Provincetown MA to Chatham MA to Nantucket MA out 20 NM Marine Forecast
| This Afternoon...W Winds Around 10 Kt. Seas 3 To 4 Ft. |
| Tonight...Nw Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Evening. Seas 3 To 4 Ft. |
| Fri...Nw Winds 5 To 10 Kt, Becoming W In The Afternoon. Seas 2 To 3 Ft. |
| Fri Night...Sw Winds Around 5 Kt. Seas Around 2 Ft. |
| Sat And Sat Night...S Winds 5 To 10 Kt. Seas Around 2 Ft. |
| Sun...S Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 2 To 4 Ft. A Chance Of Showers. |
| Sun Night...S Winds 25 To 30 Kt With Gusts Up To 50 Kt. Seas 6 To 9 Ft. Showers. |
| Mon...Sw Winds 25 To 30 Kt With Gusts Up To 45 Kt. Seas 8 To 13 Ft, Except 12 To 15 Ft S And E Of Nantucket. Showers. |
| Mon Night...W Winds 20 To 25 Kt With Gusts Up To 35 Kt. Seas 7 To 10 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. |
| Area Forecast Discussion National Weather Service Boston/Norton MA 408pm EST Fri Dec 8 2023 Synopsis High pressure over New England Friday night drifts offshore Saturday, providing dry, tranquil weather to the region. A strong frontal system has the potential to bring a period of heavy rain, strong southerly winds to the entire region, with possible coastal flooding along the south coast. All of this occurring from late Sunday into Monday morning. A few snow showers across northwest Massachusetts are possible Monday afternoon and evening as the system departs. Otherwise turning drier Monday evening with a brief shot of colder air, but temperatures look to rebound back closer to seasonable levels Tuesday through Thursday. Near Term - Until 6am Saturday Morning 315 PM Tonight... * Dry & seasonably cold tonight * Low prob (10-20%) of patchy frost/black ice overnight Deep layer ridge provides dry weather tonight. Surface ridge promotes light winds and with dew pts in the 20s to lower 30s, along with mostly clear to partly cloudy conditions, some radiational cooling will allow min temps to fall into the upper 20s and lower 30s. Mid 30s for the urban areas. Given these conditions, we derived overnight mins from the colder MOS guidance. These temps are seasonably cold for early Dec. The only wrinkle to the forecast is later tonight, as the high drifts offshore, light S-SE flow develops and allows dew pts to slowly rise into the low 30s across CT/RI and eastern coastal MA. Given recent nighttime lows have been in the teens and 20s, dew pts rising at or above freezing and streaming over subfreezing ground temps, may yield patchy frost/black ice on secondary roads, parking lots, sidewalks, etc. Not confident enough to issue a SPS, but something we will be watching this evening and overnight. Short Term - 6am Saturday Morning Through Saturday Night 315 PM Saturday... * Mainly dry and milder Saturday Warm front approaches from the southwest. Any morning sunshine will give way to mostly cloudy conditions by afternoon. Warm sector airmass bleeds into RI and southeast MA with dew pts into the mid 40s, and highs in the mid 50s. However, the true warm sector airmass holds off until Sunday. Not expecting any precipitation with the warm front Saturday, as model soundings indicate lots of mid level dry air, but can't rule out a few sprinkles especially across the interior. Otherwise, it's a dry Saturday with above normal temps. SSE winds 5- 10 mph across the interior, 10-15 mph along the coast. Saturday night... * Mainly dry and milder * Areas of fog possible Warm sector airmass advects northward with dew pts in the 40s across CT/RI and eastern MA. This combined with boundary layer cooling should yield areas of fog. Could have some patchy drizzle, but otherwise it's a mainly dry night. Lows in the low 40s, mid to upper 30s across interior CT, northwest RI into central-western MA. Light south winds, except 10-15 mph along the south coast and Islands. Long Term - Sunday Through Friday Key Points... * Increasing chance of rain through the day on Sunday with increasingly gusty winds. * The bulk of a strong storm system will arrive overnight Sunday and Monday morning bringing widespread rain, strong (potentially damaging) winds, and the possibility of coastal flooding on the south coast. * Quiet, mostly dry, and colder through the rest of the week. Much of the day Sunday will be a transition from the quiet and dry Saturday to the very wet and windy period Sunday night and early Monday. Southern New England will be placed between an exiting ridge over the west Atlantic and a deep trough digging into the Great Lakes. This funnels abnormally warm and moist air into the region leading to a very mild and breezy day with highs reaching the low 60s! The previously mentioned deep trough then swings through Sunday night into Monday bringing unsettled weather including widespread rain with flooding potential, strong winds, and coastal flooding. Details on that system are below. The dry slot punches into the region quickly behind the front (by mid day on Monday) bringing precipitation to a quick end save for some light, orographically enhanced snow showers over the Berkshires on Monday. Beyond Monday we have a quiet set up for the rest of the work week with a series of high pressures