Saturday, June12, 2021
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Marine Weather and Tides
Siasconset, MA

Version 3.4
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3/30/2021 -- ANZ330 has been split into ANZ331 and ANZ332. Click EDIT in Marine Forecast and select your new zone.
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.

Sunrise 5:09AMSunset 8:21PM Saturday June 12, 2021 10:46 AM EDT (14:46 UTC) Moonrise 6:47AMMoonset 10:17PM Illumination 7% Phase: Waxing Crescent; Moon at 2 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 121342 AFDBOX

Area Forecast Discussion National Weather Service Boston/Norton MA 942 AM EDT Sat Jun 12 2021

SYNOPSIS. Showers move south of our area by early afternoon, then trending drier. A weaker frontal passage brings a period of steady rains on Sunday night into early Monday. A stronger frontal passage will feature better chances for showers and thunderstorms later Monday into Monday night. Mainly dry and seasonable temperatures for the middle of the week. Turning warmer by late in the week, ahead of the next cold frontal passage around late Friday or Saturday.

NEAR TERM /THROUGH TONIGHT/. 940 AM Update:

Radar imagery shows the back edge of the showers passing through CT/RI and Cape Cod, moving fairly rapidly to the SE. Remainder of MA still had considerable cloud cover, however rain had come to an end. Can't rule out some patchy light drizzle for another hour or so behind the last of the rain/showers. Updated POPs to reflect these latest trends. Through early this afternoon, continue to think we'll have more clouds than sun, as looking at model soundings, if we do break into some sunshine that would be followed fairly quickly with development of stratocumulus.

Early morning discussion follows .

Showers will be ongoing early this morning, but will move off the coast by mid/late morning as a mid level shortwave and supporting jet dynamics move farther east. Clouds are likely to linger until mid to late afternoon before the drier air arriving from the north can generate more significant breaks. Clouds will linger longest towards the south coast of New England.

Pressure gradient remains weak, so sea breezes are likely to develop, especially once clouds dissipate and heating becomes more effective. Below normal high temperatures expected due to the morning clouds.

SHORT TERM /SUNDAY/. Sort of an in-between pattern across southern New England tonight into Sunday. A dissipating cold front will try to move across our region tonight. Mid level flow is more suggestive of a showery pattern, too. However, not a tremendous amount of moisture to work with. Thinking another round of clouds at most tonight. A little different story Sunday afternoon. A low pressure moving in the Great Lakes should push its warm front towards our region late in the day. So besides the increasing clouds, have included a risk for some showers also, mainly across the western half of MA. Near normal temperatures expected.

LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/. Highlights:

* Period of rain Sunday night into early Mon.

* Stronger frontal passage later Mon/Mon night. Is conditional on more clearing, but a few strong/severe t-storms are possible in the interior.

* Other than pop-up showers Tues, Tues-Thurs look mainly dry with seasonable temps. around 15

* Warming into the mid 80s late week. Next frontal passage around late Fri or Sat. Details:

Sunday Night into Monday Night:

Though some small timing differences exist, the more active weather is front-loaded to this period. Couple periods of wet weather: one Sunday night into early Mon, and then the next round for the second half of Mon into Mon night. Of the two periods, its the second one that could be active, if still conditional.

So for Sunday night/early Monday, first bundle of vort max energy moves through NY into New England Sunday night/overnight, then shifting off the coast early on Monday. Decent surge in moisture return with PWAT values in the 1.25-1.3" range per the 21z SREF; dewpoints also tend to rise into the upper 50s to low 60s overnight which will also boost K-indices a bit. Idea for steady rains, possibly with a rumble or two of thunder still looks on track. Given the PWAT values and reasonable consistency in QPF both in individual and NBM guidance, may be some brief downpours at times. Lows mid 50s to low 60s.

