Thursday, November15, 2018 L-36.com


Marine Weather and Tides
Siasconset, MA

Version 3.4
What's New / NOTES
10/6/2018 Colors of tide XTide graphs changed to emphasize that they were upgraded. See next note. Comments welcome.
10/4/2018 I have fixed XTide and updated the harmonic files. There were some name changes so you might have to click EDIT to find the new station name.

Sunrise 6:33AMSunset 4:26PM Thursday November 15, 2018 4:04 PM EST (21:04 UTC) Moonrise 1:43PMMoonset 12:00AM Illumination 53% Phase: First Quarter Moon; Moon at 8 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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ANZ005 301 Pm Est Thu Nov 15 2018
Synopsis for eastport me to stonington me out 25 nm.. High pres will move E of the area this evening. Coastal low pres will approach from the sw late tonight, cross the northern gulf of maine Fri afternoon, then exit across the maritimes Fri night and Sat. High pres from the W will approach the region Sun.


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 152039
afdbox
area forecast discussion
national weather service boston norton ma
339 pm est Thu nov 15 2018

Synopsis
A high impact but short duration snowstorm is on tap for areas
away from the very immediate coast this evening. Precipitation
transitions to mainly ice and then rain overnight, except
perhaps portions of the high terrain in massachusetts. Dry
weather with chilly temperatures move in Friday afternoon
through most of the weekend as high pressure builds across. A
weak low may bring patchy light rain and or snow late Sunday
into Monday. Another shot of colder air moves in by the middle
of next week, though it should be mainly dry.

Near term until 6 am Friday morning
235 pm update...

* high impact short duration snowstorm this evening for many
* winter storm warnings posted for northwest of i-95
a high impact short duration winter storm is on tap across much
of the region this evening. Potent closed mid level energy
across the ohio valley was inducing an 80+ knot winds at 700 mb.

The result has been for heavy snow to break out across portions
of the mid atlantic states this afternoon.

1) heavy snow away from the very immediate coast this evening:
this potent speed MAX convergence zone at 700 mb will continue
to lift northward resulting in very strong frontogenetic
forcing this evening across southern new england. Heavy snow
should develop after 4 or 5 pm across our northern ct zones and
spread northeastward into northeast ma after 7 or 8 pm. Highest
impact expected in our ct zones... Given the heavy snow with 1 to
2 inch per hour rates will impact a large portion of the
evening rush hour. The latter half of the evening rush hour will
likely be impacted in the springfield... To worcester to
providence areas.

The biggest question with this forecast is how well this band of
strong frontogenesis will maintain itself as it lifts northeast.

Confidence is highest across our ct ri and interior southeast ma
zones. Further north... The guidance is somewhat split on that
potent speed MAX at 700 mb. The rgem NAM maintain it across
northern ma... While the ECMWF gfs tend to weaken it and shunt it
further east. Regardless... It will snow heavy across much of the
region for a time but this will impact accumulations. We still
feel that 4 to 7 inches of snow looks good for much of the
region. Given the short duration high impact event and
considering some light icing will persist after the main
event... Feel warnings are warranted for much of the region. Snow
amounts will likely be much lighter on the very immediate
coast. Sst around 50 with an easterly wind will result in making
it difficult to get more than an inch in these locations before
a quick change to rain.

2) warming aloft mid level dry air late this evening:
much of the region appears cold enough for mainly snow through
02z or 03z. However... The very potent 700 mb southerly jet will
transport mid level warmth northward across the region. Ptype
should transition from snow to ice rain from 02z through 06z
across southern new england. At the same time... Mid level dry
air will be cutting off our snowgrowth. Regardless... It appears
that the damage will be done across the region but some lighter
rain ice will linger. Ptype will mainly be rain across eastern
ma ri... But some light sleet freezing rain may persist for a
time across the interior.

It does appear that temperatures by daybreak Friday will be
above freezing for most of the region for the morning rush hour.

The exception will be some of the high terrain... Especially
interior northern ma where some light sleet freezing rain may
still result in slippery travel
3) strong to damaging winds:
a strong easterly low level jet of 55 to 65 knots is expected
to develop at 925 mb during the overnight hours along with
impressive pressure falls. Low level lapse rates are fairly
steep along the coast. This will result in a period of easterly
wind gusts of 40 to 50 mph along the eastern ma coast and up to
60 mph across the CAPE islands. High wind warnings have been
issued for the CAPE islands with wind advisories along the
eastern ma coast. Will have to watch for some downed trees and
isolated to scattered power outages.

