Saturday, August17, 2019 L-36.com


Marine Weather and Tides
Siasconset, MA

Version 3.4
NOTICE
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.
6/2/2019. Many thanks to a user for reporting an error on one of the Edit pages. The switch to PHP 7.2 caused many pages that previously worked to quit working. I fixed many but I still depend on users to report ones I missed. Please report errors HERE or send an email to me at L-36.com. Allen

Sunrise 5:54AMSunset 7:43PM Saturday August 17, 2019 9:36 AM EDT (13:36 UTC) Moonrise 8:59PMMoonset 7:39AM Illumination 96% Phase: Waning Gibbous; Moon at 17 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
    EDIT      (on/off)   Help


7 Day Forecast for Marine Location Near Siasconset, MA
   Hourly   EDIT   Help
location: 38.84, -69.85     debug


Area Discussion for - Boston, MA
      (on/off)   Help   NOTE: mouseover dotted underlined text for definition
Fxus61 kbox 171153
afdbox
area forecast discussion
national weather service boston norton ma
753 am edt Sat aug 17 2019

Synopsis
Mainly dry, seasonable conditions continue today, with a chance
for showers and an isolated thunderstorm north and west. Humid,
hot conditions return Sunday, with an increasing risk for some
showers and thunderstorms. These conditions continue through
midweek, when a cold front will sweep through. Drier and not as
warm late next week.

Near term until 6 pm this evening
Only minor tweaks to the forecast this morning to reflect
observed trends.

Previous discussion...

no huge changes to the prior forecasts we've had. In general,
today will be a dry day, though it will feel a bit muggy. Quite
a bit of low clouds across much of the region early this
morning, with some areas of fog -- especially across far SE ma.

Still some uncertainty as to how widespread the fog will be
first thing this morning, but at this point thinking it won't be
too bad (famous last words). Also watching showers approaching
the ct border. Seem to be slowly weakening, but could reach the
hartford area before they totally vanish. Have maintained some
low pops in that area.

The low clouds will slowly break up later this morning, but with
ample moisture, they'll quickly be replaced by daytime cumulus.

Net result is that we'll end up partly sunny. 925mb temperatures
are on the rise, and will be around 19c in the east to 21c in
the west. That should support temperatures in the mid 80s
(especially in areas that get the most sun). A light
south southeast flow will ensure cooler conditions will occur
along the coast.

Some surface based instability, with capes of 1000-1500 j kg is
expected to develop across central western ma and northern ct
this afternoon. Not a huge amount of forcing around locally
(much better farther to our north and west), but an isolated
shower or t-storm is not out of the question. Have painted in
20-30% pops across that area, generally using a blend of hi-res
models as the foundation for that aspect of the forecast.

Short term 6 pm this evening through 6 pm Sunday
As of 300 am...

models indicate a weak shortwave will zip across northern new
england overnight. Despite the loss of daytime heating, the
southern tail of that piece of energy will be close enough to
keep the threat of showers or a thunderstorm going through the
first half of the overnight -- especially for areas along and
north of the mass pike. In addition, the shortwave will help to
produce a decent amount of shear, with 0-6km shear progged to be
30-35kts in that area. That suggests the potential for some
organization so perhaps we'll see a strong storm during the
evening.

Otherwise across the eastern half of the region, all guidance
suggests a return of the low clouds and even better chances of
widespread fog, much of it could be rather dense.

Temperatures will only drop off to the mid 60s to low 70s in
urban areas, with dewpoints still running high -- so it will be
again muggy.

Sunday we'll see southwest flow get deeper, with even more
moisture pushing into the area. Precipitable water values will
be approaching 2" by afternoon. Models are also indicating
additional shortwave energy coming through at some point in the
day. GFS has a single stronger wave, while the NAM is a bit
disorganized with several weaker disturbances. Net result is the
same however, that we should see scattered showers and a few
t-storms develop. Primary area would be central and western ma
and northern ct. Lesser chances across SE ma and the
cape islands as low level southwest flow off the water will keep
things stable. Don't see indications of strong organized
convection, but perhaps more florida-like pulse type storms.

With the high moisture values, brief downpours would be the
primary threat.

Temperatures should be a few degrees warmer as 925mb
temperatures are in the 21-24c range. Given full sun, we would
be talking about surface temperatures pushing 90f. However there
should be a good deal of clouds, so I stuck a little bit toward
some of the "cooler" guidance. Lots of mid 80s for highs (cooler
along the coast)

Long term Sunday night through Friday
17 00z guidance remains in rather good agreement with the
overall synoptic pattern through the end of next week. With a
dominant ridge across the southern usa, the northern tier
remains under the influence of a decent mid level flow. This
mid level flow will steer a series of shortwaves in our
direction through mid week. While we have high confidence these
waves will pass nearby, the timing remains more uncertain. Will
continue to favor a consensus approach, with a bias toward
typical convective climatology for our region.

