Monday, March27, 2017

Marine Weather and Tides
Attu Station, AK

Version 3.4
What's New / NOTES
5/19/2016 - There were issues with the 3 day airport observation history. I switched to another data source. Let me know if you see any issues with the data feeds.
3/12/2015 - Added section for Gulf current for users in the GMZ marine zones.
This was requested by a user. If you have requests, please let me know.

Sunrise 6:18AMSunset 6:33PM Tuesday March 28, 2017 12:26 PM ChST (02:26 UTC) Moonrise 5:27AMMoonset 5:50PM Illumination 0% Phase: New Moon; Moon at 1 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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PKZ176 SEguam Island To Adak Pacific Side- 347 Pm Akdt Mon Mar 27 2017
.small craft advisory through Tuesday night...
Tonight..NE wind 25 kt. Seas 14 ft.
Tue..E wind 20 kt. Seas 10 ft.
Tue night..E wind 25 kt. Seas 8 ft.
Wed..NE wind 35 kt. Seas 14 ft.
Wed night..NE wind 40 kt. Seas 18 ft.
Thu..N wind 35 kt. Seas 19 ft.
Fri..N wind 20 kt. Seas 12 ft.
Sat..N wind 20 kt. Seas 2 ft.

7 Day Forecast for Marine Location Near Attu Station, AK
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location: 52.84, 173.2     debug

Area Discussion for -
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Fxak68 pafc 280040
southcentral and southwest alaska forecast discussion
national weather service anchorage ak
440 pm akdt Mon mar 27 2017

Analysis and upper levels
The large scale pattern continues to shift as a closed upper level
high over the central bering sea slowly weakens and retrogrades
west. An upper level trough is now firmly entrenched over
mainland alaska and the north pacific, supported by a robust
subtropical jet. A series of lows are strung out south of the
aleutian islands and on up into the gulf of alaska. A weak
compact low over the northern gulf of alaska is producing light
snow today, primarily in the prince william sound region, though
some snow may make it over the coastal mountains. The focus of the
forecast is with the complex low pressure system south of the
alaska peninsula. A developing triple point low is headed
north into the gulf of alaska with an already established low
over the north pacific beginning to curve northeast toward the
gulf of alaska. These two systems will be the major players in
producing widespread snow across south central alaska the next
couple days.

Model discussion
There has been quite a bit of spread in handling of lows crossing
the gulf of alaska. The 12z model runs are grouped closer
together, with a median track of the next two lows toward western
prince william sound. Ensembles also support this general idea.

The NAM is the one notable outlier with a farther east track and
will be ignored. Based on increasing confidence in the general low
track, we will aggressively increase the probability of snow for
much of the area, including the population centers of anchorage
and the matanuska valley. Confidence in the location of heavier
precipitation with these systems is low. Thus, we will remain
conservative with snow accumulation forecast for now.

Panc... There is increasing confidence in development of MVFR
conditions as snow moves in on Tuesday. There is still quite a bit
of uncertainty in the exact track of lows crossing the gulf of
alaska which will greatly affect the intensity of snowfall. If
heavier snow does develop we could easily see ifr/lifr conditions
Tuesday night into Wednesday.

Short term forecast southcentral alaska (days 1 and 2)
The current low over the northern gulf of alaska will dissipate
as it heads inland across the kenai peninsula tonight. The bulk of
snow will remain in the prince william sound area this afternoon
through this evening, then tapering off after that. Low level dry
air is the limiting factor for snowfall as moisture advects across
the coastal mountain ranges to the rest of south central alaska.

We have generally stuck with chance or slight chance for these
inland areas. If snow does fall it will be light with little or no

More significant and widespread snowfall is on tap for Tuesday
through Wednesday. The latest model guidance is beginning to lock
into some very favorable features for snowfall including a series
of fairly weak lows moving up from the gulf of alaska to prince
william sound area, a strongly negatively tilted upper level
trough, and cold air advection from the bering sea to the gulf of
alaska and south central alaska. The question of the day is
"where will the surface lows track to?". This is the key to
determining how much snow will fall and how long it will fall.

Based on model trends, the latest forecast will lean pretty
heavily toward a low track to western prince william sound, which
would bring a long duration snow event to prince william sound,
the eastern kenai peninsula, anchorage, and portions of the
matanuska and susitna valleys. This would all change with a small
shift in low track.

