textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1206 AM PDT Sun Aug 9 2026

- Widespread moderate with areas of major HeatRisk for the interior Sunday

- Near-critical fire weather conditions in the higher terrain 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 Sun Aug 9 2026 (Today and tonight)

The 00Z balloon observed a 925 mb temperature of 30.35 degrees Celsius (third hottest for the date and time), 850 mb temperature of 28.75 degrees Celsius (second hottest for the date and time), and 500 mb height of 5970 meters (record for the date and time). Satellite shows stratus clearing off the coast due to a strengthening ACV-SFO surface pressure gradient. Northerly/offshore flow down the Northern Sacramento Valley Sunday morning will help push the marine layer back to the coast. Both of these factors should support Sunday being the hottest day of this event; however, if the marine layer prevails and northerly/offshore winds don't develop we could have a repeat of Saturday with our forecast being too hot for the lower elevations. Nonetheless, temperatures will be 10 to 15 degrees above normal outside of the marine layer influence with widespread moderate HeatRisk and areas of major HeatRisk in the higher terrain. 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. Have opted to leave the Pacific Coast out as it would be marginal and overnight if it occurred; however, high tide may cutoff access to some beaches.

LONG TERM

Issued at 1206 AM PDT Sun Aug 9 2026 (Monday through Saturday)

Cooling trend kicks off Monday as upper-level shortwave troughing develops off the West Coast. This will moderate temperatures to near normal, deepen the marine layer bringing a chance for drizzle, and increase onshore flow. A reinforcing trough Wednesday will bring more prominent troughing off the West Coast Thursday and into the weekend. This along with a resurgence in monsoonal moisture may be enough to bring elevated rain showers/thunderstorms to the forecast. While there's no mention in the official forecast now, it may be warranted as we get closer.

AVIATION

(06Z TAFS) Issued at 1001 PM PDT Sat Aug 8 2026

IFR-LIFR stratus is making its way inland as the marine layer remains close to 1500 feet deep, and expected to make its way into the coastal valleys through the night. Warmer air lurking offshore is evidenced in the clearing off the coast of the North Bay, but there's low confidence for its impacts to the coastal stratus as the immediate coast remains under the stratus deck. May need to monitor the evolution of the warmer air through the night. Low confidence that LVK gets a brief ceiling sometime early Sunday morning. Stratus will dissipate through Sunday morning, and breezy onshore flow will resume in the afternoon. The high resolution models do show some compression of the marine layer resulting in much less stratus development, but with similar forecast misses over the last couple of days, confidence is low.

Vicinity of SFO... VFR through the next couple of hours with moderate northwest winds. Moderate confidence of IFR ceilings developing after midnight with dissipation expected late Sunday morning. Breezy west winds develop Sunday afternoon and evening, with low confidence for stratus impacts Sunday night.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... IFR-LIFR stratus persists through the night with light to gentle winds. Stratus will dissipate through Sunday morning with breezy onshore winds resuming in the afternoon. Low to moderate confidence that stratus returns to the terminals Sunday evening a few hours before the end of the TAF period.

MARINE

(Tonight through next Friday) Issued at 1001 PM PDT Sat Aug 8 2026

Fresh to strong northwest winds persist into early next week. In response, moderate seas build to rough seas up to 12 feet by Sunday, lasting through the middle of next week. Northern coastal waters will be hazardous for small craft with occasional near gale force gusts possible through the weekend. The San Francisco Bay north of the Bay Bridge into the Delta continues to experience gusty onshore winds through Sunday night. Long period southerly swells at around 15 to 17 seconds are still present in the coastal waters.

FIRE WEATHER

Issued at 1206 AM PDT Sun Aug 9 2026

Near-critical fire weather conditions persist today 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. Localized elevated fire weather conditions in the highest terrain can be expected Monday due to the combination of recent hot/dry conditions and the increase in onshore flow. Depending how the pattern and marine layer evolves, a headline may be warranted and this could last through Wednesday.

MTR WATCHES/WARNINGS/ADVISORIES

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

Heat Advisory until 10 PM PDT this evening for CAZ503-504-510- 512>518.

PZ...Small Craft Advisory from 9 AM this morning to 9 PM PDT this evening for Pt Arena to Pt Reyes 0-10 nm-SF Bay N of Bay Bridge.

Small Craft Advisory until 3 AM PDT Monday for Pt Arena to Pt Reyes 10-60 NM.