Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 231929 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 329 PM EDT Wed Aug 23 2017 .SYNOPSIS... A cold front will move offshore this evening. High pressure brings dry weather with very comfortable humidity levels through early next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Brought the forecast back in line with observed trends this afternoon. Not much to talk about tonight. A cold front will finally move offshore this evening. Drier air will overspread our region overnight. Dry weather and mainly clear skies prevail. Patchy fog may develop late in the typically prone locations, but not expecting anything widespread. Near normal minimum temperatures. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... A large high pressure over central Canada will move slowly east Thursday and Thursday night. A mid level trough and shortwave should pass by our region before this high pressure really takes control of our weather. The lower level of the atmosphere are so dry, not expecting more than some clouds at times during this period. Near to slightly below normal temperatures expected through this period. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Not too much change with the 23.12Z models particularly with the synoptic pattern across the CONUS through mid next week. Reinforced Alaskan vortex is the driver for enhanced warm advection downstream, even as the pattern across the W becomes more zonal. Ridging amplifies through the N CONUS and central Canada as a result, and while this maintains a longwave trof across New England, the mean flow into New England is a cool and dry CP draw. Mean SW-NE oriented jet remains entrenched directly over New England within confluent flow, E of the trof baseline. This will help to maintain the slow passage of a 1025+hPa high pres, which will lead to generally dry conditions through mid week. There are two opportunities for spot showers. The first is Friday when a relatively robust shortwave rotates through the region coincident with a slight uptick in PWATs to just shy of 1.00 inches. Mid lvl lapse rates are high enough to enhance the risk. Will continue to time some slight chance POPs through the afternoon. The second is Sunday with a similar situation, but overall weaker dynamics and actually less moisture. Each day will feature only hit-or-miss showers as even at its peak near 1.00 inches, PWATs remain very low through the period. Seasonably cool temperatures will accompany this nearly week long dry period. H85 temps drop to between +5C and +8C at their coolest point following the Friday wave passage and then remain generally within this range through mid next week. Full mixing suggests mid-upper 70s for highs, however as the high pres shifts into the Maritimes Sun-Tue, flow will shift toward the E, drawing air off the Gulf of Maine and leading to cooler highs as a result. Mins will be comfortable thanks to dewpoints holding in the upper 40s and low-mid 50s through the period, suggesting the lows will drop into the 50s most night. All-in-all, temps will remain below normal throughout. && .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/... Tonight...High confidence. Mostly VFR, however a risk of MVFR- IFR for Nantucket during the evening hours. Clear conditions across the interior. May see some patchy MVFR-IFR ground fog develop at the typically prone locations toward daybreak, but nothing widespread is expected. Thursday and Thursday night...High confidence. VFR. KBOS Terminal...High confidence in TAF. Moderate risk for a seabreeze Thursday, mainly from mid morning into the afternoon. It is possible the seabreeze stalls just east of the terminal. KBDL Terminal...High confidence in TAF. Outlook /Friday through Monday/... VFR. Light flow generally NW through Sunday, then shifting toward the E Monday. Sea breezes possible all days. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Thursday Night/...High confidence. Relatively light winds and seas through this period. Rough seas will persist across the southern outer MA coastal waters a while longer. Anticipate the Small Craft Advisory will be able to expire at 4 PM. Local seabreezes possible Thursday from mid morning into the evening. Outlook /Friday through Monday/... Good boating weather. Weak N-NW winds will shift to the E by Monday but with gusts generally remaining below 20 kt. Seas/waves remain below 4 ft through the period. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ255. && $$ SYNOPSIS...Belk/Doody NEAR TERM...Belk SHORT TERM...Belk LONG TERM...Doody AVIATION...Belk/Doody MARINE...Belk/Doody is the U.S. government's official web portal to all federal, state and local government web resources and services.