just to our south interrupted by one moisture started frontal system around Wednesday which should remain dry for the vast majority of the area with highs in the 40s each day. The focus of the extended forecast period continues to be late Sunday and early Monday when a slightly negatively tilted mid level trough and strengthening surface frontal system will cross the region accompanied by highly anomalous moisture and winds, both of which are in the 99.5 percentile compared to climatology. Firstly, the threat for excessive rainfall potentially leading to flooding issues has increased in the last 24 hours, and thus a Flood Watch has been issued for CT and western/central MA. This is where the strongest dynamics (divergence from 145 kt upper jet, convergence ahead of the low level jet, amongst other things) combine with PWATs (Precipitable Waters) over 1.25 inches and have the potential to lead to rainfall amounts of 3+ inches in some locations (more widespread 1-2+ inches). If you believe the GFS (Global Forecast System) ensemble there is even a 20-30% chance of 4+ inches! If these rainfall amounts were to materialize there is a chance we could see river flooding in addition to the expected urban and poor drainage flooding issues. The MMEFS is now showing a 30% chance of points along the CT River reaching moderate flood stage (up from minor yesterday). WPC has introduced a Slight Risk of excessive rainfall for areas where we currently have the Flood Watch out. An additional factor is the chance of some limited elevated instability in the warm sector which could enhance rainfall further east in any convection. Another issue will be potential for damaging winds. Confidence for strong winds has only increased in the last 24 hours, and a High Wind Watch has been issued for Cape Cod and the islands as well as a Storm Watch for the waters. Low level jet dynamics remain largely unchanged, with winds at 925 mb ranging from ~50 kts over central MA to 75-85kts over Cape Cod. There will be the typical fight between the jet screaming just a few thousand feet above the surface and a pretty robust temperature inversion just below it. BUFKIT soundings indicate that the bulk of the jet remains aloft which is why a High Wind Watch has been issued which can later be either replaced with a High Wind Warning or a Wind Advisory depending on the higher resolution guidance as we get closer to the event. For what it's worth, the EPS ensemble continues to advertise a 80-90% chance of gusts 58mph+ on the outer Cape and Nantucket. Coastal flooding is the final hazard that will be possible with this system, focused on the Monday morning high tide along the south coast, namely Narragansett Bay. If the stronger winds materialize (mix down) they could lead to as much as 3 feet of surge. Then, if that surge coincides with high tide (6:20 am in Providence) it could lead to coastal flooding. At the Fox Point forecast location the mean of flood guidance takes it to around 7 ft (minor flood) but a worse case scenario takes it to near 9 ft (moderate flood). Too soon to know with any certainty but both are in the realm of possibility with this system. Post frontal winds will then kick up during the day on Monday with winds gusting 35-45 mph out of the west. Marine Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 315 PM High Confidence through Saturday night. Tonight...light & variable winds this evening becoming S-SE and light overnight. Dry weather and good vsby as high pressure drifts just offshore. Saturday...high pressure drifts farther offshore with a weak warm front moving across New England. Dry weather and good vsby prevail, along with light S-SE winds. Saturday night...warm front north of the MA/RI waters, with winds shifting from SSE to SSW overnight. This likely leads to areas of fog with reduced vsby. Mainly dry but can't rule out patchy drizzle at times. Outlook /Sunday through Wednesday/... Sunday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of seas approaching 5 ft. Chance of rain, patchy fog. Local visibility 1 to 3 nm. Sunday Night: Low risk for storm force winds with gusts up to 60 kt. Rough seas up to 14 ft. Rain, patchy fog. Visibility 1 to 3 nm. Monday: Low risk for storm force winds with gusts up to 60 kt. Rough seas up to 16 ft. Rain, patchy fog. Areas of visibility 1 to 3 nm. Monday Night: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 14 ft. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. NOAA Boston MA Office: Watches - Warnings - Advisories CT...Flood Watch from Sunday afternoon through Monday evening for CTZ002>004. MA...Flood Watch from Sunday afternoon through Monday evening for MAZ002>004-008>012-026. High Wind Watch from late Sunday night through Monday afternoon for MAZ022>024. RI...High Wind Watch from late Sunday night through Monday afternoon for RIZ008. Coastal Flood Watch from late Sunday night through Monday morning for RIZ002-004>007. Marine Storm Watch from late Sunday night through Monday morning for ANZ230-236. Storm Watch from late Sunday night through Monday afternoon for ANZ231>235-237-250-251-254>256. |
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