FXUS61 KBOX 260823 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 423 AM EDT Sun May 26 2019 .SYNOPSIS... A taste of summertime heat today with a low risk for an isolated late afternoon thunderstorm south of the Pike. A cold front moves south of the coast tonight followed by high pressure building in through Monday, then shifting off the coast early Tuesday. A few weak lows will move along a wavering front across the region late Tuesday into Thursday, bringing the threat for showers. Milder temperatures move in during Thursday ahead of an approaching cold front, with the threat for more showers and isolated thunderstorms. The front exits during Friday, with dry and seasonable conditions to start next weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Scattered showers are pushing off the coast early this morning, but the threat for a few showers and an isolated t-storm will continue across SE coastal New Eng through daybreak along the axis of the low level jet. Otherwise, increasing sunshine develops this morning with a very warm day for SNE. 850 mb temps 14-16C with developing W/NW flow support highs in the mid/upper 80s and would not be surprised to see a 90 degree reading. SW winds along the immediate coast will hold temps there in the 70s. Steep low level lapse rates with deep and well mixed boundary layer will result in gusty winds developing this afternoon, mainly away from the south coast as a low level inversion will persist there. Gusts to 30 mph likely, especially along and north of the Pike. Regarding convective potential this afternoon, SBCAPEs 500-1000 J/kg expected to develop which will be limited by BL mixing and drier air at the surface. Soundings also show very dry air developing above 750 mb which will limit t-storm potential. However, weak front and low level convergence south of the Pike may be enough to trigger an isold shower/t-storm during mid/late afternoon. The focus for any convection would be mainly across RI and SE MA and possibly eastern CT where slightly higher dewpoints may result in locally higher instability. Also noting a ribbon of higher KI in this area. Risk is low but non zero. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Tonight... Weak front moves south of the coast with dry airmass and light northerly flow. With clear skies, lows will drop back into the 50s. Monday... Weak high pres in control will result in plenty of sunshine. Cooler airmass but still warm away from the coast. High should reach well into 70s, near 80 CT valley, but upper 60s along the immediate coast, especially eastern MA where sea breezes develop. A cold front will be dropping south from northern New Eng during the afternoon and a few showers are possible along the boundary but this should remain to the north. The front drops south across SNE Mon evening. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Highlights... * Mainly dry conditions Monday night * Wavering front lingers Tuesday through Wednesday night with areas of showers and patchy nighttime fog * Cold front approaches Thu/Thu night bringing mild temperatures with showers and isolated thunderstorms * Rain exits Friday, then mainly dry, seasonable conditions early next weekend Overview... The progressive, active weather pattern across the northeast looks to continue through most of not during the entire long term period. Subtropical ridging remains across the southern U.S., with general long wave ridging remains across the western third of the country. Noting a continued nearly zonal mid level steering wind flow across the northeast, bringing a series of short waves from the central Mississippi valley across the Great Lakes to the region. So, will see periods of showers with mainly near to somewhat below temperatures through around Wednesday night. The wavering front channeling these lows may lift far enough north for a brief break, before a cold front moves E out of the Ohio valley/southern Great Lakes during Thursday. This may bring milder temperatures and more instability, so may see isolated embedded thunderstorms late Thu/Thu night prior to frontal passage. Medium range models continue signal generally drier, seasonal conditions for the start of June. Details... Monday night... Should see dry but cool conditions Monday evening as high pressure moves off the S coast. With the fast flow aloft, clouds will increase and a few showers may push into central and western areas after midnight as a warm front approaches. Tuesday through Thursday... A mainly zonal steering flow from north central Plains eastward to the northeast will keep mid level shortwaves and associated surface lows moving across the region. GEFS ensembles signaling possible PWAT plume moving across, with 1-2 SD above normal precip, possibly up to 3 SD above normal by late Thursday. Each system will bring a chance for showers, though there may be a better chance from around midday Tuesday into Wednesday morning. Current forecast suggests some locally heavy rainfall may move in with this system, especially across the CT valley and central areas. QPF amounts may range from 0.5 inches to 1 inch of precip there. May see a brief break around Wednesday night, then another shot moves in by around midday Thursday. Temps may warm up during Thursday as a warm front lifts N. Highs may reach the lower-mid 80s. This will help increase the instability factor ahead of the approaching cold front, with K indices in the lower 30s, SLIs around zero to -1 and TQ values in the upper teens. Have mentioned isolated thunder during this portion of the forecast. Friday and Saturday... H5 short wave and surface cold front crosses the region Friday, with leftover showers pushing offshore by around midday. Some models try to have some spotty precip lingering across central and eastern areas during the day, but should be mainly dry and cooler as winds shift to W-NW. Dry, nearly zonal mid level flow sets up across most of the northern tier by early Saturday. Ridging looks to set up across the northeast. So, at this point, looks like generally dry and seasonal conditions for the start of meteorological summer on Saturday. && .AVIATION /09Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday/...High confidence. Through 12z... VFR cigs with areas of MVFR developing. Showers and sct t-storms exiting eastern MA coast 06-07z, otherwise just a few showers to move through, becoming focused near the Cape/Islands 10-12z. A few SW gusts to 20-25 kt. Today... Leftover MVFR/IFR cigs Cape/Islands becoming VFR 14-15z but lower cigs may linger at ACK until 17-18z. Otherwise VFR. Low risk for an isold SHRA/TSRA late afternoon over CT/RI and SE MA. West wind gusts to 25-30 kt developing in the afternoon, mainly along and north of the Pike. Tonight...VFR. Light winds. Monday...VFR. Sea breezes developing late morning into the afternoon. KBOS Terminal...High confidence. KBDL Terminal...High confidence. Outlook /Monday night through Thursday/... Monday Night: Mainly VFR, with local MVFR possible. Tuesday: Mainly MVFR, with areas VFR possible. SHRA likely. Tuesday Night: Mainly MVFR, with local IFR possible. SHRA likely. Wednesday: Mainly VFR, with local IFR possible. Chance SHRA. Wednesday Night: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA. Thursday: Mainly VFR, with areas MVFR possible. Breezy. Chance SHRA, slight chance TSRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Monday/...High confidence. Today...Low level jet exits after daybreak with SW winds diminishing over SE waters. Winds below SCA for most of the waters, but west gusts 25-30 kt developing in the afternoon over Boston Harbor and eastern MA nearshore waters near the coast and Narragansett Bay where deeper mixing is present. SCA issued for these locations this afternoon. Tonight...NW winds quickly diminish in the evening becoming N overnight. Monday...Light northerly winds turning onshore over nearshore waters in the afternoon as sea breezes develop. Outlook /Monday night through Thursday/... Monday Night: Winds less than 25 kt. Tuesday: Winds less than 25 kt. Chance of rain showers. Tuesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Rain showers likely. Wednesday through Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers. Local visibility 1 to 3 nm. Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ231- 232. Small Craft Advisory from 1 PM this afternoon to 8 PM EDT this evening for ANZ230-236-251. Small Craft Advisory until 1 PM EDT this afternoon for ANZ250. Small Craft Advisory until 3 PM EDT this afternoon for ANZ254- 255. && $$ SYNOPSIS...KJC/EVT NEAR TERM...KJC SHORT TERM...KJC LONG TERM...EVT AVIATION...KJC/EVT MARINE...KJC/EVT