Short term 6 am Friday morning through 6 pm Friday
Friday...

the surface low pressure system looks to track near the
southeast new england coast Friday morning. Its associated
closed 700 mb level will also track across the southeast portion
of our region. The result will be periods of rain through Friday
morning... Before coming to an end by afternoon. However... Colder
air wrapping in behind the system may allow for portions of
interior ma especially the high terrain to transition back to
a period of snow. It is possible that some of these areas see an
additional 1 to 3 inches of snow in this region. However... For
the rest of the region temps should remain above freezing with
perhaps just some wet snow flakes mixing in at the end.

Precipitation petty much ends by Friday afternoon and we may
see some peeks of Sun late in the day. Afternoon temps should be
in the 30s to the lower 40s with gusty northwest winds.

Long term Friday night through Thursday
Highlights...

* below average temperatures persist
* weak low pressure brings periods of rain and snow late Sun into
mon
* dry and cold mid week
overview...

the extended forecast features a few high pressure systems sandwiched
around a relatively weak low pressure disturbance or two in the
Sunday night Monday time frame which will bring the return of
both rain and snow chances. Model consensus is good that the
flow pattern becomes much less amplified and more zonal behind
Friday's system, persisting through late weekend. By then a mid
level shortwave digs south, crossing the region Sunday Monday
which will generate a weak surface low in the vicinity of sne
with another round of light snow rain. Beyond this, models
diverge a bit, with the GFS keeping things unsettled into
Tuesday before the high returns, while the euro returns a dry
high pressure more quickly. Either way, by mid to late week
heights begin to rise ever so slightly and a cold and dry
pattern returns.

Details...

Friday night and Saturday...

Friday night the low continues to exit to the northeast, relaxing
the surface pressure gradient as it leaves. Winds will take a good
while to come down, however, and the 30-35 h925 jet doesn't leave
sne until late Saturday. Thus, expecting gusty west winds to persist
through the period, especially over the cape, islands, and waters,
decreasing through the day Saturday. Clearing skies early
Saturday will give way to more clouds as mid level moisture
invades from the west. With good CAA behind the system lows
Friday night dip into the low 30s with wind chills in the 20s.

Highs on Saturday won't get out of the 40s.

Sunday and Monday...

Sunday high pressure sits over the northeast with light winds and
highs in the upper 30s-40s under a cold airmass; should be a mostly
dry day before snow rain chances increase from the west by the
evening overnight hours. The upper trough over canada digs south
helping to generate a surface low in the vicinity of sne which
brings weak fronts through in quick succession Sunday
night Monday. Still expecting mainly snow outside the coastal
plain, with rain along the coasts. QPF amounts are lackluster; a
few hundredths to a few tenths of liquid equivalent.

Tuesday through Thursday...

after the system exits zonal flow returns at the base of a large 500
mb trough over the eastern us Tuesday early Wednesday. Some
disagreement on slight precip chances Tuesday, but overall looks
dry; maybe some showers over the high terrain. By mid week a
surface high returns bringing dry weather. Given the overall
weak longwave trough pattern, cold temperatures will persist
with highs in the 30s and low 40s.

Aviation 21z Thursday through Tuesday
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Friday ...

tonight... Moderate to high confidence. Ifr to lifr conditions
overspread the region from southwest to northeast roughly from
21z through 01z in moderate to heavy snow. The exception will be
the very immediate coast... Where the marine influence will
likely result in a transition quickly over to rain. Across the
rest of the region... Ptype will transition to rain across
eastern ma ri with a period of light icing across the interior
between 02z and 06z. Ifr conditions persist overnight with
temps rising above freezing by 12z... Except for portions of the
interior high terrain in ma.

In addition... A strong easterly LLJ will result in 40 to 50 knot
wind gusts along the coast, strongest of those across the
cape islands.

Friday... Moderate to high confidence. Low end MVFR-ifr
conditions in the morning in mainly rain with any snow ice
confined to interior ma. Precipitation ends by afternoon with
improvement to MVFR and even someVFR conditions possible late.

