AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 217 PM EST Wed Mar 4 2026 .WHAT HAS CHANGED... Winter Weather Advisories have been issued for Thursday late afternoon into noontime Friday as initial rain changes to a wintry mix of freezing rain, sleet and light-accumulating snow. Slippery roads can be expected, with tree and powerline damage also possible where ice totals are higher. Mild weather this weekend into early next week could cause river rises due to snowmelt. && .KEY MESSAGES... - Patchy fog possible tonight across the region with light to calm winds. Black ice will likely be an issue again Thursday morning. - Rain Thursday changes to a wintry mess of freezing rain, sleet and even some snow Thursday night into Friday in most areas away from southeast New England. Slippery roads are likely, and the potential exists for tree and powerline damage in interior high terrain if greater ice accretions materialize. - Pattern change toward milder temperatures remains in the cards for the weekend. Snowmelt could cause within-bank rises on streams, creeks and larger rivers into early next week. && .DISCUSSION... Key Message 1...Patchy fog possible tonight across the region with light to calm winds. Black ice will likely be an issue again Thursday morning. Fog finally cleared out in the CT Valley this afternoon, and as a result, high temperatures there this afternoon may reach the mid 40s at the highest. Temperatures fall quickly tonight across the region after sunset as winds go light to calm along with the effects of the snowpack. The snowpack across the region in combination with dewpoints and air temperatures in the 20s and upper teens will likely lead to patchy fog developing late tonight, especially after midnight. Freezing fog will also be a concern with temperatures falling below freezing, so black ice will be a concern once more tomorrow morning. Key Message 2...Rain Thursday changes to a wintry mess of freezing rain, sleet and even some snow Thursday night into Friday in most areas away from southeast New England. Slippery roads are likely, and the potential exists for tree and powerline damage in interior high terrain if greater ice accretions materialize. An elongated, west-east oriented surface warm front with parent 500 mb shortwave disturbance will be attempting to build northward from the mid-Atlantic/Ohio Valley region Thurs into early Fri. As it does so, it will be running into a shallow sub-freezing airmass building southward from NH/ME on increased NE winds. While initial plain rain will develop in many areas Thurs, falling temps through the 30s into the mid/upper 20s will be enough to facilitate a transition from rain to a wintry mess of freezing rain, sleet and now even some light accumulating snow starting early Thurs night through Fri morning away from southeast New England. From a travel standpoint, this is likely an especially problematic precip type changeover evolution, given rain to wintry mix, which lends itself to slippery roads. Winter Weather Advisories have been posted starting 5 PM Thursday through noon Friday. Forecast guidance has trended a little colder with 925-850 mb temps today, which results in a larger portion of Southern New England to experience a rain to wintry mix than previous indications, while at the same time opening the door for some accumulating snow along the NH/MA border. Although ice accretions of at least a light glaze are expected in much of the Advisory area, tried to hit the higher terrain in CT and MA as having the greatest ice accretions, which are up to around a quarter to third of an inch. If those higher totals materialize, the risk for tree and powerline damage would increase and feel those are possible in the higher terrain. Up to 2 inches of combined sleet and snow accumulation are forecast along the Route 2 corridor into the North Shore. But because of the cooler trend in guidance and that very subtle changes in surface to lower- atmospheric temperatures will drive the duration of precip types and accumulations, I wouldn`t rate confidence in specific snow/ice accumulations as being high; future adjustments in either/both are possible. But strong confidence exists in the impacts being at least slippery/icy roads, but could also include a risk for tree and powerline damage if higher ice totals over a quarter-inch develop, and that was the rationale for the Winter Weather Advisories. Precipitation comes to an end Friday mid to late morning; but of some concern is that there could be lingering freezing mist/freezing drizzle even after precip ends in some interior locations Friday afternoon. If that develops, it could lead to continued slippery roads into a good part of Friday. Nonetheless, expect a cloudy, chilly and raw Friday with highs only in the 30s, with highs in the low 30s around