Coastal Waters out 25 NM South of Marthas Vineyard and Nantucket Marine Forecast
|Tonight...Sw Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas Around 7 Ft. Showers Likely With A Slight Chance Of Tstms After Midnight With Vsby 1 To 3 Nm.|
|Tue...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas Around 6 Ft. A Chance Of Showers In The Morning With Vsby 1 To 3 Nm.|
|Tue Night...Nw Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Evening. Seas Around 6 Ft.|
|Wed...Nw Winds 5 To 10 Kt. Seas Around 6 Ft.|
|Wed Night...Sw Winds 5 To 10 Kt. Seas Around 5 Ft.|
|Thu...Sw Winds 10 To 15 Kt, Increasing To 15 To 20 Kt In The Afternoon. Gusts Up To 25 Kt. Seas Around 5 Ft.|
|Thu Night...Sw Winds 10 To 15 Kt, Becoming Nw After Midnight. Gusts Up To 25 Kt. Seas Around 5 Ft. A Chance Of Showers After Midnight.|
|Fri...Nw Winds 5 To 10 Kt. Seas 3 To 4 Ft.|
|Fri Night...S Winds 5 To 10 Kt. Seas 3 To 4 Ft.|
|Sat...Sw Winds 10 To 15 Kt. Seas Around 5 Ft.|
|Sat Night...W Winds 10 To 15 Kt. Seas Around 5 Ft. Winds And Seas Higher In And Near Tstms. 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
342pm EDT Monday September 23 2019
Chance of showers overnight ahead of a cold front. A few scattered showers Tuesday, then high pressure settles in Wednesday with mild days and cool nights. Swells from Jerry will cause increased rip current risk along the coast, especially Monday through Wednesday. Another front approaches Thursday into Thursday evening, with dry conditions returning Friday.
Near Term - Until 6am Tuesday Morning
An unusually warm day underway in southern New England...many locations breaking the 90 degree mark! Boston has hit 92F as of this hour while Bradley has hit 92F. Boston isn't in danger of breaking the record (96F) but Bradley is one degree shy of tying the record of 93F. Compare this to the normal highs of 70(BOS) and 73(BDL) and we're experiencing quite the resurgence of summer (on the first day of Fall, of all days). This comes on breezy SW winds ahead of an approaching cold front. Gusty winds continue to mix down to the surface, mainly on Cape Cod and along the south shore of MA/RI. SW winds are gusting 25-35 mph. These will continue into the evening before tapering off overnight.
Bigger picture we see an approaching shortwave trough and attendant cold front which will bring some showers and thunderstorms late afternoon through the overnight hours. Surface observations and satellite imagery place the cold front over western NY at this hour, slowly moving east. Ahead of the front moisture advection continues, bringing in PWATs (Precipitable Waters) near 2" over eastern and especially southeastern MA, and surface dewpoints in the upper 60s. The increased moisture and surface heating is contributing to marginal instability (CAPE values ~500 J/kg) with supportive wind profiles, enough to expect some embedded thunderstorms through much of evening and overnight hours. However, the best forcing remains to our west during peak instability, so not expecting widespread strong/severe thunderstorms. Some locally heavy downpours are possible, especially over southeast MA after midnight, when we see the alignment of the 35kt LLJ and highest moisture plume. Some in this area could see a half inch or so beneath any heavy showers. The cold front reaches western MA/CT early this evening, making its way off the southeast coast by early-mid morning Tuesday, rain coming to an end behind.
Short Term - 6am Tuesday Morning Through Tuesday Night
Tuesday features cooler weather and an improving trend. We may see some showers lingering over the Cape and islands Tuesday morning as the cold front exits, but should come to an end by late morning. Thereafter, showers of a more pop-up, scattered nature return beneath a settling closed low and cold pool(a region of relatively cold air) aloft as that trough axis crosses SNE during the afternoon. Best chance for seeing some showers will be over northern and western MA. A much cooler and drier post frontal air mass is in place, feeling a bit more Fall- like with high temperatures over 10 degrees cooler than today (in the 70s) and dewpoints in the 50s. Post frontal winds will be out of the west with potential to mix down some breezy winds 15-20kts along the south coast. Clouds and rain chances decreasing as the day progresses. This as the low moves out and heigheights begin to rise under mid level ridging. Low temps too will drop ~10 degrees from the night previous, in to the 50s...upper 40s in the higher terrain of NW MA.
