Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 251951 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 351 PM EDT WED MAY 25 2016 .SYNOPSIS...
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350 pm update ... High pressure off the Mid Atlantic coast will bring very warm weather to most of the region through Saturday along with increasing humidity this weekend. It will be cooler temperatures at times along the immediate coast. A backdoor cold front will bring cooler weather to Rhode Island and Eastern Massachusetts Sunday with warm weather continuing elsewhere. Warmer than normal temperatures overspread the remainder of the area by early next week. A few showers and thunderstorms are possible Thursday night into Friday, and again this weekend but the vast majority of the time will be dry.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... ***Summer temperatures push in today across the region*** 1030 AM Update...Most of the fog has cleared out across the area with the exception of one band of fog that is hugging the south coast of RI and moving eastward towards Buzzards Bay and the Cape. If it continues on this trajectory without burning off, portions of Cape Cod along the Cape Cod Canal as well as Martha`s Vineyard and the Elizabeth Islands will see a period of fog later this morning into early afternoon. Visibilities have been generally about a mile with this bank of fog on land, it may be more dense over the water. Made minor adjustments to the temperatures to ease them back as they have not jumped up as quickly as forecast. Otherwise, the previous forecast is on track. Weak ridging at the surface and aloft will cross the region by midday through the afternoon with NW winds aloft. Warm core H925 temps will push across the region, up to +19C to +22C by this afternoon. Once skies become mostly sunny, temps will rise quickly with excellent low and mid level mixing in place. Expect temps to top off in the mid-upper 80s with a few spots touching 90. However, dewpoints falling into the 40s will result in low humidity levels. High clouds will start to push in from the NW during the mid and late afternoon ahead of H5 short wave across far northern New England. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... Tonight... Most of the energy from a weak H5 shortwave trough will remain across northern New England. NW flow keeps dry conditions across the region tonight. The mid and upper level clouds will dissipate overnight as SW winds shift back to W-NW and diminish. It will remain mild, with temperatures only bottoming out from the mid 50s well inland to lower-mid 60s across the coastal plain. Thursday... A cold front will slowly push S across the region during the day. Clouds will push in from the W as the front moves in during the afternoon. Short range models vary in their solutions, with mainly dry conditions through the day offered by the ECMWF, but the GFS tends to bring some moisture with a weak H5 shortwave in the W-NW flow aloft. Have mentioned only slight chance PoPs moving into W MA/N Central CT during the mid and late afternoon hours. Have noted marginal instability with this system, plus another day of warm temperatures, so have mentioned widely scattered showers/isolated thunderstorms. It will be another warm day, with somewhat higher dewpoints making it feel a bit more humid. Highs will again be in the mid-upper 80s away from the immediate coast, with a few spots possibly hitting 90 again. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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350 pm update ... Highlights... * Temperatures warmer than normal much of the time * Other than isolated showers/thunderstorms many hours of dry weather this period Subtropical ridge builds northwestward from Western Atlantic into the Northeast late this week into the weekend and lingers into at least early next week. This will result in temperatures warmer than normal much of the time along with mainly dry weather. Both the 00z GEFS and 00z EPS offer 850 temp anomalies of +1 to +2 standard deviations above normal over Southern New England during this time. However there will be a brief cool down Sunday across Eastern MA and RI as a shallow cool airmass invades this area behind a backdoor cold front. Otherwise much of this forecast period will be warmer than normal (normal highs around 70, normal lows around 50). As for rain chances...a prefrontal will enter Western portions of MA and CT Friday. However rising heights and increasing anticyclonic mid level flow will likely suppress most convective development. Likewise on Sat with the ridge continuing to build and heights reaching +2 standard deviations above normal over the northeast. By late Sat and into Sunday the backdoor front provides surface convergence and shallow low level forcing first north of MA Sat and then across much of the region Sunday. However large amplitude