dangerous rip currents later this weekend into next week. Still uncertain if it gets close enough for any other impacts 14/00Z guidance suite has come into better agreement through Saturday, but still exhibit significant spread in track and timing beyond Saturday. Still have little confidence in a single deterministic outcome for Jose. Will continue to favor an ensemble approach for this portion of the forecast. Still thinking it will be a few more days before we can have much confidence in details about as track and timing of Jose. Just about all of the 14/00Z deterministic runs are outliers when compared to their corresponding ensemble means, although the ECMWF looks to be closest to its ensemble mean. As of this writing, the most likely outcome is for Jose to slowly drift north and weaken due to the colder sea surface temperatures, then shift NE well offshore of New England. However, this is not a guarantee. Can see a few scenarios where Jose could make a closer approach to southern New England. A closer approach would mean more wind and rain impacts. Will definitely see a prolonged period of elevated risk for dangerous rip currents along exposed south-facing beaches into early next week. Otherwise, this portion of the forecast looks mainly dry. Some risk for a few showers at times, greatest towards the period from Monday night through Tuesday night. Near normal temperatures this weekend. Below normal highs expected early next week. && .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/... Today...Moderate to high confidence. Mainly VFR outside of scattered showers and isolated t-storms this afternoon/early evening which develop from west to east. The exception will be the south coast, Cape and particularly Nantucket where low clouds and fog patches may continue to flirt with the area into the afternoon. Tonight and Friday...Moderate confidence. Mainly MVFR to VFR CIGS. May see local IFR CIGS/VSBYS in patchy fog late tonight into early Fri. Areas of MVFR conditions in scattered showers/isolated TSRA at times. May see brief heavy rainfall tonight. KBOS Terminal...Moderate confidence in TAF. Scattered shower/isolated t-storm threat probably focused northwest of the terminal later this afternoon and evening. KBDL Terminal...Moderate confidence in TAF. Scattered showers and perhaps isolated thunderstorms will be in the vicinity of the terminal this afternoon and evening. Outlook /Friday Night through Monday/... Friday night and Saturday...Moderate confidence. MVFR-IFR conditions possible Fri night/Sat morning in some low clouds and patchy fog. Improvement to VFR thresholds by Saturday afternoon. Sunday and Monday...Low confidence. VFR conditions probably dominate. Will still need to be wary of MVFR CIGS at times with onshore flow off the ocean. Also, high uncertainty early next week regarding the track, timing and strength of Jose.
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&& .MARINE...
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Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/...High confidence. Today through Friday...Expect SW winds less than 15 kt and seas 4 ft or less. Reduced visibilities at times in fog especially during the late night/early morning hours. Scattered showers late today into Friday. Low risk for thunderstorms. Outlook /Friday Night through Monday/...Moderate confidence in trends. Low confidence in details. Swells from distant Jose will continue to impact the southern coastal waters into early next week. The magnitude of this impact will depend on how closely Jose gets to the waters. Thinking the deterministic GFS is a strong outlier from its ensemble mean, undercut the wave height guidance slightly later this weekend into early next week. Rough seas across the southern outer coastal waters are likely. Some wind impacts are possible, too. Just do not have much confidence in those details yet.
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&& .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/EVT NEAR TERM...Frank SHORT TERM...EVT LONG TERM...Belk AVIATION...Frank/Belk/EVT MARINE...Frank/Belk/EVT

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