Issued at 828 AM PST Fri Dec 5 2025
Satellite imagery does indeed show the Tule Fog creeping into the interior East Bay and parts of the North Bay. In particular, Contra Costa County has seen some dense fog develop and the East Bay Interior Valleys are now under a Dense Fog Advisory through 11 AM today. Will continue to monitor the stratus evolution and may need to extend into the North Bay if dense fog develops there, or cancel it early if the visibilities improve. The Cold Weather Advisory has been allowed to expire. No other changes to the forecast at this time.
DialH
, Issued at 315 AM PST Fri Dec 5 2025 (Today and tonight)
First and foremost expanded the Cold Weather Advisory to include the North and East Bay Valleys with the existing advisory over the Interior Central Coast. A lot less mid-hgih level clouds are being observed overnight. The clear skies combined with relatively light winds increased radiational cooling effectiveness overnight. As such, seeing a lot more observations around that 36 degree threshold. Therefore, went ahead and expanded the Cold WEather Advisory. Also seeing some radiational fog form over the North Valleys with patchy dense fog near Santa Rosa. Additionally, the Central Valley is still seeing some Tule Fog. Just like the last few nights it will creep into the West Delta and far interior East Bay Valleys.
Otherwise, the large area of upper level high pressure parked off the CA will slowly ooze eastward. At the same time a few weak systems will ride the north periphery of the ridge and move through the PacNW. These weak system will bring some clouds and decaying fronts over the NorCal Coast. Previous forecast had a mentions of showers over the coastal waters today and tonight, but it's looking less likely. Hi-res guidance is still picking up on some moisture. In stead of completely removing the precip converted it to drizzle. Regardless, no impact to land and kept all chances over the waters.
Sensible weather today will be rather pleasant after the cool start. Highs today will be mainly in the 60s. For tonight, expecting less radiational cool due to some increasing clouds and possible return of low stratus. Will hold off on extending any Cold Weather Advisories tonight.
..issued at 320 AM PST Fri Dec 5 2025 (Saturday through Thursday)
Pretty benign weather through the long term. The ridge of high pressure will keep the region high and dry with the exception of drizzle over the coastal waters this weekend. The ridge of high pressure is expected to build and strengthen over CA into early next. As such, additional warming is expected with a general 2 to 4 degrees through the middle of next week. In fact, by next Wednesday/Thursday interior Central Coast is forecast to reach the mid 70s with solid 60s to near 70 elsewhere around the Bay Area.
How about rain? Longer range guidance still shows a possible pattern change by the middle of the month. Cluster analysis of ensembles show a majority still keeping a ridge, but a few cluster groups show a breakdown of the ridge. FWIW CPC 8-14 day outlook is now showing increasing chances for precip Dec 12-18.
(18z TAFS) Issued at 938 AM PST Fri Dec 5 2025
Patchy to areas of fog persist across the North Bay and East Bay valleys this morning and are forecast to improve between 19- 20Z. This will give way to mostly VFR conditions after low ceilings and visibilities improve. Onshore winds look to increase by this afternoon across the San Francisco Bay and Monterey Bay terminals before easing late this evening and into Saturday morning. This is when low ceilings and/or visibilities are expected again in the North Bay and East Bay valleys early Saturday morning. Any low ceilings and/or visibilities that do develop are expected to clear at a similar time as today.
Vicinity of SFO, VFR through the TAF period. Offshore winds prevail this morning and are expected to become north- northwesterly by mid- to-late afternoon. Winds diminish overnight with moderate to high confidence of onshore winds returning by Saturday afternoon.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, VFR through the TAF period. Light to southerly winds prevail this morning and are forecast to become onshore by early-to-mid afternoon. Winds diminish overnight and become southerly early Saturday morning.
(today through Wednesday) Issued at 828 AM PST Fri Dec 5 2025
Northerly winds are increasing across the waters with fresh to strong gusts expected. Localized near gale force gusts are possible across the outer waters and in the favored coastal jet regions through the weekend. These winds persist into the upcoming work week. Moderate seas continue with seas building to between 6 to 8 feet Friday through Sunday.
Ca, Coastal Flood Advisory until 3 PM PST Sunday for CAZ006-506-508- 529-530.
Dense Fog Advisory until 11 AM PST this morning for CAZ510.
PZ, Small Craft Advisory until 3 AM PST Saturday for Pt Arena to Pt Reyes 0-10 nm.
Small Craft Advisory from 3 PM this afternoon to 3 AM PST Sunday for Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory until 9 PM PST Saturday for Pt Arena to Pt Reyes 10-60 NM.
Small Craft Advisory until 3 AM PST Sunday for Pigeon Pt to Pt Pinos 10-60 NM.
