Marine Weather and Tide Forecast for Siasconset, MA
May 21, 2024 3:08 AM EDT (07:08 UTC) Change Location
 | Sunrise 5:18 AM Sunset 8:05 PM Moonrise 6:15 PM Moonset 3:59 AM |
ANZ915 Between 1000fm And 38.5 N West Of 69 W- 1037 Pm Edt Mon May 20 2024
Tonight - NE winds 5 to 15 kt, becoming 5 to 10 kt. Seas 4 to 6 ft.
Tue - NE winds less than 10 kt, becoming variable. Seas 4 to 5 ft.
Tue night - SW winds less than 10 kt. Seas 3 to 5 ft.
Wed - SW winds 5 to 10 kt. Seas 3 to 4 ft.
Wed night - SW winds 10 to 15 kt. Seas 3 to 4 ft.
Thu - SW winds 10 to 15 kt. Seas 3 to 4 ft.
Thu night - SW winds 10 to 15 kt. Seas 3 to 4 ft.
Fri - SW winds 10 to 15 kt, becoming W to sw 5 to 10 kt. Seas 3 to 4 ft.
Fri night - W to sw winds 5 to 10 kt, becoming W 5 to 15 kt. Seas 3 to 4 ft.
Sat - N to ne winds less than 10 kt, becoming e. Seas 3 to 4 ft.
Sat night - E winds 5 to 10 kt. Seas 3 to 4 ft.
ANZ900 Georges Bank Between 68w And The Hague Line- 1032 Pm Edt Mon May 20 2024
Tonight - E to ne winds 5 to 15 kt, becoming ne. Seas 5 to 6 ft.
Tue - NE winds less than 10 kt, becoming variable. Seas 4 to 5 ft.
Tue night - SW winds 5 to 15 kt. Seas 3 to 4 ft. Areas of fog with vsby 1 nm or less.
Wed - SW winds 10 to 20 kt. Seas 3 to 5 ft. Areas of fog with vsby 1 nm or less.
Wed night - SW winds 10 to 20 kt. Seas 3 to 5 ft.
Thu - SW winds 15 to 20 kt. Seas 3 to 5 ft.
Thu night - SW winds 15 to 20 kt, diminishing to 10 to 15 kt. Seas 4 to 5 ft.
Fri - SW winds 10 to 15 kt. Seas 3 to 5 ft.
Fri night - SW winds 10 to 15 kt, becoming w. Seas 3 to 4 ft.
Sat - N to nw winds 5 to 10 kt. Seas 3 to 4 ft.
Sat night - N winds less than 10 kt, becoming ne. Seas 3 to 4 ft.
FXUS61 KBOX 210256 AFDBOX
Area Forecast Discussion National Weather Service Boston/Norton MA 1056 PM EDT Mon May 20 2024
SYNOPSIS
A ridge of high pressure sinks to our south tonight, setting the stage for summerlike warmth Tuesday through Thursday at least away from the immediate south coast. Generally dry weather is expected Tuesday and Wednesday, but an approaching cold front may bring a round of scattered showers and thunderstorms Thursday afternoon and evening. This will usher in more seasonable but generally pleasant weather for the Holiday weekend.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
Main forecast challenge overnight is the northward extent of stratus and fog. As of this writing, this stratus had just begun to reach the South Shore, as well as the South Coast of MA. Much of the Cape and islands were already blanketed as well.
Still have high confidence in stratus overspreading much of RI and southeast MA. However, have lower confidence in the timing.
Will be monitoring that overnight, as it will have implications for temperatures during the day tomorrow.
Minor tweaks to bring the forecast back in line with observed trends.
315 PM Update...
* Low Clouds and fog develop tonight with lows upper 40s/50s * Fog may become dense across parts of RI/SE MA tonight
A ridge of high pressure across southern New England gradually shifts to our southwest tonight, but remains in control of our weather. Light southerly flow and a cooling boundary layer will allow areas of low clouds and fog to redevelop from south to north after sunset. Give that the surface winds will be light/calm, some of the fog may become locally dense across RI/SE MA given 50+ dewpoints. It is possible later shifts may need to consider a Dense Fog Advisory for a portion of this region.
