textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1225 AM PDT Thu Aug 13 2026

- Near-critical fire weather conditions through Thursday early morning across Monterey and San Benito Counties due to high based thunderstorms

- Up to a 15% chance for elevated rain showers/thunderstorms through Thursday early morning across the Central Coast

- Cooling trend through Friday will bring well below normal temperatures, gradual warming trend through the weekend and into next week

SHORT TERM

Issued at 1225 AM PDT Thu Aug 13 2026 (Today and tonight)

The upper-level low remains off Point Conception and will continue to bring up to a 15% chance for elevated rain showers/thunderstorms through early Thursday morning across the Central Coast as it moves inland. This will bring near-critical fire weather conditions through Thursday early morning across Monterey and San Benito Counties. Erratic/gusty outflow winds up to 40 mph can be expected with any elevated rain showers/thunderstorms. The main concern is lightning which will pose the risk for new fire starts and has the potential to hinder operations on the Timber Fire. Smoke from the Timber Fire will continue to be transported into the Central Coast via light southwesterly winds. Smoke will get trapped under the inversion at night/in the morning, making the appearance and smell worse. The proximity to the low will allow for a relatively deeper marine layer across the Central Coast (2,000 feet) than the Bay Area (1,800 feet). Sensible weather wise, the cooling and moistening trend will continue through Friday with temperatures well below normal.

LONG TERM

Issued at 1225 AM PDT Thu Aug 13 2026 (Friday through Wednesday)

Friday will see the coolest conditions of the week with well below normal temperatures and a deep marine layer as upper-level troughing persists across the West Coast. By the weekend, upper-level ridging will build in to the Desert Southwest and an upper-level low will develop well off the West Coast. This will lead to cooler conditions with a deeper marine layer in the Bay Area and hotter conditions with a more compressed marine layer for the Central Coast. Temperatures will remain below normal with the higher terrain moderating to near normal with the help of warming 850 mb temperatures.

AVIATION

(12Z TAFS) Issued at 524 AM PDT Thu Aug 13 2026

The upper level low continues to pull high level clouds over the region, while the marine layer deepens and spreads stratus. Terminals generally sit within the MVFR cig territory this morning and should hold. A few models show some IFR potential for North Bay terminals, but confidence is moderate to low for that. Any stratus that has formed is expected to erode or retreat to the coast by mid to late morning, with high clouds lingering. Breezy onshore winds return this afternoon and into the evening, where we could see sustained speeds between 10-15 kt with gusts to 15-25kt. Stratus returns tonight, likely onsetting between 01Z-09Z. The later start times favor interior Bay Area terminals.

Vicinity of SFO...The stratus made it to SFO tonight bringing MVFR cigs with it. Models differ on how long the stratus holds, with the times ranging from 14-16Z. A few low clouds may linger throughout the day, with stratus returning tonight due to the deepening marine layer. Breezy onshore winds, with gusts up to 25kt possible, return mid to late afternoon and continue until sunset.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Cigs have been improving tonight, with the latest METARs showing MVFR cigs around 1500-2500ft. Look for this to continue through the rest of the morning hours, with skies clearing by mid to late morning. Onshore flow picks up and should remain a bit breezy through sunset. Stratus returns early, and will likely fall to MVFR between 01-03Z with IFR cigs being possible after 06Z.

MARINE

(Today through Tuesday) Issued at 524 AM PDT Thu Aug 13 2026

Fresh to strong northwest winds slacken to moderate to fresh today with rough seas becoming moderate by the evening. A long period southerly swell will gradually increase Thursday reaching 16 to 18 seconds (possibly higher at times) by Friday and continuing through the remainder of the weekend. Visibility may decrease due to haze and smoke nearby the Big Sur coastline due to the Timber fire.

FIRE WEATHER

Issued at 1225 AM PDT Thu Aug 13 2026

Near-critical fire weather conditions through Thursday early morning across Monterey and San Benito Counties due to high based thunderstorms. The greatest chance was Wednesday afternoon; however, with the upper-level low still off Point Conception, there remains up to a 15% chance for another round through early Thursday morning. Erratic/gusty outflow winds up to 40 mph can be expected with any elevated rain showers/thunderstorms. Lightning will pose the risk for new fire starts and has the potential to hinder operations on the Timber Fire in Big Sur. The areas of most concern will be in the higher terrain above the marine layer (2,000 feet), namely the Santa Lucia Mountains and Gabilan Range. Poor minimum daytime relative humidity around 30% is expected with nocturnal drying bringing little-to-no recovery overnight.

Sarment

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 3 PM PDT this afternoon for Pt Arena to Pt Reyes 10-60 NM.