, Issued at 125 PM PDT Thu Aug 27 2026 (This evening through Friday night)
Looking at satellite imagery, seeing more widespread mid-to-high level cloud cover spreading across the Central Coast and southern portion of the greater San Francisco Bay Area. The greatest potential for high-based convection will be across the Central Coast as the OAK Upper Air sounding reported MUCAPE (instability aloft) slightly greater than 400 J/kg. This is also where the CAMs and higher resolution deterministic models show the greatest MUCAPE values today through early Friday morning. Thus, have added isolated thunderstorms to the official forecast for the Central Coast. Further north across the Bay Area, seeing less threat for thunderstorms, yet remains a non-zero chance.
The Precipitable Water (PWAT) values increase to around or slightly above 1.5" across the Central Coast by Friday morning with a greater potential for wetting rains. However, rainfall amounts are projected to largely be less than 0.10" throughout this event. Thus, we have issued a Red Flag Warning for much of the Central Coast including the Santa Cruz Mountains from 5 AM to 3 PM Friday. Fuels remain dry from the recent warm and very dry conditions above the marine influences, especially in areas above 1000 feet in elevation. This is also where the CAMs have the greatest instability on Friday. Given the Timber and Plaskett fires ongoing, any lightning strikes and/or erratic/gusty outflows would make for difficult firefighting efforts. Will closely monitor the latest forecast models and adjust accordingly.
As the mid/upper level trough deepens off of the Pacific Northwest coast Friday evening into Saturday morning, expecting this deeper moisture plume to shift eastward resulting in PWAT values lowering to near 0.50". Thus, ending the threat for high-based convection. The mid/upper level low off of the Pacific Northwest will push inland Friday night into Saturday, leading to a tightening pressure gradient which will result in breezier winds Friday and into the weekend. Thus, wind gusts are forecast to reach 25 to 35 mph along the coast and through favored gaps, valleys, and passes. This pattern will also usher in cooler temperatures. Zonal flow develops over the weekend holding temperatures steadily below normal.
..issued at 125 PM PDT Thu Aug 27 2026 (Saturday through next Wednesday)
A reinforcing trough deepens off of the Pacific Northwest coast by Monday, allowing afternoon temperatures to be some 5 to 15 degrees below seasonal averages. The current forecast has the potential for rain showers returning towards the middle of next week. However, the evolution of things across the tropical Eastern Pacific remains in question, mainly in the form of remnant tropical moisture to be pulled in from the south. Thus, forecast confidence remains low at this time.
(18z TAFS) Issued at 1222 PM PDT Thu Aug 27 2026
Quite an interesting set up today. A moisture plume is moving across our region from the southwest and is producing lightning offshore as well as some light rain. Whether rain will reach the ground over the terminals is uncertain, but high confidence for virga at the very least. Overall, there is low confidence on the forecasted ceilings towards the end of the TAF period and exact timing of potential vicinity showers, but medium confidence for it to remain south of the Golden Gate. The potential for lightning to impact terminals this TAF period is low, around a 10-15% chance, and TAFs will be updated as needed.
Despite the current set up, VFR conditions prevail through the day with a parade of high level clouds associated with the high-based convective system. Moderate onshore breezes increase through the day and ease overnight. If thunderstorms do develop over land, we will monitor for gusty outflows and amend as needed.
Vicinity of SFO, VFR through the afternoon with onshore winds increasing to 15-20 kt and ease to around 10 kt overnight. SFO and OAK are currently on the edge of the previously mentioned convective system, so there is not an immediate concern for lightning or VCSH. However, this moisture plume is expected to become a bit more widespread early Friday morning. As of writing this, there is a great deal of discrepancy in model guidance, so the timing will be refined in following TAF issuances.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, Moderate onshore winds prevail this afternoon and ease overnight. MRY and SNS have the highest chance of remaining under the influence of the moisture plume this TAF period. MRY may be close enough to the coast to still experience some marine influence, but medium confidence on the timing of IFR ceilings. Lightning is still being observed via satellite offshore and will continue to be monitored.
(tonight through next Tuesday) Issued at 1222 PM PDT Thu Aug 27 2026
Fresh northwest breezes with occasional near gale force gusts persist through the weekend and ease by early next week. Wind driven seas remain moderate into next week as a long period southerly swell around 16 to 18 seconds approaches our coastal waters by Friday morning.
Ca, Red Flag Warning from 5 AM to 3 PM PDT Friday for Caz516-516-517- 528>530.
PZ, Small Craft Advisory until 2 PM PDT Friday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.
Small Craft Advisory from 3 PM Friday to 9 AM PDT Saturday for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Arena to Pt Reyes 0-10 nm-Pt Arena to Pt Reyes 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm.