Overnight low temps should bottom out mainly in the lower to middle 50s, but may see readings drop to between 45 and 50 towards the Cape and Islands given lower dewpoints in that region.
SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/
Key Points...
* Summerlike Warmth Tue away from the south coast * Plenty of sun Tue with highs in the 80s NW of I-95 * Rather mild Tue night with lows in the 50s/lower 60s
Details...
Tuesday...
A ridge of high pressure off the mid-Atlantic coast will set the stage for summerlike warmth on Tue...at least away from the cooling marine influence near the south coast. S-SW surface winds should allow the low clouds and fog patches to burn off earlier than today. 850T warming to +15C should allow highs to reach the middle 80s in many locations northwest of I-95 and perhaps even a few spots flirt with the upper 80s. The S-SW winds will keep things a bit cooler southeast of I-95 which will probably hold highs in the 70s to near 80
In fact
on the very immediate south coast/Cape and Islands highs will only be in the 60s and perhaps a struggle to reach 60 in Nantucket.
Bottom line though is summer-like warmth is on tap for most of the region especially northwest of I-95.
A shortwave does track across northern New England. This coupled with diurnal heating/instability should trigger some scattered convection to our north
However
the dynamics/deeper moisture will remain across northern New England. This should result in generally a dry and warm Tuesday...but there is the risk of a brief spot shower or two during the afternoon/early evening hours across northwest and north central MA.
Tuesday night...
The ridge of high pressure off the mid-Atlantic coast will continue to generate a mild southwest flow of air Tue night.
While we probably will see some low clouds and fog patches redevelop...thinking is the main threat for these will be confined towards RI/SE MA. The southwest wind component will probably limit the northward extent compared to what we are expecting tonight
Low temps Tue night will be mild
mainly in the 50s to the lower 60s. The mildest of those low temps will be found northwest of I-95, furthest away from the cooling marine influence given the southwest wind trajectory.
LONG TERM /WEDNESDAY THROUGH MONDAY/
Highlights
* Above normal temperatures this week with highs ranging from the low to upper 80s Wednesday through Friday
* A cold front may trigger strong to severe thunderstorms west of I- 495 Thursday afternoon/evening.
* Seasonable/dry weather next weekend
Wednesday and Thursday
A broad upper-level ridge and associated surface high pressure over the eastern US will support a persistent deep southwest flow into The Northeast this week. As a result, the region is expecting well above normal temperatures with 925 hPa temps above 20 degrees Celsius through the end of the week. With diurnal mixing, this will translate to surface high temperatures ranging from the low to upper 80s Wednesday through Friday.
Wednesday will be the warmest day this week, with many locations across the interior approaching the upper 80s to low 90s.
Increasing cloudiness ahead of a cold front on Thursday will result in slightly cooler temperatures with highs in the low to mid 80s. The south coast, Cape, and Islands will be substantially cooler with onshore flow from the cooler ocean keeping highs in the 60s to low 70s Wednesday and Thursday.
In addition to the heat there will be a risk for thunderstorms on both Wednesday and Thursday afternoon. Latest guidance suggest any thunderstorm activity on Wednesday would be isolated an confined to western MA. Forcing looks to be weak on Wednesday, but there will be a modest amount of shear and instability in the atmosphere. Of greater concern is Thursday afternoon when strong to severe storms may be possible as a weak surface cold front pushes through The Northeast. Plenty of moisture and instability will be in place with dewpoints in the mid 60s and surface temps in the upper 80s to low 90s supporting SBCAPE values as high as 1000 J/kg. Furthermore, an upper-level jetstream to the north will support deep layer shear values between 30 and 40 knots. Should the values of these parameters verify, the ingredients would be in place for some areas of organized convection. Model guidance suggests the greatest height falls and forcing for ascent would be focused across the interior west of I-495. CIPS severe weather probability guidance is indicating a 30 percent chance of severe thunderstorm winds and a 15 percent chance of severe hail. CSU machine learning models are also hinting at severe thunderstorm potential with a 15 percent chance across western MA and CT. So while the heat will catch a lot of attention this week, we will also need to pay close attention to how the forecast unfolds for Thursday afternoon/evening.
