AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 550 AM EST Tue Dec 16 2025 .WHAT HAS CHANGED... Confidence continues to increase for potential wind and minor coastal flood impacts Thursday night into Friday. && .KEY MESSAGES... - Strong and possibly damaging winds possible late Thursday night into Friday with Gale force winds on MA/RI waters. - Minor coastal flooding possible along south facing shores around high tide Friday morning. && .DISCUSSION... KEY MESSAGE 1...Strong and possibly damaging winds. Main concern for this forecast is a "warmer" storm system that is expected to track through the Great Lakes and swing a strong cold front through southern New England Friday morning. Models are in good agreement in showing a 500 mb trough becoming negatively tilted as it rotates through New England, with decent moisture transport and a fairly robust wind field aloft with 60-80kt low level jet at 925 and 850 mb, though we`re seeing a trend that these stronger lower level winds will materialize as system reaches Gulf of Maine, and as a result, NBMv4.3 probabilities for 50+ mph winds have come down a bit since yesterday, although NBMv5.0 shows better potential especially across RI and SE MA as well as coastal waters. Taking a look at ensemble wind probabilities and a cursory look at NAM/GFS forecast soundings gives higher confidence for southerly gusts in 40-50 mph range late Thursday night into Friday, but if we can warm into upper 50s Friday morning, we would be able to more easily mix down 50-60 mph winds which would increase the potential for wind damage. Additionally, we will need to keep an eye on possibility of a fine line of convection developing along cold front as it crosses SNE Friday morning which could bring brief downpours and stronger wind gusts but that is highly dependent upon having some instability, something that can be seen on 00z RRFS which has 100-200 J/kg of MUCAPE. Behind front, cold advection takes hold with W/NW winds potentially gusting to 40-50 mph, especially across higher terrain and near coast (and on coastal waters) due to deepening mixed layer and strong pressure rises. Another shot of cold arrives Friday afternoon into Saturday, albeit not as cold as what we just experienced. KEY MESSAGE 2...Minor coastal flooding. Confidence is lower than with wind impacts described above due to timing of when highest surge will arrive and if it will coincide with high tide along South Coast Friday morning, roughly between 6 and 8 AM. This is tied to how quickly stronger winds can ramp up and to some extent offshore seas as well. If everything comes together, the worst case scenario would be for minor coastal flooding along South Coast (less than 1 foot deep on vulnerable shore roads) since we would need a surge close to 3 ft. Stevens Institute ensemble guidance shows a potential 1-2 ft surge while P-ETSS is under 1 ft and probably underdone. Erosion should not be much of a factor given offshore seas of 10-15 ft and only this high tide cycle being affected. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 12z TAF Update: High confidence. VFR through the period. W winds around 10kt back to SW this afternoon, then increase overnight and Wed with gusts of 20-30kt. KBOS Terminal...High confidence in TAF KBDL Terminal...High confidence in TAF. Outlook /Thursday through Saturday/... Thursday: VFR. Breezy. Thursday Night: MVFR/IFR conditions possible. Strong winds with gusts up to 45 kt. Chance RA. Friday: Mainly MVFR, with local IFR possible. Strong winds with gusts up to 45 kt. Chance RA. Friday Night: VFR. Windy with gusts up to 35 kt. Saturday: VFR. Breezy. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today Through Wednesday Night...High confidence. Calm winds and seas under a ridge, with a high pressure system sitting south of our waters. Winds and seas begin to build late tonight through Wednesday morning into SCA levels. Wind gusts over the far southern and far northern waters look to be on the higher end of SCA and may reach marginal Gales but not confident enough to raise Gale Warnings at this time. Outlook /Thursday through Saturday/... Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Thursday Night: Moderate risk for gale force winds with gusts up to 45 kt. Rough seas up to 14 ft. Chance of rain. Friday: gale force winds with gusts up to 45 kt. Rough seas up to 16 ft. Rain. Friday Night: Strong winds with areas of gusts up to 45 kt. Rough seas up to 13 ft. Slight chance of rain. Saturday: 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 3 AM to 4 PM EST Wednesday for ANZ230. Small Craft Advisory from midnight tonight to 10 PM EST Wednesday for ANZ231-251. Small Craft Advisory from 1 AM to 10 PM EST Wednesday for ANZ232>235-237. Small Craft Advisory from 3 AM to 6 PM EST Wednesday for ANZ236. Small Craft Advisory from midnight tonight to 6 AM EST Thursday for ANZ250-254>256. && $$