Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 261429 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 1029 AM EDT TUE JUL 26 2016 .SYNOPSIS... High pressure will bring dry but continued hot conditions today and Wednesday. A cold front will slowly push into the region during Thursday, then looks like will linger through this weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 1030 AM Update... Biggest issue is in regards to winds. Monitoring closely for a number of reasons: elevated fire weather potential and the necessity for small craft advisories for winds. An enhancement in the winds aloft presently ongoing as energy and accompanying jet streak / mid-level vortex flows rearward of the departing trough. This as we warm up into the 90s, diurnal heating of which allows for deep layer mixing on the order of 5-7 kft. Winds diminishing during the later half of the day as high pressure begins to settle into the region. Thus a brief period of gusts up to 25 mph out of the W/NW with perhaps lesser flow along the coast. This subsequent of a thermal-low setup and allowance of a sea-breeze for the immediate shores. Feel a majority of the wind gusts will remain around 15 to 20 mph, but again will have to watch closely. Mostly clear conditions but still some remnant moisture lingering within the low levels that`ll mix out and yield diurnal cumulus, that of which is already beginning to pop up on the latest visible satellite trends. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Tonight... High pressure builds in with diminishing wind. Dew points 60 to 65 will keep min temps in the 60s, with low 70s along the coast. Wednesday... High pressure remains in control with sunshine. Upper flow shows a weak shortwave moving through, but less cloud-level moisture for sky cover. Light wind near the surface will allow for developing sea breezes along the coasts. Temps aloft around 18C should support sfc max temps in the interior in the low to mid 90s, cooler values near the coastline. Dew points linger around 60 or in the lower 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Highlights... * Cold front approaches the region during Thursday * Showers and isolated thunderstorms remain possible Friday into the weekend Overview and model preferences... 00Z model suite remains in pretty good agreement through Thursday, then continue to show wide model spread from Thursday night onward. This appears to be dependent upon development of short waves in the nearly zonal H5 flow across the northeast, which will start to back to SW as broad mid level troughing develops across the Great Lakes into the weekend. The big differences come into play as models handling the slow movement of the front out of northern New England differently, along with any low pressure waves that move along it. One thing that is in somewhat good agreement is that the front should push into the region around Friday, then will stall in the W-SW mid level flow through most if not all weekend. Used a blend of available guidance through Thursday, then went with mainly ensemble approach beyond that. Details... Wednesday night...Will remain dry and muggy conditions. Patchy late night/early morning fog develops mainly along the coast and some of the interior valleys, especially interior E Mass. Overnight lows in the lower-mid 60s well inland, ranging to around 70 along the coast and urban centers. Thursday...Models begin their solution variance during this timeframe, but in fair agreement. Will see another hot and humid day, especially along the south coast. Timing of slow moving front remains in question, but does appear scattered showers/isold thunderstorms may push into N central and W Mass into N central CT during the afternoon/evening hours ahead of the front. Have carried low chance POPs there, with isold showers possible further S and E. Kept isold convection going, can not rule out entirely with marginal instability in place. Decent H85-H5 lapse rates of 6-6.5C/km, with best shot during max heating of the day. Expect highs in the lower-mid 90s away from the coast, warmest across the CT valley, ranging to the upper 70s-mid 80s near the coast possibly touching 90 in Boston and on the north shore. Thursday night and Friday...Model solutions continue to widen during this timeframe with the movement, or lack thereof, of the front out of S VT/NH. Also questions on development of low pressure along this front, with the GFS being most robust. Have kept chance POPs going, as models do generally bring in scattered showers, and kept isold thunder as well. With more clouds around, will see high temps on Friday 5-10 degrees cooler than Thursday, mainly in the 80s. Saturday and Sunday...High uncertainty remains during this portion of the forecast, with a continued low confidence forecast. Both the ECMWF and Canadian GGEM models move low pressure off the mid Atlantic coast during Saturday, with precip working into the region, while the GFS remains the outlier. More questions on timing of short wave in the H5 flow on Sunday, so kept low chance POPs going there as well. Monday...Low confidence continues. Do have low chance POPs going inland into the afternoon, then have trended drier. Expect temperatures to run close to seasonal normals. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/...High confidence. 15z major changes. Today... VFR. W/NW winds with gusts 15-20 knots, especially late morning through afternoon. Sea-breeze potential for the immediate E shore of MA around 18z. Tonight... VFR. Low risk of MVFR-IFR cigs/vsbys with fog towards Wednesday morning. Wednesday... VFR. Fog burns off around sunrise. Light variable wind becoming onshore along the coastline. KBOS TAF...W/NW winds. Gusts up to 25 kts around midday diminishing into the afternoon hours. This may allow a sea-breeze to come immediately ashore, but feel it will just remain adjacent to the E. KBDL TAF...W/NW winds. Gusts up to 25 kts possible into this afternoon. VFR. Outlook /Wednesday Night through Saturday/... Wednesday night...High confidence. Mainly VFR. Patchy fog possible after 07Z-08Z through 12Z along the immediate south coast, Cape Cod and the islands. Thursday through Saturday...Moderate Confidence. Mainly VFR, except MVFR CIGS/VSBYS possible in scattered showers and thunderstorms. Potential for local MVFR-IFR in patchy fog and low CIGS each night. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/...High confidence. W/NW Gusts up to 25 kts forecast, initially over the E waters through midday shifting over the S waters by early afternoon, diminishing into the evening hours. Perhaps relatively infrequent, will hold off on the issuance of a small craft advisory for winds over the waters. Will monitor closely. High pressure building into the region though late. Feel the sea- breeze will come immediately ashore but hold there up against the W/NW flow. Quiet boating weather overnight into Wednesday. Outlook /Wednesday Night through Saturday/...High confidence. Wednesday-Thursday...Winds and seas below small craft criteria. Patchy late night/early morning fog with reduced visibilities. Isolated showers/thunderstorms possible late Thursday/Thursday night. Friday-Saturday...Winds shift to S-SE but remain below small craft levels. Swells will build to around 5 ft on the southern outer waters Friday night into Saturday, then should subside. Patchy fog and scattered showers/thunderstorms will reduce visibilities. && .FIRE WEATHER... Much drier conditions are expected today across Southern New England behind the departing cool front, especially as the majority of rain yesterday (Monday) missed our area. Minimum relative humidity is expected to range from 30 to 40 percent expect along the immediate shores. NW winds 10 to 15 mph with gusts up to 25 mph possible though thinking infrequent. Lighter winds Wednesday with high pressure. Sea-breezes along the shores. Minimum RH values of 30 to 40 percent are forecast across interior Southern New England, higher along the shores with oncoming sea-breezes. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...WTB/EVT NEAR TERM...WTB/Sipprell/EVT SHORT TERM...WTB LONG TERM...EVT AVIATION...WTB/Sipprell/EVT MARINE...WTB/Sipprell/EVT FIRE WEATHER...WFO BOX Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.