textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 118 AM PDT Wed Aug 12 2026

- Near-critical fire weather conditions Wednesday afternoon 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 Wednesday across the Central Coast

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

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

SHORT TERM

Issued at 118 AM PDT Wed Aug 12 2026 (Today and tonight)

Today's forecast attention turns 300 miles southwest of Point Conception where a low pressure system is bringing up to a 15% chance for elevated rain showers/thunderstorms Wednesday across the Central Coast. This has the potential to be a low probability/high impact scenario and will bring near-critical fire weather conditions Wednesday afternoon through Thursday early morning across Monterey and San Benito Counties. So far, lightning has remained confined to the circulation with mid-to-high level clouds beginning to stream in. An upstream upper-level trough, mid-level lapse rates around 7.5 degrees C/km creating sufficient MUCAPE values around 500-1000 J/kg, and PWATs in excess of one inch are the thunderstorm ingredients. Confidence is lowest in the lift/trigger as guidance/models are struggling with the circulation and cutoff lows are notorious to forecast due to their independence from the jet stream. Uncertainty lies in what these two features will do when they collide, including track and potential dry air entrainment which would lower rain shower/thunderstorm chances. With moisture confined to the mid-to- upper-levels and a dry slot in the low levels, DCAPE values of 500- 1000 J/kg will be capable of producing erratic/gusty outflow winds of 35-45 mph with any rain showers/thunderstorms that develop. 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. The smell and appearance of smoke will be the worst under the inversion at night and in the morning. Sensible weather wise, the cooling and moistening trend will continue through Friday with temperatures well below normal and a deep marine layer bringing a chance of drizzle. 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 through Thursday morning.

LONG TERM

Issued at 118 AM PDT Wed Aug 12 2026 (Thursday through Tuesday)

Cooling and moistening trend continues through Friday as global ensemble clusters are in agreement that upper-level troughing will remain over the West Coast. By the weekend, heights will begin to rise as upper-level ridging builds in from the Southeast while simultaneously a cutoff low develops off the Pacific Northwest. Sensible weather wise, this will result in a gradual warming trend and an increase in onshore flow; however, temperatures will remain below normal.

AVIATION

(12Z TAFS) Issued at 525 AM PDT Wed Aug 12 2026

The marine layer is at roughly 1500-2000ft this morning, but the view from satellite is currently blocked due to high clouds moving in. Expect the stratus to hold where it is at, with minimal expansion into the South and East Bay valleys. Elsewhere, MVFR to IFR cigs are being observed where there is stratus with the exception being KSTS where cigs are LIFR. Look for conditions to improve by mid to late morning, with high clouds lingering. Tonight, the stratus is expected to return. There's a curve ball as an upper low and an additional disturbance move through. Will this keep the stratus at hand, allow it to expand or will the pattern shift up a bit with the high cloud? Opted to keep the pessimistic forecast of stratus returning tonight and into tomorrow morning, but this will need to be monitored. Moderate to high confidence in the forecast through Wednesday evening. Moderate confidence for Wednesday evening into Thursday morning.

Vicinity of SFO...Stratus detections is a bit difficult this morning due to the high clouds overhead. Looking at webcams and stations around the San Francisco Bay, there are some MVFR cigs present. Current thinking is we should stay VFR with only a FEW or SCT MVFR cigs possible through mid to late morning. High clouds linger into the afternoon with the next challenge being winds. Some guidance keeps SSW to SW through the day, while others try to bring onshore winds back. May need to adjust the winds by the 15Z update if the trend continues for SW this afternoon. Tonight, guidance tries to bring back stratus, but confidence is too low to sock us in with low clouds.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...Another cloudy start to the morning, as stratus seeped into the terminals early Tuesday evening. Look for conditions to clear by mid to late morning, retreating to the coast. Models show an afternoon of VFR conditions, but it will dependent on on just how far back the stratus pulls. Tonight, expect it to return early on with Thursday morning potentially being interesting. An upper level disturbance swings just to our north, which could bring some drizzle to the terminals. This hasn't been added to the forecast due to timing issues if this were to happen.

MARINE

(Today through Monday) Issued at 525 AM PDT Wed Aug 12 2026

Fresh to strong northwest winds will continue into early Thursday with for the northern outer waters. Isolated near gale gusts will continue through Wednesday morning. Seas will be rough and around 9 to 11 feet, with wave heights slowly subsiding through Thursday. Long period southerly swell will gradually increase late in the week, peaking between 16 to 18 seconds late Friday through early Sunday. Expect haze and smoke to limit visibility at times along the Big Sur coast due to the Timber fire.

FIRE WEATHER

Issued at 118 AM PDT Wed Aug 12 2026

Near-critical fire weather conditions Wednesday afternoon through Thursday early morning across Monterey and San Benito Counties due to high based thunderstorms. Confidence remains low for a low probability/high impact scenario of elevated rain showers/thunderstorms across the Central Coast from a low pressure system that is currently 300 miles southwest of Point Conception. Erratic/gusty outflow winds of 35-45 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 (1,500 feet), namely the Santa Lucia Mountains and Gabilan Range. Poor minimum daytime relative humidity around 30% is expected in the afternoons with little-to-no recovery overnight.

Sarment

MTR WATCHES/WARNINGS/ADVISORIES

CA...Coastal Flood Advisory until 2 AM PDT Thursday for CAZ006-506- 508-529-530.

PZ...Small Craft Advisory until 9 AM PDT Thursday for Pt Arena to Pt Reyes 10-60 NM.