, Issued at 1159 AM PDT Wed Sep 2 2026 (This afternoon through Thursday)
KMUX shows a band of light precipitation bisecting the Bay Area and moving east. Still waiting on a bucket tip south of the Golden Gate Bridge; nonetheless, it won't amount to much as the band continues to weaken. This pre-frontal rain has overperformed the official forecast with Mt. Tam measuring 0.57" in the last 24 hours. The overperformance is likely due to the struggles of guidance/models in the shoulder seasons. The cold frontal passage will occur tomorrow afternoon/evening from northwest to southeast, bringing renewed chances for rainfall alongside well below normal temperatures and cloudy conditions. This second round of rain also runs the risk of overperformance; however, the forecast has trended wetter. Totals of 0.10"-0.50" for most of the North Bay and 0-0.10" south of the Golden Gate Bridge are expected with accumulation south of the Golden Gate Bridge primarily favoring the San Francisco Peninsula Coast. Looking at the 90th percentile, totals get bumped up with up to 1.00" possible in the higher terrain of the North Bay and up to 0.50" along the San Francisco Peninsula Coast. While rainfall is expected to be beneficial, wet roadways will create slick driving conditions and increase stopping distance. Wind Advisory criteria is not expected to be met; however, gusts of 30-40 mph can be expected through gaps/passes and down the Salinas Valley.
..issued at 1159 AM PDT Wed Sep 2 2026 (Friday through next Tuesday)
A cutoff low will spawn in the Pacific Northwest from remnant upper- level troughing as ridging expands westward into the Desert Southwest. The low is expected to fill through the weekend, giving the ridge increasing influence over the forecast. As such, a gradual warming and drying trend and the reformation of the marine layer is expected over the weekend. These features will also be enough to shunt moisture from Tropical Storm Marie south of the California Bight, at least for now. Even with a cutoff low in play, there is relatively good agreement in the forecast through Monday. By Tuesday, the ECMWF and GFS begin to drastically diverge on their solutions with Marie. The one to watch will be the ECMWF as it has another cutoff low digging, absorbing, and bringing what was Marie into Central California, which would be a low probability outlier at the moment. It's imperative to note that if it reaches California: Marie will no longer be tropical and the primary impact will be rainfall.
(00z TAFS) Issued at 603 PM PDT Wed Sep 2 2026
The main forecast concern will be the passage of the cold front late tonight into Thursday morning. Hi-res guidance has the front arriving in the North Bay around 6-8Z and the gradually moving south. 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 cigs with the passage of the front. VFR cigs may return as early as the late morning areas for some terminals, with better chances for lifting or clearing clouds by the afternoon.
Vicinity of SFO, 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 main challenge for the Monterey Bay region will be stratus and perhaps a rogue shower or some virga if the front holds up. Models show stratus trying to make a return 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.
(tonight through next Tuesday) Issued at 603 PM PDT Wed Sep 2 2026
Northwesterly breezes will be light to moderate through the remainder of the week and into the weekend with moderate wind driven seas. Diurnal winds will 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.
Ca, None. PZ, None.
