Sunday, January24, 2021
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Marine Weather and Tides
Portola Valley, CA

Version 3.4
NOTICE
8/26/2020 The 7 day forecast is taking about 5 seconds to load but it will eventually load. NOAA is still working on it.
8/18/2020 NOAA continues to have trouble. Wind guest will occasionally be left off graphs. I am working with NOAA to resolve the issue.
12/16/2019 NOAA is having trouble with requests that include wind gusts. I am posting graphs without wind gusts until it gets fixed.
10/9/2019 Updated the Marine Zones.
9/4/2019 Fixed the weather maps due to NOAA moving them.
7/25/2019 New feature in the Airports section gives a link to 5 minute updates for data reports.

Sunrise 7:15AMSunset 5:25PM Sunday January 24, 2021 1:17 AM PST (09:17 UTC) Moonrise 1:49PMMoonset 3:56AM Illumination 84% Phase: Waxing Gibbous; Moon at 11 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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PZZ531 San Francisco Bay South Of The Bay Bridge- 907 Pm Pst Sat Jan 23 2021
.small craft advisory in effect from Sunday afternoon through Monday afternoon...
Tonight..NW winds 5 to 15 kt.
Sun..W winds 5 to 15 kt with gusts up to 25 kt. Showers.
Sun night..NW winds 20 to 30 kt with gusts up to 40 kt. Showers likely.
Mon..NW winds 20 to 25 kt with gusts up to 35 kt.
Mon night..NW winds 15 to 25 kt with gusts up to 30 kt.
Tue..SE winds up to 10 kt. A chance of rain.
Tue night..S winds 15 to 20 kt with gusts up to 30 kt. Rain.
Wed..S winds 10 to 20 kt with gusts up to 25 kt. Rain.
Thu..S winds 5 to 10 kt. Rain likely.
PZZ500 907 Pm Pst Sat Jan 23 2021
Synopsis for the central california coast and bays including the Monterey bay..Greater farallones...and cordell bank national marine sanctuaries... A cold front and upper level trough will move quickly southeastward over the coastal waters and bays Sunday. The cold front will result in showers and a slight chance of Thunderstorms. Northwest gales will develop after frontal passage in the afternoon and evening. Gale force gusts are likely over the bays. Strengthening winds will result in a large and steep combined wind wave and swell at 11 to 13 seconds late Sunday and early next week. Hazardous conditions developing due to strengthening winds and steepening seas.


7 Day Forecast for Marine Location Near Portola Valley, CA
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location: 37.36, -122.23     debug


Area Discussion for - San Francisco/Monterey Bay Area, CA
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FXUS66 KMTR 240559 AFDMTR

Area Forecast Discussion National Weather Service San Francisco Bay Area 959 PM PST Sat Jan 23 2021

SYNOPSIS. Widespread light to moderate rainfall is expected Sunday afternoon and evening, along with colder temperatures and lowering snow levels. Gusty northwest winds will follow Sunday night into Monday. A much stronger and wetter system will then impact the region with potentially heavy rain and strong winds from late Tuesday through Thursday. Additional rainfall is possible by next weekend.

DISCUSSION. Forecast remains on track. We continue to focus on the atmospheric river event that is forecast for Tuesday through Thursday. There is increasing confidence that debris flow criteria will be met during this event. If you live on or near a 2020 burn scar then make sure you're thinking through preparedness actions you can take now. If you haven't signed up for your county's alert or reverse 911 system, then do so this weekend. In an abundance of caution, if a local official knocked on your door and told you to evacuate as soon as possible, would you be ready?

PREVIOUS DISCUSSION. as of 12:55 PM PST Saturday . It's going to be a wild ride the next seven days as the active weather pattern continues with potentially the biggest storm of the season midweek. Simply put, details will change over the next few days, but now is the time to prepare for the first notable atmospheric river of the season with greatest concerns on burn areas.

The day started with cloudy skies, some lingering showers, cool temperatures and patchy fog. Despite the cool damp start skies are clearing from N to S. The greatest amount of sunshine is San Francisco northward. To the south, lingering moisture and instability resulted in fair weather cu across the area. Temperatures are still in the 50s and hitting 60 will be a struggle for many spots.

The longwave pattern visible on water vapor imagery shows yesterday's system exiting to the south and the next system upstream near Alaska. No major change in the short term as the next system is ontrack to move southward over the next 12-24 hours. As the happens the chance for precip initially returns to the North Bay early Sunday afternoon before spreading southward. Similar to the last system this one will bring widespread light to moderate precip to the forecast area. There could be some embedded heavier showers, especially given the slight convective nature. Speaking of convection, added a slight chance for thunderstorms over the coastal waters Sunday afternoon/evening. Conf is not high enough to include them overland. Rain will be most widespread with the fropa Sunday afternoon, but then quickly turn to showers behind the front Sunday evening through Monday. Rainfall amounts for the most part will be a few tenths most areas and near one half inch coastal mountains. Just like the last system, enough cold air will be present to lower snow levels with snow possible again over the highest peaks. No major accumulations, but an inch or two are possible over the Santa Lucia Mts and S Gabilan Range.

