Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 231432 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1032 AM EDT THU JUN 23 2016 .SYNOPSIS... Low pressure tracking south of New England may bring a few showers today, mainly along the south coast and islands. Large high pressure will build across the region Friday and Saturday, then shift east into early next week. This brings a spell of dry and warming weather through Monday. An approaching cold front may bring showers and thunderstorms Tuesday and Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1030 am update... Tracking the mesoscale convective complex to our S. Evaluating the mean wind along with corfidi vector flow in addition to the thermal and moist axes, majority of this activity is going to stay S. With additional energy over N New England appearing like a squeeze-play in an environment not overly condusive for shower / thunderstorm developing. Yet lowering heights and a weak frontal boundary pushing offshore, could net some low to mid level forcing with diurnal heating that may yield a spot shower to which higher confidence is towards the S and E perhaps enhanced by sea-breeze contributions. There is some contribution of differential vorticity advection which may just sqeeze out some forcing with low level lift. Not a lot of moisture to work with though per 12z soundings. So an overall quiet day of weather with temperatures warming into the upper 70s to low 80s with a greater probability of cloud cover as you go N to S across S New England. Light winds and again sea- breezes along the shores. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Tonight... As low pressure pushes offshore well S of the region, expect any lingering showers, and even the low chance for a brief thunderstorm over the coastal waters this evening, to push offshore as well. Clouds will exit from NW-SE tonight with drier air moving in. May see some brief patchy fog develop near Nantucket again off and on tonight as the drier air will take its time moving in there. Expect winds to become light N-NW tonight, stirring just enough to prevent radiational cooling. Lows will generally be in the 50s, coolest across the higher inland terrain of N central and NW Mass., but may hold around 60 along the immediate S coast and on the islands. Friday... Large high pressure will begin to build SE out of south central Canada and the Great Lakes region on the continued W-NW flow aloft. Will see abundant sunshine with good subsidence in place. Expect seasonable temperatures, ranging from the mid 70s along the immediate coast to the lower-mid 80s, mildest across the lower CT valley. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... Big Picture... Longwave scale shows a persistent trough in Eastern North America and ridge over the West. Shortwave scale shows a ridge building over New England Saturday and Sunday before diminishing late Monday. A shortwave originating over the Pacific Northwest moves east across Canada over the weekend and then digs over New England Tuesday and Wednesday. The building ridge and increasing contour heights suggest a warming trend over the weekend. Forecast contour heights are about 120 meters above normal by Sunday. As the shortwave approaches Tuesday- Wednesday the heights fall and values return to near normal. Model forecast mass fields are similar through Monday, then diverge a little early next week. Even with the divergence, the forecast scenarios are similar. This encourages confidence in the forecast through early next week. Details... Friday night through Monday...High confidence. Surface high pressure over the region Friday night and Saturday shifts east by Sunday and Monday. The surface high combined with building heights aloft will lead to fair weather and a warming trend through Monday. A light low level east flow Saturday trends to a south to southwest flow Sunday and Monday. The mixed layer is forecast to reach above 850 mb, and may approach 800 mb each day. This brings 850-equivalent temps of 13-16C Saturday and 16-18C Sunday and Monday...with surface max temps in the mid and upper 80s Saturday and upper 80s/lower 90s Sunday and Monday. These temps may be buffered by flow off the cooler ocean in RI and Eastern Mass, especially Saturday. Monday night through Wednesday...Moderate confidence. Upper shortwave approaches, driving a surface cold front toward New England. Models show some difference in timing with the ECMWF now faster than the other models in bringing pcpn into Western New England later Monday. The rest hold off until Monday night, timing that we favor. There are also timing differences in the cold front passage with the ECMWF sooner/GFS later. We will feature chance pops all areas Tuesday and Wednesday and await resolution of the timing differences. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/... Today...high confidence. VFR. BKN cigs low-end VFR likely along the S-coast. Slight chance of SHRA S and E along the coast. Sea-breezes already developing along the coast. Tonight...High confidence. VFR. Low chance for MVFR-IFR VSBYS in patchy fog INVOF KACK and the outer Cape around or after 03Z, that should improve by daybreak. Friday...High confidence. VFR. KBOS TAF...Sea breeze should be in by 15z. VFR overall with SCT to BKN cigs. KBDL TAF...VFR. Winds are light presently but should see an increase through the day out of the S and W. Outlook /Friday Night through Monday/... High confidence. Areas of IFR and LIFR in late night/early morning fog. Otherwise VFR. Sea Breezes expected Saturday. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday/...High confidence. 1030 am major changes to the forecast at this time. Today...Seas are slowly subsiding with leftover 5-foot swell just outside the outer waters. With conditions trending lighter, we will end the small craft advisory that was in effect overnight. Showers will pass south of the waters. An isolated shower might bring brief lower vsbys to the southern outer waters this afternoon. Tonight and Friday...Winds and seas will remain below small craft criteria. May see some leftover visibility restrictions in patchy fog and any lingering showers tonight across the southern waters mainly from E of Cape Cod to S of Nantucket and Martha`s Vineyard. Should improve toward daybreak Friday. Outlook /Friday Night through Monday/...Moderate confidence. Winds remain below 25 knots and seas below 5 feet through the period. The southern waters may experience a 4 foot swell Saturday and a 3 to 4 foot swell Sunday. Coastal sea breezes possible Saturday all coasts and Sunday-Monday south coast. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/EVT/Sipprell SHORT TERM...EVT LONG TERM...WTB AVIATION...WTB/EVT/Sipprell MARINE...WTB/EVT/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.