Area Forecast Discussion
Issued by NWS Boston, MA

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050 FXUS61 KBOX 272256 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 656 PM EDT SAT AUG 27 2016 .SYNOPSIS... High pressure centered over Northern New England brings dry weather through Sunday. A cold front moves south across Northern New England Sunday night and may bring a chance for a shower or thunderstorm in northern Massachusetts. Weak high pressure brings dry and less humid conditions late Monday and Tuesday. The risk for thunderstorms along with warmer and more humid weather returns Wed as yet another cold front moves across the area. Canadian high pressure brings a period of dry and fall-like weather late next week into the weekend with mild days followed by cool nights. && .NEAR TERM /THROUGH SUNDAY/... 7 PM update ... High pres centered over Quebec this evening will provide tranquil weather to the region with light winds and mainly clear skies. With dew pts in the upper 50s and lower 60s temps will cool fairly quickly with sunset. Previous forecast on track so no major changes with this forecast update. Earlier discussion below. Through evening... High pressure centered over Quebec is bringing fair weather to the Northeast USA. Expect sunny skies through the evening. A sea breeze is in place along the coastline and will linger through evening. Dew points should remain in the mostly comfortable upper 50s/low 60s. Temperatures will remain in the mid 80s to around 90 inland, while the sea breeze keeps coastal areas in the upper 70s to mid 80s. Tonight... High pressure shifts east into the Maritimes, but remains in control of our New England weather. Expect fair skies and light wind. This will allow radiational cooling, with min temps near the dew point. This also means patchy fog in the usual places with vsbys below 1 mile in spots. && .SHORT TERM /SUNDAY NIGHT/... Ridge aloft Sunday shifts east by evening. High pressure at the surface will move out of the Maritimes and out to sea, but still bring dry weather for Sunday. Temps at the top of the mixed layer will be 16-17C so max temps should again be in the mid and upper 80s, cooler near the coast. Shortwave from the Plains moves east to Quebec by Sunday night. The supporting 110-knot upper jet eventually enters Northern New England Sunday night along with the favored right entrance region. Most of this remains to our north but may clip northern Massachusetts. We will show 25 pct pops north of MA route 2 and 15 pct much of the rest of the region. That 15 percent contour could possibly be moved north to the Mass Pike, but just enough upper venting into southern sections to show something, and the various QPF forecasts do extend 0.01 inch amounts south of the Pike late Sunday night. && .LONG TERM /MONDAY THROUGH SATURDAY/... Highlights... * Temps ... Very warm & humid Mon & Wed...more pleasant Tue * Precip ... Isolated T-storm Mon...higher risk Wed * Fall-like weather Thu-Sat with mild days and cool nights Overview and model preferences... Northern stream becomes more dominant this period and eventually erodes the subtropical ridge. Thus trend will be not as warm and less humid beginning Thu and likely lasting into next Sat. However this transition will be marked by a very warm and humid day Wed along with potential convection. Regarding guidance...both GEFS and EPS ensembles are in very good agreement on the large scale flow including timing of frontal passages Mon and Wed. However as expected at this time range deterministic guid differing on amplitude and timing of smaller features. For example 00z EC is slower with fropa Wed ngt into Thu along with a cooler post frontal airmass Fri with 850 temps dipping down to +4C! Typical biases (slower and more amplified) for the EC at this time range. So for this portion of the forecast there is above average forecast confidence on trends and avg confidence on details. Daily details ... Monday ... warm and humid with the risk of a few showers and T- storms. By afternoon the risk should shift south into CT/RI and south of the MA turnpike with fropa along with exiting deep layer moisture. Instability and shear is marginal along with forcing for ascent. These attributes should keep areal coverage of any storms isolated or widely scattered. Thus not a washout expected. Turning much less humid in post frontal airmass Mon night. Tuesday ... dry and comfortable humidity as ridging lingers across New England. Seasonably warm. Seabreezes keep the shoreline slightly cooler. Wednesday ... next northern stream short wave approaches along with attending cold front. Warmer and more humid ahead of the approaching cold front. Temps should surge well into the 80s away from south coast. In fact with wsw surface winds and ensembles suggesting +17C at 850mb and +22C at 925 mb...highs of 85-90 are possible. Heavy rainers possible as PWATs surge to about +1 SD along with surface dew pts 65 to 70. Modest instability and marginal shear will yield a low risk for a few strong storms possible. Thursday thru Saturday ... a touch of fall weather this period courtsey of 1025 mb Canadian high building across the Great Lakes into New England. Ensembles suggest 850 temps dropping to about +8C (about -1 SD) for a number of days. Likely see highs in the 70s and lows in the 40s and 50s! Thus the theme will be for mild days followed by cool nights. Very pleasant with dry weather and low humidity. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday Night/...High Confidence. 7 PM update ... No major changes from the 18z TAFs...VFR/dry weather and light winds. Earlier discussion below. ================================================================ Tonight... VFR. Light and variable wind. Patchy fog after midnight in the usually prone locations, mainly in the CT River Valley, with IFR/LIFR cigs/vsbys through sunrise. Sunday... VFR with light winds increasing out of the south. Some increase in high thin clouds during the afternoon. Sunday night... VFR. Increasing mid and high clouds. Areas of 4000 foot cloud bases north of the Mass Pike late at night with widely scattered MVFR in a shower or thunderstorm. Patchy fog with local IFR vsbys after midnight. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Monday through Thursday/... Monday ... Moderate to high confidence. Mainly VFR but isolated SHRA/TSRA yielding brief MVFR which shifts into CT/RI and southeast MA during the afternoon. Tuesday ... Moderate to high confidence for VFR and dry weather. Light winds with local seabreezes likely. Wednesday ... Moderate confidence. Mainly VFR but Local MVFR possible in scattered SHRA/TSRA. Thursday ... Moderate to high confidence. VFR and dry weather likely. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday Night/...High confidence. Winds and seas expected to remain relatively light through Sunday night. Sea breezes this evening will diminish, then return late Sunday morning and continue through the afternoon. Seas trend slowly higher Sunday and Sunday night in response to southeast swell from distant Tropical Storm Gaston. Widely scattered shower or thunderstorm possible late Sunday night. Best chance will be along the Massachusetts North Shore. Outlook /Monday through Thursday/... Monday ... Cold frontal passage in the afternoon/evening. A few storms possible with the front. Increasing south to southeast swells across the ocean waters from TS Gaston. Tuesday ... High pres overhead resulting in fine boating weather. Only issue will be south to southeast swells across the ocean waters from TS Gaston. Wed ... Another cold front passage in the afternoon/evening along with risk for T-storms. Thu ... Quiet boating weather should return as high pres builds into the Great Lakes and eventually the northeast. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/Nocera NEAR TERM...WTB/Nocera SHORT TERM...WTB LONG TERM...Nocera AVIATION...WTB/Nocera MARINE...WTB/Nocera is the U.S. government's official web portal to all federal, state and local government web resources and services.