, Issued at 1224 AM PST Wed Dec 10 2025 (Today and tonight)
Tule fog and stratus continue with very similar coverage to 24 hours ago. In addition to the entire Central Valley, most of the North Bay and the interior East Bay are impacted by this persistent radiation fog. This is caused by unmoving high pressure bringing clear, dry, and calm conditions to the troposphere. Combined with long December nights, nocturnal radiative cooling from both the Earth's surface and cloud tops are enhanced. Since the cooling is coming from the bottom up, it's very stable (cold air sinks). And since the cooling at night is enough to reach saturation and form or bolster the existing clouds, a positive feedback loop sets up where the clouds then block incoming sunlight during the day. All this works to keep the day-time temperatures cool under the clouds, and the models have been struggling to capture just how cool. Kentfield stayed between 43 and 46 degrees all day Tuesday. The forecast is challenging because there is very warm air just above the clouds. The 850 temperature has blown past the 90th percentile is now approaching the daily max on record. Boulder Creek stayed clear and reached 78 degrees yesterday. This big discrepancy between the thin cold layer and everything else is really tough to nail down. When the advanced weather models let us down, we often fall back on the most rudimentary form of forecasting in existence: persistence. In other words, what happened yesterday will happen today. Specifically Tuesday's high temperatures are making up 66% of the forecast for Wednesday. With an unchanging pattern, that's not a bad guess. If the clouds clear early though, watch out for temperatures to spike. Areas outside of the clouds (Central Coast, SF Peninsula) will have cooler mornings and warmer afternoons. Maybe just a couple degrees warmer than yesterday.
..issued at 1224 AM PST Wed Dec 10 2025 (Thursday through Tuesday)
Temperatures should climb a degree or two each day through Friday before the ridge axis finally moves through on Saturday. That will mark the end of this prolonged boring pattern as a more zonal jet stream moves in. We should finally see some high clouds by Sunday with a chance for rain starting Monday or Tuesday. While we are finally losing the ridge, we're not getting a substantial trough, so any rain bearing systems should be relatively light. On the other hand the active zonal flow could bring these weaker systems in quick succession. CW3E shows both the ECCC and NCEP AR activity anomaly peaking around +2 AR days per week from 12/15-12/21 before falling back to near the climatological norm for the following 2 weeks. In other words if we don't get any substantial rain next week, there is no strong signal for it to come during the rest of the month. Perhaps the best chance is around the 20th, but there's a lot of uncertainty. The 00Z ECMWF ensemble members range from 0.0" to 8.4" of total rain at SFO through the 21st. So the total dispersion is massive, but the more reasonable interquartile range is 0.4" - 2.0". The GEFS is drier with a medial closer to 0.5". Temperatures will cool this weekend, but should remain warmer than normal through next week. The CPC temperature outlooks are about as confident as we ever see that it will remain warmer than normal for the next couple weeks, but that doesn't necessarily take our famous microclimates into account.
(12z TAFS) Issued at 324 AM PST Wed Dec 10 2025
Higher confidence in clearing out of the fog and stratus today for North Bay terminals. Day-to-day change gradually improving as high pressure builds aloft. Patchy stratus invof SF Bay providing lower confidence there, but based on persistence forecast KOAK likely to remain VFR.
Vicinity of SFO, Patchy stratus around the Bay this morning, but much less coverage than 24 hours ago. Some stratus invof the terminal may linger through sunrise. Not enough confidence to include in TAF attm. Most of the area around the terminal, including bridge approach, expected to remain mostly stratus-free.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, High confidence in VFR through the TAF period. Light drainage offshore winds overnight with light onshore flow during the afternoons.
(today through Monday) Issued at 324 AM PST Wed Dec 10 2025
Northerly fresh breeze continues across the outer waters with lighter closer to shore. Light offshore flow through the San Francisco Bay and Delta result in light easterly flow through the Golden Gate. A new, long period northwesterly swell anticipated to arrive today, lasting into this weekend.
Issued at 1224 AM PST Wed Dec 10 2025
Long period swell will reach the coast Wednesday - Friday. This energy brings strong rip currents, an increased risk for sneaker waves, and large breaking waves. The Bodega Bay Buoy is reporting a WNW swell of 9 feet with a 13 second period. That translates to breaking waves of 12-16 feet along west facing beaches. This coincides with nice warm weather, which will likely lure more people to the beach under a false sense of security. A Beach Hazard Statement is in effect through Friday evening. Respect the power of the ocean and never turn your back on it.
Ca, Beach Hazards Statement from 7 AM PST this morning through Friday evening for CAZ006-505-509-529-530.
PZ, Small Craft Advisory until 9 AM PST this morning for Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 3 AM PST Thursday for Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory until 3 PM PST this afternoon for Pigeon Pt to Pt Pinos 10-60 NM.
