Area Forecast Discussion
Issued by NWS Boston, MA

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358 FXUS61 KBOX 311051 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 651 AM EDT TUE MAY 31 2016 .SYNOPSIS... A cold front will cross southern New England today bringing a drier airmass. High pressure then builds over New England with dry and cooler weather Wednesday and Thursday. A frontal system may bring unsettled weather by the end of this week then a low pressure may affect the region sometime Sunday into next Monday. && .NEAR TERM /THROUGH TONIGHT/... 7 am update... Scattered showers with embedded heavier downpours were continuing to impact far SE New England this morning. Instability limited beneath the right rear quadrant of the upper level cold front and ahead of a weak cold frontal boundary and stretched mid-level vortex energy. Should see a gradual conclusion to this activity over the next few hours. Trend for today is for the morning activity and mugginess to shift SE and offshore behind which conditions should clear and turn drier with lower dewpoints as we warm well into the 80s as mixing proceeds up to H85 where temperatures of around 12-14c will reside. Cooler along the shores. Plenty of sunshine as the weak cold front moves offshore this afternoon. && .SHORT TERM /WEDNESDAY/... Tonight... A second cold front will move south across the region which will shift winds to north as high pres builds to the north across Canada. Mainly clear skies expected with low temps dropping into the 50s. Wednesday... High pres shifts to the Maritimes with surface ridging extending across SNE. Expect mostly sunny skies, but enough low level moisture for some BKN cumulus developing, especially across central and western New Eng. A cooler airmass will overspread the region as easterly flow develops. Highs will range from the upper 60s across east coastal MA to around 80 in the CT valley, with 70s elsewhere. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... */ HIGHLIGHTS... - A shift from Summer-like conditions back to more typical Spring - A bit of a chill Thursday and Friday with onshore flow - Cold front and wet weather for late Friday into Friday night - Mostly quiet for the weekend - Unsettled and prolonged cool, wet weather by early next week */ DISCUSSION... Persistence and morphology of low pressure over the Gulf of Alaska maintains and manages ridging across the W and Central CONUS. The +PNA / +EPO pattern over time modifies -NAO / -AO teleconnections. Subsequently the warmer than average conditions under higher heights this week shift towards around average beneath anomalously low H5 heights on the order of -1 to -2 standard deviations per ensemble means. In other words, a shift away from the Summer-like feel towards a slightly atypical Spring-time pattern. Nothing noteworthy stands out through the extended forecast. Onshore flow looks to keep the E cool Thursday and Friday. An isallobaric / pressure gradient response with high pressure N/E and a sweeping cold front for late Friday into Friday night. A good chance of wet weather with the sweeping cold front but will prevail with chance PoPs as the cold front becomes removed from more favorable dynamics into a region of low-level ridging and poor low-level lapse rates over the immediate SE neighbored by S-stream disturbances, namely the remnants of Bonnie moving NE from the Carolinas. High pressure and a slightly cooler airmass aloft follow for the weekend. Perhaps some shower activity to the N driven by additional mid-level energy and destabilization of the local atmosphere per a reinforcing cooler airmass from the N during the day via diurnal heating. Into early next week, looking at the bigger picture and focusing on ensemble means. Quite the spread in individual ensemble member forecasts. Anomalous troughing pattern with accompanying mid- level vortex energy and jet dynamics. An unsettled, cooler, wet weather pattern unfolding. Plausible such a pattern lasts into the end of the week. Will keep with chance PoPs and lean towards temperatures that are near or below average for early June. && .AVIATION /12Z 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/... Today...High confidence. A mix of MVFR/IFR lingering for the SE coastal terminals into midday with -RA and a low risk of TSRA. Low conditions holding out the longest on ACK. Either VFR or improving to VFR elsewhere. W winds. Tonight and Wednesday...High confidence. VFR. Easterly winds developing Wednesday. KBOS TAF...Will hold the terminal at VFR for the forecast period. KBDL TAF...A low risk of nearby fog becoming an issue, but confident the morning and thus the remainder of the day will be VFR. Outlook /Wednesday Night through Saturday Night/... Wednesday night into Friday... VFR. E onshore flow, breezy especially across E-coastal terminals, turning SE late. Late Friday into Friday Night... MVFR / Low-End VFR. S flow, potentially breezy, backing W/NW. SHRA possible. Saturday into Saturday Night... VFR. Breezy N/NE flow persists becoming light towards Sunday morning. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday/... Today and Tonight...High confidence. Windspeeds will remain below 20 kt with SW winds today shifting to north tonight. A southerly swell will result in seas building to 4 feet over the southern waters with a low prob of 5 ft seas. Wednesday...High confidence. NE winds and seas below SCA. Outlook /Wednesday Night through Saturday/... Thursday into Friday... E onshore flow, breezy especially across the E-coast, turning SE late. A low risk of 5-foot waves over the E/SE outer waters. Late Friday into Friday Night... S flow, potentially breezy, backing W/NW with the passage of a cold front along and ahead of which some shower activity is possible. Not thinking any restrictions to visibility. Waves remaining below 5- feet. Saturday into Saturday Night... Breezy N/NE flow persists becoming light towards Sunday morning as high pressure moves across the region. Waves remaining below 5-feet. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...KJC/Sipprell NEAR TERM...KJC/Sipprell SHORT TERM...KJC LONG TERM...Sipprell AVIATION...KJC/Sipprell MARINE...KJC/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.