Marine Weather and Tides
1/26/2021 -- The West Coast Satellite images havd been updated. They now use GEOS-17.
1/1/2021 -- The 7 day forecast are now working well. Thank you NOAA for your support.
|Sunrise 6:01AM||Sunset 8:10PM||Tuesday May 11, 2021 2:57 AM PDT (09:57 UTC)||Moonrise 5:27AM||Moonset 7:34PM||Illumination 0%|
7 Day Forecast for Marine Location Near Point Arena, CAHourly EDIT Help
Area Discussion for - San Francisco/Monterey Bay Area, CA  (on/off)  Help NOTE: mouseover dotted underlined text for definition
FXUS66 KMTR 110532 AFDMTR
Area Forecast Discussion National Weather Service San Francisco Bay Area 1032 PM PDT Mon May 10 2021
SYNOPSIS. A Red Flag Warning remains in effect through 6 pm Tuesday for the North and East Bay Hills as well as the East Bay Interior Valleys. Otherwise, expect continued sunny and warm weather through Tuesday. A cooling trend begins Wednesday and lasts through the end of the week and into next weekend as the marine layer develops and also deepens, and as onshore winds prevail.
DISCUSSION. As of 8:55 PM PDT Monday . Another pulse of offshore winds in the hills last night and today brought more dry air into our region and also limited the strength of onshore flow near sea level. Also, a building upper ridge centered just off the West Coast warmed the airmass aloft. These developments resulted in very warm temperatures regionwide today, except for areas near the ocean. Persistent northwest winds over our coastal waters is maintaining strong upwelling and thus cold near-shore ocean waters (sea surface temps mostly in the lower 50s). Thus, areas in very close proximity to the ocean posted highs only in the 50s and 60s today, while low to mid 80s occurred not all that far away around San Francisco Bay. Most inland areas had highs ranging from the mid 80s to mid 90s. Three Bay Area locations tied daily high temperature records today including Napa (94), Richmond (88), and SFO Airport (84).
Offshore winds in the hills have been subsiding since midday and most locations are currently reporting wind gusts of 25 mph or less. Although models have been backing off on forecast wind speeds in the hills tonight, higher elevation winds are still expected to increase once again by late this evening. Even moderate offshore winds combined with little or no humidity recovery will maintain critical fire weather conditions across portions of the North and East Bay, especially when factoring in the record dry fuels for this time of year. In addition, very warm and very dry conditions will persist inland into Tuesday. See Fire Weather Discussion below for details.
Offshore winds in the hills are expected to decrease significantly by mid morning Tuesday and this should allow for a modest increase in marine air influence near the ocean and bays tomorrow, as well as in the coastal valleys, as low level onshore flow starts to ramp up. Also, it's likely we'll see an increase in low clouds and fog along the immediate coast by late in the day. However, the upper ridge is forecast to shift eastward and strengthen further over California by tomorrow. Thus, although coastal areas will likely experience modest cooling tomorrow, most inland valleys will remain very warm, as will the hills.
By Wednesday the upper ridge will flatten and its axis will shift inland, resulting in the redevelopment of widespread onshore flow. Expect cooling to develop in all but the valleys farthest inland on Wednesday. Models agree that by late in the week a trough will deepen along the West Coast, eventually forming a closed upper low over the Bay Area by late Friday night or Saturday morning. Thus, we can expect a deepening marine layer late in the week, along with temperatures cooling close to seasonal averages by Thursday and then slightly below average by Friday. The upper low will have a very limited amount of moisture at its disposal and so it's not a surprise that nearly all GFS and ECMWF ensemble members maintain dry conditions across our area through the weekend. Daytime highs next weekend are forecast to be mostly in the 60s and 70s.
AVIATION. As of 10:31 PM PDT Monday . For the 06z TAFs. VFR conditions around the Bay Area and the Central Coast. There is small "slug" of stratus crawling up the Monterey Bay into Santa Cruz that will be monitored, but otherwise, light winds and clear skies is expected overnight. LLWS was removed from most of the TAF sites, expect KAPC and KLVK, as the obs just are verifying it and most models have really pared it down to the far eastern portions of the forecast area. VFR expected on Tuesday with onshore breezy winds, stronger through coastal gaps up to 20 kts. Winds subside Tuesday right as skies remain mostly clear, with stratus returning to the Monterey Bay.
Vicinity of KSFO . Winds remain breezy from 10 to 15 kts, but beginning to diminish. VFR forecast through the TAF period. Winds will increase during the day, but as the large scale pattern breaks down, winds will be tamer than recent, up to 20 kts, staying breezy through the end of the TAF period.
SFO Bridge Approach . Similar to KSFO.
Monterey Bay Terminals . Obs suggesting that KSNS is IFR, yet satellite has most of the stratus drifting north toward Santa Cruz. Likely that the onshore flow is pushing sea spray/salt over the ceilometer suggesting there is a cloud deck. The stratus will be monitored as most hi-res models suggest it will come back into peninsula terminals after 12Z for a more robust return to IFR. But it should clear between 16 and 17Z. VFR Tuesday with breezy onshore winds. Stratus returns to terminals after 01Z Tuesday night, with a farther push toward the Salinas Valley at the end of the TAF period.
FIRE WEATHER. As of 4:00 PM PDT Monday . Red Flag Warning remains in effect through 6 pm Tuesday for zones 507/510/511. Winds in the hills subsided somewhat on Monday afternoon, but were still gusting between 25 and 35 mph while RH values have dropped as low as the teens. Offshore winds in the hills are forecast to increase once again tonight, although models have backed off on wind speeds tonight. In any case, a reinforcing burst of dry air arriving late this afternoon and evening will result in little or no RH recovery overnight. Very dry air, combined with moderate offshore winds in the hills, will maintain critical fire weather conditions into Tuesday morning. Winds will subside by mid morning Tuesday, but warm and very dry conditions will persist through the afternoon hours with RH values dropping as low as the single digits.
Onshore breezes should return to all areas by Tuesday evening. Moderating conditions are forecast into Weds in terms of cooler temps and an uptick in humidity. A cooling trend will continue through the end of the week with temps and humidity returning to more seasonal values.
MARINE. as of 09:00 PM PDT Monday . Current observations show winds to have diminished over most of the central and southern outer and coastal waters. Seas will take longer to diminish, which could still create isolated areas of hazardous seas for smaller vessels. Seas will continue quiet down through Tuesday morning. Winds are still elevated over the northern waters. Light winds will persist mid to late week before re- strengthening into the weekend as the next system moves through. The sea state continues to be dominated by wind driven northwest waves. A pair of light northwest and southerly swells persist throughout the forecast period.
MTR WATCHES/WARNINGS/ADVISORIES. Tngt. Red Flag Warning . CAZ507-510-511 SCA . Pt Arena to Pt Reyes 0-10 nm until 3 AM SCA . Pt Arena to Pigeon Pt 10-60 nm
PUBLIC FORECAST: Dykema AVIATION: DK MARINE: Dhuyvetter FIRE WEATHER: Dykema
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