textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1248 AM PDT Thu Aug 6 2026

- Elevated fire weather conditions in the higher terrain Thursday

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

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

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

SHORT TERM

Issued at 200 PM PDT Thu Aug 6 2026 (This evening through Friday night)

Seeing a lot of similarities today to the last few days...the marine layer foot print from this morning is dictating the "cooler" temps and the hotter inland temps. Latest 24 hr trends follow this foot print too showing slightly warmer temperatures this afternoon across the interior.

For tonight...a little bit of rinse and repeat. Marine layer hugging the coast will once again march inland with a slight compression, but still decent inland reach. Nocturnal drying and active thermal belts persist above the marine layer exacerbating the fire weather concerns.

Monsoon moisture influx is slowing creeping in from the south as we speak. Latest guidance continues to show increasing moisture through Friday. Normally, focus would turn toward high based convection, but the large ridge and lack of trigger will like limit convective potential. Also, the moisture seems to be rather high (>10k ft) so impacts at the surface may be minimal.

Friday and Friday night...large upper level ridge will expand back over the region bringing a more noticeable warm up across the interior. For the coast, same old same old, persistent marine layer influence keeping temperatures in check.

LONG TERM

Issued at 230 PM PDT Thu Aug 6 2026 (Saturday through next Wednesday)

First and forecast, a Heat Advisory has been issue for Saturday and Sunday. The warming trend will continue Saturday and then moderate Sunday. The warmer interior temperatures in the mid 90s to lower 100s will push HeatRisk back into the critical levels (widespread Moderate to pockets of Major). Overnight lows will remain mild and in the 60s to mid 70s for interior and higher terrain locations. There are lots of outdoor events going on around the Bay Area this weekend. Interior locations will want to take some safety precautions for the heat: hydrate, take breaks, seek shade, never leave pets/people in cars. Do expect a warm up at the coast too, but it's the Bay Area so pack a jacket as the marine layer will move inland during the evening hours.

HeatRisk concerns begin to fade on Monday as the large ridge flattens and looks to split into two with sagging H5 over CA coast. The cooling trend will continue through at least Wednesday.

AVIATION

(18Z TAFS) Issued at 1101 AM PDT Thu Aug 6 2026

Satellite is showing stratus receding to the coastline where it'll remain for the rest of the day. Typical diurnal onshore breeze pattern is expected where winds will increase to 10-15 kt through the afternoon and ease to 5-8 kt by sunset. Widespread stratus coverage expected again tonight which will bring a mixed bag of low- end MVFR to IFR ceilings. Medium confidence on whether LVK will be included in the stratus coverage tonight. If there is a sufficient onshore breeze, an MVFR ceiling may develop so TAF hints at the possibility around 12Z. Overall, medium confidence on the exact arrival of stratus tonight.

Vicinity of SFO...VFR through the afternoon as onshore winds increase. With a depth of around 1000-1500 feet, the marine layer will bring MVFR ceilings (~OVC010-015) over SFO and OAK this evening around 04-06Z. Medium confidence on the exact timing of ceilings as they may arrive a couple hours later than specified. Stratus should mix out by 17-18Z Friday morning as onshore winds increase.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Stratus should remain confined to the coastline through the afternoon, resulting in VFR conditions. Anticipated stratus arrival is currently around 03Z, though it may arrive as late as 06Z. Prevailing MVFR ceilings are expected for SNS, meanwhile MRY will drop to IFR. SNS may intermittently drop to high-end IFR ceilings overnight. Coastal drizzle associated with these low ceilings are possible.

MARINE

(Today through Tuesday) Issued at 1012 AM PDT Thu Aug 6 2026

Gentle northwest winds continue to increase to strong by Saturday morning across the outer Northern coastal waters. Wind-driven moderate seas build to rough (9-12 feet) Saturday night in response to strengthening winds. A long period southwesterly swell of 15 to 17 seconds approaches our coastline Saturday morning and persists through the weekend.

FIRE WEATHER

Issued at 1248 AM PDT Thu Aug 6 2026

Elevated fire weather conditions continue Thursday with hot and dry conditions alongside the diurnal sea breeze. PSAs of Mid Coast to Mendocino, Diablo/Santa Cruz Mountains, and Central Coast Interior are all currently in the 97th percentile for ERC with Mid Coast to Mendocino and Central Coast Interior forecast to reach daily record values this weekend. This indicates potential for extreme burning conditions. Even the more marine layer influenced PSAs of Bay Marine and Central Coast are forecast to peak in the 80th-90th percentile. Building high pressure will bring near-critical fire weather conditions Friday through Sunday. Temperatures will be 10 to 15 degrees above normal with a shallow marine layer in place. Poor minimum daytime relative humidity as low as 10% is expected in the afternoons with little-to-no recovery expected overnight. The one missing piece preventing this from being a Fire Weather Watch/Red Flag Warning as of now is wind, it's expected to be light. The exception being through gaps/passes (namely Altamont Pass, the Delta, and Pacheco Pass) and down the Salinas Valley. To add onto this, the critical conditions are not expected to overlap spatially (majority of a zone) or temporally (for at least 8 hours) to warrant a product.

Sarment

MTR WATCHES/WARNINGS/ADVISORIES

CA...Heat Advisory from 10 AM Saturday to 10 PM PDT Sunday for CAZ503- 504-510-512>515-517-518.

PZ...None.