Friday
Temperatures remain above normal on Friday with highs in the upper 70s to low 80s. Though the air should be more comfortable than on Wednesday/Thursday as dewpoints fall into the 50s behind a weak surface cold front. The column dries out behind this front as well with PWATs dropping to around 0.5 inches. This should result to a sunny/pleasant end to the work week.
Next Weekend
Forecast looks to be on the quiet side for Saturday with a dry/seasonable air mass supporting normal conditions across southern New England for late May. Sunday may become more unsettled as model guidance is hinting at high pressure offshore supporting an easterly wind over the region. This could come with cooler temperatures, clouds, and possibly light rain/drizzle. Details are vague at the 7 day time range, so stay tuned for more details later this week.
AVIATION /03Z TUESDAY THROUGH SATURDAY/
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High Confidence in trends, but lower confidence in specific timing.
Low end MVFR to IFR/LIFR conditions will ovespreads area near the Springfield, to Worcester to Beverly corridor...but may struggle to get too far northwest of that region. The greatest risk for LIFR conditions will be across RI/SE MA where low clouds arrive earlier and there also will be fog developing, which may become locally dense. Calm/light S winds.
Tuesday...High Confidence.
Low clouds and fog patches should burn off Tuesday morning as S/SW winds increase to 10-15 knots just after sunrise. May also see a few hours of localized sea breezes along the very immediate coast...but this should be overcome during the afternoon as gradient strengthens.
Tuesday night...Moderate Confidence.
Low clouds and fog patches redevelop Tue night, but probably only impact areas south of I-90 with the best chance across RI/SE MA. Surface winds out of the SW at 5-15 knots will probably keep the low clouds/fog from becoming as extensive and spreading as far north as tonight.
KBOS TAF...Moderate Confidence
High confidence in IFR ceilings developing around/after 06Z.
There is a low risk for LIFR ceilings around 400 feet after 09Z along with potential for MVFR vsbys in patchy fog near the terminal. Can't rule out a possible sea-breeze for a brief period Tuesday afternoon, but confidence is low given pretty strong southwest winds so have left out of TAF for now.
KBDL TAF...High confidence
Outlook /Wednesday through Saturday/...
Wednesday through Wednesday Night: VFR. Breezy.
Thursday: VFR. Breezy. Chance SHRA, isolated TSRA.
Thursday Night: VFR. Breezy. Chance SHRA.
Friday: VFR. Slight chance SHRA.
Friday Night through Saturday: VFR.
MARINE
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Tuesday night...High Confidence.
High pressure across the region this afternoon sinks south of the region tonight. This high then remains off the mid-Atlantic coast Tue and Tue night. This keeps the pressure gradient weak enough and winds/seas should generally remain below small craft advisory thresholds
That being said
we may see some 20+ knot S-SW wind gusts Tue afternoon and Tue night so some choppy nearshore seas are possible. The biggest concern for mariners though will be the formation of fog tonight, which may become locally dense tonight especially across the southern waters.
This fog should burn off by Tue afternoon.
Outlook /Wednesday through Saturday/...
Wednesday through Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft.
Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers.
Friday: Winds less than 25 kt. Slight chance of rain showers.
Friday Night through Saturday: Winds less than 25 kt.
BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...None.
Area Forecast Discussion National Weather Service Boston/Norton MA 1056 PM EDT Mon May 20 2024
SYNOPSIS
A ridge of high pressure sinks to our south tonight, setting the stage for summerlike warmth Tuesday through Thursday at least away from the immediate south coast. Generally dry weather is expected Tuesday and Wednesday, but an approaching cold front may bring a round of scattered showers and thunderstorms Thursday afternoon and evening. This will usher in more seasonable but generally pleasant weather for the Holiday weekend.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
Main forecast challenge overnight is the northward extent of stratus and fog. As of this writing, this stratus had just begun to reach the South Shore, as well as the South Coast of MA. Much of the Cape and islands were already blanketed as well.
Still have high confidence in stratus overspreading much of RI and southeast MA. However, have lower confidence in the timing.