Long Term - Wednesday Through Monday
*/ Highlights... - Low chance of showers late Thursday into Thursday evening - Warming up considerably by the weekend into early next week - Overall temperatures above average, and a very dry forecast
*/ Overview... Mild, dry pattern. Active tropics assisted by a phase 1 MJO that are drawn N into the mid-latitude flow yielding chaos. Post-tropical in becoming baroclinic, contribution of latent heat release, warmth is introduced poleward as the longwave pattern becomes amplified at a point where initially +EPO / +WPO cascades energy E along a strong jet eastward into the CONUS from prevailing low pressure over the N Pacific. Rossby waves manifesting, greater transfers between the N pole and equator, blocks emerging over AK and across Greenland, the pattern is slowed briefly by the beginning of October with momentum transfers (i.e., wind) and subsequent longwave pattern undulations. The CONUS trough.ridge by next weekend into early the following week, near climatological-record percentiles, +1-2 standard deviation over the MS/OH Valley, biggest question is how far N/E the ridge builds into New England. Ensemble spread noted in a multitude of height and temperature fields yet notably the high-skill deterministic solution exhibits tendency towards the high/warm-end of the member guidance. Forecast spread mainly in part due to longwave pattern uncertainty, the N Atlantic block in particular whether if further W putting the NE CONUS beneath NW flow. Quite possible we could see upper 80 to low 90 highs with very little if any rainfall. Max temperatures that would be record-breaking. Coinciding with CPC earlier and now latest 6-10 day forecasts. Not a good setup when we're already experiencing "abnormally-dry" conditions in spots across New England. Indications further into October that Rossby waves pinch-off and a flat-pattern returns ushering in near-seasonable conditions per ensemble, however considerable spread remains. For now increasing confidence that as September ends and October begins it will still feel like Summer as opposed to Autumn. Keeping a mostly dry forecast. Leaning towards warmer forecast guidance. Humidity will also make a return.
*/ Discussion... Through Thursday night... Quick note on the details. Rain chances late Thursday into Thursday night. However heigheights rising, indications of a flat N-stream wave, perhaps some mid-level subsidence. Outcomes along a sweeping cold front being squashed out prior to arrival into S New England with synoptics shunted N and lack of support to maintaining convection, if any. Low chance Probability of Precipitation sneaking into N/W MA and CT towards late afternoon into evening.
Friday onward... It's after a brief period of high pressure Friday pushing S/E off- shore that return S flow through the weekend beneath rising heigheights and low-mid level SW warm advection that we see temperatures rise, potentially record-breaking, into the 1st of October. This along with dewpoints into the 60s, it will feel like Summer rather than Autumn.
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.
Short Term /through Tuesday Night/...High confidence.
SW winds will increase to 20-25 kt with a few gusts to 30 kt not out of the question this afternoon into the evening, especially along the near shore of Cape Cod and the Islands. This preceding a cold front which will sweep through late tonight into Tuesday ahead of which showers are forecast some of which will contain locally heavy downpours. Visibility could fall as low as 1 to 2 miles.
SMALL CRAFT ADVISORIES are in effect for most waters. Increasing swell from Tropical Storm Jerry today into Wednesday.
Outlook /Wednesday through Saturday/...Moderate confidence.
Wednesday: Winds less than 25 kt. Local rough seas.
Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft.
Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Slight chance of rain showers.
Thursday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.
Friday through Friday Night: Winds less than 25 kt. Seas locally approaching 5 ft.
Saturday: Winds less than 25 kt. Seas up to 5 ft.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...High Rip Current Risk through Wednesday morning for MAZ023-024. RI...High Rip Current Risk through Wednesday morning for RIZ008.
Small Craft Advisory until 6am EDT Tuesday for ANZ232>234-250. Small Craft Advisory until 10pm EDT this evening for ANZ231. Small Craft Advisory until 2am EDT Tuesday for ANZ236. Small Craft Advisory until 8am EDT Wednesday for ANZ235-237- 254>256.