Cape Cod Bay Marine Forecast
| Tonight...Ne Winds 5 To 10 Kt, Diminishing To Around 5 Kt After Midnight. Seas Around 2 Ft. Areas Of Fog. Numerous Showers, Mainly This Evening. Vsby 1 To 3 Nm, Decreasing To 1 Nm Or Less After Midnight. |
| Fri...N Winds Around 5 Kt, Becoming S In The Afternoon. Seas 1 Foot Or Less. Areas Of Fog. Vsby 1 Nm Or Less. |
| Fri Night...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt, Diminishing To 5 To 10 Kt After Midnight. Seas Around 2 Ft. |
| Sat...Sw Winds 5 To 10 Kt. Seas Around 2 Ft. |
| Sat Night...Sw Winds 5 To 10 Kt. Seas Around 2 Ft. |
| Sun...Sw Winds 5 To 10 Kt. Gusts Up To 20 Kt In The Afternoon. Seas Around 2 Ft. |
| Sun Night...W Winds 5 To 10 Kt. Gusts Up To 20 Kt In The Evening. Seas Around 2 Ft. A Chance Of Showers And Tstms. |
| Mon...N Winds Around 5 Kt. Seas Around 2 Ft. A Chance Of Showers. |
| Mon Night...Sw Winds Around 5 Kt. Seas Around 2 Ft. A Chance Of Showers. |
| Tue...Ne Winds Around 5 Kt. Seas Around 2 Ft. A Chance Of Showers. |
| Tue Night...N Winds Around 5 Kt. Seas Around 2 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 722pm EDT Thu July 18 2019 Synopsis: Showers, mainly along the south coast and Cape Cod will come to an end overnight. Sunday and warmth returns Friday as some of the hottest weather we've had in years starts moving into the region. Dangerous heat and humidity are on tap this weekend with heat index values approaching or perhaps exceeding 110 degrees. Dry weather should dominate this weekend, but a few thunderstorms are possible later Sunday and Sunday night as a cold front crosses the region. Much cooler and less humid follows for the next work week, especially on Monday with the potential for some showers. Near Term - Until 6am Friday Morning 720 pm update... Weak wave of low pressure coupled with Pwats of 2+ inches continues to generate bands of showers south of the MA turnpike. Areal coverage and intensity was greatest near the south coasts of RI & MA, where there were some heavy downpours. This is where the highest Pwat/strongest forcing exists. As previous forecast mentioned, we should see this activity wind down late this evening and especially after midnight. This in response to the greatest forcing shifting east of the region. Otherwise, expect fog across the Cape and Islands and also impact portions of RI/SE MA. A bit muggy in many areas with dewpoints in the 60s, though slightly drier across northeast MA. Overnight lows will generally be in the 60s Short Term - 6am Friday Morning Through Friday Night As of 420 PM... Not much going on tomorrow. Flow turns back to the west/southwest and starts to advect in some warmer air and push the moisture out. That will bring back partly to mostly sunny skies. With 850mb temperatures up around 19C, that suggest the potential for surface highs reaching 33-34C (92-94F). With some clouds around, we may just fall short of that potential, but upper 80s to lower 90s is a good bet. Right along the coast, especially eastern MA, there will be a sea breeze to drop temperatures a few degrees. Models suggest convection developing during the day out across NY state. Could be a rogue shower that makes it into the far western part of the forecast area Friday evening, but at this point I've kept the Probability of Precipitation out there less than 15%. Friday night should be quiet, though with increasing dewpoints, there should be areas of low clouds/fog that develop off the south coast through the Cape and Islands. During the day Friday, heat index values will approach the mid 90s in most areas, with 100F or so in the Connecticut river value. This is due to the combo of the hot temperatures and dewpoints rising to near 70. "By the book", this meets only Heat Advisory thresholds. However since the heat will continue to build for the weekend, we've decided to issue an Excessive Heat Warning that becomes effective Friday and continues into Sunday, rather than try to split hairs and separate out Friday vs Saturday and Sunday .LONG TERM /SATURDAY THROUGH THURSDAY/. .. Highlights... * Dangerous Heat/Humidity This Weekend: Heat Indices May Approach Or Even Exceed 110 Degrees * A few thunderstorms are possible Sunday afternoon/night as a cold front crosses the region * Much cooler/less humid for the next work week especially Monday with the potential for some showers. Details... This Weekend... Strong upper level ridging across the mid-Atlantic/southeast states will pump a highly anomalous hot/humid airmass into southern New England. 