textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 143 AM PDT Sun Oct 18 2026

- Hazardous beach conditions continue through tonight

- Cooling trend begins today and persists into the work week

- Light rain showers possible mid-week

UPDATE

Issued at 857 PM PDT Sat Oct 17 2026

Saturday was the last hot day for the next week! Maximum temperatures today reached the low to mid-90s across the interior valleys, bay shorelines remained in the 80s, and the coast saw temperatures rise to the mid 70s to high 80s. A few hotspots even reached the high 90s to low 100s. Luckily, the offshore flow responsible for the warmth is weakening. The SFO-WMC pressure gradient increased by around 6 mb within the past 24 hours (was -10 mb Friday 8 PM and -4.4 mb Saturday 8 PM). In response, onshore flow continues to increase overnight ahead of the incoming dry, cold front. The presence of a moderate onshore push along with a deepening marine layer will support cooler weather beginning Sunday into the work week.

Navarrete

SHORT TERM

Issued at 143 AM PDT Sun Oct 18 2026 (Today and tonight)

Sunday and Monday mark the transition towards cooler conditions and breezy onshore winds. Weakening high pressure allows the marine layer to gradually reform and deepen, though it will be short-lived. Nonetheless, any marine layer presence aids to initiate the beginning of a cooling trend, even if it remains shallow and confined to the coast Sunday morning. As the upper-level trough digs southward along the West coast on Sunday, a strengthening onshore pressure gradient will support moderate westerly breezes. This set up can support wind gusts around 20-25 mph through the Petaluma Gap/Valley with the Altamont and Patterson Passes experiencing gusts closer to 25-30 mph.

Sunday maximum temperatures are forecast to reach the 60s to low 70s along the coast, mid 70s to mid 80s across the interior, with the usual hot spots reaching into the low 90s. On Monday, the maximum temperatures drop further due to increased cold air advection from the upper-level trough. Max temperatures are forecast to reach the mid 50s to mid 60s at the coast, mid 60s to low 70s across the interior, with the southernmost extent of the Central Coast remaining in the mid 70s to low 80s.

LONG TERM

Issued at 143 AM PDT Sun Oct 18 2026 (Monday through Saturday)

Monday night has a better chance for a marine layer around 1500 ft as the center of the upper-level trough deepens along our coastline. By Tuesday morning however, the first round of light rain arrives with precipitation chances around 20-40% across the Bay Area and Central Coast. Rainfall can overpower the marine layer by saturating the atmosphere above it, thereby mixing out. Our stratus marine layer is typically capped by an inversion, defined as layer of the atmosphere where temperature increases with height. Introducing rain into the mix perturbs and cools the inversion layer causing it to disappear resulting in no marine layer. Though there will still be deep convective cumulus clouds present!

By Tuesday afternoon, the cut-off low pressure system slows down and stalls directly to our west with its center approximately 300-350 miles west of San Francisco. As it stalls, a plume of moisture originating in the Eastern Pacific gets funneled into the eastern portion of the system from the south. By Wednesday morning, the system begins to propagate eastward towards the Central Coast. Given the nature of cut-off lows combined with an increased moisture flux and terrain interactions, there is potential for precipitation to wrap around the system's center giving way for widespread light rain on Wednesday across the Bay Area and Central Coast (40-75% chance). European and GFS ensemble members continue to agree on precipitable water values above the 75th percentile on Wednesday. Rainfall chances gradually diminish by Thursday, but cooler conditions remain through the end of the week.

The potential for thunderstorm development (<15% chance) remains near the Central Coast. Compared to yesterday's model runs, the deterministic European model trended upwards in relation to most unstable CAPE which is estimated to be around 200-350 J/kg. There is sufficient instability and moisture available to support thunderstorm development. Though lift is a limiting factor as it is dependent on the alignment and trajectory of the system when it approaches the coast.

AVIATION

(06Z TAFS) Issued at 850 PM PDT Sat Oct 17 2026

Clear skies and VFR conditions prevail due to dry low levels. Expect VFR through most of tonight. Still looking like a 30% chc for MVFR at KSTS, but given the conf will keep the SCT to show some poss clouds. IFR to LIFR more likely at KHAF,KMRY,KSNS tomorrow with shallow moisture layer. Better chc for stratus by Monday AM. Overall conf remains high.

Vicinity of SFO...VFR. Gusty onshore this evening then weakening overnight. Onshore push again tomorrow afternoon with gusts over 20kts.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...VFR through early tonight. Need stratus to develop overnight and if it does it will be shallow leading to IFR to LIFR conditions Sunday AM. 15-20% for dense fog early Sunday for Monterey Bay region. VFR Sunday afternoon.

MARINE

(Today through Thursday) Issued at 1002 AM PDT Sat Oct 17 2026

Moderate to fresh northwesterly breezes will prevail through Monday with strong breezes across the northern outer waters. Widespread hazardous conditions will spread across the coastal waters as a result Sunday afternoon, likely continuing into Monday. Moderate seas will prevail across the inner waters with rough seas building across the outer waters Saturday through Monday, rebuilding again Tuesday. Light rain is expected Monday night through Wednesday.

BEACHES

Issued at 1002 AM PDT Sat Oct 17 2026

Hazardous beach conditions will be present at Pacific Coast beaches through Sunday and likely into next week. Long period southerly/southwesterly swell will bring an increased risk for sneaker waves and strong rip currents with breaking waves of 7 to 12 feet. Remain off jetties, piers, rocks, and other waterside infrastructure as waves can sweep across the shoreline without warning, pulling people into the sea. Remain out of the water to avoid hazardous surf with strong rip currents and never turn your back on the ocean!

Sarment

MTR WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement through this evening for CAZ006-505-509- 529-530.

PZ...Small Craft Advisory until 9 PM PDT this evening for Pt Arena to Pt Reyes 0-10 nm.

Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Pigeon Pt to Pt Pinos 0-10 nm-Pigeon Pt to Pt Pinos 10-60 NM-Pt Pinos to Pt Piedras Blancas 0-10 nm-Pt Reyes to Pigeon Pt 0-10 nm.

Small Craft Advisory until 9 PM PDT this evening for Pt Arena to Pt Reyes 10-60 NM.