San Francisco Bay north of the Bay Bridge, including San Pablo Bay, Suisun Bay, and West Delta, CA Marine Forecast
| Today...Se Wind 5 To 10 Kt, Becoming S 10 To 15 Kt Early This Afternoon, Then Becoming Sw 5 To 10 Kt Late. Rain Likely. |
| Tonight...W Wind 5 To 10 Kt. A Chance Of Rain. |
| Thu...W Wind 5 To 10 Kt, Rising To 10 To 15 Kt In The Afternoon. A Slight Chance Of Rain In The Morning. |
| Thu Night...W Wind 10 To 15 Kt. |
| Fri...W Wind 5 To 10 Kt. |
| Fri Night...W Wind 10 To 15 Kt, Easing To 5 To 10 Kt After Midnight. |
| Sat...W Wind 5 To 10 Kt. |
| Sat Night...W Wind 5 To 10 Kt, Becoming Sw After Midnight. |
| Sun...Sw Wind Around 5 Kt. |
| Sun Night...Sw Wind 5 To 10 Kt. |
| Area Forecast Discussion National Weather Service San Francisco CA 1103am PDT Wednesday Oct 1 2025 Issued at 851am PDT Wednesday Oct 1 2025 Overcast skies and scattered showers remain through the day with some slight slowing in the frontal passage. Some slight adjustments will be needed to be made in the spread of rainfall in the forecast package, otherwise the forecast remains on track. -Murdock .SHORT TERM... Issued at 1213am PDT Wednesday Oct 1 2025 (Today and tonight) Light rain showers are ongoing across the Bay Area ahead of a cold front located about 200 miles west of San Francisco. This front is connected to a mature, cut off low pressure system way up in the southern Gulf of Alaska. This separation from the parent low is causing a very slow forward progression of the cold front. A ribbon of moisture on the latest water vapor imagery is already showing signs of stalling. As a result, the prefrontal rain will continue through the day. Fortunately the rain intensity looks to remain light outside of a mid day shower or two in the North Bay. The West-WRF ensemble shows, within 1 standard deviation, the IVT will remain between 250-500 kg of water vapor per meter per second today. Thunderstorm chances are less than 10% today. The lapse rates are pretty weak (around 5-6 C/km). With the upper level low so far removed from the surface front, there is a notable lack of cold air aloft needed to create the necessary buoyancy. Based on the 00Z sounding, the 850-500 mb lapse rate is 5.0 C/km, which is actually in the bottom 10th percentile for this time of year. The 850 temp isn't the problem (9.35 C, close the bottom 10th percentile), but the 500 mb temp (-11.75C) is close to the median for this time of year. Furthermore, the slow motion of the cold front doesn't support robust updrafts. Finally, most of the current showers are below the 12,500 foot freezing level, limiting the amount of ice particles necessary for the charge buildup in thunderstorms. When all is said and done we're expecting up to 1" in the coastal mountains of the North Bay with up to 1/4" across the Bay Area and 1/10" across the Central Coast. With the rain spread out over the day, this is mostly a beneficial event and will help put a damper on fire season. Long Term Issued at 1213am PDT Wednesday Oct 1 2025 (Thursday through Tuesday) The prefrontal rain will finally taper off by Thursday morning as the moisture plume slides south. The associated 500 mb trough will swing through Thursday-Friday. This will cause winds to shift from SW to NW, and may support some convection each afternoon, though the lack of moisture will be a major limiting factor for thunderstorm development. This trough will bring lower surface pressure to southern California. Meanwhile higher surface pressure will build over the northern Rockies through the weekend. The gradient across the pressure field will support some northerly, offshore wind from Saturday - Monday. Typically these winds pose a fire weather concern. Fortunately the antecedent conditions and wind strength are mitigating factors. The PGE-WRF ensemble shows the SFO-WMC gradient bottoming out around -2 to -6 mb. Enough for offshore winds, but not a particularly strong event. Marine (Today through Monday) Issued at 851am PDT Wednesday Oct 1 2025 Scattered showers continue across the coastal waters through late tonight. A moderate to rough northwest swell associated with this system arrives tonight and will bring waves between 10 to 11 feet across the outer waters. Wave heigheights will diminish below 10 feet Thursday and Friday before building again late weekend into next week. Winds are expected to strengthen to fresh to strong on Friday resulting in a continuation of rough seas and hazardous conditions for small crafts into the weekend. NOAA San Francisco Bay Area Office: Watches - Warnings - Advisories CA...None. PZ...Small Craft Advisory from 9pm Thursday to 9am PDT Friday for Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory from 3pm Thursday to 9am PDT Friday for Pt Pinos to Pt Piedras Blancas 0-10 nm. Small Craft Advisory until 3pm PDT Thursday for Pt Arena to Pt Reyes 10-60 NM. Small Craft Advisory from 3pm this afternoon to 9am PDT Thursday for Pigeon Pt to Pt Pinos 10-60 NM. Small Craft Advisory from 3am to 9am PDT Friday for Pigeon Pt to Pt Pinos 10-60 NM. x.com/nwsbayarea |
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