San Francisco Bay South of the Bay Bridge Marine Forecast
|Tonight...W Winds 10 To 15 Kt, Becoming Sw Around 5 Kt After Midnight.|
|Tue...S Winds 10 To 15 Kt.|
|Tue Night...Se Winds 15 To 20 Kt With Gusts Up To 25 Kt. Rain.|
|Wed...S Winds 10 To 15 Kt. Rain.|
|Wed Night...Se Winds 5 To 10 Kt. Rain.|
|Thu...W Winds 5 To 10 Kt. Patchy Fog. Rain.|
|Thu Night...S Winds 5 To 10 Kt. Rain.|
|Fri...Sw Winds 5 To 10 Kt. Rain.|
|Sat...Sw Winds 10 To 15 Kt. Rain Likely.|
| 305 PM PDT Mon Oct 18 2021 |
Synopsis for the Central California Coast and Bays Including the Monterey Bay, Greater Farallones and Cordell Bank National Marine Sanctuaries - PZZ500
Winds will remain light to breezy into Tuesday morning. Winds then increase Tuesday night as the next front moves over the waters, increasing the chances for scattered showers into Wednesday morning. These winds will shift to the south and strengthen with gale force gusts possible over the northern outer waters. These winds will generate steep waves resulting in hazardous seas conditions, particularly for smaller vessels. Southerly winds will ease Wednesday and then persist through much of the forecast period with another chance for rain on Thursday, as the unsettled weather pattern continues into the weekend. As weak southerly swell remains embedded in a northwest swell, the primary swell pivots to more westerly by mid week.
| Area Forecast Discussion|
National Weather Service San Francisco Bay Area
151pm PDT Monday Oct 18 2021
Cooler conditions persist this week with rain chances returning Tuesday. Additional rain chances will arrive Thursday evening and again next weekend.
As of 01:50pm PDT Monday...Moist flow over the region and daytime heating has resulted in ample cumulus clouds over the Bay Area this afternoon. A few of the stronger cumulus build ups has actually resulted in lingering showers over the coastal waters and higher terrain south of San Francisco. The forecast will keep a mention of isolated showers through this afternoon. Expect little to no accumulation with the lingering showers.
Once these showers end the Bay Area will see a brief break as an upstream upper level ridge moves overhead. Dry conditions are expected through Tuesday afternoon. The next round of rainfall is expected by Tuesday evening as a cold front moves S and E. The front is currently offshore from the PacNW Coast with a low spinning in the Gulf of AK. Unlike the last frontal passage the Tuesday into Wednesday frontal passage will have more moisture to work with. Latest models pull in some rather high PWATs (Precipitable Waters) exceeding an inch as well. Additionally some of the Atmospheric Guidance now shows a weak to moderate AR. In fact, the frontal passage looks to move S into the Bay Area Tuesday evening, then drift southward by early Wednesday, stall and gradually lift northward Thursday. While all of this happens the higher PWATs (Precipitable Waters) continue to stream inland. Needless to say, rainfall totals have been nudged upward from previous forecast. Rainfall amounts Tuesday afternoon through Thursday: up to 2.5-3.5" N Bay Mountains, N Bay Valleys 1.5-2.0", SF, E Bay and S Bay 0.25-0.75", elsewhere less than 0.25".
Another low pressure and associated cold front will impact the region late Thursday into Friday. The 18Z GFS is all in with this system bringing a good shot of rain to the region, but other models are not as pronounced. For now will keep rain in the forecast, but may need to up rainfall totals for Friday if models keep trending wetter. Rainfall looks to be highest over the N Bay again and little rainfall over interior Monterey/San Benito.
Potentially a brief break in the rain early Saturday before yet another system brings even more rain to the region. Rain chances return by Saturday afternoon/evening to the N before spreading S over the region. Early indications the late weekend system will have the most moisture from an AR perspective. There are differing details, but models do bring the moisture tongue down the coast with a good shot of rain likely Sunday into Monday.
These amounts will definitely change, but the seven day rainfall totals look pretty good for the Bay Area: N Bay 5-8", SF, E and S Bay 1-3", Santa Cruz Mts 3-5", and areas southward 0.5-1.5".
All in all this could stick a fork in fire weather concerns for most of the forecast area (not interior Monterey/San Benito).
as of 08:39am PDT Monday...Moderate post-frontal northwest winds prevail on Monday. The next front with additional rain chances approaches the waters on Tuesday afternoon, causing the winds to shift to the south, strengthening Tuesday night into Wednesday morning when gale force gusts will be possible over the northern outer waters. These winds will generate steep waves resulting in hazardous seas conditions, particularly for smaller vessels. Southerly winds will ease Wednesday and then persist through much of the forecast period. Seas remain out of the northwest with a weaker southerly swell. The primary swell will shift to more westerly by mid week.
NOAA San Francisco Bay Area Office: Watches - Warnings - Advisories