Still early and there are some uncertainties, but there are now several ingredients and elements that suggest Monday aftn into early evening could be active, with a conditional strong/severe storm risk in the interior. After rains from overnight and early Monday exit, it looks like the rest of Monday may stay at least considerably cloudy and that may temper surface-based instability and potentially keep temperatures on the cooler side. However a stronger/digging shortwave trough and associated frontal zone arrives mid to late in the day in western-central MA and northern CT. There are some steeper mid-level lapse rates (in the 6.5-7 C/km range) ahead of this frontal system, but looks like cloud cover may keep most- unstable CAPEs in the 1000 J/kg range in our Berkshires, CT Valley to central MA areas. What may help offset the lower-instability values is SNE being positioned in the cyclonic-shear/poleward exit region of a 500 mb 45-50 kt jetstreak. These strengthening wind fields bring effective-layer shear values around 50 kt where the instability axis lies. So, an overlap of wind shear and (limited) instability exist, especially in the NAM/GFS. Timing and the extent of cloud cover are the bigger uncertainties but it's not out of the question that Monday could have some stronger storms around with best chance in the interior. This risk increases if there are more breaks in clouds and stronger heating to destabilize the atmosphere more than currently reflected in the guidance. Something that will bear close watch as we move into the range of the mesoscale models. Weakening showers/storms then roll eastward into more-stable eastern MA/RI later Monday into Monday night. Kept Monday's highs close to NBM in the 70s but possible these may need to be lowered if clouds hang tough; lows in the upper 50s to the lower 60s.

Tuesday through Thursday:

An amplified longwave trough (-2 sigma standardized height anomalies per ensembles) sets up across New England and the broader eastern US around Tues and remains established until later on Thurs.

Pop-up scattered showers following the diurnal heating cycle still look possible into Tuesday, but not a washout and many stay dry most of the time. Cyclonic flow aloft is maintained Wed into Thurs, though surface ridge builds in from the Gt Lakes and should permit dry weather. Midweek looks to be the pick of the workweek weather- wise, with temperatures still looking seasonable or slightly cooler than average.

Friday into Saturday:

Longwave trough over New England is replaced by shortwave ridging on Fri, with a warming trend taking place on SW winds. 850 mb temps rise back into the mid-teens Celsius neighborhood, which brings highs back into the middle 80s by late in the week into Sat. Despite the warmth, dewpoints still look on the lower/comfortable side, though.

Operational models show a potent shortwave trough and associated cold front arriving either later Friday or on Saturday, looking to be the next chance at more widespread precip. Will have to fine-tune the timing of this frontal system. As of now, looks like Saturday has better chances for showers and thunderstorms but still too uncertain to lock this in as of yet.

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

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

14Z Update:

Today: Moderate confidence.

Mix of flight categories through midday, lowest MVFR-IFR, with rain moving south of the area by 15-16Z. Improvement in CIGs generally 15-17z, earliest north and latest south. Conditions improving to VFR this afternoon. Light winds with sea breezes developing.

Tonight . High confidence. Mainly VFR, but patchy late night fog possible.

Sunday . High confidence. Mainly VFR. Low risk for some showers late in the day, mainly across western MA.

KBOS TAF . Moderate confidence in TAF. Showers have moved south of BOS, however IFR CIGs still possible through 15Z. VFR conditions should return around 16Z.

KBDL TAF . Moderate confidence in TAF. IFR to start, with -RA ending around 14Z. VFR conditions should return by 16-17Z.

Outlook /Sunday Night through Wednesday/ .

Sunday Night: Mainly VFR, with local IFR possible. Breezy. Chance SHRA.

Monday: Mainly MVFR, with local IFR possible. Breezy. Chance SHRA, chance TSRA.

Monday Night: Mainly MVFR, with local IFR possible. Chance SHRA.

Tuesday: Mainly VFR, with areas MVFR possible. Chance SHRA.

Tuesday Night: VFR.

Wednesday: VFR. Breezy.

MARINE. Forecaster Confidence Levels.

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

Short Term /through Sunday/ .

Winds and seas expected to remain below Small Craft Advisory thresholds.

Outlook /Sunday Night through Wednesday/ .

Sunday Night through Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers.

Tuesday Night through Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

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

SYNOPSIS . Belk/Loconto/NMB NEAR TERM . Belk/Loconto SHORT TERM . Belk LONG TERM . Loconto AVIATION . Belk/Loconto/NMB MARINE . Belk/Loconto


Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA168 mi54 minNE 89.00 miLight Rain61°F58°F90%1011.5 hPa

Link to 5 minute data for KACK

Wind History from ACK (wind in knots)
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2 days agoW10W9W11W10SW12W9W10W8SW6W3SW4W4CalmSW3NW5N8N10N11NE11NE10N11NE15NE19
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