Will be monitoring that overnight, as it will have implications for temperatures during the day tomorrow.
Minor tweaks to bring the forecast back in line with observed trends.
315 PM Update...
* Low Clouds and fog develop tonight with lows upper 40s/50s * Fog may become dense across parts of RI/SE MA tonight
A ridge of high pressure across southern New England gradually shifts to our southwest tonight, but remains in control of our weather. Light southerly flow and a cooling boundary layer will allow areas of low clouds and fog to redevelop from south to north after sunset. Give that the surface winds will be light/calm, some of the fog may become locally dense across RI/SE MA given 50+ dewpoints. It is possible later shifts may need to consider a Dense Fog Advisory for a portion of this region.
Overnight low temps should bottom out mainly in the lower to middle 50s, but may see readings drop to between 45 and 50 towards the Cape and Islands given lower dewpoints in that region.
SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/
Key Points...
* Summerlike Warmth Tue away from the south coast * Plenty of sun Tue with highs in the 80s NW of I-95 * Rather mild Tue night with lows in the 50s/lower 60s
Details...
Tuesday...
A ridge of high pressure off the mid-Atlantic coast will set the stage for summerlike warmth on Tue...at least away from the cooling marine influence near the south coast. S-SW surface winds should allow the low clouds and fog patches to burn off earlier than today. 850T warming to +15C should allow highs to reach the middle 80s in many locations northwest of I-95 and perhaps even a few spots flirt with the upper 80s. The S-SW winds will keep things a bit cooler southeast of I-95 which will probably hold highs in the 70s to near 80
In fact
on the very immediate south coast/Cape and Islands highs will only be in the 60s and perhaps a struggle to reach 60 in Nantucket.
Bottom line though is summer-like warmth is on tap for most of the region especially northwest of I-95.
A shortwave does track across northern New England. This coupled with diurnal heating/instability should trigger some scattered convection to our north
However
the dynamics/deeper moisture will remain across northern New England. This should result in generally a dry and warm Tuesday...but there is the risk of a brief spot shower or two during the afternoon/early evening hours across northwest and north central MA.
Tuesday night...
The ridge of high pressure off the mid-Atlantic coast will continue to generate a mild southwest flow of air Tue night.
While we probably will see some low clouds and fog patches redevelop...thinking is the main threat for these will be confined towards RI/SE MA. The southwest wind component will probably limit the northward extent compared to what we are expecting tonight
Low temps Tue night will be mild
mainly in the 50s to the lower 60s. The mildest of those low temps will be found northwest of I-95, furthest away from the cooling marine influence given the southwest wind trajectory.
LONG TERM /WEDNESDAY THROUGH MONDAY/
Highlights
* Above normal temperatures this week with highs ranging from the low to upper 80s Wednesday through Friday
* A cold front may trigger strong to severe thunderstorms west of I- 495 Thursday afternoon/evening.
* Seasonable/dry weather next weekend
Wednesday and Thursday
A broad upper-level ridge and associated surface high pressure over the eastern US will support a persistent deep southwest flow into The Northeast this week. As a result, the region is expecting well above normal temperatures with 925 hPa temps above 20 degrees Celsius through the end of the week. With diurnal mixing, this will translate to surface high temperatures ranging from the low to upper 80s Wednesday through Friday.
Wednesday will be the warmest day this week, with many locations across the interior approaching the upper 80s to low 90s.
Increasing cloudiness ahead of a cold front on Thursday will result in slightly cooler temperatures with highs in the low to mid 80s. The south coast, Cape, and Islands will be substantially cooler with onshore flow from the cooler ocean keeping highs in the 60s to low 70s Wednesday and Thursday.
