Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 232325 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 725 PM EDT THU JUN 23 2016 .SYNOPSIS... High pressure remains influential over New England through the weekend. Expect a warming trend which will continue into Monday with showers and thunderstorms possible Tuesday. More seasonable weather is expected late in the week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 7 PM Update... More widespread clearing across SRN New England this evening partially as shearing vort max shifts S of the region. This will tend toward clearing skies but noted temps running a bit warmer than previously forecast. Therefore, only changes were to bring in more widespread clear skies later tonight and raise mins just a shade. Still think it will be cool overall, with many places dropping into the lower 50s before rising again. Previous discussion... High pressure settling in as a frontal boundary pushes offshore. Beneath, cyclonic flow aloft through which mid-level vortex energy rotates. Perhaps convergence and lift along the front / sea-breeze coupled with mid-level forcing will yield a spot shower for areas S of the N CT border towards the S-coast, Cape and Islands? HRRR seems to suggest and just evaluating the synoptics can not rule out as we go towards evening. Will prevail with slight chance PoPs. Closely watching activity out of PA attendant with a mid level vortex out of the E Great Lakes. Could be just enough of a kicker up on the low level lift generated by the boundary. A bigger question is how quickly will dry air move in? Low 60 dewpoints lingering S and E beneath a stabilizing boundary layer beneath which moisture will pool. Scattered nuisance low clouds over Nantucket at around 300 feet are likely to expand along and ahead of the front, most likely as far N as the S-coastline of MA and RI. Should see improvement and clearing towards morning. Can not rule out the potential of fog, mainly and mostly a repeat of soupy conditions on Nantucket. Otherwise a mild evening as it was warmer earlier in the day. Light winds across the interior with low dewpoints. Not ruling out radiational cooling and locations could fall back into the 40s for lows. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Friday... High pressure in control. Light winds. Beneath cooler air aloft with H85 temperatures around +10C. But considering the high angle of the sun, should easily warm back up into the upper-70s to low-80s. Cooler along the coasts with expected sea-breezes. Dry and comfortable as dewpoints will range in the 40s to low-50s. Friday night... High pressure pushes E. Begin to see return E/SE flow albeit remaining light. Mostly clear, an opportunity for radiational cooling and will need to watch those areas with sandy soils in particular. Leaned cooler of the forecast guidance, mainly towards MOS. Of greater attention is interior Southeast MA and Marthas Vineyard which could fall into the 40s. Progged presently in the low-50s. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Highlights... * Warming into Monday * Some showers and thunderstorms Tuesday * More seasonable WX late week Overview and model preferences... Continuance of the nearly zonal flow across the northern CONUS on the periphery of the cutoff anticyclone across the southern tier suggests any particular energy/vortex to weaken some upstream. In fact the building ridge which will bring about this weekend`s heat is mostly a response to downstream trof development. Given we remain on the anticyclonic shear side of this zonal flow, the quiet trend looks to continue for the most part. The only issue is an opening wave which will traverse this flow and arrive by Tue, this is currently linked to the PACNW vortex and will gradually open/weaken as it approaches New England. Otherwise, warmer than normal temperatures, with generally modest dwpts will define the next week. Not enough difference in the deterministic guidance even by mid next week to stray too far from a blend for this forecast update. Details... Sat and Sun... The primary issue for the weekend will be the heat potential. H85 temps rising to between +12C and +14C should easily be mixed to, providing at least mid-upper 80s, however, with a modified airmass and some hint at downslope component to the isallobaric flow, expect a few places to see the low 90s each day before all is said and done. Gradient winds remain light but out of the SSW, cooling RI and SE MA. E coastal sea breezes possible as gradient aloft likely not strong enough to keep it fully offshore. Mon... Chance for a very warm day as return flow develops with high pres moving E. H85 temps reach near +18C by afternoon. May be some convective cloud debris from the W to contend with but otherwise, full mixing expected with temps away from the south coast potentially rising into the 90s with dwpts increasing to the low 60s. Low risk for leftover convective shra by evening, but the best theta-e ridging remains to the W per latest runs. Also to watch, dwpts will run very close to crossover with S coastal SSTs, so will need to watch for marine fog/stratus impacts. Tue and Tue evening... With wave opening and shifting the low more meridionally approaching cold front is expected to slow as it reaches New England. Timing of this feature will once again be key to impacts, as an afternoon FROPA definitely suggests higher convective risk than an early AM or late evening passage. At this time, modest cooling aloft suggests MU CAPE values potentially exceeding 1500j/kg with sfc based values closer to 1000j/kg. Not a true EML it appears as lapse rates will only reach about 6.0 or slightly higher. Shear not impressive either as the mid lvl flow remains relatively weak. Therefore, primary risk would be heavy rain if any storms form. More to come as we approach. Wed and Thu... Similar setup to this week. Cold front stalls offshore and how close it sits will ultimately determine whether any MCS or developing frontal wave could impact Srn New England. High pres to the N looks to keep it too far S at this time thanks to some phasing of the initial trof with a secondary Hudson Bay trof late week. This suggests temps closer to seasonal normals, but a continuation of the dry wx. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/...High Confidence. No major changes with 00Z TAF update... Tonight... VFR for all terminals but the S-coast, Cape and Islands. IFR to LIFR cigs mainly with potential for fog over ACK. Anticipating a near-repeat of conditions the previous night over ACK. Cigs 300 to 500 ft agl. Friday... VFR. Light winds. Sea-breezes developing along the coasts towards mid-morning. Friday night... Patchy MVFR-LIFR conditions with fog. Lower CT River Valley, interior non-urban locations, perhaps along the S-coast. Light winds. KBOS TAF...VFR. E winds back out of the N overnight before becoming E again through Friday. KBDL TAF...concern with respect to Friday night into Saturday morning with potential fog issues. Otherwise VFR and light winds. Outlook /Saturday through Tuesday/...High confidence. Sat and Sun... VFR. Light winds mainly E and SE. Sea breezes expected. Mon and Tue... Mainly VFR. Low risk for early AM fog with localized IFR conditions. Some showers and thundershowers, especially Tuesday. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/...High confidence. Tonight... Low clouds and fog issues, perhaps a spot shower. N/NE winds increasing as a weak frontal boundary pushes offshore and in response to more active weather emerging off the Mid-Atlantic. Gusts up to 20 kts possible. Friday... NE winds initially with gusts up to 20 kts diminishing while turning E/SE as high pressure pushes across New England into the Gulf of Maine. Waves begin to build of 4 feet on the outer waters but much of this looks to be the result of swell subsequent of storm activity emerging off the Mid-Atlantic. Friday Night... Light winds overall out of the E/NE with high pressure situated over the Gulf of Maine. Seas of 4 feet continue over the S waters mainly due to swell from continued storm activity off the Mid- Atlantic. Outlook /Saturday through Tuesday/... Sat and Sun...High confidence. High pres moves over the waters with winds and seas expected to remain below small craft thresholds. Mon and Tue...Moderate confidence. Winds and seas remain below small craft thresholds for the most part except a few gusts near 20 kt near shore each afternoon. Some fog possible across the waters during the AM hours. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Doody/Sipprell NEAR TERM...Doody/Sipprell SHORT TERM...Sipprell LONG TERM...Doody AVIATION...Doody/Sipprell MARINE...Doody/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.