ridge over the region along with mid level anticyclonic flow may suppress much of the convection once again. Thus model guidance is likely too wet especially the 12z GFS. Therefore have undercut guidance from chance to slight chance pops Fri/Sat and Sun. Greatest risk (albeit low) of seeing any showers/thunderstorms Fri/Sat & Sunday will likely be across Western portions of MA and CT. Thus a washout is not expected just isolated to widely scattered showers/thunderstorms well inland. Mon and Tue of next week becomes interesting as area of convection currently northeast of the bahamas advects northwestward around the subtropical ridge into the mid Atlantic region. Then it becomes a question if the upstream northern stream trough has sufficient amplitude to capture this area tropical moisture and advect it into Southern New England. 00z GEFS and 00z EPS both suggest bulk of tropical moisture remains offshore or just clips south coast of New England and bulk of convection from northern stream trough remains northwest across NY state and VT. Given the time range and uncertainty chance pops seems reasonable here.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today...High confidence. VFR conditions expected the rest of the day, except on the Cape and Islands where fog may reduce visibilities down to MVFR/IFR at times. Tonight...High confidence. VFR conditions. W-NW winds 10 kt or less. Thursday...High confidence. VFR. Light W-NW winds, except sea breezes possible late morning/afternoon along the coast. KBOS TAF...Moderate to high confidence. An ESE sea breeze has developed and is expected to continue into early afternoon. Southwesterly winds should overcome this by late afternoon. KBDL TAF...High confidence in TAF. Outlook /Friday through Monday/... 350 pm update ... Friday ... MVFR conditions likely with low risk of a few brief showers/t-storms mainly across the interior. Also, some patchy ground fog possible in the typically prone locations very early Fri AM. Moderate to high forecast confidence. Saturday ... Moderate to high confidence. Any early MVFR conditions should quickly lift to VFR by midday. Low risk of a few afternoon and evening showers/thunderstorms well inland. Sunday ... Moderate confidence. MVFR likely with low risk of IFR in spots. A few thunderstorms also possible Sun afternoon across the interior. Monday ... low confidence given time range and weather pattern. VFR likely but period of MVFR in low risk of scattered showers/ thunderstorms.
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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. Today...High confidence. W winds up to 10 kt will back to SW 10-15 kt this afternoon with gusts up to 20 kt on the southern outer waters. Seas 4 ft or less. Patchy fog mainly along the south coast will result in reduced visibilities at times. Tonight...High confidence. Light southwesterly winds become westerly, gusting up to 20 kt on the southern outer waters this evening. Seas 4 ft or less. Thursday...High confidence. Light W winds shifting to S in the afternoon. Seas remain below 5 ft. Outlook /Friday through Monday/...High Confidence. Winds and seas will generally remain below Small Craft Advisory thresholds through the period. The main concerns are a period of near-shore southwesterly wind gusts of 20 to 25 knots Saturday afternoon which will result in some choppy seas for mariners. May also see some brief easterly wind gusts between 20 and 25 knots on Sunday behind a backdoor cold front. Then winds become ssw Sunday into Tue as front lifts north as a warm front.
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&& .FIRE WEATHER... Today...Expect temperatures will rise quickly, soaring well into the 80s to near 90 across most locations except cooler along the immediate south coast. These temperatures will combine with dewpoints dropping into the 40s resulting in afternoon RH values down to between 20 and 30 percent. A few hours of westerly wind gusts up to 20 to perhaps briefly 25 mph are anticipated. Given Tuesday`s rainfall and marginal criteria, will fall short of needing fire weather headlines. Many locations are close to or already at full green-up. && .BOX WATCHES/WARNINGS/ADVISORIES...
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CT...Air Quality Alert from 11 AM to 11 PM EDT Thursday for CTZ002>004. MA...Air Quality Alert until 11 PM EDT this evening for MAZ020>024. Air Quality Alert from 11 AM to 11 PM EDT Thursday for MAZ002>005-008>014-017-018-020-021-023-026. RI...Air Quality Alert until 11 PM EDT this evening for RIZ003-004- 006>008. Air Quality Alert from 11 AM to 11 PM EDT Thursday for RIZ001>008. MARINE...None.
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&& $$ SYNOPSIS...Nocera NEAR TERM...Frank/RLG/EVT SHORT TERM...EVT LONG TERM...Nocera AVIATION...Nocera/EVT MARINE...Nocera/EVT FIRE WEATHER...staff

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