Once cold advection kicks and post frontal winds ramp up it will get rather gusty over the waters, immediate coastline, coastal peaks with gusts 40-50 mph. Therefore a Wind Advisory will be issued Sunday evening through early Monday morning for the gusty winds. Wind will subside through the day Monday with a few lingering showers possible. Skies will clear and winds dropping off will lead to some chilly temps monday night.

Now for the main event. Features to key in on for an atmospheric river event are the moisture plume (where its focusing/landfall) and timing (progressive or stalling). Earlier model runs were split into two camps:a more progressive pattern pushing the moisture plume through the forecast area and the slower stalling pattern with the moisture plume lasting longer. The 12z model suite has switched again with less progression and more stalling, especially with the GFS and ECMWF. The ECMWF is now trending to push the plume of moisture into the North Bay Tuesday night and then slowly moving southward toward Big Sur Wednesday and stalling/inching back northward toward Santa Cruz Wednesday evening/night. In the general sense the GFS is similar with a slower/stalling moisture plume. It's still several days out and one cannot focus too much on specific details as they'll like change. However, confidence is much higher that a moderate to heavy rain event will impact the Bay Area Tuesday night through Thursday. Rainfall will be widespread with a few inches possible for lower elevations, but five inches plus likely for the coastal mountains like Santa Cruz and Big Sur. If in fact there is more stalling of the plume rainfall amounts could approach ten inches over the event in the higher terrain. Obviously the greatest concerns will be any type of flooding, especially on recent burn areas with debris floods. In addition to rain, expect strong and gusty winds at times through the event.

The atmospheric river moves south by Friday, but models show additional rainfall chances are possible with additional system next weekend.

Lastly, please monitor the forecast and our social media feeds the next few days as forecast update get published and details become more clear.

AVIATION. as of 9:59 PM PST Saturday . For the 06Z TAFs. VFR with patchy evening low clouds, patchy fog /VLIFR-IFR/ developing tonight and Sunday morning. By mid to late Sunday morning ceilings deteriorating with rain arriving midday to late Sunday and scattered showers for the overnight hours.

Vicinity of KSFO . VFR-MVFR tonight and Sunday. Deteriorating conditions by midday Sunday with gusty winds and rain developing. Scattered showers Sunday night and Monday morning.

SFO Bridge Approach . Similar to KSFO.

Monterey Bay Terminals . VFR, ceilings lowering to MVFR tonight and Sunday. Rain developing Sunday in the mid to late afternoon. Showers Sunday night and Monday morning.

MARINE. as of 9:38 PM PST Saturday . A cold front and upper level trough will move quickly southeastward over the coastal waters and bays Sunday. The cold front will result in showers and a slight chance of thunderstorms. Northwest gales will develop after frontal passage in the afternoon and evening. Gale force gusts are likely over the bays. Strengthening winds will result in a large and steep combined wind wave and swell at 11 to 13 seconds late Sunday and early next week. Hazardous conditions developing due to strengthening winds and steepening seas.

MTR WATCHES/WARNINGS/ADVISORIES. Tngt. SCA . Pt Arena to Pt Reyes 0-10 nm SCA . Pt Reyes to Pigeon Pt 0-10 nm SCA . Pigeon Pt to Pt Pinos 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: MM/BB AVIATION/MARINE: Canepa

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Weather Reporting Stations
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Stations Dist Age Wind Air TempWater Temp WavesPressureDewPt
RTYC1 - 9414523 - Redwood City, CA 10 mi47 min SE 2.9 G 4.1 43°F 54°F1014.9 hPa
AAMC1 - 9414750 - Alameda, CA 29 mi47 min E 4.1 G 5.1 47°F 53°F1014.4 hPa
LNDC1 30 mi47 min ESE 6 G 7 48°F 1014.1 hPa
PXOC1 - 9414311 - San Francisco (Pier 1), CA 31 mi47 min E 7 G 8.9 48°F 1013 hPa
OMHC1 - 9414769 - Oakland Middle Harbor Met, CA 31 mi47 min ESE 6 G 8
OBXC1 31 mi47 min 48°F 48°F
46269 31 mi47 min 44°F 53°F5 ft
OKXC1 - 9414776 - Oakland (Berth 34), CA 32 mi47 min SE 2.9 G 7 47°F 1014.3 hPa
PXSC1 32 mi47 min 49°F 49°F
FTPC1 - 9414290 - San Francisco, CA 33 mi47 min Calm G 1.9 46°F 53°F1014.4 hPa
46012 - HALF MOON BAY - 24NM South Southwest of San Francisco, CA 35 mi27 min NNW 16 G 21 51°F 11 ft1015.5 hPa47°F
46237 - San Francisco Bar, CA (142) 36 mi47 min 52°F6 ft
PPXC1 - 9414847 - Richmond (Point Potrero), CA 38 mi47 min SE 6 G 8.9 49°F 1014.5 hPa
TIBC1 - Tiburon Pier, San Francisco Bay, CA 39 mi96 min Calm 46°F 1014 hPa
RCMC1 - 9414863 - Richmond, CA 40 mi47 min SE 4.1 G 5.1 50°F 53°F1014.1 hPa
46042 - MONTEREY - 27NM West of Monterey Bay, CA 41 mi27 min NW 9.7 G 16 52°F 55°F11 ft1015.1 hPa47°F
46026 - SAN FRANCISCO - 18NM West of San Francisco, CA 42 mi27 min NW 19 G 23 53°F9 ft1014.8 hPa
46092 - MBM1 43 mi80 min NW 7.8 51°F 53°F1014.5 hPa (+0.7)
MLSC1 - Moss Landing, South Harbor, CA 45 mi47 min 54°F
ELXC1 - Elkhorn Slough Reserve, CA 46 mi92 min ESE 1 42°F 1014 hPa41°F
46114 - West Monterey Bay, CA 46 mi21 min 55°F11 ft
MZXC1 - 9415102 - Martinez-Amorco CA 47 mi47 min WNW 2.9 G 4.1 48°F 52°F1014 hPa
UPBC1 47 mi47 min WNW 5.1 G 6
DPXC1 - 9415141 - Davis Point, San Pablo Bay, CA 48 mi47 min WSW 2.9 G 4.1 46°F 1013.7 hPa
PCOC1 - 9415144 - Port Chicago, CA 49 mi47 min SSW 8 G 11 43°F 51°F1013.6 hPa

