Tuesday, May26, 2020
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Marine Weather and Tides
Siasconset, MA

Version 3.4
NOTICE
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.

Sunrise 5:15AMSunset 8:09PM Tuesday May 26, 2020 1:41 PM EDT (17:41 UTC) Moonrise 8:27AMMoonset 11:43PM Illumination 21% Phase: Waxing Crescent; Moon at 4 days in cycle
NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION.
Marine Forecasts
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7 Day Forecast for Marine Location Near Siasconset, MA
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location: 38.84, -69.85     debug


Area Discussion for - Boston, MA
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FXUS61 KBOX 261407 AFDBOX

Area Forecast Discussion National Weather Service Boston/Norton MA 1007 AM EDT Tue May 26 2020

SYNOPSIS. Warm front lifts through the area this afternoon followed by summer-like warmth and mugginess away from the coast through mid week. A cold front approaches from the west Friday and moves across the area Saturday. Both days will feature a risk of scattered showers and thunderstorms. Cooler, drier and less humid conditions follow on Sunday and Monday.

NEAR TERM /UNTIL 6 PM THIS EVENING/.

1005 AM Update .

The fog has pretty much burned off late this morning, but there were still two areas of low clouds. One area was located across the immediate eastern MA coast with another area across the CT River Valley region.

The strong late May sun angle will continue to erode most of these remaining low clouds through early afternoon. This combined with anomalously high height fields near 590 DM will set the stage for a very warm afternoon. 925T between 18C and 22C should allow afternoon high temps to reach the middle to upper 80s in many locations away from the coast. Dewpoints near or just above 60 will add a bit of humidity to the air as well, so definitely a summer feel away from the immediate coast. Onshore flow off the cool ocean will result in much cooler afternoon temps in the upper 60s to lower 70s along the very immediate coast. Also, will need to watch lower clouds and fog patches flirting with the coast all day especially toward evening.

SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/.

* Wednesday looks to be warmer than Tuesday, including coastal areas.

Tonight .

As for the overnight hours, areas of locally dense fog could develop along and near the coast with the warm and moist air mass advecting over the relatively cold ocean waters. Best chance of dense fog would be over the south coast and Cape and the islands. As for overnight lows, have gone with a blend of guidance to yield values in the mid 50s to low 60s. Areas of patchy drizzle are also possible along the south coast and Cape and the Islands. But no significant rain is expected because only levels below 850 mb are saturated according to Bufkit soundings.

Wednesday .

For Wednesday, NAEFS shows temperatures for all levels at the 99th percentile! With a predominant southwesterly flow on Wednesday, expect highs to be even warmer than on Tuesday. So once again have used the 90th percentile of guidance for high temperatures, which will see parts of the interior especially north of the MA Pike approach 90 degrees. Places like Boston on the Eastern MA coast should see highs in the 80s thanks to surface winds backing to the southwest and the wind fields are a bit stronger as well, which should help keep the sea breeze at bay.

LONG TERM /THURSDAY THROUGH MONDAY/. Big Picture .

At 500-mb, warm high pressure sits along/off the New England coast. This shows a warm deep-layer, with south to southwest winds closer to the surface. Contours are forecast at 588-590 Dm, which is almost as high as has been measured in late May. Expect a warm period to finish the week. Northern stream trough digs over the region over the weekend, followed by a reinforcing trough early next week. Heights dip to around 560 Dm, which is on the cool side of normal.

Based on the deep layer heights and a developing southwest flow near the surface, expect above normal temperatures Thursday-Friday, then trending to below normal Sunday-Monday.

Good agreement on mass fields through the weekend, thus moderate- high forecast confidence much of the period. Increasing differences Monday suggest moderate forecast confidence at best that day.

Daily Concerns .

Wednesday night-Thursday .

West Atlantic surface high brings a south-southwest flow to the surface layer, with low moisture levels through the deep layer Wednesday night. The weak south along the coast may support stratus and fog/drizzle especially along the South Coast. But otherwise a dry night. Dew points in the lower 60s suggest overnight min temps in the low to mid 60s.

Moisture levels trend higher Thursday as low level airflow turns more from the southwest. PW values reach 1.5 inches or higher Thursday afternoon. Even so, lift remains hard to find with the 30- kt low level jet directed more toward NY and PA than New England. Any showers will be widely scattered and mostly close to the low level jet west of us. The mixed layer reaches to 950 mb, but even temps at 925 mb look equiv to 8C at 850 mb. This would support max temps in the mid 70s south to around 80 along the NH border.

Friday-Saturday .

Northern stream shortwave moves through the flow, crossing the Great Lakes Friday and New England Saturday. Guidance shows early morning showers as the right entrance region of the upper jet approaches, with these conditions continuing Friday through early Saturday. Not much cold advection aloft during the day, but the CAA does increase later Friday night and Saturday morning. It is at that time that a cold front moves through. Stability parameters are most supportive in Eastern NY Friday afternoon, with LI values most impressive at -5 to -7 in the Hudson Valley. Convection firing in this zone could then move into Western MA. Favorable stability values shift east along/ahead of the cold front Friday night/Saturday. Expect scattered showers/tstms during this time. High PW values also continue during this time, suggesting some local downpours possible.

