419 FXUS61 KBOX 142250 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 650 PM EDT Wed Oct 14 2020 .SYNOPSIS... High pressure will result in dry weather tonight into Thursday along with an unseasonably mild and breezy Thursday afternoon. Rain develops on Friday as a frontal system stalls across New England with locally heavy rainfall Friday night into early Saturday as a coastal storm moves through. Improving conditions expected Saturday afternoon, then mainly dry and seasonable conditions Sunday into Wednesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 650 PM update... High pres shifts east of New Eng overnight. Just a few high clouds moving into the region tonight, otherwise mainly clear skies and light winds, which will result in temperatures dropping fairly quickly this evening. Low temps will bottom out in the 40s across most of the region. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... * Sunny, Breezy and Unseasonably Mild Thursday Thursday... High pressure will move east of our region on Thursday. This will allow for an unseasonably mild southwest flow of air into the region. Model cross sections are quite dry, so expect sunny skies and SW flow with 850T around +12C will result in an unseasonably mild afternoon. High temperatures should reach the middle 70s in many locations. It will also become quite breezy by afternoon given a modest southwest low level jet and good mixing. We expect south to southwest wind gusts of 25 to 35 mph by afternoon. Thursday night... A surface cold front to our northwest will push southeast Thu night and be located across interior southern New England by daybreak Fri. Southwest flow aloft will continue and low level moisture be on in the increase. This should result in the development of some low clouds and probably a few showers as well after midnight. Low temps will be milder only dropping into the upper 40s and 50s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Highlights * Rain returns Fri with locally heavy rainfall possible Fri night into early Sat * Improving conditions Sat afternoon * Mainly dry and seasonable weather Sun into Wed Friday into Saturday... Robust mid level trough across the Gt Lakes expected to amplify and become neg tilted as it sweeps across New Eng on Sat. Strong synoptic forcing combined with modest PWAT plume will bring widespread beneficial rain to SNE. A period of heavy rainfall likely Fri night into early Sat as strong shortwave energy moves through with a deepening coastal low tracking near the 40N/70W benchmark as impressive height falls develop off the coast. Still some timing differences among the models but confidence is high in widespread beneficial rainfall. Expect periods of rain to develop during Fri as cold front stalls across eastern New Eng. Rain on Fri will be focused along and west of the boundary where deep moisture plume develops. This suggests the steadiest rain on Fri will be confined to much of the interior to near the I-95 corridor with more spotty light rain across SE MA and Cape Cod. Rain heavy at times is expected Fri night, initially across western New Eng then shifting east late Fri night into early Sat. Impressive dynamics with right entrance region of upper jet combined with strong mid level frontogenesis moving west to east will bring the heavy rainfall to SNE. The rain Sat morning will be focused in eastern New Eng with improving conditions from west to east during the afternoon. Rainfall amounts should average 1-2 inches with locally higher amounts. The heaviest rainfall is expected to be in the interior with lighter amounts across SE New Eng but the axis of heavy rainfall may shift. The other concern for Sat is the potential for gusty NW winds behind the storm, but the latest ECMWF has backed off on rapid deepening of the low pres and subsequent strong winds. Temps: Highs should reach well into 60s Fri and possibly near 70 east of the front which will be mainly across SE New Eng, with 50s in the interior. Highs saturday mainly in the 50s. Regarding coastal flood potential, there is a low risk of minor splashover for the Fri night tide cycle as a result of the increasing astronomical tides. But this would be the worst case scenario as winds and waves not expected to be significant which will limit surge. Another round of minor splashover is possible for the Sat midday high tide which gets to 11.9 ft in Boston Sunday through Wednesday... Broad longwave trough sets up across the upper Midwest and Great Lakes with subtropical ridge off the SE US coast. Mainly dry weather expected although a few showers are possible at times in the interior as series of shortwaves lifts to the north, but better chance of showers will be to the north and west. Mainly seasonable temps expected, but it could be warmer than forecast Tue/Wed as ECMWF is more aggressive building the subtropical ridge north along the coast toward midweek. ECMWF ensembles offering low probs of 70+ degree temps Tue/Wed. GFS keeps the polar jet further south which suppresses the ridge. Tides: Astronomical tides peak at 12.1 ft in Boston Sunday and Monday afternoon which may result in minor splashover. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00z Update... Tonight...High Confidence. VFR conditions with winds becoming light and from the SW. Thursday...High Confidence. VFR conditions. SSW wind gusts of 20 to 30 knots developing by afternoon. Thursday night...Moderate confidence. VFR conditions during the evening, but some MVFR ceilings may develop after midnight and there probably will be a few showers too. Light SW winds. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Friday through Monday/... Friday: Mainly MVFR, with areas VFR possible. Chance RA, chance SHRA. Friday Night: Mainly MVFR, with local IFR possible. Breezy. RA. Saturday: Mainly VFR, with areas MVFR possible. Windy with gusts up to 30 kt. Chance RA. Saturday Night: VFR. Breezy. Sunday through Monday: VFR. && .MARINE... Tonight...High confidence. High pressure in control will keep winds/seas generally below SCA thresholds. Thursday and Thursday night...High confidence. Modest LLJ will result in SSW wind gusts of 20 to 30 knots developing by afternoon and continue into the evening. SCA headlines posted for all our waters with rough and choppy seas expected as well. Wind gusts should diminish a bit as the SW LLJ lifts northeast of our region. Outlook /Friday through Monday/... Friday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain. Friday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Rain. Saturday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Chance of rain. Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Sunday: Winds less than 25 kt. Seas locally approaching 5 ft. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday: Winds less than 25 kt. Seas up to 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 8 AM Thursday to 2 AM EDT Friday for ANZ231>235-237-251. Small Craft Advisory from 10 AM to 8 PM EDT Thursday for ANZ230-236. Small Craft Advisory from 8 AM Thursday to 5 AM EDT Friday for ANZ250-254>256. && $$ SYNOPSIS...KJC/Frank NEAR TERM...KJC/Frank SHORT TERM...Frank LONG TERM...KJC AVIATION...KJC/Frank MARINE...KJC/Frank