Wind History for Redwood City, CA
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Airport Reports
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AirportDistAgeWind ktVisibilitySky/WeatherTempDewPtHumidityPressure
Palo Alto Airport, CA10 mi4.5 hrsSSE 310.00 miClear45°F39°F81%1014.9 hPa
Mountain View, Moffett Field, CA11 mi27 minN 010.00 miFair41°F39°F93%1014.6 hPa
San Carlos Airport, CA12 mi22 minno data10.00 miFair41°F39°F93%1014.9 hPa
San Jose, San Jose International Airport, CA16 mi24 minS 410.00 miFair42°F37°F82%1014.4 hPa
Half Moon Bay Airport, CA18 mi22 minN 07.00 miOvercast41°F41°F100%1015.2 hPa
San Francisco, San Francisco International Airport, CA19 mi21 minN 010.00 miA Few Clouds47°F42°F83%1014.4 hPa
Hayward, Hayward Air Terminal, CA22 mi23 minN 010.00 miFair41°F37°F86%1015.4 hPa
San Jose / Reid / Hillv, CA22 mi3.5 hrsN 010.00 miClear43°F37°F81%1015.2 hPa
Oakland, Metro Oakland International Airport, CA23 mi24 minE 410.00 miA Few Clouds44°F39°F83%1014.8 hPa

Link to 5 minute data for KPAO

Wind History from PAO (wind in knots)
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Last 24hr------------------N55N7NW6N4NW8NW8NW9--------CalmCalmS3
1 day ago------------------443--SW5SW9--SW9SW5--Calm4W5--Calm
2 days ago------------------CalmCalm------N5NW10--NW8NW8----------

Tide / Current Tables for Palo Alto Yacht Harbor, California
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Palo Alto Yacht Harbor
Click for Map
Sun -- 03:55 AM PST     Moonset
Sun -- 04:02 AM PST     3.31 feet Low Tide
Sun -- 07:17 AM PST     Sunrise
Sun -- 09:05 AM PST     8.49 feet High Tide
Sun -- 01:48 PM PST     Moonrise
Sun -- 04:46 PM PST     0.10 feet Low Tide
Sun -- 05:24 PM PST     Sunset
Sun -- 10:45 PM PST     6.10 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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5.454.33.73.33.74.96.67.98.58.17.15.84.32.91.40.40.10.92.345.366.1

Tide / Current Tables for Dumbarton Hwy Bridge, South San Francisco Bay, California Current
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Dumbarton Hwy Bridge
Click for Map
Sun -- 01:04 AM PST     -0.43 knots Max Ebb
Sun -- 03:53 AM PST     0.00 knots Slack
Sun -- 03:55 AM PST     Moonset
Sun -- 06:54 AM PST     1.02 knots Max Flood
Sun -- 07:17 AM PST     Sunrise
Sun -- 09:32 AM PST     -0.00 knots Slack
Sun -- 01:19 PM PST     -1.19 knots Max Ebb
Sun -- 01:48 PM PST     Moonrise
Sun -- 05:02 PM PST     0.01 knots Slack
Sun -- 05:24 PM PST     Sunset
Sun -- 08:23 PM PST     1.50 knots Max Flood
Sun -- 11:23 PM PST     -0.00 knots Slack
Tide / Current data from XTide NOT FOR NAVIGATION
Sorry tide depth graphs only, please select another station.

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-0.4-0.4-0.4-0.200.50.910.80.4-0.2-0.6-1-1.2-1.1-0.9-0.6-00.71.21.51.410.3

Weather Map
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wmap_P
GEOS Local Image of CentralWestCoast    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

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Ground Weather Radar Station




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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 numerous 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.