textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 428 PM PDT Mon Aug 17 2026

- Slight warming trend continues through Wednesday

- Marine layer remains compressed through mid week

- Light winds continue to be mitigating factor for Timber Fire

SHORT TERM

Issued at 1145 PM PDT Mon Aug 17 2026 (Today and tonight)

Mid/upper level clouds continue to stream from southwest to northeast across our area with mild temperatures expected once again overnight into early Tuesday morning. The mild start to the day will help bump temperatures at least a few degrees (away from the marine layer) higher from Mondays values as the influence from upper level ridging over the Four Corners nudges west. H85 temperatures will be around 23-24C by peak heating which is in the 90th percentile for this time of year. With that, the warmest temperatures will be at higher elevations, especially the East Bay Hills and Santa Lucias, including higher portions of the Timber Fire. Fortunately, light winds continue to be a mitigating factor to more rapid spreading of the fire.

LONG TERM

Issued at 1145 PM PDT Mon Aug 17 2026 (Wednesday through Monday)

Warmer temperatures persist Wednesday under the influence of the aforementioned ridging aloft, however the troughing over the EPAC pushes back east and slightly north by Thursday with a sharpening trough axis well offshore. The cool down for Thursday through the remainder of the extended forecast will be subtle and gradual. There are at least two tropical waves that will pass well to our south, the first on Thursday followed by a more organized wave with tropical development possible by the end of the weekend into the beginning of next week. We'll be keeping an eye on any midlevel moisture advection north from either of the two waves.

AVIATION

(12Z TAFS) Issued at 442 AM PDT Tue Aug 18 2026

IFR-LIFR everywhere as stratus pushes into the Bay Area and Central Coast. Models are not capturing the current marine layer well and continue to show it compressing to ~1000 feet while it stays around 1500 to 2000 feet in actuality. Opted to follow a general persistence forecast for clearing by late morning and for stratus return later tonight. Stratus will be more persistent along the coast, potentially impacting HAF all day, with only a brief period of VFR at MRY and SNS. Some potential for fog along the coast this morning with moderate reductions in visibility at HAF, MRY, and SNS already being observed. Given the relatively stable forecast, moderate confidence in a persistence forecast again tonight with a mix of IFR to LIFR conditions returning this evening and coastal reductions in visibility early tomorrow morning.

Vicinity of SFO...IFR ceilings generally persist until late this morning. LAMP guidance suggests some potential for ceilings to go from IFR to MVFR shortly before clearing around 18Z. Gusty onshore winds are expected this afternoon and evening before winds ease overnight. Opted for a more persistence based forecast of IFR ceilings again tonight with stratus returning around 05Z and lasting through the rest of the TAF period.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...LIFR-IFR ceilings continue through late morning with moderate confidence in clearing around 18/19Z. VFR conditions briefly return this afternoon before IFR to LIFR conditions redevelop early this evening into the overnight hours. Followed persistence to show the lowering of stratus from IFR to LIFR with substantial reductions in visibility becoming more likely closer to 12Z. Moderate onshore winds expected this afternoon before winds ease overnight.

MARINE

(Today through Sunday) Issued at 442 AM PDT Tue Aug 18 2026

A fresh to strong northwest breeze will develop across the outer waters today and extend into the inner waters tonight into tomorrow. Winds then remain elevated through the end of the forecast period. Locally stronger winds are possible in the coastal jet regions north of Point Reyes and along the Big Sur coast. Seas build to 7 to 9 feet Tuesday and Wednesday before subsiding late week.

FIRE WEATHER

Issued at 200 PM PDT Mon Aug 17 2026

The marine layer will gradually compress over the next 24 to 36 hours, as high pressure builds over the region. As a result, nocturnal drying will be possible through at least mid-week for the higher elevations, with more widespread fair to moderate recoveries developing over the higher elevations, especially in and around the Timber Fire.

MTR WATCHES/WARNINGS/ADVISORIES

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