Drier air moves in from the west late Saturday afternoon and night with clearing skies from west to east. A few showers may linger over the Cape and Islands Saturday night.

Sunday-Monday .

Surface ridge over the Great Lakes while upper trough digs through Eastern Canada over New England. Cold advection continues, with the associated -27C cold pool core moving across Nrn New England while Srn New England sees values of -20C to -25C. The airmass is forecast to be dry, but the low values lend some concern for diurnal clouds especially Monday.

AVIATION /14Z TUESDAY THROUGH SATURDAY/. Forecaster Confidence Levels .

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

14Z Update .

Late this morning and afternoon . Moderate to high confidence. Lingering IFR conditions in low clouds across the CT River Valley will improve to VFR as these clouds continue to erode through early afternoon. Another area of low clouds and fog along the immediate coast should also erode, but still will have to watch for some lingering patches flirting with the coast through the afternoon Otherwise. VFR dominates by afternoon with S winds of 5 to 10 knots except for some sea breezes on the immediate coast.

Tonight . Moderate confidence. VFR conditions for most areas away from the immediate coast. MVFR to IFR vsby possible with development of locally dense fog along the immediate coast. Winds turning southwest at about 5 kt.

Wednesday . High confidence. VFR conditions. Southwest winds at 5 to 10 kt with gusts of 15 kt.

KBOS Terminal . Moderate confidence in TAF.

KBDL Terminal . High confidence in TAF, but moderate confidence in timing.

Outlook /Thursday through Saturday/ .

Wednesday Night: Mainly VFR, with local IFR possible in fog, mainly South Coast. Slight chance SHRA, patchy BR.

Thursday: Mainly MVFR, with areas VFR possible. Breezy. Slight chance SHRA.

Thursday Night through Friday: Mainly MVFR, with local IFR possible. Breezy. Chance SHRA, slight chance TSRA.

Friday Night: Mainly MVFR, with areas IFR possible. Breezy. Chance SHRA, slight chance TSRA, patchy BR.

Saturday: Mainly MVFR, with areas IFR possible. Trending VFR late afternoon and night. Breezy. Chance SHRA, slight chance TSRA.

MARINE. Today . Patchy morning fog and drizzle gives way to dry weather in the afternoon along with improving vsby. SE winds become SSW in the afternoon as warm front lifts north of the area. Winds at 5 to 10 kt. Seas 3 ft or less.

Tonight . Areas of fog develop with SSW winds of 8 to 12 kt. Seas 2 to 4 ft.

Wednesday . Patchy fog gives way to dry weather. SSW winds of 10 to 15 kt. Seas 2 to 4 ft.

Outlook /Thursday through Saturday/ .

Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

Thursday: Winds less than 25 kt. Seas less than 5 feet.

Thursday Night: Winds less than 25 kt. Seas less than 5 ft. Chance of rain showers.

Friday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas, with 5 to 7 feet on the outer waters. Chance of rain showers, slight chance of thunderstorms.

Saturday: Winds less than 25 kt. Seas 5 to 7 feet, mainly on the outer waters. Chance of rain showers, slight chance of thunderstorms.

BOX WATCHES/WARNINGS/ADVISORIES. CT . None. MA . None. RI . None. MARINE . None.

SYNOPSIS . WTB/Chai NEAR TERM . Frank SHORT TERM . Chai LONG TERM . WTB AVIATION . Frank/Chai/WTB MARINE . WTB/Chai


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA168 mi49 minS 710.00 miOvercast59°F55°F87%1023.4 hPa

Link to 5 minute data for KACK

Wind History from ACK (wind in knots)
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Last 24hrE10E10E10E8E7NE7E4E6E4NE3N6NE6NE5E6NE4N4N3NE4N4CalmCalmSE6SE8S7
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Tide / Current Tables for
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Weather Map
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NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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Wind Forecast for Boston, MA (13,3,4,5)
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Ground Weather Radar Station Upton, NY
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The information on this web site has not been checked for accuracy. It is for entertainment purposes only and should be independently verified before using for any other reason. There are five sources. 1) Documents and manuals from a variety of sources. These have not been checked for accuracy and in many cases have not even been read by anyone associated with L-36.com. I have no idea of they are useful or accurate, I leave that to the reader. 2) Articles others have written and submitted. If you have questions on these, please contact the author. 3) Articles that represent my personal opinions. These are intended to promote thought and for entertainment. These are not intended to be fact, they are my opinions. 4) Small programs that generate result presented on a web page. Like any computer program, these may and in some cases do have errors. Almost all of these also make simplifying assumptions so they are not totally accurate even if there are no errors. Please verify all results. 5) Weather information is from numerous of sources and is presented automatically. It is not checked for accuracy either by anyone at L-36.com or by the source which is typically the US Government. See the NOAA web site for their disclaimer. Finally, tide and current data on this site is from 2007 and 2008 data bases, which may contain even older data. Changes in harbors due to building or dredging change tides and currents and for that reason many of the locations presented are no longer supported by newer data bases. For example, there is very little tidal current data in newer data bases so current data is likely wrong to some extent. This data is NOT FOR NAVIGATION. See the XTide disclaimer for details. In addition, tide and current are influenced by storms, river flow, and other factors beyond the ability of any predictive program.