Wednesday, December12, 2018

Marine Weather and Tides
Point Arena, CA

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 7:14AMSunset 4:53PM Wednesday December 12, 2018 9:10 AM PST (17:10 UTC) Moonrise 11:30AMMoonset 10:10PM Illumination 26% Phase: Waxing Crescent; Moon at 5 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 Point Arena, CA
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location: 36.95, -126.32     debug

Area Discussion for - San Francisco/Monterey Bay Area, CA
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Fxus66 kmtr 121149
area forecast discussion
national weather service san francisco bay area
349 am pst Wed dec 12 2018

Synopsis Dry conditions are forecast to continue across our
region through Thursday night. Daytime temperatures will be mild
while nights will be seasonably cool. A weak weather system will
likely produce light rain on Friday and Friday night, especially
for areas north of the golden gate. Periods of light rain may
continue into Saturday and Saturday night, mainly in the north
bay. A stronger and wetter system is then expected to produce
widespread rain across our entire region Sunday and Sunday night.

Dry weather will likely return by late Monday.

Discussion As of 3:20 am pst Wednesday... A weather system
moving inland to our north brought considerable high clouds to our
region overnight, but no rainfall. Also, areas of low clouds
developed overnight, but only patchy light fog has formed thus
far. Given the amount of cloud cover in place, feel it's unlikely
we will see widespread fog develop prior to sunrise.

The system to our north will move quickly off to the east today
while an upper ridge offshore builds inland over california. After
morning low clouds and fog clear, expect a mostly sunny day except
for occasional high clouds. High temperatures today should be
slightly warmer than yesterday. Mostly clear skies and light winds
will mean chilly conditions tonight with lows dipping into the
lower to mid 30s in the coolest inland valleys. Also, expect
patchy fog again by late tonight, especially in the valleys. The
upper ridge will maintain dry and mild conditions on Thursday,
along with a continued warming trend across the southern portion
of our region where high temperatures will climb into the mid and
upper 60s. Increasing high clouds on Thursday night are expected
to hold temps up a bit.

Rain chances return to our region on Friday when a frontal system
arrives over northern california. Models agree that most rainfall
will hold off until Friday afternoon, but both the NAM and ecmwf
forecast spotty light warm advection rainfall as early as Friday
morning in advance of the main frontal rain band. Models have
come into better agreement with respect to rainfall location and
amounts with this system. Widespread light rain is forecast to
spread across the north bay Friday afternoon and evening, with
only spotty light rain expected across the san francisco peninsula
and east bay, and little or no rain for points south. The front
is forecast to stall and mostly dissipate over the sf bay area by
Friday night. This weak remnant frontal boundary is then expected
to remain draped across the bay area through Saturday and
Saturday night, producing periods of light precipitation, mainly
over the north bay. Rainfall accumulations from Friday through
Saturday night are generally forecast to be a quarter inch or
less, except up to a half inch in the north bay. Most of this rain
will likely fall on Friday afternoon and evening.

The models have consistently indicated that the following system,
due to arrive by Sunday afternoon, will be both stronger and
wetter, producing widespread moderate rainfall across our region
from Sunday afternoon through Sunday night. There could be a brief
period of heavy rain just prior to frontal passage, especially in
the north bay on Sunday afternoon. Rainfall totals with the
Sunday Sunday night system are projected to range from
0.50-1.50", with potentially higher amounts in the north bay.

Gusty south winds are also likely for a short period of time just
ahead of the front on Sunday, with the strongest winds expected
along the north bay coast and in the coastal hills.

Showers may linger into Monday morning, but the models agree that
dry conditions will develop in most areas by Monday afternoon. An
upper ridge is forecast to build in quickly behind the departing
system on Monday and this ridge will likely bring dry and mild
weather to most of our region from late Monday through at least
Thursday of next week. However, the ECMWF indicates that moist
flow over the top of the ridge may result in rain across portions
of the north bay late Monday night and Tuesday.

Aviation As of 3:49 am pst Tuesday... For 12z tafs. A weak,
trailing frontal boundary is presently passing through the san
francisco bay area, bringing with is a mixture of low and high
clouds for many terminals. As of the 12z TAF publication time,
terminals were reporting anywhere from ifr toVFR conditions.

Generally expect either mfvr or ifr ceilings and or visibilities
to prevail in the san francisco bay area through at least sunrise
while monterey bay terminals should remainVFR. A few differences
from yesterday's dense fog event are 1) there is a bit more
mixing at the surface, and 2) the passing high clouds have
prohibited optimal surface radiational cooling. Can't rule out
some drops in visibilities through sunrise in the san francisco
bay area given the near-saturated boundary layer, but the passing
front should help prevent a widespread fog event. The challenge
this morning that was not applicable yesterday is that the high
clouds are obscuring the low clouds on infrared satellite imagery.

Will continue to closely monitor the latest terminal observations
and amend the tafs accordingly. Overall moderate confidence.

Vicinity of ksfo... MVFR ifr ceilings are expected during the
morning hours as a weakening front passes through the area. This
front should help prevent the dense fog from redeveloping like it
did 24 hours ago, but it is concerning that visibilities across
the bay at oakland have dropped as of the 12z TAF publication.

Can't rule out a minor drop in visibilities through sunrise, thus
prompting the introduction of the temporary drop in visibilities
in the 12z taf. Will continue to closely monitor observations and
amend if necessary.

Sfo bridge approach... Similar to ksfo.

Monterey bay terminals...VFR conditions are expected to prevail.

The approaching front has weakened considerably as it pushes
southward, and think the low clouds will generally remain few sct
this morning. Can't rule out a brief opportunity with
visibilities dropping to MVFR levels -- particularly at sns -- but
confidence of occurrence is too low to put in the TAF at this

Marine As of 2:29 am pst Wednesday... Breezy northerly winds
behind a passing cold front will gradually subside later this
afternoon and evening over the coastal waters. Winds will then
become southerly by late Thursday and Friday ahead of a weekend
system. A series of west to northwest swell trains will arrive to
the waters over the coming days, creating hazardous conditions for
small vessels. The most significant long- period swell is
forecast to arrive by late Sunday or Monday, which has the
potential to bring open water swells of 20 feet or more.

Mtr watches warnings advisories
Tday Sca... Pigeon pt to pt pinos 0-10 nm from 3 pm
sca... Pt arena to pt reyes 0-10 nm
sca... Pt reyes to pigeon pt 0-10 nm
sca... Pt pinos to pt piedras blancas 0-10 nm
sca... Pt arena to pigeon pt 10-60 nm
sca... Pigeon pt to pt piedras blancas 10-60 nm
public forecast: dykema
aviation: rowe
marine: rowe
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Wind Forecast for San Francisco/Monterey Bay Area, CA (12,3,4,5)
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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.