Area Forecast Discussion

621 FXUS61 KBOX 030729 AFDBOX Area Forecast Discussion National Weather Service Boston/Norton MA 229 AM EST Tue Mar 3 2026 .WHAT HAS CHANGED... No signficant changes made to the wintry mix today and tonight...but some black ice is a concern after this activity departs for the early Wednesday morning commute. && .KEY MESSAGES... - Mainly snow arrives from southwest to northeast between 11 am and 3 pm then changes to rain near the coast but with pockets of light freezing rain across the interior into tonight. Snow accumuluations a coating to 2" with ice accretion up 0.10". - Areas of black ice possible early Wed morning. Otherwise...dry & milder Wed with highs in the upper 40s to the middle 50s. The one caveat is if fog hangs on later than expected...highs will be cooler than currently forecast. - A period of wintry precip remains possible Thu night into early Fri. - Pattern change towards milder weather this weekend and potentially warmer next week. && .DISCUSSION... KEY MESSAGE 1...Mainly snow arrives from southwest to northeast between 11 am and 3 pm then changes to rain near the coast but with pockets of light freezing rain across the interior into tonight. Snow accumuluations a coating to 2" with ice accretion up 0.10". A large 1040 mb high pressure system will continue to shift further east and way from the region today. At the same time...shortwave energy will approach from the west so brief morning sunshine will quickly fade by lowering and thickening clouds. This shortwave will also induce a modest southwest LLJ on the order of 35 to 45 knots. This will increase the forcing for ascent and precipitation should arrive from southwest to northeast...roughly between 11 am and 3 pm. Thermal profiles indicate antecedent airmass should initially be cold enough for mainly snow except perhaps the immediate south coast, Cape and Islands. Given light to moderate intensity during the daylight hours...the early March sun angle will probably keep roads wet/slushy outside the highest terrain. Snow accumulutations of a coating to 2 inches of snow with higher amounts expected north of I-90. High pressure sliding directly east of our lattitude...mid level warmth will quickly overspread the region. This will allow snow to change to rain along the coastal plain from south to north with perhaps a brief period of sleet during the transition...roughly in the 4 to 8 pm time frame. Periods of rain & drizzle will continue tonight across the coastal plain along with areas of fog. The bigger concern will be northwest of I-95 and into parts of the interior where temps will remain at or below freezing into Tue night. This will result in the snow transitioning to pockets of light freezing rain. Ice accretion of up to one tenth of an inch are possible and untreated roads/walkways may become icy tonight. Departing shortwave should bring an end to the precipitation toward daybreak. Light winds and perhaps some clearing may result in areas of fog and black ice for the Wed morning commute. Key Message 2...Areas of black ice possible early Wed morning. Otherwise...dry & milder Wed with highs in the upper 40s to the middle 50s. The one caveat is if fog hangs on later than expected...highs will be cooler than currently forecast. Give the left over low level moisture, light winds, and near or sub- freezing temperatures will have to watch for areas of fog and black ice early Wed morning. Otherwise...subsidence behind tonight/s shortwave should allow plenty of sunshine and 925T reamin between +5C and +6C. This should yield a mild Wednesday afternoon with highs in the upper 40s to the middle 50s. Most locations away from the immediate coast/sea breeze potential should break 50! The one caveat is the potential for low clouds/fog patches to hang on later than expected. Given very weak surface flow this can not be ruled out...so if this were to occur highs would be lower than currently forecast. Key Message 3...A period of wintry precip remains possible Thu night into early Fri. Mid to late week the synoptic pattern remains flat and zonal with the first shortwave moving through late Thursday into Friday. This, while a 1040mb high pressure sits over southeast QC setting up a potential cold air damming situation. While the mid level disturbance moves through a moist environment on Thursday bringing rain to much of the area, stubborn NE surface flow into the high terrain will likely