Nantucket Sound Marine Forecast
| This Afternoon...S Winds 20 To 25 Kt With Gusts Up To 30 Kt. Seas 4 To 5 Ft. Wave Detail: S 5 Ft At 5 Seconds And Se 1 Foot At 9 Seconds. Patchy Fog. Rain. Vsby 1 To 3 Nm, Decreasing To 1 Nm Or Less. |
| Tonight...Sw Winds 20 To 25 Kt, Becoming W 15 To 20 Kt After Midnight. Gusts Up To 30 Kt. Seas 3 To 5 Ft. Wave Detail: Sw 5 Ft At 5 Seconds And Se 2 Ft At 8 Seconds. Patchy Fog. A Chance Of Showers. Vsby 1 Nm Or Less. |
| Sun...W Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 3 To 4 Ft. Wave Detail: W 3 Ft At 4 Seconds And Se 2 Ft At 8 Seconds. |
| Sun Night...Nw Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 2 To 3 Ft. Wave Detail: W 3 Ft At 4 Seconds And Se 1 Foot At 8 Seconds. |
| Mon...Nw Winds 10 To 15 Kt With Gusts Up To 20 Kt, Diminishing To 5 To 10 Kt In The Afternoon. Seas 2 To 3 Ft. Wave Detail: Nw 2 Ft At 4 Seconds And E 1 Foot At 8 Seconds. |
| Mon Night...W Winds 5 To 10 Kt. Seas 1 Foot Or Less. Wave Detail: W 1 Foot At 3 Seconds And E 1 Foot At 8 Seconds. |
| Tue...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas Around 2 Ft. |
| Tue Night Through Wed Night...Nw Winds 20 To 25 Kt. Seas 2 To 4 Ft. 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 709am EDT Sat April 26 2025 Synopsis Periods of rain with embedded downpours continue through at least the first part of the day today. A few thunderstorms are possible for western areas but severe weather is not likely. A cold front then ushers in a much cooler airmass tonight. Cloudy, cool, and blustery conditions on Sunday. High pressure returns with dry conditions for Monday and Tuesday, along with mild to warm temperatures. A cold front moves across the region on Wednesday with a few showers possible late Tuesday night into early Wednesday morning. Seasonable temperatures to end the week with the next chance for rain by Friday. Near Term - Through Tonight Key Messages... * Rain moves offshore, but eastern MA and RI may struggle to reach the lower 60s with overcast skies persisting. * A few t-storms possible west of Worcester this afternoon, but severe weather is not likely. * Cooler and breezy overnight. Isentropic forcing continues to produce widespread light rain showers over southern New England early this morning, though the heavier precipitation remains over eastern PA/NY. This is where, not coincidentally, mesoanalysis indicates the core of a 40+ kt 850 mb jet. As this jet (and associated forcing) shift east the heavier bands of rain will move through SNE generally between 7am and 5 PM. Once all is said and done most locations will have gotten a good soaking, between a 0.25" and 1.25" with the Quantitative Precipitation Forecast bullseye over western/interior SNE; ensemble guidance paints a 60-70% chance of at or above 1" in the Worcester Hills and 80-95% chance in the Berkshires. Some dry mid/upper level air works in by afternoon as the core of the jet moves off, so more breaks in the rain are expected, especially west, before a final round of showers and thunderstorms accompanies the cold front late afternoon/evening. Guidance continues to be pessimistic on breaks of sun during daylight hours (needed to increase the modest instability available, up to 500 J/kg SBCAPE) so severe weather is not expected. However, some thunderstorms are possible, mainly west of Worcester. Tonight the cold front ushers in a much cooler and drier airmass as dewpoints drop from 60F to the 30s by 5am. It will become breezy, however, as Cold Air Advection promotes deeper mixing. Low temps will be 10+ degrees cooler than the previous night, in the 40s. Short Term - Sunday Key Messages... * Cool and blustery conditions on Sunday Sunday will be drier, but still cloudy thanks to the -23C 500mb cold pool and cyclonic flow aloft with the lingering trough. Strong gradient winds will also be increasing through the day as Cold Air Advection promotes mixing down of a potent 45-50 kt 850 mb LLJ. A marginal Advisory may be needed for a portion of interior SNE. Most locations will be dry on Sunday, but a few instability showers are possible and some orographically forced precipitation may linger over the Berkshires for part of the day. Long Term - Sunday Night Through Friday Key Messages: * Much warmer with dry conditions Monday and Tuesday. A few showers are possible Tuesday night into Wednesday morning ahead of an approaching cold front. * Near seasonable temperatures Thursday and Friday. While Thursday is dry, rain chances return for Friday. Sunday Night: Gusty NNW winds continues for part of the night, but the duration of the wind will largely depends how quickly we cool the boundary layer and lose the mixing. Guidance does show a robust 850mb jet with wind speeds aloft 50 to 60 knots, with the 00z NAM being the most robust with max wind speeds ~70 knots. While I do not think will mix up to 850mb, BUFKIT soundings mix upward 900mb which have winds close to 40 knots. For now, think wind gusts 30 to 40 MPH through midnight is a good assessment, with potentially near advisory level gusts 46+ MPH for the Berkshire high terrain. Otherwise, the mid-level low moves out to the Gulf of Maine and drier air advects into southern New England, will have clearing skies and lows in the 40s and possible upper 30s for those at or above 1,000 feet. Monday through Wednesday: After a gloomy weekend, nicer weather for Monday and Tuesday with high pressure and mid-level ridging. Monday night there is the potential for cooler temperatures because of radiational cooling, did blend in the cooler CONSMOS guidance which gave lows are in the upper 30s to low 40s across interior southern and known areas that radiate well along the I-495 corridor and Martha's Vineyard, elsewhere middle and upper 40s. The axis of the ridge shifts east Tuesday evening and a northern stream trough and cold front approaches from the west. Temperatures rebound nicely both these days, low 70s for Monday, then mid to upper 70s on Tuesday. SW flow on Tuesday ushers in higher PWATs, ahead of an approaching mid-level trough and surface cold front. While a few showers Tuesday night into Wednesday morning are possible, it looks the best forcing with the cold front comes too late as the best moisture exits east of New England before the cold front arrives. The timing of the cold front will dictate the high temperatures for Wednesday, thinking it could be a slow moving front, which may allow the coast plain to warm up nicely into the low and middle 70s, while those interior locations only reach the upper 60s to low 70s. Cold front moves across the region and brings a shot of colder air across all of southern New England, widespread upper 30s to low 40s. Thursday and Friday: Drier Thursday with weak high pressure briefly in control, but is quickly followed by unsettled weather and the return of rain on Friday. Temperatures late week are seasonable in the low and middle 60s. Marine Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. Southerly flow continues to strengthen into the SCA (Small Craft Advisory) range for today, with winds 25-30 kt and seas 4-7 ft. Rain and reduced visibilities expected until a sharp frontal passage this evening, bringing a windshift to W/NW around 15-25 kt. Sunday NW winds will gust 20 to 25 kts with seas of 3-6 ft. Outlook /Sunday Night through Wednesday/... Sunday Night: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Local rough seas. Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday Night: Winds less than 25 kt. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas locally approaching 5 ft. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain showers, isolated thunderstorms. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Local rough seas. NOAA Boston MA Office: Watches - Warnings - Advisories CT...None. MA...None. RI...None. Marine Small Craft Advisory until 8am EDT Sunday for ANZ231>237. Small Craft Advisory until 2am EDT Monday for ANZ250-254>256. |
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