850T around +22C will support and westerly flow will support near record high temperatures this weekend. In fact...one of the top CIPS analogs for this weekend is July 22nd, 2011 which is the last time many of our sites reached the century mark. Some guidance may be a few degrees too cool given its tendency to trend towards climatology. Overall, expect high temperatures to generally be in the 96 to 102 degree range away from localized marine influences along the coast. More important than the actual temperatures will be the heat index values. We have an EML in place on Sat, which tends to keep the surface dewpoints from mixing out. On Sunday, a cold front will be dropping south and dewpoints may pool for a time along the boundary. Given the above expect dewpoints mainly in the 70s over the weekend. The expected high temperatures/dewpoints will likely result in heat index values approaching or even exceeding 110 degrees during peak afternoon heating this weekend. Therefore, Excessive Heat Warnings are in effect this weekend for basically the entire region. Heat Advisories have been issued for Cape Cod/Marthas Vineyard. Much of the weekend will feature dry weather, but there will be a couple things will need to watch. An elevated mixed layer in place Sat into early Sunday along with very high instability for this part of the country. However, it looks like we probably will be capped keeping us dry Sat into early Sun. That being said given the extreme instability and an EML in place, there is a very small risk that a complex of thunderstorms develop and cross our region. While this appears to be a rather low risk at this time, if it were to happen it would have some high end potential given the environment. A better chance exists for a few showers/thunderstorms later Sunday into Sunday night with the cold front, but low confidence on areal coverage. Monday through Thursday... A much cooler/less humid airmass works into the region behind the cold front, especially Monday and Tuesday. A wave of low pressure developing on the front to our south may result in some showers/isolated t-storms Monday which may linger into part of Tue, especially across southeast New England. This will also help to keep temperatures much cooler then what we have experienced over the weekend. Mainly dry weather should allow temps to warm up some by next Wed/Thu, but readings should not be too far from typical late July temperatures .AVIATION /23Z THURSDAY THROUGH TUESDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/...Moderate confidence. MVFR to IFR conditions will prevail overnight, despite the bulk of the showers south of the MA Pike ending by or not too long after midnight. The lower of the cigs/visibilities will be across the Cape/Islands, where the might be some LIFR conditions especially across Nantucket. Conditions will improve to VFR across most of the region by mid morning as the clouds finally dissipate. Winds will turn southwest, but onshore sea breezes are expected to develop and remain right along the coast from mid morning to mid afternoon. Southwest flow will strengthen enough by late afternoon that it should overcome the sea breeze. Low clouds and areas of fog are expected to develop Friday evening across the waters near and south of Cape Cod and last all night. That will result in IFR to LIFR conditions. KBOS Terminal...Moderate confidence in TAF. KBDL Terminal...Moderate confidence in TAF. Outlook /Saturday through Tuesday/...High confidence. Saturday: VFR. Breezy. Saturday Night: VFR. Sunday through Sunday Night: VFR. Breezy. Chance SHRA, chance TSRA. Monday: Mainly VFR, with local MVFR possible. Chance SHRA, isolated TSRA. Monday Night: VFR. Chance SHRA, isolated TSRA. Tuesday: VFR. Slight chance SHRA, isolated TSRA Marine Discussion Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Friday Night/...High confidence. Showers and areas of fog, especially this evening and overnight primarily from Long Island Sound to Cape Cod and points south and east. Primarily northeast winds, perhaps gusting to 20 knots this evening. Winds will turn southwest during the day Friday and continue to Friday night, running about 15 knots. Seas generally 1 to 3 feet, though 4 foot seas well south of Cape Cod. Late Friday and Friday night, expecting areas of fog to develop along and off of the south coast and over to the Cape and Islands. Visibilities could be reduced to less than 1 mile. Outlook /Saturday through Tuesday/...High confidence. Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Patchy fog. Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Patchy fog. Local visibility 1 to 3 nm. Sunday through Sunday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, chance of thunderstorms. Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, isolated thunderstorms. Monday Night: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms. Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers, isolated thunderstorms. Climate Record highest min temps for Saturday July 20: BOS: 75 in 2016 BDL: 73 in 1975 PVD: 77 in 1983 ORH: 72 in 2013 Record highs for Saturday July 20: BOS: 99 in 1991 BDL: 100 in 1991 PVD: 101 in 1991 ORH: 92 in 1901 Record highest min temps for Sunday July 21: BOS: 81 in 1991 BDL: 74 in 1977 PVD: 77 in 1980 ORH: 73 in 1991 Record highest max temps for Sunday July 21 BOS: 102 in 1977 BDL: 101 in 1991 PVD: 102 in 1991 ORH: 95 in 1926 Last Occurrence of 100F or higher temperatures BOS: 7/22/2011 (103F) BDL: 7/18/2012 (100F) PVD: 7/22/2011 (101F) ORH: 7/4/1911 (102F) NOAA Boston MA Office: Watches - Warnings - Advisories CT...Excessive Heat Warning from noon Friday to 8pm EDT Sunday for CTZ002>004. MA...Excessive Heat Warning from noon Friday to 8pm EDT Sunday for MAZ002>021-026. Heat Advisory from noon Friday to 8pm EDT Sunday for MAZ022- 023. RI...Excessive Heat Warning from noon Friday to 8pm EDT Sunday for RIZ001>007. MARINE...None |
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