Friday, September21, 2018

Marine Weather and Tides
Siasconset, MA

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9/17/2018 XTide broke when 1and1 "upgraded" my server. It has been esculated. I am sorry for the problem.

Sunrise 6:31AMSunset 6:44PM Friday September 21, 2018 11:18 AM EDT (15:18 UTC) Moonrise 5:10PMMoonset 2:53AM Illumination 88% Phase: Waxing Gibbous; Moon at 12 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 211411
area forecast discussion
national weather service boston norton ma
1011 am edt Fri sep 21 2018

High pressure will move slowly to the east this afternoon. A
cold front sweeps across the region late tonight with showers
and a few thunderstorms. Large high pressure will then bring dry
but cool conditions this weekend lasting into Monday. Another
round of scattered showers and a few thunderstorms are expected
Tuesday afternoon through Wednesday evening as a series of
fronts move across the region. High pressure will bring dry
conditions Thursday.

Near term until 6 pm this evening
High pressure centered over nova scotia and extending across srn
new england and the mid atlantic coast, maintaining cool dry air
across SRN new england. Increasing south to southwest winds
across the eastern and central great lakes are drawing warmer
and more humid air north across that region. Low level jet
and concurrant mixing are generating gusty winds with gusts
roughly 20 to 25 knots. All of this is shifting eastward.

Satellite shows a broad area of low clouds from the berkshires
through the catskills, with additional clouds across much of
northern ct and central northeast mass, and clouds mixed with
sunshine farther east.

The surge of warm air through ny is most active from NRN ny
through NRN new england, where showers were moving through
during the morning. These will move off through maine this
afternoon. Jet support and instability is focussed to our west
this afternoon, and we would expect the best chance of afternoon
showers tstms to be well to our west during that period.

For SRN new england, expect clouds west and mixed clouds sun
east, temps reaching the upper 60s to mid 70s. The low level jet
affecting areas farther west will reach our area late this
afternoon, and should support south-southwest wind gusts up to
25 mph.

Short term 6 pm this evening through 6 pm Saturday

cold front moves across sne late tonight, mainly 06-12z and will
be accompanied by a weakening line of convection from new york
state, mainly after midnight. Surface instability is non
existent, but low level theta-e ridge and ki values into the mid
30s ahead of the front support a line of showers and possibly a
few t-storms. This activity will weaken as it approaches the
coast so best chance for thunder will be in western new eng.

Gusty S SW winds will continue tonight, especially near the
coast where gusts 25-35 mph likely. Dewpoints will be climbing
into the 60s with temps holding steady in the upper 60s ahead
of the front, but cooling interior northern and western ma late
tonight behind the front.


the cold front moves south of the coast in the morning followed
by high pres and very dry air advecting into the region. Some
clouds may linger near the south coast early, otherwise lots of
sunshine expected. Gusty post-frontal NW winds expected in the
morning near the coast, then diminishing in the afternoon. Highs
upper 60s to lower 70s with dewpoints falling through the 50s
and into the 40s in the afternoon.

Long term Saturday night through Thursday

* large high pressure will bring dry, cool conditions late this
weekend into early next week
* a slow moving warm front brings scattered showers and a few
thunderstorms late Tuesday through Wednesday
* above normal temperatures briefly arrive Wednesday
* cooler temperatures return late next week as cold front passes

00z model suite continues trend of fast moving weather systems
into early next week thanks to a nearly zonal mid level
steering flow across the northern tier states. H5 begins to
amplify a trough as it moves out of the northern rockies mon
night Tue timeframe as the long wave ridge tends to suppress
south across the mid atlc and SE u.S. Some ridging does build
into quebec in response to the digging trough, which will allow
for a brief period of milder temperatures but will also see
scattered showers and isolated thunderstorms around the middle
of next week with an approaching frontal system. Noting a cold
front working SE by late next week, which should bring another
shot of cooler air, but there are timing issues in play amongst
the model suite, so have lower confidence during the later

With the approaching frontal system around the Tuesday
afternoon through Wednesday timeframe, noting marginal
instability with tq values in the upper teens and k indices in
the lower 30s. Have mentioned isolated thunderstorms through
this time, but will convection looks to be spotty at this

Expect temperatures through most of this period running close
to or below normal. However, with the ridging that builds in
ahead of the tue-wed system, could see temps on Wed run 5 to 10
degrees above seasonal normals.

Aviation 14z Friday through Tuesday
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Saturday ...

this afternoon... Moderate confidence. MainlyVFR in the east
with areas of MVFR CIGS persisting across western new england.

Increasing S winds this afternoon with gusts to 20-25 kt
developing after 21z.

Tonight... Moderate confidence.

Cigs lowering to MVFR with a band of sct showers and isold
t-storms moving west to east across sne 04-10z. Greatest
coverage across western new eng with activity weakening as it
moves east. S SW wind gusts to 20-30 kt, strongest near the

Saturday... High confidence.

Some lingering MVFR CIGS early CAPE islands, otherwiseVFR.

Gusty NW winds in the morning diminishing in the afternoon.

Kbos terminal... Moderate confidence in taf.

Kbdl terminal... Moderate confidence in taf.

Outlook Saturday night through Tuesday ...

Saturday night through Sunday:VFR.

Sunday night through Monday:VFR. Breezy.

Monday night:VFR. Breezy. Slight chance shra.

Tuesday: mainlyVFR, with local MVFR possible. Breezy.

Chance shra.

Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Saturday ... High confidence.

Through tonight...

increasing S winds developing this afternoon and peaking
tonight as a 45-50 kt low level jet develops. Given warm sst,
expect sufficient mixing to bring down some of this wind with
gale force gusts to 35-40 kt over eastern ma waters. Converted
gale watches to warnings for eastern ma waters with SCA for
south coastal waters and bos harbor. A few showers and perhaps
an isold t-storm is possible late tonight, after midnight.


w NW wind gusts to 25-30 kt in the morning diminishing rapidly
and becoming N NE in the afternoon as high pres builds over the
waters. Seas subsiding.

Outlook Saturday night through Tuesday ...

Saturday night through Sunday: winds less than 25 kt.

Sunday night: low risk for small craft advisory winds with
gusts up to 25 kt. Seas locally approaching 5 ft.

Monday: low risk for small craft advisory winds with gusts up
to 25 kt. Seas up to 5 ft.

Monday night: low risk for small craft advisory winds with
gusts up to 25 kt. Local rough seas.

Tuesday: moderate risk for small craft advisory winds with
gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.

Box watches warnings advisories
Ct... None.

Ma... None.

Ri... None.

Marine... Small craft advisory from 8 pm this evening to 11 am edt
Saturday for anz232>235-237.

Small craft advisory from 5 pm this afternoon to 11 am edt
Saturday for anz230.

Gale warning from 8 pm this evening to 5 am edt Saturday for

Small craft advisory from 8 pm this evening to 8 am edt
Saturday for anz236.

Gale warning from 8 pm this evening to 8 am edt Saturday for

Small craft advisory from 8 pm this evening to 2 pm edt
Saturday for anz255-256.

Synopsis... Kjc evt
near term... Wtb kjc evt
short term... Kjc
long term... Evt
aviation... Wtb kjc evt
marine... Wtb kjc evt

Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA168 mi85 minSSE 610.00 miA Few Clouds64°F53°F68%1026.2 hPa

Wind History from ACK (wind in knots)
Last 24hrNE14NE11NE14NE12NE12
1 day agoNE12NE19
2 days agoS15S13S15

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Weather Map and Satellite Images
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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 (11,2,3,4)
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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 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 numerious of sources and is presented automatically. It is not checked for accuracy either by anyone at 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.