Marine Weather and Tide Forecast for San Francisco, CA

UPDATE
Issued at 922 AM PST Sat Dec 7 2024

A chilly start to the morning across the Bay Area and Central Coast! The coldest places in the interior North Bay valleys and interior Monterey county saw morning lows in the upper 30s while most other places stayed in the 40s to low 50s. Pockets of fog in the North Bay have generally dissipated with minimal impacts to visibility currently being observed. No major changes to the forecast. Today warms up nicely with highs in the mid to upper 60s and the warmest South Bay and interior Central Coast locations potentially flirting with the low 70s.

SHORT TERM
(Today and tonight)
Issued at 337 AM PST Sat Dec 7 2024

Generally clear skies across the region with patchy radiational fog and stratus across the North Bay valleys, with further development possible in the West Delta. Low temperatures are around seasonal averages in the lower elevations, with lows in the lower to middle 40s inland and closer to the upper 40s to near 50 along the Pacific coast, perhaps into the mid 50s along the Santa Lucia mountains.

A cold front over the eastern Pacific is closing into the western United States, associated with a low pressure system currently over the eastern Gulf of Alaska. This low pressure system moves towards Haida Gwaii. For those of you not well-versed in Canadian geography, this is the archipelago that sits off the northern coast of British Columbia, just south of southeast Alaska. As the low crosses into British Columbia, it dissipates. As a result, by the time the cold front makes it into central California, it too is dissipating, and whatever precipitation potential it may have had is limited to coastal drizzle with practically zero chance of measurable precipitation (0.01" or more). High temperatures range from the middle 60s to lower 70s in the inland valleys to the upper 50s to middle 60s along the Pacific coast, or about a 2 to 3 degree drop in high temperatures across the Bay Area while some areas of the interior Central Coast maintain highs around those on Friday.

LONG TERM
(Sunday through Friday)
Issued at 337 AM PST Sat Dec 7 2024

High temperatures continue to dip on Sunday with a couple more degrees of cooling, particularly in the interior Central Coast.
Later on Sunday into Monday, high pressure develops in the Great Basin on the back of the cold front, leading to a period of offshore flow throughout the region. The gustiest winds are expected in the higher elevations of the interior North Bay and East Bay. Of those, the highest gusts are expected along the crest of the Vaca Mountains on the eastern border of Napa County, where the chances for wind gusts reaching 35 mph or above on Monday reach 40-60%. Wind gusts in the rest of the region top out near 20-30 mph, so there's not enough confidence for a Wind Advisory. In addition, with the recent rainfall and lighter winds across the rest of the region, widespread fire weather concerns are not expected, despite fuels remaining drier in the interior Central Coast.

Clear skies and light winds will promote more radiational cooling late Monday into Tuesday, with low temperatures reaching the low to mid 30s in the inland valleys, especially across the North Bay and Central Coast. The operations team considered issuing a Frost Advisory, but elected to wait another day to see how the forecast would evolve. Even so, consider how would you tend to sensitive plants and vegetation, as well as pets and those without adequate heating.

Towards the latter part of the next week, considerable uncertainty still remains regarding chances for more widespread rain. On the surface, ensemble means appear to show a trough approaching the West Coast on Friday heading into the weekend. Closer analysis in the ensemble model clusters reveals that around half of the ensemble members showing some type of ridge over the western United States, which would limit our potential rainfall totals, and potentially translating the significant rainfall towards the north, perhaps as far north as British Columbia and southeastern Alaska. The other half place an amplified trough into the state and thus see more significant rainfall coming into northern and central California.
For what it's worth, the current forecast shows PoPs above 50% beginning to edge into the North Bay on Friday and spread into the Bay Area by Saturday, but this could very well mean anything from a light, mainly beneficial rainfall, to a much more impactful rain and wind system. Keep track with the forecasts throughout the next week, as additional model guidance comes in and the forecast becomes further refined.

AVIATION
(18Z TAFS)
Issued at 1053 AM PST Sat Dec 7 2024

The picture from space this morning shows valley fog lingering in some of the North Bay counties; however, all TAF Sites are currently reporting VFR conditions. In addition to that, satellite shows cirrus flowing over the region. Expect light winds and VFR conditions to prevail through the evening. Tonight, a weak front will approach the region. This could bring MVFR to IFR cigs to coastal sites, while inland sites remain VFR.

Vicinity of SFO...High clouds are moving over the region this morning and will continue to stream by through the afternoon. VFR conditions are expected to prevail through much of the period. MVFR to perhaps IFR conditions are possible early Sunday morning ahead of the front, with conditions improving mid to late morning.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...High clouds and VFR conditions will prevail through today. Late tonight and into early tomorrow morning, KMRY and KSNS have a shot of MVFR cigs ahead of a weak disturbance.
Should this happen, VFR conditions are expected to return by late morning.

MARINE
(Today through Thursday)
Issued at 919 AM PST Sat Dec 7 2024

A gentle to moderate N breeze remains over the waters today; however, winds will begin to increase this evening ahead of an approaching cold front. This front will bring a fresh to strong N breeze and build rough seas on Sunday. Winds will decrease Sunday night, allowing seas to abate by Monday afternoon. Gentle, shifting wind and a moderate NW swell will persist through the remainder of next week.

MTR WATCHES/WARNINGS/ADVISORIES
CA...None.
PZ...Small Craft Advisory from 9 PM this evening to 3 PM PST Sunday for Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 10- 60 NM.