textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1004 PM PDT Sun Aug 30 2026

- Morning drizzle likely along the coast

- Cooler weather continues this week

- Chance for light rain Wed-Thu in North Bay

SHORT TERM

Issued at 1004 PM PDT Sun Aug 30 2026 (Tonight through Tuesday)

Marine layer stratus is becoming much better organized than 24 hours ago. Low clouds now cover the entire coast south of Pt. Reyes. With a deeper, more organized marine layer, high resolution models are suggesting coastal drizzle is likely Monday and Tuesday morning.

The troughing pattern will deepen over the next 48 hours, keeping high temperatures 5-15 degrees below normal for this time of year. According to the ECMWF ensemble, there is an 90% chance the 850 mb temperature will drop below 12 C on Tuesday, which is the bottom 10th percentile for this time of year. As the trough axis approaches the coast, there is a good chance (roughly 70%) that the North Bay will get some light rain starting Tuesday.

LONG TERM

Issued at 1004 PM PDT Sun Aug 30 2026 (Tuesday night through next Sunday)

The jet stream becomes highly meridional (north to south) by Wednesday. This makes the forecast more challenging. The 500 mb low will linger around the Pacific Northwest, but the exact track becomes much less certain, and the models are split if it will become completely cut-off from the jet stream later this week or not. Either way the cooler weather and occasional light rain chances will continue through the rest of the week. The exact evolution of this low could have a major impact on the weather next weekend and beyond.

First some background. There is an tropical disturbance in the Eastern Pacific well offshore SW Mexico. The National Hurricane Center is currently calling this system Invest Area 95E as they monitor for the further development needed to earn a name. This system has a 90% chance of formation into a tropical depression in the next 48 hours, and has a high chance of becoming a hurricane by mid-week. This would be the 13th tropical cyclone in the Eastern Pacific this season, so why am I writing about it?

Tropical cyclones are steered by large scale, mid-tropospheric pressure systems. Typically the semi-permanent high pressure over the subtropical eastern Pacific blocks tropical cyclones from leaving the deep tropics. They very often ride the trade winds and follow a WNW track after forming, moving into the open ocean. With the deep trough over the west coast breaking up the typical pattern, the door is open for this particular tropical cyclone to take a more northerly track, roughly parallel to the coast of Mexico.

To be clear, there is virtually no chance that a hurricane will make landfall in California. While it's true the SST anomalies are quite high (3-5 F) along this track, the actual water temperature (70-74 F) is still far too cold to support a tropical cyclone north of the Vizcaino Peninsula (mid Baja). However, if the cut-off low stays strong enough, and moves far enough south to pull the tropical cyclone quickly to the north, there could be impacts from the remnants of this system in about a week. The primary impacts would be rain and wind, and they would likely be focused across Southern California. There are so many moving puzzle pieces that it's impossible to be more specific at this time, but the chance is there, and we'll keep an eye on it.

AVIATION

(12Z TAFS) Issued at 429 AM PDT Mon Aug 31 2026

Extensive stratus development with varying ceilings (MVFR to LIFR) is occurring across the region and further expansion is expected through sunrise. Stratus will retreat to the immediate coastal region after sunrise with a moderate onshore pattern wind developing in the afternoon and evening hours. Tonight through Tuesday morning brings some uncertainty into the stratus forecast, as a decaying cold front approaches the region and could mix out the lower layers, thus inhibiting stratus formation. Opted to lean towards a more persistent forecast for the time being.

Vicinity of SFO... VFR at present. Continuing to monitor MVFR stratus around the terminal area with the possibility of SFO remaining clear through the night. Low confidence on clearing time if stratus does form over the terminal; high resolution model output is attempting to keep the stratus over the terminal into the afternoon hours. Moderate west-northwest winds develop in the afternoon and evening before gradually diminishing into the overnight period. Moderate confidence in stratus development tonight through Tuesday morning.

SFO Bridge Approach... Slightly greater confidence in the development of stratus that would impact the approach path. Otherwise similar to SFO.

Monterey Bay Terminals... IFR stratus continues through the morning hours. Clearing time post-sunrise is uncertain with some high resolution model output keeping MRY under IFR-MVFR ceilings well into the afternoon hours. Gentle to moderate northwest winds are expected this afternoon and evening, with moderate confidence of stratus developing in the late evening-early overnight hours.

MARINE

(Today through Saturday) Issued at 429 AM PDT Mon Aug 31 2026

Fresh northwest winds continue to diminish to a moderate breeze, allowing rough seas to subside to moderate by the late morning. The long period southerly swell continues to decrease through Tuesday. Northwest to westerly winds remain gentle to moderate through the remainder of the work week as slight to moderate NW seas prevail.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory from 9 AM this morning to 3 AM PDT Tuesday for SF Bay N of Bay Bridge.

Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Mry Bay.

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