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

(18Z TAFS) Issued at 1156 AM PDT Mon Aug 31 2026

Finishing Fogust off strong with a robust marine layer at a depth of around 2200 feet this morning. MVFR stratus will take a bit longer to scatter out today, likely in the early afternoon. Moderate onshore winds increase through the day and ease slightly overnight. APC and LVK may experience gusts up to 20 kt through the late afternoon which will gradually diminish tonight. Medium confidence on how widespread the marine layer will be tonight as an upper level trough approaches our coast. This trough may generate sufficient lifting to mix out the marine layer across the North Bay, but confidence remains low. Higher confidence for coastal sites to develop MVFR ceilings around sunset with HAF likely to stay cloudy all day.

Vicinity of SFO...MVFR stratus persists into the afternoon as moderate westerly winds increase. There has been some disagreement in the model guidance on whether stratus will completely scatter out today. Currently on satellite, there is some dry air making its way to our coast. This dry air combined with a moderate onshore flow may be enough to scatter out the remaining clouds in the SF Bay. MVFR ceilings return as winds ease to gentle and persist into Tuesday afternoon. Medium confidence on the overall forecast.

SFO Bridge Approach...Stratus is likely to become patchy over the bridge before scattering out at the terminals this morning/early afternoon. Otherwise, similar to SFO.

Monterey Bay Terminals...Northwest to westerly breezes increase to moderate this afternoon as MVFR ceilings scatter out. The marine layer is less likely to mix out due to the upper level trough, therefore anticipate an early return of MVFR ceilings right around sunset.

MARINE

(Today through Saturday) Issued at 1156 AM PDT Mon Aug 31 2026

Northwest to westerly gentle breezes prevail through the week and may become moderate at times. Wind driven seas remain slight to moderate through the week as a long period southerly swell continues to diminish by Tuesday.

MTR WATCHES/WARNINGS/ADVISORIES

CA...None. PZ...Small Craft Advisory until 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.