textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1206 AM PDT Sat Aug 8 2026

- Warming trend through the weekend will result in moderate to major HeatRisk for the interior

- Near-critical fire weather conditions in the higher terrain through Sunday

- Minor coastal flooding for bayshore locations along the San Francisco Bay, San Pablo Bay, and Monterey Bay through Thursday morning

SHORT TERM

Issued at 1206 AM PDT Sat Aug 8 2026 (Today through Sunday)

Upper-level ridging across the Four Corners will expand westward Saturday bringing widespread moderate to areas of major HeatRisk to the interior over the weekend. This will support temperatures 10-15 degrees above normal and a compressed marine layer. While messaging remains the same, the ridge is forecast to be slower to break down with northerly/offshore flow developing at 925 mb down the Northern Sacramento Valley on Sunday. This will make Sunday the hottest of the two days in some locations, namely the North Bay Interior Valleys, San Francisco Bayshore, and San Francisco. Have opted to leave them out of the Heat Advisory still; however, they may need to be included in subsequent forecasts. Near-critical fire weather conditions persist through the weekend across the interior due to very hot and dry conditions. Minor coastal flooding is expected during the highest high tide (evening/overnight) for bayshore locations along the San Francisco Bay, San Pablo Bay, and Monterey Bay through Thursday morning. The Pacific Coast may need to be added Sunday through Tuesday. Tonight's forecast was overdone by 0.1 ft and while that is not a lot, it is the difference of whether or not the Pacific Coast gets included. We will wait to see how our forecast performs and what the trend is after Saturday night's high tide before we make a decision one way or the other.

LONG TERM

Issued at 1206 AM PDT Sat Aug 8 2026 (Monday through Friday)

Global ensemble clusters are in agreement that upper-level shortwave troughing will develop Monday off the West Coast between subtropical high pressure across the Eastern Pacific Ocean and the Four Corners high. This will result in temperatures moderating to near normal and the return of a marine layer around 1,000 feet. Even with the cooling trend and the deepening of the marine layer, the increase in onshore wind will support elevated fire weather conditions into next week. The upper-level pattern along with a resurgence in monsoonal moisture may be enough to bring elevated rain showers/thunderstorms to the forecast as early as Thursday and into next weekend. Whether or not the aforementioned trough pinches off to become a low or not will be important for the lifting mechanism factor. As far as instability and moisture go, conditionally unstable lapse rates and sufficient MUCAPE will overlap with PWAT values in excess of an inch. While there's no mention in the official forecast now, it may be warranted as we get closer.

AVIATION

(06Z TAFS) Issued at 952 PM PDT Fri Aug 7 2026

IFR-LIFR stratus is expanding into the Sonoma County valleys, the SF Bay, the Monterey Bay region, and the Salinas Valley with expansion expected to continue into the night. The current forecast calls for gradual compression of the marine layer through the night as an upper level ridge expands over the region. Confidence in stratus impacts at SJC has lowered dramatically, and not expecting any stratus to make it into the interior East Bay. Stratus will retreat to the immediate coast through Saturday morning with breezy onshore winds resuming in the afternoon. Most stratus development on Saturday evening falls after the end of the 24-hour TAF period.

Vicinity of SFO... Moderate confidence that an IFR-LIFR ceiling will develop over the terminal through the night, with some high resolution model output depicting the stratus deck deflected to the north of the terminal. Confidence is higher at OAK. Stratus dissipates over the post-sunrise hours Saturday morning and breezy west-northwest winds develop in the afternoon and evening hours. Low confidence of stratus impacts to the terminal Saturday night through Sunday morning.

SFO Bridge Approach... Lower confidence of stratus impacts compared to the immediate terminal area. Otherwise similar to SFO.

Monterey Bay Terminals... IFR-LIFR stratus persists through the night and into Saturday morning. Stratus will retreat to the immediate coast around 16-18Z and breezy northwest winds develop in the afternoon hours. Moderate confidence that stratus returns early Saturday evening.

MARINE

(Tonight through next Thursday) Issued at 952 PM PDT Fri Aug 7 2026

Moderate seas gradually build to rough seas up to 12 feet as northwest winds increase to fresh to strong by Saturday into the middle of the week. Seas and winds remain elevated through the middle of next week. Embedded near gale force gusts are possible across the outer northern coastal waters. A long period southerly swell at 15 to 17 seconds persists through the weekend.

FIRE WEATHER

Issued at 1206 AM PDT Sat Aug 8 2026

Near-critical fire weather conditions persist through the weekend across the interior due to very hot and dry conditions. Strong thermal belting, extended burn periods, elevated PIG, and near or record BI/ERC values are expected. Temperatures will be 10 to 15 degrees above normal with a compressed marine layer. Poor minimum daytime relative humidity as low as 10% in the afternoons with little-to-no recovery overnight is expected with nocturnal drying in the highest terrain. Even with critically dry conditions, wind is the limiting factor preventing this from being a Fire Weather Watch/Red Flag Warning event. Outside of the diurnal sea breeze that will bring breezy conditions in the afternoons and evenings through gaps and passes, onshore flow will be light. Additionally, critical conditions are not expected to meet coverage or duration requirements to warrant a product. Elevated fire weather conditions are expected into next week as onshore flow increases on the heels of the near-critical hot and dry event this weekend. The upper-level pattern along with a resurgence in monsoonal moisture may be enough to bring elevated rain showers/thunderstorms to the forecast as early as Thursday and into next weekend.

Sarment

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until 2 AM PDT Thursday for CAZ006-506- 508-529-530.

Heat Advisory from 10 AM this morning to 10 PM PDT Sunday for CAZ503-504-510-512>518.

PZ...Small Craft Advisory from 3 PM this afternoon to 9 AM PDT Sunday for Pt Arena to Pt Reyes 10-60 NM.