, 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.
..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.
(12z TAFS) Issued at 438 AM PDT Thu Sep 3 2026
A weak cold front is on track to move through the Bay Area this morning. This cold front will bring scattered showers in the North Bay (higher confidence) and potentially into the rest of the Bay Area (lower confidence). Stratus coverage is patchy this morning with the incoming cold front keeping the marine layer mixed out. After cold frontal passage, the marine layer looks to return tonight (around 2000 ft) and will see MVFR CIGs along the coast. Confidence is slightly lower as to the timing of stratus return for interior sites with guidance indicating a later return between 09-12Z likely. Winds initially start more southwesterly this morning before shifting northwesterly again after cold frontal passage. Breezy to gusty winds are possible as the front moves through with winds to diminish after frontal passage.
Vicinity of SFO, Shower chances increase by late this morning and continue through the early evening. The cold front is expected to pass through SFO this afternoon/early this evening with the highest potential for showers during this time. Breezy southwesterly winds become more northwesterly by this evening after cold frontal passage. Guidance is mixed as to if stratus will return to SFO tonight as the marine layer redevelops. For the 12Z TAFs opted to keep VFR conditions at SFO tonight (similar to the HRRR) but this may need to be updated.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, Patchy MVFR-IFR CIGs have been developing over the Monterey Peninsula with ceilings coming in and out at both MRY and SNS. Moderate confidence that ceilings will continue to fluctuate at SNS through mid morning while confidence is low to moderate that a ceiling will, at least temporarily, return to MRY this morning. VFR conditions expected this afternoon with breezy SW to W winds expected. The cold front will largely have fallen apart by the time it reaches MRY/SNS but there is still a low potential for drizzle to impact both sites late this evening.
(today through Tuesday) Issued at 438 AM PDT Thu Sep 3 2026
Rain chances increase over the northern waters this morning as a weak cold front moves through the region. Southwesterly winds gradually shift northwesterly by this afternoon after cold frontal passage. Winds generally stay gentle to moderate but diurnal fresh to strong gusts return within the Monterey Bay and along the Big Sur Coast Friday into the weekend. More widespread fresh to strong gusts return by early next week across the coastal waters. Long period southerly swell associated with tropical activity well to our south will reach the coastal waters Friday and continue into early next week.
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.
Ca, Beach Hazards Statement from Friday morning through Monday evening for CAZ006-505-509-529-530.
PZ, None.
