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 1248 AM PDT Thu Aug 6 2026 (Today and tonight)

Longwave upper-level ridging will drift in from the Eastern Pacific Ocean today, compressing the marine layer to near 1,500 feet in the process. Temperatures will be near to slightly above normal with the diurnal sea breeze. A surge of monsoonal moisture arrives today, increasing surface dew points and relative humidity in the process. Sensible weather wise, this will make it feel hotter and more uncomfortable than what the thermometer reads. Areas of moderate HeatRisk are expected in the interior with pockets of major in the higher terrain of Monterey and San Benito Counties. Stagnant air from the ridge may support haze from wildfire smoke. Elevated fire weather conditions continue today above the marine layer.

LONG TERM

Issued at 1248 AM PDT Thu Aug 6 2026 (Friday through Wednesday)

Surface high pressure over the Four Corners will build and expand westward Friday and into the weekend. This will bring the hottest conditions of the week and compress the marine layer further. Areas of moderate HeatRisk across the interior on Friday will expand to become widespread on Saturday with areas of major. To put this into context: 850mb temperatures, 500mb heights, and PWAT values are all forecast to exceed the 90th percentile Saturday. No records are forecast with temperatures 10-15 degrees above normal for the hottest spots. A potential wild card in the precision and subsequent impacts of the forecast is the aforementioned surge of monsoonal moisture. Mid-to-high level clouds would limit solar insolation during the day and radiational cooling at night, potentially resulting in cooler highs and warmer lows than the official forecast. Even though the ridge will begin to break down and dry air will begin to get filtered in from the northwest, cumulative impacts from the heat and humidity will likely still be felt on Sunday. Near- critical fire weather conditions are expected above the compressed marine layer Friday through the weekend due to hot and dry conditions with the diurnal sea breeze. Global ensemble clusters are in agreement that upper-level shortwave troughing off the West Coast will prevent the aforementioned ridge and subtropical high pressure across the Eastern Pacific Ocean from joining forces and building out of control across our area. Sensible weather wise, temperatures will moderate to near normal with onshore flow Monday through Wednesday. 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 Saturday evening through Thursday morning.

AVIATION

(06Z TAFS) Issued at 953 PM PDT Wed Aug 5 2026

VFR prevails early tonight with only KHAF and KSNS with MVFR ceilings thus far. The stratus push inland isn't as dramatic as thought just three hours ago, but confidence remains high that it will eventually spread over most of our area below 1500ft by sunrise Thursday. With high pressure continuing to build, expect VFR conditions by late morning for most terminals, possibly early afternoon for the Monterey Bay sites as a compressed marine layer retreats back to the coast.

Vicinity of SFO...Stratus lingering in vicinity of the terminals but currently slow to make much more progress. The inland push isn't taking hold as quickly as though just a few hours ago, but confidence is high that IFR/LIFR ceilings will develop after midnight and persist through late morning. VFR through the remainder of the forecast period once stratus retreats back to the coast.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...MVFR ceilings will become IFR/LIFR after midnight and continue through late morning at KSNS, possibly early afternoon for KMRY. Moderate to high confidence that IFR/LIFR ceilings return by early evening before sunset with VFR most of the afternoon on Thursday.

MARINE

(Tonight through next Tuesday) Issued at 953 PM PDT Wed Aug 5 2026

Light to gentle breezes will continue through Thursday with seas between 2-6ft. Northwest winds begin to increase Friday into the weekend with building seas and hazardous conditions for small craft. A long period southwesterly swell of 15-17sec begins on Saturday, peaks on Sunday then begins to subside by the beginning of next week.

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...None. PZ...None.