In addition to the heat there will be a risk for thunderstorms on both Wednesday and Thursday afternoon. Latest guidance suggest any thunderstorm activity on Wednesday would be isolated an confined to western MA. Forcing looks to be weak on Wednesday, but there will be a modest amount of shear and instability in the atmosphere. Of greater concern is Thursday afternoon when strong to severe storms may be possible as a weak surface cold front pushes through The Northeast. Plenty of moisture and instability will be in place with dewpoints in the mid 60s and surface temps in the upper 80s to low 90s supporting SBCAPE values as high as 1000 J/kg. Furthermore, an upper-level jetstream to the north will support deep layer shear values between 30 and 40 knots. Should the values of these parameters verify, the ingredients would be in place for some areas of organized convection. Model guidance suggests the greatest height falls and forcing for ascent would be focused across the interior west of I-495. CIPS severe weather probability guidance is indicating a 30 percent chance of severe thunderstorm winds and a 15 percent chance of severe hail. CSU machine learning models are also hinting at severe thunderstorm potential with a 15 percent chance across western MA and CT. So while the heat will catch a lot of attention this week, we will also need to pay close attention to how the forecast unfolds for Thursday afternoon/evening.
Friday
Temperatures remain above normal on Friday with highs in the upper 70s to low 80s. Though the air should be more comfortable than on Wednesday/Thursday as dewpoints fall into the 50s behind a weak surface cold front. The column dries out behind this front as well with PWATs dropping to around 0.5 inches. This should result to a sunny/pleasant end to the work week.
Next Weekend
Forecast looks to be on the quiet side for Saturday with a dry/seasonable air mass supporting normal conditions across southern New England for late May. Sunday may become more unsettled as model guidance is hinting at high pressure offshore supporting an easterly wind over the region. This could come with cooler temperatures, clouds, and possibly light rain/drizzle. Details are vague at the 7 day time range, so stay tuned for more details later this week.
AVIATION /03Z TUESDAY THROUGH SATURDAY/
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High Confidence in trends, but lower confidence in specific timing.
Low end MVFR to IFR/LIFR conditions will ovespreads area near the Springfield, to Worcester to Beverly corridor...but may struggle to get too far northwest of that region. The greatest risk for LIFR conditions will be across RI/SE MA where low clouds arrive earlier and there also will be fog developing, which may become locally dense. Calm/light S winds.
Tuesday...High Confidence.
Low clouds and fog patches should burn off Tuesday morning as S/SW winds increase to 10-15 knots just after sunrise. May also see a few hours of localized sea breezes along the very immediate coast...but this should be overcome during the afternoon as gradient strengthens.
Tuesday night...Moderate Confidence.
Low clouds and fog patches redevelop Tue night, but probably only impact areas south of I-90 with the best chance across RI/SE MA. Surface winds out of the SW at 5-15 knots will probably keep the low clouds/fog from becoming as extensive and spreading as far north as tonight.
KBOS TAF...Moderate Confidence
High confidence in IFR ceilings developing around/after 06Z.
There is a low risk for LIFR ceilings around 400 feet after 09Z along with potential for MVFR vsbys in patchy fog near the terminal. Can't rule out a possible sea-breeze for a brief period Tuesday afternoon, but confidence is low given pretty strong southwest winds so have left out of TAF for now.
KBDL TAF...High confidence
Outlook /Wednesday through Saturday/...
Wednesday through Wednesday Night: VFR. Breezy.
Thursday: VFR. Breezy. Chance SHRA, isolated TSRA.
Thursday Night: VFR. Breezy. Chance SHRA.
Friday: VFR. Slight chance SHRA.
Friday Night through Saturday: VFR.
MARINE
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Tuesday night...High Confidence.
High pressure across the region this afternoon sinks south of the region tonight. This high then remains off the mid-Atlantic coast Tue and Tue night. This keeps the pressure gradient weak enough and winds/seas should generally remain below small craft advisory thresholds
That being said
we may see some 20+ knot S-SW wind gusts Tue afternoon and Tue night so some choppy nearshore seas are possible. The biggest concern for mariners though will be the formation of fog tonight, which may become locally dense tonight especially across the southern waters.
This fog should burn off by Tue afternoon.
Outlook /Wednesday through Saturday/...
Wednesday through Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft.
Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain showers.
Friday: Winds less than 25 kt. Slight chance of rain showers.
Friday Night through Saturday: Winds less than 25 kt.
BOX WATCHES/WARNINGS/ADVISORIES
CT...None.
MA...None.
RI...None.
MARINE...None.
Upton, NY,
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