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

(06Z TAFS) Issued at 1000 PM PDT Thu Aug 6 2026

MVFR-IFR stratus is beginning to expand as it flows into the Petaluma Gap and starts edging into the Golden Gate. Stratus continues to expand across the coastal valleys through the night with low to moderate confidence that impacts extend into the interior East Bay. That may depend on exactly how deep the marine layer is. So far stratus has been developing later than the earlier forecast suggested and the TAFs have been updated to reflect later development times. Stratus is expected to mix out back to the immediate coastline Friday morning with the breezy onshore winds expected to resume in the afternoon. Some stratus expansion is possible Friday evening, but most coverage develops after the end of the 24-hour TAF period.

The SJC ASOS will be offline within a window from 07-13Z due to maintenance at the station; the TAF is marked AMD NOT SKED as a result.

Vicinity of SFO... Low-end MVFR stratus comes into the terminal area within the next couple of hours, with lower confidence on timing as the high resolution models start with the terminal on the edge of the stratus deck. Stratus will gradually mix out through Friday morning followed by breezy and possibly gusty northwest winds in the afternoon and evening hours. Low to moderate confidence of stratus over the terminal Friday night with high resolution models trending towards pulling the stratus deck to the north.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... Low confidence in the timing of the stratus development at the terminals as observed stratus coverage is much lower than model output. Nevertheless high confidence that IFR stratus will build over the terminals through the night. Stratus will retreat to the coast late Friday morning with gentle northwest winds developing in the afternoon hours, diminishing in the evening as the stratus returns.

MARINE

(Tonight through next Wednesday) Issued at 1000 PM PDT Thu Aug 6 2026

Northwest gentle winds gradually increase to a fresh to strong breeze, particularly across the outer northern waters on Saturday through the middle of the week. Moderate northwest seas also build to rough by Sunday morning continuing into the early part of next week. Winds and seas remain elevated through the middle of next week. A long period southerly swell of 15 to 17 seconds will impact the coastal waters beginning Saturday morning.

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...Coastal Flood Advisory from 5 PM Friday to 2 AM PDT Thursday for CAZ006-506-508-529-530.

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

PZ...None.