textproduct: San Francisco Bay Area

KEY MESSAGES

Updated at 1010 PM PDT Wed Sep 2 2026

- Beneficial rain Thursday, mainly in the North Bay

- Hazardous beach conditions this weekend

SHORT TERM

Issued at 1010 PM PDT Wed Sep 2 2026 (Tonight through Friday)

The marine layer is gone. A cold front is currently located about 200 miles west of San Francisco and is supported in the upper levels by a 500 mb trough and a meridional jet stream. We saw some pre- frontal rain in the North Bay on Wednesday. Santa Rosa received 0.08" and Mt. Tam recorded 0.64". That was just the warm-up. The main event will occur Thursday morning as the front moves through. Models have been trending wetter, and we're now expected around 1/4" in Santa Rosa through the morning and up to 1" in the mountains. That's not enough to cause any major issues, but it is real rain, especially for this time of year. The normal rainfall for the entire moth of September is 0.15" at Santa Rosa. Expect slick roadways in the North Bay Thursday morning.

As the front continues to march south, the associated rain should cross the Golden Gate by midday, but it will be losing upper level support and start to rapidly weaken. While a good portion of the Bay Area should see some rain, it likely won't be more than a few hundredths outside of the coastal mountains. The Central Coast will be even drier, and will have to wait until Thursday evening to see if any rain will fall.

In addition to rain, this front will bring NW winds with gusts up to 25 mph for most. Stronger gusts of 30-40mph are expected through favored gaps/passes, and in the Salinas Valley. We'll obviously have more cloud cover Thursday as well, keeping the temperatures cool and comfortable.

After the front passes, skies will clear from North to South through Thursday evening. As the skies clear, radiational cooling overnight will help the marine layer will start to reform. While there is still some uncertainty with the timing, marine layer stratus will likely return to the North Bay by Friday morning, but may take until Saturday or even Sunday to reach the Central Coast.

LONG TERM

Issued at 1010 PM PDT Wed Sep 2 2026 (Friday night through next Wednesday)

Speaking of this weekend, a Beach Hazards Statement is in effect from Friday through Monday as southerly swell from multiple distant hurricanes reaches the coast. Days when it's nice outside but the ocean is energetic are typically the most deadly. On top of that it's a holiday weekend. Please refer to the Beaches section below for more details.

Behind the front the temperature outside of the newly forming marine layer will start to warm up through the weekend. At 500 mb the trough over the coast will become a pseudo cut-off low. While it detaches from the 500 mb flow, a healthy jet finger will continue to provide some upper level divergence through the weekend. Nevertheless the low pressure will gradually fill. Meanwhile high pressure over the Southwest will start to influence the weather, allowing temperatures to rebound back to normal by Monday.

As Hurricane Marie now looks like it will take a more westerly track out to sea, the residual moisture impacts are much less likely to reach any further north than Southern California this weekend. Models are also showing a slug of dry air Sunday over the Central Coast that blocks the less dense tropical air mass from moving north. The deterministic ECMWF shows 1.8" of PW at Los Angeles Sunday afternoon, while Monterey has 0.5". That would give Southern California a decent amount of rain, but nothing for the Bay Area. It's a similar story with instability. Not a single member of the ECMWF ensemble has MUCAPE over 50 J/kg north of Pt. Conception. There is always the chance that the tropical moisture rides over this dry air mass, opening the door for dry thunderstorms. There's no direct support for that in the model guidance at the moment, but pattern recognition suggests it's worth keeping an eye on.

While this weekend now looks like it will probably be dry, there is a hint in the guidance that the remnants of Marie will eventually get caught up in the persistent SW flow if the cut-off low can survive long enough. If that happens, we may see some associated moisture by the middle of next week.

AVIATION

(06Z TAFS) Issued at 957 PM PDT Wed Sep 2 2026

Minimal changes to the TAF package this evening. The near term changes covered stratus that has started to form along the coast and in some of the valleys. Outside of that, we await the arrival of a cold front. The highest chances for rain will be for the North Bay terminals with chances decreasing around the San Francisco Bay. Heavier pockets of rain may bring reduced visibility at times, but most sites will see at least MVFR to potentially IFR cigs with the passage of the front. VFR cigs may return as early as the late morning areas for some terminals, for North Bay terminals. Clearing skies will gradually follow for terminals south of there, with a slot for clear skies. Models hint at stratus trying to reform late Thursday night into Friday morning but confidence was too low to add to most terminals.

Vicinity of SFO...Stratus formed off the west side of the San Francisco Peninsula and around KOAK this evening; however, KSFO has been lucky with only high clouds being reported. Confidence remains low with the stratus forecast here, so opted to remain optimistic during the overnight hours. Though lower clouds are expected with the passage of the front. We'll be watching the frontal passage, which should reach the San Francisco area Thursday morning. The best chances for rain look to be between 14-20Z with perhaps some vicinity showers or MVFR type cigs lingering into the mid afternoon. Winds will be from the south early on and getting to about 15kt by the late morning or early afternoon. Flow becomes west/northwest once the front passes, with sustained 15kt winds through roughly sunset. Cigs should gradually improve with the frontal passage as well.

SFO Bridge Approach...Similar to SFO.

Monterey Bay Terminals...The HRRR seems to be doing alright this morning, capturing the blip of stratus hugging the northern portion of the Monterey Bay and slinking into the northern Salinas Valley. Models show stratus flirting around KSNS for the next couple of hours, with stratus returning after midnight but clearing shortly after sunrise. Brought cigs up a bit to MVFR levels rather than keeping them at IFR given last nights observations, but the marine layer and stratus have humbled us before. Nonetheless, it should be short lived as it retreats to the coast during Thursday morning and a front slowly meanders southward. VFR cigs are expected by 13-15Z Thu, with high clouds returning to the forecast for the afternoon. Around or shortly after 0Z Fri, stratus looks to make are return to KSNS and KMRY.

MARINE

(Tonight through next Tuesday) Issued at 850 PM PDT Wed Sep 2 2026

A weak cold front will move through the region late tonight and into Thursday morning. Winds will continue to shift ahead of its arrival with gentle to moderate southwest breezes expected. Rain chances are best north of Pigeon Point during the morning and early afternoon hours, with isolated showers possible down to Point Pinos during the afternoon. Northwest winds return behind the front and will be gentle to moderate. Diurnal winds increase more Friday and Saturday afternoon, especially in vicinity of Monterey Bay. The tropical activity well to our south will produce long period southerly swell beginning Friday and continuing through the weekend into the beginning of next week.

BEACHES

Issued at 1010 PM PDT Wed Sep 2 2026

A Beach Hazards Statement is in effect Friday-Monday as the swell from both Hurricane Marie and Hurricane Karina reaches the coast. As these hurricane whip up the ocean, the waves travel over 1,000 miles in all directions, gradually flattening out to low amplitude, but long period swell. These waves aren't very intimidating if you're on a boat in the open ocean, but the long period allows them to push much farther up the beach. Long period swell always increases the chance for sneaker waves, but that's particularly true this weekend since there are 2 different sets of southerly swell, and their energy will periodically combine. In addition to sneaker waves, expect strong rip currents and breaking waves up to 10 ft. As this is a holiday weekend and the weather is otherwise pretty nice, the exposure to the risk is high. Avoid the water if you're not an expert swimmer. If caught in a rip current, swim parallel to shore until you stop feeling the pull. Even on the beach, be prepared for sneaker waves this weekend and never turn your back on the ocean.

MTR WATCHES/WARNINGS/ADVISORIES

CA...Beach Hazards Statement from Friday morning through Monday evening for CAZ006-505-509-529-530.

PZ...None.