Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 171428 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 1028 AM EDT Tue Sep 17 2019 .SYNOPSIS... Expect a quiet spell of weather through the week with mild days and cool nights. There is a spot chance of a shower tonight into Wednesday, but a dry forecast for most people/areas. Temperatures warm up late week into the weekend. Dangerous surf and rip currents will develop along ocean facing beaches due to well-offshore Humberto. The next best chance at any rainfall in the form of showers is forecast for early next week. && .NEAR TERM /THROUGH TONIGHT/... High pressure over Eastern Canada is building over Southern New England. This will turn winds from the northeast and east during the afternoon over Eastern MA and RI and the Central Hills, while CT and Western MA remain more northerly. An area of cloud-level moisture moves into Northeast MA later this afternoon. This may be enough to generate partly cloudy skies, mainly from the Merrimack River to Boston. Temps aloft are forecast at 5C east to 7C west, supporting max temps in the mid 60s to lower 70s. && .SHORT TERM /WEDNESDAY/... Onshore flow continues tonight into Wednesday. Colder air will continue to flow into our region, with Wednesday probably being the coldest day this week. As temperatures lower, expecting marine stratus to develop and move onshore. The layer of higher moisture content is rather shallow beneath a substantial subsidence inversion. Temperature differential for ocean enhancement is impressive for mid September. There may be a few sprinkles to contend with tonight into Wednesday morning. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... */ Highlights... - Mild days, cool nights through the week, dry throughout - Turning warmer over the weekend into next week - Next chance of rain may not be till early next week */ Overview... Transitioning warmer? Mild days, cool nights through the week but by the weekend into the following week we could see warmer than average conditions. Positive teleconnections across the board minus the PNA. WPO/EPO strongest into late September signaling a strong Pacific jet into western N America. Mid-latitude energy downsheared across the W CONUS as a prominent MJO is forecast over the W Hemisphere / Africa (phase 1/8), the potential combination N Atlantic tropical waves / latent heat release with favorable downstream E CONUS ridging from an onshore mild Pacific jet supports warmer than average conditions advertised by CPC 6-10 / 8-14 day outlooks. All signs point towards higher heights late September across New England. With that there does not seem to be much rainfall opportunity. Ensembles showing out through the rest of the month there`s an SW-NE E CONUS axis into S New England of less than an inch of total rainfall. Deterministic forecast guidance highlights our next best chance of rainfall early the following week. Looks like we`re in store for a long period of dry weather which is not atypical as September is one of more drier months on average. Neither is warmer than average temperatures. A glance back at records for late September, we`ve observed upper 80s to low 90s for highs. An ensemble blend forecast with lower certainty on specifics further out in the forecast. Warming trend into the weekend as high pressure shifts E and S/SW winds prevail prior to a sweeping cold front early the following week with a chance of showers. Could see a brief cool down thereafter before warmer weather builds back in as we go into Autumn. && .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/... This afternoon... VFR, with cloud bases around 4000 feet. Best chance for clouds will be around the Merrimack Valley and Boston. N wind becoming NE at 5 to 15 kt. Gusts up to 20 kt may occur across the Cape and Islands by mid to late afternoon. Tonight and Wednesday... Mainly VFR. A period of BKN 020-030 MVFR ceilings along with a passing SHRA or two possible across portions of E MA tonight into Wednesday morning. Lower MVFR possible along the high terrain down to 010. KBOS Terminal... High confidence in TAF. 020 MVFR possible tonight into Wednesday. KBDL Terminal... High confidence in TAF. Outlook /Wednesday Night through Saturday/... Wednesday Night through Thursday: VFR. Breezy. Thursday Night through Saturday: VFR. && .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. This afternoon... N/NE wind with afternoon gusts up to 20 knots. Seas 2-4 ft. Tonight and Wednesday... NE wind gusts around 20 knots at times in the cool air advection pattern. Gusts increasing up to around 25 kt Wednesday afternoon. Seas increasing 3-5 ft by early Wednesday morning across the open waters. Will need to consider Small Craft Advisories with later forecasts. Outlook /Wednesday Night through Saturday/...Moderate confidence. Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Thursday through Thursday Night: Winds less than 25 kt. Local rough seas. Friday through Friday Night: Winds less than 25 kt. Rough seas up to 10 ft. Saturday: Winds less than 25 kt. Areas of rough seas. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Belk/Sipprell NEAR TERM...WTB/Belk/Sipprell SHORT TERM...Belk LONG TERM...Sipprell AVIATION...Belk/Sipprell MARINE...Belk/Sipprell is the U.S. government's official web portal to all federal, state and local government web resources and services.