Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 010645 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 245 AM EDT Sat Oct 1 2016 .SYNOPSIS... A low pressure passes by to our south today. Meanwhile, a high pressure remains over the Maritimes. This combination will mean cool and damp conditions through most of this weekend. Another low pressure moves east across New England Monday and Tuesday. High pressure builds over New England Wednesday and Thursday. Still watching Hurricane Matthew, but uncertain information whether it affects New England, or not. && .NEAR TERM /THROUGH TODAY/... Radar continues to show bands of showers moving north across Southern New England. Lift is rather weak, and mainly the result of a low pressure passing by to our south. As this low pressure moves offshore, we should start to start to get into a dry slot later today. Looking very much like a low QPF/high PoP kind of forecast. Most rainfall rates were less then one tenth inch per hour. Will continue categorical PoPs through this morning, before slowly diminishing them this afternoon. In any case, not expecting a total washout. A large high pressure over the Maritimes will maintain persistent northeast winds. Besides keeping southern New England below normal temperature-wise, this will also keep the low level humidity higher, particularly across RI and southeast MA. Max temperatures today are not expected to be more than 10 degrees higher than the low temperatures this morning. && .SHORT TERM /TONIGHT THROUGH 6 PM SUNDAY/... Our region will still be in range of a potent mid-level cutoff low late tonight into Sunday. This should be close enough to maintain meager convective instability across our region. Despite a period of lower precipitable water values, there should still be enough moisture around for at least a continued chance of showers. Temperatures still below normal thanks to flow off the Gulf of Maine and continued cloud cover. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Big Picture... Longwave pattern continues to show West Atlantic high in place, but shifting south over the weekend. Closed Upper Low over the Ohio Valley shifts north, then moves east as the Atlantic high moves out of the way. This upper low moves over New England Monday and Tuesday. High pressure then moves over the Northeast USA Wednesday and Thursday. Upper low along the British Columbia coast swings across the USA during the week, then lifts northeast across Eastern Canada Friday. And then there is Matthew. There is a great difference in how the models handle the storm, especially north of the Bahamas. The GFS continues to outrun the ECMWF in bringing the storm up the coast, but reacts to the building midweek upper high by dancing and spinning east of our area. The difference continues to be the GFS showing a greater phasing of Matthew with a southern stream shortwave, while the ECMWF shows either no phasing or greatly delayed phasing...and thus a much slower movement north. We favored a model blend for most of the long term. The GFS has been trending slower on Matthew, so a movement away from either extreme seems a good thing. Details... Monday-Tuesday... Upper low and cold pool move overhead Monday and Tuesday. Monday will feature the most instability with GFS-ECMWF-NAM-GGEM showing totals in the upper 40s and lower 50s. This looks mainly to be scattered showers Monday but with enough instability to mention a widely scattered tstm. Less coverage Tuesday, but enough for scattered or widely scattered showers. Surface wind flow will continue from the northeast keeping temps below normal especially in Eastern MA and RI. Mildest temps will be in the CT Valley. Wednesday through Friday... High pressure actually starts building south from Canada on Tuesday, but is most notable starting Tuesday night with temps and dew points cooling into the 40s. The high brings fair and dry weather Wednesday and Thursday with partly sunny skies. Northeast flow continues. Friday currently looks to maintain the dry weather as high pressure moves off through the Maritimes. If Matthew moves close enough, then we could see some showers well out ahead of the system. But very low confidence in such a scenario so we have indicated only slight chance pops in eastern and central sections. Otherwise dry weather. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/... Today...Moderate confidence. Low-end MVFR or IFR cigs linger through the day with on-and-off rain showers lowering vsbys. Tonight...Moderate confidence. May see some minimal improvement during the overnight hours. However, low CIGS will remain an issue. At least MVFR for most of southern New England, with IFR CIGS toward the south coast. Sunday...Moderate confidence. MVFR/IFR cigs and vsbys in showers and fog. Diminishing northeast flow. KBOS TAF...High confidence in trends, moderate confidence in timing. KBDL TAF...High confidence in trends, moderate confidence in timing. Outlook /Sunday Night through Wednesday/... Monday-Tuesday... Low confidence. VFR with areas of MVFR in scattered showers. Wednesday...Moderate confidence. VFR. && .MARINE... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/... High confidence. It will likely take until into Sunday for seas to drop below 5 ft across the eastern, outer coastal waters. With northeast winds gradually diminishing today and tonight, expecting seas to subside as well. Small Craft Advisories will continue for at least a while today. Will likely be able to convert the remaining Gale Warnings to Small Craft Advisories later this morning. Still evaluating the trends. Outlook /Sunday Night through Wednesday/... Diminishing Northeast wind Sunday night and Monday with gusts 20 knots or less. Northeast winds increase again Tuesday and Wednesday on the Southern and Southeast waters with frequent gusts 20-25 knots. Seas 5-6 feet on the eastern waters Sunday but diminishing. Seas build again Tuesday and Wednesday with 5-7 foot seas on the outer waters. Small Craft Advisory will be needed for much of this time period. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 5 PM EDT this afternoon for ANZ232. Small Craft Advisory until noon EDT today for ANZ233-234. Small Craft Advisory until 8 PM EDT this evening for ANZ230- 231-235-237. Small Craft Advisory until 11 AM EDT this morning for ANZ236. Small Craft Advisory until 8 AM EDT Sunday for ANZ250-251-254- 255. Gale Warning until 5 AM EDT early this morning for ANZ256. && $$ SYNOPSIS...WTB/Belk NEAR TERM...Belk SHORT TERM...Belk LONG TERM...WTB AVIATION...WTB/Belk MARINE...WTB/Belk

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