San Francisco Bay north of the Bay Bridge, including San Pablo Bay, Suisun Bay, and West Delta, CA Marine Forecast
|Today...Sw Winds 10 To 20 Kt. A Chance Of Rain.|
|Tonight...S Winds 5 To 15 Kt. Rain Likely.|
|Tue...S Winds 10 To 20 Kt With Gusts Up To 25 Kt. Showers And A Slight Chance Of Thunderstorms.|
|Tue Night...Sw Winds 5 To 15 Kt. Rain.|
|Wed...S Winds Up To 10 Kt. Showers And A Slight Chance Of Thunderstorms.|
|Wed Night...Ne Winds 5 To 10 Kt.|
|Thu...Nw Winds Up To 10 Kt.|
|Fri...Nw Winds Up To 10 Kt. Winds And Wind Waves Higher In And Near Thunderstorms.|
|858 AM PST Mon Mar 8 2021 .Synopsis for the Central California Coast and Bays Including the Monterey Bay...Greater Farallones...and Cordell Bank National Marine Sanctuaries... West to southwest winds will prevail this morning ahead of a weak frontal boundary that will push through the waters midday. Moderate winds will accompany this frontal passage with winds briefly turning W in the wake of the front, then returning to the SW tonight into early Tuesday as a secondary front approaches from the north. Increasing W winds are forecast by late Tuesday before weakening NW to N winds return through Wednesday. A large northwest swell train is arriving in the waters this morning and will bring seas in excess of 10 feet (locally above 15 feet) today, resulting in hazardous small craft across the waters. In addition, thunderstorms are possible over the water on Tuesday.|
| Area Forecast Discussion|
National Weather Service San Francisco Bay Area
1003am PST Monday Mar 8 2021
An offshore low will start to bring rain to the region Monday afternoon/evening. Cool and showery weather will continue through Wednesday as the low moves inland. There is potential for thunderstorms on Tuesday and Wednesday with lightning, gusty winds, and small hail. Drier and warmer conditions are forecast later in the week.
as of 09:02am PST Monday...Overnight cloud cover prevented temperatures from getting as cold as the previous night, but some interior areas still fell into the 30s. Today will offer more cloud cover with highs mostly 50s ahead of the initial rain chances. The track of these showers remains largely unchanged since the previous discussion. The main focus of the afternoon forecast update will be fine-tuning Tuesday's convection chances and snow levels, as well as adjusting the timing of the last chances for rain on Wednesday.
passed through the region overnight resulting in a few high clouds. Despite the cold front temperatures are running a few degrees warmer than Sunday morning due to high clouds and a more mixed atmosphere. Interior valleys will still reach the 30s, but less likely to see spots hit freezing or sub-freezing temperatures. After a pleasant weekend weather wise today will kick off a pattern change with cooler and unsettled weather returning.
The longwave pattern over the West shows a rather robust upper low spinning off the PacNW Coast. This storm system's associated cold front is draped to the south and southwest. The front is forecast to move south and east through the day today bringing light showers to the Bay Area. Onset of shower activity has not changed much from the previous forecast. Rain showers, which are just showing up on the KBHX radar, will enter the North Bay mid- morning then spread southward during the afternoon. For most of the Bay Area (S of the Golden Gate) most of today will be dry, well at least through mid to late afternoon. Locations to the south are more likely to see shower activity Monday night into Tuesday. It should also be noted that the front is forecast to weaken as it moves southward.
The upstream upper low is forecast to track southward as the cold front moves inland on Tuesday. The upper low will bring much better dynamics and lift to the region resulting in better chances for rainfall. As noted on previous discussions, this upper low is rather cold aloft resulting in better instability and lower snow levels. The forecast has carried thunderstorms for a few days now for Tuesday and the current forecast will do the same. As the cold air aloft moves in overhead on Tuesday instability increases at the surface and aloft. The ECMWF (European Centre for Medium-Range Weather Forecasts) Extreme Forecast Index, National Blend of Models, HREF (ensembles), and deterministic models all show a solid uptick in CAPE through the day Tuesday. Therefore, thunderstorms will be possible with greatest threat during the day Tuesday afternoon. Main threats with developed cells will be heavy rain, gusty winds, small hail, and lightning. Given the lower snow levels hail could accumulate rather quickly in stronger cells. Additionally, some of the lightning guidance from the ECMWF also indicates a decent likelihood for a strike or two. Back to snow levels - they're projected to drop to 3000-3500 feet during the day on Tuesday. Snow will be likely over the higher terrain with some accumulations possible, especially the Gabilan and Santa Lucia Ranges. One final note for Tuesday - not an AR set up or NCFR set up for debris flow concerns, but given the thunderstorm threat burn areas will be watch very closely. Strong cell at the wrong place could cause a problem.
Shower activity will continue through Wednesday as the core of the cold upper low passes overhead. One change to the Wednesday forecast was to keep thunderstorm chances in the forecast, especially inland area. Same threats apply: heavy rain, gusty winds, small hail, and lightning. Storm Prediction Center has much of the region in a general mention for thunderstorms on Tuesday and Wednesday. Snow levels drop 500-700 feet on Wednesday as the coldest air filters overhead.
There still remains the possibility of a few lingering showers Wednesday night into early Thursday as the upper low finally moves inland toward the Desert SW. When it's all said and done rainfall totals from Monday through early Thursday will range from 1"-2" North Bay Mts and coastal Mts with a few jackpots up to 3" per hi- res models. Interior valleys and lower elevations generally in the 0.25"-0.75" range. Obviously amounts could be locally higher given the thunderstorm threat. Snowfall totals will be tricky as surface temps may hamper accumulating snow. Nonetheless a few inches will be possible over the North and East Bay. The Santa Lucia and S Gabilan Range could see 5-10".
Drier weather briefly returns on Friday and Saturday. Previous forecast look dry,but latest ensemble forecast shows rain chances returning late Saturday night and Sunday. At this time, chances are low and the storm system doesn't look strong, but a slight chance for rain has been added to the forecast.
as of 09:53am PST Monday...West to southwest winds will prevail this morning ahead of a weak frontal boundary that will push through the waters midday. Moderate winds will accompany this frontal passage with winds briefly turning W in the wake of the front, then returning to the SW tonight into early Tuesday as a secondary front approaches from the north. Increasing W winds are forecast by late Tuesday before weakening NW to N winds return through Wednesday. A large northwest swell train is arriving in the waters this morning and will bring seas in excess of 10 feet (locally above 15 feet) today, resulting in hazardous small craft across the waters. In addition, thunderstorms are possible over the water on Tuesday.
.MTR WATCHES/WARNINGS/ADVISORIES... .Tday...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