Although we have trended up with the likelihood of snow across
the region, we have gone with a conservative snowfall
accumulation forecast until there is more confidence in the low
track. For now, the big message is that the weeks of dry weather
for much of the region are coming to an end and people should
prepare for a return to winter weather and winter driving

Short term forecast southwest alaska (days 1 and 2)
The forecast period commences with a surface low 200 miles south
of dutch harbor resulting in widespread easterly winds from the
kenai peninsula to attu island. As time elapses expect the low to
drop south taking the enhanced pressure gradient force winds with
it shifting the strongest gusts to the east followed by a brief
stint of northerly winds. By Tuesday night a new low will enter
the gulf of alaska resulting in gale force winds and increased
chance of precipitation.

Short term forecast bering sea/aleutians (days 1 and 2)
The blocking pattern over the bering sea which has been in place
most of march will finally break down over this forecast period.

By day two anticipate stormy conditions to move into the western
portion of the bering sea and aleutians complete with a spike in
precipitable water and easterly gusts.

Long term forecast (days 3 through 7)
The extended forecast looks to be quite an active one for much of
alaska. Starting late Wednesday into Thursday, an upper level
trough extending over the bering sea and northern pacific ocean
will continue to amplify and elongate as an influx of energy from
the coast of russia moves into the pacific ocean. As the trough
amplifies, a warmer and more moist air mass originating in the
subtropics will begin to be advected north toward the gulf coast
of alaska. While models have struggled recently with the pattern
change, models are in near lock-step through Friday before some
discrepancies begin to develop.

The big story on Thursday and Friday will be a powerful low
pressure system moving north toward the alaska peninsula which
will likely slam the gulf coast with a mixture of rain and snow.

Model guidance shows surface to 500 mb thicknesses increasing and
850 mb temperatures approaching 0 degrees c which indicates a
change to rainfall along the coast. However, interior locations
that see precipitation will likely remain snow. The low track will
be important as this far west track will likely keep anchorage
and normal downsloped locations on the dry side. Heading into the
weekend, models begin to struggle with the orientation of the
upper level trough as the ECMWF tries to flatten the trough out
which brings all the energy toward juneau while the GFS keeps the
energy in the gulf of alaska. The take-away story here is that
this active pattern looks to be here to stay for the next 7 to 10
days but it's difficult to see as of now which areas may see the
most rainfall/snowfall. Stay tuned.

Afc watches/warnings/advisories
Public... None.

Marine... None.

Synopsis and model discussion... Sb
southcentral alaska... Cb
southwest alaska/bering sea/aleutians... Ps/dek
long term... Mc

Weather Reporting Stations
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Airport Reports
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Tide / Current Tables for Massacre Bay, Attu Island, Alaska
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Massacre Bay
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Mon -- 06:39 AM HDT     2.31 feet High Tide
Mon -- 09:11 AM HDT     Sunrise
Mon -- 09:27 AM HDT     Moonrise
Mon -- 12:23 PM HDT     1.16 feet Low Tide
Mon -- 05:59 PM HDT     New Moon
Mon -- 06:19 PM HDT     2.42 feet High Tide
Mon -- 09:49 PM HDT     Moonset
Mon -- 09:54 PM HDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
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Tide / Current Tables for Chichagof Harbor, Attu Island, Alaska
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Chichagof Harbor
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Mon -- 12:14 AM HDT     0.56 feet Low Tide
Mon -- 06:52 AM HDT     2.52 feet High Tide
Mon -- 09:11 AM HDT     Sunrise
Mon -- 09:27 AM HDT     Moonrise
Mon -- 12:39 PM HDT     1.26 feet Low Tide
Mon -- 05:59 PM HDT     New Moon
Mon -- 06:32 PM HDT     2.64 feet High Tide
Mon -- 09:49 PM HDT     Moonset
Mon -- 09:54 PM HDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

Weather Map and Satellite Images
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Weather Map
IR Satellite Image from GEOS

GOES Local Image of Puerto Rico    EDIT

Wind Forecast for (22,6,7,8)
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Ground Weather Radar Station Anderson AFB, Guam
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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.