, Issued at 1218 AM PDT Mon Oct 19 2026 (Today and tonight)
As the upper-level trough nears the West coast, it pushes southward until it finally settles a few hundred miles west-southwest of San Francisco by Tuesday. In the meantime, as the trough center approaches our immediate coastline, the marine layer deepens to around 2000 feet overnight accompanied with a gentle to moderate onshore flow up to 10-20 mph through Monday afternoon. Another drastic drop in temperatures due to enhanced cold air advection occurs on Monday with widespread maximum temperatures in the mid 50s to low 70s. The far interior Central Coast will remain in the 70s however. By Monday evening, winds gradually ease and become variable through Tuesday.
The upper-level trough becomes fully cut-off from the main jet stream by Tuesday. As a result, a cooler and more humid air mass gets ushered into the Central Coast and Bay Area. Ensemble Euro and GFS members continue to forecast precipitable water (PWAT) values around 0.80-0.85 inches by Tuesday evening, exceeding the 75th percentile for this time of year. To put into perspective, the most recent 00Z OAK sounding measured PWAT at 0.56 inches which falls within the seasonal norm. An increased moisture content supports the initiation of light rain (mainly offshore) while suppressing the redevelopment of the marine layer.
..issued at 1218 AM PDT Mon Oct 19 2026 (Tuesday through Sunday)
Light rain showers migrate onshore Tuesday evening impacting the Central Coast first and gradually making their way through the rest of the Bay Area. As a result, the marine layer is not expected to redevelop in the next few days. The rain-producing system propagates eastward toward land on Wednesday, thereby allowing for widespread showers to persist through Thursday. The North Bay will likely see lower rainfall totals compared to the rest of the Bay Area. Given its proximity to the center of the cut-off 500 mb low, the Central Coast will likely experience the highest rainfall amounts as well as the greatest potential for thunderstorm development (<20%), particularly along the Santa Lucia Range and Sierra de Salinas. Ensemble Euro and GFS members forecast PWAT values to rise above the 90th percentile on Wednesday. According to deterministic European model, most unstable CAPE continues to trend upwards generally around 100-300 J/kg with a few spots exceeding 500-800 J/kg. The moisture and instability is available to support thunderstorm development. The alignment of these elements with orographic lift will be sufficient to result in some "wet" thunderstorms, which is why the greatest potential resides over the Central Coast higher terrain. While the winds are expected to remain light and variable through the event, any thunderstorm development can result in gusty and erratic winds. This event will be the first test to the Timber and Plaskett fire burn scars as the soil in these areas cannot absorb much moisture. If rainfall rates exceed their thresholds, the water will slip right off the surface resulting in burn scar debris flows, which may lead to flash flooding. If your home is downslope of these burn scars, now is the time to prepare for the possibility of an emergency.
By Thursday night, the cut-off low is well to our East with rainfall chances rapidly diminishing. The usual diurnal onshore wind pattern returns briefly on Friday with a persistent troughing pattern through the remainder of the forecast period, resulting in near to slightly below seasonal temperatures.
(12z TAFS) Issued at 507 AM PDT Mon Oct 19 2026
The marine layer is here, blanketing much of the region with stratus and MVFR ceilings. Expect the stratus to slowly trim back this morning, with coastal communities seeing clouds cling into the early afternoon. After that, VFR conditions should prevail for much of the region. Models try to hint some MVFR cigs trying to sneak back in tonight, but with a 20-40% probability opted to not lock in any BKN or OVC cigs.
Vicinity of SFO, Stratus engulfs the SF Bay this morning, with MVFR cigs being reported at SFO and surrounding stations. These conditions should hold through mid morning, with clearing expected by late morning or early afternoon. After that look for onshore to pick up in the afternoon and linger through the early evening hours with gusts up to 20-24kt. The marine layer is expected to mix out completely today, which should make the return of stratus difficult tonight. Opted to keep the hint of some lower cigs tonight, but confidence is low in any stratus development around the region.
SFO Bridge Approach, Similar to SFO.
Monterey Bay Terminals, The stratus has been most interesting around the Monterey Bay this morning as it has played peek-a-boo with the terminals for a few hours. But alas, it appears to have finally filled in leaving us with MVFR cigs. These should clear by late morning or early afternoon if it remains pesky. Then, we should have VFR conditions through the early evening. Both the HREF and HRRR hint at stratus trying to make an appearance before clearing by early Tuesday morning. Medium confidence in the forecast.
(today through Saturday) Issued at 507 AM PDT Mon Oct 19 2026
Moderate to fresh northwesterly breezes will prevail today, with hazardous conditions for small craft lingering at the inner coastal waters south of Point Pinos through this afternoon. Winds will diminish and back to a gentle southerly breeze Tuesday and Wednesday before returning to moderate to fresh northerly breezes Thursday. Rough seas across the outer waters will subside to become moderate but will rebuild briefly to become rough Tuesday. Light rain showers are expected Tuesday through Thursday.
Ca, None. PZ, Small Craft Advisory from 3 PM this afternoon to 9 PM PDT this evening for Mry Bay.
Small Craft Advisory until 3 PM PDT this afternoon for Pt Pinos to Pt Piedras Blancas 0-10 nm.
