Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 241737 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 137 PM EDT Sat Jun 24 2017 .SYNOPSIS...
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A cold front over Eastern Massachusetts moves offshore this afternoon. This brings clearing skies and warm temperatures. Dry weather and lower humidity follow for tonight. Seasonably warm and less humid conditions Sunday will be followed by cooler weather and few diurnally driven showers and isolated thunderstorms Monday into Wednesday. A warming trend begins for the latter half of the week with a return to summer heat and humidity by Friday.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/... Active morning in the weather office as a trough leading a low pressure wave swept up across Southeast New England and brought showers/thunderstorms along with some heavy downpours. Southerly winds of 30-35 knots showed as inbound on the BOX radar, providing a strong inflow of moisture, and cross sections showed this wind lifting to 10-15K feet. The result was an area of heavy rain that moved across Southern RI and SE Mass. Reports showed rainfall rates of approximately an inch an hour with some reports of street flooding...mainly in the usual areas. This rain area was affecting Cape Cod/Plymouth/Vineyard areas at 1115 AM, and should move offshore between noon and 1 PM. Associated showers will also sweep Nantucket during the noon hour. The low pressure and its associated cold front are moving through the region, with showers along the front from Salem through Northeast Connecticut. These will move through the region early this afternoon. Drying/clearing trend follows this front. Mixed layer per 12z soundings should reach to at least 800 mb. Temps at this level support max sfc temps in the mid to upper 80s. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... Tonight... Overall becoming quiet. Some initial light shower activity across N/W MA and CT, up against the high terrain, as mid-level energy advects through the continued cyclonic flow promoting localized theta-E / moisture convergence. But soon after weak height rises overnight out ahead of a more stout mid-level feature through the longwave trough over the Great Lakes Region. Surface high pressure emerging, drying out and clearing out, W winds becoming light, there is the opportunity for radiational cooling. Indications of low to mid 50s in the coolest of guidance at typically prone locations. Dry air advection with dewpoints fall, not anticipating fog threats. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Highlights... * Seasonably warm/less humid Sun with a spot shower possible interior * Cooler with a few showers/isold t-storm possible Mon into Wed * Warming trend toward end of the week with return to summer heat/humidity by Fri Details... Sunday... Fairly robust mid level shortwave moves NE from Gt Lakes. Brunt of energy remains well to the north and west, but cooling aloft will result in diurnal cu developing and can`t rule out a few afternoon showers, mainly in the interior. Instability parameters are not favorable so no mention of thunder. 850 mb temps near 12C and deep mixing supports highs in the low to mid 80s but cooler south coast with SW flow. Dewpoints in the 50s will make it feel much more comfortable. Monday into Wednesday... Anomalous mid level trof moves eastward from the Gt Lakes Mon pushing into New Eng late Tue and may linger into early Wed. Temps continue to cool aloft Mon which may trigger a few showers or an isold t-storm in the interior, but best chance of showers/t-storms will likely be on Tue as the trof approaches and core of coldest air aloft moves overhead. Timing of when the trof exits is somewhat uncertain but GFS and ECMWF still have -21C at 500 mb 12z Wed before temps aloft warm in the afternoon. So expect isold showers and t-storms again on Wed with focus more across eastern half New Eng. Temps through Wed will average near or slightly below normal with highs mainly 75-80 and lows in the 50s. Thursday and Friday... Pattern change signaled as upper trof moves out with rising heights and zonal flow across New Eng. This will result in a warming trend with temps into the 80s Thu and possibly 90+ on Fri. Humidity levels should still be comfortable Thu as dry air remains in the lower levels, but higher dewpoints will be moving in by Fri. Mainly dry weather, but developing warm advection may bring a few showers Thu afternoon to northern areas, then chance of afternoon showers/t- storms Fri as atmosphere destabilizes. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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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 Tonight/...Moderate confidence. This afternoon... Lingering MVFR/IFR cigs and vsbys in fog over Cape Co and Islands moves offshore this afternoon. Clearing skies in Eastern Mass and mostly sunny skies in Central and Western parts of our area. Gusty northwest winds behind the cold front with speeds in the lower 20s. This will diminish this evening. Tonight... VFR. Mostly clear skies with diminishing wind, becoming calm in the interior. Sunday... VFR. Increasing cumulus clouds late morning and afternoon especially northwest of I-95. Scattered afternoon showers ORH- HFD-BAF and points north. Could be brief MVFR cigs/vsbys in any afternoon shower. Sunday night... VFR. West winds. KBOS Terminal...High confidence in TAF. Shifting winds, from the WNW this afternoon, becoming light tonight, then from the southwest Sunday afternoon. KBDL Terminal...High confidence in TAF. Outlook /Monday through Wednesday/... High confidence. Mainly VFR. A few diurnally driven showers and perhaps an isold t-storm each day.
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&& .MARINE... This afternoon and tonight... Showers and thunderstorms over the waters will trend northeast and move east of the waters during the early afternoon. Expect south winds to shift out of the west at that time. Winds will then diminish at that time. Waves of 5 to 7 feet will linger early afternoon on the outer waters and the Rhode Island waters, then subside towards Sunday morning. All other waters should remain below 5 feet. Outlook /Sunday through Wednesday/... Sunday...High confidence. Some lingering 5 ft seas possible over the southern waters, otherwise winds will remain below SCA. Monday through Wednesday...High confidence. Quiet boating weather with winds and seas below SCA. A few hours of nearshore lower 20 knot wind gusts are possible each afternoon. && .TIDES/COASTAL FLOODING... Astronomical tides are rather high through this weekend during the night time cycles. Boston has a 12.4 ft high tide around midnight tonight and 12.2 ft just after midnight Sunday night. While, offshore winds are forecast current conditions suggest a 0.4 surge which will result in minor splashover. Thus will go ahead an issue a coastal flood statement for tonight`s high tide. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...High Surf Advisory until 8 PM EDT this evening for MAZ020-023- 024. RI...High Surf Advisory until 8 PM EDT this evening for RIZ006>008. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ231>234. Small Craft Advisory until 11 AM EDT Sunday for ANZ235-237. Small Craft Advisory until 2 AM EDT Sunday for ANZ250. Small Craft Advisory until 8 PM EDT Sunday for ANZ254>256. && $$ SYNOPSIS...WTB/KJC NEAR TERM...WTB SHORT TERM...Sipprell LONG TERM...KJC AVIATION...WTB/KJC MARINE...KJC/Sipprell TIDES/COASTAL FLOODING... is the U.S. government's official web portal to all federal, state and local government web resources and services.