Area Forecast Discussion
Issued by NWS Boston, MA
Issued by NWS Boston, MA
306 FXUS61 KBOX 020608 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 208 AM EDT Tue Sep 2 2025 .SYNOPSIS... High pressure remains in control through at least Thursday, bringing an extended stretch of dry weather and seasonably warm temperatures. Turns more humid by Friday, with an approaching cold front bringing showers and a chance of thunderstorms. Warm and humid conditions and risk for showers linger into Saturday ahead of the cold front, then cooler and drier weather returns next Sunday and Monday behind the cold front with slightly below normal temperatures. && .NEAR TERM /THROUGH TODAY/... Key Messages: * Areas of fog and seasonably cool temperatures to kick off the day. * Warm and generally sunny this afternoon, though will have some fair weather clouds. Hard to believe it, we have officially began meteorological fall on September 1st. With these shorter days and longer nights, will start to experience a shift towards cooler temperatures. Usually this time of year we can experience areas of morning fog due to the process of radiational cooling, which is occurring this morning. Already finding areas of fog in prone locations; river valleys and hollows. As well, temperatures are seasonably cool in the 50s, but a few areas that are able to fully radiate and are located in a depression/bowl are likely to have even cooler temperatures in the 40s. Nevertheless, it is a sign of the times now that the calendar has moved to September. Lingering morning fog will erode, giving way to a mainly clear day. The upper level disturbance has shifted north and will have surface high pressure today. Expecting fair weather clouds, BUFKIT soundings shows a well mixed boundary layer this afternoon to 850mb. Winds aloft area fairly weak and do not anticipate and significant wind gusts. Temperatures are nearly +8C to +10C aloft, this should yield highs in the middle and upper 70s. Cannot rule out a few 80F in the broader CT River Valley. Will be a touch cooler at the coast as we anticipate a light on shore wind. && .SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/... Key Messages: * Carbon copy, another seasonably chilly night ahead with areas of radiational fog, followed by a mainly sunny and warm Wednesday. No notable changes, expecting effective radiational cooling tonight under clear skies with light to calm wind, results in temperatures lowering through the 50s, with the coldest locations in the 40s. And as with today, cannot rule out fog to develop, lingering into Wednesday morning. 850mb temperatures are warmer Wednesday afternoon, +10C to +12C, and expect highs in the upper 70s to 80F across much of the region. As with today, have high pressure and a weak pressure gradient, thus an on shore wind will keep coastal areas a touch cooler. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... Key Messages: * Dry with seasonable temperatures Thursday. * Next chance for rainfall arrives by Friday with rain and a some embedded thunderstorms possible later in the day. * Front moves through by Sunday bringing slightly below normal temperatures for Sun/Mon. Deterministic/ensemble guidance show the extended period to be dominated by an upper ridge across the western CONUS and troughing across the east. On Thursday, high pressure will weaken through the day in response to an upper level trough shifting eastward across the Great Lakes region. Thursday should still remain dry with temperatures in the 70s to around 80. An upper low center slowly moves across eastern Canada before lifting north Thursday through the first half of the weekend. Ensemble guidance keeps the associated trough and shortwave energy to the north and west of southern New England as it tracks closer to the northeast on Friday. Forcing will be more limited; however, there should be weak ascent and sufficient moisture to support rain Friday. There will be sufficient instability in place later Friday which may support embedded thunderstorms. Across ensemble guidance, the highest probabilities for rain amounts are in the 0.01-0.50" range with the best chances for the upper range in western parts of the region. With the potential for embedded thunderstorms and above normal moisture present, localized areas may receive high amounts of rainfall. We`ll be able to tap into more detail as we get closer.. Dry air/high pressure offshore and limited forcing may keep the Cape/Islands on the lower end of the rainfall range. Temperatures should range in the mid 70s to near 80 with higher humidity with breezy SW winds. Model guidance hints at another brief wave that may bring a secondary round of scattered light showers on Saturday. We still remain in the "warmer" airmass on Saturday which will support similar temperatures/humidity levels to Friday. A cold front will push through later Saturday into early Sunday bringing back cooler highs and lower humidity Sunday and Monday. Highs will likely range slightly below normal in the lower 70s and even some upper 60s in the higher terrain spots. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today... High Confidence. VFR. Patchy radiational fog developing, could impact terminals with brief IFR conditions in protected areas, i.e. KBED, KBAF, and KBDL. Calm wind becomes easterly 7-10 knots. Tonight... High Confidence. VFR. Calm wind. Patchy radiational fog developing, could impact terminals with brief IFR conditions in protected areas, i.e. KBED, KBAF, and KBDL. Wednesday... High Confidence. VFR. Southeast wind up to 10 knots for eastern MA terminals. South to south/southwest wind elsewhere 5-8 knots. KBOS Terminal...High confidence in TAF. VFR. Radiation fog development south of the terminal near Hull as of 06z but think the N to NE wind shunts any northward development. That said, the pressure gradient is weak due to surface high pressure, if wind direction were to become ESE to SE, this feature could move towards the terminal. If area of radiational fog expands, will handle with a TEMPO. KBDL Terminal...High confidence in TAF. VFR. But, a low risk of late night patchy fog after 08z. Outlook /Wednesday Night through Saturday/... Wednesday Night: VFR. Thursday: VFR. Breezy. Thursday Night: VFR. Chance SHRA. Friday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, slight chance TSRA. Friday Night: VFR. Breezy. Chance SHRA. Saturday: VFR. Breezy. Chance SHRA, slight chance TSRA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Through Wednesday... High Confidence. Area of high pressure remains in control and provides tranquil boating conditions. Easterly winds today are generally 10-15 knots, then becoming light to calm overnight. Wind shifts more to the southeast Wednesday, wind speeds 5-10 knots. Gusts both days are less than 20 knots and seas 2-4 feet. Outlook /Wednesday Night through Saturday/... Wednesday Night through Thursday Night: Winds less than 25 kt. Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers. Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers. Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...None. && $$ SYNOPSIS...Dooley/Mensch NEAR TERM...Dooley SHORT TERM...Dooley LONG TERM...Mensch AVIATION...Dooley/Mensch MARINE...Dooley/Mensch