the interior higher terrain. Key Message 3...Pattern change toward milder temperatures remains in the cards for the weekend. Snowmelt could cause within-bank rises on streams, creeks and larger rivers into early next week. Significant pattern change takes place for the weekend as anomalously strong SWly flow aloft advects in well above normal 850 mb temperatures Sat/Sun, as high as 10-13C. These would be some 15 degrees Celsius warmer than climatological 850 mb temps for early March. Mixing looks shallow despite the very warm 850 mb temps on Saturday, which could keep highs closer to the mid 40s to lower 50s. Still, highs some 10-15 degrees above normal should develop Sun with highs in the 50s to even some spot 60s. Rising dewpoints into the mid 40s/around 50 will also eat away at the standing snow depth, too. There is a frontal system which looks to move in around Saturday night into Sunday, bringing light rains. Some rises on rivers are anticipated from melting snow during the weekend to early next week based on GEFS/NAEFS hydrologic forecasts. Will have to monitor the western watersheds for at least within-bank rises into early next week, though potential for some to reach flood stage if we get any rainfall on top of the melting snow. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 18z TAF Update... Rest of Today...High confidence. Lingering IFR conditions in the CT Valley are finally starting to clear and should continue to lift to VFR within the next hours or so. Otherwise, VFR for the rest of today across southern New England with light SW winds for most (winds more N to NE in the CT Valley), aside from localized sea breezes along the immediate coast for some terminals. Tonight...Moderate confidence. VFR this evening, but areas of low clouds and fog may develop late resulting in MVFR-IFR conditions with even localized LIFR cigs/vsbys. While low clouds and fog patches are possible anywhere late tonight, guidance continues to indicate the greatest risk for it being most widespread across CT/RI and southeast MA. Light/calm winds. Thursday...Moderate confidence. The initial morning low clouds/fog patches may briefly burn off. Widespread MVFR to localized IFR conditions expected to overspread the region from southwest to northeast, particularly in the evening hours into Thursday night with rain mixed with some sleet moving in. Light NE winds. Thursday Night...Moderate confidence. IFR/LIFR ceilings with IFR/MVFR visbys. FZRA and RA expected across the region, moving in from SW to NE starting in the evening hours. NE winds pick up slightly to be around 6-12 kt sustained with occasional gusts to 20 kt possible in higher elevations and towards the Cape/Islands. KBOS Terminal...Moderate confidence in TAF. Main uncertainty is timing of category improvments tomorrow. Confidence in any seabreeze for the rest of this afternoon is very low. KBDL Terminal...Moderate confidence in TAF. Main uncertainty is timing of category improvements tomorrow. Outlook /Friday through Monday/... Friday: MVFR/IFR conditions possible. Breezy. Chance RA, chance FZRA. Friday Night: MVFR/IFR conditions possible. Slight chance RA. Saturday: Mainly VFR, with areas IFR possible. Breezy. Slight chance RA. Saturday Night: Mainly VFR, with local IFR possible. Breezy. Chance RA. Sunday: VFR. Breezy. Slight chance RA. Sunday Night: VFR. Monday: && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through Thursday Night...High confidence. Lingering southerly swell will result in small craft seas lingering across our southern waters into the first half of the evening before dropping below criteria. High pressure tonight will keep sustained winds generally 10 knots or less. Low pressure approaching from the west will allow NE winds to increase to between 10 and 20 knots on Thu. Wintry mix moves over the waters for Thursday night and seas in the northern waters begin building again heading into Friday morning. NE winds 10-20 kt continue through Thursday night with occasional gusts to 25 kt. Small craft advisories may be needed then. Outlook /Friday through Monday/... Friday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Chance of rain. Friday Night: Winds less than 25 kt. Areas of rough seas. Saturday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Saturday Night: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Areas of rough seas. Chance of rain, isolated thunderstorms. Sunday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain. Sunday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory from 5 PM Thursday to noon EST Friday for CTZ002>004. MA...Winter Weather Advisory from 5 PM Thursday to noon EST Friday for MAZ002>015-026. RI...Winter Weather Advisory from 5 PM Thursday to noon EST Friday for RIZ001-003. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ254>256. && $$