A cold front will start to approach our region Tuesday, but is
unlikely to get enough push to completely cross southern new
england until sometime Thursday. This will be the general
period of greatest risk for any showers and thunderstorms.

High pressure with drier weather expected for next Friday.

Until this front crosses our region, it should remain very warm,
if not hot, and very humid. Dewpoints should approach 70
degrees, raising the possibility of local downpours where it
does rain. With temperatures around 90 degrees early next week,
we may need heat advisories for a time.

Aviation 12z Saturday through Wednesday
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Sunday ... Moderate confidence.

Expecting more widespread stratus this morning. Visibility
dropped briefly around 12z, but should improve through 14z.

Appears the low ceilings will be slow to lift dissipate, soVFR
conditions aren't expected until 17z or so in most areas. MVFR
ceilings will likely remain all day along off the south coast of
ma.

All available guidance indicates Saturday night has a higher
probability of seeing widespread ifr, not only ceilings but
visibility as stratus and fog is expected cover much of eastern
ma and ri, especially after 02z or so.

There is a small chance for a few showers or a thunderstorm
across northern ct and western ma late this afternoon, with the
chances increasing slightly Saturday night, and have included
vcsh for baf and bdl tafs.

Kbos terminal... Honestly, the easiest aspect of the forecast are
winds, which will remain 10kts or less from 110-130 degrees.

Ceilings expected to drop under 1000ft through 12z or so, but
might stay a bit higher. Visibility forecast is low confidence
through 12z. More confident for ifr visibilities Saturday night.

Kbdl terminal... Overall moderate confidence in taf.

Outlook Sunday night through Wednesday ... Moderate confidence.

Sunday night: mainlyVFR, with local MVFR possible. Chance
shra with isolated tsra. Patchy br.

Monday through Monday night:VFR. Slight chance shra with
isolated tsra.

Tuesday through Wednesday:VFR. Chance shra with isolated tsra.

Marine
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Sunday ... High confidence.

Primary marine concern will be areas of fog. Fog today will be
primarily concentrated off the south coast and south of CAPE cod
and around the islands. Most should diminish during the mid-day,
but some areas will persist. The fog will redevelop Saturday
night, and is expected to stretch even up the east coast of
ma. Once again on Sunday, some fog will persist much of the day
offshore. Visibilities will be reduced to less than 1 mile in
the fog. Winds and seas aren't expected to be much of an issue.

Potential for a bump up in wave heights late this weekend and
into next week as we may see a short period southerly swell
develop due to several weak low pressure systems develop off the
north carolina coast and move out to sea.

Outlook Sunday night through Wednesday ... Moderate confidence.

Sunday night through Monday: winds less than 25 kt. Seas
locally approaching 5 ft. Slight chance of rain showers. Patchy
fog.

Monday night: winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.

Tuesday through Tuesday night: winds less than 25 kt. Seas
locally approaching 5 ft. Chance of rain showers with isolated
thunderstorms.

Wednesday: winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers with isolated thunderstorms.

Box watches warnings advisories
Ct... None.

Ma... None.

Ri... None.

Marine... None.

Synopsis... Belk nash
near term... Belk nash
short term... Nash
long term... Belk
aviation... Belk nash
marine... Belk nash


Weather Reporting Stations
   EDIT       (on/off)   Help   NOTE: Click on distance to see the station location on a map

Airport Reports
    EDIT      (on/off)   Help   Click EDIT to display multiple airports. Follow links for more data.
AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA168 mi1.7 hrsENE 70.50 miFog64°F64°F100%1018.4 hPa

Link to 5 minute data for KACK

Wind History from ACK (wind in knots)
10
AM
11
AM
12
PM
1
PM
2
PM
3
PM
4
PM
5
PM
6
PM
7
PM
8
PM
9
PM
10
PM
11
PM
12
AM
1
AM
2
AM
3
AM
4
AM
5
AM
6
AM
7
AM
8
AM
9
AM
Last 24hrNE8NE9NE9NE10NE11E6E7E8E7E8E5E6E6E6E6E7E7SE5E5E4E7E6E7E8
1 day agoNE12E13NE13NE10NE13NE10E9NE10NE8NE8NE7NE6E6NE6E5E6NE5NE6E7E6E6E6NE7NE4
2 days agoN8NE6N8N6NE8N9NE9N11NE9NE12NE10NE10NE7NE8NE6E4E5NE3NE3NE4NE6N10NE10NE12

Tide / Current Tables for
   EDIT   Weekend mode (on/off)   (on/off)   Help
Tide / Current Tables for
   EDIT      (on/off)   Help
Weather Map and Satellite Images
       (on/off)   HelpWeather Map
wmap_A
GOES Local Image of    EDIT
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.
Link to Loop

Other links: Northern Pacific     Contential US     Full GOES-East
Wind Forecast for Boston, MA (9,2,3,4)
      (on/off)   Help

Ground Weather Radar Station Upton, NY
   (on/off)   Help
weather_mapweather_map weather_map

Ad by Google

Disclaimer:
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 numerious 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.