Nantucket Sound Marine Forecast
| Today...Nw Winds 5 To 10 Kt, Becoming Sw This Afternoon. Seas Around 2 Ft. Wave Detail: Nw 2 Ft At 3 Seconds And Ne 1 Foot At 6 Seconds. A Slight Chance Of Freezing Rain This Afternoon. |
| Tonight...Se Winds 5 To 10 Kt, Becoming E 15 To 20 Kt With Gusts Up To 25 Kt After Midnight. Seas 1 Foot Or Less, Then 2 To 3 Ft After Midnight. Wave Detail: S 1 Foot At 2 Seconds And Ne 1 Foot At 4 Seconds, Becoming Se 3 Ft At 5 Seconds. A Chance Of Snow In The Evening, Then Snow And Rain With Freezing Rain Likely After Midnight. Vsby 1 Nm Or Less. |
| Sun...E Winds 20 To 25 Kt, Becoming S In The Afternoon. Gusts Up To 30 Kt. Seas 4 To 6 Ft. Wave Detail: Se 4 Ft At 5 Seconds. Rain. Vsby 1 Nm Or Less, Increasing To 1 To 3 Nm In The Afternoon. |
| Sun Night...Sw Winds 25 To 35 Kt With Gusts Up To 45 Kt. Seas 5 To 8 Ft. Wave Detail: Sw 6 Ft At 5 Seconds And S 4 Ft At 10 Seconds. Rain, Mainly In The Evening. |
| Mon...W Winds 30 To 35 Kt With Gusts Up To 40 Kt. Seas 6 To 8 Ft. Wave Detail: W 6 Ft At 5 Seconds And S 3 Ft At 11 Seconds. |
| Mon Night...W Winds 30 To 35 Kt With Gusts Up To 40 Kt. Seas 5 To 7 Ft. Wave Detail: W 6 Ft At 5 Seconds And Sw 3 Ft At 11 Seconds. Freezing Spray Likely. |
| Tue...W Winds 25 To 30 Kt With Gusts Up To 35 Kt. Seas 4 To 6 Ft. Light Freezing Spray Likely. |
| Tue Night...Nw Winds 20 To 25 Kt. Seas 3 To 5 Ft. |
| Wed...W Winds 15 To 20 Kt. Seas 2 To 3 Ft. |
| Wed Night...Nw Winds Around 10 Kt. Seas 1 Foot Or Less. A Chance Of Snow. Seas Are Reported As Significant Wave Height, Which Is The Average Of The Highest Third Of The Waves. Individual Wave Heights May Be More Than Twice The Significant Wave Height. |
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Area Forecast Discussion National Weather Service Boston/Norton MA 620am EST Sat Feb 15 2025 Synopsis A storm system brings a round of wintry precipitation later today into Sunday, starting as accumulating snow before changing to rain near the coast and a wintry mix inland. Arctic airmass in place for Monday and Tuesday along with strong winds, especially Monday. Cold and dry for the middle of next week, with another chance of snow later in the week with a potential coastal system. Near Term - Until 6pm This Evening Key Messages... * Dry in the morning and early afternoon for most. * Snow arrives in from west to east 4-9 PM. High pressure remains in control through the first half of the day ahead of our next winter system. Some breaks of sun to be had across southern New England in the morning but high clouds streaming overhead on warm advection ahead of this evening's system will thicken and lower through the day leading to mostly overcast skies. At a synoptic scale we see the parent surface low over moving into the midwest ahead of a digging shortwave trough which brings us overspreading snow from west to east this evening. Model soundings show the column saturating between 3 and 5pm in western CT/MA which is when we can expect the snow to begin. Moist advection continues and this snow overspreads the rest of southern New England between 5 and 9 PM. More on this storm below. Short Term - 6pm This Evening Through 6pm Sunday Key Messages... * 2 to 6 inches of snow followed by an icy mix and rain on Sunday. Guidance didn't throw us any big curve balls with the 00Z suite as we see broad WAA (Warm Air Advection - the movement of warm air) driven snowfall continuing over southern New England in the evening and overnight hours. As has been advertised the last several days, a developing mid level jet brings a warm nose of air around 850 mb, moving in from SW to NE between midnight and 7 am. This will cause a changeover to sleet/freezing rain and eventually all rain. One change from 24 hours ago is a delay in the changeover, especially for areas further north as the warmer air gets hung up a bit. This has allowed for slightly increased snow totals over northern MA before the change; still thinking 4 to 6 inches is most likely with isolated amounts up to 7 inches. While most locations will only be dealing with rain during the day on Sunday, the exception will be the high terrain of the Worcester Hills and Berkshires. Given a secondary low forming directly overhead and directing colder NE flow into the region, there is some question as to how quickly that subfreezing air gets scoured out for northern MA in general, as models tend to be too fast. Regardless, it will be a slushy, messy day for travel on Sunday. Given PWATs (Precipitable Waters) in the 1.3" range and a 70-80 kt LLJ overhead, we will easily see 1-1.5 inches of rain on top of any snow that we get. This along with melting snow as temps in southeast MA will reach up into the low to mid 40s. Further north highs in the upper 30s are more likely, outside of those higher elevations. Long Term - Sunday Night Through Friday Key Messages: * Increasing potential for at least advisory level winds for most parts of southern New England Monday with potential for periods near/at warning criteria for the higher elevations. * Below normal temperatures, especially early next week. Windy conditions bring wind chills in as low as -10 Monday night. * Monitoring potential for a coastal storm Weds-Thurs. Details: Sunday Night - Monday Night: A strong cold front pushes through the region Sunday night. Strong westerly subsident flow will kickstart the drying with any remaining showers diminishing. Strong cold air advection will quickly drop temperatures from mid 30s and mid 40s down to low-mid 20s. Residual moisture/water on roads/paths will freeze which could lead to slick spots if left untreated. The ECMWF (European Centre for Medium-Range Weather Forecasts) EFI shows a strong signal for anomalously high winds Monday. With strong Cold Air Advection advection and LLJ overhead, the potential for strong gusts should be well supported. Model soundings indicate a relatively deep, well-mixed boundary layer for points across southern New England on Monday. This will allow transport of the stronger winds aloft down to the surface. Soundings show around 50- 65 kts at the top of the mixed layer which in theory, would support winds nearing high wind criteria in spots IF it fully mixed down. The more likely scenario right now is widespread advisory level winds. Ensemble guidance shows a high chance for gusts 45 mph (at least) across southern New England. However, ensembles do indicate probabilities of 60-90% confined to the higher terrain such as the Worcester Hills and Berkshires for gusts nearing/or at warning criteria (58 mph). With perpendicular flow to terrain of the Berkshires, it is an ideal set-up for downslope enhancement, which is why they (and the immediate east slope) display the highest chances of reaching warning criteria. A High Wind Watch is looking likely for this event. Will likely broad brush the whole region for the Watch and upgrade to Warning/Advisories accordingly as we get closer. Temperatures Monday will be much cooler with highs in the mid 20s to low 30s. However, gusty winds will make it feel much colder with wind chills in the single digits to low teens. The higher gusts gradually decrease Monday evening, but gusts will still play a factor in how chilly it will feel overnight. Temperatures drop into the single digits to teens with wind chills ranging from single digits to as low as -5F. Tuesday and Wednesday: Windy conditions continue Tuesday; however, not as strong as Monday as 850mb winds weaken. The well below normal airmass remains positioned over the region resulting in chilly highs in the 20s. Winds will bring wind chills into the single digits and teens again. The pressure gradient continues to relax into Wednesday trending winds downward. The airmass will begins to moderate as a weak ridge builds in, "warming" highs back into the mid 20s to low 30s. Thursday and Friday: Confidence in the details of the pattern decrease late next week. Overall, ensemble guidance continues to display a potential coastal low forming in the mid-Atlantic then tracking northeastward toward New England. Plenty of model spread among deterministic and ensemble solutions and changes from run to run. As the track varies among solutions/model runs, this will impact where the highest chances of seeing precipitation will be and how much. With a cold pattern in place, this would likely mean snow. Again, we are far out and there is no consistency in the track so we will continue to monitor this as more confidence trends become more evident. Marine Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Moderate confidence. Next storm approaches late today, so winds shift to the SE/S. Could be small craft advisory conditions for southern waters by late day. Better chance on Sunday as the low moves over the region and winds start to increase. Initially they will be out of the east, but as the low moves east, winds will switch to the northwest and start to increase in strength. Gale Watches are in effect for Sunday evening through Monday evening. Freezing spray also becomes a problem late Monday into Tuesday. Outlook /Sunday Night through Wednesday/... Sunday Night: Moderate risk for gale force winds with gusts up to 45 kt. Rough seas up to 16 ft. Rain. Washingtons Birthday: gale force winds with local gusts up to 45 kt. Rough seas up to 16 ft. Freezing spray likely. Monday Night: gale force winds with gusts up to 40 kt. Rough seas up to 15 ft. Freezing spray likely. Tuesday: Strong winds with gusts up to 35 kt. Rough seas up to 12 ft. Freezing spray likely. Tuesday Night: Strong winds with gusts up to 30 kt. Rough seas up to 10 ft. Wednesday: Winds less than 25 kt. Local rough seas. NOAA Boston MA Office: Watches - Warnings - Advisories CT...Winter Weather Advisory from 1pm this afternoon to 7pm EST Sunday for CTZ002>004. High Wind Watch from Sunday evening through Monday evening for CTZ002>004. MA...Winter Weather Advisory from 1pm this afternoon to 7pm EST Sunday for MAZ002>021-026. High Wind Watch from Sunday evening through Monday evening for MAZ002>024-026. RI...Winter Weather Advisory from 1pm this afternoon to 7pm EST Sunday for RIZ001>007. High Wind Watch from Sunday evening through Monday evening for RIZ001>008. Marine Gale Watch from Sunday evening through Monday evening for ANZ230-236. Small Craft Advisory from 1am to 4pm EST Sunday for ANZ231>235-237-250-251-254>256. Gale Watch from Sunday afternoon through Tuesday afternoon for ANZ231>235-237-250-251-254>256. |
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