Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 252106 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 506 PM EDT WED MAY 25 2016 .SYNOPSIS... 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 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. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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510 PM Update ... Did a quick update to include isolated to widely scattered showers/sprinkles over Western MA in response to a short wave trough moving across Northern New England. Most of these showers will likely erode/diminish as airmass ahead of these showers is very dry with dew pts in the low 40s along with downslope west- northwest winds. Thus not expecting much if any shower activity east of the Worcester hills. Otherwise remainder of the forecast is on track. Earlier discussion below. ==================================================================== Temperatures have climbed in to the mid to upper 80s away from the immediate coastline this afternoon. The sea breeze along the immediate east coast of Massachusetts should push back out to sea in the next hour. This will allow temperatures to make a last ditch effort to get up to 80 at Logan Airport. Once the sea breeze moves off, the temperature jump should occur rather quickly. Tonight...A mid-level ridge starts to build over southern New England from the west tonight, along with high pressure at the surface. Westerly winds shift more to the northwest overnight and remain on the light side. This will keep temperatures from dropping too low. Low temperatures tonight will be in the low to mid 60s for most of the area, with mid to upper 60s in the urban centers.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Thursday...High pressure moves offshore slowly while the mid level ridge centers itself over southern New England. With a much weaker gradient over the region, sea breezes along both coasts are a slam dunk. Therefore, temperatures will be cooler at the coasts but still in the mid to upper 80s for the rest of the area under mostly sunny skies. Thursday night...Mid level ridge sinks south a bit but overall conditions remain the same as previous couple of days. Winds will go calm overnight allowing temperatures to drop back into the upper 50s to lower 60s for most places. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... 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 trough 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 become 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. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through 00Z...High confidence. VFR. Weak sea breeze should move offshore by 21Z. Tonight...High confidence. VFR. Thursday...High confidence. VFR. Sea breezes will develop early on both coasts. Thursday night...Moderate confidence. VFR conditions likely for much of the period. Brief MVFR conditions possible in SCT - SHRA/TSRA across W MA/N CT. KBOS TAF...High confidence in TAF. 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. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. High confidence. Quiet boating weather is expected through the short term. 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. && .BOX WATCHES/WARNINGS/ADVISORIES... 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. && $$ SYNOPSIS...Nocera/RLG NEAR TERM...Nocera/RLG SHORT TERM...RLG LONG TERM...Nocera AVIATION...Nocera/RLG MARINE...Nocera/RLG is the U.S. government's official web portal to all federal, state and local government web resources and services.