textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1101 PM PDT Thu Aug 13 2026

- Well below normal temperatures with a deep marine layer and a chance for drizzle Friday

- Gradual warming trend kicks off Saturday with temperatures slightly below normal into next week

SHORT TERM

Issued at 1101 PM PDT Thu Aug 13 2026 (Tonight through Saturday)

Upper-level shortwave troughing will bring the coolest conditions of the week with well below normal temperatures and a deep marine layer Friday. The 00Z sounding observed a marine layer of 2,400 feet with satellite already showing an inland intrusion through the Delta and Pacheco Pass. With the associated lift from the aforementioned trough, drizzle can be expected along the coast and in the higher terrain via orographic lift. Smoke from the Timber Fire is expected to improve with the help of northwesterly transport winds.

LONG TERM

Issued at 1101 PM PDT Thu Aug 13 2026 (Saturday night through next Thursday)

Gradual warming trend kicks off Saturday as upper-level ridging builds into the Desert Southwest. Simultaneously, upper-level troughing will develop well off the West Coast. This will keep the ridge in check and onshore flow in place with temperatures remaining below normal. The marine layer will likely be deeper in the Bay Area than in the Central Coast with a chance for drizzle remaining across the coast and higher terrain. Global ensemble clusters are in agreement through Tuesday and then by Wednesday 60% show troughing prevailing into Thursday. Sensible weather wise, this would result in a cooling trend with increased onshore flow and the deepening of the marine layer.

AVIATION

(06Z TAFS) Issued at 959 PM PDT Thu Aug 13 2026

MVFR-IFR stratus is expanding across the region and will impact all terminals overnight. Lingering southwesterly breezes will gradually diminish through the next few hours. Stratus is not expected to dissipate until early Friday afternoon, around 19-21Z for most terminals. Low to moderate confidence that more northwesterly flow will develop Friday afternoon and evening, with moderate to high confidence that stratus will again develop across the region on Friday evening, with moderate confidence on the exact timing.

Vicinity of SFO... MVFR ceilings arrive imminently and persist into the early afternoon on Friday. Light to gentle southwest winds persist overnight into Friday morning. Low to moderate confidence that winds will turn more towards the west or west-northwest on Friday afternoon and evening, with moderate confidence in stratus returning to the terminal sometime Friday evening to Friday night, although confidence in timing is low to moderate.

SFO Bridge Approach... Similar to SFO.

Monterey Bay Terminals... MVFR conditions persist through the overnight hours with some IFR ceilings possible at MRY. Light winds persist overnight before a moderate confidence forecast for more northwesterly flow develops Friday afternoon. Low confidence in a brief scattering out of the stratus clouds Friday afternoon a couple of hours in the afternoon before stratus returns early Friday evening.

MARINE

(Tonight through next Wednesday) Issued at 959 PM PDT Thu Aug 13 2026

Gentle to moderate west-northwest winds persist into the weekend and early next week as seas continue to subside to moderate in response. A long period southerly swell of about 16 to 18 seconds approaches the coast Friday night into Sunday. Winds will build to a fresh northwest breeze early next week, causing seas to build up to 9 feet. Light drizzle is possible across the coastal waters. Haze and smoke may also impact visibility along the Big Sur coastline due to the Timber fire.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...None.