Kbos terminal... Moderate to high confidence in taf. Snow or a
mixture of rain snow develops around 00z or 01z... But quickly
transitions to all rain by 03z. A coating to 1 inch is possible
on runways before that occurs. Easterly wind gusts of 40 knots
expected overnight.

Kbdl terminal... High confidence in taf. Heavy snow overspreads
the terminal after 21z or 22z. This continues through about 03z
before ptype transitions to a period of sleet freezing rain.

Ptype should then change to all rain after 6z or so.

Outlook Friday night through Tuesday ...

Friday night:VFR. Windy with local gusts to 30 kt.

Saturday through Saturday night:VFR. Breezy.

Sunday: mainlyVFR, with local ifr possible. Slight chance sn.

Sunday night: mainly ifr, with local MVFR possible. Chance sn,
slight chance ra.

Monday: MVFR ifr conditions possible. Breezy. Chance sn, slight
chance ra.

Marine
Forecaster confidence levels...

low - less than 30 percent.

Moderate - 30 to 60 percent.

High - greater than 60 percent.

Short term through Friday ... High confidence.

Tonight... Strong easterly LLJ will result in 50 knot wind gusts
across much of our waters late tonight with strong SCA across
boston harbor narr bay. Seas will build to between 15 and 20
feet across our eastern waters by daybreak Friday. Vsbys reduced
at times in mainly a windswept rain.

Friday... Storm force wind gusts should diminish to gales during
the morning and persist into part of the afternoon with still a
decent pressure gradient in place. Seas will remain very high.

Outlook Friday night through Tuesday ...

Friday night: moderate risk for small craft advisory winds with
local gusts up to 30 kt. Rough seas up to 12 ft.

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

Saturday night: winds less than 25 kt. Areas of seas
approaching 5 ft.

Sunday: winds less than 25 kt. Seas locally approaching 5 ft.

Sunday night: winds less than 25 kt. Slight chance of rain.

Local visibility 1 to 3 nm.

Monday: winds less than 25 kt. Areas of seas approaching 5 ft.

Slight chance of rain.

Hydrology
Renewed river flooding is possible across ri and eastern ma with
0.50 to 1.0 inches of rainfall possible tonight into Friday
after a few inches of snow first. Will have to watch this
closely.

Tides coastal flooding
Astronomical tides are very low (below 9 ft) in boston. Thus
with this upcoming storm worse case scenario would be isolated
minor flooding possible.

Box watches warnings advisories
Ct... Winter storm warning until 7 am est Friday for ctz002>004.

Ma... High wind warning from midnight tonight to 9 am est Friday for
maz022>024.

Winter weather advisory until 1 am est Friday for maz017>021.

Wind advisory from midnight tonight to 9 am est Friday for
maz007-014>016-019.

Winter weather advisory until 2 am est Friday for maz007-
013>016.

Winter storm warning until 7 am est Friday for maz002>006-
008>012-026.

Ri... High wind warning from midnight tonight to 9 am est Friday for
riz008.

Winter weather advisory until 1 am est Friday for riz002>007.

Winter storm warning until 7 am est Friday for riz001.

Marine... Storm warning from midnight tonight to 9 am est Friday for
anz231>235-237-250-254>256.

Gale warning from 10 pm this evening to 4 pm est Friday for
anz230-251.

Gale warning from midnight tonight to 9 am est Friday for
anz236.

Synopsis... Frank bw
near term... Frank
short term... Frank
long term... Bw
aviation... Frank bw
marine... Frank bw
hydrology...

tides coastal flooding...



Weather Reporting Stations
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Nantucket, Nantucket Memorial Airport, MA168 mi72 minE 710.00 miA Few Clouds37°F23°F57%1030.9 hPa

Wind History from ACK (wind in knots)
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Last 24hrNW13
G21
NW16
G22
NW15
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NW20
G28
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N14N15
G24
N14N12N13N13
G19
N12N10N7N6NE6NE5NE9E8E9E8E8E7E9
G16
1 day agoW14NW19
G25
W11W14
G20
NW16
G23
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W13
G19
W12W17
G27
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G25
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NW13
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W12NW16W18
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G24
NW15
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G26
NW15
G21
2 days agoSW8SW4S6S9S8S12SE16SE17SE15SE18
G22
SE16SE16SE16SE18SE21
G28
SE17
G24
SE18
G24
SE18SE18
G26
S25
G32
S24
G39
SW24
G37
SW20
G27
SW18
G26

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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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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.