keep temps below freezing leading to the possibility of freezing rain. The risk for now looks to be limited to the high terrain of interior MA and CT where ensemble guidance paints a 20-35% chance of at least a tenth of an inch of ice overnight. Key Message 4...Pattern change towards milder weather this weekend and potentially warmer next week. There continues to be good model agreement in a pattern shift looking into the extended forecast with an Atlantic ridge leading to warmer SW flow directed into southern New England. However, there remains a good degree of uncertainty as to the magnitude and duration of the warm up given the quick, transient pattern; GEFS plumes show a big increase in spread in 2M-Temp guidance beyond Friday highlighting that lower confidence. Overall, though, high temperatures in the low 50s are possible this weekend with perhaps even some low 60s as we go into the new week. This with a high March sun angle and elevated dewpoints will help to melt away our existing snowpack. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 06z TAF Update... Today and tonight...High confidence in trends with moderate confidence in timing. MVFR-IFR conditions in mainly snow overspread the region from southwest to northeast in the 15z to 20z time frame. Ptype initially mainly snow but a quick change to rain from south to north occurs in the 21z to 01z timeframe along the coastal plain with perhaps a brief period of sleet during the transition. However...across portions of the interior temps near or just below freezing will result in snow/sleet transitioning to pockets of light freezing rain by early evening. IFR to LIFR conditions expected tonight with periods of rain along the coastal plain and pockets of light freezing rain across parts of the interior. Winds generally less than 10 knots today and tonight. KBOS Terminal...High confidence in TAF. Snow arrives near of just after 19z and flips to rain by 23z with perhaps a brief period of sleet during the transition. Little impact on runways expected. KBDL Terminal...High confidence in TAF. Snow arrives around 16z/17z and flips to light rain/freezing rain by 22z/23z with perhaps a period of sleet during the transition. Temps this evening will be near freezing...so impacts may be somewhat limited on runways but some icing can not be ruled out. Wednesday...Moderate confidence. MVFR-IFR with even localized LIFR conditions in low clouds/fog patches early Wed morning improve to VFR by Wed afternoon. It is possible fog could linger longer in low lying locations given very weak winds/poor mixing. Outlook /Wednesday through Saturday/... Wednesday: VFR. Wednesday Night: VFR. Slight chance FZRA. Thursday: Mainly VFR, with local IFR possible. Chance RA, slight chance FZRA. Thursday Night: Mainly IFR, with areas MVFR possible. Breezy. Chance RA, chance FZRA. Friday: MVFR/IFR conditions possible. Breezy. RA likely, FZRA likely. Friday Night: Mainly VFR, with areas IFR possible. Slight chance RA, slight chance FZRA. Saturday: Mainly VFR, with local IFR possible. Breezy. Slight chance RA. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Today through Wednesday...High confidence. High pressure continues to move east of the waters today. This will result in long S-SW fetch and build seas into the 3 to 6 foot range late tonight into Wed across our southern waters. Therefore...we have issued small craft advisories for our southern outer- waters. Outlook /Wednesday through Saturday/... Wednesday: Winds less than 25 kt. Seas up to 5 ft. Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain, slight chance of freezing rain. Thursday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain, slight chance of freezing rain. Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Rain likely. Friday: Winds less than 25 kt. Areas of rough seas. Rain likely. Friday Night through Saturday: Winds less than 25 kt. Areas of rough seas. Slight chance of rain. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory from noon today to 7 AM EST Wednesday for CTZ002>004. MA...Winter Weather Advisory from noon today to 7 AM EST Wednesday for MAZ002>012-014-026. RI...Winter Weather Advisory from noon today to 7 AM EST Wednesday for RIZ001. MARINE...Small Craft Advisory from 10 PM this evening to 7 PM EST Wednesday for ANZ254>256. && $$ DISCUSSION...Frank/BW/Nocera AVIATION...Frank/BW MARINE...Frank/BW/Nocera NWS BOX Office Area Forecast Discussion